Defect structures in cadmium-nickel ferrites

The cation-deficient solid solutions of cadmium ferrite (CdFe2O4) and nickel ferrite (NiFe2O4) obtained by prolonged thermal treatment from stoichiometric samples have been investigated by X-ray powder diffraction, magnetic measurements and chemical analysis. The stoichiometric CdNi1-xFe2O4 samples were prepared from coprecipitated xCd(OH)2.(1 - x)Ni(OH)2-2Fe(OH)3-hydroxides, sintered at 1000-degrees-C during one hour. It has been found that because of the CdO volatility, stoichiometric preparations with x = 0.9 and x = 1.0 should be synthesized with the excess of 8% and 10% Cd(OH)2 respectively. The linear increase of spinel lattice constant with increasing Cd-content and the observed X-ray reflection intensities confirm the stoichiometry and the tetrahedral coordination of Cd2+-ions. Thermal treatment above 1000-degrees-C leads to the defect spinel structures with the Cd2+-deficiency, composed from solid solutions with the general formula Cdx-alpha-2+Fe1-x+alpha-3+[Ni1-x2+Fe1+ x- alpha/33+square-alpha/3]O4, corresponding to a solid solution of stoichiometric (Cd, Ni)-ferrite with the maghemite, gamma-Fe2O3.