Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles

摘要

Barium titanate (BaTiO{sub}3) crystallites with various particle sizes from 22 to 500 nm were prepared by the 2-step thermal decomposition method of barium titanyl oxalate. Various characterizations revealed that these particles were impurity-free, defect-free, dense BaTiO{sub}3 particles. The powder dielectric measurement clarified that the dielectric constant of BaTiO{sub}3 particles with a size of around 58 nm exhibited a maximum of over 15,000. To explain this size dependence, the THz region dielectric properties of BaTiO{sub}3 fine particles, especially Slater mode frequency, were measured using the far infrared (FIR) reflection method. As a sample for FIR measurement, the 3D colloidal sphere arrays were prepared using BaTiO{sub}3 fine particles. Finally, the dense BaTiO{sub}3 3D colloidal sphere arrays were successfully prepared, and their dielectric properties were measured. As the result, the lowest Slater mode frequency was obtained at 58 nm. This tendency was completely consistent with particle size dependence of dielectric constant.