Formation of cadmium, zinc-bearing ferrites in aqueous suspension by air oxidation
Abstract
Slightly oxidized cadmium, zinc-bearing and cadmium-bearing ferrites have been prepared by air oxidation of iron(II) hydroxide suspensions at initial (Cd + Zn):Fetot mol ratios (rCd + Zn) of 0.10:2.90–1.00:2.00 at pH 10.0 and 65 °C. The upper limit of Cd: Fetot mol ratio in the ferrites was found to be about 0.1:1, and for each Zn:(Cd + Zn + Fetot) mol ratio in the suspensions upper limits were also found, respectively. The lattice constant a0 and Mössbauer spectra at room temperature of the cadmium, zinc-bearing ferrites suggested that at Cd2+:Zn2+ mol ratios of ⩽0.12:0.43 at the tetrahedral sites the crystal structure of the ferrites prepared at rCd + Zn= 1.00:2.00 is that of zinc-bearing ferrites and approaches that of cadmium-bearing ferrites with increasing Cd2+ :Zn2+ mol ratio. Also that at rCd + Zn= 0.10:2.90–0.80:2.20, homogenous mixtures of CdFe2O4–Fe3O4 and ZnFe2O4–Fe3O4 solid solutions are formed.