FORMATION OF CADMIUM, ZINC-BEARING FERRITES IN AQUEOUS SUSPENSION BY AIR OXIDATION

Slightly oxidized cadmium, zinc-bearing and cadmium-bearing ferrites h ave been prepared by air oxidation of iron(II) hydroxide suspensions a t initial (Cd + Zn):Fe(tot) mol ratios (r(Cd + Zn)) of 0.10:2.90-1.00: 2.00 at pH 10.0 and 65-degrees-C. The upper limit of Cd:Fe(tot) mol ra tio in the ferrites was found to be about 0.1:1, and for each Zn:(Cd Zn + Fe(tot)) mol ratio in the suspensions upper limits were also fou nd, respectively. The lattice constant a0 and Mossbauer spectra at roo m temperature of the cadmium, zinc-bearing ferrites suggested that at Cd2+:Zn2+ mol ratios of less-than-or-equal-to 0.12:0.43 at the tetrahe dral sites the crystal structure of the ferrites prepared at r(Cd + 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 tha t at r(Cd + Zn) = 0.10:2.90-0.80:2.20, homogeneous mixtures of CdFe2O4 -Fe3O4 and ZnFe2O4-Fe3O4 solid solutions are formed.