NONSTOICHIOMETRIC SOLID-SOLUTIONS DURING FORMATION OF CD NI FERRITES/

Cadmium-nickel ferrites prepared by different procedures from coprecip itated amorphous xCd(OH)2.(1-x)Ni(OH)2. 2Fe(OH)3 mixtures have been in vestigated by X-ray, magnetic and thermogravimetry techniques. In the preparations obtained by hydrothermal methods at 100 and 150-degrees-C there is a marked tendency to form solid solutions between the nickel and cadmium ferrites for lower values of x, but for higher x the latt ice parameters suddenly decrease, indicating the formation of solid so lutions between CdFe2O4 and maghemite, gamma-Fe2O3. It has been found that during a gradual heating of dried, initially amorphous mixtures o f hydroxides, several distinct nonstoichiometric intermediate phases o f Cd/Ni ferrites arose before the final product, corresponding to the nominal composition was formed. Prolonged thermal treatment at T great er-than-or-equal-to 1000-degrees-C, because of the Cd volatility, lead s again to the defect structure solid solutions between the cadmium-ni ckel ferrites and maghemite.