The effect of stoichiometry and the TiCl 3 addition on the microstructure of BaTiO 3

Abstract The effect of stoichiometry, i.e. Ba/Ti ratios (1.0025, 1.0 and 0.98) and the TiCl 3 addition on the microstructure and densification of BaTiO 3 were investigated. The BaTiO 3 powders were prepared by the conventional ceramic processing method. The samples were sintered at 1250, 1300, 1335 and 1360 °C for 1 h. The Ba 4 Ti 2 O 27 phase was found in the Ba excess BaTiO 3 , the platelet type Ba 2 Ti 5 O 12 phase was detected in the Ba and Ti excess compositions which were sintered at 1250 and 1300 °C, but not in the stoichiometric composition. When the sintering temperature was increased to 1335 °C 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 °C large polygonal grains of 20–30 μm in size were obtained within the fine grained matrix. The addition of 0.2 mol% TiO 2 as TiCl 3 to the stoichiometric composition revealed a similar structure at 1250 °C. 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.