Crystal and defect chemistry of rare earth cations in BaTiO3

This study revisits the issue of rare earth cation substitutions into bariu m titanate. Analysis based upon crystal chemistry, defect chemistry and met astable states is presented to aid interpretation of experimental data. Rec ent detailed and highly precise X-ray powder diffraction and Electron Param agnetic Resonance experiments performed on samples produced with different A/B ratios and fired under different oxygen partial pressure conditions giv e rise to new insights into the material. Specifically, the site occupancy and the valence states for the rare-earth dopants in barium titanate are co nsidered. Earlier work is also reviewed and compared to the studies perform ed here. Collectively a classification of the various types of behavior obs erved for the rare-earth series in barium titanate is presented.