CTLA微波介质陶瓷性能优化与微结构调控机理研究

Microwave dielectric ceramics with high quality factor and near-zero temperature coefficient of resonant frequency were required to meet the need of miniaturization, integration and high performance of microwave dielectric filters. In this project, firstly CaTiO3-LaAlO3（CTLA）ceramics were prepared by conventional solid-state reaction, the effects of A/B site ionic parameters on the electron structure and defect distribution were investigated, and mechanisms of polarization and dielectric loss were elucidated. Secondly, the electron structure, density of state and lattice vibration modes were calculated by first-principle, the impacts of ionic parameters on the vibrational frequency were revealed.The correlation between the microstructure, lattice vibration modes and the microwave dielectric properties of this three were established, and the inner link between the ionic polarization states and energy band structures and electron structures rere explored. Finally CTLA ceramics with different dopants were designed to tailor the microwave dielectric properties, the influences of the interface electronic structure and density of state on the microwave dielectric properties were discussed, and the energy band engineering was employed to reveal the mechanism of energy bands adjust and control, which provides theory evidence and experimental guidance for the design of microstructure and the energy bands tailoring and the optimizing of the microwave dielectric properties. The implementation of this project has a great significance in promoting the development and application of high performance microwave dielectric ceramic materials.

微波介质滤波器的小型化、集成化及高性能化发展方向要求微波介质陶瓷材料具有更高的品质因数和近零的谐振频率温度系数，本项目拟以CaTiO3-LaAlO3（CTLA）陶瓷为研究对象，采用固相反应法制备CTLA陶瓷，研究A/B位离子参数对陶瓷电子结构、缺陷态分布的影响，探讨陶瓷的极化和损耗的微观机理；应用第一性原理计算CTLA陶瓷电子结构、态密度分布、晶格振动模式，探讨掺杂离子参数对晶格振动频率的影响，建立陶瓷微结构、晶格振动模及其介电性能三者之间的关联和离子极化状态与能带结构和电子结构的内在联系。设计不同离子掺杂微波介质陶瓷体系，研究界面电子结构和态密度对CTLA陶瓷宏观介电性能的影响规律，揭示陶瓷能带调控的物理机理，为精确设计及控制材料的能带结构、微观结构和宏观介电性能提供理论依据和实验指导。本项目的研究与实施对于高性能微波介质陶瓷材料的研发与应用具有极大的推动作用和重要的科学价值。

为适应微波介质滤波器的小型化、集成化及高性能化要求，项目围绕高、中、低介微波介质陶瓷材料体系进行研究，开发了εr = 110.6 的(1-x)CaTiO3-x(Li0.5Sm0.5)TiO3、εr =80的Ba4Nd9.33Ti18O5陶瓷、εr =45的CaTiO3-LaAlO3和εr 为20左右的MgTiO3-CaTiO3和Li2TiO3–Li3Mg2NbO6等陶瓷体系。探索了低熔点、高Q×f值的复合烧结助剂（（BLA和BBSZ）在高、中、低介微波陶瓷体系中的应用，针对不同体系成功将烧结温度降低了300-500℃，建立了烧结理论模型，揭示了液相烧结的物理机制。设计并开发了 (1-x)CaWO4-x(Li0.5Sm0.5)WO4、Li4NbO4F等低温烧结陶瓷材料，实现了低于950℃低温烧结、Q׃值>30000 GHz，并实现了与Ag电极共烧，可广泛应用于LTCC材料体系。研究了陶瓷密度、晶粒大小、晶格常数和结构有序度等微结构特征参数对陶瓷微波介电性能的影响，建立了微结构特征参数与微波介电性能的关联；研究了离子极化率、键价、容忍因子等微电学特征参数对陶瓷微波介电性能的影响，揭示了它们与陶瓷微波介电性能的关联，总结了微波介电性能的调控规律。应用四参数半定量模型结合远红外光谱分析，计算了CaTiO3-(Li0.5Sm0.5)TiO3陶瓷的晶格振动模式，研究了振动模式和结构有序度对陶瓷微波介电性能的影响机制，揭示了在钙钛矿结构中A位离子振动模式对介电常数的巨大贡献。应用远红外反射光谱得到了本征介电常数与介电损耗，建立晶格振动模式、频率与离子极化和介电性能的关联，为微波介质陶瓷性能优化与微结构调控提供理论指导。测试了Ba4Nd9.33Ti18O54微波陶瓷中Ti原子的价态分布，揭示了Ti原子电子结构变化对微波介电性能的影响；计算了Zn2TiO4晶体结构中的态密度，研究了态密度对微波陶瓷宏观介电性能的影响，揭示了Ti－O键和Zn－O键对微波陶瓷性能调控的物理机理，为精确设计及控制材料的能带结构和宏观介电性能提供理论依据和实验指导。项目拓展了介质滤波器的设计仿真工作，利用 ADS 和 HFSS 软件实现了全介质、金属介质混合及双模介质滤波器设计，其技术参数均达到5G通信用技术指标。项目研究期间发表论文18篇，申请发明专利1项，项目成果对于高性能微波介质陶瓷材料的的研发与应用