The effect of stoichiometry and the TiCl3 addition on the microstructure of BaTiO3

The effect of stoichiometry, i.e. Ba/Ti ratios (1.0025, 1.0 and 0.98) and the TiCl3 addition on the microstructure and densification of BaTiO3 were investigated. The BaTiO3 powders were prepared by the conventional ceramic processing method. The samples were sintered at 1250, 1300, 1335 and 1360 degreesC for I h. The Ba4Ti2O27 phase was found in the Ba excess BaTiO3, the platelet type Ba4Ti5O12 phase was detected in the Ba and Ti excess compositions which were sintered at 1250 and 1300 degreesC, but not in the stoichiometric composition. When the sintering temperature was increased to 1335 degreesC the platelet type grain growth disappeared in the Ba excess composition, but remained in the Ti excess composition. In the stoichiometric composition, the fine grained microstructure occurred at 1250 and at 1300 degreesC large polygonal grains of 20-30 mum in size were obtained within the fine grained matrix. The addition of 0.2 mol% TiO2 as TiCl3 to the stoichiometric composition revealed a similar structure at 1250 degreesC. Below the eutectic temperature, the densification rates of the Ti excess samples were lower than the Ba excess samples, but above this temperature they showed a higher densification. (C) 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.