应用于微驱动器的高逆压电效应的无铅铁电压电薄膜的性能优化和机理探索

Ferroelectric and piezoelectric thin films, which can realize the energy conversion between the electric energy and mechanical energy, are one of the most ideal functional materials used in the micro- and nano- electric devices. The micro-actuator, which transfers the electrical energy into the mechanical energy based on the inverse piezoelectric effect, is a hot area of research in the field of micromechanical systems (MEMS) and nanoelectromechanical systems (NEMS). Big progress has been achieved in lead-free Bi0.5Na0.5TiO3 (BNT)-based ceramics that high inverse piezoelectric coefficient and large strain can be obtained in this system due to the electric field-induced-phase transition. As a result, the BNT-based ceramics are one of the most promising in lead-free candidates for actuators. However, the research on lead-free thin films used in the micro-actuators is still lacking. The purpose of this project is to prepare lead-free thin films with excellent inverse piezoelectric effect which can be used in the application of micro-actuators. BNT-based materials are chosen as the object of study to establish MPB in the system, and the electric field-induced-phase transition will be introduced to improve the properties. Furthermore, the influence of the substrate, interface and defects on the properties will also be controlled. We aim to obtain excellent inverse piezoelectric property in the BNT-based thin films which can replace the lead-based thin film in application to micro-actuators. Finally, the physical mechanism of performance improved by electric field-induced-phase transition, substrates, interface and defects will be explored to reveal the key factors determining the piezoelectric properties in the films. The physical model of the origin of piezoelectric effect will be established to provide theoretical foundation for the development and design of novel lead-free ferroelectric and piezoelectric thin films.

铁电压电薄膜兼具机电耦合的功能性和微型化的特点，是用来发展微纳电子器件的理想功能材料。微型驱动器利用铁电压电薄膜的逆压电效应，将电能转化为机械能，是MEMS和NEMS的研究热点。钛酸铋钠(BNT)基无铅铁电压电块体材料的研究取得了突破性进展，利用电场诱导在MPB处的相变获得高逆压电效应，为其取代铅基材料在驱动器领域的应用奠定了坚实的基础，但是应用于微型器件的无铅薄膜的研究还存在欠缺。本项目以无铅铁电压电材料在微型驱动器中的应用为导向，以BNT材料为基体，在薄膜中构建MPB，同时利用电场诱导相变增强其对逆压电效应的贡献；进一步通过薄膜衬底、界面和缺陷的调控，在BNT薄膜中实现与PZT可比拟的性能。在获得高性能薄膜的基础上，探索电场诱导和其他因素调控的物理机制，揭示薄膜中影响电性能的决定性因素，建立压电性能起源的物理模型，为高性能无铅铁电压电薄膜的发展提供理论依据，指导无铅薄膜研究的新思路。

铁电压电薄膜兼具机电耦合的功能性和微型化的特点，是用来发展微纳电子器件的理想功能材料。微型驱动器利用铁电压电薄膜的逆压电效应，将电能转化为机械能，是MEMS和NEMS的研究热点。钛酸铋钠(BNT)基无铅铁电压电块体材料的研究取得了突破性进展，利用电场诱导在MPB处的相变获得高逆压电效应，为其取代铅基材料在驱动器领域的应用奠定了坚实的基础，但是应用于微型器件的无铅薄膜的研究还存在欠缺。本项目利用化学溶液沉积技术，开展了BNT基薄膜的制备技术优化和应变性能探索研究。基于创建铁电/弛豫、铁电/反铁电等相界的指导思想，设计了多种组分的固溶体薄膜，制备了结构致密、低漏电流的薄膜。通过组分的调控，成功地在薄膜中构建出了铁电和非典型铁电相界。并在相界处获得高的逆压电系数和大应变响应，最大应变值可达1.7%，在无机铁电压电薄膜中是非常突出的性能。BNT基薄膜中超大应变响应来源于两个重要的贡献：一是电场诱导相界处的可逆相变；二是电场作用下铁电畴的演变和运动。本项目不仅实现了高性能薄膜的制备，而且建立了结构、铁电畴与性能的关系。基于本项目的研究，发表9篇高水平学术论文，申请发明专利2项。本项目的顺利实施，极大促进该体系薄膜在微纳机电系统中的应用，并为我国发展高性能的无铅铁电压电薄膜提供了原理性支撑。