PZT基压电陶瓷准同型相界处微观缺陷演化及其对相变和电性能的影响研究

In both Pb-contained and Pb-free materials,The basic approach to achieving high piezoelectricity is to place the composition of the material to the proximity of the morphotropic phase boundary (MPB), a composition-induced phase transition between ferroelectric rhombohedral(R) and tetragonal(T) phases.In spite of its wide application, the mechanism of ferro-ferro transition at MPB and the generation mechanism of the ultra high piezoelectricity and permittivity are not completely known. PZT-based piezoelectric ceramics，currently the most widely used piezoelectric materials, are investigated in this project.Defect evolution during ferro-ferro transition and its influence on electrical properties at MPB is studied by positron annihilation techniques. Studies involve the evolution of defects during composition induced transition and temperature induced transition,the stability of defects at MPB,the relationship between the variation of micro-defects and the variation of electrical properties (including piezoelectric, dielectric, ferroelectricity properties) with composition, temperature and time。From the point of micro-defects, the mechanism of ferro-ferro transition and the generation mechanism of the ultra high piezoelectricity at MPB in PZT-based piezoelectric ceramics will be given in this project. The conclusion of this project can be expanded to other piezoelectric materials and the study will provide physical guidance on the development of high performance piezoelectric ceramics.

使材料的组分位于铁电三方（或三角）-四方相变的边界，即准同型相界，已经成为制备高性能压电材料的基本方法。然而，尽管准同型相界被广泛应用，压电材料的铁电三方-四方相变过程及准同型相界处反常压电性能的产生机理目前并不完全清楚。本项目以目前应用最广泛的PZT基压电陶瓷为研究对象，利用正电子湮没谱学技术从微观缺陷的角度研究陶瓷的铁电三方-四方相变过程以及缺陷对准同型相界处电性能的影响。通过对不同体系、不同形态（块体和薄膜）的陶瓷在组分和温度诱导的铁电三方-四方相变过程中微观缺陷的演化行为以及准同型相界处缺陷结构随时间的变化行为的研究，得到PZT基压电陶瓷准同型相界处微观缺陷的演化特征，并与材料宏观压电、介电、铁电性能随组分、温度、时间的变化关联起来，进而阐释材料准同型相界处反常压电性能的产生机理。本项目的研究结论有望推广到其他压电材料体系，为高性能压电材料的开发提供物理指导依据。

使材料的组分位于铁电三方（或三角）-四方相变的边界，即准同型相界，已经成为制备 高性能压电材料的基本方法。从微观缺陷的角度深入系统地研究压电材料的铁电三方-四方相变过程以及缺陷对准同型相界处电性能的影响，对高性能压电陶瓷的制备具有重要意义。本项目利用固相反应法制备了纯钙钛矿相的PZT、PMN-PZT（包含xPMN-(1-x)PZT44/56和0.2PMN-0.8PZTx/(1-x) ）陶瓷，利用正电子湮没寿命谱和符合多普勒展宽能谱研究了室温下缺陷随组分和时间的变化行为以及温度在20K-300K范围内改变时缺陷随温度的变化行为，对各体系陶瓷的介电、压电性能进行表征，讨论了缺陷对电学性能的影响，总结了准同型相界附近缺陷的特征。此外，还运用第一性原理分析了PMnN-PZT(50/50)的介电和压电性质随PMnN含量的变化，并在Si基衬底上制备了PMnN-PZT(50/50)薄膜，分析了薄膜的电学性能。