Effects of pH on formation and morphology of barium titanate powders prepared by coprecipitation process

Abstract

Abstract The effects of pH on the formation and microstructure of barium titanate (BaTiO3) prepared by a coprecipitation process have been investigated. After calcination of the precipitates at 800°C, pure BaTiO3 was formed in samples prepared from oxalic solutions with pH in the range 5-7, and the powders obtained exhibited spherical shape with a size range of 5-10 μm. In contrast, small particles (around 0·1 μm) with Ti enriched phases (BaTi3O7, BaTi4O9) were produced at pH 1, and BaCO3 with irregular shape appeared at pH 10. The phases and morphologies of the calcined powders markedly influenced the sintering behaviour and dielectric properties of BaTiO3. After sintering at 1350°C, densified ceramics with high dielectric constants were derived from the calcined powders containing pure BaTiO3 phase. These results show that close control of the pH of the oxalic solutions is required to produce BaTiO3 powders with high sinterability and high dielectric constant.