Srn+1TinO3n+1 (n=1,2)基陶瓷的氧八面体扭转机制及微波介电性能调控

Dielectric materials with Ruddlesden-Popper structure have received extensive attention due to their significant application prospects in microwave communication systems. This proposal will focus on the tilting mechanism of oxygen octahedron in Srn+1TinO3n+1 (n=1,2) based materials along with its effects on the evolutions of microwave dielectric properties. The relations between structural parameters and dielectric responses, especially the effects of octahedral tilting on the temperature coefficient of resonant frequency and intrinsic dielectric loss will be emphasized. Meanwhile, the interlayer mismatch, atomic distribution and the corresponding microstructure will be systematically investigated by transmission electron microscope to reveal the influence of stacking faults on the dielectric loss and the underlying physical mechanism. Accordingly, the optimizations of microwave dielectric properties are expected by comprehensive structure and microstructure tailoring. This proposal will improve the structure-performance tailoring theories of Ruddlesden-Popper structured microwave dielectric ceramics, and also be instructive for the new material design.

具有Ruddlesden-Popper层状结构的电介质材料由于其微波通讯应用的诱人前景而获得广泛关注。本项目拟选取Srn+1TinO3n+1 (n=1,2)基陶瓷为研究对象，系统研究结构中氧八面体扭转机制及其对微波介电性能的影响规律。项目重点探讨宏观介电响应与本征结构参数的协同关系，特别是氧八面体扭转对谐振频率温度系数和本征介电损耗的调控规律。同时，通过透射电镜观察Srn+1TinO3n+1结构中氧八面体扭转与层间失配程度、层间原子分布和由此产生的微结构特征，解析堆垛缺陷形成的物理机理及其对微波介电性能的影响。最终，在掌握组分设计与结构综合调控规律基础上实现Srn+1TinO3n+1基陶瓷微波介电性能的协同优化。本项目的实施将有力地补充Ruddlesden-Popper型微波介质陶瓷的结构-性能调控理论，并为新材料的设计提供指南。

钙钛矿结构由于其优异的结构通融性和可调性而获得广泛关注，然而层状钙钛矿中结构与性能的调控关系仍有待研究。本项目着眼于Srn+1TinO3n+1 (n = 1, 2)基微波介质陶瓷，借鉴钙钛矿体系结构调控理念，探索其微波性能优化途径。项目重点研究了宏观介电响应与本征结构参数的协同关系，特别是氧八面体扭转对谐振频率温度系数和本征介电损耗的调控规律。项目取得的重要成果如下：1）在n=1型Sr2TiO4结构中通过B位Sn置换调控许容因子成功诱导氧八面体扭转并调节τf值近零，确定了相转变的临界结构参数，结合微波介电性能的演变规律构建了许容因子对τf值调控的物理模型。2）揭示了在n=2型Sr3(Ti1-xSnx)2O7陶瓷中许容因子调控晶体结构的演变过程，构建了结构本征参数-微观晶体结构-宏观介电性能的协同关系，通过红外反射光谱理清了本征结构参数与其本征介电性能的对应关系。3）在Srn+1TinO3n+1结构中设计B位(Mg, Nb)协同置换，分析了不同n值条件下陶瓷物相组成、氧八面体扭转机制、结构稳定性调控及其微波介电性能。本项目的实施有效地完善了Srn+1TinO3n+1基微波介质陶瓷的材料设计及结构、性能调控机理，为新型微波介质材料的开发设计提供了理论指导。