Preparation of nm-sized BaTiO3 crystallites by a LTDS method using a highly concentrated aqueous solution

A low temperature direct synthesis method is useful for preparing nm-sized barium titanate (BaTiO3) crystallites, However, its characterization revealed that in BaTiO3 crystallites prepared by this method, there were many hydroxyl groups and barium vacancies. This is because of the use of aqueous solutions as starting materials. To prepare BaTiO3 crystallites with a hydroxyl group less, use of a highly concentrated aqueous solution must be required. In this study, BaTiO3 crystallites were prepared under a dry N-2 atmosphere using the highly concentrated aqueous solution. As a result, the formation of BaTiO3 crystallites with sizes around 16nm were confirmed. XRD and Raman measurements revealed that as-prepared powder was BaTiO3 single phase. However, in as-prepared BaTiO3 crystallites, a hydroxyl group was detected as an impurity. Its chemical analysis determined that the Ba/Ti atomic ratio was 0.786 +/- 0.005, which implies the presence of barium vacancies 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 was assigned to a tetragonal 4mm symmetry, which suggested that in the crystal structure of as-prepared BaTiO3 crystallites, there existed a disorder system. These crystallites were also characterized after annealing at various temperatures. (C) 2001 Elsevier Science B.V, All rights reserved.