基于弛豫性调控的KNN基无铅透明压铁电陶瓷的组成设计、微观缺陷与电光性能研究

The lead-free transparent piezoelectric ceramics play a crucial role in the future development of optical computer technology, modern advanced technology and national defense. In order to achieve high transmittance and excellent electric properties in piezo-ferroelectric materials simultaneously, the composition design in this project is mainly dominated by regulating the relaxor behavior associated with theoretical calculation. Then the crystal structure of the composition can be located at the coexistence of tetragonal and cubic phase or pseudo cubic phase through adjusting the A and B-site ions, adding the second phase and other means. It is anticipated the submicron powders of KNN-ABO3 will be prepared by solid state method, high energy ball milling method and the sol-gel method, respectively. The growth of ceramic grains can be effectively controlled by two-step sintering and hot pressing sintering. Furthermore, the effects of the process parameters on the microstructure, defects (grain boundary, porosity, vacancy, second phase) and the transparency of the materials will be explored in detail. Finally, KNN-based ceramics with high density and prior electro-optical performance can be obtained by optimizing the preparation parameters. The introduction of special advanced characterization technologies will help us to further reveal the physical mechanisms of transparency, determine the fundamental discipline for the composition design, and realize the adjustment of transparency and electrical properties of the transparent lead-free KNN-based piezo-ferroelectric ceramics. This project will not only focus on a new preparation technology of the transparent lead-free piezo-ferroelectric ceramics but also enrich the theory of the transparent lead-free piezo-ferroelectric ceramics, and especially, provide a new candidate and technology support for the applications of the transparent lead-free piezo-ferroelectric ceramics.

无铅透明压铁电陶瓷是未来光计算机技术、电子信息技术和国防军事应用开发中的关键材料。基于透光性和压铁电性这一对矛盾特性是制约透明压铁电陶瓷发展的关键瓶颈，本项目提出拟采用引入第二组元及A、B 位离子取代并结合理论计算，调控材料的弛豫性使其组成处于四方-立方相共存或伪立方相为设计思想，以促进这一对矛盾达到合理平衡；基于控制陶瓷微观缺陷，减少晶界处光散射，以提高透光性的思路，拟采用高能球磨法和溶胶-凝胶法制备高活性的KNN-ABO3亚微米粉体，经真空或热压烧结等工艺控制陶瓷的晶粒生长，研究工艺参数对陶瓷微观结构和缺陷（晶界、气孔、空位、杂相）及陶瓷透光性的影响规律，系统探讨陶瓷晶体相结构、微观缺陷等因素对陶瓷透光性和压铁电性能之间的关联性，揭示透光性的物理机制，提出无铅透明压铁电陶瓷的组成设计原则，实现透光性与电性能的主动调控，建立无铅透明压铁电陶瓷的制备新技术，为实际应用提供新材料和技术支持。

本项目选择具有无铅钙钛矿结构的K0.5Na0.5NbO3（KNN）作为研究对象，开展了KNN陶瓷的微观结构和相结构、透明性和压铁电性能的研究。首先，采用传统固相反应法和高能球磨法制备了纯K0.5Na0.5NbO3 (KNN)陶瓷，优化了制备工艺参数，并结合第一性原理计算进行研究。其次，通过引入第二组元制备了具有伪立方结构的KNN基透明陶瓷，系统研究了相结构对陶瓷透明性和电学性能的影响，陶瓷的透明性明显提高；同时系统研究了晶粒尺寸和KNN陶瓷透明性之间的关系，提出亚微米、纳米尺寸晶粒能有效地减少晶界处双折射，是提高各向异性陶瓷透明性的重要手段。最后，通过化学组分设计同时调控陶瓷的微观结构（如晶粒尺寸、气孔）和相结构，深入研究了KNN陶瓷的微观结构、相结构、透明性和电学性能，提出了实现KNN基陶瓷透过率和压电性能协同调控的一种新思路，最终制备出同时具有高透明性和高压电性的KNN基透明陶瓷。发表SCI源期刊40篇(标注），获授权专利8个。培养毕业博士生3名，毕业硕士研究生7名。