Preparation of nm-sized BaO3 particles using a new 2-step thermal decomposition of barium titanyl oxalate

To obtain inpurity-free and nm-sized barium titanate (BaTiO3) particles, a new 2-step thermal decomposition method from barium titanyl oxalates (BaTiO(C2O4)2 · 4H2O) was proposed. At the 1st step, BaTiO(C2O4)2 · 4H2O was annealed at 400°C for 1 h in the O2 flow. The annealing temperature of 400°C was chosen for the following reasons; (1) no formation of BaCO3 and TiO2 and (2) the complete removal of H2O and other carbon species. This compound obtained at 400°C was amorphous phase, and its chemical composition was BaCO3-TiO2. When this compound was annealed in air at higher temperatures, the large BaTiO3 particles were prepared with by-products such as BaCO3. Thus, at the 2nd step, to prevent the crystal growth and the formation of BaCO3, this compound was annealed above 600°C in vacuum. Finally, the BaTiO3 single crystals with a size with 16.5 nm were prepared around 620°C. These BaTiO3 fine particles were characterized using various methods to investigate defects and impurities in the particles. As a result, it was confirmed that there was no impurity in the BaTiO3 lattices.