巨介电常数功能陶瓷材料的缺陷形成机制及性能调控研究

This project is to research on the defect formation mechanism and electrical properties of functional ceramics with giant dielectric constant. ACu3Ti4O12（A＝Ca,Sr,Ba）-based nano-size powders, dielectric ceramics and thin films, respectively, will be fabricated by using sol-gel method, self-propagating combustion synthesis, ceramic process and electrophoretic deposition (referred to as EPD) technologies etc. The effcts of phases, compositional distribution, microstructures on dielectrical properties as well as the electrical conductivity at high temperature will be investigated systematically, to understant the mechanism of grain semiconducting and grain-boundary isolating. According to experimental results, a model of defect formation will be proposed to reasonably explain the dielectric origin of complex-perovskite materials. The porous structure of ACu3Ti4O12 materials will be self-assembled by hydrothermal synthesis and template techniques. By controlling the microstructure of grains and grain boundaries, ACu3Ti4O12-based semiconducting materials with different electrical conductivity will be prepared and their corresponding gas sensing and the photocatalytic features will be researched. Furthermore, the preparation and properties of ACu3Ti4O12 composited with other functional materials will be investigated to extend the application of such materials and achieve results with independent intellectual property rights.

拟开展巨介电常数功能陶瓷材料缺陷的形成机制及其性能调控相关的研究。采用溶胶-凝胶法、自蔓延燃烧合成、陶瓷工艺及电泳沉积（简称EPD）技术等分别制备ACu3Ti4O12（A＝Ca,Sr,Ba）基纳米粉体，介电陶瓷及薄膜材料。系统研究材料的相结构、组分分布、显微结构等对材料介电特性的影响，并结合高温电导研究，掌握调控晶粒半导化和晶界绝缘性的机理和工艺，揭示缺陷与性能之间的相关性，建立缺陷形成机制模型，合理解释其介电起源。通过调控晶粒和晶界的微结构，获得不同导电特性的ACu3Ti4O12基半导体材料，并采用自组装技术制备多孔结构粉体及薄膜，研究其相应的气敏和光催化性能。此外，与其它功能材料进行复合及掺杂、改性，充分发挥ACu3Ti4O12 基电介质材料的优点，进一步拓展其相关性能及应用，形成具有自主知识产权的成果。

本项目执行期间，系统开展了复合钙钛矿结构ACu3Ti4O12（A＝Ca,Sr,Ba）纳米粉体、薄膜、厚膜及陶瓷材料的制备、微结构分析与表征、电学性能及机理等的相关研究。通过四年的努力，掌握了获得纳米级及微米级纯相ACu3Ti4O12（A＝Ca,Sr,Ba）的工艺方法，并以合成的粉体材料为原料，通过优化工艺及调控晶粒、晶界导电特性，分别制备得到了具有巨介电常数的电介质陶瓷、压敏电阻、热敏电阻等材料。基于制备工艺、微结构及性能的相关性研究，提出了此类材料形成巨介电特性的机理模型，并在实践中验证了相关机理的合理性，对指导此类材料的后续研究和应用具有重要的科学意义。同时，通过结构设计，采用水热合成等技术沉积纳米氧化物对ACu3Ti4O12材料进行修饰改性，分别得到了室温下具有极高介电常数（ɛr>4x10^5, 1kHz, 室温）的电介质材料和低压（V1mA<6V/mm）压敏电阻材料。除巨介电材料外，ACu3Ti4O12系列材料将会在新型半导体元器件领域有广阔的应用前景。