Study On Synthesis Processing Of Ultrafine BaTiO₃ Powder Used By Functional Ceramics

In view of the existing problems of the processing research on barium titanate and the control of particle size, the relatively simple direct precipitation method was choiced to synthesis barium titanate powder and the processing for synthesis barium titanate powder was studied systematically in this paper. During the course of study on the preparation process of barium titanate powder, some of the major factors and synthesis conditions influenced the formation of barium titanate were determined and their action rule was discussed. The viewpoint of structure of barium titanate prepared by direct precipitation was proposed and the formation mechanism of barium titanate was preliminary discussed. Through the experiments, some synthesis conditions and factors influenced the particle size of barium titanate powder were found and discussed for particle size control of barium titanate prepared by direct precipitation.The synthesis conditions including system acidity, reaction temperature, preheating temperature of the starting materials etc. effect on the phase, composition and particle size of products were inspected. The causes of impurity barium carbonate were discussed as well as the relative content along with the changes of synthesis conditions was also studied. The measurements such as FT-IR, XRD, SEM were used to characterized the product. Experimental also inspected the action rule of acidity behavior and the formation mechanism of barium titanate. Furthermore, the particle size control of barium titanate was preliminary discussed. Some meaningful results were obtained:System acidity and a certain energy field are essential conditions for the formation of barium titanate prepared by direct precipitation. Cubic barium titanate was obtained as the main phase of the product only when pH>13 and also the reaction temperature above 60℃under this experimental condition. OH-plays variety roles on the formation of barium titanate in the process. Not only to neutralize, but also to promote transformation in molecular configuration structure, form the octahedral complex and to transform the key alcohol on the other hand; in the meanwhile, in the micro-environment, OH-plays vital role as the driving force to promote the formation of barium titanate. There is a peak linked by hydroxyl instead of oxygen in titanium oxygen octahedron during the formation process of barium titanate prepared by direct precipitation method. The reaction mechanism is possiblely described as absorption- infiltration-exchange mechanism.The main factors influenced the particle size of barium titanate prepared by direct precipitation are inspected. The factors especially the initial concentration of TiOCl2 and adsorption temperature when materials mixed play vital role on the control of the particle size of barium titanate. The narrower size distribution, approximate spherical ideal barium titanate powder with particle size of about 0.4μm is obtained when synthesis conditions are strictly controlled.