BNT基低电场高电致应变三元无铅压电陶瓷的结构调控及其机理研究

With respect to the strain response in BNT-based ceramics, two most urgent tasks are to effectively reduce the electric field required for activating this large strain behavior, and to enhance the temperature stability of the large strain with the minimum degradation of the maximum achievable strains, which limit the use in practical actuator applications. Based on the above mentioned, the relationship between the tolerance factor and strain behavior in BNT-based lead-free piezoelectric ceramics will be clarified, and the type of the additive Bi(MeMe)O3 which can effectively reduce the electric field required for activating the large strain response in BNT-BT/BKT binary system will be excavated in terms of phase structure, the degree of crystal lattice distortion and tolerance factor of the Bi(MeMe)O3. In this project, templated grain growth technology will be used to control the microstructure, and to fabricate BNT-BT/BKT-Bi(MeMe)O3 lead-free piezoelectric ceramics with the promising strain response. Influence of the sintering process and the content, type and size of the template on microstructure, phase structure and strain behavior of BNT-based ceramics will be investigated thoroughly. The composition-microstructure-phase structure-strain behavior relation in textured BNT-based lead-free piezoelectric ceramics will be revealed, and the relationship between structure (phase structure and microstructure) in BNT-based lead-free piezoelectric ceramics will be established. On the basis of phase structure and microstructure control , the present project provides the foundation for the preparation of BNT-based lead-free piezoelectric ceramics with optimized strain properties featured by not only large strain response at a low driving field but also promising the temperature stability, and extends practical actuator applications for lead-free piezoelectric materials.

BNT基陶瓷，在实现高应变响应时所需要的外加电场值较高以及高电致应变的温度稳定性较差，限制其在压电驱动器中的应用。本项目针对这一问题，通过在BNT-BT/BKT中引入具有不同相结构、晶胞畸变程度及容忍因子的Bi(MeMe)O3组元, 阐明BNT基材料中容忍因子与电致应变特性的作用机理，挖掘出有效改善BNT-BT/BKT陶瓷电致应变特性的第三组元Bi(MeMe)O3；拟采用微观结构调控(织构化)手段制备优化的BNT-BT/BKT-Bi(MeMe)O3压电陶瓷，深入研究烧结过程、模板含量、种类及尺寸对其的微观结构、相结构和应变特性的影响，揭示陶瓷材料组分-微观结构-相结构-电致应变特性的关联程度，建立结构（相结构与微观结构）与应变行为的关系模型。本项目通过调控相结构和微观结构，为获得低电场高电致应变并伴随优异温度稳定性的BNT基陶瓷提供理论依据，为无铅压电驱动器实用化发展奠定基础。

BNT 基陶瓷材料由于其可逆的弛豫向铁电相的转变而具有高电致应变，适用于驱动器、传感器等器件中，在军事和医疗领域具有广阔的应用前景。然而，与传统铅基材料相比，目前BNT基材料存在三个焦点问题：在获得高应变响应时需要高的外加电场值、高电致应变温度稳定性差以及在产生高电致应变时伴随较大的滞后行为,从而限制其在压电驱动器中的应用。本项目围绕这些问题，采用具有不同相结构钙钛矿模板BaTiO3、NaNbO3、SrTiO3、(Bi0.5Na0.5)TiO3、(K0.5N0.5)NbO3 等，拟通过模板晶粒生长技术制备BNT-BKT-Bi(Me′Me″)和BNT-BT-ST 等陶瓷材料，获得同时具有相变特征和微观结构可控的BNT 基织构陶瓷材料；深入研究烧结过程、模板的相结构、种类、含量、尺寸对BNT基陶瓷微观结构、相变行为以及应变特性的影响规律，阐明不同相结构的钙钛矿模板对织构陶瓷的结构演变和应变行为的作用机制，揭示结构(微观结构和相结构)与应变性能之间的对应关系，获知钙钛矿模板-微观结构-相结构-电致应变特性的内在关联度，建立相应的理论指导基础。本项目通过优化制备工艺，调控相结构和微观结构，期望获得低电场高电致应变同时伴随良好温度稳定性及小的滞后行为的BNT 基压电织构陶瓷,为无铅压电驱动器的研究和实用化奠定基础。