Abstract
We clarified the effect of (Ba,Ca)/Ti ratio on the substitution of Ba by Sn in (Ba,Ca)TiO3 perovskites. With decreasing (Ba,Ca)/Ti ratio, c/a ratio rapidly increases and leads to an increase in phase transition temperature. The increasing number of Ba site vacancies is effective for substituting Sn into the Ba site. We directly observed that Sn ions exist at Ba sites, for the first time, by spherical-aberration-corrected scanning transmission electron microscopy combined with energy-dispersive X-ray spectrometry and electron energy loss spectroscopy. These results provide insights for exploring BaTiO3-based ceramics containing Sn, which show high Curie temperatures without Pb.