Study Of Barium Titanate Ceramics With "Core-shell" Structure And Temperature Stable Properties Using Precipitation Coating Method

Multilayer ceramic capacitors (MLCC) of BaTiO3-based are main research content in the article. The preparation methods and modification mechanism of ceramic material were studied, and then developed temperature characteristic with Y5V and X8R standard of high-performance materials, respectively. Firstly, MLCC ceramics materials of BaTiO3-based with Y5V standard were prepared by sol-gel method. The study found that the properties of ceramics materials would be optimized after the powders coating modified. So the coated modification is very important in optimization performance of ceramics materials. It is found that the coated modification will be more easily and easy to control when the monodisperse spherical particles as "core". The BaTiO3-based powders with monodisperse spherical were studied, and the possible mechanism was speculated. Then, the "core-shell" composite powders were obtained by using chemical precipitation method (monodisperse BaTiO3-based powders as the "core"; Ho2O3 La2O3, MgO or YFeO3 as the "shell"), and studied on the micro structure and properties of composite powders and ceramics. The main contents of this paper are shown as below:(1) Zirconium barium titanate powders were prepared by sol-gel method. Furthermore, the effects of different Dy (Sm) concentrations on the phase composition, microstructure, and dielectric properties of multicomponent BZTZN ceramics were investigated. We used a modified version of the Curie-Weiss law to clarify the influence of the dopant on the dielectric properties of the BZTZND ceramics. The BZTZND2 ceramics met the Y5V specifications, the grain size is about 3μm and the dielectric constant was greater than 20000, with a dielectric loss (at 25℃) of only 0.006, and y coefcient for the sample was-1.43, thus confirming the relaxor behavior of the material. The BZTZNS4 ceramics met the Y5V specifications and the dielectric constant was greater than 20000, with a dielectric loss (at 25℃) of only 0.011.(2)The BaTi0.9Zr0.1O3 powders were prepared by atmospheric water phase. Design with the "core-shell" structure composite powders, Ba(Zr0.0Ti0.9)O3 as the "core" and Ho2O3 as "shell". The changes of experiment conditions (presintering temperature, sintering temperature and quantity of cladding material) can control "core-shell" structure of the ceramic samples. The solution of "core" and "shell" materials would be controlled, and further control of the temperature coefficient of capacitance. Get the materials met the Y5V specifications and lay a foundation for type X8R fine-grain ceramics.(3) A series of monodisperse spherical sub-micron BaTiO3-base powders (BaTiO3, Ba0.97La0.02TiO3 and Ba0.9895Bi0.0070TiO3) were prepared by atmospheric water phase. The BaTiO3-based powders were studied on the phase composition, microstructure. And the possible mechanism was speculated. The coated modification was studied for the BaTiO3-based powders with monodisperse spherical by co-precipitation. The effects of La2O3 coated on the phase composition, microstructure, and dielectric properties of BaTiO3 ceramics were investigated. The BaTiO3@La2O3 composite ceramics met the X8R specifications, the grain size was about 250 nm and the dielectric constant was 2902, with a dielectric loss (at 25℃) of only 0.00556. Furthermore, the effects of different MgO coated contents on the phase composition, microstructure, and dielectric properties of BaTiO3 ceramics were investigated. The addition of MgO coated helped to improve the microstructural homogeneity of the Ba0.9895Bi0.0070TiO3 ceramics (the grain size is about 250 nm), improve its dielectric constant at low temperature, and enhance the temperature stability.(4) The BaTiO3@YFeO3 composite powders with "core-shell" was prepared by co-precipitation. The effects of different YFeO3 coated contents on the phase composition, microstructure, and dielectric properties of BaTiO3 ceramics were investigated. The BTYF-6 composite ceramics met the X8R specifications and the dielectric constant was 2319, with a dielectric loss (at 25℃) of only 0.016. The magnetization of the BTYF-6 ceramics was about 2.31 emu/g, and remanent magnetization is 1.3 emu/g.