Study On Dielectric Properties Of Sm-doped SrTiO₃Ceraamics

In this thesis,SrTiO3ceramic was selected as study material. Because of itsrelatively high breakdown strength and low dielectric loss,SrTiO3bears greatpotential in the development of materials with high energy storage density. In order tofurther improve the energy storage density of SrTiO3,Sm element was doped intoSrTiO3ceramic to enhance its dielectric constant, at first,and studying the mechanismof high dielectric constant by rare earth element with+3value doped. At last, addedAl2O3additive into the Sm-doped SrTiO3ceramic with high dielectric constant for thepurpose of electrical structure optimization, in order to achieve both high dielectricconstant and high insulance. And do related tests on the microstructure, phasestructure, sintering properties, electrical properties and so on.In this paper, Sr1-3x/2SmxTiO3ceramics synthesized through solid state methodand then the influence of the changing Sm2O3contents on the sintering properties, thecrystal structure, the microstructure, the dielectric properties, and the breakdownstrength of ceramics system are analyzed. The result shows that, the introduction ofthe rare earth elements of Sm will improve the sintering temperature of SrTiO3system,the best sintering temperature increased from1350℃to1400℃, thecrystal structureof SrTiO3was not influenced. In the range of0.0075~0.02, by adjusting the Smdoping amount x can get the dielectric ceramic materials with dielectric constant from350to10000.When Sm doping amount x=0.01,the dielectric constant ofSr1-3x/2SmxTiO3ceramics system was10000which was the highest dielectric constant,at the same time the dielectric loss maintained at around3%.The introduction of Smbelonged to inequitable doped,the free electrons by oxygen vacancy ionized made thedielectric constant gradually increase with the rising of the biasing electric field.Through the Arrhenius fitting analysis of dielectric relaxation and conductance forSr1-3x/2SmxTiO3ceramic, it was turned out to be that thermal activation caused thephenomenon, and had closed relationship with the oxygen vacancy secondaryionization by calculating the activation energy about0.7eV.Because of the Sm3+ions entered into the lattice and occupied the location of Sr,caused inequitable replacement resulting in generates phenomenon, so that thebreakdown performance was decreased obviously. For energy storage ceramics,breakdown strength is also one of the important influencing factors, so choose theappropriate additive to increase Sr0.985Sm0.01TiO3system breakdown performance is also one of the highlights of this experimental study. This thesis studies had foundthat Al2O3didn’t change Sr0.985Sm0.01TiO3ceramic sintering properties and crystalstructure. Solid solubility of Sr0.985Sm0.01TiO3<1wt.%,exceed the solid solubility,irregular phase SrAlTiO separated out. With the increasing of Al2O3doped amount,dielectric constant and dielectric loss of Sr0.985Sm0.01TiO3-xAl2O3were decreasedobviously, respectively reduced from10000to250, dielectric loss reduced from3%to1%.Meanwhile,to a certain extent, the insulation performance and the bias stabilityof the material improved. Dielectric relaxation and the conductance mechanism hadchanged with the increasing of Al2O3doping amount. When the amount of Al2O3x=0.7wt.%, dielectric constant was257, breakdown strength was148.7kV/cm, energystorage density was0.61J/cm3.