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Electrocaloric Properties of (Pb,La)(Zr,Ti)O3 and BaTiO3 Ceramics

Written By

Hiroshi Maiwa

Submitted: December 9th, 2014 Reviewed: November 2nd, 2015 Published: November 11th, 2015

DOI: 10.5772/61926

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Abstract

The electrocaloric properties of (Pb,La)(Zr,Ti)O3 (PLZT) and BaTiO3 ceramics were investigated by the indirect estimation and direct measurement of temperature–electric field (T–E) hysteresis loops. The measured T-E loops showed a similar shape to strain–electric field (s–E) loops. The adiabatic temperature change ∆T due to electrocaloric effects was estimated from the polarization change of these samples. ∆Ts of 0.58 and 0.36 K were estimated for the (Pb,La)(Zr,Ti)O3 (PLZT)(9.1/65/35) ceramics and BaTiO3 ceramics sintered at 1400°C, respectively. The measured temperature changes ∆Ts in these samples upon the release of the electric field from 30 kV/cm to zero were 0.26 and 0.29 K, respectively.

Keywords

  • Electrocaloric effect
  • PLZT
  • BaTiO3
  • refrigerator

1. Introduction

The electrocaloric effect(ECE) is a phenomenon in which a material shows a reversible temperature change under an applied electric field [1, 2]. There has been some problem in the conventional refrigerator. Since the conventional refrigerator operates by using a compressor, vibration generation is inevitable. The conventional refrigerator uses Freon as refrigerants; however, Freon acts implicated in ozone depletion. The other disadvantage includes the difficulty in down-scaling. Thermoelectric cooling using the Peltier device has been considered as a solid state cooling device; however, low efficiency has been a hindrance to the wide applications. In addition, common thermoelectric materials used as semi-conductors include bismuth telluride, lead telluride, silicon germanium, and bismuth-antimony alloys. Some of them are toxic. Although new high-performance materials for thermoelectric cooling are being actively researched, the good results have not been obtained. From the viewpoint of the refrigerator innovation, new refrigerators based on the new mechanism are expected. ECE is considered to be one of the new cooling mechanisms [1, 3, 4]. By using ECE, the application to compact a high energy-effective, inexpensive, and safe refrigerator would be considered, as shown in Fig. 1. ECE was discovered in 1930 by Kobeko and Kurchakov [5]. The research activities on ECE have been not active until the year 2006. In that year, “giant” temperature change in Pb(Zr,TiO3 (PZT) thin films were activated at one sweep [6]. Figure 2 shows the relation between the numbers of the published papers and the published year. After 2006, the number of papers on ECE increased rapidly [7-17]. The operation principle of the refrigerator using ECE is shown in Fig. 3. By applying the electric field, the ferroelectrics are heated by ECE. This process corresponds to the compression process in the compressor type refrigerator. By removing the electric field, the directions of the polarization become random. This process is endothermic, corresponds to the expansion process in the compressor type refrigerator, and the object is cooled. The electrocaloric effect (ECE) is a phenomenon in which a material shows a reversible temperature change under an applied electric field. In order to create ECE cooling devices, materials with large ECEs are required. The electrocaloric temperature change ∆T due to applied ∆E is calculated from the following equation [6]:

ΔT=TρCE1E2(PT)EdEE1

Here, C and ρ are the specific heat and density, respectively. Based on equation (1), a large (∂P/∂T)E (i.e., a large polarization change with temperature under high electric field) is desirable. With respect to achieving large (∂P/∂T)E, relaxor materials have recently attracted attention [1, 3, 4]. For direct measurement of the ∆T, there are some difficulties. Most temperature changes are less than 1K. And heat dissipation from ferroelectric materials through electrode, wire, and/or the supporting jig for field application occurs. Most probably due to these difficulties, the reports on the direct measurement of ∆T are limited thus far [13, 17, 18]. In this study, the electrocaloric temperature change, ∆T, due to applied ∆E, of the PLZT ceramics and BaTiO3 ceramics is estimated and directly measured. Concerning direct measurement of temperature–electric field (T–E) hysteresis loops, the reports have been limited. Detailed measurements of various measurements are required to clarify the insights of the ECE [4, 18, 19, 20].

Figure 1.

The merits of ECE cooler.

Figure 2.

Year to year comparison of the numbers of papers on ECE, 1958-2014.

Figure 3.

The operation mechanism of the ECE cooler.

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2. Experimental procedure

PLZT(7/65/35) and PLZT(9.1/65/35) ceramics and BaTiO3 ceramics were used for ECE measurement. PLZT(7/65/35) and PLZT(9.1/65/35) ceramics were sintered from the commercial powders (Hayashi Chemical) as starting materials. BaTiO3 ceramics were sintered from the commercial powders (Toda Kogyo). The powders were fired at 1225–1275°C for PLZT ceramics at 1300–1400°C for BaTiO3 ceramics, respectively [20-22].

The ceramics were polished and then produced electrodes using a silver paste. And the ceramics were polarized for 20 min in a silicone bath under a DC field of 20 kV/cm at room temperature. The dielectric constant and tanδ were measured at 1 kHz with an oscillating voltage of 1 V. An alternating electric field of 0.1 Hz was used in these measurements. The dielectric constant was measured using an Agilent Technology impedance analyzer, 4192A. Piezoelectric d33 meter (IACAS ZJ-3B) was used for piezoelectric measurements. Polarization–electric field (P–E) hysteresis loops of the samples at various temperatures were measured using a combination of a programmable signal generator and a charge amplifier (POEL 101). The samples were cut into 3–4 mm squares, and their temperatures were changed by immersing them in a heated or a cooled oil bath [21,22]. Strain–electric field (s–E) hysteresis loops of the samples at room temperature were measured using a combination of a programmable signal generator and a strain gauge. Triangular waves of 0.1 Hz with 30 kV/cm were applied to the samples in P–E and s–E measurements. The sample temperatures during the application of triangular waves of 0.1 Hz with 30kV/cm field were measured using a platinum thermometer. The sample temperatures changed periodically in accordance with the external field. The polarization reversals of the samples were monitored on the basis of signals from the charge amplifier (POEL 101). By synchronization of electric field to sample temperature, temperature–electric field (T–E) hysteresis loops were obtained.

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3. Results and discussion

3.1. Microstructure

Figure 4 shows SEM micrographs of the surface of the PLZT(7/65/35) and PLZT(9.1/65/35) ceramics sintered at 1225°C. Densely packed microstructures of both ceramics are observed. In the sintering temperature range between 1225°C and 1275°C, the grain growth was not remarkable for these samples; however, the surface roughening were observed in the ceramics sintered at 1275°C, suggesting the lead evaporation loss from the samples. Figure 5 shows SEM micrographs of the surface of the BaTiO3 ceramics sintered at 1300°C, 1350°C, and 1400°C. The surface of the BaTiO3 ceramics sintered at 1300°C consists of the small grains of 1–2 μm. The melted grains are observed in the BaTiO3 ceramics sintered at 1350°C, and large grains at 50–200 μm grains were observed in the BaTiO3 ceramics sintered at 1400°C. This suggests the abrupt grain growth happened in the sintering temperature above 1350°C.

Figure 4.

SEM micrographs of the surface of the PLZT(7/65/35) and PLZT(9.1/65/35) ceramics sintered at 1225°C.

Figure 5.

SEM micrographs of the surface of the BaTiO3 ceramics sintered at 1300°C, 1350°C, and 1400°C.

3.2. Electrical properties

Figure 6 shows the P-E hysteresis loops at 10°C, 27°C, and 100°C, s–E hysteresis loops at room temperature, and the T–E hysteresis loops of the PLZT(7/65/35) and PLZT(9.1/65/35) ceramics sintered at 1225°C. Those of the BaTiO3 ceramics sintered at 1300°C, 1350°C, and 1400°C are shown in Fig. 7. The electrical properties of these ceramics are summarized in Table 1. The change to “soft” ferroelectrics with La content increase yields the increase in dielectric constant, the decrease in remanent polarization (Pr) and coercive force (Ec), the slanted and slim P-E hysteresis loops, and the parabolic s-E loops in the PLZT(9.1/65/35) ceramics, compared with the PLZT(7/65/35) ceramics. In the case of BaTiO3 ceramics, ferroelectricity increases with the grain growth accompanying the higher sintering temperature. The increase in Pr and d33, the more distinct shrink around Ec in s-E loops with sintering temperature would be due to the increase of ferroelectricity. The low Ec in the BaTiO3 sintered at 1300°C is probably due to the slim P-E loop in weaker ferroelectricity and the low Ec in the BaTiO3 sintered at 1400°C is due to the high domain mobility in large grain ceramics. The higher dielectric constant in the BaTiO3 sintered at 1300°C compared with those in the BaTiO3 sintered at 1350°C and 1400°C is characteristic of BaTiO3 ceramics, and the similar results that BaTiO3 with grains with at around 1μm size have been reported thus far [23-25].

Dielectric constant Pr (μC/cm2) Ec (kV/cm) d33 (pC/N)
PLZT(7/65/35) 2464 15.5 6.9 490
PLZT(9.1/65/35) 5564 2.4 2.3 37
BT sintered at 1300°C 3927 4.7 3.3 97
BT sintered at 1350°C 1966 7.1 4.5 126
BT sintered at 1400°C 1591 7.2 3.2 137

Table 1.

Electrical properties of PLZT and BaTiO3 ceramics

Figure 6.

Polarization–electric field (P–E) loops (above), strain–electric field (s–E) loop (middle), and temperature–electric field (T–E) loop (below) of the PLZT(7/65/35) and PLZT(9.1/65/35) ceramics sintered at 1225°C.

Figure 7.

Polarization–electric field (P–E) loops (above), strain–electric field (s–E) loop (middle), and temperature–electric field (T–E) loop (below) of the BaTiO3 ceramics sintered at 1300°C, 1350°C, and 1400°C.

3.3. Indirect estimation

The dP/dT between 10°C and 100°C for the PLZT and BaTiO3 ceramics were calculated using P-E hysteresis loops. Estimated ∆T for from Equation (1) for these ceramics are shown in Table 2. Among the ceramics, PLZT(9.1/65/35), which contains relaxor behavior by introducing Lanthanum substitution, estimated the largest temperature change. Among the BaTiO3 ceramics, the BaTiO3 sintered at 1400°C with large grains and accompanying strong ferroelectricity estimated the largest temperature change.

Samples dP/dT (μCcm-2K-1) Estimated ∆T(K) Measured ∆T(K)
PLZT (7/65/35) -0.031 0.35 0.07
PLZT (9.1/65/35) -0.051 0.58 0.26
BT sintered at 1300°C -0.030 0.29 0.12
BT sintered at 1350°C -0.026 0.25 0.08
BT sintered at 1400°C -0.037 0.36 0.29

Table 2.

Electrocaloric properties of PLZT and BaTiO3 ceramics

3.4. Direct measurement

Figures 6 and 7 contain s-E loops and T-E loops of the PLZT and BaTiO3 ceramics. The similar shapes between s-E loops and T-E loops are observed in these samples. The similar results were reported by J. Wang et al. and our previous report. Field-induced displacement derives from the change in the polarization, and the appearance of similar loops is reasonable. The temperature change ∆T of the samples was calculated from the slope beginning with maximum field and ending at the zero field. The temperature change, ∆T, in PLZT(9.1/65/35) ceramics induced by bipolar switching field of 30 kV/cm was 0.26K, and that in the BaTiO3 sintered at 1400 °C by bipolar switching field of 30 kV/cm was 0.29K. The round T-E and s-E shapes around polarization switching observed in the loop from PLZT(9.1/65/35) attributes characteristic of relaxor ferroelectric materials. The decreasing transition temperature and increasing the polarization movements in relaxor ferroelectrics provide larger temperature change.

The direct measurement shows smaller values, compared with the estimation, generally. The reasons are unknown at present; heat dissipation may play a role in real systems. Although quantitative consistency is not obtained, it is safe to say that the materials with large dP/dT provided large temperature change generally.

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4. Conclusion

The electrocaloric properties of (Pb,La)(Zr,Ti)O3 (PLZT) and BaTiO3 ceramics were investigated by the indirect estimation and direct measurement of temperature–electric field (T–E) hysteresis loops. The measured T-E loops showed a similar shape to strain–electric field (s–E) loops. This suggests the ECE of these materials are mainly governed by the change of their polarization. The extrinsic contribution from the multi-domain behavior to ECE is limited. The adiabatic temperature change ∆T due to electrocaloric effects was estimated from the polarization change of these samples. ∆Ts of 0.58 and 0.36 K were estimated for the (Pb,La)(Zr,Ti)O3 (PLZT)(9.1/65/35) ceramics and BaTiO3 ceramics sintered at 1400°C, respectively. The measured temperature changes, ∆Ts, in these samples upon the release of the electric field from 30 kV/cm to zero were 0.26 and 0.29 K, respectively.

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Acknowledgments

This study is partly supported by grant from KAKENHI Grant Number. 26420684, GRENE (Green Network of Excellence) project from The Ministry of Education, Culture, Sports, Science and Technology, Japan, and Kato Science Foundation.

References

  1. 1. Correia T and Zhang Q editors: Electrocaloric materials, Springer, 2014. p.1–12. DOI: 10.1007/978-3-642-40264-7
  2. 2. Lines ME and Glass AM: Principles and applications of ferroelectrics and related materials, Clarendon press, Oxford, 1977; 148–150
  3. 3. Moya X, Kar-Narayan S, Mathur ND: Caloric materials near ferroic phase transitions. Nat. Mater., 2014;13:439–450. DOI: 10.1038/nmat3951
  4. 4. Valant M: Electrocaloric materials for future solid-state refrigeration technologies. Prog. Mater. Sci., 2012;57: 980–1009. DOI: 10.1016/j.pmatsci.2012.02.001
  5. 5. Kobeko P and Kurtschatov J: Dielectriche Eigenshaften der Seignettesalykristalle. Zeit. Phys.,.1930;66:192
  6. 6. Mischenko AS, Zhang Q, Scott JF, Whatmore RW and Mathur ND: Giant electrocaloric effect in thin-film PbZr0.95Ti0.05O3.Science, 2006;311: 1270–1271. DOI: 10.1126/science.1123811
  7. 7. Tuttle BA and Payne DA: The effects of microstructure on the electrocaloric properties of Pb(Zr,Sn,Ti)O3 ceramics, Ferroelectr., 1981;37: 603–606. DOI: 10.1080/ 00150198108223496
  8. 8. Chukka R, Cheah JW, Chen Z, Yang P, Shannigrahi S, Wang J, Chen L: Enhanced cooling capacities od ferroelectric materials at morphotropic phase boundary. Appl. Phys. Lett.,2011;98:242902. DOI: 10.1063/1.3595344
  9. 9. Zhang R, Peng D, Xiao D, Wang Y, Zhu J, Yu P, Zhang W: Preparation and Characterization of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 electrocaloric ceramics. Crys. Res. Technol.,1998;33: 827-832. DOI: 10.1002/(SICI)1521-4079(1998)33:5<827::AID-CRAT827>3.0.CO;2-H
  10. 10. Shebanovs L, Borman K, Lawless WN, Kalvane A: Electrocaloric effect in some perovskite ferroelectric ceramics and multilayer capacitor. Ferroelectr., 2002;273: 137–142. DOI: 10.1080/00150190211761
  11. 11. Mischenko AS, Zhang Q, Whatmore RW, Mathur ND: Giant electrocaloric effect in the thin film relaxor ferroelectric 0.9PbMg1/3Nb2/3O3–0.1PbTiO3 near room temperature. Appl. Phys. Lett, 2006;89: 242912. DOI: 10.1063/1.2405889
  12. 12. Lin GC, Xiong XM, Zhang JX, Wei Q: Latent heat study of phase transition in Ba0.73Sr0.27TiO3 induced by electric field. J. Therm. Anal. Calor, 2005;81:41–44. DOI: 10.1007/s10973-005-6369-5
  13. 13. Kar-Narayan S and Mathur ND: Direct and indirect electrocalorc measurements using multilayer capacitor. J Phys. D: Appl. Phys, 2010;43: 032002. DOI: 10.1088/0022-3727/43/3/032002
  14. 14. Chen H, Ren TL, Wu XM, Yang Y, Liu LT: Giant electrocaloric effect in lead-free film of strontium bismuth tantalite. Appl. Phys. Lett, 2009;94:182902. DOI: 10.1063/1.3123817
  15. 15. Neese B, Chu B, Lu SG, Wang Y, Furman E, Zhang QM: Large electrocaloric effect in ferroelectric polymers near room temperature, Science, 2008; 321: 821–823. DOI: 10.1126/science.1159655
  16. 16. Lu SG, Rožič B, Zhang QM, Kutnjal Z, Pirc R, Lin M, Li X, Gorny L: Comparison of directly and indirectly measured electrocaloric effect in relaxor ferroelectric polymer. Appl. Phys. Lett. 2010; 97: 202901. DOI: 10.1063/1.3514255
  17. 17. Lu SG, Rožič B, Zhang QM, Kutnjal Z, Neese B: Enhanced electrocaloric effect in ferroelectric poly(vinylidene-fluoride/trifluoroethylene) 55/45 mol% copolymer at ferroelectric-paraelectric transition. Appl. Phys. Lett, 2011; 98: 122906. DOI: 10.1063/1.3569953
  18. 18. Weisman GG, IEEE Trans. Electron Devices, 1969; ED-16: 588
  19. 19. Wang J, Yang T, Wei K, and Yao X: Temperature-electric field hysteresis loop of electrocaloric effect in ferroelectricity—Direct measurement and analysis of electrocaloric effect. I. Appl. Phys. Lett. 2013;102: 152907. DOI: 10.1063/1.4801997
  20. 20. Maiwa H: Characterization of electrocaloric properties by indirect estimation and direct measurement of temperature–electric field hysteresis loops. Jpn. J. Appl. Phys. 2015;54: 10NB08. DOI: 10.7567/JJAP.54.10NB08
  21. 21. Maiwa H: Pyroelectric and electrocaloric properties of PZT- and BT-based ceramics. Ferroelectr., 2013;450: 84–92. DOI: 10.1080/00150193.2013.838497
  22. 22. Maiwa H, Jia TT, and Kimura H: Energy harvesting using PLZT and lead-free ceramics and their piezoelectric properties on the nano scales. Ferroelectr., 2015;475: 71–81. DOI: 10.1080/00150193.2015.995518
  23. 23. Kinoshita K, Yamaji A: Grain-size effects on dielectric properties in barium titanate ceramics. J. Appl. Phys., 1976;47: 371–373. DOI: 10.1063/1.322330
  24. 24. Arlt G, Hennings D, De With G: Dielectric properties of fine-grained barium titanate ceramics. J. Appl. Phys., 1985;58: 1619–1925. DOI: 10.1063/1.336051
  25. 25. Maiwa H: Advances in ceramics - Electric and magnetic ceramics, bioceramics, ceramics and environment. InTech, 2011; p.3-22.

Written By

Hiroshi Maiwa

Submitted: December 9th, 2014 Reviewed: November 2nd, 2015 Published: November 11th, 2015