Defect structures in cadmium-nickel ferrites

Abstract

The cation-deficient solid solutions of cadmium ferrite (CdFe 2O 4) and nickel ferrite (NiFe 2O 4) obtained by prolonged thermal treatment from stoichiometric samples have been investigated by X-ray powder diffraction, magnetic measurements and chemical analysis. The stoichiometric Cd xNi 1−xFe 2O 4 samples were prepared from coprecipitated xCd(OH) 2·(1− x)Ni(OH) 2·2Fe(OH) 3-hydroxides, sintered at 1000°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 Cd 2+-ions. Thermal treatment above 1000°C leads to the defect spinel structures with the Cd 2+-deficiency, composed from solid solutions with the general formula Cd 2+ x−αFe 3+ 1−x+α[Ni 2+ 1−xFe 3+ 1+x−α/3□ α/3]O 4, corresponding to a solid solution of stoichiometric (Cd, Ni)-ferrite with the maghemite, γFe 2O 3.