CRYSTALLOGRAPHIC PROPERTIES OF HYDROTHERMAL BARIUM-TITANATE CRYSTALLITES

The crystallographic properties and defects of hydrothermally grown ba rium titanate crystallites are reported, When a precursor with a Ba:Ti molar ratio of 1.0 was used, cubic barium titanate crystallites were formed, However, when the precursor Ba:Ti molar ratio was 3.0, the pro duct was tetragonal, The defect concentration (including OB defects an d barium vacancies) was higher in cubic crystallites than in tetragona l crystallites. Because of the defects in the crystallites, the displa cement of Ba2+ cations and the deformation of the Ti-O-6 octahedrons w as suppressed; thus, no phase transition from cubic to tetragonal occu rred at the Curie point, When the defects were eliminated by thermal t reatment, the normal crystallographic properties were obtained, A high reaction temperature and a high Ba:Ti molar ratio in the precursor we re beneficial to limiting defect dormation in the crystallites; thus, tetragonal crystallites were obtained.