基于缺陷调控的功能氧化物的巨介电响应和载流子输运机制研究

Colossal permittivity materials have a broad application prospect in the field of microelectronic device and high energy density storage. And colossal permittivity materials also have attracted the continuous scientific concern, due to the fascinating physico-chemical information. How to broaden the temperature and frequency stability of colossal dielectric response, reduce the loss and the leakage, improve the breakdown strength, is key to the application. In this project, functional oxide ceramics containing Ti, Sn, Fe, Co, Ni and other variable valence transition metal elements are intended as the research object, for example, TiO2 and SnO2, simple perovskite, composite perovskite, and other compounds. Relying on the micro and macro structure modulation, ion modification, defect design, the roles of microstructure, the complex phase, the equilibrium or non-equilibrium ion substitution, defect regulation, oxygen state, carrier transport on the polarization response and macroscopic electrical properties will be systematically investigated. The physical nature and structural origin of the colossal dielectric effect and the dielectric relaxation will be deeply analyzed. The approach of performance optimization will also be explored to obtain the excellent materials with high dielectric constant and low loss. Meanwhile, the mechanisms and correlation of inhomogeneous structure, interfacial relaxation, defect association, the mixed valence and content of elements, charge ordering, carrier transport and colossal dielectric response, breakdown properties can be revealed. The research can provide the theoretical and experimental basis for the application of colossal permittivity materials in a wide temperature and wide frequency range. The development and exploration of electronic components may be much propelled, such as new capacitors, memory, storage, etc.

巨介电材料在微电子及高能量密度存储等领域有广阔的应用前景，其本身也蕴含丰富的物理信息，因此备受关注。如何拓宽巨介电响应的温度频率稳定性，降低损耗与漏导，提高击穿场强，将非常关键。本申请拟以含钛、锡、铁、钴、镍等可变价的过渡金属元素的功能氧化物陶瓷为研究对象，如TiO2、SnO2、简单钙钛矿、复合钙钛矿等化合物，通过微观和宏观结构调控、离子改性、缺陷设计，系统研究微结构、复相、平衡与非平衡离子取代、缺陷调控、氧状态、载流子输运与极化响应和宏观电学特性之间的关联。进而深入分析巨介电效应和介电弛豫的物理根源，探索性能优化的途径，获得高介低损的介质。同时揭示非均匀结构、界面弛豫、缺陷缔合、元素混合价态与含量、电荷有序、载流子输运与巨介电响应、击穿特性之间的微观机制和相互联系。可为在宽温宽频范围内应用的巨介电介质材料提供新思路，从而促进新型电容、存储、储能等电子元件的发展。

本课题自2017年立项以来，围绕功能氧化物陶瓷TiO2、SnO2、钙钛矿SrTiO3、Bi0.5Na0.5TiO3、六方钙钛矿介质，通过离子掺杂改性、复相设计，系统探讨了晶体结构、微观结构与极化响应和宏观电学特性之间的关联，分析了巨介电效应和介电弛豫的物理根源。我们以金红石相TiO2、SnO2为基体，基于缺陷调控，通过施主受主联合掺杂，正如设计了(Bi0.5Nb0.5)xTi1-xO2、(Mg1/3Nb2/3)xTi1-xO2、(Al0.5Nb0.5)xSn1-xO2配方，成功制备了优异的具有巨介电特性的氧化物陶瓷。研究了其物相结构与组成的衍变机制，施主受主共掺杂对介电性能的影响，同时在宽温宽频范围内讨论了巨介电响应的物理机制。另外，基于缺陷设计和平衡取代的策略，我们合成了不同Ho含量的HoxSr1-1.5xTiO3陶瓷，详细研究了掺Ho的SrTiO3化合物的相组成演变、介电弛豫行为和缺陷偶极构造。低Ho含量掺杂的SrTiO3陶瓷可以收获巨介电效应，包括介电常数（~5000）、低介电损耗（~0.03）和稳定的频率响应。我们也合成了Ba0.6Sr0.4La4Ti4O15-CaTiO3系列陶瓷，研究了其晶体结构、微波介电特性以及TSDC行为，CaTiO3含量的增加直接促进了氧空位浓度的增加。这些研究结果可为在宽温宽频范围内应用的巨介电材料提供理论参考和实验依据。