Effect of surface properties on cobalt modification of iron oxides

Nine different gamma Fe₂O₃ samples were surface-modified with Fe²⁺ and Co²⁺ ions. The coercivity (H_c), the specific surface area (SSA), and the acid-base characteristics of the core particles were measured, as well as the coercivity of the final product. A relationship was found between the integral surface charge density of the core particles and the surface efficiency, defined as the difference between the final and the initial H_c normalized by the SSA at a constant amount of Fe²⁺ and Co²⁺. The technological importance of this finding is that the efficiency of the cobalt doping process can be related to measurable surface properties of the core particles