Modified Phase Diagram for the Barium Oxide–Titanium Dioxide System for the Ferroelectric Barium Titanate

The ferroelectric phase transition behavior in BaTiO 3 was investigated for various annealing times, temperatures, and Ba/Ti ratios by means of a differential scanning calorimeter. Coupling these observations with powder X‐ray diffraction and transmission electron microscopy allowed new insights into the barium oxide (BaO)–titanium dioxide (TiO 2 ) phase diagram. The transition temperature was varied systematically with the Ba/Ti ratio at annealing temperatures from 1200° to 1400°C in air. The transition temperature decreased with increasing concentrations of BaO and TiO 2 partial Schottky defects, and showed a discontinuous change at the phase boundaries. Beyond the solubility region, two peritectoid reactions were confirmed and revised; first around 1150°C for Ba 1.054 Ti 0.946 O 2.946 →Ba 2 TiO 4 +BaTiO 3 and second 1250°C for BaTi 2 O 5 →Ba 6 Ti 17 O 40 +BaTiO 3 , respectively. All other regimes of the BaO–TiO 2 were found to be consistent with the reported diagrams in the literature.