STUDIES ON THE GROWTH ASPECTS OF SEMI-ORGANIC AMMONIUM BORODILACTATE: A PROMISING NEW NLO CRYSTAL
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STUDIES ON THE GROWTH ASPECTS OF SEMI-ORGANIC AMMONIUM BORODILACTATE: A PROMISING NEW NLO CRYSTAL

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A new second order Non-linear optical semi organic single crystals of pure and Neodymium(Nd3+) doped Ammonium borodilactate (ABL) has been grown by aqueous solution slow evaporation technique (SET). ...

A new second order Non-linear optical semi organic single crystals of pure and Neodymium(Nd3+) doped Ammonium borodilactate (ABL) has been grown by aqueous solution slow evaporation technique (SET). In the present study, to improve the device characteristics of ABL crystals, metal dopant was incorporated into the pure crystals. The grown crystals are Non- Hygroscopic and good transparent in the visible region, the solubility of the grown crystals was found. The cell parameters were estimated by single crystal X-ray diffraction pattern. UV- Vis-NIR spectrum was recorded to study the optical transparency of the grown crystal. The pure and doped crystals were characterized by thermal studies. The mechanical behavior was studied by Vickers micro hardness test, dielectric and photoconductivity studies were also carried out for the pure and doped ABL crystals.

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STUDIES ON THE GROWTH ASPECTS OF SEMI-ORGANIC AMMONIUM BORODILACTATE: A PROMISING NEW NLO CRYSTAL STUDIES ON THE GROWTH ASPECTS OF SEMI-ORGANIC AMMONIUM BORODILACTATE: A PROMISING NEW NLO CRYSTAL Document Transcript

  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963 STUDIES ON THE GROWTH ASPECTS OF SEMI-ORGANIC AMMONIUM BORODILACTATE: A PROMISING NEW NLO CRYSTAL T. Panchanathan1, S. Nalini Jayanthi2, P.Sagayaraj3, K. Thamizharasan4 1 Department of Physics, Vellayan Chettiyar Hr. Sec. School, Chennai, India 2 Department of Physics, AIHT, Chennai, India 3 Department of Physics, Loyola College, Chennai, India 4 Department of Physics, Sir Theagaraya College, Chennai, IndiaABSTRACTA new second order Non-linear optical semi organic single crystals of pure and Neodymium(Nd3+) dopedAmmonium borodilactate (ABL) has been grown by aqueous solution slow evaporation technique (SET). In thepresent study, to improve the device characteristics of ABL crystals, metal dopant was incorporated into thepure crystals. The grown crystals are Non- Hygroscopic and good transparent in the visible region, thesolubility of the grown crystals was found. The cell parameters were estimated by single crystal X-raydiffraction pattern. UV- Vis-NIR spectrum was recorded to study the optical transparency of the grown crystal.The pure and doped crystals were characterized by thermal studies. The mechanical behavior was studied byVickers micro hardness test, dielectric and photoconductivity studies were also carried out for the pure anddoped ABL crystals.KEYWORDS: Solution growth, ABL, Micro Hardness, Dielectric, Photoconductivity. I. INTRODUCTIONNonlinear optical (NLO) materials which can generate highly efficient second harmonic blue-violetlight are great interest for various applications including optical, optical computing, opticalinformation processing, optical disk data storage, laser remote sensing, colour display, etc.[1,2]. Inthe recent past, there have been extensive efforts to develop new inorganic, organic and semi organicnonlinear optical (NLO) materials that posses several attractive properties such as high threshold,wide transparency range and high nonlinear coefficient which make them suitable for frequencydoubling [3, 4]. In view of this, there has been considerable interest in the synthesis of semi-organicmaterials having high mechanical and thermal stability. Semi-organic materials gain importance overinorganic materials because of their polarizability, wide transmission window and high damagethreshold [5]. The low temperature solution growth is an important technique because most of thesemi-organic non linear- optical crystals are being grown by this technique. Due to the inherentlimitation of these techniques, the size of the crystals grown by these methods is small.In the present investigation, we report the growth of Neodymium (Nd3+) doped ammoniumbordilactate (ABL) along with pure ABL crystals by slow evaporation technique. The grown crystalsare subjected to single crystal X-ray studies to estimate the crystal structure and space group. Thecontent of the dopant was determined by ICP analysis. UV- Vis-NIR, thermal, micro hardness,dielectric and photoconductivity studies were carried out from the grown pure and doped crystals. 298 Vol. 6, Issue 1, pp. 298-303
  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963 II. RELATED WORKSThe effect of sodium chloride, borax and boric acid of different concentrations on the growth rate ofammonium pentaborate octahydrate crystals (APBO) was measured by O. Sahin et.al. [6]. The effectof ammonium malate on the growth rate, structural, optical, thermal, mechanical, dielectric properties,crystalline perfection and second harmonic generation (SHG) efficiency of ammonium dihydrogenphosphate single crystals grown by the slow cooling method has been investigated by P. Rajesh et. al[7]. They found SHG efficiency was enhanced by the dopant. Ammonium acetate doped ammoniumdihydrogen phosphate single crystals have been grown by slow cooling along with bidirectional seedrotation method by P.Rajesh et.al.[8]III. EXPERIMENTAL PROCEDURE3.1 Crystal growthThe synthesis of ammonium borodilactate with chemical formula (NH4)+ (C6H8BO6)- was done bystoichiometric incorporation of ammonium carbonate, boric acid and lactic acid. Taken in the ratio1:2:4. ABL salt was synthesized according to their relation. (NH4)2 CO3 + H3BO3 + C6H6O3 → (NH4) + (C6H8 BO6)- 3+Nd doped ABL salt was also synthesized by adding 3 mole % of the dopant. To increase the purityof the crystal, recrystalization was carried out using doubled distilled water more than three times.3.2 Solubility StudiesThe solubility of pure and Nd3+ added ABL in double distilled water was measured at differenttemperature (30, 35, 40 and 45ºC) using a constant temperature bath of accuracy ± 0.01ºC. Thesolvent and an excess amount of ABL were added to a 250ml glass crystallizer. Experiments wererepeated for several times at each temperature. Similar experimental procedure was followed for Nd 3+at each temperature added ABL material. The solubility of pure and Nd 3+ added ABL in doubledistilled water was plotted as a function of temperature (Fig.1). Fig.2 shows the photograph of asgrown pure and doped crystals in a period of 45 days. Figure 1. Solubility curves of pure and Nd3+ Figure 2. Photograph of as grown (a) pure and (b) Nd 3+ doped ABL crystal doped ABL crystal crystal3.3 Characterization analysisThe grown crystals of pure and doped ABL have been subjected to single crystal X-ray diffractionstudies using ENRAF NONIUS CAD-4 single crystal X-ray diffractometer with Cu K(λ=1.541Ǻ)radiation. The structure of the grown ABL crystal was solved by direct method and retired by the fullmatrix-least – squares technique using ‘SHELXL’ program. The optical absorption spectrum wasrecorded for samples of about 4-6 mm thickness using a Varian carry 5E model dual beamspectrometer in the wave length range from 200 to 2000 nm. Single crystals of pure and doped ABLcrystals were subjected to thermo gravimetric analysis (TGA) and differential thermal analysis (DTA)simultaneously between 20˚C and 1400˚C in the nitrogen atmosphere at the heating rate of 10K/minusing STA 409˚C instrument. The electric constant was measured along the direction perpendicular to 299 Vol. 6, Issue 1, pp. 298-303
  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963the (010) face of low frequency at room temperature (28˚C). The single crystal (dimensions: thickness1.04mm and area 8.5 mm2) using a LCR meter (HIOKI3532-50 LCR HITESTER). In the frequencyrange 100Hz – 6MHz.IV. RESULT AND DISCUSSION4.1 Single crystal XRD analysisIt is observed that both pure and doped ABL single crystals belongs to orthorhombic system with anon-centrosymmetric space group C2221 with four molecules per unit cell (Z = 4). The latticeparameters values of ABL are measured as a= 9.3464 Ǻ, b=11.9628Ǻ, c=8.5674 Ǻ and cell volumeV= 957.9134 Ǻ3 and agree well with the reported values [9]. There slight variations in the latticeparameters and cell volume of the doped crystals. These variations may be due to the incorporation ofthe dopant in the ABL crystal lattice.4.2 Inductively Coupled Plasma AnalysisIn order to determine the weight percentage of dopant in doped ABL crystal, 10mg of fine powder ofthe doped crystal was dissolved in 100ml of triple distilled water. This prepared solution was taken forthe ICP analysis. The results obtained from ICP show that 2.16% of Nd3+ (216 µg/100ml) was presentin the solution. It is observed that the amount of dopant incorporated into the crystal lattice is belowits original concentration (3%) in the solution.4.3 UV-Vis-NIR spectral analysisUV-Vis-NIR spectrum was as shown in Fig.3. For optical application, especially for SHG, the crystalmust be transparent in the wavelength region of interest. The grown pure and Nd3+ doped ABL sampleshows high transparency (85%) in the range from 230 to 1300 nm and a sharp UV cut off wave lengthobserved at 230nm and 240nm for pure and doped ABL is due to - * transition in thismaterial.From the spectra, it is seen that doped ABL crystals have better lower cut-off wavelenghthsthan the pure crystals. The high transmission in the entire visible region on short cutoff wave lengthfacilities it to be a potential NLO material for second and third harmonic of Nd: YAG laser. Figure 3. Absorption spectrum of pure and Nd3+ doped ABL crystal4.4. TGA and DTA studiesFig.4 shows the resulting TGA and DTA traces of the pure and doped crystals. ABL was thermallystable around 204.3 ˚C and 218.2˚C respectively. The sharp weight loss of the material starts around204.3˚C.The DTA trace of ABL shows that a sharp endothermic matching with the decomposition of ABL.The Nd3+ doped ABL crystal shows the same features as that of pure ABL. 300 Vol. 6, Issue 1, pp. 298-303
  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963 Figure 4. TGA and DTA curves of pure ABL crystal4.5 Micro hardness studies crystalMicro hardness behaviour of the pure and doped crystals were tested by employing Vicker’s microhardness test on the (010) plane. Measurements were taken by varying the applied loads from 5 to 50g. Micro cracks were developed at higher loads, therefore the maximum applied load was restricted to50g only. The plot of variation of Vicker’s hardness number (HV) with applied load for (010) plane ofpure and doped ABL is shown in (Fig.5). From the plot, it is noted that the hardness number (H V) ofthe crystal decreases with increasing load. This type of behaviour wherein the hardness numberdecreases with increasing applied load is called normal indentation size effect (ISE). The work-hardening coefficient ‘n’ is calculated using log P versus log d graph. The value of work hardeningcoefficient, ‘n’ is found to be less than 2 for both pure and doped crystals. This further confirms thenormal ISE behaviour [10]. The hardness number HV has improved in the case of doped crystal. Figure 5. Variation of HV with load for pure and Nd3+ doped ABL4.6 Dielectric studiescrystalThe opposite parallel faces of the crystals were coated with high-grade silver paste placed between thetwo copper electrodes and thus a parallel plate capacitor was formed. The capacitance of the samplewas measured by varying the frequency from 100 to 6MHz. The dielectric constant (εr) was calculatedon capacitance, electrode area, and sample thickness. Fig.6 shows the plot of dielectric constant (ε r)verses applied frequency. The dielectric constant has high values in the lower frequency region andthen it decrease with the applied frequency. The dielectric constant has a high value of 6.4 at 100 Hzand decreases to 2.7 at 6 MHz. The dielectric constant of materials may be due to the contribution ofall the four polarizations, namely, space charge, dipolar, electronic and ionic polarization, whichdepend on the frequencies. The variation of dielectric loss with frequency is shown in Fig.7. Thedielectric loss has low value of 0.129 at high frequency (6MHz). The effect of inclusion of dopant isfound to decrease the dielectric constant. The behavior of doped crystal is very similar to that ofundoped crystal except having lower values of dielectric constant. The low value of dielectric loss athigh frequency for these samples suggest that samples possesses enhanced optical quality with lesserdefects and this parameter is of vital importance for NLO materials in their application [11]. 301 Vol. 6, Issue 1, pp. 298-303
  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963 Figure 7. Variation of dielectric loss with Figure 6. Variation of dielectric constant with frequency for pure and doped ABL single crystals frequency for pure and doped ABL single crystals4.7 Photoconductivity StudiesFig.8 and 9 shows the field dependence of dark and photo currents in doped and pure ABL crystals. Itis observed that both dark and photo currents of crystals increase linearly with the applied electricfield but the photo current of both pure and doped crystals is less than the dark current which istermed as negative photoconductivity. The loss of water molecules can also lead to decrease inconductivity. However, in the present case the contribution of water molecules to negativephotoconductivity is ruled out as the loss of water molecules for pure and doped ABL crystals beginsat 204.3˚C and 218.2˚C respectively. Hence, the negative photoconductivity in the present case isattributed to the reduction in the number of charge carriers or their life time, in the presence ofradiation [12]. Figure 8. Field dependent photoconductivity of Figure 9. Field dependent photoconductivity of doped ABL single crystals pure ABL single crystals V. CONCLUSIONS AND FUTURE WORKPure and Nd3+doped ABL crystals have been grown for pure and Neodymium (Nd3+) - added growthsolution by the slow evaporation method. The structure of the grown crystals confirmed with singlecrystal X- ray analysis, it is obvious that the pure and Nd3+ doped ABL crystals retain theorthorhombic structure and the calculated lattice parameter values are comparable with the reportedvalues of pure ABL. The presence of Nd3+ in ABL crystal was confirmed by inductively coupledplasma analysis. The transparency nature of the crystal in the visible and infrared region that form theabsorption spectrum confirms the NLO property of the crystal. From Vickers microhardness studies,the VHN value of this pure ABL crystal is less than that of the doped crystal, and revealed that themicro hardness number decreases linearly with increasing load for both pure and doped. ABL crystalswere calculated and found to be less than two for both pure and doped crystals of ABL weremeasured. At low frequency range both dielectric constant and dielectric loss are found to decrease 302 Vol. 6, Issue 1, pp. 298-303
  • International Journal of Advances in Engineering & Technology, Mar. 2013.©IJAET ISSN: 2231-1963with the increase of frequency. In general, ABL shows higher dielectric constant and dielectric lossthan its doped system. The crystals with low dielectric constant lead to minimum losses as they haveless number of dipoles per unit volume and hence doped crystals will be more useful for high speedelectro optic modulations as compared to pure crystals. Photoconductivity studies of both pure anddoped ABL crystals. It is clearly observed that both pure and doped crystals exhibit negativephotoconductivity.Basic studies shows Pure and Neodymium (Nd3+) added crystals are suitable for high speed electrooptic modulation techniques. Further studies on Second Harmonic Generation, Photo Luminescenceanalysis, DC conductivity measurements can lead to some concrete conclusion regarding the use ofthis crystal in NLO devices.REFERENCES [1]. H.S. Nalwa, Seizo Miyata, Nonlinear Optics Molecules and Polymers,CRC Press NewYork, 1997. [2]. P.N. Prasad, D.J. Williams, Introduction to Nonlinear Optical Effects In organic Moleculeas and Polymers, John Wiley and Sons Inc. New York, USA,1991. [3]. N. Vijayan, R. Ramesh Babu, R. Gopalakrishnan, P. Ramasamy,J.Cryst.Growth 267 (2004). [4]. R. Mohan Kumar, D. Rajan Babu, D. Jayaraman, R. Jayavel, K. Kitamura, J.Cryst. Growth, 275 (2005) 1935. [5]. R. Bairava Ganesh, V. Kannan, K. Meera, N.P. Rajesh,P.Ramasamy, J.Cryst.Growth, 282 (2005) 429. [6]. Ö. Şahin, M. Özdemir, N. Genli, Journal of Crystal Growth, 270 (2004) 223-231. [7]. P. Rajesh,P. Ramasamy, G. Bhagavannarayana, Journal of Crystal Growth, 311 (2009) 4069-4075. [8]. P. Rajesh, K. Boopathi, P. Ramasamy, Journal of Crystal Growth, 311 (2011) 751-756. [9]. K.Thamizharasan, S.Xavier Jesuraja, Francis P.Xavier, P. Sagayaraj, J. Cryst. Growth, 218 (2000) 323. [10]. S. Dhanuskodi, P.A. Angeli Mary, J. Cryst. Growth, 253 (2003) 424. [11]. M.D. Shahabuddin Khan, G. Prasad. G.S. Kumar, Cryst. Res. Tech, 27 (1992) K28. [12]. V.N. Joshi, Photoconductivity, Marcel Dekker, New York, 1990.AUTHORST. Panchanathan received his B.Sc., M.Sc., and M.Phil. in Physic from Madras University. Heis currently doing his Ph.D., in Bharathiyar University, Coimbatore. He has 2 years of teachingexperience in college and 20 years of teaching experience in school. He published more than 4research papers in various National and International conferences.S. Nalini Jayanthi received her B.Sc., Degree in Physics (2000), M.Sc., Degree in Physics(2002), M.Phil., Degree in Physics (2003) from Bharathidasan University. She is currentlyworking as Assistant Professor in Anand Institute of Higher Technology, Chennai-603 103. Shehas published more than 6 research papers in various National and International Conferences.Her research interest includes Ultrasonics and Spectroscopy.P. Sagayaraj received his Ph.D degree from Madras University (1996). He have 30 years ofteaching experience. Now he is working as Dean of Reasearch in Loyola College, Chennai. Hepublished more than 94 international research papers and 25 national research papers. Hepublished more than 180 national and international conference papers. He completed tworesearch projects and two other projects are undergoing. He guided 50 M.Phil., students and 21Ph.D., research scholars/ Currently he is guiding 2 M.Phil., students and 8 Ph.D., researchscholars.K. Thamizharasan received his Ph.D., degree from Madras University (2000). He has 30years of teaching experience. Now, he is working as Associate professor and Head of Physicsdepartment in Sir Theagaraya College, Chennai-21. He published more than 20 papers inNation/International conferences. He published nearly 25 papers in international Journals. Heguided nearly 15 M. Phil., students and guiding 5 Ph.D., scholars. His area of Interest is Crystalgrowth. 303 Vol. 6, Issue 1, pp. 298-303