高性能KNN基无铅压电陶瓷的相结构设计与温度稳定性调控

Although piezoelectric materials have been in commercial use for a long time, the development never ceases during the last few decades. One of the most concerning subjects is searching for lead-free counterparts to substitute the widely used lead zirconate titanate ceramics, which are not environment-friendly. The breakthrough on textured (K, Na)NbO3 (KNN) based ceramics with co-dopants of Li, Ta, and Sb has made a significant impact on the development of lead-free piezoelectric ceramics. In recent years, tremendous studies have been devoted to KNN-based ceramics with emphases on property enhancement by optimizing sintering processes and compositional modifications. However, it seems that the present situation could not fully qualify KNN-based ceramics as a successful alternative for PZT, due to several drawbacks, one of which is the poor thermal stability. Several methods have been propsed for conquring this issue, while it still annoys the community that high piezoelectric properties and decent thermal stability could not be achived simutaneously. The current proposal considers a noval solution for this problem, which takes account of orthorthombic-tetragonal coexsitence as a guarantee for enhanced piezoelectric activity. Based on this designation, temperature-insensitivity may be reallized by means of phase structure engineering. The latest result shows that optimal CaZrO3 doping is quite effective. It is scheduled that the effect of CaZrO3 on both phase structure and thermal stability will be analysed at first. Then comprehensive investigations will be carried out on KNN-based ceramics modified by various dopants, resulting in general understanding of connections between phase structure and thermal stabiliy. The influence of external stimulations and microstructure will also be investigated. It is expected that the current effort will shed light on development of qualified lead-free piezoceramics.

基于环境保护的迫切要求，高性能(K,Na)NbO3（简称KNN）基无铅压电陶瓷的研发引起了人们极大的兴趣。许多研究者指出，在该体系中难以同时获得高压电活性与较好的温度稳定性。我们最近的研究发现，掺杂适量CaZrO3可以使KNN陶瓷的压电常数d33在室温条件下达到320～360pC/N，并且其场致应变在室温至175摄氏度的宽温度范围内变化率小于10%。本课题计划探索CaZrO3含量影响相结构变化及铁电压电性能、温度稳定性的内在作用机理，获取通过相结构设计调控KNN基陶瓷温度稳定性的可行性原则。在此基础上，系统研究不同掺杂元素或化合物改性的KNN基陶瓷的相结构与物理性能，力图得到该体系相结构特征与温度稳定性关联的规律。此外，还将积极探索外加电场、力场调控及微观形貌结构与温度稳定性的联系。这些工作将为KNN基无铅压电陶瓷材料的综合性能优化及进一步发展提供必要的实验基础。

压电材料可实现电能和机械能的相互转换，传感器、驱动器和换能器等各种电子元器件方面有着广泛地应用。目前大量使用的压电材料主要是含铅体系。然而，基于环境保护的迫切要求和应对可能随时到来的无铅化变革对我国压电产业造成的巨大影响，研究具有高压电活性和温度稳定性的无铅压电陶瓷具有重大意义。申请人及团队围绕项目计划书中的四个研究内容，开展了一系列的研究，基本实现了研究目标：（1）在CaZrO3掺杂的KNN压电陶瓷中研究了CaZrO3对陶瓷疲劳性能、温度稳定性的调控机理，以及如何通过优化极化温度提高压电性能；（2）研究了MPB相结构和R-T共存相结构在获得高温度稳定性陶瓷中的重要作用以及对KNN基陶瓷温度稳定性的影响规律；（3）发现了受外电场调制的弥散性相转变对KNN基陶瓷温度稳定性的影响规律；（4）通过改变烧结制度，使用多种烧结工艺，在一定范围内调控KNN基陶瓷的微观结构，并利用压电力显微镜等表征手段探索微观结构与温度稳定性的关联。在Advanced Functional Materials和Acta Materialia等期刊发表SCI论文15篇，获得授权发明专利1篇。