チタン酸バリウムナノ粒子の構造と巨大誘電特性の発現機構

抄録

Almost impurity- and defect-free barium titanate (BaTiO₃) nanoparticles with various sizes from 20 to 430 nm were prepared using 2-step thermal decomposition method. The powder dielectric measurement method indicated that the dielectric permittivity of BaTiO₃ particles with a particle size of 140 nm exhibited a dielectric maximum of 5,000. Nano-structures of BaTiO₃ nanoparticles were analyzed using a composite structure model. It was found that BaTiO₃ nanoparticles had a composite structure consisting of (i) inner tetragonal core, (ii) gradient lattice strain layer (GLSL) and (iii) surface cubic layer. The crystal structure of each region didn’t depend on particle size while the volume fraction of the GLSL and the surface cubic layer increased with decreasing the particle size. These results suggested that the size effect of BaTiO₃ nanoparticles originated from the composite structure.