Study Of Doping Modification And Properties Of CaWO₄ And ZnZrNb₂O₈

In recent years,with the development of science and technology and the market demand of electronic component,the development of electronic component is becoming more and more popular.Because of the wide application of dielectric materials,the research on dielectric parameters of dielectric materials is also increasing.It has became the focus of the study of dielectric materials in recent years to explore the relationship between dielectric constant and microstructure.Because CaWO₄ and ZnZrNb₂O₈ are dielectric materials with excellent dielectric properties,especially calcium tungstate ceramics,they are widely used because of their high quality factor,stable resonant frequency,low temperature coefficient and low sintering temperature.This paper first discusses the preparation of CaWO₄ and ZnZrNb₂O₈ pure phase dielectric ceramics,and determines the optimum process route by selecting different dispersants and different sintering temperatures.In the next two chapters,the performance analysis of CaWO₄ and ZnZrNb₂O₈ for different ion doping is discussed.We replaced the A bits of CaWO₄ by strontium and barium,replaced molybdenum by B,replaced ZnZrNb₂O₈ by Zn,and replaced by magnesium,nickel and manganese.And through to replace complete samples of SEM diagram analysis,finishing to the XRD diffraction spectrum,in order to obtain the atomic position,so as to further obtain the bond length,calculated by the bond length between atoms we can ionic bond,lattice energy,bond energy,bond valence and other important parameters,so as to explain the changes with the doping content,dielectric constant,Q×f₀,change the temperature coefficient of the resonant frequency.We draw the following conclusions:In this paper,CaWO₄ and ZnZrNb₂O₈ are prepared by solid phase method.The optimum sintering temperature of CaWO₄ is 1150℃,and the optimum sintering temperature of ZnZrNb₂O₈ is 1250℃.It is found that the dielectric constant is affected by bond-ionicity and it increases with the increase of B-site bond ionicity.Q×f₀increases with the increase of packing fraction and lattice energy.τ_f of speciments increases dued to the increase of B-site energy.The best dielectric properties of CaWO₄areε_r=10.22,Q=79919GHz,τ_f=-40.39ppm/^OC with the substitution of Mo andε_r=9.42,Q=79867 GHz,τ_f=-18.8/^OC with the substitution of Sr.The optimum of ZnZrNb₂O₈with Ni substitution isε_r=25.72,Q=73224 GHz,τ_f=-39.14/^OC.