THICKNESS OF CUBIC SURFACE PHASE ON BARIUM-TITANATE SINGLE-CRYSTALLINE GRAINS

The crystallographic structure of BaTiO3 particles prepared by convent ional solid-state reaction has been investigated by X-ray diffractomet ry and dielectric measurements. The systematic analysis of the diffrac tion pattern has clearly shown the coexistence of tetragonal and cubic phases at room temperature. The relative amount of cubic phase increa ses and the dielectric constant decreases with decreasing particle siz e. These experimental results are consistent with the model that the c ubic phase is located at the surface of BaTiO3 grains. The thickness o f the surface layer is estimated to be approximately 5 nm, irrespectiv e of the grain size.