Investigation On The Structure And Properties Of Vanadate-Based Microwave Dielectric Ceramics

Low temperature co-fired ceramics（LTCC）,as the mainstream passive integration technology,has great application potential in 5G communication field due to its small volume,low dielectric loss and high integration density.Low temperature sintered vanadate-based microwave dielectric ceramics have attracted the attention of many scholars due to application in LTCC technology.Therefore,this thesis takes the low loss Ba Mg2V2O8 ceramic as the main research object,and systematically studies the relationship between crystal structure and microwave dielectric properties based on the refined data and complex crystal chemical bond theory,and the quality factor was greatly improved by non-stoichiometric ratio and ion substitution.In addition,vanadate-based Ca Bi Mo VO8 and Bi M2VO6（M=Mg,Zn）microwave dielectric ceramics with excellent dielectric properties were successfully prepared.The research work of this thesis is as follows:（1）The influence of sintering temperature on the structure and properties of Ba Mg2V2O8 ceramics was explored;The relationship between the chemical bond properties and microwave dielectric properties of Ba Mg2V2O8 ceramics was investigated by the chemical bond theory of complex crystals.Ba Mg2V2O8 ceramics obtained the best dielectric properties when sintered at 950°C:εr～12.6,Q×f～97039GHz,τf～-41ppm/°C.（2）The Q×f value of Ba Mg2V2O8 ceramics was greatly improved by non-stoichiometric ratio.The research results showed that increasing the content of Mg²⁺and V⁵⁺ions in an appropriate amount promoted the growth of Ba Mg₂V₂O₈ceramic grains to a certain extent,and reduced the porosity in the micro morphology.In addition,excessive V⁵⁺can not only compensate for the vanadium volatilized during the sintering process,but also effectively reduce the sintering temperature of Ba Mg2V2O8 ceramics.For Ba Mg2+x V2O8（0.04≤x≤0.16）ceramics with a non-stoichiometric ratio of Mg position,the quality factor achieved the maximum value at x=0.08.Finally,Ba Mg2.08V2O8 ceramics obtained excellent dielectric properties when sintered at 950°C:εr～13.4,Q×f～164646GHz,τf～-45ppm/°C.（3）The Ba Mg2-x Cox V2O8 and Ba Mg2-x Znx V2O8 ceramics with excellent properties were prepared by replacing Mg²⁺in Ba Mg₂V₂O₈ ceramics with Co²⁺and Zn²⁺.The effects of divalent ion substitution on the structure and properties of Ba Mg2V2O8 ceramics were systematically studied.The research results showed that Ba Mg1.94Co0.06V2O8 ceramics and Ba Mg1.98Zn0.02V2O8 ceramics sintered at 940°C had excellent microwave dielectric properties(Ba Mg1.94Co0.06V2O8:εr～12.0,Q×f～112809GHz,τf～-43ppm/°C;Ba Mg_1.98Zn_0.02V₂O₈:εr～13.5,Q×f～178760GHz,τf～-46ppm/°C).（4）The vanadate-based Ca Bi Mo VO8 and Bi M2VO6（M=Mg,Zn）microwave dielectric ceramics were synthesized by solid state reaction method.The effect of sintering temperature on the structure and properties of Ca Bi Mo VO8 and Bi M2VO6（M=Mg,Zn）ceramics was systematically studied.In addition,the chemical bond theory of complex crystals was used to study the Bi Mg2VO6 ceramic chemical properties and the relationship of microwave dielectric properties.The results show that Bi Zn2VO6 ceramics can achieve excellent performance when sintered at 725°C,εr～17.9,Q×f～41000GHz,τf～-88ppm/°C.