Defence Science Journal, Volume 63, Issue 4 , July 2013, pp. 418-422
DOI : 10.144029/dsj.63.4866
© 2013, DESIDOC
Received 22 March 2013, Revised 16 June 2013, Online published 19 July 2013
Effect of Sintering Time on Dielectric and Piezoelectric Properties of Lanthanum Doped Pb(Ni1/3Sb2/3)-PbZrTiO3 Ferroelectric Ceramics
C.M. Lonkar* , D.K. Kharat#, H.H. Kumar,
Sahab Prasad, and K. Balasubramanian*
Armament Research & Development Establishment, Pune-411 021, India
# Defence Institute of Advanced Technology, Girinagar, Pune-411 025, India
Lead zirconate titanate (PZT) based materials can be employed for power harvesting applications since they can produce electrical output in response to ambient pressures, vibrations, movements etc. In the present studies, sintering time for composition Pb0.98La0.02(NiSb)0.05[(Zr0.52Ti0.48)0.995]0.95O3 (La-PNS-PZT) was optimised to achieve properties suitable for power harvesting. Composition was processed through mixed oxide route and sintered at 1270 °C for 20 min, 40 min, 60 min, 80min and 100 min. XRD pattern indicated the presence of both, ferroelectric tetragonal and ferroelectric rhombohedral perovskite phases. The optical photographs shown the uniform and dense microstructure for the samples sintered for 60 min, resulted into optimum piezoelectric charge coefficient, voltage coefficient, electromechanical coupling coefficient and figure of merit. Power harvesting capabilities in response to impact of stainless steel ball (8.25 gm) from 150 mm height were evaluated and compared with PZT type 5A. La-PNS-PZT produced batter electrical output (5.11 W, 71.13 µJ) across the matching load resistance of 4000 Ω and 2.08 W maximum power and 20.79 µJenergy by PZT type 5A disc across the matching load resistance of 1000 Ω.
Lead zirconate titanate (PZT) based ceramics attracted the technologists and researchers for sensor and actuator applications because of the excellent piezoelectric properties1,2. Mechanical quality factor (Qm), dielectric loss factor (tan δ), dielectric constant ( ), piezoelectric charge coefficient (d33), piezoelectric voltage coefficient (g33) are the important parameters which decide the suitability of the material for particular application. Materials with high Qm and low tan δ are suitable for ultrasonic and high frequency applications. Materials with higher and d33 are suitable for actuator applications like vibration and noise control, benders, optical positioning etc.3,4. Materials with higher g33 are useful for sensor applications5. Particularly, materials with higher d33, g33 and higher figure of merit (d33 x g33) are suitable for power harvesting applications since they offers higher power output6- 9.
Incorporating the suitable dopant and optimising the process parameters, desired properties can be obtained. Sintering parameters viz. atmosphere, temperature, time and heating rate have significant effect on microstructure and thus on electromechanical properties of the final product10,11. Dense microstructure with optimum grain size formed during sintering results in better dielectric and piezoelectric properties12.
In our earlier studies,effect of Zr/Ti ratio13 and lanthanum concentration14 on power harvesting properties of ferroelectric composition Pb(Ni1/3Sb2/3)-(ZrTi)O3were investigated. In the present study, ferroelectric composition Pb0.98La0.02(NiSb)0.05[(Zr0.52Ti0.48)0.995]0.95O314 was investigated for the effect of sintering time on the microstructure and electromechanical properties viz. Qm, kp, , d33, g33 and figure of merit. Study was also aimed towards analysing the suitability of this composition for power harvesting applications and its comparison with PZT type 5A.
Lanthanum doped Pb(Ni1/3Sb2/3)-(ZrTi)O3 ferroelectric composition Pb0.98La0.02(NiSb)0.05[(Zr0.52Ti0.48)0.995]0.95O3 [La-PNS-PZT] was synthesised by mixed oxide route using the oxides of elements.Raw material powders NiO (97%, Acros), Sb2O5 (99%, Loba Chemie), PbO (99.5%,Waldies Ltd., Kolkata), ZrO2 (99.37%, Loba Chemie) and TiO2 (98.5%, Travancore Titanium Products) were wet milled in pure water medium for 24 hours. Calcination was performed at 1060 °C followed by wet milling. Phase formation of the calcined powder was analysed from slow scanned X-ray diffraction pattern recorded from 42° to 58° by X-Ray diffractometer (Make -PANalytical, Model-X’pert pro). Powder was granuled using polyvinyl alcohol as a binder. Discs of diameter 29 mm and 1.7 mm thickness were compacted using double ended die punch machine (Make-GMT) by maintaining green density near to 4.8 g/cc. Samples were sintered in lead rich environment at 1270 °C for 20 min, 40 min, 60 min, 80 min and 100 min. They were lapped to 1.2 mm thickness and electroded with silver paste, followed by poling. Microstructure of polished and chemically etched samples was studied using optical microscope.
Capacitance (C at 1 kHz), resonance frequency(fr), anti resonance frequency (fa), Impedance (Zm) were measured at by Hioki Hi-tester (model 3532). Piezoelectric charge coefficient (d33) was measured by Berlincourt d33 meter (CPDT-3330). Dielectric constant ( ), voltage coefficient (g33) coupling factor (kp) and mechanical quality factor (Qm)were calculated using standard mathematical relations15,16.
Electrical output, across the load resistance ranging 15 Ω to 6000 Ω, in response to impact of stainless steel ball (8.25 gm) released from 150 mm height was measured. Voltage output was recorded by oscilloscope Make-Rigol, model-DS1064B. Full Width at Half Maximum (FWHM) was evaluated for positive pulse. Maximum power and energy output by positive pulse was calculated respectively, using Eqns. (1) and (2).
Composition shows perovskite phase formation reported in our earlier work14. Slow scanned X-ray diffraction pattern of calcined powder (Fig.1) shows presence of ferroelectric tetragonal (FT) and ferroelectric rhombohedral (FR) perovskite phases indicated by the splitting in the peak intensity at (200) plane in the triplets viz’ (002)T, (200)R and (200)T which was also confirmed by splitting in the peak intensity at (201) and (211) planes13,14,17 -21.
Figures 2(a)-2(e) represent the effect of sintering time on
Figure 1.X-ray diffraction pattern of calcined powder.
Figure 2.Microstructure of samples sintered at 1270 °C for (a) 20 min, (b) 40 min, (c) 60 min, (d) 80 min, and (e) 100 min.
microstructure of the samples sintered at 1270 ºC for 20 min, 40 min, 60 min, 80 min and 100 min, respectively. It was observed that grain size increased with the sintering time. Few grains were polygonal in shape and many ovals in case of the samples sintered for 20 min (Fig 2(a)). Large numbers of pores were also seen. For 40 min sintering time grain size remained same but porosity was reduced. For 60 min sintering time, the grain morphology was remarkably changed. Most of the grains were polygonal, indicating the complete grain growth, which was responsible for the compact microstructure. Narrow grain size distribution with reduced porosity was also noticed. For 80 min and 100 min sintering, grain morphology again changed. Some of the grains were spherical in shape. Broader grain size distribution was observed. Porosity largely increased at triple grain point may be due to the lead loss from the material sintered due to larger sintering time19. Loss of compactness in the microstructure was noticed. The average grain size was largely increased.
The average grain size measured by linear intercept method was about 5.99 µm, 6.04 µm, 6.85 µm, 8.76 µm and 10.19 µm of the samples sintered for 20 min, 40 min, 60 min, 80 min and 100 min , respectively.
Figure 3 shows the effect sintering time on electro-mechanical coupling factor (kp) and mechanical quality factor (Qm). As sintering time increased from 20 min to 60 min, kp increased and reached optimum value (=0.65). This was due increased domain wall motion which promotes the alignment of ferroelectric dipoles along the DC electric field applied during poling13,14,20. Increased domain wall motion reduces Qm and increases kp22. Minimum Qm was obtained for 60 min sintering time (=128). Further, increasing the sintering time to 100 min, kp decreased attributing to increased porosity may be due to volatility of PbO for larger sintering time (Figs. 2(c)-2(d)19) . Loss of lead changes the stoichiometry and creates the vacancies at the Pb site and reduces the domain wall movement resulting in increase in Qm and reduction in kp23,24.
Figure 4 shows the effect of sintering time on piezoelectric charge coefficient (d33) and on dielectric constant ( ). With increased sintering time from 20 min to 60 min, d33 increased
Figure 3.Effect of sintering time on kp and Qm.
Figure 4. Effect of sintering time on d33 and KT3.
Figure 5.Effect of sintering time on g33 and FoM.
from 281 x 10-12 C/N to 413 x 10-12 C/N, which was its optimum value. This was due to the reduced porosity and maximum polarisability obtained at this sintering time. Compactness in the microstructure increases the polarisation per unit volume13,14,19 resulting into optimum d33. Dielectric constant, increased from 808 to 1188 on increasing the sintering time from 20 to 60 min , which was its optimum value. Further, it decreased to 772 at 100 min sintering time. Dense microstructure with optimum grain size and narrow size distribution obtained for the samples sintered for 60 min was resulted into optimum piezoelectric and dielectric properties of the material11,23. On further increasing the sintering time, they were reduced may be due defects in a piezoelectric ceramic structure arose may be due to lead loss and thus increased porosity16.
Figure 5 shows the effect of sintering temperature on piezoelectric voltage coefficient (g33), and figure of merit (d33 xg33), a power generation ability of the piezoceramic. Voltage coefficient (g33) did not show linear relationship with the sintering time. It can be justified from the rise and fall in d33 and shown at Fig. 4 and the fact that mathematically, it is directly proportional to d33 and inversely proportional to As sintering time increased from 20 mins to 40 mins, extent of increase in d3 was less compared to
Figure 6.Electrical output at various load resistances.
Table 1.Electrical out put by La-PNS-PZT and PZT type 5A.
leading to reduction in g33. When sintering time increased from 80 min to 100 min, fall in d33 is lesser compared to fall in which yield higher g33. Similarly, trend was shown by FoM can be explained on the basis of behavior of d33 and g33. Optimum d33 and moderate value of g33 obtained in the samples sintered for 60 mins., resulted in optimum FoM.
In general, impedance is the measure of the opposition to the flow of current through a circuit when an alternating voltage is applied. When impedance of the piezo-element and the load is matched maximum power and thus energy can be obtained25-27. It was observed that the power and energy out put given by La-PNS-PZT was better than that of PZT type 5A (Fig. 6). The optimum values obtained are given at Table 1. As shown in Fig. 6, maximum power output of 5.11 W and energy output of 71.13 µJ was given by La-PNS-PZT across the matching load resistance of 4000 Ω and 2.08 W maximum power and 20.79 µJ energy output is given by PZT type 5A across matching1000 Ω load resistance.
Pb0.98La0.02(NiSb)0.05[(Zr0.52Ti0.48)0.995]0.95O3 ferroelectric composition was synthesised and sintered between 20 mins - 100 mins. XRD pattern indicated the polycrystalline microstructure along with presence of both, ferroelectric tetragonal and ferroelectric rhombohedral perovskite phases. Increased grain size was noticed with the sintering time as seen in optical photographs. Compact and uniform microstructure with optimum grain size (~6.85µm) was obtained for the samples sintered for 60 min which was resulted into optimum value of piezoelectric charge coefficient (d33=413 x 10-12 C/N), piezoelectric voltage coefficient (g33=39.3 x 10-3 V.m/N), electromechanical coupling coefficient kp(0.65), and figure of merit, FoM (d33 x g33=16.2 x 10-12 C.V.m/N2 ). It was observed that La-PNS-PZT generated higher electrical output compared to PZT type 5A. Optimum power 5.11 W and energy 71.13 µJ was generated by La-PNS- PZT while 2.08 W power and 20.79 µJ energy was generated by PZT type 5A. Comparatively, larger electrical output by La-PNS-PZT was attributed to better d33, g33 and figure of merit.
The authors express their sincere gratitude to Director, ARDE for providing necessary support to carry out the research work and permission to publish the work and to Director, NMRL for providing XRD facility. Thanks are also due to the Officers and Staff of PZT Centre of ARDE for their technical help for fabrication and characterisation of the material.
1. Haertling, G.H. Ferroelectric ceramics: History and technology. J. Am. Ceram. Soc., 1999, 82(4), 797–818.doi: 10.1111/j.1151-2916 [Full text via CrossRef]
2. Jaffe, B.; Cook, W.R. Jr. & Jaffe, H. Piezoelectric ceramic. Academic Press, New York, 1971, pp. 135-43.
3. Jordan, T.L. & Ounaies, Z. Piezoelectric ceramics characterisation. ICASE Report No. 2001-28, NASA/CR-2001-211225. 2001. http://dtic.mil/cgi-bin/GetTRDoc?AD=ADA395517 [Full text PDF]
4. Zhou, D.; Kamlah, M. & Munz, D. Effects of uniaxial prestress on the ferroelectric hysteretic response of soft PZT. J. Eur. Ceram., 2005, 25(4), 425-32.doi: 10.1016/j.jeurceramsoc.2004.01.016 [Full text via CrossRef]
5. Tressler, J.F.; Alkoy S. & Newnham, R. Piezoelectric sensors and sensor materials. J. Electroceram., 1998, 2(4), 257-71.doi: 10.1023/A:1009926623551 [Full text via CrossRef]
6. Kim, H.W.; Priya, S.; Unchino, K. & Newnham, R. Piezoelectric energy harvesting under high pre-stressed cyclic vibrations. J. Electroceram., 2005, 15(1), 27-34. doi: 10.1007/s10832-005-0897-z [Full text via CrossRef]
7. Mohammadi, F.; Khan, A. & Cass, R.B. Power generation from piezoelectric lead zirconate titanate fiber composites. In the Proceedings of the Material Research Society Symposium, Materials Research Society, 2002, 736, pp. D5.5.1-D5.5.6. doi: 10.1557/proc-736-d5.5 [Full text via CrossRef]
8. Green, C.; Mossi, K.M. & Bryant R.G. Scavenging energy from piezoelectric materials for wireless sensor applications. In the Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Orlando, USA, November 2005, pp.1-7. doi: 10.1115/imece2005-80426 [Full text via CrossRef]
9. Moulson, A.J. & Herbert, J.M. Electroceramics. Edn 2. John Wiley & Sons Ltd., England, 2003, 384p. doi: 10.1002/0470867965 [Full text via CrossRef]
10. Saha, S.K. & Agarwal, D.C. Composition fluctuations and their influence on the properties of lead zirconate titanate ceramics. Am.Ceram. Soc. Bull., 1992, 71(9), 1424-29.
11. Kungl, H. & Hoffmann M.J. Effects of sintering temperature on microstructure and high field strain of niobium-strontium doped morphotropic lead zirconate titanate. J. Appl. Phys., 2010 107(5), 054111 - 054111-11. doi: 10.1063/1.3294648 [Full text via CrossRef]
12. Zipparo, M.J.; Shung K.K. & Shrout, T.R. Piezoelectric properties of fine grain PZT materials. In the Proceedings of IEEE Ultrasonics Symposium, 1995, 1, pp. 601 - 604. doi: 10.1109/ultsym.1995.495648 [Full text via CrossRef]
13. Lonkar, C.M.; Kharat, D.K.; Kumar, H.H. & Prasad S. Effect of Zr/Ti ratio on piezoelectric properties of Pb(Ni1/3Sb2/3)O3–Pb(ZrTi)O3 ceramics. Ceram. Int., 2011, 37(8), 3509-14.doi: 10.1016/j.ceramint.2011.06.006 [Full text via CrossRef]
14. Lonkar, C.M.; Kharat, D.K.; Kumar, H.H.; Prasad S. & Balasubramanian, K. Effect of La on piezoelectric properties of Pb(Ni1/3Sb2/3)O3–Pb(ZrTi)O3 ferroelectricceramics. J. Mater. Sci. Mater. Electron., 2013, 24(1), 411-17. doi: 10.1007/s10854-012-0765-y [Full text via CrossRef]
15. Jordan, T.L. & Ounaies, Z. Piezoelectric ceramics characterisation. NASA Langley Research Centre. NASA Report No NASA/CR-2001-211225, 2001.
16. Bing, C.H.; Cheng, L.H. & Long, W. Promotion of piezoelectric properties of Lead Zirconate Titanate ceramics with (Zr,Ti) partially replaced by Nb2O5. Solid-State Electron., 2004, 48(12), 2293-97. doi: 10.1016/j.sse.2004.04.007 [Full text via CrossRef]
17. Yongjian, Yu.; Jinbiao, Tu & Singh, R.N. Phase Stability and ferroelectric properties of lead strontium zirconate titanate ceramics. J. Am. Ceram.,2001, 84(1),333-40.
18. Singh, V.; Kumar, H.H.; Kharat, D.K; Hait, S. & Kulkarni, M.P. Effect of lanthanum substitution on ferroelectric properties of niobium doped PZT ceramics. Mater. Lett., 2006, 60(24), 2964-68. doi: 10.1016/j.matlet.2006.02.041 [Full text via CrossRef]
19. Wang, M.C.; Haung, M.S.; Tze-Shoeng & Nan-Chung, Wu. Sintering and piezoelectric properties of Pb(Ni1/3Sb2/3)O3-PbZrO3-PbTiO3 ferroelectric ceramics. J. Mater. Sci., 2002, 37(3), 663-68.doi: 10.1023/A:1013746414023 [Full text via CrossRef]
20. Laishram, R.; Thakur, O.P.; Bhattacharya, D.K. & Harsh. Dielectric and piezoelectric properties of La Doped lead zinc niobate–lead zirconium titanate ceramics prepared from mechano-chemically activated powders. Mater. Sci. Eng. B, 2010, 172(2), 172-76. doi: 10.1016/j.mseb.2010.05.007 [Full text via CrossRef]
21. Boutarfafia, A. Investigations of co-existence region in lead zirconate titanate solid solutions: X-ray diffraction studies. Ceramic International, 2000, 26(6), 583-87.doi: 10.1016/S0272-8842(99)00099-1 [Full text via CrossRef]
22. Sangawar, S.R.; Praveenkumar, B.; Kumar, H.H. & Kharat. D.K., Effect of Fe and Fe-Ba substitution on the piezoelectric and dielectric properties of lead zirconate titanate ceramics. Mater. Sci. Eng. B, 2011,176(3), 242-45.doi: 10.1016/j.mseb.2010.12.003 [Full text via CrossRef]
23. Ming, Chen.; Xi, Yao. & Liangying, Zhang. Grain size dependence of dielectric and field–indiced strain properties of chemical prepared (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric ceramics. Ceramic International, 2002, 28(2), 201-207.doi: 10.1016/S0272-8842(01)00078-5 [Full text via CrossRef]
24. Zahi, S.; Bouaziz, R. & Abdessalem, N. A dielectric and piezoelectric properties of PbZrO3–PbTiO3–Pb(Ni1/3,Sb2/3)O3 ferroelectric ceramic system. Ceramic International., 2003, 29(1), 35–39. doi: 10.1016/S0272-8842(02)00086-X [Full text via CrossRef]
25. Umeda, M.; Nakamura, K. & Ueha, S. Energy storage characteristics of a piezogenerator using impact vibration.Jpn. J. App. Phys., 1997, 36(1), 3146–51. doi: 10.1143/JJAP.36.3146 [Full text via CrossRef]
Dr C M Lonkar
Dr C.M. Lonkar received PhD (Materials Science) from Defence Institute of Advanced Technolgy, Pune. He has published 11 research papers in peer-reviewed international journals, conferences & symposia. Presently, he is working in DRDO Centre for Piezoceramics and Devices at ARDE. His area of interest includes developing various grades of PZT based ferroelectric materials and devices..
Dr D K Kharat
Dr D.K. Kharat is Director, Armaments, at DRDO Headquarters, New Delhi. Prior to this, he was Associate Director at ARDE, Pune. He has a wide experience in the area of advanced composites, piezoceramics and nano materials for light weight launchers, under water sensors and hydrophones etc. He has published 120 research papers in national and international peer-reviewed journals, symposia and seminars.
Mr HH Kumar
Mr HH Kumar, Sc G obtained his MSc (Physics) from Pune University. He joined DRDO at NPOL, Kochi, in 1986 and presently heads DRDO Centre for Piezoceramics and Devices at ARDE. He has published 26 research papers in peer-reviewed journals and over 52 papers in conferences/seminars. He also possesses 3 Indian patents to his credit. He is presently working on nano materials and energy harvesting applications.
Dr Sahab Prasad
Dr Sahab Prasad(retd.) is PhD from IIT. He joined DRDO at INS Shivaji in June 1983 and subsequently transferred to Defence Institute of Advanced Technology, Pune. He was Head of the Materials Engineering Department and shouldered the responsibilities of Controller of Examinations. He has supervised several PG and PhD students and authored several research papers and technical reports.
Dr Balasubramanian K
Dr K. Balasubramanian, PhD (UK), CEng. (UK), MIMMM, FIoN (UK), Head of Materials Engineering Department, DIAT Pune, graduated with an honours degree in Chemical Technology specialising and Masters degree in Chemical Technology, specialising in Plastics Processing. He has a PhD in Materials Engineering from Loughborough University, UK. He has a total of 17 years of industrial and research experience in UK in the areas of polymer composites, plastics engineering, nanocomposites, ceramics and elastomers, coatings and advanced materials. He has filed 10 international/ national patents and has transferred technologies to automotive, aerospace and health care industries.