Study On Preparation And Dielectric Properties Of Ca Doped BaTiO₃-based Dielectric Ceramics

Multilayer ceramic capacitors?MLCCs?are important fundamental device of electronic information technology.In recent decades,as a result of the rapid development of the electronics industry,there is a growing demand for MLCC materials with wide working temperature and dielectric temperature stability.Barium titanate?BaTiO₃?has become the most successfully MLCC matrix material due to its excellent dielectric properties.Still,upper limit working temperature of BaTiO₃-based MLCC materials need to be elevated as higher as 200 ^oC.In this paper,Ca was selected as a peak shifter to modify BaTiO₃-BiZn_0.5Ti_0.5O₃ solid solution to get XnR type capacitors.BaTi_0.97Ca_0.03O_2.97[BTC3]and Ba_0.97Ca_0.03TiO₃[BC3T]ceramics were prepared via solid-state reaction method.The structure,electric and dielectric properties of Ca substitution at Ti and Ba sites were investigated.Structural and electrical properties analyses gave strong evidence of Ca²⁺substitution at Ti or Ba site in BTC3 and BC3T materials.BaTi_1-xCa_xO_3-x[BTC100x,0?x?0.05]ceramics were prepared.Effect of Ca substitution on the structure,microstructure and dielectric properties of BTC100x ceramics was investigated.When x?0.04,the diffraction peak shifted to lower angles with x increasing indicating increased unit cell volume and the solubility of Ca²⁺at Ti site in BTC100x was around 4mol%.when x=0.03⁰.04,BTC100x ceramics transformed from tetragonal to pseudocubic phase.Additionally,with increasing x,the Curie temperature decreased from 128 ^oC?BT?to⁴0 ^oC?BTC4 and BTC5?.?1-x?BTC4-xBZT,?1-x?BTC5-xBZT?y=0.1⁰.2?ceramics were prepared.Effect of BTZ content on phase structure,microstructure,dielectric,ferroelectric and electric properties was investigated.The solubility of?1-x?BTC4-xBZT,?1-x?BTC4-xBZT ceramics were determined to be around 0.15.The dielectric maximum peak T_m at 1kHz shifted to-20±5 ^oC due to Ca modification.When y=0.1,0.13,0.15,?1-y?BTC4-yBZT ceramics satisfy the requirement of EIA-X7R,X8R and X9R capacitors,with?=1430,tan?=0.0087;?=1277,tan?=0.0089 and?=1060,tan?=0.015,respectively.For?1-x?BTC5-xBZT ceramics,when y=0.1,0.15,ceramics satisfy the requirement of EIA-X7R and X9R capacitor,with?=1493,tan?=0.03 and?=1051,tan?=0.01,respectively.Nominal composition?1-x?BT-xBTC?x=0⁰.3?ceramics were prepared.Effect of BTC content on phase structure,microstructure,dielectric properties was investigated.when x?0.15,undesired phases were found and the phase structure changed from tetragonal to tetragonal and cubic coexist phase structure.There were two dielectric peaks,one was curie peak the other was peak 1.Nominal composition?1-x?BT-xBTC ceramics were Bi and Ca co-doped BaTiO₃ and the dielectric curve became more flat.