Mössbauer Studies of Divalent and Trivalent 57Fe in CoSO4 and CoSO4·7H2O

Abstract

We report the results of a Mössbauer study of ⁵⁷Co(⁵⁷Fe) in CoSO₄ as a function of temperature at atmospheric pressure and as a function of pressure at room temperature. In addition to the expected divalent ⁵⁷Fe component, one also observes a trivalent component, the relative intensity of which decreases with increasing temperature or pressure. The isomer shifts of both charge states also decrease with increasing temperature or pressure. The behavior of the large quadrupole splittings observed in each charge state is analyzed using the crystal field approximation. We also find similar results in a temperature study of CoSO₄·7H₂O at atmospheric pressure. The relative intensity of the trivalent ⁵⁷Fe component is considerably greater in the hydrate and also decreases with increasing temperature.