当前，具有优异储能特性的电介质电容器向着集成化与多功能等方面发展，其相应电介质材料的储能密度也因此被提出了更高的要求。铌酸银(AgNbO₃)是当前最有潜力的无铅反铁电材料之一，但因固有的回滞效应与铁电相的存在，导致其储能特性不能满足储能器件的工作要求。本论文通过水热法工艺获得了离子掺杂型AgNbO₃基陶瓷材料，并对掺杂后的AgNbO₃基陶瓷进行核壳结构的构筑，系统地探究了离子掺杂改性和核壳结构构筑对AgNbO₃基陶瓷材料介电性能、阻抗性能以及储能性能的影响。在改善优化AgNbO₃陶瓷储能性能的基础上，以促进在电介质电容器方面的应用。

采用水热法制备出粒径大小平均约为260~280 nm左右的AgNbO₃基陶瓷粉体颗粒，而针对AgNbO₃的A位Ag⁺离子，采用了异价A位的Y³⁺进行掺杂取代。相较于原A位的Ag⁺，Y³⁺由于更小的离子半径不仅降低了体系的容差因子，还增强了体系的反铁电相稳定性，同时对应的介电测试结果也证实了铁电相-反铁电相在室温下趋于稳定。基于第一性原理计算的Y³⁺掺杂AgNbO₃电子结构的带隙宽度由1.959 eV减小至1.746 eV，这归结于异价的A位掺杂产生了施主能级，导致电子更容易被激发。

针对AgNbO₃的B位调控，采用非铁电活性的Ta⁵⁺取代了铁电活性的Nb⁵⁺，以此降低体系的铁电性，从而提高反铁电稳定性。同时基于密度泛函理论所得的能带结构、态密度与光学介电函数分析了B位Ta⁵⁺掺杂对AgNbO₃电子结构的影响。结合微结构、介电与铁电测试的结果发现，Ta⁵⁺掺杂的AgNbO₃不仅晶粒尺寸由3.35 µm减小到2.74 µm，还具有更加稳定的反铁电相。在Ta⁵⁺的掺杂量x=0.05时，AgNb_0.95Ta_0.05O₃陶瓷在225 kV/cm的电场下储能密度从1.94 J/cm³提高到了3.67 J/cm³。

为了进一步提高AgNbO₃的储能性能，在Ta⁵⁺掺杂AgNbO₃的基础上制备了具有核壳结构的AgNb_0.95Ta_0.05O₃@SiO₂陶瓷材料，其中以非晶相的无定型SiO₂作为壳，而AgNb_0.95Ta_0.05O₃则是核结构。SiO₂作为壳结构，一方面可以抑制晶粒大小的生长，另一方面其独特的壳层结构提高体系的耐击穿特性。具有核壳结构的AgNb_0.95Ta_0.05O₃@5wt.%SiO₂陶瓷不但具有较低的介电损耗值，而且实现了3.94 J/cm³的储能密度和72.64 %的储能效率。这项工作为设计具有高储能性能的AgNbO₃基无铅反铁电陶瓷材料提供了研究思路与技术参考。

Currently, dielectric capacitors with excellent energy storage characteristics are developing toward integration and multi-function, and the energy storage density of their corresponding dielectric materials is therefore put forward to higher requirements. Silver niobate (AgNbO₃) is one of the most potential leadless antiferroelectric materials at present, but due to the inherent hysteresis effect and ferroelectric phase, its energy storage characteristics can not meet the requirements of energy storage devices. In this thesis, ion-doped AgNbO₃-based ceramic materials were obtained by a hydrothermal process, and the core-shell structure of the doped AgNbO₃-based ceramics was constructed to systematically investigate the effects of ion-doping modification and core-shell structure construction on the dielectric properties, impedance properties, and energy storage properties of AgNbO₃-based ceramic materials. On the basis of improving and optimizing the energy storage properties of AgNbO₃ ceramics in order to promote the application in dielectric capacitors.

The AgNbO₃-based ceramic powder particles with an average particle size of about 260~280 nm were prepared by hydrothermal method, while Y³⁺ at the heterovalent A-site was used to dope and replace the Ag⁺ ion of AgNbO₃. Compared with the original A-site Ag⁺, Y³⁺ not only reduces the tolerance factor of the system due to its smaller ionic radius, but also enhances the stability of the antiferroelectric phase of the system, while the corresponding dielectric test results also confirm that the ferroelectric-antiferroelectric phase tends to be stable at room temperature. The band gap width of the Y³⁺-doped AgNbO₃ electronic structure calculated based on the firs principle is reduced from 1.959 eV to 1.746 eV, which is attributed to the fact that the heterovalent A-site doping generates the sender energy level, resulting in easier excitation of the electrons.

For the B-site modulation of AgNbO₃, the non-ferroelectric active Ta⁵⁺ was used to replace the ferroelectric active Nb⁵⁺ in order to reduce the ferroelectricity of the system and thus improve the antiferroelectric stability. The effect of B-site Ta⁵⁺ doping on the electronic structure of AgNbO₃ was also analyzed based on the energy band structure, density of states and optical permittivity function obtained from density generalized theory. Combining the results of microstructure, dielectric and ferroelectric tests, it is found that the grain size of Ta⁵⁺-doped AgNbO₃ is not only reduced from 3.35 µm to 2.74 µm, but also has a more stable antiferroelectric phase. The energy storage density of AgNb_0.95Ta_0.05O₃ ceramics increased from 1.94 J/cm³ to 3.67 J/cm³ under an electric field of 225 kV/cm at a Ta⁵⁺ doping amount of x=0.05.

In order to further improve the energy storage performance of AgNbO₃, AgNb_0.95Ta_0.05O₃@SiO₂ ceramic materials with core-shell structure were prepared on the basis of Ta⁵⁺ doping AgNbO₃, in which amorphous SiO₂ was used as shell, and AgNb_0.95Ta_0.05O₃ was used as nuclear structure. SiO₂ as shell structure, on the one hand, can inhibit the growth of grain size, on the other hand, its unique shell structure can improve the breakdown resistance of the system. The AgNb_0.95Ta_0.05O₃@5wt.%SiO₂ ceramics with core-shell structure not only have low dielectric loss value, but also achieve 3.94 J/cm³ energy storage density and 72.64 % energy storage efficiency. This work provides a research idea and technical reference for the design of AgNbO₃-based lead-free antiferroelectric ceramics with high energy storage performance.