Evolution of the formation of barium titanate in the citrate process: the effect of the pH and the molar ratio of barium ion and citric acid

In this investigation, several experiments were conducted to study the effects of the molar ratio of barium ion and citric acid and the pH value on the formation of BaTiO3 by the citrate process. It was found that the molar ratio of barium ion and citric acid and the pH value could affect the chelation of carboxylate groups and Ba/Ti ions at temperatures below 450 degrees C but they seemed not to influence the formation of BaTiO3. The development of an oxycarbonate intermediate during the thermal decomposition of (Ba,Ti) gel was confirmed, which was suggested to possess a structure of BaTiO3,, whereby CO3-2 was located inside the layer structure. (C) 1998 Kluwer Academic Publishers.