高温度稳定的BaTiO3-Bi(Mg2/3Nb1/3)O3基弛豫铁电陶瓷结构、弛豫机理和储能研究

BaTiO3-Bi(Mg2/3Nb1/3)O3 (BTBMN) is a new system of relaxor material. BTBMN exhibits high dielectric constant, lower dielectric loss and slim hysteresis loop, which makes it promising candidate materials used for the high-capacity capacitors and energy storage ceramic capacitors. Moreover, compared with other traditional high-dielectric materials, it may exhibit excellent dielectric stability in high electric field and high temperature environment. There is still a lack of research on the relationship between structure and performance of BTBMN ceramics. The relationship between structure and relaxor behavior of BTBMN ceramics are not clear. Furthermore, the temperature stability of high polarization samples are bad, and it limits the application. BTBMN ceramics were chosen as the research object. In this proposal, we will study the relationship between the content of Bi(Mg2/3Nb1/3)O3 (BMN) and relaxor behavior, especially the relationship between relaxor behavior and phase structures together with the size of ploar nano regions (PNRs), the relationship model between relaxation behavior and BMN content will be established. Based on these experiments results, we could identify the origin of the relaxor behavior of BTBMN ceramics. The polarization evolutions with different temperatures and electric field will be studied. Considering the extrinsic polarization of PNRs superimposed on an intrinsic paraelectric background, the dielectric constants under bias electric field were fitted to a multipolarization mechanism model. The relationship model between electrical conductivity and BMN content will be established. The contribution of polarization mechanism on the energy storage performance will be studied. To the application, the optimum composition range with high energy storage density will be investigated, and the temperature stability of high polarization sample will be improved, the relationship model between energy storage property, relaxation behavior and temperature stability will be established, which is the basis of the development of the novel energy storage dielectric capacitors.

BaTiO3-Bi(Mg2/3Nb1/3)O3（BTBMN）是一类新型弛豫铁电体，具有高介电常数，低介电损耗和细电滞回线，非常适合于高容量电容器以及储能电容领域。且和其他传统高介材料相比，具有高电场和高温环境下优异的介电性能稳定性。然而BTBMN陶瓷结构和弛豫性能关系还不明确，另外高极化强度值组分温度稳定性不好等难题限制其应用。本项目从Bi(Mg2/3Nb1/3)O3成分与弛豫性能关系入手，深入研究弛豫铁电性和微观相结构及极性纳米微区尺寸之间的关系，建立弛豫性能随成分变化的规律模型，探索BTBMN弛豫性能的起源问题。研究不同温度和电场下的极化机制，区分外场下对介电常数的本征和非本征贡献，构建材料成分和电导率的关系模型，揭示极化机制对储能性能的贡献。在兼具高储能密度同时改善BTBMN陶瓷温度稳定性，建立储能性能和弛豫性能及温度稳定性的关系模型，为开发新储能电容器提供材料研究的基础。

弛豫铁电陶瓷材料Pmax高，Pr低，能量存储效率高，充放电速度快，适用于高温高压等极端环境和性能稳定，制备工艺简单成本较低，且储能密度高等优良特性，使弛豫铁电体陶瓷非常适合应用于电能存储领域、高温电容器和脉冲电容器领域，但单一的材料体系难以满足综合性能的需要。. 本研究以BaTiO3基无铅弛豫铁电体陶瓷为研究基体材料，通过掺杂低熔点电导玻璃在在较低烧结温度提升BTBMN陶瓷的击穿电场和储能性能。和Bi基化合物和其他材料复合，有效改善其BaTiO3陶瓷的弛豫铁电性，从而成功提升BaTiO3基陶瓷储能性能。通过在BaTiO3基弛豫铁电陶瓷中引入高Pmax值的Na0.5Bi0.5TiO3陶瓷，弥补了BaTiO3基陶瓷Pmax随弛豫铁电性能增强而大幅衰减的难题。使BaTiO3基陶瓷高储能性能和高弛豫铁电性可以同时兼得。尤其是在较低电场下极大提升了BaTiO3基陶瓷的储能性能，获得良好的储能性能的温度和频率稳定性，及快速充放电性能。本项目研究集中在保持高储能密度的同时，尽量提高Pmax，减小Pr，进一步加大Pmax-Pr和提高BDS两大技术难点。在兼具高储能密度的同时进一步改善BaTiO3陶瓷的介电常数温度稳定性，推动弛豫铁电陶瓷材料在储能电容器发面的开发与应用。