压电换能器用钛酸铋钠基陶瓷大压电各向异性的结构本质和织构化制备新方法及机理

Based on the urgent demand of large piezoelectric anisotropy of transducers such as non-destructive tests, ultrasound diagnosis and hydrophone, et al. and inherent large piezoelectric anisotropy of Bi1/2Na1/2TiO3(BNT) ceramics, two core issues of piezoelectric anisotropy of kt/kp and piezoelectric anisotropy induced by grain orientation growth will be conducted in this project. The correlation between compositions, structure(domain), process and piezoelectric anisotropy will be investigated. The intrinsic and extrinsic piezoelectric anisotropy will be studied and the micromechanism of piezoelectric anisotropy will be obtained. The correlation between microstructure regulation and macroscopical piezoelectric anisotropy will be explored, and the regulation mechanism and tailor rules of large piezoelectric anisotropy will be obtained. The grain orientation growth and piezoelectric anisotropy induced by high cold press technical will be investigated. The mechanism of thermodynamics and kinetics of grain orientation growth will be explored and the micromechanism of grain orientation growth induced by high cold press technical will be revealed. The new preparation method and theory of textured BNT-based piezoelectric ceramics will be developed and perfected. The development of this project is expected to have major breakthroughs in preparation technical and theory for textured lead-free piezoelectric ceramics. The development of this project is expected to significantly improve the piezoelectric properties and anisotropy of BNT-based ceramics simultaneously, solve the materials demand of piezoelectric device for large anisotropy, low cost, green environmental protection. The results will open up a new way for the application of lead-free piezoelectric ceramics and have very important research value and scientific meaning.

针对无损检测、医疗超声诊断及水听器等压电换能器对大压电各向异性陶瓷的需求及Bi1/2Na1/2TiO3(BNT)基陶瓷固有的大压电各向异性，本项目围绕“压电各向异性结构本质”和“晶粒取向生长诱发的压电各向异性”两个核心内容开展研究。研究BNT陶瓷的组成/工艺/结构(电畴结构)/各向异性之间的关联，分析本征与非本征压电性能的各向异性效应，阐明压电各向异性的结构本质；探索微观结构调控与宏观各向异性的关系，获得压电各向异性的调控机理与裁剪规则。开展高冷压成型技术诱导晶粒取向生长与各向异性的研究，探讨晶粒取向生长的热力学和动力学机理，揭示高冷压成型诱导晶粒取向生长的微观机理，发展并完善制备取向生长BNT基陶瓷材料的新方法与理论。本研究有望在无铅压电陶瓷制备技术和理论上有重要突破，并同时大幅度提高BNT基陶瓷的压电性能及各向异性，为无铅压电陶瓷的应用开辟一条新的途径，有重要的研究价值和科学意义。

压电换能器材料要求尽可能高的厚度机电耦合系数kt与压电各向异性kt/kp，使换能器与媒介之间充分耦合而无寄生模式干扰，能量更集中于厚度模式，灵敏度与分辨高，器件更加小型化。针对压电陶瓷变压器等对大各向异性压电陶瓷的需求和BNT基陶瓷压电各向异性的国内外发展趋势，本项目主要研究了BNT陶瓷的组成/工艺/结构(电畴结构)/各向异性之间的关联，分析了本征与非本征压电各向异性，探索了压电性能大各向异性的微观机制；通过掺杂改性与制备工艺，获得了微观结构调控与宏观各向异性的关系，探明了大压电各向异性的裁剪规则；通过高冷压成型技术，研究了陶瓷组成、坯体尺寸、成型工艺以及烧结工艺等参数对物相、晶粒取向、微观结构和压电各向异性的影响，探讨高冷压成型诱导晶粒定向生长与压电各向异性的微观机理，发展并完善了制备取向生长的BNT基陶瓷的新方法与新理论，为压电陶瓷的织构化提供新的理论与方法。通过研究，大幅度提高了BNT 基无铅压电陶瓷的性能与压电各向异性，解决了压电换能器对大压电各向异性、低成本、绿色环保压电材料的需求，为无铅压电陶瓷的应用开辟了一条新的途径，有极为重要的研究价值和科学意义。