Synthesis Of Barium Titanate Nano-powders By Microwave-hydrothermal Processing

BaTiO₃ electronic ceramic is the basic material of dielectric and semiconductor ceramics, which has high application value and is widely used in martial and demotic electronic machine. With the rapid development of electronic industries, electronic components are developing to miniaturization, lightweight and integration, The requirement of Ceramic Materials'grain size and microstructure should be higher, that means nanocrystalline barium titanate ceramics is needed. Many factors such as size, configuration, distributing status of powders seriously affect the performance of electronic ceramics. Especially when the size of the powder reach nano-meter grade, the performance of electronic ceramic changes very greatly. So it is still a hot research field to produce high purity BaTiO₃ nano-powders with small size, narrow size distribution and good crystallinity on electronic ceramic.In this paper, many methods of preparing BaTiO₃ powders have been summarized. And microwave radiation heating has been bring in hydrothermal process, which have the advantages of heating fast and temperature well-distributed by microwave heating and good crystallinity, size small and particle size well-distributed of powders prepared by hydrothermal. At the normal atmosphere, near-spherical barium titanate powders with 60nm size were obtained in 10min by this new method when the temperature was 70℃. The synthesis technology has been studied. X-ray diffraction (XRD) and transmission electron microscopy (TEM) means were used to study the factors in the process of preparing barium titanate nano-powders, such as reaction temperature, reaction time, pH, Ba/Ti in raw materials and surfactant. Through combining mathematical theory with practice experimental, the optimum process parameters of preparing by microwave hydrothermal were obtained. In addition, with physical and chemical means, the problem of reunion in the process of synthesizing nano-powders by microwave hydrothermal method has been solved, and the mechanism of dispersion was discussed.In the experiments, the barium titanate nano-powders was obtained with 60nm average size, well-distributed and near-spherical at the process parameters of reaction temperature (T=70℃), reaction time(t=10min), pH>13, Nop-10:NTi=1:10. When surfactant was used to disperse nano-powders, the anionic surfactant was better than the non-ionic surfactant. Because the long chain anionic surfactant both have steric effect and electric stability mechanisms. And when oleic acid was used as surfactant, the optimum amount of dispersion was N_{oleic acid} : N_Ti = 1:20. In the powders next processing, ultrasound physical dispersion worked effectively. And when ultrasound time was 10min, the particle size was the smallest and distribution was the narrowest. What's more, if ultrasound time was extended, particle aggregation may occurre.