Study And Preparation Of Temperature-stable BaTiO₃-based Multilayer Ceramic Capacitor Dielectric Materials

Multilayer Ceramic Capacitors（MLCC for short）are an important electronic component that is widely used in various electrical circuits.As the application field of multilayer ceramic capacitors expands further,higher demands are placed on their performance.Capacitors used in harsh conditions such as defense,aerospace and automotive engines require higher temperature and better temperature stability.The development of high end MLCC devices is moving toward miniaturization,high capacity and high temperature stability.BaTiO₃ ceramics have been developed as the most effective dielectric material for the preparation of multilayer ceramic capacitors because of their good dielectric properties,excellent insulation properties and environmentally friendly characteristics,but the low Curie temperature and poor temperature stability of the pure phase barium titanate greatly limit their application in high temperature dielectric materials.In this paper,BaTiO₃-based dielectric ceramics satisfying EIA X8R(-55～150℃,ΔC/C_25℃≤±15%)and X9R standards(-55～200℃,ΔC/C_25℃≤±15%)were successfully prepared by doping modification and optimization of the synthesis process based on BaTiO3-based dielectric materials.The effects of dopant type,doping ratio and sintering regime on the materials were investigated.The main results of this paper are as follows:BaTiO₃-Nb₂O₅-Co₃O₄ was chosen as the basic material system to obtain air-sintered ceramic materials with room temperature dielectric constant of 2500,dielectric loss tanσ≤1.5%by co-doping with appropriate amount of Bi₂O₃ and Ho₂O₃ in accordance with EIA X8R.The doping modification mechanism of Bi₂O₃ and Ho₂O₃ and the effect on the structural morphology,Curie temperature and dielectric properties of ceramics were studied.0.9BaTiO₃-0.1(Bi_0.5Na_0.5)TiO₃-0.02Nb₂O₅ was selected as the basic material system,and air-sintered ceramics conforming to EIA X8R standard were obtained by doping with appropriate amount of Mg O and optimization of sintering temperature,with room temperature dielectric constant reaching 2000 and dielectric loss tanσ≤1.5%.The effects of the doping ratio of Nb/Mg and the sintering temperature on the structural morphology,Curie temperature,and dielectric properties of the ceramics were investigated,and the modification mechanism of Mg O was explained.0.9BaTiO₃-0.1(Bi_0.5Na_0.5)TiO₃-0.02Nb₂O₅-0.02Mg O was selected as the basic material system,and ceramics conforming to EIA X9R standard were obtained by doping with appropriate amount of spreading agent Ca ZrO₃ and optimizing the sintering regime,with room temperature dielectric constant reaching nearly 1800 and dielectric loss tanσ<1.7%.The effects of Ca ZrO₃ doping and sintering temperature on the structure,microscopic morphology,Curie temperature and dielectric properties of the ceramics were investigated,and the modification mechanism of Ca ZrO₃ doping was explained.