X-ray powder diffraction study on the Al-for-Fe substitution in nickel ferrite and cadmium-nickel ferrites

Structural study by X-ray powder diffraction, applied to several solid solutions of spinel ferrites, indicates the differences of cation arrangement in the spinel oxides obtained hydrothermally, compared to that of ferrites prepared by ceramic methods. The 'low temperature' ferrites are generally cation deficient, nonstoichiometric structures, which may be considered as solid solutions formed between a given stoichiometric ferrite and the defect spinel gamma-Fe2O3. it has been confirmed by the measurements of integrated intensities of X-ray reflections, that the cationic vacancies are randomly distributed over the octahedral spinel cationic sublattices. According to the unit cell parameters of the cubic spinel phases, the substitution of cadmium and aluminium ions in the solid solutions of cadmium-nickel-aluminium ferrites, CdxNi1-xFe2-yAlyO4, prepared by hydrothermal methods is limited to x less than or equal to 0.4 and y less than or equal to 0.4 respectively.