Effect of temperature schedule on the particle size of barium titanate during solid-state reaction

Nano-sized BaTiO3 particles were synthesized by a solid-state reaction in air using a 2-step heat treatment process. The dependence of the particle size and tetragonality (=c/a) on the temperature schedule was investigated. The temperature was held for 10 h at an intermediate temperature before heating to the target temperature of 1000 degrees C for 1 h. Although more heat was consumed, the powders synthesized by the 2-step heat treatment method showed a much smaller particle size with higher tetragonality than those produced by direct heating. For example, the mean particle size was <100 nm at a holding temperature ranging from 500-700 degrees C. while it was 246 nm for direct heating to the same target temperature of 1000 degrees C. This was explained by the enhanced nucleation rate during temperature holding stage based on the TG/DTA and high temperature XRD results. (C) 2009 Elsevier B.V. All rights reserved.