Soft X-Ray Absorption Spectroscopy as a Method to Study Y1–yCayBaCo4–xMxO7 Cobaltites (M = Fe, Zn)

Resumo

Soft X-ray absorption spectroscopy has been used to determine the charge state and content of cobalt ions in doped cobaltites CaBaCo₄O₇, Y_0.5Ca_0.5BaCo₄O₇, Y_0.5Ca_0.5BaCo_4–xFe_xO₇, and Y_0.5Ca_0.5BaCo_4–zZn_zO₇. A method has been proposed to determine the relative concentrations of cobalt ions in barium-containing cobaltites from the relative intensities of X-ray absorption Со L₃/Ba M₅ spectra, and the relative contents of both Fe and Zn doping elements and Co²⁺ and Co³⁺ ions have been determined. It has been found that the substitution of iron ions for some cobalt ions (cobaltite Y_0.5Ca_0.5BaCo_4–xFe_xO₇) transforms some Co³⁺ ions to Co²⁺ ions. It has been found that iron ions are in the 3+ charge state and have tetrahedral coordination with oxygen ions. The substitution of divalent zinc ions for some cobalt ions (cobaltite Y_0.5Ca_0.5BaCo_4–zZn_zO₇) increases the concentration of high-spin Co3+ ions. The tetrahedral coordination of the Co²⁺ and Co³⁺ ions has been confirmed.