Glass Science & Technology Research @ UPM

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A compilation of research papers on glass materials. Research activities were conducted at Universiti Putra Malaysia, Serdang, Selangor, Malaysia.

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Glass Science & Technology Research @ UPM

  1. 1. Glass Science & Technology 2012/2013
  2. 2. Hindawi Publishing Corporation Advances in Condensed Matter Physics Volume 2013, Article ID 783207, 6 pages http://dx.doi.org/10.1155/2013/783207 Research Article Effect of ZnO on the Thermal Properties of Tellurite Glass H. A. A. Sidek, S. Rosmawati, B. Z. Azmi, and A. H. Shaari Glass Ceramic and Composite Research Group, Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia Correspondence should be addressed to H. A. A. Sidek; sidek@upm.my Received 16 August 2012; Accepted 29 January 2013 Academic Editor: Nigel Wilding Copyright © 2013 H. A. A. Sidek et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Systematic series of binary zinc tellurite glasses in the form (ZnO) 𝑥 (TeO2 )1−𝑥 (where 𝑥 = 0 to 0.4 with an interval of 0.05 mole fraction) have been successfully prepared via conventional melt cast-quenching technique. Their density was determined by Archimedes method with acetone as buoyant liquid. The thermal expansion coefficient of each zinc tellurite glasses was measured using L75D1250 dilatometer, while their glass transition temperature (𝑇 𝑔 ) was determined by the SETARAM Labsys DTA/6 differential thermogravimetric analysis at a heating rate of 20 K min−1 . The acoustic Debye temperature and the softening temperature (𝑇 𝑠 ) were estimated based on the longitudinal (𝑉 𝐿 ) and shear ultrasonic (𝑉𝑠 ) wave velocities propagated in each glass sample. For ultrasonic velocity measurement of the glass sample, MATEC MBS 8000 Ultrasonic Data Acquisition System was used. All measurements were taken at 10 MHz frequency and at room temperature. All the thermal properties of such binary tellurite glasses were measured as a function of ZnO composition. The composition dependence was discussed in terms of ZnO modifiers that were expected to change the thermal properties of tellurite glasses. Experimental results show their density, and the thermal expansion coefficient increases as more ZnO content is added to the tellurite glass network, while their glass transition, Debye temperature, and the softening temperature decrease due to a change in the coordination number (CN) of the network forming atoms and the destruction of the network structure brought about by the formation of some nonbridging oxygen (NBO) atoms. 1. Introduction Tellurite glasses are at present the subject of intensive investigations because the glassy phase can be formed over a wide range of concentrations. The application of these types of glasses in areas of optoelectronics such as laser technology and fiber optics and other fields is immense due to their good physical properties, high density, chemical stability, high homogeneity, and relatively high electrical conductivity [1–4]. Even tellurite glasses and glass ceramics are promising choices due to their high refractive index (larger than 2), wideband infrared transmittance (extending up to 6 micrometer), and large third-order nonlinear optical susceptibility. In addition, tellurite glasses combine the attributes of a short wavelength UV edge (about 350 nm), good glass stability, rare earth ion solubility, a slow corrosion rate, and relatively low phonon energy (600–850 cm−1 ) among oxide glass formers [5]. Furthermore, their low transformation temperatures and absence of hygroscopic properties limits the application of phosphate and borate glasses. Based on the information, the use of tellurite glasses may be more advantageous than silicate glasses [6, 7]. Another basic system that has good glass-forming ability and used by many researchers is the ZnO-TeO2 system. Tellurium (IV) oxide in combination with ZnO forms stables glasses [7]. Zinc tellurite glasses are reported to be a suitable host for optically active rare earth ions because of the wide glass-formation range which is close to the extremum for binary tellurite glasses [8]. ZnO-TeO2 system was used as a basis for multicomponent optical glass synthesis and has been reported as a useful medium for ultralow loss (1 dB 1000 m−1 ) optical fibers for wavelengths in the 3.5–4 𝜇m region [9]. It seems clear from the coverage above that tellurite glasses are strategically important solid materials. The above indicate undoubtedly the existence of a practical interest in the zinc-tellurium-containing systems as a choice of compositions for super heavy optical flint glasses. Previous studies showed that the glass formation occurs in the zinc tellurite system in the region of the eutectic (21 mol%
  3. 3. 2 Advances in Condensed Matter Physics Table 1: The density, transition temperature, thermal expansion, acoustic Debye temperature, and softening temperature of zinc tellurite glasses. ZT0 ZT1 ZT2 ZT3 ZT4 ZT5 ZT6 ZT7 ZnO-TeO2 (mol%) Density (g/cm3 ) (± 0.01) 0–100 10–90 15–85 20–80 25–75 30–70 35–65 40–60 Thermal expansion coefficient (× 10−6 K−1 ) (± 0.01) 4.80 5.09 5.10 5.14 5.19 5.21 5.28 5.29 ZnO) on the TeO2 -rich side of the phase diagram [10]. These types of glasses are characterized by a high refractive index which increases with TeO2 content [11–13]. Apart from their applications, there is a lack of data on structural investigations as well as the thermal properties of these ZnO-TeO2 glass systems in the literature. Therefore, the aim of this research is to study the effect of zinc on the thermal properties of tellurite glass system in order to understand the fundamental origin of such properties. Temperature (K) Transition Debye Softening 658 654 653 646 647 638 637 633 12.40 12.14 12.36 12.51 12.66 12.90 12.54 12.78 263 259 259 257 257 252 253 251 857 852 833 802 783 736 722 694 Intensity (a.u.) Glass sample ZT7 ZT6 ZT5 ZT4 ZT3 ZT2 ZT1 ZT0 2. Experimental and Materials Systematic series of binary zinc tellurite glasses in the form (ZnO) 𝑥 (TeO2 )1−𝑥 (where 𝑥 = 0 to 0.4 with internal of 0.05 mole fraction) have been successfully prepared via melt quenching technique. The density of the glasses was determined by Archimedes method with acetone as buoyant liquid. The preparation of the tellurite-based glass systems and related experimental method has been discussed elsewhere [14–16]. To check the amorphous state, the X-ray diffraction was carried out for each glass sample by using a computercontrolled X’pert Pro Panalytical set. Both longitudinal and shear ultrasonic velocities were measured in different compositions of the glass system by using the MBS8000 Ultrasonic Data Acquisition System at 10 MHz frequency and at room temperature. The thermal expansion coefficient was measured using L75D1250 dilatometer with the rectangular parallelepiped 3 × 3 × 6 mm3 of each glass samples. The thermal expansion was obtained over a range of 30∘ to 210∘ C, while the glass transition temperature (𝑇 𝑔 ) was determined by the differential thermogravimetric analysis (Setaram instrumentation Labsys DTA/6) at heating rate of 20 K min−1 . The accuracy in the measurement of 𝑇 𝑔 is ±2∘ C. 3. Results and Discussion Table 1 presents the density, transition temperature, thermal expansion, acoustic Debye temperature, and softening temperature of (ZnO) 𝑥 (TeO2 )1−𝑥 zinc tellurite glasses. 10 20 30 2𝜃 40 50 Figure 1: The XRD patterns of zinc tellurite and pure tellurite glass. 3.1. XRD Analysis. The XRD patterns of the present glass samples depicted in Figure 1 were found to show no discrete or continuous sharp peaks but broad halo at around 26∘ – 30∘ , which reflected the characteristic of amorphous glass structure. This indicates the absence of long-range atomic arrangement and the periodicity of the three-dimensional network in the glassy materials. 3.2. Density. The density of a glass is an important property capable of evaluating the compactness. The density is affected by the structural softening/compactness, change in coordination number, and dimension of interstitial spaces of the glass. The increase in the density (as depicted in Table 1) can be related to two reasons: The first reason is the replacement of TeO2 by ZnO which has high relative molecular weight where the molecular weight of TeO2 and ZnO is 159.6 and 81.38, respectively. The second reason may be due to the transformation of TeO3 to TeO4 where the formation of TeO3+1 polyhedron has one nonbridging oxygen atom. This increase can be attributed to the zinc ions that occupy the interstitial position, and therefore the threedimensional structure of tellurite glass is not destroyed. These behaviors of the studied glasses are agreed with reported data elsewhere [4, 7].
  4. 4. Advances in Condensed Matter Physics 3 𝛼𝐿 = Δ𝐿 , 𝐿𝑥Δ𝑇 (1) where 𝐿 is the original length of the sample, Δ𝐿 is the increase in length, and Δ𝑇 is the increase in temperature. Since glasses are usually isotropic materials with relatively small thermal expansion coefficients, 𝛼V = 3𝛼 𝐿 can be used to approximate 𝛼V with very little error in calculation. All reported thermal expansion coefficients for glasses are actually average linear thermal expansion coefficients over some specified temperature ranges. The particular temperature ranges from 0 to 300∘ C, 20 to 300∘ C, or 25 to 300∘ C. The data for experimental studies may be reported for almost any temperature range. Since most linear thermal expansion coefficients lie between 1 and 50 × 10−6 K−1 , metallurgists, ceramists, and other material scientists usually report values with units of ppm K−1 . Traditionally, however, glass technologists used 10−7 K−1 as the basis for reporting thermal expansion coefficients. An understanding of how the thermal expansion coefficient varies as a function of the glass composition is needed. The linear 𝛼th of any solid material depends strongly on the anharmonic nature of interatomic forces. Figure 2 shows the plot of thermal expansion coefficient versus chemical composition of binary zinc tellurite glasses at various temperatures and summarized in Table 1. The thermal expansion coefficient indicates the relation between the volume of a glass and its temperature. This property is a strong function of glass composition. In the range between room temperature and 𝑇 𝑔 , the expansion coefficient of the glass was often assumed to be independent of temperature and was defined as 𝛼 = (Δ𝐿/𝐿 0 )Δ𝑇. From Figure 2 it can be seen that the thermal expansion coefficient increases as the ZnO content added from 0.10 mole fraction to 0.40 mole fraction. The substitution of ZnO might be due to the change of the coordination number of TeO2 from 4 to 3. This change is associated with the creation of non-bridging oxygens (NBOs) that caused the decrease in rigidity. Further substitution of ZnO, that is, 0.35 mole fraction, decreases the thermal expansion coefficient which can be supported by the earlier work [18]. Further increasing the modifier content stabilizes TeO4 units with NBO. The decrease of thermal expansion 14 14 𝑦 = 0.0001𝑥 2 + 0.0078𝑥 + 12.278 𝑅2 = 0.5521 10 12 11 8 10 2 𝑦 = −0.0003𝑥 + 0.0221𝑥 + 4.8296 6 𝑅2 = 0.9541 4 2 9 8 Thermal expansion (×10−6 K−1 ) 13 12 Density (g cm−3 ) 3.3. Thermal Expansion. Thermal expansion is one of the very important properties of materials for many technological and practical applications. The aim of the present work is to characterize glass thermal expansion coefficient, and their transition temperatures. There is a strong dependence between the glass transition temperature, 𝑇 𝑔 , thermal expansion coefficient and the kind of the modifier [17]. The thermal expansion coefficient of a material is a measure of the rate of change in volume and therefore density with temperature. Although the thermal expansion coefficient is actually defined in terms of the volume of the substance, this value is somewhat difficult to measure. As a result, the expansion coefficient for glasses is usually only determined in one direction; that is, the measured value is the linear thermal expansion coefficient, 𝛼 𝐿 : 7 0 10 20 30 ZnO content (mol%) 6 40 Figure 2: The density and linear expansion coefficient of TeO2 -ZnO glasses. coefficient increased the tightness of the structure. Above 0.35 mole fraction, the conversion of TeO4 to TeO3 occurs again which causes the decrease in rigidity. 3.4. Thermal Stability. Thermal stability is defined as the resistance to permanent change in properties caused solely by heat. Glass stability is defined in terms of resistance to crystallization of a glass during heating. Glass stability is most important during processes involving re-forming of an existing glass. The glass forming ability automatically leads to glass stability [19]. Thermal stability is frequently characterized by the difference in temperature between the onset of the glass transformation range (𝑇 𝑔 ) and the occurrence of crystallization (𝑇 𝑥 ) for a sample heated at a specified linear rate. These measurements are routinely carried out using a differential scanning calorimeter (DSC) or differential thermal analyzer (DTA). The exact definitions of 𝑇 𝑔 and 𝑇 𝑥 are subjected to the preference of the experimenter, as is the choice of the appropriate heating rate used in the study. Typical thermal spectra may contain one or more exothermic peaks due to crystallization of different phases, but the lowest temperature peak is considered in discussing glass stability. Once a significant number of crystals are formed, subsequent events at higher temperatures are not considered important in glass stability. It is known that the glass transition temperature (𝑇 𝑔 ) is affected by the alteration of the glass structure, and the structure of the thermally stable glasses is close-packed structure. The glass transition temperature 𝑇 𝑔 helps to reveal the close or loosely packed structure of the glass [20], where the higher single-bond energy in glass network, the more stable the glass-forming system. 3.5. Glass Transition Temperature. Glass transition temperature, 𝑇 𝑔 , plays a vital role in understanding the physical properties of glass [21]. DTA curves for the studied glass
  5. 5. 4 Advances in Condensed Matter Physics 900 900 700 Debye temperature (K) 800 𝑦 = −0.0758𝑥2 − 1.4117𝑥 + 863.81 700 𝑅2 = 0.9787 2 600 600 𝑦 = −0.0068𝑥 − 0.3747𝑥 + 658.59 𝑅2 = 0.9614 500 400 500 400 𝑦 = −0.0003𝑥2 − 0.2841𝑥 + 262.79 300 300 𝑅2 = 0.9348 200 200 100 Transition/softening temperature (K) 800 of the glass is associated with an increase in the lattice vibrations. The observed acoustic Debye temperature, obtained from the ultrasonic velocity data, [13, 24, 25] is 100 0 10 30 20 ZnO content (mol%) 40 Figure 3: The acoustic Debye, transition and softening temperatures of ZnO-TeO2 glasses. samples with different ZnO contents have been obtained to determine the glass transition temperature (𝑇 𝑔 ) values. Generally, glasses with close-packed structure will have thermal stability, while those with loose-packed structure will have unstability [17]. In the present investigation, all of the glasses have an endothermic change between 385.21 and 360.52∘ C, which attributes to the glass transition temperature, 𝑇 𝑔 . The Zn2+ is incorporated into the glass structure as a network modifier, resulting in loose packing of the glass structure. As a result, a continuous decrease in 𝑇 𝑔 with the increase in network modifier content has been observed (Figure 3). In the present glasses, the decrease in 𝑇 𝑔 values with increase in Zn2+ content contributes to a decrease in thermal stability of the glasses leading to loose-packed structure as discussed elsewhere [21]. The glass transition reflects a change in the coordination number of the network forming atoms and destruction of the network structure brought about by the formation of some non-bridging atoms [22]. The decrease in the glass transition temperature values implies that the number of bridging oxygen groups decreases. This is mainly due to the addition of ZnO which weakens the bond between each atom sample (increases the number of NBOs atom). The bond is easier to break and hence the 𝑇 𝑔 of the sample decreased. Furthermore, it also implies a decrease in rigidity of the glass network. 3.6. Acoustic Debye Temperature. Acoustic Debye temperature (𝜃 𝐷) is a characteristic property of a solid lattice related to its acoustic phonon spectrum [23] where it represents the temperature at which nearly all modes of vibration in a solid are excited [24]. Debye temperature is a characteristic temperature of glass; any modifier added to the host network affects this temperature [25]. Also the increase in the rigidity 9𝑍𝑁 𝐴 1/3 ℎ ) , Θ 𝐷 = ( ) 𝑀 𝑆( 𝑘 4𝜋𝑉 𝑚 (2) where 𝑀 𝑆 , the mean velocity, is given by 𝑀 𝑆 = [( 1 2 ) + ( 3 )] 𝑉 𝐿3 𝑉𝑠 −1/3 (3) ℎ the Planck’s constant, 𝑘 the Boltzmann’s constant, 𝑁 𝐴 the Avogadro’s number, and 𝑍 the number of atoms given by 𝑍 = ∑ 𝑥 𝑖 𝐿 𝑖, (4) where 𝑥 and 𝐿 are the mole fraction and number of atoms in the 𝑖th oxide. Regarding the compositional dependence of the Debye temperature, it can be seen that Debye temperature decreases from 263 K to 251 K as ZnO content increases (Figure 3). It decreases when the ultrasonic velocity decreases. The observed decrease in 𝜃 𝐷 indicates a monotonic decrease in the total vibrational energy of the system. This is because any of the conceivable vibrational units resulting from the substitution will be of lower energy. Also, the observed decrease in Debye temperature is mainly attributed to change in the number of atoms per unit volume and also the existence of non-bridging oxygen. It also indicates the loosing packing structure of the glasses with creation of NBOs as discussed above. In general the acoustic Debye temperature of the present glasses is particularly sensitive with the addition of ZnO content. 3.7. Softening Temperature. Softening temperature (𝑇 𝑠 ) is another important parameter defined as the temperature point at which viscous flow changes to plastic flow. In actual practice, it plays a crucial role in determining the temperature stability of the glass. Softening temperature (𝑇 𝑠 ) is related to the ultrasonic velocity of shear waves (𝑉𝑠 ) by the equation 𝑇𝑠 = 𝑉𝑠 2 𝑀 , 𝐶2 𝑍 (5) where 𝑀 is the effective molecular weight, 𝑍 is the number of atoms in the chemical formula, and 𝐶 is the constant of proportionality and has the value 507.4 (ms−1 K1/2 ) for alumina-silicate glasses and is assumed to be the same for the glasses under investigation. The higher the value of softening temperature of a glass, the greater the stability of its elastic properties [24, 25]. Values of softening temperature for ZnO-TeO2 glasses were calculated and presented in Table 1. Figure 3 shows that on addition of ZnO to TeO2 , the softening temperature decreases from 857 K to 694 K with increasing ZnO content. This shows that the stability of the glasses decreases as the network modifier content increases. This change is what may be expected from the decrease of elastic moduli.
  6. 6. Advances in Condensed Matter Physics 5 Table 2: Nonlinear regression analysis of the variables ( ̂ = 𝛿̂ 2 + 𝛽̂ + 𝛼) for various properties of ZnO–TeO2 glass. 𝑌 𝑥 𝑥 Variables ( ̂ 𝑌) Density Thermal expansion coefficient Transition temperature Acoustic Debye temperature Softening temperature 𝛿 −0.0003 0.0001 −0.0068 −0.0006 −0.1037 𝛽 0.033 0.008 −0.375 −0.275 −0.609 3.8. Regression Analysis. All the current experimental data were analyzed using Microsoft Excel, by fitting regression curves, and the results of the regression coefficients are presented in Table 2. The regression coefficients obtained from each curves are shown in Figures 2 and 3. In Table 2, ̂ stands for the variables shown in the first column and ̂ is 𝑌 𝑥 the ZnO concentration. As can be seen in previous figures, for most of the variables a nonlinear polynomial ( ̂ = 𝛿̂ 2 + 𝑌 𝑥 𝛽̂ + 𝛼) gives the best fit. 𝑥 Except for the softening temperature, the overall results from Table 2 show that the addition of ZnO with less than 40 mol% into the tellurite glass system causes small effect (less than 10%) on their thermal properties. 4. Conclusion A number of experimental techniques have been employed to determine a number of important thermal properties of zinc tellurite glass system. The thermal properties of tellurite glasses such as the linear thermal expansion coefficient, the acoustic Debye temperature, glass transformation temperature, 𝑇 𝑔 , and softening temperature were studied with respect to ZnO content. The addition of ZnO content increases the densities of ZnO-TeO2 glasses due to a change in crosslink between TeO2 chains and coordination number of Te2+ ions. The addition of ZnO on TeO2 network also causes the decreasing values of the acoustic Debye, transition, and softening temperatures of ZnO-TeO2 glasses probably due to the change in Te2+ coordination number. The increase of ZnO in the tellurite glass system results in lower network rigidity, which in turns results in decrease of most of their thermal properties. Experimental data shows that the density and thermal properties are greatly a strong function of glasses composition. The changes in microstructure glassy network can have an effect on the physical as well as thermal characteristics of zinc tellurite glass. Acknowledgment The authors like to thanks the Universiti Putra Malaysia (UPM) who funded this research project under the Research University Grant Scheme (RUGS 2-2012) Project no. 05-0212-1838RU. References [1] A. I. Sabry and M. M. El-Samanoudy, “Optical, infrared and electrical conductivity of glasses in the TeO2 -B2 O3 system,” Journal of Materials Science, vol. 30, no. 15, pp. 3930–3935, 1995. 𝛼 4.830 12.278 385.59 262.76 861.08 𝑅2 0.954 0.552 0.961 0.910 0.978 % change 10 3.06 −6.41 −4.56 −19.02 [2] A. Berthereau, Y. le Luyer, R. Olazcuaga et al., “Nonlinear optical properties of some tellurium (IV) oxide glasses,” Materials Research Bulletin, vol. 29, no. 9, pp. 933–941, 1994. [3] A. Narazaki, K. Tanaka, K. Hirao, T. Hashimoto, H. Nasu, and K. Kamiya, “IR and XPS studies on the surface structure of poled ZnO-TeO2 glasses with second-order nonlinearity,” Journal of the American Ceramic Society, vol. 84, no. 1, pp. 214–217, 2001. [4] G. D. Khattak and M. A. Salim, “X-ray photoelectron spectroscopic studies of zinc-tellurite glasses,” Journal of Electron Spectroscopy and Related Phenomena, vol. 123, no. 1, pp. 47–55, 2002. [5] T. Sekiya, N. Mochida, and A. Ohtsuka, “Raman spectra of MO-TeO2 (M = Mg, Sr, Ba and Zn) glasses,” Journal of NonCrystalline Solids, vol. 168, no. 1-2, pp. 106–114, 1994. [6] T. Kosuge, Y. Benino, V. Dimitrov, R. Sato, and T. Komatsu, “Thermal stability and heat capacity changes at the glass transition in K2 O-WO3 -TeO2 glasses,” Journal of Non-Crystalline Solids, vol. 242, no. 2-3, pp. 154–164, 1998. [7] V. Kozhukharov, H. B¨ rger, S. Neov, and B. Sidzhimov, “Atomic u arrangement of a zinc-tellurite glass,” Polyhedron, vol. 5, no. 3, pp. 771–777, 1986. [8] D. L. Sidebottom, M. A. Hruschka, B. G. Potter, and R. K. Brow, “Structure and optical properties of rare earth-doped zinc oxyhalide tellurite glasses—practical implications of glass structure,” Journal of Non-Crystalline Solids, vol. 222, pp. 282– 289, 1997. [9] L. G. van Uitert and S. H. Wemple, “ZnCl2 glass: a potential ultra-low optical fiber material,” Applied Physics Letters, vol. 33, no. 57, 3 pages, 1978. [10] H. B¨ rger, K. Kneipp, H. Hobert, and W. Vogel, “Glass foru mation, properties and structure of glasses in the TeO2 -ZnO system,” Journal of Non-Crystalline Solids, vol. 151, no. 1-2, pp. 134–142, 1992. [11] R. El-Mallawany, M. Sidkey, A. Khafagy, and H. Afifi, “Elastic constants of semiconducting tellurite glasses,” Materials Chemistry and Physics, vol. 37, no. 3, pp. 295–298, 1994. [12] R. El-Mallawany, “Quantitative analysis of elastic moduli of tellurite glasses,” Journal of Materials Research, vol. 5, no. 10, pp. 2218–2222, 1990. [13] R. El−Mallawany, “Specific heat capacity of semiconducting glasses: binary vanadium tellurite,” Physica Status Solidi (a), vol. 177, no. 2, pp. 439–444, 2000. [14] Burger H, W. Vogel, and V. Kozhukharov, “IR transmission and properties of glasses in the TeO2 -Rn Om , Rn Xm , Rn (SO4 )m , Rn (PO3 )m and B2 O3 systems,” Infrared Physics, vol. 25, pp. 395– 409, 1985. [15] H. A. A. Sidek, S. P. Chow, Z. A. Talib, and S. A. Halim, “Formation and elastic behavior of lead-magnesium chlorophosphate glasses,” The Turkish Journal of Physics, vol. 28, no. 1, pp. 65–71, 2004.
  7. 7. 6 [16] H. A. A. Sidek, S. Rosmawati, Z. A. Talib, M. K. Halimah, and W. M. Daud, “Synthesis and optical properties of ZnO-TeO2 glass system,” The American Journal of Applied Sciences, vol. 6, no. 8, pp. 1489–1494, 2009. [17] R. El-Mallawany, “Tellurite glasses. Part 2. Anelastic, phase separation, debye temperature and thermal properties,” Materials Chemistry and Physics, vol. 60, no. 2, pp. 103–131, 1999. [18] U. Hoppe, E. Yousef, C. R¨ ssel, J. Neuefeind, and A. C. Hannon, u “Structure of zinc and niobium tellurite glasses by neutron and x-ray diffraction,” Journal of Physics Condensed Matter, vol. 16, no. 9, pp. 1645–1663, 2004. [19] J. E. Shelby, Introduction to Glass Science and Technology, The Royal Science of Chemistry, Cambridge, UK, 2nd edition, 2005. [20] H. Hirashima, H. Kurokawa, K. Mizobuchi, and T. Yoshida, “Electrical conductivity of vandium phosphate glasses containing ZnO or GeO2 ,” Glastechnische Berichte, vol. 61, no. 6, pp. 151–156, 1988. [21] A. B. Nishara and V. Rajendran, “Structure and elastic properties of TeO2 -BaF2 glasses,” Journal of Physics and Chemistry of Solids, vol. 67, no. 8, pp. 1697–1702, 2006. [22] H. Mori and H. Sakata, “Low-temperature electrical conduction of V2 O5 -Sb2 O3 -TeO2 glasses,” Journal of the Ceramic Society of Japan, vol. 102, no. 9, pp. 852–857, 1994. [23] A. H. Khafagy, A. A. El-Adawy, A. A. Higazy, S. El-Rabaie, and A. S. Eid, “The glass transition temperature and infrared absorption spectra of: (70−x)TeO2 + 15B2 O3 + 15P2 O5 + xLi2 O glasses,” Journal of Non-Crystalline Solids, vol. 354, no. 14, pp. 1460–1466, 2008. [24] M. A. Sidkey, A. Abd El-Moneim, and L. Abd El-Latif, “Ultrasonic studies on ternary TeO2 -V2 O5 -Sm2 O3 glasses,” Materials Chemistry and Physics, vol. 61, no. 2, pp. 103–109, 1999. [25] Y. B. Saddeek and L. Abd El-Latif, “Effect of TeO2 on the elastic moduli of sodium borate glasses,” Physica B, vol. 348, no. 1–4, pp. 475–484, 2004. Advances in Condensed Matter Physics
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  9. 9. Int. J. Mol. Sci. 2013, 14, 1022-1030; doi:10.3390/ijms14011022 OPEN ACCESS International Journal of Molecular Sciences ISSN 1422-0067 www.mdpi.com/journal/ijms Article The Effect of Remelting on the Physical Properties of Borotellurite Glass Doped with Manganese Syed Putra Hashim Syed Hashim, Haji Abdul Aziz Sidek *, Mohamed Kamari Halimah, Khamirul Amin Matori, Wan Mohamad Daud Wan Yusof and Mohd Hafiz Mohd Zaid Glass and Ultrasonics Studies Centre (GUSC), Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia; E-Mails: hyzzam2003@yahoo.com (S.P.H.S.H.); halimah@science.upm.edu.my (M.K.H.); khamirul@science.upm.edu.my (K.A.M.); wmdaud@science.upm.edu.my (W.M.D.W.Y.); mhmzaid@gmail.com (M.H.M.Z.) * Author to whom correspondence should be addressed; E-Mail: sidek@science.upm.edu.my; Tel.: +603-8946-6682; Fax: +603-8943-2508. Received: 7 October 2012; in revised form: 26 December 2012 / Accepted: 29 December 2012 / Published: 7 January 2013 Abstract: A systematic set of borotellurite glasses doped with manganese (1–x) [(B2O3)0.3(TeO2)0.7]-xMnO, with x = 0.1, 0.2, 0.3 and 0.4 mol%, were successfully synthesized by using a conventional melt and quench-casting technique. In this study, the remelting effect of the glass samples on their microstructure was investigated through density measurement and FT-IR spectra and evaluated by XRD techniques. Initial experimental results from XRD evaluation show that there are two distinct phases of glassy and crystallite microstructure due to the existence of peaks in the sample. The different physical behaviors of the studied glasses were closely related to the concentration of manganese in each phase. FTIR spectra revealed that the addition of manganese oxide contributes the transformation of TeO4 trigonal bipyramids with bridging oxygen (BO) to TeO3 trigonal pyramids with non-bridging oxygen (NBO). Keywords: borotellurite glass; density; bridging oxygen; FTIR spectra 1. Introduction Tellurite glass is an extremely promising material for laser and nonlinear applications in optics due to some of its essential characteristic features, such as high density, high refractive index, low phonon
  10. 10. Int. J. Mol. Sci. 2013, 14 1023 maxima, low melting temperature and excellent transparency in the far infrared region [1,2]. Furthermore, tellurite glass has a low melting point and is nonhygroscopic, which is an advantage when compared to borate and phosphate glasses. These types of glasses are extremely stable against devitrification, nontoxic and resistant to moisture for long periods of time [2]. It is widely recognized that the refractive index, n, and density, ρ, of many common glasses can be varied by changing the base glass composition [3]. In binary tellurite glasses, the basic structural unit of TeO4 is trigonal bipyramid (tbp) with a lone pair of electrons, and the structural units permit Te–O–Te bonding for glass formation [4]. The addition of tellurite to any other glass former or network modifier, such as B2O3, is of scientific and practical interest and may lead to the formation of interesting structural units that affect the physical properties of the glass network [5]. As reported earlier, the boron coordination number in the borate glass changed from three to four as more alkaline content was added into the system where the network linkage was increased. In contrast, the Te coordination number changed from four to three by the cleavage of the tellurite glassy matrix [6,7]. In fact, the presence of TeO2 in the matrix of alkali borate glasses decreases its hygroscopic nature; however, it improves the quality and enhances the IR transmission [8,9]. The role of alkali, alkaline earth, and transition metal oxides (TMO) in the borotellurite network is to modify the host structure through the conversion of the structural units of the borate system from [BO3] to [BO4] and the tellurite network from trigonal bipyramid [TeO4] to trigonal pyramid [TeO3] [10–13]. The elastic moduli of borotellurite glasses (TeO2–B2O3) have been reported and discussed based on the bond compression model [10,12]. In this work, borotellurite glasses doped with manganese oxide (MnO) in the form of (1–x) [(B2O3)0.3(TeO2)0.7]-xMnO, with x = 0.001, 0.002, 0.003 and 0.004, were prepared by using a conventional melt and quench-casting technique. The main objective of this work is to determine the optimum concentration of manganese needed to prepare the glass by examining amorphous characteristics using X-ray diffraction. The effect of remelting each glass sample is also studied. 2. Results and Discussion The XRD patterns for the various compositions of (1–x)[(B2O3)0.3(TeO2)0.7]-xMnO glasses are shown in Figure 1, and the existence of a peak for MnO concentrations of 0.1 mol% and 0.2 mol%, which is related to the existence of a crystalline phase in the samples, is shown in Figure 1a. The addition of the MnO has disturbed the borotellurite glass system. In general, crystal growth can occur at any temperature if a seed crystal is available. It may establish and enhance crystal growth inside a system where a detectable growth rate can occur at any temperature below the Tm. These crystalline peaks correspond to cubic manganese telluride borate, Mn3B7O12.65Te0.85, with the reference number 00-026-1255 [11–13]. At 0.3 mol% and 0.4 mol% MnO, the glass systems are in the amorphous state due to the optimum concentration of MnO, where it acts as a stabilizer for the glass system. Figure 1a also shows that no sharp peaks exist at 0.3 mol% and 0.4 mol% of MnO [10–15]. Manganese ions seem to exist in the Mn2+ and Mn3+ states in the glass network. However, at lower concentration of MnO, a majority of the manganese ions are in the Mn2+ state. The linkage of the Mn2+ and Te4+ ions is expected to be extremely weak because the difference in ionic radii of the Mn2+ (0.8 Å) and Te4+ (0.84 Å) is high when compared to that of Mn3+ (0.58 Å) and Te3+ (0.52 Å) ions [15].
  11. 11. Int. J. Mol. Sci. 2013, 14 1024 To study the remelting effect on the glass structure, all of the glass samples were then remelted. In general, the features of the XRD patterns confirm that all of the remelted glasses are in the amorphous state (Figure 1b), as indicated by the broad hump that occurs at approximately 2θ = 20°–30° for all of the remelted glass samples. All of the prepared glasses are free of bubbles, purple in color and of good quality. The density (ρ) and molar volume (Vm) of the glass samples are shown in Figure 2 and Table 1. The density of the pure borotellurite increased steadily with the addition of TeO2 into the glass structure, as depicted in Figure 2a. It can be observed that the density decreases gradually with the compositions for both glasses before and after remelt with an addition of MnO (see Figure 2b,c). Figure 1. The XRD pattern of (a) the original sample and (b) the remelted MnO–B2O3–TeO2 glass samples. 0.1%  0.1%  0.2%  0.2%  0.3%  0.3%  0.4%  (a) 0.4%  (b) The density results as depicted in Table 1 show that as the manganese cation concentration increases, the glass structure becomes more open, allowing for the likely creation of more nonbridging oxygen (NBO) [15,16]. Additionally, Figure 2 shows that the molar volume increases with the introduction of manganese content. In the present samples, the glass densities vary from 4.57 to 5.56 gcm−3 and 3.23 to 4.38 gcm−3 after remelt, revealing a rather linear relationship with the manganese content. However, there are slight differences in the density between the before and after remelt (Figure 2c) samples due to the existence of a crystalline phase inside the glass system. The occurrence of crystal growth causes a decrease of NBO. The remelting effect of this glass network is the reconstruction of the structure of the glass system and an increase of NBO, causing a decrease in the density. The composition dependence of the molar volume gives information about the coordination state of the manganese cations. The density and molar volume for these glasses are compatible with the ionic size, atomic weight, and amount of different elements in the glasses.
  12. 12. Int. J. Mol. Sci. 2013, 14 1025 Table 1. The glass composition (mol%), density and molar volume of (100–x) [(B2O3)30(TeO2)70]-xMnO. MnO 0.1 0.2 0.3 0.4 B2O3 29.97 29.94 29.91 29.88 TeO2 69.93 69.86 69.79 69.72 ρ (g/cm3) 5.555 5.370 4.764 4.569 ρremelt (g/cm3) 4.3773 3.885 3.5798 3.2253 Vm (cm3) 22.734 23.507 26.483 27.604 Vm,remelt (cm3) 27.597 29.668 30.649 32.300 Figure 2. The density and molar volume of (a) borotellurite glasses; (b) the original (100–x) [(B2O3)30(TeO2)70]-xMnO glass samples and (c) the remelted samples.
  13. 13. Int. J. Mol. Sci. 2013, 14 1026 Figure 2. Cont. The experimental FTIR spectra for the borotellurite glasses doped with manganese (100–x) [(B2O3)30(TeO2)70]-xMnO, with x = 0.1, 0.2, 0.3 and 0.4 mol%, are presented in Figure 3a,b. The FTIR spectral bands of the glasses and their assignments are summarized in Table 2. The data were analyzed following the method proposed by Condrate [17], comparing the experimental data of the glasses with those of their corresponding crystalline compounds. The present study shows that the quantitative evolution of these glass structures are greatly influenced by the MnO concentration. The addition of MnO to the glass matrix leads to a drastic reduction in intensity between the ~520 and ~650 cm−1 absorption bands due to the Te–O bond between the trigonal bypiramidal unit [TeO4] and bridging oxygen and also contributes to the specific vibration of the Mn–O bond [18–20]. If we take into account the Mn–O bond vibrations’ contribution to the ~520 cm−1 absorption band, it seems that the controlled addition of manganese ions constricts, to a large degree, the bending motion of different boron-oxygen bonds and gradually increases the number of Mn–O linkages. The vibration of the B-O arrangement in the infrared region of 400–1400 cm−1 is more profound [20,21]. The medium absorption observed at ~1200 cm−1 is attributed to the B–O asymmetric stretching of the tetrahedral BO4 [18] and orthoborate group [21,22]. The intensity of this band decreases for the original samples from x = 0.1% to x = 0.4%. As for the remelted sample, the intensities of these bands remain the same as the concentration of manganese ions is increased. The band intensity at ~1400 cm−1 is due to the asymmetric stretching of the B–O bond from the [BO3] trigonal unit in varied borate rings [18,22,23]. The band intensity decreases with the increase in concentration of manganese ions for the original samples. The band intensities between ~1600 cm−1 and ~3200 cm−1 are assigned to the bending of O–H and the asymmetric stretching of O–H, respectively [24,25]. The occurrence of the O–H bond inside the glass for the x = 0.1% to x = 0.3% original samples corresponds to the existence of a crystal structure of manganese telluride borate, which is highly soluble and simply reacts with H2O. As the band
  14. 14. Int. J. Mol. Sci. 2013, 14 1027 intensity at ~1200 cm−1 and ~1400 cm−1 decreases, the band intensity at ~1600 cm−1 and ~3200 cm−1 also decreases and eventually disappears for the x = 0.4% original sample. There is no bending of O–H or stretching of O–H for the remelted sample because no crystal structure exists in the glass matrix, as affirmed by Figure 1b. Table 2. Frequencies and their assignments for the FT-IR spectra of (100–x) [(B2O3)30(TeO2)70]-xMnO. Peak positions (cm−1) ~520 ~650 ~1200 ~1400 ~1600 ~3200 Assignments Corresponds to the Mn–O bond The Te–O bond of the trigonal bypiramidal unit [TeO4] with NBO and the contribution of the specific vibration of the Mn–O bond The asymmetric stretching vibration of the B–O bond for the tetrahedral and orthoborate group The asymmetric stretching of the B–O bond from the [BO3] trigonal unit in diverse borate rings The bending of O–H The asymmetric stretching of O–H Figure 3. Selected FT-IR spectra of (a) the original sample; (b) the remelted sample. %T 3. Experimental Section A 13 g batch of the (1–x) [(B2O3)0.3(TeO2)0.7]-xMnO glass system, with x = 0.1, 0.2, 0.3 and 0.4 mol%, was prepared by mixing all of the components together. The mixture was mechanically ground and homogenized using an agate mortar for 15 min. The mixture was then preheated inside an alumina crucible in an electrical furnace for half an hour at a temperature of 400 °C. The preheated mixture was then transferred to the second furnace for one hour at a temperature of 950 °C. To improve homogeneity, the crucible was constantly shaken inside the furnace. The melt was then poured into a stainless steel cylindrically shaped split mold, which was preheated at 350 °C before being transferred
  15. 15. Int. J. Mol. Sci. 2013, 14 1028 to an annealing furnace for two hours at 350 °C. After two hours, the furnace was allowed to cool to room temperature. The cylindrically shaped samples obtained were then cut using low speed diamond blade to make parallel fine surfaces of 6 mm thickness. The unused part of the glass was taken and ground in to a fine powder. The fine powders were then remelted, and the entire procedure above was then repeated to examine the remelting effect. The entire procedure for the remelted sample preparation was the same, including the preheating, melting and annealing temperature, so that the conditions of the samples could be maintained as the conditions of the original samples. The amorphous nature of the glasses was ascertained from XRD analysis using an X-ray Diffractometer (PAnalytical (Philips) X’Pert Pro PW 3040/60). The density of each glass was measured using the Archimedes method with distilled water as the immersion liquid. A bulk glass was weighed in air (Wair), immersed in distilled water and then reweighed (Wdw), where the density of the distilled water was 1.00 g cm−3. The relative density is given as ρs = ρdw (Wair/Wdw) [26]. 4. Conclusions Borotellurite glass doped with manganese oxide was prepared by the melt-quenching technique. The XRD, density and molar volume of the glasses were discussed. The overall features of the XRD curves showed that the occurrence of peaks for the 0.1 mol% and 0.2 mol% samples are due to the existence of crystal seeds inside this glass structure. However, for the 0.3 mol% sample, the XRD pattern confirms the amorphous nature of the glass. The remelting effect, on the other hand, reconstructs the glass structure and avoids the nucleation of crystal growth. This result was confirmed by the XRD patterns showing the amorphous nature of all of the remelted glasses. Density was observed to decrease with the increase of MnO in the glass and the remelting effect. However, a slightly different density was shown for both glass systems due to the existence of crystallites inside the remelted glass network. This effect reconstructed the structure of the glass system and increased the amount of nonbridging oxygen inside the system, causing the density to decrease after it was remelted, which was proven by the FT-IR spectral analysis. Acknowledgments The researchers gratefully acknowledge the financial support from Universiti Putra Malaysia for this study through the Research University Grant Scheme (RUGS) no. 91748. References 1. 2. Prakash, G.V.; Rao, D.N.; Bhatnagar, A.K. Linear optical properties of niobium-based tellurite glass. Solid State Comm. 2001, 119, 39–44. Durga, D.K.; Veeraiah, N. Role of manganese ions on the stability of ZnF2–P2O5–TeO2 glass system by the study of dielectric dispersion and some other physical properties. J. Phys. Chem. Solids 2003, 64, 133–146.
  16. 16. Int. J. Mol. Sci. 2013, 14 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 1029 Eraiah, B. Optical properties of samarium doped zinc-tellurite glasses. Bull. Mater. Sci. 2006, 29, 375–378. Rajendran, V.; Palanivelu, N.; Chaudhuri, B.K.; Goswami, K. Characterisation of semiconducting V2O5–BiO3–TeO2 glasses through ultrasonic measurements. J. Non-Cryst. Solids 2003, 320, 195–209. Khaled, M.A.; Elzahed, H.; Fayek, S.A.; El-Ocker, M.M. Optical absorption, infrared and differential thermal analysis studies of borotellurite glass containing nickel. Mater. Chem. Phys. 1994, 37, 329–332. Sekiya, T.; Mochida, N.; Ohtsuka, A.; Tomozawa, M. Raman spectra of MO1/2-TeO2 (M = Li, Na, K, Rb, Cs and Tl) Glasses. J. Non-Cryst. Solids 1992, 144, 128–144. Ghosh, A.; Pan, A. Scaling of the Conductivity Spectra in Ionic Glasses: Dependence on the Structure. Phys. Rev. Lett. 2000, 84, 2188–2190. El-Mallawany, R. Tellurite Glasses Handbook, Physical Properties and Data; CRC Press: Boca Raton, FL, USA, 2002; p. 540. Saddeek, Y.B.; Abd El Latif, L. Effect of TeO2 on the elastic moduli of sodium borate glass. Physica B 2004, 348, 475–484. Halimah, M.K.; Sidek, H.A.A.; Daud, W.M.; Zainul, H.; Talib, Z.A.Z.; Zaidan, A.W.; Zainal, A.S.; Mansor, H. Ultrasonic Study and Physical Properties of Borotellurite Glasses. J. Appl. Sci. 2005, 2, 1541–1546. Mandal, S.; Ghosh, A. Electrical conduction in lead-iron glasses J. Phys. Condens. Matter 1996, 8, 829–836. Halimah, M.K.; Daud, W.M.; Sidek, H.A.A.; Zainal, A.T.; Zainul, H. Optical Properties of Borrotellurite Glasses. Am. J. Appl. Sci. 2005, Special Issue, 30–33. Chowdari, B.V.R.; Kumari, P. Synthesis and characterization of silver borotellurite glasses. Solid State Ionics 1996, 86, 521–526. Dutta, D.; Ghosh, A. Dynamics of Ag+ ions in binary tellurite glasses. Phys. Rev. B 2005, 72, 024201:1–024201:6. Durga, D.K; Veeraiah, N. Physical properties of ZnF2–As2O3–TeO2 glasses doped with Cr3+ ions. Physica B 2002, 324, 127–141. El-Desoky, M.M.; Al-Assiri, M.S. Structural and Polaronic transport properties of semiconducting CuO–V2O5–TeO2 glasses. Mater Sci. Eng. B 2007, 137, 237–246. Condrate, R.A. Vibrational spectra of structural units in glass. J. Non-Cryst. Solids 1986, 84, 26. Ardelean, I.; Simona, C.; Lucacel, R.C.; Hulpus, O. EPR and FT-IR spectroscopic studies of B2O3–Bi2O3–MnO glasses. Solid State Sci. 2005, 7, 1438–1442. Bentley, F.; Smithson, L.D.; Rozek, A.L. Infrared-Spectra and Characteristic Frequencies 700–300 cm−1; Interscience: New York, NY, USA, 1986, p. 103. Lucacel, R.C.; Marcus, C.; Timar, V.; Ardelean, I. FT-IR and Raman spectroscopic studies on B2O3–PbO–Ag2O glasses doped with manganese ions. Solid State Sci. 2007, 9, 850–854. Fuxi, G. Optical and Spectroscopic Properties of Glass; Springer: Berlin, Germany, 1991; pp. 32–40. Yiannopoulos, Y.D.; Chryssikos, G.D.; Kamitsos, E.I. Structure and properties of alkaline earth borate glasses. Phys. Chem. Glasses 2001, 42, 164–172.
  17. 17. Int. J. Mol. Sci. 2013, 14 1030 23. Kamitsos, E.I.; Karakassides, M.A. Far-infrared spectra of binary alkali borate glasses. Phys. Chem. Glasses 1989, 30, 19. 24. Nikolic, G.; Zlatkovic, S.; Cakic, M.; Cakic, S.; Lacnjevac, C.; Rajic, Z. Fast Fourier Transform IR Characterization of Epoxy GY Systems Crosslinked with Aliphatic and Cycloaliphatic EH Polyamine Adducts. Sensors 2010, 10, 684–696. 25. Yongzhong, J.; Shiyang, G.; Shuping, X.; Jun, L. FT-IR spectroscopy of supersaturated aqueous solutions of magnesium borate. Spectrochim Acta A Mol. Biomol. Spectrosc. 2000, 56, 1291–1297. 26. Sidek, H.A.A.; Bahari, H.R.; Halimah, M.K.; Yunus, W.M.M. Preparation and Elastic Moduli of Germanate Glass Containing Lead and Bismuth. Int. J. Mol. Sci. 2012, 13, 4632–4641. © 2013 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/)
  18. 18. Journal of Non-Crystalline Solids 361 (2013) 78–81 Contents lists available at SciVerse ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol Study of the elastic properties of (PbO)x(P2O5)1 − x lead phosphate glass using an ultrasonic technique Khamirul Amin Matori a, b,⁎, Mohd Hafiz Mohd Zaid a, Sidek Hj. Abdul Aziz a, Halimah Mohamed Kamari a, Zaidan Abdul Wahab a a b Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia a r t i c l e i n f o Article history: Received 31 July 2012 Received in revised form 18 September 2012 Available online 24 November 2012 Keywords: Glasses; Ultrasonic measurement; Elastic properties a b s t r a c t Fabrication of a series of binary (PbO)x(P2O5)1−x lead phosphate glasses with various mole fractions (x = 0.1 to 0.6) was carried out using a conventional melt-quenching method. The glass density was measured by using Archimedes principle. The ultrasonic wave velocities (Vl and Vt) of the glasses were determined at room temperature by using a nondestructive test: the digital signal processing technique of the Ultrasonic Data Acquisition System (Matec 8020, Matec Instruments, USA). The experimental data for the wave velocities and densities were then used to determine the elastic properties in each series of lead phosphate glass systems: the longitudinal, shear, bulk and Young's moduli; Poisson's ratio; and the Debye temperature. Based on the results obtained, the longitudinal, shear, bulk and Young's moduli of the glasses increased with the addition of PbO content. The Poisson's ratio obtained remains almost constant, while the Debye temperature shows a continuous decrease with the addition of PbO content. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Recently, phosphate glasses have become technologically important materials, primarily because of their relatively large thermal expansion coefficients, low optical dispersions and low glass transition temperatures [1–5]. Phosphate glasses have been extensively investigated due to their transparency in a wide spectral range from UV to IR, which makes them suitable for the fabrication of optical fibers, detection, sensing and laser technologies (laser host glasses) [6]. Phosphate glass is also important for the study of hazardous waste immobilization [7,8]. Phosphate glasses have unique characteristics and bond lattices, which include a low melting point, a high thermal stability, a high gain density, a low refractive index and a low dispersive power [9–12]. Pure phosphate glass has a very viscous hygroscopic nature [13–15], so many studies were conducted to improve its chemical resistance. Various studies related to the preparation and use of phosphate glass have been widely carried out in areas such as bioceramics and glass with metal connectors for semiconductor materials. Phosphate glass is important in glass technology because the pure phosphate glass ⁎ Corresponding author at: Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. Tel.: +60 3 89466653; fax: +60 3 89454454. E-mail addresses: khamirul@science.upm.edu.my (K.A. Matori), mhmzaid@gmail.com (M.H.M. Zaid), sidekaa@science.upm.edu.my (S.H.A. Aziz), halimah@science.upm.edu.my (H.M. Kamari), zaidan@science.upm.edu.my (Z.A. Wahab). 0022-3093/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jnoncrysol.2012.10.022 viscosity is low at the melting point [16], and it is suitable for use as a host of the network modifier ions in the glass matrix. Phosphate glasses containing rare-earth ions have important applications in optical fibers, sensors, and radiation shield glasses. These glasses also have been used in optoelectronics technology for the fabrication of solid-state lasers [7,17]. Research in the field of glass and crystal using ultrasonic methods has been carried out for many years. Anderson et al. [18,19] studied silica glass at different pressures, temperatures and frequencies. After that, the study of silica glass using ultrasonic methods was continued by Cantrell et al. [20], and the study of other types of glass, such as borate, phosphate and others, followed [21–24]. In a study of the elastic constants of materials using ultrasonic methods, the main point to note is the ultrasonic wave propagation velocity and the density [25]. From the data for the ultrasonic wave propagation velocity mode, the series elastic constants can be determined. Due to the elastic constants of this second-order difference of the total energy of the strain, the constant values can be used to explore the bonding forces between the atoms in the material [26]. Typically, when the material undergoes a phase change, the value of the elastic constants will also change. In the study of glass samples, the ultrasonic method is greatly influenced by the density of the sample. The phosphate density is lower than the density of the glass modifier. The addition of phosphate glass modifier in the glass will increase the density of the glass produced. This is proved by the addition of V2O5 by Farley et al. [27], Fe2O3 by Brassington et al. [28], Sm2O3 by Mierzejewski et al. [29],
  19. 19. K.A. Matori et al. / Journal of Non-Crystalline Solids 361 (2013) 78–81 79 5200 and ZnO by Higazy [30] to phosphate glass, which increases the density. In the present work, PbO has been added to the phosphate glass network to improve its chemical durability as a glass modifier. The elastic properties of (PbO)x(P2O5)1−x glasses have been discussed by looking at the structural modifications that take place in the glass network. 5000 4800 4600 4400 2. Experimental 4200 A series of (PbO)x(P2O5)1−x lead phosphate binary glasses (where x = 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 mol%) were prepared by the conventional melt quenching method. The starting materials, phosphorus pentoxide (P2O5) with a purity of 97% and lead oxide (PbO) with a purity of 98% were weighed in appropriate quantities according to the mol% of the samples. The powdered mixture was placed in a crucible and melted in an electrical furnace to obtain a homogenous melt at 1100 °C for 1 h. A special mold was made to obtain samples with a cylindrical shape and dimensions of 10 mm × 20 mm. The glass melt was poured into the stainless steel mold. All of these glass samples were annealed at 400 °C (below Tg) for 1 h to remove the thermal strain. The glass samples were later cut and polished to obtain flat, parallel end faces that were suitable for ultrasonic measurements. The density measurement was performed using the Archimedes method with acetone as the buoyant liquid. The room-temperature ultrasonic measurements were carried out at 10 MHz using x-cut and y-cut quartz transducers. A pulse superposition technique was employed using an Ultrasonic Data Acquisition System (Matec 8020, Matec Instruments, USA). Burnt honey was used as a bonding material between the glass samples and the transducers. By measuring the thickness of the sample (d), longitudinal (Vl) and transverse (Vt) wave velocities were calculated using the relation V = 2d/t. The absolute accuracy in the measurement of the velocity is ±5 m s−1, and the relative error is ±0.1%. In an amorphous solid, the elastic strain produced by a small stress can be described by two independent elastic constants, C11 and C44. Elastic moduli were calculated using the following standard relations. 2 Longitudinal modulus C11 ¼ L ¼ ρV l ; ð1Þ 2 Shear modulus C44 ¼ G ¼ ρV t ; ð2Þ Bulk modulus K ¼ L–ð4=3ÞG; ð3Þ Young’s modulus E ¼ ð1 þ σ Þ2 G; ð4Þ Poisson’s ratio σ ¼ ðL–2GÞ=2ðL–GÞ; ð5Þ 3. Results and discussion The density of the binary lead phosphate glasses (PbO)x(P2O5)1−x together with the molar volume, sound velocities (both longitudinal and transverse), the calculated elastic constants (C11 and C44), the bulk modulus (K), Young's modulus (E), Poisson's ratio (σ) and the 4000 3800 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 PbO mol% Fig. 1. Variation of density versus PbO mol%. Debye temperature obtained from the experimental results are given in Table 1. Lead phosphate glasses are interesting systems to study because the glass phase can be formed over a wide concentration. Moreover, PbO can enter the glass network both as a network modifier and also as a network former [23]. It was suggested that the addition of PbO to phosphate networks results in the formation of POPb bonds, leading to a dramatic improvement in the chemical durability of the phosphate glasses [31]. The variation of density versus mol% of PbO as shown in Fig. 1, suggests that the addition of PbO to phosphate glass networks causes a nonlinear increase in density. As shown in Fig. 1 the densities of (PbO)x(P2O5)1−x glasses increase with an increase of the PbO content. This change in density by the addition of PbO is related to the change in the atomic mass and the atomic volume of the constituent elements. The atomic masses of the Pb and P atoms are 207.20 and 30.87, and their atomic radii are 1.75, and 1.28 Å, respectively. This explains the increase in density with the increase in the PbO content. There is a nonlinear increase in density up to 40 mol%. For higher amounts of PbO, the increase in the density is highly pronounced. The addition of PbO and the decrease in the P2O5 concentration in the glass network caused the densities to increase, which indicates that the Pb 2+ acts as a network modifier, altering the structure of the glass by reducing nonbridging oxygens (NBOs) in the network, so that the structure turns out to be more compact. The possible reactions in the glass network can be represented as follows: h i h i P2 O5 ≡2 POO3=2 and PbO≡ PbO2=2 h i h i h i2− h iþ PbO2=2 þ 2 POO3=2 ↔ PbO4=2 þ 2 PO4=2 The additional oxygen sharing and charge-balance requirements are met by the conversion of P_O in [POO3/2] units to form PO in [PO4/2] + units. It is therefore suggested that the P_O bonds are titrated continuously to incorporate Pb into the network [32]. This process gives rise to the formation of POPb linkages. Fig. 2 shows that the molar volume of the glasses increases with increases in the PbO content. Both the density and the molar volume of Table 1 The values of density, molar volume, sound velocities, elastic moduli, Poisson's ratio and Debye temperature of (PbO)x(P2O5)1−x glasses. Glass sample (x) ρ (kg/m3) Vm (cm3/mol) Vl (m/s) Vt (m/s) C11 (GPa) C44 (GPa) K (GPa) E (GPa) σ ƟD (K) 0.1 0.2 0.3 0.4 0.5 0.6 4136 4275 4470 4521 4706 4856 36.3 37.0 37.1 38.6 38.8 39.3 2706 2857 2912 3011 3141 3237 1576 1664 1702 1765 1788 1844 30.3 34.9 38.0 41.0 46.4 50.9 10.3 11.8 12.9 14.1 15.0 16.5 16.6 19.1 20.6 22.2 26.4 28.9 25.5 29.4 32.1 34.9 37.9 41.6 0.238 0.242 0.243 0.244 0.256 0.261 256 253 251 249 244 240
  20. 20. 80 K.A. Matori et al. / Journal of Non-Crystalline Solids 361 (2013) 78–81 60 C11 50 39 Elastic modulus (GPa) Molar Volume (cm3/mol) 40 38 37 36 E 40 30 K 20 C44 10 35 0 0.1 0.2 0.3 0.4 0.5 0.6 0 0.7 0 PbO mol% 0.1 0.2 0.3 0.4 0.5 0.6 0.7 PbO mol% Fig. 2. Variation of molar volume versus PbO mol%. Fig. 4. Variation of elastic moduli versus PbO mol%. the glasses increase with an increase in PbO. The density and molar volume increase by replacing P2O5 by PbO. As shown in Fig. 1 and Fig. 2 the density of (PbO)x(P2O5)1−x glasses varies from 4136 to 4856 kg m −3 and that the molar volume varies from 36.3 to 39.3 cm3 mol−1. Generally, the density and the molar volume show opposite behaviors, but in this study, different results were obtained. In this glass, the substitution of phosphorus by lead causes an expansion of the network. Similar trends for densities and molar volumes have already been reported elsewhere for other glass systems [16,24,33,34]. It is clear that by increasing PbO, the molar volume increases, which is similar to the variation density that occurs with increasing PbO content. The Pb ions may enter the glass network interstitially; hence, some network POP bonds are broken and replaced by ionic bonds between Pb ions and singly bonded oxygen atoms. Therefore, if one assumed that the only effect of adding Pb cations was to break down the network POP bonds, then an increase in the molar volume with PbO content would be expected for the entire vitreous range of the studied glass system. Experimentally, this effect increases the molar volume, and as a consequence, the values of the density are increased. The addition of PbO increased the values of the density, which is most likely attributable to simultaneous filling up of the vacancies in the network by the interstitial Pb ions with an atomic mass of 207.20. This increase in density indicates a structural change in the glass network, which is accompanied by an increase in the molar volume [35]. The addition of PbO in glass interstices causes more ions to fill up the network, thus compacting the glass structure and increasing the rigidity of the network. As a consequence, both velocities Vl and Vt increase with the addition of PbO, as shown in Fig. 3. An increase of the ultrasonic velocities with an increase in the PbO concentration has been observed, which indicates that PbO plays a dominant role in the velocities. In this (PbO)x(P2O5)1−x glass system, PbO plays the role of a network modifier. It will modify the glass structure, thus causing the glass to become harder. Although the glass is harder, this does not mean that the glass is dense. The independent elastic constants for isotropic solids and glasses are the longitudinal modulus (C11) and the shear modulus (C44). The calculation of other elastic constants and Poisson's ratio depends on the values of the density and on both of the velocities. The sound velocities also determine Young's modulus, which is defined as a ratio of the linear stress over the linear strain and is related to the bond strength. Additionally, the bulk modulus is defined as the change in volume when a force is acting upon it in all directions. Fig. 4 shows the variation of the elastic moduli; C11, C44, K and E versus mol% of PbO. It can be observed that for every type of glass, there is a similar pattern in the elastic moduli with increases of the PbO content in the composition. The values of the elastic moduli increase linearly with increases in the PbO content. In general, the addition of PbO to a phosphate glass network increases the rigidity, the velocity and hence the elasticity of the glass. The increase in the rigidity of the glass contributes to the increase in the velocity and elastic moduli. Poisson's ratio obtained from elastic moduli remains almost constant and linearly increases from 40 mol% PbO and above, while the Debye temperature obtained from ultrasonic velocities shows a continuous decrease with the addition of PbO, as shown in Figs. 5 and 6. Although the modulus is sensitive to structural changes in glasses because it depends on the change in the cross-link density, the observation made about Poisson's ratio supports the finding that there is no appreciable change in cross-link densities with the addition of PbO. The change in the cross-link density of the glass network is well understood from the variation in Poisson's ratio. In general, a high cross-link density has a Poisson's ratio on the order of 0.1 to 0.2 [29], while a low cross-link density has a Poisson's ratio between 0.3 and 0.5. In the present system, Poisson's ratio (Fig. 5) is almost constant 3400 0.27 Longitudinal velocity Poisson's ratio Velocity (m/s) 2900 2400 Transverse velocity 1900 0.26 0.25 0.24 1400 0.23 0 0.1 0.2 0.3 0.4 0.5 PbO mol% Fig. 3. Variation of sound velocities versus PbO mol%. 0.6 0.7 0 0.1 0.2 0.3 0.4 0.5 Pbo mol% Fig. 5. Variation of Poisson's ratio versus PbO mol%. 0.6 0.7
  21. 21. K.A. Matori et al. / Journal of Non-Crystalline Solids 361 (2013) 78–81 81 Debye temperature (K) 260 Acknowledgments 255 The researchers gratefully acknowledge the financial support for this study from the Malaysian Ministry of Higher Education (MOHE) through the Fundamental Research Grant Scheme (5523753). 250 245 References 240 235 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 PbO mol% Fig. 6. Variation of Debye temperature versus PbO mol%. (changes from 0.238 to 0.261) when the PbO content is increased. The observed Debye temperature, obtained from the ultrasonic velocity data, is particularly sensitive to the PbO content (Fig. 6). The observed decrease in the Debye temperature with the addition of PbO supports the finding that the addition of PbO content indicates the compact packing structure of the glass structure and a reduction in the creation of NBOs, as discussed above. 4. Conclusions The elastic properties of binary (PbO)x(P2O5)1−x lead phosphate glass systems have been studied to ascertain the role of Pb 2+ ions in these glasses. Based on the results obtained, the density and molar volume increase with the addition of PbO in the (PbO)x(P2O5)1−x glass system. The velocities (Vl and Vt) and elastic moduli (C11, C44, K, and E) show gradually increasing trends as PbO is being added into the lead phosphate glass network. Poisson's ratio remains almost constant in the early stage and then increases, while the Debye temperature obtained from ultrasonic velocities shows a continuous decrease with the addition of PbO content. The addition of PbO in the glass network caused the densities to increase according to the atomic mass and atomic radii of the Pb atoms. In addition, the addition of PbO and the decrease of the P2O5 concentration in the glass network caused the densities to increase, which indicates that the Pb 2+ acts as a network modifier, altering the structure of the glass by reducing the non-bridging oxygens (NBOs) in the network and causing the structure to be more compact. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] N.H. Ray, C.J. Lewis, J.N.C. Laycock, W.D. Robinson, Glass Technol. 14 (1973) 50. N.H. Ray, J.N.C. Laycock, W.D. Robinson, Glass Technol. 14 (1973) 55. Y.B. Peng, D.E. Day, Glass Technol. 32 (1991) 166. Y.B. Peng, D.E. Day, Glass Technol. 32 (1991) 200. Y. He, D.E. Day, Glass Technol. 33 (1992) 214. R. Praveena, V. Venkatramu, P. Babu, C.K. Jayasankar, Phys. B 403 (2008) 3527. P. Stoch, M. Ciecinska, J. Therm. Anal. Calorim. 108 (2012) 705. M.I. Ojovan, W.E. Lee, Metall. Mater. Trans. A 42 (2011) 837. M.I. Ojovan, W.E. Lee, J. Non-Cryst. Solids 356 (2010) 2534. G. Le Saout, Y. Vaills, Y. Luspin, Solid State Commun. 123 (2002) 49. B. Eraiah, S.G. Bhat, Phys. Chem. Solids 68 (2007) 581. P. Jozwiak, J.E. Garbarczyk, Solid State Ionics 176 (2005) 2163. K.V. Shah, V. Sudarsan, M. Gaswami, A. Sarkas, S. Manikandan, R. Kumar, B.I. Sharma, V.K. Shrikhande, G.P. Kothiyal, Bull. Mater. Sci. 26 (2003) 715. L.D. Burling, PhD thesis, University of Nottingham (2005). K. Suzuya, D.L. Price, C.K. Loong, B.C. Sakas, L.A. Boatner, in: Proceeding of Materials Research Society, 1994. H.A.A. Sidek, S. Rosmawati, Z.A. Talib, M.K. Halimah, W.M. Daud, Am. J. Appl. Sci. 6 (2009) 1489. H.M. Farok, H.B. Senin, G.A. Saunders, W. Poon, H. Vass, J. Mater. Sci. 29 (1994) 2847. O.L. Anderson, H.E. Bommel, J. Am. Ceram. Soc. 38 (1955) 125. O.L. Anderson, J. Phys. Chem. Solids 27 (1966) 547. J.H. Cantrell, M.A. Breazeale, Phys. Rev. B 17 (1978) 4864. A. Tawansi, I.A. Gohar, D. Holland, N.A. El-Shishtawi, J. Phys. D: Appl. Phys. 21 (1988) 607. H.A.A. Sidek, S.P. Chow, Z.A. Talib, S.A. Halim, Turk. J. Phys. 28 (2004) 67. M. Hamezan, H.A.A. Sidek, A.W. Zaidan, K. Kaida, A.T. Zainal, J. Appl. Sci. 6 (2006) 943. Y.B. Saddeek, J. Alloys Compd. 467 (2009) 14. K.A. Matori, M.H.M. Zaid, H.A.A. Sidek, M.K. Halimah, Z.A. Wahab, M.G.M. Sabri, Int. J. Phys. Sci. 5 (2010) 2212. M.H.M. Zaid, K.A. Matori, L.C. Wah, H.A.A. Sidek, M.K. Halimah, Z.A. Wahab, B.Z. Azmi, Int. J. Phys. Sci. 6 (2011) 1404. J.M. Farley, G.A. Saunders, Phys. Status Solidi 28 (1975) 199. M.P. Brassington, A.J. Miller, J. Pelzl, G.A. Saunders, J. Non-Cryst. Solids 44 (1981) 157. A. Mierzejewski, G.A. Saunders, H.A.A. Sidek, B. Bridge, J. Non-Cryst. Solids 104 (1988) 323. A.A. Higazy, B. Bridge, A. Hussein, M.A. Ewaida, J. Acoust. Soc. Am. 86 (1989) 1453. P.Y. Shih, S.W. Yung, T.S. Chin, J. Non-Cryst. Solids 224 (1998) 143. B. Bridge, A.A. Higazy, Phys. Chem. Glasses 27 (1986) 1. S.E. Van Kirk, S.W. Martin, J. Am. Ceram. Soc. 75 (1992) 1028. Y.B. Saddeek, Mater. Chem. Phys. 83 (2004) 222. V. Rajendran, N. Palanivelu, D.K. Modak, B.K. Chaudhuri, Phys. Status Solidi A 180 (2000) 467.
  22. 22. Int. J. Mol. Sci. 2013, 14, 3201-3214; doi:10.3390/ijms14023201 OPEN ACCESS International Journal of Molecular Sciences ISSN 1422-0067 www.mdpi.com/journal/ijms Article Structural and Optical Properties of Lead-Boro-Tellurrite Glasses Induced by Gamma-Ray Iskandar Shahrim Mustafa 1, Halimah Mohamed Kamari 2,*, Wan Mohd Daud Wan Yusoff 2, Sidek Abdul Aziz 2 and Azhar Abdul Rahman 1 1 2 School of Physics, Universiti Sains Malaysia, 11800 Minden, Pulau Pinang, Malaysia; E-Mails: iskandarshah@usm.my (I.S.M.); arazhar@usm.my (A.A.R.) Physics Department, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia; E-Mails: wmdaud@science.upm.edu.my (W.M.D.W.Y.); sidek@science.upm.edu.my (S.A.A.) * Author to whom correspondence should be addressed; E-Mail: halimah@science.upm.edu.my; Tel.: +603-89466657; Fax: +603-89454454. Received: 25 October 2012; in revised form: 9 January 2013 / Accepted: 12 January 2013 / Published: 4 February 2013 Abstract: Spectrophotometric studies of lead borotellurite glasses were carried out before and after gamma irradiation exposure. The increasing peak on the TeO4 bi-pyramidal arrangement and TeO3+1 (or distorted TeO4) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. The structures of lead tellurate contain Pb3TeO6 consisting of TeO3 trigonal pyramid connected by PbO4 tetragonal forming a three-dimensional network. The decrease of glass rigidity is due to irradiation process which is supported by the XRD diffractograms results. The decreasing values of absorption edge indicate that red shift effect occur after irradiation processes. A shift in the optical absorption edge attributed to an increase of the conjugation length. The values of optical band gap, Eopt were calculated and found to be dependent on the glass composition and radiation exposure. Generally, an increase and decrease in Urbach’s energy can be considered as being due to an increase in defects within glass network. Keywords: tellurite glass; optical band gap; Urbach’s energy; irradiation
  23. 23. Int. J. Mol. Sci. 2013, 14 3202 1. Introduction Glass in an amorphous (non-crystalline) solid material. Glasses are typically brittle and optically transparent. The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica (SiO2) plus sodium oxide (Na2O) from soda ash, CaO, and several minor additives. Some glasses that do not include silica as a major constituent may have physico-chemical properties useful for their application in fibre optics and other specialized technical applications. These include fluoride glasses, tellurite glasses, aluminosilicates, phosphate glasses, borate glasses and chalcogenide glasses. Tellurite glasses contain tellurium oxide (TeO2) as the main component. Tellurium dioxide is known as a conditional glass former, which it is, needs a modifier in order to easily form the glassy state. The formation of glass on two glass formers interest both scientific and practical locale. The structural network will be perturbed and may lead to the formation of new structural units [1,2]. Glass forming substances are fall into two categories of inorganic compounds containing bonds which are partially ionic and partially covalent, and, inorganic or organic compounds which form chain structures with covalent bonds within the chains and van der Waals’ bonds between the chains. Glasses containing heavy metal oxide (HMO) have recently attracted the attention of several researchers for the excellent infrared transmission compared with conventional glasses. The γ-irradiation on glasses is found to affect the optical and physical properties [3,4]. Hence, radiation damage caused by electrons, alpha particles and gamma rays has been thoroughly investigated [5]. The structural and physical properties of PbO glasses are well described by Worrel and Henshell [6]. In previous work, Atul et al. [7] have studied borate glasses containing heavy-metal oxides and shown that it has potential applications in radiation shielding. The objective of the present work is to study the effect of radiation on the structural and optical properties of lead borotellurite glass system. To achieve this, a systematic study on optical properties has been performed to understand the variation of irradiation dose as a function of PbO composition in borotellurite glasses. In addition, X-ray diffraction patterns and Raman spectra measurements were also performed in order to support the available data. 2. Results and Discussion 2.1. Raman Spectra Marker labeling of Raman peak is shown in Table 1. Raman spectrum in Figures 1 and 2 were corrected for baseline and normalized which allows for an effective comparison across a heterogeneous set of samples. Eventually, the baseline correction utilized the multiple point level method (Savitzgy-Golay) in which the baseline is leveled at a value that is the average of the baseline points. Normalization of Raman spectral was performed based on the common normalization method referring to min/max technique. The min/max (normalization) method is expressed by: (1) where I is the intensity after baseline correction was performed, Imin is the minimum intensity and Imax is the maximum intensity on single spectral measured. Raman spectrum in Figure 1 shows significant
  24. 24. Int. J. Mol. Sci. 2013, 14 3203 peak at <100 cm−1 which indicate the strong presence of Pb and Te in the chemical bonding through vibrational mode due to addition of PbO and glass network. PbO stands out as unique because of its dual role [8], one as modifier, if Pb–O bond is ionic and the other as glass former with PbO4 structural units, if Pb–O bond is covalent. Occasionally, PbO concentration deteriorates glass forming ability [9] of (TeO2)y[(PbO)x(B2O3)1−x]1−y system. The addition of heavy metal oxide modifiers to pure TeO2 leads to the progressive formation of distorted TeO3+1 polyhedron followed by the creation of regular trigonal TeO3 pyramids that contain non-bridging oxygen. In all compositions, the appearance of the low-frequency Boson peak (<200 cm−1) affirms the presence of the glass structure. The increase broad shoulders at 410 cm−1 indicate that new features to vibrations of one of the partially crystalline phase of Pb3TeO6. The existence of Pb3TeO6 is confirmed by X-ray analysis. Clearly, the shoulders at 410 cm−1 were getting broader as the content of PbO increased, possibly due to the PbO unique ability. At low portions of PbO (up to 0.2% mol), it enters the glass network by breaking up the Te–O–Te and B–O–B bonds and introduces coordinate defects known as dangling bonds along with non-bridging oxygen ions (Te–O−…Pb2+…−O–Te) which in turn neutralizes the negative charge of non-bridging oxygens (NBO) by forming TeO3 and BO4 units. Normally, the oxygen of PbO breaks the local symmetry while Pb2+ ions occupy interstitial positions. As PbO increases (from 0.3% to 0.5% mol), a considerable portion may be acts as a double bridges between adjacent TeO4 such as =Te–O–Pb–O–Te= which can formed besides the formation of PbO4 and TeO3 units. Therefore, for PbO ≥ 0.3% mol, Pb2+ acts as glass forming agent and is incorporated in the glass network in the form of PbO4 units. Decreasing on (ss) Te–O–Te and B–O–B bending shoulder at approximately 490 cm−1 and 450 cm−1 ascribe that the splitting of Te–O–Te and B–O–B bonds and hence, the bridging oxygen’s (BOs) are converted into NBOs. The pure B2O3 was known to consist of the boroxol rings by linking among trigonal-plane BO3 units, but the network structure was altered through the addition of PbO. Some parts of the boroxol ring of BO3 units were changed into BO4 tetrahedral units [10]. TeO4 trigonal bipyramids is known to be the main structural unit of the network of all tellurite glasses [11], as well as of the lattices of crystalline TeO2 polymorphs. All stable tellurite glasses are multi-component and, what is important, cations on non-tellurite components have a coordination number other than four. The tellurite structural units of two types are always present in multi-component tellurite glass network, namely, fourfold coordinated Te atoms (TeO4 trigonal bipyramids, where all O atoms from bridging bonds with the environment) and threefold coordinated Te atoms (O=TeO2 trigonal pyramids, where one of O atoms is non-bridging, one forms O=Te double bond and one O atoms form bridging bonds with the environment). The spectral features from 710 cm−1 to 730 cm−1 and 790 cm−1 in Figure 1 correspond to the TeO4 bi-pyramidal arrangement and the TeO3+1 (or distorted TeO4) and TeO3 trigonal pyramids structures respectively. It can be clearly observed that the evolution of TeO4 to TeO3+1 and TeO3 units which one of the Te sp3 hybrid orbital is occupied by a lone pair of electron. This transformation causes increases in the number of non-bridging oxygen (NBO) atoms. Legitimately, the increasing peak on the TeO3 trigonal pyramids shows that modification of lattice and interstitial occurs in the system due to addition of PbO and B2O3.
  25. 25. Int. J. Mol. Sci. 2013, 14 3204 Table 1. Marker labeling Raman peak according to chemical bonding and stretching [12]. Raman Shift (cm−1) Bonding S—Strong W—Weak B—Bending G—Group as—Asymmetry stretching ss—Symmetry stretching (S) <100cm−1; (S) 450 cm−1; 410 cm−1; (W) 490 cm−1; (S) 710 cm−1 ; (S) 730 cm−1; (S) 790 cm−1–860 cm−1; Pb, Te B–O–B (b) Te–O–Te (ss) TeO4 bi-pyramidal arrangement TeO3+1 (distorted TeO4) Te–O bending vibrations in TeO3 trigonal pyramids and TeO6 Figure 1. Raman spectra (at ambient temperature) of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with different compositions before irradiation. 1.0 Normalized Raman Intensity (a.u.) 0.9 0.8 0 Pb 0.7 0.1 Pb 0.2 Pb 0.6 0.3 Pb 0.5 0.4 Pb 0.5 Pb 0.4 Boson frequency peak region 0.3 0.2 0.1 0.0 0 200 400 600 Raman Shift (cm-1) 800 1000 Figure 2. Raman spectra (at ambient temperature) of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with different irradiation doses at x = 0.5% mol, y = 0.7% mol. 1.0 Normalized Raman Intensity (a.u.) 0.9 0 kGy 5 kGy 10 kGy 20 kGy 25 kGy 0.8 0.7 0.6 0.5 0.4 Boson frequency peak region 0.3 0.2 0.1 0.0 0 200 400 600 Raman Shift (cm-1) 800 1000
  26. 26. Int. J. Mol. Sci. 2013, 14 3205 The presence peaks at <100 cm−1 in Figure 2 do not indicate any strong changes of intensity due to variation of gamma irradiation exposure. Eventually, the decrease in broad shoulders at 410 cm−1 also indicates the existence of new features in the vibrations of the partially crystalline phase of Pb3TeO6. The existence of Pb3TeO6 is confirmed by X-ray analysis. Clearly, the shoulders at 410 cm−1 were getting lower as the irradiation dose increased, possibly due to the network compaction. The spectral features from 710 cm−1 to 730 cm−1 and 790 cm−1 correspond to the TeO4 bi-pyramidal arrangement and the TeO3+1 (or distorted TeO4) and TeO3 trigonal pyramids structures respectively. It can be clearly observed that the evolution of TeO3+1 and TeO3 units occurs as the TeO2 concentration decreases. Legitimately, the decreasing peak on the TeO4 bi-pyramidal arrangement and TeO3+1 (or distorted TeO4) is due to augmentation of irradiation dose which is attributed to an increase in degree of disorder of the amorphous phase. According to El-Alaily and Mohamed [3], irradiation with gamma rays are assumed to create displacements, electronic defects and/or breaks in the network bonds, which allow the structure to relax and fill the relatively large interstices that exist in the interconnected network of boron and oxygen atoms causing expansion followed by compaction of the volume. Shelby [13] also suggested that the boron-oxygen bond is more likely to be affected by irradiation. 2.2. XRD The XRD diffractograms result in Figure 3 shows the partially crystalline precipitation before and after irradiation exposure for x = 0.5% mol; y = 0.7% mol. All the glass that was prepared proved to fit the amorphous state. In addition to the enhanced amount of PbO, the glass had been acclimatized to the partially crystalline phase from the full amorphous phase. It also shows the presence of a hunch for 2θ around 20°–35°. All these XRD reflections were assigned to the two polymorphic phases; hexagonal of tellurium (Te, PDF2 No. 00-036-1402) and monoclinic of lead tellurate (Pb3TeO6, PDF2 No. 00-033-0770). The intensity of the XRD reflections indicate that more monoclinic crystals are reduced in quenched samples as the modifier content increases. The structures of lead tellurate contain Pb3TeO6 probably consisting of TeO3 trigonal pyramid connected by PbO4 tetragonal, forming a three-dimensional network. The decrease of glass rigidity is due to irradiation processes which are supported by the XRD diffractogram results in Figure 3. The XRD result shows the presence of crystalline precipitation before irradiation process. However, the partially crystalline peaks vanished due to 5 kGy of gamma irradiation exposure. Eventually, modification of lattice and structural arrangement along with network compaction occurs in the system due to irradiation exposure of more than 5 kGy which comprises the presence of crystalline peaks. As the irradiation dose increases (above 20 kGy), the crystalline peaks once again begin to diminish. Obviously, the partially crystalline glass still proved to fit the amorphous state as the irradiation dose increased.
  27. 27. Int. J. Mol. Sci. 2013, 14 3206 Figure 3. X-ray diffractogram patterns (at ambient temperature) of (TeO2)y[(PbO)x(B2O3)1−x]1-y glasses (x = 0.5% mol; y = 0.7% mol) with varied gamma irradiation dose. 25 kGy Tellurium, syn, Te (110) Lead Tellurate, Pb3TeO6 Relative Counts (a.u.) 20 kGy (440) Tellurium, syn, Te (114) Tellurium, syn, Te (114) Lead Tellurate, Pb3TeO6 10 kGy (440) Lead Tellurate, Pb3TeO6 (422) (440) Tellurium, syn, Te (114) 0 kGy 10 5 kGy Lead Tellurate, Pb3TeO6 (422) (440) Tellurium, syn, Te (114) 20 30 40 50 60 70 80 2θ 2.3. Optical Absorption Spectra The optical absorption spectra were taken in the ranges of 340 to 550 nm. The optical absorption is one of the most productive tools to understand the band gap of optical materials. The optical properties of a solid are governed by the interaction between the solid and the electric field of the electromagnetic wave. The optical absorption measurements coefficient α() near the fundamental is calculated from absorbance A, using the following Equation [14]: 2.303 ⁄ (2) where d is the thickness of the samples. The rapid change in α(ω) against ω is called “the fundamental absorption edge” and the corresponding energy is defined as “the optical energy gap (Eopt). In the compound, a typical absorption edge can be broadly ascribed to any of the three processes: (i) residual below-gap absorption; (ii) Urbach tails; and (iii) interband absorption. In the second process, the absorption edge depends exponentially on the photon energy according to the Urbach relation. In crystalline materials the fundamental edge is directly related to the conduction band and valence band, i.e., direct and indirect band gaps, while in the case of amorphous materials a different type of optical absorption edge is observed. Figure 4 illustrates the variation of absorption coefficient, α with incident photon energy at different doses. Urbach edge analysis is a useful way to parametrically characterize glass optical absorption edge and potentially distinguished intrinsic contributions to absorbance. Urbach’s absorption edge is formed in the region of photon energies below the forbidden gap. The interaction between lattice vibrations and localized states in tail of band gap from the glass samples has a significant effect on the optical properties. The plot of ln (α) against photon energy, ħω is linear for the absorption region near the fundamental absorption edge. Thus, it is evaluated that the absorption coefficient near the fundamental absorption edge is exponentially dependent on the photon energy and obeys the Ubach’s rule. Figure 5 illustrates the dependence of Urbach’s absorption edge with different irradiation of prepared glasses.
  28. 28. Int. J. Mol. Sci. 2013, 14 3207 The absorption edge decreases with the increase of dose. Significantly, the decreasing values of absorption edge indicate that after irradiation processes, there is red shift effect on the (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses. The red shift effect is a process when the absorbance band shifts to longer wavelength and widens due to irradiation. A shift in the absorption edge can be attributed to an increase of the conjugation length. The number of Te atoms and Pb atoms per conjugation length is found to increase with increasing dose which create structure defect within the prepared (TeO2)y[(PbO)x(B2O3)1−x]1−y glass. Figure 4. Optical absorption edge, α of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with y = x = 0.5% mol; 0.7% mol at various irradiation exposure. The lines represent the expolation. 8 0 kGy 7 5 kGy 6 10 kGy 20 kGy  (cm‐1) 5 25 kGy 4 3 2 1 0 1.5 2.0 2.5 ħω (eV) 3.0 3.5 Figure 5. The dependence of Urbach’s absorption edge on different irradiation dose for (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with y = x = 0.5% mol; 0.7% mol. 3.10 Absorpotion edge, ħω (eV) 2.90 2.70 2.50 0 % mol Pb  0.1 % mol Pb  0.2 % mol Pb  0.3 % mol Pb  0.4 % mol Pb  0.5 % mol Pb  2.30 2.10 1.90 1.70 1.50 0 5 10 15 Dose (kGy) 20 25 30 The optical band gap energy is determined by using the following Equation [15] (3)
  29. 29. Int. J. Mol. Sci. 2013, 14 3208 where α is the absorption coefficient, ħω is the incident photon energy, A is a constant and Eopt is the optical band gap. Values of n are 2 and 1/2 for direct and indirect transitions, respectively. Figure 6 shows the information of indirect band gap (αħω)1/2 against photon energy ħω of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with x = 0.5 mol %; y = 0.7 mol % at various irradiation exposure, plotted in the absorption region. Indirect energy gap is determined from the linear regions of the plots as shown in the figures and corresponding values presented in Table 2. The Eopt has been calculated approximately from the linear region of the arc extrapolating to meet the ħω axis at (αħω)1/2=0. Figure 6. Plot of (αħω)1/2 against photon energy for indirect band gap of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with y = x = 0.5% mol; 0.7% mol at various irradiation exposure. The lines represent the pattern. 6 (αħω)1/2 (cm‐1 eV)1/2 5 4 3 0 kGy 5 kGy 10 kGy 20 kGy 25 kGy 2 1 0 1.8 1.9 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 3.5 ħω (eV) The variation of indirect optical band gap with mole fraction of PbO content before and after irradiation is shown in Figure 7. The connected lines do not resemble any significant explanations rather than to show the decreasing and increasing pattern of the graph. The optical band gap values of the indirect process before irradiation decreases through the augment of PbO from 0% mol to 0.15% mol. This is due to the increase of the network disorder and consequently the extension of the localized states within the gap. More likely, PbO enters the glass network by breaking up the Te–O–Te and B–O–B bonds and introduces coordinate defects known as dangling bonds along with non-bridging oxygen. Normally, the oxygen of PbO breaks the local symmetry while Pb2+ ions occupy interstitial positions. PbO content >0.2% mol shows a slight increase before tends to decline slowly for 0 kGy and increase for irradiated samples with 5 kGy up to 25 kGy (towards 0.5% mol). Consequently, as PbO increases (from 0.2% to 0.5% mol), modification of lattice and interstitial occurs in the system with the nearest neighboring atoms and arrangements, such as PbO4 and/or BO4. A considerable portion may act as double bridges between adjacent TeO4 which can form in addition to the formation of PbO4 and TeO3 units. Therefore, for PbO ≥ 0.2% mol, Pb2+ acts as glass forming agent and is incorporated in the glass network in the form of PbO4 units. The optical band gap, Eopt values for indirect transition decrease with increasing of irradiation dosage as the content of PbO ≤ 0.2% mol due to increase in degree of disorder of the amorphous phase. Obviously, the Eopt values for indirect transition increase with increasing of irradiation dosage as the content of
  30. 30. Int. J. Mol. Sci. 2013, 14 3209 PbO > 0.2% mol. It is believed that the increasing of irradiation create displacements, electronic defects and/or breaks in the network bonds, which allow the structure to relax and fill the relative large interstices that exist in the interconnected network of boron and oxygen atoms causing expansion followed by compaction of the volume. Figure 7. Variation optical band gap, Eopt of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses for indirect transition with x = 0%–0.5% mol; y = 0.7% mol at various irradiation exposure. The lines represent the extrapolation. 3.00 Eopt (eV) 2.50 2.00 0 kGy 1.50 5 kGy 10 kGy 1.00 20 kGy 25 kGy 0.50 0 0.1 0.2 0.3 0.4 0.5 0.6 PbO, x (mol %) In many crystalline and non-crystalline semiconductors, the α(ω) depends exponentially on the ħω. This exponential dependence, known as the Urbach rule, can be written in the form [16]: ∆ (4) where B is a constant and ΔE is the width of the band tails of the localized states which also known as Urbach energy. The value of Urbach energy (ΔE) is calculated by taking the reciprocals of the slopes of the linear portion of the ln α() against ħω curves in the lower photon energy regions. Figure 8 shows the reciprocal of the slopes of the linear portion from the ln α() against ħω curves in the lower photon energy regions for (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with x = 0.5% mol; y = 0.7% mol at various irradiation exposure. The reciprocal values will be used to calculate the value of Urbach energy (ΔE) using the Equation 3. The values of (ΔE) of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses’ various irradiation exposure with x = 0.0%–0.5% mol; y = 0.7% mol are visualized in Figure 9 and tabulated in Table 2. Generally, an increase and decrease in Urbach energy can be considered as being due to defects within the glass network.
  31. 31. Int. J. Mol. Sci. 2013, 14 3210 Figure 8. Optical absorption coefficient of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses with y = x = 0.5% mol; 0.7% mol at various irradiation exposure. The line represents the pattern. 2.5 2.0 ln α (cm‐1) 1.5 1.0 0.5 0 kGy 5 kGy 10 kGy 20 kGy 25 kGy 0.0 ‐0.5 ‐1.0 ‐1.5 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4 ħω (eV) Figure 9. Variation Urbach energy, ΔE of (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses for indirect transition with x = 0%–0.5% mol; y = 0.7% mol at various irradiation exposure. The lines represent the pattern. 2.0 0 kGy 5 kGy 10 kGy 20 kGy 25 kGy ΔE (eV) 1.5 1.0 0.5 0.0 0 0.1 0.2 0.3 0.4 0.5 0.6 PbO, x (mol %) Urbach’s energy is a characteristic energy which determines how rapidly the absorption coefficient decreases for below band gap energy. Urbach measured the absorption tail for different temperatures and showed that the Urbach’s energy is approximately kT, the thermal energy. The temperature dependence of the urbach tail led to the conclusion that the below-bandgap transitions are assisted transition. The Urbach tail can be caused by mechanisms other than phonon-assisted absorption. Considering Figure 9, before irradiation took place, the Ubach energy having a non-prominent increase pattern when the content PbO in the network increase which illustrating the saturation of defects at high content of PbO. Other than that, it is more likely due to the increase of the disorder and consequently the more extension of the localized states. For every irradiation dose of between 5 kGy and 25 kGy, Ubach energy increases as the content of PbO ≤ 0.2% mol suggesting the increasing of disorder and consequently the further extension of the localized states. Nevertheless, Ubach energy for every irradiation dose from 5 kGy up to 25 kGy decreases as the content of PbO > 0.2% mol advocating the possibility of long range order locally arising from the minimum in the number of defects.
  32. 32. Int. J. Mol. Sci. 2013, 14 3211 Table 2. Optical characteristic for (TeO2)y[(PbO)x(B2O3)1−x]1−y glasses, y = 0.7% mol. PbO, x (mol %) 0.00 0.10 0.20 0.30 0.40 0.50 Dose (kGy) 0 5 10 20 25 0 5 10 20 25 0 5 10 20 25 0 5 10 20 25 0 5 10 20 25 0 5 10 20 25 Direct transition Eopt (eV) 3.22 3.13 2.82 2.76 2.74 3.22 2.97 2.82 2.72 2.62 3.18 2.98 2.54 2.62 2.66 3.16 2.94 2.66 2.68 2.76 3.16 3.04 2.74 2.78 2.80 3.10 3.00 2.80 2.82 2.92 Indirect transition Eopt (eV) 2.78 2.48 2.10 1.84 1.80 2.78 2.28 1.96 1.70 1.60 2.72 2.38 1.16 1.36 1.60 2.73 2.30 1.64 1.68 1.80 2.66 2.40 1.59 1.62 1.80 2.58 2.38 1.82 1.92 1.90 Urbach energy ΔE (eV) 0.27 0.36 0.65 0.68 0.73 0.27 0.43 0.81 1.06 1.09 0.28 0.38 1.58 1.17 0.94 0.25 0.41 1.23 1.00 0.79 0.30 0.35 1.17 1.00 0.87 0.28 0.34 0.87 0.70 0.70 With the increasing of irradiation dosage, the content of PbO ≤ 0.2% mol, the Ubach energy increases significantly, this suggests the increase in degree of disorder of the amorphous phase. As the content of PbO increases to be greater than 0.2% mol, the Ubach energy increases with 5 kGy and 10 kGy of irradiation dose and begins to decrease with irradiation dosage of 20 kGy and 25 kGy. It is believed that the increasing of irradiation creates displacements, electronic defects and/or breaks in the network bonds, which allow the structure to relax and fill the relative large interstices that exist in the interconnected network, causing expansion followed by compaction of the volume.
  33. 33. Int. J. Mol. Sci. 2013, 14 3212 3. Experimental Section The ternary (TeO2)y[(PbO)x(B2O3)1−x]1−y glass system (x = 0.0%–0.50% mol and y = 0.7% mol) were prepared using a conventional melt-quenching method [17]. All the glass samples arranged were homogenous, transparent and bubble free. The glasses were prepared by mixing together specific weights of Tellurium dioxide—TeO2 (Alfa Aesar 99.99%), Lead oxide, Litharge—PbO (99%) and Boron oxide—B2O3 (Alfa Aesar, 97.5%). Appropriate amounts of TeO2, PbO and B2O3 were weighed by using an electronic balance having an accuracy of 0.0001 g. The chemicals were then thoroughly mixed in an Agate pestle mortar for half an hour and poured into an Alumina crucible. The crucible was transferred to a furnace and heated at 950 °C for 2 h to aid the melting process. When the melting process was complete, the molten liquid was cast into a stainless steel cylindrical shape mold which had been preheated at 340 °C for 30 min. The produced glass samples were annealed at the temperature range 340 °C for 2 h, and then the furnace was turned off for cooling process reaching the atmospheric temperature. The glass samples were cut using Buhler ISOMET diamond cutter at a thickness of approximately 2 mm for the required measurements. The irradiation process had been conducted using 6°Co gamma rays (J.L. Sherperd & Associates, model 109-68# 3044) with the dose rate of 5.52 kGyh−1 on March 2004. The 6°Co radioisotope produced two gamma rays of energy 1.17 MeV and 1.33 MeV, often indicated in the machine as the average energy of 1.25 MeV, is the most widely used gamma source not only for research, but also for the food preservation, sterilization of medical equipment and pharmaceutical raw materials. The dose , where λ is the decay rate at the day of irradiation was calculated using decay equation constant, Dt is the dose rate at time t and D0 is the dose rate calibrated using Fricke dosimeter (Ferrous Sulphate). The half-life of 6°Co is 5.3 years. The irradiation has been conducted at the building 41, SINAGAMA at Malaysia Nuclear Agency. Raman spectra were measured using a Raman spectrometer (RSI 2001 B, Raman system, INC) equipped with a 532 nm solid-state diode green laser. Grams/32, version 6 software was used to analyze the spectra. All spectra were corrected for baseline; smoothed and Fourier Transformed (FT). The baseline correction utilized the multiple point level method in which the baseline is leveled at a value that is the average of the baseline points. A constant correction factor of 80% of the degree of smoothing parameter was used throughout the data collection. The Fourier smoothing was accomplished by the peak data, applying a triangular filter function at the specified cut-off point of 40% and then reverse Fourier transforming the data. Optical absorption measurements in the wavelength range of 190 to 800 nm with 0.1 nm internal spacing at slow scan speed were performed at room temperature using SHIMADZU spectrophotometer model UV-1650PC (absorption within ± 0.1 a.u. and wavelength within ± 2 cm−1). Phase identification of the samples will be determined by X-ray Powder Diffractometer, Philip X’Pert Pro Holland, using Cu-Kα monochromatized radiation (λ = 1.5418 mm). The operating generator tension is 40 kV while generator current is 30 mA. X-Ray diffraction patterns of powders were recorded at room temperature with a diffraction angle from 2θ = 5°–90° and at a rate of 0.01°/min. The XRD measurements were held using bulk dimension since the results gained did not shows any significant difference between bulk dimension and powder dimension.

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