A strong correlation of crystal structure and Curie point of barium titanate ceramics with Ba/Ti ratio of precursor composition

A series of barium titanate powders were synthesized from precursors BaCO3 and TiO2 with Ba/Ti ratio ranged from 0.96 to 1.04. For the ceramics sintered at 1300 °C for 2 h, with increasing Ba/Ti ratio from 0.96 to 1.04, the tetragonal distortion of perovskite barium titanate phase was decreased continuously and the Curie point was decreased monotonously from 122.9 to 98.0 °C. At the same time, the content of secondary phases was very low. This correlation of crystal structure and Curie point of barium titanate ceramics was explained by composition variation of the perovskite phase itself rather than by the influence from secondary phases. Due to very controversial results reported by different groups, it was proposed that BaTiO3 has some different states with different solubilities for BaO and TiO2. Further investigations should be conducted on the preparation and the properties of BaTiO3 with much BaO or TiO2 dissolved.