核壳结构BNT/KNN基压电复合膜界面效应对其力电耦合性能的调控与相场模拟

Study on lead-free piezoelectric composite films was significant to the theorical research and practical value in the application of actuator, for high field excitation of high electric field induced strain, but lower effective piezoelectric coefficient and temperature stability. Modified sol-gel method in this project compatible with MEMS process was intended to adopt to prepare the core-shell structure BNT/KNN-based piezoelectric composite films with BNT-based relaxor and KNN-based ferroelectric， potassium sodium niobate powder synthesized by hydrothermal or solid state reaction method and modified-sodium bismuth titanate precursor solution synthesized by sol-gel method. By optimizing process parameters, the rule between structure and performance of the piezoelectric composite film was studied, and according to it, the key technologies for the composite film structure control can be draw. Phase field modeling of core-shell structure BNT/KNN-based piezoelectric composite films can be used to analyze interfacial effects on domain movement, the polarization inversion under field effect, and then it can theoretically explain the interface effect on the electromechanical coupling. The essence of electromechanical coupling properties can be revealed by binding assay results and theoretical simulation results, for the core-shell structure relaxor / ferroelectric phase piezoelectric composite film, and which can be used as guidance for high-performance features regulation, as well as new material designing and exploiting, to lay the foundation for the development of actuator.

针对高场下激发产生高电致应变，却降低有效压电系数和温度稳定性的缺陷，积极开展新型高力电耦合性能无铅压电复合材料的研究具有重大的科学意义和广阔的应用前景。本项目拟采用兼容于MEMS工艺的改进0-3复合溶胶-凝胶方法，将形貌、尺寸可控、表面功能化铌酸钾钠基铁电相粉体与有机物改性的弛豫相钛酸铋钠基前驱体溶胶进行复合，制成核壳结构BNT/KNN基压电复合膜；通过工艺参数的优化，研究复合膜界面效应对其力电耦合性能的调控规律，明确最佳性能产生的结构根源；通过对核壳结构BNT/KNN基压电复合膜相场建模，分析外场作用下界面效应对复合膜电畴运动、极化反转的影响，从理论上推导其力电耦合性能的作用机理；通过实验检测结果与理论模拟结果的结合，揭示核壳结构弛豫相/铁电相压电复合膜力电耦合性能的本质，为高性能压电复合膜功能的调控、材料的改性以及新体系的探索提供指导，为发展高性能无铅致动器奠定基础。

随着器件微型化、集成化的发展，铁电压电薄/厚膜以其体积小、重量轻、便于集成化、微型化、操作电压低、驱动能力大、响应速度快等优点，正逐渐成为微机电系统（MEMS）、传感器和换能器等领域的研究热点。然而，目前使用最多的是铅基材料。但是，铅生产过程中的挥发和难回收处理给人类的环境造成极大的危害。因此，对于新型高力电耦合性能无铅压电复合材料的研究具有重大的科学意义和广阔的应用前景。本项目采用改性的0-3复合法制备出不同体系的无铅压电复合厚膜BNT/KNN-基，BNT/BNT-基，BZT/KNN；系统深入的研究了不同外场作用下，复合膜微观结构及力学、电学特性，分析对比了不同组成复合膜中界面态对电畴翻转的影响，阐明了核壳结构压电复合膜力电耦合的作用机理。最终得到，BNT/KNN40压电复合膜的夹持压电系数达到50.1 pC/N，疲劳测试表明，复合膜在室温下可达到105次铁电反转，压电性能衰减小于10%，表明其抗疲劳特性好,温度稳定性优良的新型压电复合膜材料；相场分析表明：外加压应力作用下，薄膜内部电畴主要发生90°电畴的翻转，最终形成平行于薄膜表面的极化取向；外加电场作用下，薄膜内部主要发生90°和180°电畴的翻转，最终在薄膜形成平行于极化电场方向的偶极取向呈现出高的压电性能。通过不同材料的复合，可以有效的调控复合膜内的界面态，调节界面梯度应力，从而有效的调控电畴翻转，从宏观上有目的地调节材料的力电耦合性能，为高性能压电复合膜功能的调控、新体系的探索提供指导，为发展高性能、微型化、环保无铅致动器奠定基础。