A Moessbauer study of natural gahnite spinels showing strongly temperature-dependent quadrupole splitting distributions

Natural iron-containing gahnite spinels (ZnAl (sub 2) O (sub 4) ) are investigated using Mossbauer spectroscopy. Ferrous and ferric iron are completely ordered into tetrahedral and octahedral sites, respectively. Spectra recorded at 295, 77 and U K show a dramatic change in the absorption envelope ; this effect is ascribed to an inhomogeneous electric field gradient caused by near-neighbour effects acting on the ferrous iron in tetrahedral sites. The magnitude of this effect is shown to increase with increasing Fe (super 2+) substitution.