Ca K-edge X-ray absorption fine structure in BaTiO3-CaTiO3 solid solutions

Ca K-edge extended X-ray absorption fine structure (EXAFS) has been used to analyze local coordination of Ca in (Ba,Ca)TiO3 and Ba(Ti,Ca)O3−δ solid solutions. EXAFS reveals the average Ca-O distance in (Ba1−xCax)TiO3 (0 < x ≤ 0.3) is significantly larger compared to CaTiO3, which suggests a relatively limited relaxation of the oxygen framework around Ca in the solid solutions; nevertheless, the [CaO12] coordination environment appears to be strongly distorted. No significant differences in Ca-O distances were observed among the solid-solution samples with different x-values. For BaTi0.97Ca0.03O3−δ sample, EXAFS indicates that Ca is predominantly located on the B-sites with a Ca-O distance of 2.28 A. X-ray absorption near-edge structure, which is different for A and B-site Ca, has been interpreted using phenomenological considerations.