Study On Nonlinear Coefficients Of ZnO-Pr₆O₁₁ Varistors

Zinc oxide is a direct band-gap semiconductor with a wide band gap,The band gap has a large 3.6 eV exciton binding energy,The lattice has intrinsic defects that make it have good semiconducting properties and can be used in a variety of fields.This project mainly discusses three different Zn-Pr varistors,and discusses the effects of doping,sintering temperature and holding time on the microscopic morphology,nonlinear coefficient and dielectric characteristics of the resistor.At the same time,a varistor with a nonlinear coefficient of up to 70 was obtained,its dielectric properties were also excellent.The specific content is as follows:(1)By studying the effect of lanthanum oxide doping and holding time on the ZnO varistor,it is found that when the lanthanum oxide doping content is set to 1.5mol%,the breakdown field strength of the varistor ceramic reaches 752 V/mm,and the grain boundary capacitance is the largest(276 pF),the loss tangent is minimized in the high frequency region,and the electrical characteristics of the resistor are the best.At the same time,it was found that the addition of Co2O3 is of great significance to the non-linear coefficient of the varistor.The experimental formula is 96.5mol%ZnO+l.5mol%Pr6O11+10×1.0mol%Co2O3+1.0mol%La2O3.get the best electrical characteristics of the varistor when the holding time is 0.5h,especially the non-linear coefficient of the resistance can reach as high as 70,and the breakdown field strength is also high as 740V/mm,and the dielectric constant is also excellent with low constant and low loss.(2)By studying the effects of TiO2 doping and sintering temperature on the titanium oxide doped varistor(ZPCT),it was found that:Increasing the content of TiO2 in a certain range can optimize the nonlinear coefficien,When the doping content is 1.5mol%,the electrical characteristics are the best,the nonlinear coefficient reaches 12,the breakdown field strength reaches 1980V/mm,and the leakage current is 296 ?A/cm2,in the audio range The dielectric constant is 35 to 86,and the dielectric loss is 0.13 to 0.18.When the temperature is 1250?,the electrical characteristics are the best,the non-linear coefficient is 10.23,and the breakdown field strength is 1450 V/mm.The dielectric constant is low,between 35?140,and the dielectric loss is the lowest(0.1).(3)By studying the effects of Er2O3 doping,sintering temperature and holding time on the Zn-Pr-Co-Er varistor,it is found that Er2O3 can reduce the barrier height and increase the breakdown field strength and nonlinear coefficient at the same time,when the doping content is 1.5 mol%,the electrical characteristics are the best,and the nonlinearity and breakdown field strength are the highest,which are 6 and 655 V/mm,respectively.When the sintering temperature is 1250? the maximum nonlinear coefficient is 9.73,and the electrical characteristics of the varistor are the best when the holding time is 1.5h.The nonlinear coefficient is the highest(5.77).At this time,the breakdown field strength is 827 V/mm,and the dielectric constant is 500?2000.(4)At the end of this article,The following conclusions were obtained:Both lanthanum oxide and titanium oxide can form phases at the grain boundaries,so the average value of non-linear coefficient is higher.The doping of lanthanum oxide can increase the non-linear coefficient,and titanium oxide can achieve The resistance is linearized,and thorium oxide cannot form a phase at the grain boundaries.The average value of non-linear coefficient is low,but the proper addition of thorium oxide can increase the non-linear coefficient.The effect of holding time on the non-linear coefficient of varistor and grain size It is not obvious,but it has a significant effect on the nonlinear coefficient of ZPCL varistor ceramics containing simple perovskite lanthanum cobaltate(LaCoO3);through research and comparison,it is found that hafnium oxide doped zinc oxide varistor is more than titanium oxide The doped varistor has a higher density,but excessive doping of hafnium oxide also tends to reduce the density.For Zn-Pr varistors,the phase transition of hafnium oxide will decrease.Varistor density,phase transition temperature may be controlled by different control praseodymium oxide doped optimum sintering temperature can be controlled.