The Formation of the Cd-bearing Ferrite by the Air Oxidation of an Aqueous Suspension

When the Cd2+/Fetotal ratio in the initial solution is below 0.1, almost all cadmium ions are incorporated into the ferrite with the spinel-type structure by the air oxidation of an aqueous suspension at a pH 9.0 and at 65 °C. The Cd-bearing ferrite thus obtained is a ferromagnet and is oxidized to form a completely oxidized Cd-bearing ferrite at 150 °C in the air; this ferrite is still a ferromagnet and belongs to the Fe2O3–CdFe2O4 binary system, with the same spinel type structure. When the Cd2+/Fetotal ratio in the initial solution increases to 0.5, the crystalline phases formed is complicatedly changed; the products are also significantly affected by the pH value of the suspension. The most favorable pH value at 65 °C to form the Cd-bearing ferrite is proposed to be 10.0.