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Impedance spectroscopic studies on pani ceo2 composites
 

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    Impedance spectroscopic studies on pani ceo2 composites Impedance spectroscopic studies on pani ceo2 composites Document Transcript

    • INTERNATIONAL Electrical EngineeringELECTRICAL ENGINEERING International Journal of JOURNAL OF and Technology (IJEET), ISSN 0976 – 6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME & TECHNOLOGY (IJEET)ISSN 0976 – 6545(Print)ISSN 0976 – 6553(Online)Volume 4, Issue 1, January- February (2013), pp.01-08 IJEET© IAEME: www.iaeme.com/ijeet.aspJournal Impact Factor (2012): 3.2031 (Calculated by GISI) ©IAEMEwww.jifactor.com IMPEDANCE SPECTROSCOPIC STUDIES ON PANI/CEO2 COMPOSITES Khened B.S1, Machappa.T2, M.V.N. Ambika Prasad3, Sasikala. M.4* 1 Department of Electrical and Electronics Engineering, Ballari Institute of Technology & Management, Bellary-583 104, Karnataka, India 2 Department of Physics, Ballari Institute of Technology & Management, Bellary-583 104, Karnataka, India 3 Department of Material Science, Gulbarga University, Gulbarga-585 106, Karnataka, India 4 Department of Electrical and Electronics Engineering, C. V. R. College of Engineering, Vastunagar, Ibrahimpatnam-501 510, R R Dist., Andhra Pradesh, India Email: bskhened@yahoo.co.in, machappat@rediffmail.com, Prasad1_Amb@rediffmail.com, sasi_mun@rediffmail.com Author for correspondence: sasi_mun@rediffmail.com ABSTRACT Polyaniline-Cerium oxide composites were prepared by in situ polymerization method with different weight percentage of cerium oxide in Polyaniline. The composites were characterized by infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The frequency dependent conductivity and dielectric behavior of these composites have been studied in the frequency range of 50 Hz to 5 MHz. The variation of σac was small in all composites in the frequency range of 50Hz to 10 KHz. Large variations in conductivity were observed in the frequency range of 10 KHz to 5 MHz. This multiphase variation may be due to lattice polarization around a charge in localized state and due to variation of distribution of CeO2 in polymer matrix. Dielectric constant and dielectric loss and real part of impedance were found to decrease with increase in frequency. The position of peak of Z shifts towards higher frequency side with decrease in weight percent of cerium oxide in polyaniline. Key words: polyaniline, Cerium oxide, impedance spectroscopy, a.c.conductivity 1
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME1. INTRODUCTION Conducting polymers are being used commonly in scientific and industrial studiesand in various applications such as sensors, rechargeable batteries, diodes, transistors andmicroelectronic devices [1-7]. These materials provide huge scope for tuning their electricalconductivity [8-9]. Among conjugated polymers polyaniline deserves special attentionbecause of its good environmental stability, easy processability, moderate electricalconductivity, and rich physics in charge transport mechanism [10]. The electrical and dielectric properties of these materials are altered when they aretaken in the composite form. The composite materials consist of conducting filler material inthe polymer matrix and provide satisfactory mechanical and electrical properties. Conductingpolymer inorganic composites have been in the extensive research for the past few years [11-14]. Synthesis of many polyaniline—inorganic particle composites have been reported [15-21] and applications of such composites as electro—rheological fluids [22] and in highdensity information storage devices [23] have been studied. The conductivity of these composites depends on number of factors such as theconcentration of conducting fillers, their shape, size, orientation and interfacial interactionbetween filler molecules and host matrix [24-25]. Conduction by polarons and bipolarons isthe dominant mechanism of charge transport in polymers. New models are developed toexplain the mechanism of charge transport in these materials [26-27]. Kivelson was the firstto use the inter-soliton hopping model [28]. Other models like electron hopping and dipolarrelaxation have been used to explain the dielectric data of PANI salts. But it seems that nodefinite theory exists to explain the origin of electric conduction or the reported near metalinsulator transition occurring in conducting PANI [29]. In the present paper, the authorsreport the preparation of Polyaniline / Cerium oxide composites, its characterization throughFTIR spectra, scanning electron microscope (SEM), transport properties such as acconductivity, dielectric behavior, dielectric loss and variation of impedance with frequency.2. EXPERIMENTAL All chemicals used are analytical grade (AR) and were used as received. Themonomer aniline was doubly distilled prior to use. Synthesis of polyaniline /CeO2 compositeshas been carried out by single step in situ polymerization technique. Aniline of 0.1mol wasdissolved in 1M of hydrochloric acid to form aniline hydrochloride. Finely grinded powder ofCerium oxide (CeO2) is added in the weight percent of10, 20, 30, 40 and 50 to the abovesolution with vigorous stirring to keep Cerium oxide suspended in the solution. To thisreaction mixture, 0.1M of oxidizing agent ammonium persulphate [(NH4)2S2O8] in 1M ofhydrochloric acid was added slowly with continuous stirring for 4–8 hours at 0–5° C topolymerize. The precipitated powder was recovered, vacuum filtered and washed with deionized water. Finally, the resultant precipitate was dried in an oven for 24 hours to achieveconstant weight. In this way, five different composites of polyaniline/CeO2 with differentweight of (10, 20, 30, 40 & 50) in PANI have been synthesized. The pellets of 10 mmdiameter are formed with thickness varying up to 2 mm by applying pressure of 10 ton in aUTM-40 machine (40 Ton Universal testing machine). For conductivity measurement, thepellets are coated with silver paste on either side of the surfaces. 2
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME The characterization studies are employed on all the above synthesizedpolyaniline/CeO2 composites to confirm the presence of CeO2 in PANI. Fourier transforminfrared(FTIR) spectra was recorded on a JASCO FT/IR 5300 spectrophotometer in KBrmedium and the powder morphology of pellets was investigated with scanning electronmicrographs on Phillips XL 30 ESEM The frequency dependent AC conductivity studies on polyaniline / CeO2composites are made using Hioki impedance analyzer (model 3532-50 programmable LCRmeter) in the frequency range 50 Hz to 5 MHz at room temperature.3. RESULTS AND DISCUSSIONS 3.1. FTIR Figure 1(a) shows the IR spectra of Polyaniline where the transmittance is plottedas a function of wave number (cm-1). Careful analysis of the spectra reveals the presence ofintensity peaks 1302 cm-1 for C-N stretching + C-H bending,1240cm-1 C-N stretching + C-Cstretching ,812 cm-1 Deformational C-H (out of plane) of 1-4 disubstituted aromatic ring (Benzoid).The spectra shows the presence intense bands at 1568 cm-1, 1481 cm-1 which maybe attributed to Qunoid and Benzoid rings respectively. Figure 1 (a) IR spectrum of Polyaniline (b) IR spectrum of composite The IR spectra of polyaniline – CeO2 composite (40 wt % of CeO2 in PANI) isshown in Figure 1 (b). The prominent peaks that are observed in polyaniline – CeO2composite are 2918 cm-1, 2361 cm-1, 1560 cm-1, 1471 cm-1, 1298 cm-1, 1240cm-1,1107 cm-1 ,798 cm-1, 652 cm-1,and 509 cm-1.By careful observation of IR the characteristic stretchingfrequencies are considerably shifted towards higher frequency side. The data suggest that,there is a Vander walls kind of interaction between the polymer chain and CeO2. 3
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME3.2. SEM SEM micrograph of polyaniline is as shown in figure 2(a). It can be clearly seenthat the micrograph of polyaniline is smooth and homogeneous. Since Hydrochloric acid isused as protonic acid in the preparation of polyaniline, the presence of microcrystallinestructure can be seen that is not homogeneously distributed throughout. The contrast in theimage is a result of differences in scattering from different areas of the surface as a result ofgeometrical differences. Figure 2(b) shows the SEM micrograph of pure CeO2. High magnification SEMimage reveals that CeO2 particles are uniformly distributed with definite shape and size andconfirms the crystallanity of the oxide.The SEM micrograph of polyaniline – CeO2 compositewith 40 wt % of CeO2 in polyaniline is shown in figure 2(c). High magnification SEM imagereveals the presence of CeO2 particles uniformly distributed throughout the compositesample. A small variation in the particle dimensions of CeO2 so dispersed in polyaniline hasbeen observed. Fibrillar morphology is observed in the composite. The contrast in the imageis due to the difference in scattering from different surface areas as a result of geometricaldifferences between polyaniline and CeO2.Figure 2.SEM of (a) PANi, (b)CeO2, (c)composite 3.3. A.C. conductivity Using the values of the equivalent parallel capacitance(Cp), dissipation factor( D),and parallel equivalent resistance(Rp), recorded by the LCR meter at a different frequencies ,ac conductivity (σac), dielectric constant (ε) and dielectric loss (tan δ) parameters have beencalculated. Figure 3(a), shows the variation of ac conductivity as a function of frequency ofpolyaniline/CeO2 composites. It is observed that variation of σac is small in all compositesin the frequency range of 50Hz to 10 KHz. Large variations in conductivity is observed inthe frequency range of 10 KHz to 5 MHz. This multiphase variation may be due to latticepolarization around a charge in localized state and due to the variation of distribution of CeO2in polymer matrix. Apart from temperature and frequency, percentage of crystallinity, degreeof protonation, crystalline domain size and order in crystalline and amorphous regions have arelation with the delocalization length. Figure (3b) shows the variation of σac as a function of wt% of CeO2 in polyanilineat three frequencies (10, 100 & 1000 kHz) at room temperature. It is observed that acconductivity decreases in 10, 20, 30 & 50 wt % of CeO2 in polyaniline and increases in 40 wt% of CeO2 in polyaniline. The decrease in conductivity with increase in wt% may be due toan increase in the disorderliness of the composites. CeO2 particles could possibly induceconformational changes in polyaniline, leading to a reduction in the order and a consequentreduction in the delocalization length, which is reflected with decrease in conductivity [32]. 4
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEMEThe increase in conductivity in 40 wt% of CeO2 in polyaniline may be due to the extendedchain length of polyaniline which facilitate the polarization of charge carriers and variation ofdistribution CeO2 particles which may support for more number of charge carriers to polarizebetween favorable localized sites causing increase in conductivity. -2 1.0x10 0.0050 10 20 30 40 50 -3 0.0045 b 10 wt% 9.0x10 10 KHz 0.0040 100KHz 1000KHz 20 wt% -3 8.0x10 0.0035 30 wt% 40 wt% conductivity(s-cm ) 0.0030 -1 -3 7.0x10 0.0025 50 wt% c o n d u c tiv ity (s /c m ) -3 0.0020 6.0x10 0.0015 -3 0.0010 5.0x10 0.0005 -3 4.0x10 0.0000 10 20 30 40 50 wt% of CeO2 in Polyaniline -3 3.0x10 a -3 2.0x10 -3 1.0x10 0.0 100 1000 10000 100000 1000000 frequency(Hz) Figure 3(a) ac conductivity as a function of frequency (b) variation of σac at three frequencies. 3.4 Dielectric Behaviour Figure 4 shows the variation of ε as a function of frequency for different wt% ofpolyaniline/ CeO2 composites. It is observed that, the dielectric constant is high in 20 wt %compared to 10, 30, 40 & 50 wt% at low frequency .In all the samples, dielectric constantdecreases with increase in applied frequency. The dielectric constant value for differentcomposites is ranging from 8.9 x 105 to 3.26 x 106 at 50 Hz which decreases to value rangingfrom 707 to1843 at 5 MHz. Such large values of real permittivity is not unusual, which arerelated to effect of electrode polarization and space charge polarization [30]. The observedbehavior may be due to nearly a Debye-type single relaxation mechanism taking place inthese materials. All these results go in accordance with the conductivity behavior. 6 3.5x10 10 wt% 10 10 wt% 20 wt% 20 wt% 6 3.0x10 30 wt% 30 wt% 40 wt% 40 wt% 50 wt% 50 wt% 6 8 2.5x10 6 2.0x10 6 T nd lta a e e 6 1.5x10 6 4 1.0x10 5 5.0x10 2 0.0 -5.0x10 5 0 100 1000 10000 100000 1000000 100 1000 10000 100000 1000000 Frequency(Hz) Frequency(Hz) Figure 4. Variation of permittivity Figure 5 . variation of dielectric loss 5
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME3.5. Dielectric loss The variation of dielectric loss as a function of frequency for different wt% ofpolyaniline / CeO2 composites is represented in figure 5. The loss tangent value is rangingbetween 4.06 to 9.99 at 50 Hz and decreases with increase in frequency. At 5 MHz its valueis ranging between0.68 to 1.89.Similar values which increase with protonation have beenreported earlier [31] . The observed behavior is in accordance with the conductivity anddielectric constant results in these composites. High dissipation loss at low frequency in allthe composites may be due to DC conduction losses. 3 4.0x10 900 3 10wt% 800 10wt% 3.5x10 20wt% 20wt% 30wt% 700 30wt% 3 3.0x10 40w t% 40w t% 50w t% 600 50w t% 3 2.5x10 500 z"(Ohms) 3 2.0x10 z 400 3 1.5x10 300 3 1.0x10 200 2 5.0x10 100 0.0 0 1 2 3 4 5 6 7 1 2 3 4 5 6 7 10 10 10 10 10 10 10 10 10 10 10 10 10 10 Frequency(Hz) Frequency (Hz) 900 800 Z(ohms) 700 600 500 400 300 10 % 200 20 % 30 % 100 40 % 50 % 0 0.0 5.0x102 1.0x103 1.5x103 2.0x103 2.5x103 3.0x103 3.5x103 4.0x103 Z(ohms)Figure 6 (a)Variation of Z with frequency (b) Variation of Z with frequency (c)Nyquist plot Figure 6 (a) shows the variation of real part of impedance with frequency inpolyaniline / CeO2 composites. At lower frequencies the value of Z increases with increasein weight percent of cerium oxide in polyaniline and with increase in frequency, the value ofZ is found to decrease in all samples. The variation of imaginary part of impedance withfrequency in polyaniline / CeO2 composites is shown in figure 6(b)..The position of peak ofZ shifts towards higher frequency side with decrease in weight percent of cerium oxide in 6
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEMEpolyaniline. The width of the peak points towards the possibility of distribution of relaxationtimes(33) and the relaxation time τ can be determined from the position of the peak(τ=1/ωmax). Figure 6(c) shows Nyquist (Z vs. Z) plots for polyaniline / CeO2 composites.The semi circles observed in the plot are due to grains, grain boundaries and grain- electrodeeffect. With increase in weight percent of cerium oxide in polyaniline, the number of semi-circles increases up to three. Each semi circle can be represented by a resistance and acapacitor connected in parallel. The intercept on real axis represents the bulk resistance of thesample.4. CONCLUSIONS Polyaniline-cerium oxide composites with different weight percentage of ceriumoxide in Polyaniline were prepared by in situ polymerization method. The formations of thecomposites were characterized by infrared spectroscopy, x-ray diffraction and scanningelectron microscope techniques. The frequency dependent conductivity and dielectricbehavior of the composites have been studied in the frequency range of 50 Hz to 5 MHz. Inthe frequency range of 50Hz to 10 KHz, variations in a.c. conductivity was small in all thesamples. Large variations in conductivity were observed in the frequency range of 10 KHz to5 MHz. This multiphase variation may be due to lattice polarization around a charge inlocalized state and due to variation of distribution of CeO2 in polymer matrix. With increasein frequency, dielectric constant was found to decrease. This behavior may be due to nearly aDebye-type single relaxation mechanism. High dissipation loss observed at low frequencymay be due to D.C. conduction losses. With increase in frequency the dielectric loss and Zwere found to decrease. With decrease in weight percent of cerium oxide in polyaniline, theposition of peak of Z shifts towards higher frequency side.REFERENCES1 Mac Diarmid,A.G.;Yang,L.S.;Hunng,W.S.;Humphry,B.D. Synth Met 1987,18,393.2. Mizumoto,M.;Namba,M;Nishimura,S.;Miyadera,H.;Koseki,M.;Kobayashi,Y.Synth Met1989, 28, 639.3. Sukeerthi,S.; Contractor,A.Q Indian J Chem Sect A 1994,33,365.4. Ogura ,K.; Saino ,T.; Nakayama , M.;Shiigi , H. J Mater Chem 1997, 7, 2363.5. Ogura ,K.; Shiigi, H.; Nakayama , M.;Fujii, A. Electrochem Soc 1998, 145, 3351.6.Patil, R.C.;Ahmed, S.M.; Shiigi, H; Nakayama , M.; Ogura ,K.J Polym Sci Part A;PolymChem1999,37,4596.7. Paul, W.;Ricco, A.J.;Wrighton, M.S. J Phys Chem 1985,89,1441.8. MacDiarmid A G and Epstein A J. Frontiers of polymers and advanced materials (NewYork: Plenum Press) 1994. 2519. Wessling B Synth. Met1999. 102. 139610. J. Joo, S.M.Long, J.P.Pouget,E.J.Oh, A.J.MacDiarmid, A.J.Epstein.Phys.Rev.B.1998.57.9567.11. C. G. We, D. C. Degroot, H. O. Marcy, J. L. Schindler, C. R. Kannewurf, Y. J. Liu, W.Hirpo, and M. G. Kanatzidis, Chem. Mater.1996, 8, 1992 .12. T. A. Kerr, H. Wu, and L. F. Nazar, Chem. Mater, 1996, 8, 2005.13. E. R. Hitzky, P. Aranda, B. Casal, and C. J. Galvan, Adv. Matter.1995,7,180. 7
    • International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 1, January- February (2013), © IAEME14. W. J. Bae, K. H. Kim, W. H. Jo, and Y. H. Park, Macromolecules, 2004,37, 9850.15. P. Somani, B. B. Kale, and D. P. Amalnerkar, Synth. Met.1999, 106, 53.16. F. Fusalba and D. J. Belangar, Mater. Res., 1999, 14, 1805.17. M. L. Gautu and P. J. G. Romero, Solid state Chem.1999, 147, 601.18. I. Krivka, J. Prokes, E. Tobolkova, and J. Stejskal, J. Mater. Chem.1999, 10, 2425.19. W. Jia, E. Segal, D. Kornemandel, Y. Lamhot, M. Norkis, and A. Siegmann, Synth.Met.2002,128, 115.20. S. J. Su and N. Kuramoto, Synth. Met.2000, 114, 147.21. S. Wang, Z. Tan, Y. Li, L. Sun, and T. Zhang, Thermochim. Acta, 2006, 441, 191.22. J. W. Kim, S. G. Kim, H. J. Choi, and M. S. Jhon, Macromol. Rapid Commun.1999, 20,450.23. C.Wang, Y. H. Zang, J. B. Gao, W. J. Zang, Y. F. Lu, Y. B. Bai, Y. J. Li, L. J. Li, andY.Wei, Chem. J. Chin. Univ.1999,20, 1491.24. Kryszewaski M,Synth. Met.1991, 45, 28925. Brosseau C, Queffelec P and Talbot P, J. Appl. Phys.2001, 89, 453226 Kaiser A B, Subramanium C K, Gilberd P W and Wessling B, Synth. Met.,1995,69, 197.27 Kaiser A B, Liu C J, Gilberd P W, Kemp N T, Wessling B, Partridge A C, Smith W T andShapiro J C, Synth. Met., 1997, 84, 699.28. Kivelson, S., Phys. Rev. B, 1982, 25, 3798.29.H.M.El Ghanem,H.Attar, H.Sayid Ahmed,S.Abduljawad, I.J. Pol.Mater.,2006,55, 663.30. H.M. Kim, C.Y. Lee, J. Joo, Korean Phys. Soc.2000, 36, 371.31. H.H.S. Javadi, K.R. Cromack, A.G. MacDiarmid, A.J. Epstein, Phys. Rev. B,1989, 39,3579.32. T.Machappa, M.V.N.Ambika Prasad, Ferroelectrics.2009, 39, 2 71.33.Subrat K Barik, R.N.P.Choudhary, A.K.Singh,Adv. Mat.Lett.2011,2, 419.34. G. Bhavani and S. Ganesan, “Synthesis Of Nano Ytrrium Oxide Phosphors By SimpleMethods And Their Morphological Studies” International Journal of Physics (IJP), Volume1,Issue1, 2012, pp. 32 - 40, Published by IAEME.35. Attel manjunath and Dr. D V Girish, “Effect Of Short Glass Fiber Reinforcement OnCharacteristics Of Polymer Matrix (Polycarbonate) - An Experimental Study”International Journal of Mechanical Engineering & Technology (IJMET), Volume1, Issue1,2010, pp. 124 - 133, Published by IAEME.36. S.Shankar, Dr.H.K.Shivanand and Santhosh Kumar.S, “Experimental Evaluation ofFlexural Properties of Polymer Matrix Composites” International Journal of MechanicalEngineering & Technology (IJMET), Volume3, Issue3, 2012, pp. 504 - 510, Published byIAEME. 8