X8r Capacitors Of High-k Dielectric Material

Multilayer ceramic capacitors(MLCC) are important electric components which are used in almost all areas of electronics.Barium titanate(BaTiO₃) was the most widely developed and used perovskite ferroelectrics.The reason behind a wide range of applications is that the barium titanate boasts of high specific permittivity and long lifetime of insulation resistance.The goal of this study was to investigate temperature stable MLCC dielectrics based on BaTiO₃.A few of compounds have been doped into BaTiO₃ system to obtain the X8R materials,and the dielectric properties and microstructures of BaTiO₃-based ceramics has been investigated.Finally we accomplished its commercial production requirement.The influence of oxide dopants upon dielectric properties of BaTiO₃-Nb₂O₅-ZnO system are investigated.The amount of Nb₂O₅ is very important in BaTiO₃-Nb₂O₅-ZnO system,The proportion of the non-ferroelectric phase with abundant Nb-Ba(Ti_x Nb_1-x)O₃ which increases as Nb₂O₅ contents increase.The formation of the non-ferroelectric phase of Ba(Ti_x Nb_1-x)O₃ is presumed to be the factor that the dielectric constant at room temperature decrease of BaTiO₃ ceramics.The rare earth is one of important dopants in BaTiO₃ systerm.In this paper,the influence of two rare earth oxide-Gd₂O₃ and Sm₂O₃ doped upon dielectric properties of BaTiO₃-Nb₂O₅-ZnO system are investigated.The vary of the dielectric constant at room temperature can be explained by the occupational sites of ions in perovskite structure.And on this basis,high performance was observed in Gd/Sm Co-doped BaTiO₃ ceramics,experimental best value of Gd/Sm is 0.7wt%/0.2wt%.In the experiment,the way of B-site substitution using precursor in BaTiO₃-NiNb₂O₆-MnNb₂O₆ system was also studied.Doping glass flux into this system can lower down it's sintering temperature.The mechanics of precursor replacement of B-site ion was also discussed.The results listed as follows:K＞2800,dielectric loss＜1.0%,insulation resistance＞7×10¹⁰Ω,ΔC/C＜±12%(-55℃～150℃)Microwave dielectric ceramics BiNbO₄ and ZMT with low dielectric loss and low temperature coefficient can be doped into BaTiO₃ systerm,on this basis,the systerm showed high performance.The experiment results have revealed that,the dielectric constant at room temperature decrease with the increase amount of BiNbO₄,but a proper usage of BiNbO₄ can improve dielectric properties of BaTiO₃ cerimics at high temperature.The high performance dielectrics satisfying X8R are achieved in the BaTiO₃-Nb₂O₅-ZMT new system.The influence of Nb₂O₅ and ZMT addition on phase transition,microstructure have been studied profoundly.In this paper,we doped rare quantity donor/acceptor into BaTiO₃ system to optimize the properies,X8R type MLCC prepared from our composite with independent intelligence had good dielectric properties:K=2370±100,dielectric loss＜1.6%,insulation resistance＞3×10¹⁰Ω,ΔC/C＜±14%(-55℃～150℃),average breakdown voltage＞800V/mil.