Domain size effect on dielectric properties of barium titanate ceramics

barium titanate (BaTiO3) ceramics with various grain sizes were prepared by a conventional sintering method and a two-step sintering mehod. The permittivity of the ceramics increased with decreasing the grain size down to 1.1 mu m on average. The BaTiO3 ceramics with an average grain size of 1.1 mu m had a high permittivity of 7,700. The transmission electron microscopy (TEM) observation realed that the 90 degrees domain density increased with decreasing the grain size. the domain size of the ceramics with the highest permittivity of 7,700 was approximately 100 nm. From an ultra wide range dielectric spectroscopy, it was found that the high domain density enhanced the orientational polarizability due to the domain-wall vibration and the ionic poarizability due to the lattice vibration. It was clarified that the increase of the permittivity with decreasing the grain size was due to the domain size effect.