Yang Ziqi, Wang Bing, Li Yizhe, Hall David A
Department of Materials, University of Manchester, Manchester M13 9PL, UK.
Materials (Basel). 2022 Apr 14;15(8):2872. doi: 10.3390/ma15082872.
BiFeO-BaTiO (BF-BT) ceramics exhibit great potential for diverse applications in high temperature piezoelectric transducers, temperature-stable dielectrics and pulsed-power capacitors. Further optimization of functional properties for different types of applications can be achieved by modification of processing parameters or chemical composition. In the present work, the influence of pentavalent niobium substitution for trivalent ferric ions on the structure, microstructure and dielectric properties of 0.7BF-0.3BT ceramics was investigated systematically. Doping with niobium led to incremental reductions in grain size (from 7.0 to 1.3 µm) and suppression of long-range ferroelectric ordering. It was found that core-shell type microstructural features became more prominent as the Nb concentration increased, which were correlated with the formation of distinct peaks in the dielectric permittivity-temperature relationship, at ~470 and 600 °C, which were attributed to the BT-rich shell and BF-rich core regions, respectively. Nb-doping of BF-BT ceramics yielded reduced electronic conductivity and dielectric loss, improved electrical breakdown strength and enhanced dielectric energy storage characteristics. These effects are attributed to the charge compensation of pentavalent Nb donor defects by bismuth vacancies, which suppresses the formation of oxygen vacancies and the associated electron hole conduction mechanism. The relatively high recoverable energy density (W = 2.01 J cm) and energy storage efficiency (η = 68%) of the 0.7BiFeO-0.3BaTiO binary system were achieved at 75 °C under an electric field of 15 kV mm. This material demonstrates the greatest potential for applications in energy storage capacitors and temperature-stable dielectrics.
BiFeO₃-BaTiO₃（BF-BT）陶瓷在高温压电换能器、温度稳定电介质和脉冲功率电容器等多种应用中展现出巨大潜力。通过改变加工参数或化学成分，可以进一步优化不同类型应用的功能特性。在本工作中，系统研究了五价铌取代三价铁离子对0.7BF-0.3BT陶瓷结构、微观结构和介电性能的影响。铌掺杂导致晶粒尺寸逐渐减小（从7.0微米降至1.3微米）并抑制了长程铁电有序性。发现随着铌浓度增加，核壳型微观结构特征变得更加显著，这与介电常数-温度关系中在约470℃和600℃出现的明显峰值相关，分别归因于富BT壳层和富BF核区域。BF-BT陶瓷的铌掺杂降低了电子电导率和介电损耗，提高了电击穿强度并增强了介电储能特性。这些效应归因于五价铌施主缺陷通过铋空位进行的电荷补偿，这抑制了氧空位的形成以及相关的电子空穴传导机制。在75℃、15 kV/mm的电场下，0.7BiFeO₃-0.3BaTiO₃二元体系实现了相对较高的可恢复能量密度（W = 2.01 J/cm³）和储能效率（η = 68%）。这种材料在储能电容器和温度稳定电介质应用中展现出最大潜力。
