Mossbauer spectroscopic investigation of the valency states of iron formed in the decay of <SUP>57</SUP>Co<SUP>2+</SUP> in Co[Cr<SUB>2</SUB>]O<SUB>4</SUB> and Co[Cr<SUB>2</SUB>]S<SUB>4</SUB>

The Mossbauer spectra of sources of 57Co in the form of spinels Co [Cr2] O4 and Co [Cr2]S4, matched against a 92 per cent 57Fe-enriched K4Fe(CN)6. 3H2O absorber have been studied from -80&#176;C to 362&#176;C. 57Co[Cr2]O4 source gave a complex spectrum which was analyzed to yield three peaks of different intensities and attributed to the presence of Fe4+, Fe3+ and Fe2+ states. A similar study with 57Co[Cr2]S4 showed the presence of the Fe3+ and Fe2+ states in the Mossbauer spectrum. The stabilization of the Fe4+ and Fe3+ states in addition to the expected Fe2+ state has been attributed to the presence of cation vacancies in the source lattice