Hydrothermal synthesis of nanosized BaTiO 3 powders and dielectric properties of corresponding ceramics

Abstract

BaTiO 3 fine powders were synthesized by hydrothermal method at 150 °C or 250 °C for 7 h, starting from a mixture of TiCl 3 + BaCl 2 or TiO 2 + BaCl 2. The size of the crystallites is close to 20 nm whatever the starting mixture and the reaction temperature. These powders are well crystallized and constituted of a mixture of the metastable cubic and stable tetragonal phases. The ceramics obtained after uniaxial pressing and sintering at 1250 °C for 10 h or 20 h present high densification (up to 99.8%). The Curie temperature ( T c) and the electrical permittivity ( ɛ r) of the ceramics strongly depend on the type of titanium source that has been used for preparing the powder and on the sintering dwell time. Particularly, T c is shifted towards lower temperature when TiCl 3 is used. The permittivity value at T c of BaTiO 3 sintered at 1250 °C for 10 h reaches 7000 and 11,000 with respectively TiCl 3 and TiO 2 used as titanium source.