Research On Preparation And Properties Of Non-Reducible Barium Titanate-Based Materials

Based on the domestic substitution of basic powder and ceramic powder for high-end base metal electrode multilayer ceramic capacitor（BME-MLCC）,this paper primarily focuses on the preparation and properties of non-reducible barium titanate-based materials.Based on the synthesis of high tetragonality ultrafine BaTiO₃ powder by solid phase method,the process matching problem between basic powder-ceramic-MLCC was studied.Through the structural design and process design of basic powder synthesis and the composition design of ceramic powder formula,BaTiO₃-based BME-MLCC specimens were prepared.The internal mechanism influencing the dielectric properties and microstructure of materials and MLCC devices was studied,and the composition design and preparation process of basic powder and ceramic powder formula were fed back,and then the improvement ideas and methods were put forward.The effects of BaCO₃ on the synthesis of BaTiO₃ powders by solid-state reaction were studied by utilizing diverse domestic BaCO₃ and TiO₂ raw materials.The uniformity of the mixture,the particle size of the product and the phase composition of the product were evaluated.The best raw materials for the synthesis of high-quality BaTiO₃ powders were Hongxing 1#BaCO₃ and Ti-02 TiO₂.The 160 nm BaTiO₃powders with tetragonality c/a of 1.0093 were synthesized by sand milling.The reaction mechanism of the solid phase method was studied,involving the direct contact reaction in the first step and the solid phase diffusion reaction in the second step.The activation energy of the two steps was calculated.The process design of solid-phase synthesis of BaTiO₃ powder was studied from four aspects:mixing method,drying method,synthesis method and fine grinding process.BaTiO₃ powder with tetragonality c/a of 1.0098 and 200 nm was synthesized in the pilot test by using the advanced sand mill mixing synthesis technology.The dielectric properties verified in ceramics have reached the powder level produced by domestic mainstream manufacturers.In the ceramic powder system of BaTiO₃+MgO+CaCO₃+Y₂O₃+MnCO₃+Si O₂,the effects of Ca and Y doping amount and sintering temperature on the microstructure and dielectric properties of the ceramics were studied,and the ceramic powder formula for BME-MLCC meeting the requirements of X7R（when used at-55～125°C,the capacitance change rate is within 15%）was obtained.Using the thermally stimulated depolarization currents test（TSDC）,the influence mechanism of Ca and Y doping amount on the dielectric properties of materials was revealed from the perspective of the type and concentration of internal defects in materials.The 1210 type BME-MLCC specimens were prepared by tape casting method.The thickness of the dielectric layer is 8μm,the number of stacked layers is 39,which reached the X7R standard,and the dielectric constant was 2094.The dielectric properties and bias characteristics were studied.The core-shell structure of the dielectric layer grains and the element distribution of the dielectric layer-inner electrode interface were tested by transmission electron microscope（TEM）.The results demonstrate that the interface layers are a significant factor influencing the reliability of ultra-thin BME-MLCC.