Mössbauer study on the chemical state of iron in binary oxide glasses based on Fe 2O 3

Abstract

Iron-containing binary oxide glasses in the systems of Fe 2 O 3 -P 2 O 5 , -TeO 2 , -SrO, -BaO, -PbO and -Bi 2 O 3 were prepared by using a twin-roller quenching method, and 57 Fe Mossbauer effect measurements were carried out on these glasses in order to determine the chemical state of iron ions. All the iron ions existed as Fe 3+ ions in all the glasses except Fe 2 O 3 -P 2 O 5 ones in which Fe 2+ ions coexisted. Fe 3+ ions in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses were laid on octahedral sites while they occupied tetrahedral sites in Fe 2 O 3 -SrO, -BaO, -PbO and -Bi 2 O 3 glasses. The covalency of Fe-O chemical bond was directly estimated from the isomer shift. The covalency was large in Fe 2 O 3 -SrO, -BaO, -PbO and Bi 2 O 3 glasses, while it was small in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses. This large dependence of the chemical state of iron ion on the kind of other cations coexisting with iron ions was explained based on the ionic character of chemical bonds between other cations and oxygen ions. Furthermore, the effect of covalency of Fe-O bonds on the magnetic properties of the glasses was discussed qualitatively.