Temperature dependence of the cation distribution in zinc ferrite (ZnFe₂O₄) from powder XRD structural refinements

Zinc ferrite (ZnFe₂O₄) has the cubic spinel structure with an (approximately) normal cation distribution. It was synthesised by direct reaction of the oxides at 800°C, and also by using a sodium tungstate flux with excess ZnO. The cation distributions in quenched samples of the flux-grown material were determined by powder X-ray diffraction. The degree of inversion in ZnFe₂O₄ increases from 0.02(2) at 500°C to 0.19(2) at 950°C. Samples quenched from higher temperatures show no further increase in x, in agreement with the trend in a_o. ⁵⁷Fe Mossbauer spectra were collected for a few samples at 80K and 298K. All spectra show only a single doublet with hyperfine parameters characteristic of octahedral Fe³⁺. The tetrahedral Fe³⁺ deduced from the XRD refinements cannot be resolved. -from Author