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 u sing diether oxalate as the precipitant, and double-microemulsion coprecipi tation using oxalic acid as the precipitant. A single-phase perovskite bari um titanate was obtained when the double-microemulsion-derived oxalate prec ursor was calcined for 2 h at a temperature of as low as 550 degrees C, com pared to 600 degrees C required by the single-microemulsion-derived precurs or. A calcination for 2 h at >700 degrees C was required for the convention ally coprecipitated precursor in order to develop a predominant barium tita nate phase. It was, however, impossible to eliminate the residual TiO2 impu rity phase by raising the calcination temperature, up to 1000 degrees C. Th e microemulsion-derived barium titanate powders also demonstrated much bett er powder characteristics, such as more refined crystallite and particle si zes and a much lower degree of particle agglomeration, than those of the co nventionally coprecipitated powder, although they contained similar to 0.2 wt% BaCO3 as the impurity phase.