Preparation And Characterization Of MLCC Dielectric Ceramics With Temperature Stability And Colossal Permittivity

In this paper,BaTiO₃ based ceramics have been investigated as the research basic system.By adjusting the technological parameters and doping contents,colossal permittivity（CP,ε>10000）materials were successfully prepared by traditional solid-state method and atmosphere sintering process.The formation of the colossal permittivity behavior in reduced BaTiO₃ based ceramics has been analyzed in detail.The relationship between microstructure and dielectric/electrical properties of the CP ceramics has been studied,and the theoretical mechanisms of colossal permittivity accompanied with high resistivity have been proposed.This paper presents a new idea to optimize the performance of giant dielectric constant materials,which establishes theoretical basis for the further study of temperature stabilized CP materials.Colossal permittivity behavior in BaTiO₃–Na_0.5Bi_0.5TiO₃-Nb₂O₅ ceramics has been studied,which shows extremely high permittivity up to¹0⁵.The comprehensive effect of doping concentration and sintering atmosphere on dielectric properties of donor-doped BaTiO₃ ceramics are discussed.Hopping polarization,which is induced by reducing sintering atmosphere in barium titanate,makes great contributes to the promotion of the dielectric constant.Along with the increasing reducibility of sintering atmosphere,more and more intergranular electrons appear and then grain boundaries become more conductive,resulting in the deterioration of insulation properties.The heterogeneous doping of Nb⁵⁺ions leads to the formation of"shell-core"structure.Suitable niobium doping content reduces charge accumulation by optimizing the“core-shell”structure,which ensures that the hopping polarization will not be weakened and insulation resistivity still maintain high level.High performance BaTiO₃-based CP material has been obtained:ε¹.3?10⁴,tanδ⁰.06,ρ¹0¹⁰Ω·cm@100VDC.The effect of Ni²⁺and Mn²⁺ions co-doping has been explored based on BaTiO₃-Na_0.5Bi_0.5TiO₃-Nb₂O₅ CP ceramics.It has been determined that Mn²⁺ions effectively prevent the generation of hopping electrons induced by the reducing atmosphere,which leads to the disappearance of CP behavior.Ni²⁺ions significantly raise the dielectric constant but fail to prevent the deterioration of resistivity.The balance between the insulation properties and dielectric properties has been achieved via Ni/Mn co-doping.BaTiO₃-based ceramics with colossal permittivity（⁴.1×10⁴@1kHz）and low loss tangent（tanδ⁰.026 at room temperature）has been prepared by sintering in reducing atmosphere.Excellent insulation resistivity(¹0¹¹Ω·cm@100VDC)has been obtained in this new colossal permittivity ceramics,and the samples still maintain outstanding dielectric properties over a wide temperature range-55℃¹50℃,satisfying IEA-X8R specification.This new colossal permittivity material exhibits a promising potential for application in high-capcaitance temperature stable MLCC.