高性能铋层状结构超高温压电材料结构缺陷调控机理

Bismuth layer-structured ceramics with high Curie temperature (Tc > 650 °C) are one of the most important high-temperature electronic component materials, which can be manufactured to high-temperature piezoelectric transducers working at 400-700 °C for widely using in automotive, aerospace, nuclear power, power generation and chemical engineering industries, etc. However, the piezoelectric response (d33) of this type of materials is relatively poor because of their special crystal structures. Therefore, in this project, CaBi2Me2O9 (Me = Nb, Ta) with high Tc of > 900 °C are chosen as the objects of study, and the tailoring mechanism of the structural defects caused by the ionic substitution on their structures and improved properties are specifically investigated, with the aim of developing new ultrahigh-temperature piezoelectric materials. To be detail, firstly, the CaBi2Me2O9-based piezoelectric ceramics are prepared, and their crystal structures, microstructures and domain structures are determined. Secondly, the tailoring effects of different types of structural defects on structures and properties of CaBi2Me2O9-based materials are revealed, and the correlation between tailored structure and improved performance is clarified. Finally, the kinds of structural defects in CaBi2Me2O9-based materials are determined, and the defect polarization in bismuth layer-structured ferroelectrics is explored, which is controlled to contribute to the ferroelectric polarization and piezoelectric properties.

高居里温度（Tc > 650 °C）的铋层状结构压电陶瓷是最为重要的高温电子器件材料之一，其可制作成工作温度为400-700 °C的高温压电传感器，广泛用于汽车、航空航天、核能、发电、化工等领域。但是，由于其独特的晶体结构，这类材料的压电响应（d33）相对较低。本项目拟以Tc高于900 °C的铋层状结构压电陶瓷CaBi2Me2O9（Me = Nb、Ta）为研究对象，研究离子固溶取代诱导的结构缺陷对材料结构和优化性能的调控机理，开发新型高d33的超高温压电材料。首先，研究CaBi2Me2O9基陶瓷材料的制备工艺，确定其晶体结构、显微结构、电畴结构。其次，揭示不同结构缺陷对CaBi2Me2O9基材料结构和性能的调控作用，阐明调控结构与优化性能之间的相关性。最后，研究CaBi2Me2O9基材料内结构缺陷类型，探索铋层状结构铁电体的缺陷极化机制，引导其对材料铁电极化以及压电性能的贡献。

高温压电传感器是一类重要的电子元器件，广泛地应用于航天航空、核能、发电、船舶等领域，用来健康监控和无损伤检测各类装置高温工作状态。高温压电材料是高温压电传感器的核心器件。本项目首先研究了铋层状结构高温压电材料内缺陷如氧空位的形成机理，揭示了缺陷及缺陷极化对材料电学性能的作用机制，掌握了不同掺杂取代等方式对缺陷种类和浓度的影响规律；其次揭示了铋层状结构高温压电材料电导机制，其主要为p-型电导，导电离子为正电空穴。通过W6+、Nb5+等施主掺杂可以大大地增加它们的高温电阻率（电导率），显著地降低了其漏导损耗，增大其耐击穿电场。此外，可以通过受主取代使铋层状结构高温压电材料转变为氧离子导体，650-800度时其离子电导率大于0.01 S/cm2，氧迁移数为0.91-0.94。最后通过多种晶格缺陷复合改良了铋层状结构高温压电材料的电学性能，有意义地是获得了多种居里温度(Tc)高、压电活性(d33)高、铁电极化强度(Pr)大、电致应变量(S33)大、高电阻率(p)大且热稳定性好的高温超高温压电传感器材料，其Tc、d33、Pr、S33，分别高达953°C、23.5 pC/N、26.98 uC/cm2、7.59x 10-4、28.2 pC/N。