Studies on the Thermal Decomposition of Pure and Mixed Hydroxides of Iron(III)—Nickel(II)

Abstract

The decomposition sequence of the pure and mixed hydroxides of iron(III) and nickel(II) containing 0–50 mol% of NiO and the formation of a ferrite phase have been studied using various experimental techniques. DTA plots of pure ferric hydroxide exhibit one endothermic peak at 130° and three exothermic peaks at 210°, 315° and 430°C. It has been confirmed by X-ray, IR spectroscopy and magnetic susceptibility measurements that the first exothermic peak corresponds to the crystallization of α-FeOOH while the second exothermic peak at 315°C corresponds to the formation of α-Fe2O3 and the third one is due to a change in crystallite size of the specimen.The positions of the endothermic peak at 130° and the two exothermic peaks at 210° and 315°C of ferric hydroxide do not vary significantly with the addition of NiO to the ferric oxide. However, there is a shift in the exothermic peak at 430°C. The magnetic measurements of the mixed oxide specimens indicate the possible formation of the ferrite phase within 550°C ...