超大应变BNT基厚膜叠层无铅压电执行器及其界面调控机理

The lead-free multilayer piezoelectric actuator has the potential of wide application due to the advantages of environment compliance, high displacement resolution, high response speed, low-voltage driving, and low power consumption. However,the field-induced strain is too low for industrial application. Recently, a temperature-insensitive lead-free piezoceramics with giant strain based on KNN modified BNT ceramics have been developed. However,the property of high strain can only be realized at relatively high electric fields exceeding 80 kV/cm. In order to get this giant field-induced strain at very small applied voltage, the BNT-based lead-free thick films with thickness of 10-100μm will be used to fabricate multilayer piezoelectric actuators. Moreover, based on the optimization of the piezoelectric/electrode interfacial layer and structure parameters, the microstructural engineering technologies including the control of residual stress, fining grain size, and reducing thickness of piezoelectric active layer are employed to improve piezoelectric coefficient and depolarization temperature, which shines the research and development of lead-free piezoelectric devices. Furthermore, the planned project will employ PFM and in situ XRD aided with Rietveld Profile Refinement methods to investigate the relationships between microstructures, field-induced phase transition, as well as field-induced domain-wall motions and field-induced strain of multilayer lead-free piezoelectric actuators. Based on the theoretical study of the mechanisms of field-induced strain and the model empirical formula, the field-induced domain-wall motion, phase transition, and field-induced strain of multilayer piezoelectric actuators with various microstructures and residual stress will be proposed, which will help to optimize the structural parameters of actuators and to guide the design for high-performance multilayer lead-free piezoelectric actuators.

叠层无铅压电执行器环保、位移精度高、响应快、能耗小、驱动电压低应用极为广泛,但是目前所能达到的应变值较小。KNN改性的BNT基无铅压电陶瓷具有0.48%的超大场致应变但需在80kV/cm的高电场下实现,难以实际应用。项目拟采用10-100μm厚的KNN改性BNT基压电厚膜层制备叠层压电执行器，从而在较小的电压下实现极高的场致应变。并在优化界面与微结构参数的前提下，通过调控应力、细化晶粒、减薄压电层等"结构工程"的方法提高压电系数与退极化温度，制备出具有超大应变的无铅叠层压电执行器，为无铅压电器件研发提供了新的思路。采用PFM与XRD原位观测技术对场致相变与非180 电畴翻转进行分析，揭示微观结构、相变与畴变对叠层压电执行器的场致应变的影响规律。建立不同微观结构以及残余应力下的场致相变、畴变与场致应变的理论模型与经验公式,对厚膜叠层无铅压电执行器进行优化设计，具有极大的理论意义与应用价值。

压电致动器具有结构简单、位移精度高、响应快、驱动力大、无电磁干扰、无噪声、结构刚度大等优点，可应用于航空航天、汽车、精密光学仪器、微电子机械、生物医学、机器人以及消费电子等领域，市场极为巨大。采用多层压电致动器的汽车发动机喷油嘴，喷射速度比传统电磁式喷油嘴快4-5倍，可更精确控制燃油喷射量，不但降低了油耗（降低约20%），提高了发动机功率（约5%），更减少了NOx等污染气体和PM2.5的排放，在能源短缺以及环境日益恶化的形势下，具有重大意义。KNN改性的BNT基无铅压电陶瓷具有0.48%的超大场致应变但需在80kV/cm的高电场下实现,难以实际应用。项目采用10-100μm厚的KNN改性BNT基压电厚膜层制备叠层压电执行器，从而在较小的电压下实现极高的场致应变。. 开发出了一种新的大应变弛豫铁电材料0.91Bi1/2Na1/2TiO3- 0.06BaTiO3-0.03AgNbO3（BNT-BT-AN），由于不含有易挥发的K元素，这一体系的烧结特性和性能可重复性均优于BNT-BT-KNN陶瓷。在此基础上，通过流延工艺制备出织构化的BNT-BT-AN陶瓷及厚膜进一步降低了驱动电场。设计和制备了BNT基多层无铅压电致动器，采用流延法制备出了BNT-BT-AN陶瓷生坯带，并利用丝网印刷法制备出Pt内电极，经过叠层、热压和共烧，成功制备出24层、单层厚度分别为114 μm和71 μm的两种多层致动器，6 kV/mm的电场下具有高达0.3%的应变（远高于日本学者报到的0.17%），在高达150 °C温度也具有很好的应变性能，并且表现出较好的耐疲劳特性。