新型超高温压电细晶陶瓷的制备及性能调控

The urgent need for ultrahigh-temperature piezoelectric devices is imperative in hi-tech domains such as aviation, energy and chemical industries. Currently, the development of ultrahigh-temperature piezoelectric materials mainly focuses on Bismuth layer-structured ferroelectrics (BLSF) with high Curie temperature. Dealing with the bottleneck problems that limit practical applications of ultrahigh temperature piezoelectric ceramics, this project will carry out experimental and theoretical investigations on the Bismuth layer-structured materials in the two aspects of composition design and preparation techniques, with the aim to develop practical ultrahigh temperature piezoelectric ceramics suitable for above-700℃ applications and with piezoelectric coefficient larger than 20pC/N. Novel ultrahigh temperature piezoelectric ceramic systems will be designed by solid-sloving weak and strong ferroelectric materials with ultrahigh Curie temperatures, so as to disclose phsyical and chiemical mechanisms that affect the performances of Bismuth layer-structured piezoelectric materials. The material performances are adjusted microscopically so as to solve the Curie temperature reduction problem resulted from doping in improving the piezoelectric performances. Meanwhile, using the water heat method, nano-scale ceramic precursor powders are synthesized and fine-grainedceramics are sintered specific craft under normal air pressures. This solves the material loss increase problem resulted from Bi volatilization during high-temperature sintering process. Moreover, such materials are easy to be polarized to enhance their piezoelectric performances. This project will provide new routes and new craft for the design and performance adjustment of high-performance ultrahigh temperature piezoelectric ceramics and thus is of engineering application and significant scientific.

航空航天、能源化工、军事等许多高科技领域迫切需求超高温压电器件，国际上高温压电器件材料开发主要集中在铋层状结构材料。本项目针对约束超高温压电陶瓷实用化进程的瓶颈问题，拟对铋层状压电材料从组分设计、制备工艺两方面进行实验和理论研究，旨在制备适合700℃以上使用、压电系数d33>20pC/N的实用化超高温压电陶瓷材料。设计将超高居里温度的弱铁电体与强铁电体相固溶的超高温压电陶瓷新体系，揭示影响铋层状结构压电材料性能的物理、化学机制，并在微观尺寸上对材料的性能进行调控，解决通常为改善压电性能采用掺杂取代而引起的材料居里温度降低问题；同时采用水热法合成纳米陶瓷前驱粉体，通过特殊的常压烧结工艺得到细晶陶瓷，解决材料难以极化及高温烧结造成Bi元素挥发导致材料损耗增大问题，增强其压电性能。该项目为高性能超高温压电陶瓷的设计、性能调控提供新思路、新工艺，具有重要工程应用价值和较大科学研究意义。

本研究针对约束铋层状压电材料超高温压电陶瓷实用化进程的瓶颈问题，将超高居里温度的弱铁电体与强铁电体相固溶，设计出了(1-x)CaBi2Nb2O9-xNa0.5Bi2.5Nb2O9高性能超高温铋层状结构压电陶瓷材料新体系，并在微观尺寸上对材料的性能进行调控，成功制备了适合700℃以上使用高温压电陶瓷，解决通常为改善压电性能采用掺杂取代而引起的材料居里温度降低问题；同时采用水热法合成纳米陶瓷前驱粉体，通过特殊的动态常压烧结工艺得到细晶陶瓷，得出晶粒为1μm左右的细晶陶瓷，前驱纳米粉体既能在较低温度烧结高致密度陶瓷，又能通过抑制Bi金属元素的挥发来保持相结构稳定性，并且没有引入任何杂相,因而能在较宽的低温区间内获得高性能的压电陶瓷。该工艺解决了材料难以极化及高温烧结造成Bi元素挥发导致材料损耗增大问题，增强其压电性能，成功制备了适合700℃以上使用、压电系数d33~13 pC/N的实用化超高温压电陶瓷材料。研究了尺寸效应对该结构材料的影响规律，实验结果表明，铋层状结构基陶瓷的压电性能存在晶粒尺寸效应。在0.1-10.8μm的晶粒尺寸范围内，1μm 左右铋层状结构基陶瓷具有最优性能，室温d33~18 pC/N。该项目从组分设计、制备工艺两方面进行了实验和理论研究，为高性能超高温压电陶瓷的设计、性能调控提供新思路、新工艺。