B位1:2有序的Ba(B'1/3B''2/3)O3复合钙钛矿因其优异的微波介电性能和丰富的微结构特征而受到了广泛关注，是一种极具商业化应用前景的低损耗微波介质陶瓷。而其超低损耗化的实现是推进其实用化需解决的关键难题。本项目在对有序度认识的基础上，拟从有序畴尺寸和有序畴界特征两方面揭示Ba(B'1/3B''2/3)O3复合钙钛矿的有序畴结构演化及对微波介电性能的影响规律。将建立与有序畴尺寸相关的介电损耗物理模型，获得超低损耗Ba(B'1/3B''2/3)O3复合钙钛矿的最佳有序畴尺寸；同时，通过透射电镜对不同有序畴界的静态特征和动态演化展开深入研究，揭示有序畴界特征对微波介电性能的影响规律及其物理机制。最终，通过优化制备工艺，调控其有序畴结构与畴界结构，进而实现超低损耗化。本项目的实施将为超低损耗微波介质陶瓷的结构-性能调控提供指南，并为新材料设计奠定理论基础。

The B-site ordered Ba(B'1/3B''2/3)O3 complex perovskites which exhibit excellent dielectric properties and rich microstructural features, have received extensive attentions as low loss microwave dielectric ceramics with great commercial application prospect. However, the realization of ultra-low loss is the key issue to promote their practical applications. On the basis of the preliminary understanding about the cation ordering degree of Ba(B'1/3B''2/3)O3 complex perovskites, this proposal mainly from two aspects of the ordering domain size and the ordering domain boundary, to clarify the structure evolution rule and the corresponding effects on microwave dielectric properties. A physical model about the relation between dielectric loss and ordering domain size will be established to conclude the optimum domain size for Ba(B'1/3B''2/3)O3 complex perovskites. Meanwhile, the static characteristics and dynamic evolution of ordering domain boundary will be systematically investigated by transmission electron microscope to reveal the influence of domain boundary on dielectric loss and the underlying physical mechanism. Accordingly, the ultra-low loss of Ba(B'1/3B''2/3)O3 can be realized by tailoring the ordering domain structure and domain boundary, which is obtained by optimizing the preparation process. This proposal will be instructive for the structure-performance tailoring of ultra-low loss microwave dielectric ceramics, and also lay a theoretical foundation for the new material design.