Crystal structure of BaTiO₃ in the cubic phase

Abstract

The crystal structure of cubic barium titanate was determined at five temperatures up to 180 °C, using the data collected by an X-ray automatic four-circle diffractometer. At temperatures between the Curie temperature and about 180 °C, the Ti atom is displaced from the center of the unit cell along the <111> direction and has eight local disorder positions. This result is the same as the model proposed by Comes et al. In addition to this disorder, we find that the Ba atom is displaced from the cell corner along the <110> direction leading to twelve local disorder positions and the O atoms are uniformly distributed on rings in their face centered planes. At temperatures higher than about 180 °C, the Ti atom is no longer located at any local disorder positions but lies rather on the center of the unit cell.