Preparation And Characterization Of X9R Barium Titanate Based Ceramics

Multilayer Ceramic Capacitors?MLCC?are the most widely used passive electronic components in the field of electronic information.The application of electronic equipment is more and more extensive,which expects dielectric material of MLCC could develop in the direction of high capacity and small size,environmental protection and lead-free,and wide temperature range.In particular,higher requirements are placed on the temperature stability of the dielectric material of MLCC.Therefore,it has become more and more urgent to develop a temperature-stable dielectric material that satisfies the X9R standard.MLCC ceramics usually use perovskite-type ferroelectric BaTiO₃?BT?as a basic raw material.However,the dielectric constant of pure BaTiO₃ changes drastically around 130°C due to the phase transition.To improve its dielectric properties,we added(Bi_0.5Na_0.5)TiO₃?BNT?material to BT.And they were mixed to form a solid solution 0.9BaTiO₃-0.1(Bi_0.5Na_0.5)TiO₃?0.9BT-0.1BNT?to increase the Curie temperature.The study of element substitution on 0.9BT-0.1BNT was carried out to improve its dielectric properties.The diffusion rate of niobium ions in BT is slow,which can result in the formation of core-shell structure in ceramics and improve its temperature stability.Therefore,we studied the effect of Nb₂O₅,NiNb₂O₆,MnNb₂O₆ doping separately,and NiNb₂O₆ and MnNb₂O₆ co-doping on the dielectric properties and microstructure of 0.9BT-0.1BNT ceramic system.A new idea was proposed to improve the Curie temperature of BaTiO₃based ceramics,and two dielectric materials that meet the X9R standard were successfully prepared.The(K_0.5Na_0.5)NbO₃?KNN?powders were synthesized by solid-state reaction method and liquid-state reaction method respectively.The effects of KNN doping concentration and preparation process on the dielectric properties and microstructure of BaTiO₃ were studied.And a kind of ceramic material meeting the X8R specification was obtained,which had a dielectric constant 3084 at room temperature.Then the effect of KNN prepared by liquid-state reaction method doping on the dielectric properties of0.9BT-0.1BNT ceramic system was studied.When the KNN doping amount was4mol%,the ceramic can satisfy the X9R standard,which was sintered at 1250°C.Its dielectric constant was 1740,and the dielectric loss was 2.0%at room temperature.Through the research of this thesis,various ceramics with high temperature stability were obtained,which can promote the development of new MLCC ceramic materials.