Papers by Author: Toshimasa Suzuki

Abstract: The strontium titanate (SrTiO₃, ST) -coated barium titanate (BaTiO₃, BT) complex nanoparticles was prepared. Using this condition, ST-coated BT (ST/BT) and ST-coated ST (ST/ST) nanocube accumulation ceramics were successfully prepared with epitaxial interface between ST and BT. Dielectric properties were measured for the both accumulation ceramics, but there was no difference of the dielectric properties between both ceramics, and the origin of the result was discussed.

Abstract: Highly crystallized BaTiO₃ thin films were fabricated by a nanocrystal sintering process. Boron alkoxide was introduced into a slurry of Mn-doped BaTiO₃ nanocrystals with particle sizes of 5-7 nm. The deposited nanocrystal film on a (111)-oriented Pt/TiO₂/Al₂O₃ substrate was sintered at a low temperature of 800 °C and the obtained film had highly densified and oriented microstructures. We found that the boron additive enhanced the grain growth of nanoparticles and as a result the dielectric constant of the thin film increased to 1100 at 10 kHz, which is much higher than that of undoped BaTiO₃ thin films.

Abstract: Structural changes induced by oxygen vacancies in tetragonal phase BaTiO₃ are studied with first principles calculations within density functional theory. In our calculations, the incorporation of oxygen vacancies greatly decreases c/a ratio of the tetragonal phase BaTiO₃, and a phase transition from tetragonal to cubic phase occurs when the incorporation of the oxygen vacancies reaches about 4%. Our results also shows that the generation of the oxygen vacancies slightly increases the volume of BaTiO₃, and the increases are typically less than 0.5% even in heavily reduced conditions.