原位复合制备渗流型高性能铁电/介电复相陶瓷及其机理研究

Ferroelectric/dielectric composite ceramics with high dielectric tunability and low theoretical microwave loss can be applied in dielectric tunable microwave devices, such as resonator, filter and phase shifter etc., which has broad application prospects in both military and civilian. However, high microwave loss of composite ceramics caused by sintering with admixtures of ferroelectric and dielectric phases limits its application in high-frequency and high-performance devices. Aimed at this problem,this project intends to prepare ferroelectric/dielectric composite ceramics, such as BST/Mg2TiO4 and BST/Mg3B2O6 and so on, by using a sol-gel in situ process. Meanwhile, based on the respective growth-order of two phases resulting from the difference of its crystallization temperature, wrapped structure of two phases can be achived by controlling growth process. The growth mechanism in situ process will be clarified. Influence of composition, grain size and wrapped structure on microwave and dielectric tunable properties will be investigated thoroughly to establish a relationship between variations in structure and property and percolation effect. Then the interface percolative mechanism of ferroelectric/dielectric composite ceramics will be clarified and the dielectric tunable and loss mechanism of percolative composite ceramics will be revealed, which provides the foundation for the preparation of percolative ferroelectric/dielectric composite ceramics with low permittivity, high tunability and low loss and the application and investigation of high-frequency and high-performance tuable microwave devices.. The interface percolative mechanism of ferroelectric/dielectric composite ceramics will be solved as the key science problem in this project.

铁电/介电复相陶瓷具有高的介电调谐率和极低的理论微波损耗，适用于谐振器、滤波器、移相器等介电调谐微波器件，在军事和民用领域应用前景广阔。然而两相揉合烧结造成较高的微波损耗，限制了其在高频、高性能器件中的应用。针对这一问题，本项目拟用溶胶-凝胶原位复合技术制备BST/Mg2TiO4、BST/Mg3B2O6等铁电/介电复相陶瓷，并利用各自晶化温度的差异导致两相生长顺序的不同，通过控制生长工艺，实现两相包裹结构，阐明原位复合的生长机理；深入研究化学组成、晶粒尺度、包裹结构对微波、介电调谐特性的影响，建立结构及性能变化与渗流效应的对应关系，阐明铁电/介电复相陶瓷的界面渗流机理，揭示渗流型复相陶瓷的介电调谐机理及损耗机制,为研制低介电常数、大可调度及低损耗的铁电/介电复相陶瓷提供依据，为高频、高性能介电调谐微波器件的应用和研究奠定基础。本项目拟解决的关键科学问题：铁电/介电复相陶瓷的界面渗流机理。

铁电/介电复相陶瓷材料具有高的介电调谐率和极低的理论微波损耗，适用于谐振器、滤波器、移相器等介电调谐微波器件，在军事和民用领域应用前景广阔。然而两相糅合烧结造成较高的微波损耗，限制了其在高频、高性能器件中的应用。针对这一问题，本项目用溶胶-凝胶原位复合技术制备BST/MgO、BST/Mg2TiO4、BST/Mg3B2O6等铁电/介电复相陶瓷，并通过表面活性剂改性，实现BST@MgO核-壳结构，阐明了原位复合的生长机理；深入研究了原位复合制备工艺与化学组成、显微结构的关系及对微波、介电调谐特性的影响，建立了结构及性能变化与渗流效应的对应关系，阐明了铁电/介电复相陶瓷的界面渗流机理，揭示了渗流型复相陶瓷的介电调谐机理及损耗机制，获得高渗流阈值（f=0.6）的铁电/介电复相陶瓷，为高频、高性能介电调谐微波器件的应用和研究奠定基础。