Cation distribution in some natural spinels from X-ray diffraction and Mössbauer spectroscopy

Abstract

Abstract Three natural spinels of different places of occurrence and compositions were investigated by means of microprobe chemical analysis, single crystal X-ray diffraction and Mössbauer spectroscopy. All cation distributions between T and M sites were calculated from microprobe and XRD experimental data, by means of a mathematical model with appropriate assumptions. Fe 2+ and Fe 3+ assignments calculated in this way were compared with those observed in Mössbauer spectra. The satisfactory agreement found proves, at least in the samples studied, the reliability of the model and the assumptions used. In the spinels examined, such results show Fe 2+ and Fe 3+ virtually ordered in T and M sites respectively. Mössbauer data also revealed Fe 2+ in different tetrahedral sites due to the next-nearest neighbour effect, probably as a consequence of spinel genetic conditions.