Rate-controlled synthesis and sintering of nanocrystalline barium titanate powder

The densification and grain size during sintering as well as particle size,of the barium titanate powder during Pechini decomposition-synthesis depends on the heating rate and this dependence originates from the kinetic competition between elementary transformation mechanisms, inherent in the two processes. The given competition is the main reason for development of the optimum mode of the mentioned thermal activated processes. As developed at the NCSU (USA) the Rate-Controlled Sintering (RCS) is known to allow the obtaining of dense and finegrained ceramics with improved properties. As developed at the IPMS (Ukraine) the Rate-Controlled Synthesis is directed to prepare nanocrystalline unagglomerated ceramic powders suitable for RCS. The extreme behavior of the BaTiO3 particle size as a function of heating rate is established and the optimal temperature-time path is calculated and verified to obtain the best powder of 20-25 nm particles. The change in microstructure and phase composition with heating rate is considered in details. The advantages of the RCS to achieve density of 99.9% and grain size around 100-150 nm are presented in comparison with the linear heating rate regime. (C)1998 Acta Metallurgica Inc.