Effects of heat treatment and particle size on the tetragonality of nano-sized barium titanate powder

Abstract Although fine BaTiO 3 powders with high tetragonality (= c / a ) are required to increase the volumetric efficiency of a multilayer ceramic capacitor in industry, the tetragonality decreases and disappears below a certain particle size. In order to check the effects of particle size and processing temperature on tetragonality, heat treatment and X-ray diffraction were performed using commercial hydrothermal BaTiO 3 powders after adding different amounts of carbon black. Carbon black was burned out completely up to 600 °C during the heat treatment while acting as an effective particle growth inhibitor even at high temperature like 1100 °C. By changing the amount of carbon black, the synthesis of BaTiO 3 particles having similar size at different processing temperatures was possible. Tetragonality depended linearly on the average particle size up to 330 nm, while showing a saturated value of 1.0105 for larger particles. Tetragonality was not a function of processing temperature for particles heat treated above 950 °C, which implied that the heat treatment above 950 °C was not helpful for the enhancement of tetragonality.