Crystal Structure, Phase and Elemental Composition and Chemical Bonding in Bi 1− X A X FeO 3± Y Systems ( A = Sr, Ca; 0 ≤ X ≤ 1) from X-ray Diffraction, Mössbauer, and X-ray Photoelectron Spectra

An integrated study of samples of Bi1−x A x FeO3±y (A = Sr, Ca) systems for 0 ≤ x ≤ 1 (step 0.1) is performed using X-ray diffraction (XRD), Mossbauer spectroscopy (MS), and X-ray photoelectron spectroscopy (XPS). Considerable deviations of actual elemental compositions from nominal ones in the samples of both systems are discovered. Both Fe3+ and Fe4+ ions are found to be present in the samples of the Bi1−x Sr x FeO3±y system with x > 0. No Fe4+ ions are discovered upon substitution of Bi3+ by Ca2+ in Bi1−x Ca x FeO3±y , neither by Mossbauer spectroscopy, nor by XPS. Charge compensation in Bi1−x Ca x FeO3±y takes place mostly via creation of oxygen vacancies.