Preparation and characterizations of uniform nanosized BaTiO 3 crystallites by the high-gravity reactive precipitation method

Abstract

A novel method for the preparation of uniform nanosized crystalline particles of barium titanate (BaTiO 3) at a low temperature (<100°C) by the high-gravity reactive precipitation (HGRP) technique is described. On the basis of the analysis of key engineering factors predominating in a reactive precipitation process, several experimental parameters, including the flow rate, reaction temperature, reactant concentrations, and effect of high gravity level were varied in order to establish the optimum conditions for the preparation of uniform nanosized BaTiO 3 crystallites. The BaTiO 3 powders, produced by the HGRP technique, show a cubic structure at room temperature and a quasi-spherical morphology. The stoichiometry of the BaTiO 3 particles can be controlled precisely and reproducibly. The reactants, barium and titanium salts can be used in high concentrations and the yield is quantitative. BaTiO 3 particles, in purely cubic phase as synthesized, underwent a phase transition to tetragonal phase by calcination over 1000°C. The lattice constant, a, decreased with an increase in the calcined temperature. These abnormal crystallographic features are assumed to result from lattice defects caused by OH incorporated in perovskite lattice as well as the grain growth in BaTiO 3 particles. The results of sintering tests and dielectric performance on the dry pressed titanate powders showed that the sintered body had a high permittivity and a low dissipation factor. The process has potential application in industry.