| The traditional preparation method and the conventional raw materials of capacitor ceramics have been used in these experiments.The influence of different dopants and doping amount on the dielectric properties of medium temperature sintering (Ba,Sr) TiO3(BST) series capacitor ceramics has been investigated by means of orthogonal design experiments. The major secondary influencing factors and the influencing tendency of various factors levels for the dielectric properties of BST ceramics have been obtained,at the same time ,the optimum formula forε,for tanδand for withstand voltage have been obtained in the experimental conditions.The BST ceramics having optimum comprehensive properties has been obtained by means of orthogonal design experiments。The influencing mechanism of various components on the dielectric properties of BST ceramics is studied.On the basis of orthogonal design experiments, the influence of 4PbO.B2O3 glass,Bi2O3/Li2O solid solution CaZrO3,Nb2O5/Co2O3 doping amount and Nb/Co ratio on the dielectric properties .structure and medium temperature sintering of (Ba,Sr) TiO3(BST) series capacitor ceramics has been investigated by means of single factor variable design experiments。The results show that the 4PbO.B2O3 and Bi2O3/Li2O solid solution doping can form liquid,arrange crystal grain,make crystal grain contacting,make pore removing, make crystal grain size increasing,enhance ceramics density,and decrease sintering temperature in sintering process.The dielectric constant temperature property is influenced by component increasing and decreasing and phase changing.The doped mechanism is not the same by doping various amount CaZrO3,little CaZrO3 doping amount make dielectric peak overlapping phenomenon and increasing dielectric constant of BST ceramics,excessive doping CaZrO3 amount influence the dielectric properties by means of solid solution cushioning widen mechanism and grain boundary cushioning widen mechanism .The effect of depressing dielectric peak and widening dielectric peak is obvious,this is because of forming core and shell structure and depressing crystal grain growing up.The acting mechanism of dopants doping has also been investigated.A series formulas of medium temperature sintering BST capacitor ceramics with high dielectric performance have been obtained by means of conventional technique and conventional raw materials.With the help of the orthogonal design experiment, the single factor variable experiments doped with Bi4Ti3O12 and Dy2O3, the influence of various components on the dielectric performance,capacitance temperature characteristic, sintering temperature of barium and strontium titanate(BST) based high voltage capacitor ceramics with X7R specification has been investigated.The influencing mechanism of various components on the dielectric properties of barium titanate based capacitor ceramics is studied. These provide the basis for preparation of BST based capacitor ceramics with high voltage and X7R specification.The capacitor ceramics with good dielectric properties has been obtained,which the size of crystal grain is about 1μm, the sintering temperature is 1120℃, the capacitance temperature property is suited for X7R,dielectric constant e is 1324.2, dielectric loss is 0.0070, the withstand voltage is larger than 10kv/mm,.Doping CdO helps Nb2O5 and Dy2O3 dissolve and diffuse, reducing material's sintering temperature effectively, raising dielectric constant improving the shape look of crystal grain of ceramics, restraining crystal grain from growing up. Excessive Nb2O5 segregates in crystal boundary, preventing crystal boundary from moving, restraining the growth of crystal grain, thus forming fine grain structure. Ca2+ and Zr4+ respectively enter into some Ba2+ and Ti4+ location in the crystal lattice, reducing the dielectric constant peak value in the curie point, making curie temperature moving towards low temperature, restraining crystal grain growing up ,elevating dielectrical constant.Bi4Ti3O12 glass phases parcel crystal grain and are filled with between grains, forming the complex and not even structure of ceramic body. Different phases restricts barium titanate ferroelectric phases, making the depth of potential well of B position cation change shallow,and showing dielectric constant(ε) temperature(T) characteristic curve rather smooth.In BST based ceramics, doping small rare earth oxide Dy2O3 can keep back the growth of crystal grain, producing fine grain effect, making curie summit in entire work temperature range scatter and spread, get higher dielectric constant and good capacity temperature property,satisfy X7R property, raising the withstand voltage of BST based ceramics greatly.In barium-strontium titanate based ceramic, doping small amount rare earth oxide Y2O3 can keep back the growth of crystal grain, producing fine grain effect, making curie summit in entire work temperature range scatter and spread, get higher dielectric constant and good capacity temperature property, raising the withstand voltage of barium strontium titanate based ceramic substantially. When Y2O3 doping amount is 0.6wt% and Dy2O3 doping amount is 1.0 wt%, the medium temperature sintering BST ceramics with good dielectric properties has been obtained respectively.X-ray diffraction analysis shows that the crystal structure of barium-strontium titanate ceramics is not affected by Yb2O3 doping. The dielectric constant of barium-strontium titanate ceramics become elevating greatly while Yb2O3 doping. When Yb2O3 doping amount is 1.2wt%, the BST capacitor ceramics with high dielectric constant has been obtained ,which dielectric constant is 10000 and dielectric loss is 0.021.The temperature dielectric constant temperature peak is depressed and broadened while MgO doping. XRD paterns show that a single perovskite phase in samples. When MgO doping amount is 0.2wt% and 1.0 wt%,the BST ceramics with good comprehensive dielectric properties has been obtained respectively.The results show that Bi2Sn2O7 parcel crystal grain and are filled between grains, forming the complex and not even structure of ceramics. Different phases restricts barium-strontium titanate ferroelectric phases, making the depth of potential well of B position cation change shallow and showing dielectric temperature characteristic curve rather smooth. When Bi2Sn2O7 doping amount is 30wt%, the BST ceramics with good comprehensive dielectric properties has been obtained,which is suitable for X7R and sintered at 1150℃.Nanometer (Ba0.7Sr0.25Cd0.05)TiO3 (BSCT) powder is prepared by sol-gel method from Ba(CH3COO)2-Sr(NO3)2-Cd(NO3)2-Ti(OC4H9)4-H2O-CH3COOH-CH3CH2OH system. The influence of water volum and heat treatment temperature on the particle size .material phase composition and specific surface area of the BSCT nanometer powder was investigated using x-ray diffraction and specific surface area measurement instrument.The nanometer BSCT powder used for multilayer ceramic capacitor has been obtained,which The average particle size of the powder is 80 nm , the specific surface area is 13.64m2/g .Heat treatment at 950℃can form perovskite strucrure,which is low 250℃-300℃than traditional solid phase synthesis.The (Ba0.7Sr0.25Cd0.05)TiO3 superfine ceramics which the grain size is approximately 1μm are prepared using (Ba0.7Sr0.25Cd0.05)TiO3 namometer powder. The superfine BSCT ceramics with good comprehensive dielectric properties has been obtained. With decreasing of the grain size,phase changing temperature region decreases greatly, while the maximum dielectric constant increases greatly.The ultra-fine BST powders and doped ultra-fine BST powders prepared by citrate-nitrate combustion method were studied. The influence of citrate acid volume,pH value,heat-treating temperature and dispersant(ethylene alcohol) volume on the material phase ,morphology and particle size of ultra-fine BST powders were investigated, to obtain the optimum amount of citrate acid volume and dispersant(ethylene alcohol) volume, the proper pH value and heat-treating temperature. The superfine BST powders was obtained ,which the phase structure of BST powders is cubical phase, the average grain size is about 50-100nm,the particle morphology is irregularity spherical shape with conglobationAt the same time , the doped ultra-fine BST powders was obtained, the average grain size is about 70nm.Ultra-fine Bi4Ti3O12 powders were prepared by Sol-gel method . The results indicate that the phase structure of Bi4Ti3O12 powders is bismuth layer-structure and the average grain size is 70nm.BST mixed-powders were prepared by ultra-fine BST powders and doped BST powders doped with ultra-fine Bi4Ti3O12 powders. The preparation of superfine BST ceramics using BST mixed powders was studied. The surface topography, microscopic structure and phase structure of ultra-fine BST ceramics were analysed systematically. The effects of sintering temperature and the doped amount of Bi4Ti3O12 and trace elements doping on the surface microscopic structure and dielectric properties of superfine BST ceramics were studied. The superfine BST capacitor ceramics with good dielectric properties has been obtained ,which the sintering temperature is 1200℃and 1150℃,the grain size is about 0.5μm.
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