Ultrafine Barium Titanate Powders via Microemulsion Processing Routes

Three processing routes have been used to prepare barium titanate powders, namely conventional coprecipitation, single‐microemulsion coprecipitation using diether oxalate as the precipitant, and double‐microemulsion coprecipitation using oxalic acid as the precipitant. A single‐phase perovskite barium titanate was obtained when the double‐microemulsion‐derived oxalate precursor was calcined for 2 h at a temperature of as low as 550°C, compared to 600°C required by the single‐microemulsion‐derived precursor. A calcination for 2 h at >700°C was required for the conventionally coprecipitated precursor in order to develop a predominant barium titanate phase. It was, however, impossible to eliminate the residual TiO2 impurity phase by raising the calcination temperature, up to 1000°C. The microemulsion‐derived barium titanate powders also demonstrated much better powder characteristics, such as more refined crystallite and particle sizes and a much lower degree of particle agglomeration, than those of the conventionally coprecipitated powder, although they contained ∼0.2 wt% BaCO3 as the impurity phase.