Effect of Occupational Sites of Rare-Earth Elements on the Microstructure in BaTiO3

The effect of rare-earth elements such as La, Ho and Yb on the microstructure in BaTiO 3 ( A B O 3 ) with various Ba/Ti ratios was studied. The grain size changed markedly depending on the Ba/Ti ratio in the case of La- and Yb-doped BaTiO 3 . On the other hand, in the case of Ho-doped BaTiO 3 , the grain size changed gradually in a wide range of Ba/Ti ratio. It is considered that Ho ions occupy both A - and B -sites, depending on the Ba/Ti ratio, while La and Yb ions occupy A - and B -sites, respectively. The solubility, the microstructure and the resistivity of rare-earth elements and Mg-substituted BaTiO 3 were also investigated. It was also confirmed that La ions occupied A -sites, Yb ions occupied B -sites and Ho ions occupied both A - and B -sites. It appears that the drastic change of the resistivity of Ho–Mg-substituted BaTiO 3 is due to the change in the predominant occupational site of Ho ions.