The Preparaton Of High Energy Capacitor Materials Based On Barium Titanate Poeders

First coating of aluminum oxide (a-Al2O3) was homogeneously coated on the surface 100 nm barium titanate (BaTiO3) particles via sol-gel and precipitation method, respectively. Then second coating of calcium magnesium aluminosilicate glass (CaMgAl4Si8024) was applied on first coating via sol-gel. It was systematic studied of the A12O3 coating process parameters, and this double-coated layer was characterized.Firstly, in sol-gel process Al(OC3H7)3 was acted as alumina source and HNO3 was acted as peptizator to prepare the Al2O3@BaTiO3 composite powder. The results showed that when water addition was 200, the alumina sol evenly distributed in BaTiO3 around; higher temperature (>80℃) was helpful for preparation of coated powders; the amount of the HNO3 had a best value, when the ratio of HNO3 and Al(OC3H7)3 was in 0.1-0.15(molar ratio), it was obtained in clarification and uniformity of the aluminum and sol coated composite powders.Furthermore, in precipitation process Al(NO3)3·9H2O was acted as alumina source and NH3·H2O was acted as the precipitating agent for the preparation of Al2O3@BaTiO3 composite powder. The results showed that:the optimal concentration of Al3+ was 1 mol/L; pH value from 8 to 12 was not affected to the coating; lower reaction temperature (25℃) was conducive to Al2O3 deposition on the surface of BaTiO3 powders.Finally, the Al2O3@BaTiO3 composite powders were coated by calcium magnesium aluminosilicate glass films via sol-gel method. The double coated powders of CaMgAl4Si8O24@Al2O3@BaTiO3 could be observed by EDS and line-by-line scanning.The characteristics of sintering behavior of the double coating BaTiO3 ceramic were obtained by means of a method of thermal analysis. It was found that sintering temperature of the double coating BaTiO3 ceramic was confirm in 800℃. The maximal electric breakdown strength of the double coating BaTiO3 ceramic reached 2.8×106 V/cm.