Understanding the mechanism of large dielectric response in Pb-free (1−x)Ba(Zr_0.2Ti_0.8)O₃−x(Ba_0.7Ca_0.3)TiO₃ ferroelectric ceramics

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• 作者：Jinghui Gao^a ; Xinghao Hu^a ; Yan Wang^a ; Yongbin Liu^a ; Lixue Zhang^c ; Xiaoqin Ke^a ; ^b ; ^{kexiaoqin@mail.xjtu.edu.cn} ; Lisheng Zhong^a ; ^{lszhong@mail.xjtu.edu.cn} ; Hui Zhao^a ; Xiaobing Ren^a ; ^d ; ^{ren.xiaobing@nims.go.jp}
• 关键词：Pb-free ferroelectric materials ; Dielectric property ; Domain structure ; Phase transition
• 刊名：Acta Materialia
• 出版年：2017
• 出版时间：15 February 2017
• 年：2017
• 卷：125
• 期：Complete
• 页码：177-186
• 全文大小：2351 K
• 卷排序：125

文摘

(1-x)Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) ceramics have been reported to exhibit large dielectric response in the vicinity of the multi-phase-coexisting point (i.e. triple point). However, the reason for large dielectric response in such a material system is still unclear and thus awaits explanation. In this paper, we investigate the reason for large dielectric response by studying the phase transition behavior around the triple point of BZT-xBCT ceramics. Our results show that the transition enthalpy nearly vanishes and the associated specific heat shows discontinuity on the triple point, which suggest tricritical behavior (i.e. crossover point from first to second order phase transition) for such a triple point. Further Rayleigh analysis indicates that strong dielectric response is due to large reversible contribution which may be caused by phase transition. Moreover, TEM study shows a mottled domain structure with numerous nanodomains close to tricritical triple point, which reveals a polarization isotropic state. In addition, a six-order Landau free energy modeling demonstrates that the energy barrier between paraelectric and ferroelectric phases nearly vanishes on the tricritical triple point, which facilitates large polarizability in the presence of external electric field and is thus responsible for large dielectric permittivity in BZT-xBCT.