共掺杂钙钛矿基巨介电材料性能调控及其巨介电机理研究

 Ceramic capacitors are important energy storage components for microelectronic and power electronic systems. Dielectric materials with high dielectric constant, low loss and high breakdown voltage are urgently needed for high energy density capacitors for system minimization and integration. To build giant dipoles by co-doping was a proved strategy for developing ceramic materials with colossal dielectric constant and low dielectric loss. However, it is still frustrating in fabricating colossal dielectric constant materials with low loss through co-doping method because the dielectric performance of a material is always the overlap of several polarization mechanisms. There also has no clear model about how the giant dipoles created from co-doping exist in the materials and what’s their fingerprint under the outside field. This proposal will focus on the colossal dielectric constant materials based on co-doping strategy and try to clarify the above concerns...Since perovskite type compounds containing [TiO6] units can provide much larger space than the rutile TiO2 for doping and for dielectric properties tailoring, perovskite type ATiO3 with different A site elements will be used as the base materials for colossal dielectric constant materials fabrication. The co-doped ATiO3 ceramics will be prepared by conventional solid state reaction and then by high temperature sintering. The trend of dielectric properties variation with co-doping elements and A site elements will be investigated, and some clues on how to build the giant dipoles in materials is expected to be found out. Ultra-wide band dielectric spectra with frequency up to GHz or higher will be measured in a wide temperature range. These wideband experimental data will be analyzed based on Debye equation, Koop’s equivalent circuit model and universal dielectric theory to find out the direct proof of giant dipoles in materials and to clarify the dielectric characteristics of the giant dipole polarization. ..Considering the very low breakdown strength of the reported colossal dielectric constant ceramics, efforts will also be taken to improve the breakdown strength of the colossal dielectric constant materials by crystal lattice tailoring and grain boundary modification. High performance dielectric ceramics with colossal dielectric constant, low dielectric loss, high breakdown strength, wide temperature and frequency stability will be obtained, which will be the strong base for developing high energy density ceramic capacitors.

陶瓷介质电容器是微电子及电力电子系统不可或缺的储能元件，发展高介电常数、低介电损耗的陶瓷电介质材料是电子系统小型化、集成化的迫切需求。通过共掺杂构建自由电子高度局域化的大偶极子是获得低损耗巨介电材料的可行途径并受到广泛关注，但这种大偶极子形成的条件、极化效应的微观机制和宏观物理特征等都还不清楚。本项目将以含有[TiO6]结构基元的钙钛矿结构ATiO3为基质，通过共掺杂来制备新型巨介电陶瓷材料；通过比较不同A位元素和Ti位掺杂所得材料的介电性能，探索共掺杂型巨介电材料中大偶极子的形成条件；通过宽温宽频介电性能测试、介电理论模型分析以及微结构分析，阐明共掺杂型巨介电材料巨介电效应的根源和微观机制；通过微观和介观尺度改性来改善巨介电材料的耐压特性，从而获得低介电损耗、高耐压强度、宽温度和频率稳定性的巨介电陶瓷材料。本项目研究将为高性能巨介电材料及高储能密度电容器的研制奠定科学和技术基础。

陶瓷介质电容器是微电子及电力电子系统不可或缺的储能元件，发展高介电常数、低介电损耗的陶瓷电介质材料是电子系统小型化、集成化的迫切需求。本项目自2016年开始执行以来，完成了项目计划的研究内容，通过不同体系基体材料的系统研究，对共掺杂型巨介电材料产生的机制有了更深入的认识。围绕共掺型巨介电介质材料巨介电性能起源问题，分别以BaTiO3、SrTiO3、LaGaO3、ZnO等不同类型的氧化物为基体材料，通过In-Nb、Al-Nb、Ga-Nb、Li-Nb等元素的复合共掺杂，获得了一系列具有巨介电特性的陶瓷材料；通过介电温谱、介电频谱、交流阻抗谱、元素价态和缺陷状态等的表征和分析，以及不同材料体系巨介电特性的比较，认为共掺体系同都存在钉扎电子-缺陷偶极子存在，同时晶界层效应、界面极化效应和变程电子跃迁效应等都对共掺体系材料的巨介电效应有贡献。不同材料体系的比较也表明，在共掺杂型巨介电材料中很难获得单一机制的巨介电材料，提高钉扎电子-缺陷偶极子效应在巨介电效应中的贡献有利于降低介电损耗，提高巨介电性的频率及温度稳定性。通过本项目研究获得了介电常数~10000，介电损耗小于0.05的巨介电介质陶瓷材料，该类材料具有良好的频率和温度稳定性，通过进一步的改性，该类材料将在陶瓷电容器的小型化、高容量化等领域有广泛的应用。本项目对几种不同基质材料巨介电效应机理研究的结果也对新型巨介电介质材料的研究开发有重要的借鉴意义。