Preparation And Properties Of High Pressure Zinc Oxide Varistor Ceramics

With the entry of human society into the power era,the safety and stability of circuit system operation has become the basis for human life and industrial production.At this time,varistor ceramic materials as a good over-voltage protection and electronic components for absorbing surge current gradually attracted the attention of researchers.Entering the electronic age,the application fields of varistor ceramic materials are further broadened,from household appliances,automotive circuits to transportation circuit systems,communications,etc.,to ensure the safe operation of residents'lives and industrial production.Therefore,the development of varistor ceramic materials with excellent nonlinear characteristic properties,high potential gradient and low leakage current has become one of the research hotspots.At present,the most widely used ZnO-Bi₂O₃ varistor ceramic material has the advantages of low preparation cost and excellent performance,which makes it stand out among many pressure sensitive materials.At present,domestic and foreign research scholars have made the improvement of the pressure-sensitive properties of varistor ceramic materials as the research focus,and achieved remarkable results.Among them,the varistor ceramics prepared by researchers in Japan and other countries have the best performance,and the comprehensive electrical properties of the prepared ZnO varistor ceramic materials are at a relatively high level.However,the gap between domestic manufacturers and foreign countries is more obvious.While improving the potential gradient,the effect of improving nonlinear characteristics is not obvious.Therefore,improving the comprehensive electrical properties of varistor ceramic materials is the key to preparing varistor ceramics with excellent performance.In this paper,ZnO varistor ceramics were prepared by doping with rare earth elements Pr₆O₁₁,Sm₂O₃ and Sm₂O₃-SiO₂.The effects of doping amount and sintering temperature on the density,potential gradient,nonlinear coefficient and leakage current of varistor ceramics were investigated..The results are as follows:?1?Bi₂O₃ and Pr₆O₁₁1 binary varistor ceramics were prepared by doping Pr₆O₁₁1 in ZnO varistor ceramics.The doping of Pr₆O₁₁1 improved the electrical properties of ZnO varistor ceramics,but the improvement effect was very limited.The varistor ceramics sintered by doping with 0.5 mol.%Pr₆O₁₁1 at 1100?had a radial shrinkage of 18.9%,a thickness shrinkage of 17.9%,a density of 99.5%,a potential gradient of 568 V/mm,and a nonlinear coefficient of 53.6.The leakage current is 0.58 uA.?2?The doping of rare earth element Sm₂O₃ improves the varistor properties of ZnO varistor ceramics better than that of Pr₆O₁₁.The varistor characteristics of ZnO varistor ceramics are optimized by doping with 0.3 mol.%Sm₂O₃ and sintering temperature of1100?.The radial shrinkage was 19.2%,the thickness shrinkage was 17.7%,the density was 99.6%,the potential gradient was 633 V/mm,the nonlinear coefficient was 58.4,and the leakage current was 0.43 uA.?3?The further introduction of SiO₂ on the basis of Sm₂O₃ optimal doping has a significant improvement on the nonlinear characteristics of ZnO varistor ceramics,and the relative potential gradient of Zn₂SiO₄ spinel is further improved.When the doping amount of SiO₂ is 0.6 mol.%and the sintering temperature is 1100?,the comprehensive performance of varistor ceramics is optimal.At this time,the radial shrinkage of the ceramic was 19.7%,the thickness shrinkage was 18.1%,the density was 99.8%,the potential gradient was 752V/mm,the nonlinear coefficient was 73,and the leakage current was 0.22 uA.