Characteristics and formation mechanism of BaTiO3 powders prepared by twin-fluid and ultrasonic spray-pyrolysis methods

Spherical fine (micrometer and submicrometer in size) homogeneous BaTiO3 powders were synthesized from ethanol: water solutions of BaCl2 and TiCl4 using the spray-pyrolysis technique. Two different atomizers-twin-fluid and ultrasonic, with a resonant frequency of 2.5 x 10(6) Hz-were used for mist generation. Hollow spherical particles containing a certain amount of unreacted BaCl2 phase and having a mean particle diameter of 2.5 mu m mere obtained at 1173 K using a twin-fluid atomizing system. Decomposition of precursors and their transition to the cubic BaTiO3 phase occurred, even at 973 K in the case of the ultrasonic atomizing system. For the initial droplet size of 2.2 mu m and residence time of similar to 60 s, spherical BaTiO3 particles with the mean particle diameter of 0.53 mu m were obtained. A BaTiO3 formation mechanism has been proposed as a reaction between TiO2 and BaCl2 rather than a reaction of oxides.