THE EFFECT OF MGO AND RARE-EARTH-OXIDE ON FORMATION BEHAVIOR OF CORE-SHELL STRUCTURE IN BATIO3

The formation mechanism of the core-shell structure of a BaTiO3(BT)-Mg O-Ho2O3-based system was studied. Mg reacted with BT at low temperatur es and showed poor diffusivity compared with Ho. The core-shell struct ure was considered to be formed by the suppression of the diffusion of Ho into the core region by Mg. Also, replacement modes of Mg and Ho i n perovskite were investigated. Lattice parameters were determined at temperatures higher than the Curie temperature in order to avoid cryst al structure change. It was confirmed that Mg dissolved in Ti site, an d Ho dissolved in both Ba and Ti sites. This indicates that Mg ions ac t as accepters and Ho ions act as both donors and accepters in the she ll phase.