Preparation of Highly Dispersed Barium Titanate Nanoparticles from Barium Titanyl Oxalate Nanoparticles and Their Dielectric Properties

Barium titanate (BaTiO3) crystallites with various particle sizes from 10 to 300 nm were prepared by the two-step thermal decomposition method of barium titanyl oxalate nanoparticles with a particle size of 30 nm under vacuum to prepare defect-free BaTiO3 nanoparticles with a thin surface cubic layer. Various characterizations revealed that the obtained particles were defect-free, dense BaTiO3 nanoparticles. Scanning electron microscopy (SEM) revealed that BaTiO3 nanoparticles prepared from oxalate nanoparticles were nonaggregated and highly dispersed. Moreover, the mesoscopic particle structure of BaTiO3 nanoparticles was investigated using a synchrotron X-ray diffraction (XRD) analysis and a two-layer model, i.e., the (1) surface cubic layer and (2) bulk tetragonal layer, and it was confirmed that the thickness of the surface cubic layer was always below 5 nm regardless of particle size. Finally, the dielectric property of BaTiO3 nanoparticles was measured by powder dielectric measurement at 20.00 °C and 20 MHz, and a high dielectric constant of around 30,000 was obtained for the BaTiO3 nanoparticles with sizes between 60 and 85 nm.