ZnO压敏电阻微观结构调控与性能提升研究综述

Review on Microstructure Control and Performance Improvement of ZnO Varistors

金属氧化物避雷器是电力系统重要的过电压保护设备,ZnO压敏电阻是其核心部件。提高ZnO压敏电阻性能,不仅有利于优化现有系统的绝缘配合设计,在面对未来新能源广泛应用的新型电力系统时,也有利于提高对系统的保护能力,并促进设备小型化、紧凑化、轻量化。一直以来,人们主要按照机械混粉烧结的工艺路线,通过改进材料配方、改善烧结工艺、优化粉体制备等来提升ZnO压敏电阻的性能。这些工作对提高ZnO压敏电阻性能发挥了重要作用,但进一步提升的潜力有限。表面包覆形成的核壳结构能使ZnO压敏电阻的微观结构更加均匀,并可能在烧结过程中对ZnO压敏电阻的微观结构进行定制化的有效调控,在提升ZnO压敏电阻的性能方面有一定的潜力。因此,基于表面包覆的ZnO压敏电阻有望成为研究高性能ZnO避雷器的新途径。该文从传统机械混粉和表面包覆两种技术路线的角度对ZnO压敏电阻的微观结构调控与性能提升研究做了归纳整理,并对包覆路线下需要开展的研究工作进行了思考,希望能为相关领域的研究提供一定的参考。

As the core component of metal oxide arresters,the ZnO varistor has always been the focus of research.In the face of the new power system with the wide application of new energy in the future,ZnO varistors should not be limited to the optimization of small current characteristics.In some specific situations,the performance of varistors with high potential gradient,large flow capacity,and low residual voltage ratio is the focus of future attention.This paper summarizes the research on the microstructure regulation and performance improvement of the ZnO varistor from the perspective of traditional mechanical powder mixing and surface coating,and considers the research works that need to be carried out under the coating route,hoping to provide some references for research in related fields.For a long time,people have mainly improved the performance of the ZnO varistor by improving the material formula,improving the sintering process,and optimizing the powder preparation according to the process route of mechanical powder mixing and sintering.Based on the traditional formula,it was found that the doping of rare earth elements can effectively control the grain size,thus improving the uniformity of the microstructure and the potential gradient of the varistor.Using ultrafine powder also reduced the particle size and improved the microstructure uniformity.The new sintering techniques,such as cold sintering,flash sintering,and spark plasma sintering,can ensure the compacting of the porcelain body and reduce the sintering temperature.These new technologies have played an important role in improving the performance of ZnO varistors,but the potential for further improvement is limited.Surface coating modification technology has been tried in the research field of ZnO varistors.In the initial exploratory experiments,one or more elements were coated on the surface of ZnO by salts corresponding to their oxides to form the core-shell structure.The prepared ZnO varistor samples had a smaller grain size and narrower distribution,which was beneficial to improve the microstructure uniformity.Different from mechanical powder mixing sintering,the core-shell structure formed by cladding can form a heating mode with a specific temperature field structure on the billet with the help of the outer cladding during sintering,rather than relying on the temperature field of the furnace itself to directly act on the billet,which may have a better control effect on the structure formed by sintering.All these indicate that surface coating technology has a specific potential to improve the performance of ZnO varistors.However,as this kind of research is still in the early stage,much research is still needed on the following aspects:(1)Determine the coating element system suitable for ZnO to make the research work systematic;(2)Optimize the key process from coated powder to sheets,such as uniform dispersion of coated powder and optimization of the sintering system;(3)Sum up the coated ZnO varistor performance evolution law,providing the basis for performance control;(4)Explore the influence of microscopic parameters on the macroscopic electrical properties,give a reasonable deep mechanism from the microscopic level,and put forward an effective method to customize the performance of the ZnO varistor;(5)The calculation of ZnO surface adsorption by first principles can play a guiding role in selecting the coating body and then designing the surface coating structure.