Study On The Preparation,material Structure And Properties Of Alkaline Earth Metal Doped ZnO Powder And Ceramic

Among the materials for circuit overvoltage protection,modified zinc oxide occupies a dominant position.ZnO-Bi₂O₃system pressure-sensitive ceramics with excellent performance are the most widely used.But there are some of the following problems.During the sintering process,the low melting point of Bi₂O₃would cause severe volatilization of the pressure-sensitive ceramics,and the higher reactivity has a very adverse effect on the performance of the ceramics.Based on the above problems,in order to obtain ZnO ceramic materials with more stable performance,this article mainly focuses on the study of alkaline earth metal elements used in the modification of nano ZnO ceramics.The influence of alkaline earth metal elements on the structure and performance of nano ZnO varistor ceramics has been explored through a series of structural characterization and electrical performance tests.The main research results are as following:1.ZnO powders doped with different proportions of Ca were successfully synthesized by simple liquid phase method（auxiliary modifiers Co,Mn,Bi）,and ceramic samples were also smoothly prepared under high temperature sintering.The structure characterization showed that the lattice structure of ZnO was not changed by doping with Ca.With the increase of Ca doping ratio,the average particle size of the samples increased slightly.The test results of electrical properties show that as the doping amount increases from 0at.%to 3at.%,the varistor voltage of the modified ZnO ceramic sample increases from 283 V/mm to 386 V/mm.The ceramic sample with doping content of 2at.%has the highest temperature stability,and the nonlinear coefficient reaches the highest value of 47 at room temperature.2.Different proportions of Ba-doped ZnO powders materials were successfully synthesized by sol-gel method（auxiliary modifier P）,and ceramic materials were smoothly prepared by high-temperature sintering.The characterization results show that the crystals of ZnO is hexagonal wurtzite structure,but the doping of Ba can effectively inhibit the growth of crystal grains.Scanning electron microscopy of the ceramics shows that the samples have the advantages of small size and uniform morphology with few pores in the doping ratio of 4at.%-8at.%.Raman spectrum analysis shows that the maximum resistivity of the sample appears when the doping ratio is8at.%.The electrical performance test results of the ceramic samples show that the nonlinear coefficient of the ceramic sample reaches the maximum value of26.7 when the doping ratio is 4at.%,and the breakdown voltage reaches the peak value of 561 V/mm when the doping ratio is 8at.%.The overall analysis of the above properties shows that the optimal doping ratio is 4at.%.At a working frequency of 1 k Hz,the dielectric constant of the ceramic sample reached 1254 and the dielectric loss was reduced to 0.325.3.Different proportions of B-doped ZnO-BaO-based powders were successfully synthesized by the sol-gel method,and ceramic samples were also prepared.The structure test results show that the ZnO crystal has a hexagonal wurtzite structure,and the sample crystal grains are inhibited from growing as B doping.And with the increase of the doping ratio of B element,the grain sizes show a decreasing trend.Compare the electrical properties of B-doped ZnO-BaO-based ceramics with different proportions,the test results show that the E_1mAof the ceramic sample ZBO-0.02B₂O₃is 336.5 V/mm,and the nonlinear coefficient has reached the highest value of 49.2.The lowest leakage current density of the ceramic sample ZBO-0.04B₂O₃reached 3.922A/cm².In terms of frequency stability,the ZBO-0.04B₂O₃sample has the best performance and the lowest dielectric loss.In terms of temperature stability,ZBO-0.02B₂O₃has the best nonlinear coefficient stability.