High-temperature Moessbauer study of /sup 57/Fe interstitials in Chevrel phases

Moessbauer measurements have been made at /sup 57/Fe nuclei in the Chevrel phase compound Fe/sub 0/ /sub 05/SnMo/sub 6/S/sub 8/ from 300 to 1100K and Fe/sub 0/ /sub 05/HoMo/sub 6/S/sub 8/ from 80 to 673K. Iron atoms are found to be in two electronic states which are attributed to Fe monomers and dimers in Cu-II-like crystallographic sites. No evidence of diffusive broadening is observed to 1100K for Fe atoms in the Fe/sub 05/SnMo/sub 6/S/sub 8/ compound. The iron atoms are apparently in deep interstitial traps bound to S and Sn atoms. Thermal cycling experiments indicate that phase decomposition is occurring at temperatures of about 400C for the Ho compound and 800C for the Sn compound.