Synthesis of Nanometer-Sized Barium Titanate Crystallites Using a Modified Low Temperature Direct Synthesis Method and Their Characterization.

Abstract

A low temperature direct synthesis (LTDS) method is useful for preparing nm-sized barium titanate crystallites. However, the precise characterization of impurities in barium titanate crystallites is difficult because barium carbonate is formed as a by-product. In this study, a normal LTDS method was modified to prepare barium titanate crystallites under a CO2-free atmosphere, i.e., an N2 atmosphere. The barium titanate single phase was first prepared using this modified LTDS method. In the characterization of as-prepared barium titanate crystallites, only a hydroxyl group was detected as an impurity for ca. 11mass%. A chemical analysis of the as-prepared barium titanate crystallites determined that the Ba/Ti atomic ratio was 0.635±0.005, which means that a lot of barium vacancies formed in the crystallites. The average crystal structure, determined by XRD, was assigned to a cubic m3m symmetry, while the local structure, determined by Raman scattering spectroscopy, was assigned to a tetragonal 4mm symmetry, which suggested that in the crystal structure of as-prepared barium titanate crystallites, there existed a disorder system. Crystallites were also characterized after annealing at various temperatures.