Preparation of nm-ordered barium titanate fine particles using the 2-step thermal decomposition of barium titanyl oxalate and their dielectric properties

The new 2-step thermal decomposition method using barium titanyl oxalate (BaTiO(C₂O₄)₂·4H₂O) was proposed to obtain impurity-free and defect-free nm-sized barium titanate (BaTiO₃) particles. At the 1st step, BaTiO(C₂O₄)₂·4H₂O was annealed at 400°C for 1 h in the O₂ flow. This product obtained at 400°C was amorphous, but its chemical composition was BaCO₃-TiO₂. At the 2nd step, the amorphous compound was annealed under vacuum. Finally, the BaTiO₃ single crystals with a size of 16.5 nm were prepared around 620°C. Their characterization was done using various methods. As the impurities, the surface adsorbed hydroxyl group (OH) and the surface adsorbed carbonate (CO₃^-)were detected, but no lattice hydroxyl group was detected using IR. These results suggested that the BaTiO, crystallites have less impurity in their lattice. The relative density of the BaTiO, crystallites was over 98%. Moreover, a new powder dielectric measurement was proposed. This method was composed of two parts; (1) the dielectric measurement using the slurry of the BaTiO₃ crystallites with 1-propanol and (2) the simulation using the electrostatic field analysis of the finite element method. When these two kinds of the values becomes to same, the dielectric constant of the BaTiO, crystallites can be determined. Using this powder dielectric measurement, the dielectric constant of the BaTiO₃ crystallites with a size of 16.5 nm were determined at almost 400.