Bi1-xCaxFeO3-δ (0 ≤ x ≤ 1) ceramics: Crystal structure, phase and elemental composition, and chemical bonding from X-ray diffraction, Raman scattering, Mossbauer, and X-ray photoelectron spectra

An integrated study of samples of Bi1-xCaxFeO3-delta (BCFO) system for 0 <= x <= 1 (step 0.1) is performed using X-ray diffraction (XRD), Raman scattering, Mossbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS). Measured elemental compositions of samples were found to deviate substantially from nominal ones. X-ray structure analysis discovered a continuous series of solid solutions with perovskite structure (or its derivatives) on the interval of nominal Ca content 0 <= x <= 0.9. However, the analysis of the data from all the methods used, limits the region of single phase samples (in presence of insignificant amount of foreign ones) to nominal Ca content interval 0.1 < x < 0.4. No Fe4+ ions are discovered upon substitution of Bi3+ by Ca2+, neither by Mossbauer spectroscopy, nor by XPS. Charge compensation in Bi1-xCaxFeO3-delta takes place mostly via creation of oxygen vacancies. Charge transfer satellites position in Ca2p XPS is shown to be sensitive to a number of oxygen ions in the immediate environment of Ca. (C) 2016 Elsevier B.V. All rights reserved.