Study On Doping And Coating Modification Of Barium Titanate Based Ceramics

BaTiO₃?BT?with typical perovskite structures is one of the most widely used electronic ceramics.In order to further improve its dielectric properties,doping,cladding and preparing composite ceramics are often used as modified method.In the early stage,the Ba_0.7Sr_0.3Ti_1-3/4yTm_yO₃?y=0-0.05?ceramics were prepared by Sol-Gel method by co-doped Sr and Tm elements.It was found that the dielectric constant increased to millions,but dielectric loss also increased at the same time.The modification method is adopted on the basis of BST ceramics for preparing the ceramics with high dielectric constant,low dielectric loss and good dielectric temperature stability in this paper.The BST powders were prepared by sol-gel method,and modified ceramics such as BST@SiO₂,BST-Al₂O₃and BST-Graphene composite ceramics were prepared by sol-gel method based on BST powder.Then,the preparation process of modified ceramics and the effects of SiO₂,Al₂O₃and graphene on the microstructure and properties of BST ceramics were studied,and the conclusions were as follows:?1?The BST@SiO₂ ceramic powders were verified to form the"core-shell"structure by transmission electron microscopy and infrared spectra,and a layer of SiO₂ amorphous film was coated evenly on the BST ceramic powders.After sintering,the Ba₂TiSi₂O₈ phase appeared in the BST@SiO₂ ceramic block,and the grain size decreased to 150 nm,but the porosity increased.With the increase of SiO₂ content,the dielectric constant decreased to3000 finally.However,the dielectric loss decreased to 0.15.The Curie temperature moved to low temperature first and then moved to high temperature.?2?The BST-Al₂O₃ ceramics had a homogeneous perovskite phase,and the Al₂O₃produced in the ceramics was verified by transmission electron microscope and infrared spectrum.The grain size of BST-Al₂O₃ ceramics decreased slightly.The dielectric constant decreased to about 10000 with the increase of Al₂O₃,and the dielectric loss was reduced to about 0.1.The Curie peak of BST ceramics was broadened after doping Al₂O₃,and when the addition was 5%,the Curie peak was almost flat.Besides,the Curie temperature moved to low temperature first and then moved to high temperature.?3?The BST-Graphene ceramics had a homogeneous perovskite phase,and the grain size of the ceramics has little change with the addition of graphene.With the increase of the amount of graphene,the dielectric constant decreased,and eventually dropped to about4000.But the dielectric loss was reduced to about 0.01.Besides,the Curie temperature moved to low temperature first and then moved to high temperature and then moved to low temperature finally.