HYDROTHERMAL SYNTHESIS AND DIELECTRIC-PROPERTIES OF TETRAGONAL BATIO3

Hydrothermal synthesis of barium titanate (BaTiO3) at 240-degrees-C using different barium salts as starting reactants is examined. It is found that halide salts (I-, Br-, Cl-) result in the highest tetragonal content, followed by acetate, nitrate, and hydroxide salts. The tetragonal content was quantified from differential scanning calorimetry by following the endothermic Curie transition around 130-degrees-C and reached as high as 37-39% for the materials made with the barium halides. The particle sizes ranged from 0.15 to 0.37 mum, as estimated by scanning electron microscopy. Sintering and dielectric properties of the barium titanates synthesized from different barium sources were examined. BaTiO3 made from the chloride salt sintered with high densities at 1250-degrees-C with grain sizes of 1-5 mum and a room-temperature dielectric constant (1 kHz) of 2960.