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

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.