P–E hysteresis loop going slim in Ba0.3Sr0.7TiO3-modified Bi0.5Na0.5TiO3 ceramics for energy storage applications

Dielectric capacitors as a passive component are widely used in fields such as household electronics, high-frequency inverters, high-power lasers, benefiting from their merits of high-power density, ultrafast charge-discharge rates, and exceptional temperature stability. However, low energy density of dielectric materials compared to other chemical power systems such as Li-batteries limits their applications. Normal ferroelectric Bi_0.5Na_0.5TiO₃ possesses high maximum polarization but high remanent polarization leads to poor energy storage properties. Therefore, how to effectively utilize high polarization of Bi_0.5Na_0.5TiO₃ via composition/structure design becomes very important.

A research group led by Professor Zong-Yang Shen from Jingdezhen Ceramics University proposed to use paraelectric Ba_0.3Sr_0.7TiO₃ (Wang et al., Ceram. Int. 2015) for modifying normal ferroelectric Bi_0.5Na_0.5TiO₃, and prepared a series of (Ba_0.3Sr_0.7)_x(Bi_0.5Na_0.5)_1-xTiO₃ (BS_xBNT, x = 0.3–0.8) ceramics solid-solutions, and optimize successfully the polarization behavior in maintaining high polarization but reducing remanent polarization. This work lays a foundation for dielectric energy storage applications since high polarization at low electric field conditions.

The team published their work in the Journal of Advanced Ceramics on April 07, 2020.

Ferroelectric is a special crystal that exhibits spontaneous polarization within a certain temperature range, and the direction of spontaneous polarization can rotate reversibly with an applied electric field. Normally, ferroelectrics include normal ferroelectric and relaxor ferroelectric, and both of which have a difference in domain structure leading to different dielectric and polarization characteristics. For dielectric energy storage, relaxor ferroelectric with small polar-nanoregions (PNRs), compared to normal ferroelectric with macro-domain, possesses the advantage of frequency dispersion phenomenon and slim polarization behavior.

“In this work, we aim to solve the issue of utilizing effectively the maximum polarization and develop a new Bi_0.5Na_0.5TiO₃-based relaxor ferroelectric ceramics for energy storage applications. As Ba_0.3Sr_0.7TiO₃ content increases, the dielectric constants and corresponding transition temperatures at dielectric peaks both decrease over a wide temperature range, the remanent polarization sharply while maximum polarization slowly decreases. Importantly, we obtain some representative compositions (x = 0.35 and 0.5) with well dielectric and ferroelectric properties, which make them potential for electrostatic capacitors.” said Prof. Shen, vice dean of the School of Material Science and Engineering at Jingdezhen Ceramics University.

Specifically, phase structure evolves from tetragonal symmetry to pseudo-cubic one with the increase of Ba_0.3Sr_0.7TiO₃ content. The transition temperature at maximum dielectric constant decreases from 110 ℃ (x = 0.3) to –45 ℃ (x = 0.8), across T_m = 36 ℃ (x = 0.5) with a maximum dielectric constant ɛr = 5920 @1kHz. P-E loops go slim together with maximum polarization gradually while remnant polarization sharply decreases, which is closely related to domain size decreases. BS_xBNT with x = 0.5 compositions obtain a maximum difference between P_max and P_r (P_max–P_r) and high recoverable energy density of ~1 J/cm³ under a low electric field of 100 kV/cm. Besides, BS_xBNT with x = 0.5 ceramics displays well temperature/frequency/fatigue-stability in energy storage properties.

The research team expects this work could provide more chances to advance the progress of medium-high voltage capacitors in the future. Next, they will devote to improving the temperature stability of Bi_0.5Na_0.5TiO₃-based relaxor ferroelectric over a wide temperature range from -55 °C to 125, even 150 °C, and improving polarization behavior of Bi_0.5Na_0.5TiO₃-based relaxor ferroelectric via defect engineering. “For the goal of preparing high-quality ceramic power and multi-layer devices, we will do more work on the preparation, and pay more attention to push the advancement of functional ceramics field.” Professor Zong-Yang Shen from Jingdezhen Ceramics University said.

Other contributors include Dongxu Li, Zhipeng Li, Wenqin Luo, Zhumei Wang, Fusheng Song, and Yueming Li from Jingdezhen Ceramics University, and Xingcai Wang from Chengdu Hongke Electronic Technology Co., Ltd.

This work was financially supported by the National Natural Science Foundation of China (51767010), the Science & Technology Key Research Project of Jiangxi Provincial Education Department (GJJ170760), and the Graduate Student Innovation Fund of Jiangxi Province (YC2018-S295).

About Journal of Advanced Ceramics

Journal of Advanced Ceramics (JAC) is an international journal that presents the state-of-the-art results of theoretical and experimental studies on the processing, structure, and properties of advanced ceramics and ceramic-based composites. JAC is Fully Open Access, monthly published by Tsinghua University Press on behalf of the State Key Laboratory of New Ceramics and Fine Processing (Tsinghua University) and the Advanced Ceramics Division of the Chinese Ceramic Society, and exclusively available via SciOpen. JAC has been indexed in SCIE (IF = 16.9, top 1/28, Q1), Scopus, and Ei Compendex.

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