Structure and Mechanism of Ultrahigh Dielectric Properties for Barium Titanate Nanoparticles

Abstract

Almost impurity-and defect-free barium titanateBaTiO 3 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 BaTiO 3 particles with a particle size of 140 nm exhibited a dielectric maximum of 5,000. Nano-structures of BaTiO 3 nanoparticles were analyzed using a composite structure model. It was found that BaTiO 3 nanoparticles had a composite structure consisting ofiinner tetragonal core,iigradient lattice strain layerGLSLandiiisurface 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 BaTiO 3 nanoparticles originated from the composite structure.