Cation distribution of the system CuAlxFe2−xO4 by X-rays and Mossbauer studies

The structural and Mossbauer spectroscopy studies have been performed on the spinel solid solution series CuAlxFe2−xO4 (0.0 ≤ x ≤ 1.0). All the compounds with 0.0 ≤ x ≤ 1.0 crystallised with cubic spinel structure. Lattice constant values calculated from XRD analysis were found to decrease on increasing x, linearly obeying Vegard's law. The X-ray intensity calculations indicated that Cu2+ prefers to occupy octahedral (B) site, where as Al3+ ions replace Fe3+ ions from both tetrahedral (A) and octahedral (B) sites. Mossbauer spectra at room temperature display magnetic sextets corresponding to A and B-sites superimposed on each other. The data shows that Al-possesses greater preference for B-site compared to A-site, and iron exists in high spin ferric Fe3+ state. The hyperfine fields for both A and B-sites decrease with increasing x. The cation distribution calculated from X-ray intensity data agrees with the Mossbauer results.