Effect of Dopants on Oxidation Reaction of Cobalt(II) Oxide

Abstract

The effect of dopants (Li₂O, Al₂O, In₂O₃, Ga₂O₃) on the oxidation reaction and the electrical conductivity of cobalt(II) oxide were investigated. The kinetic data obtained in the temperature range from 450° to 700°C in oxygen atomosphere were expressed by Jander's equation. The oxidation rate of pure CoO was proportional to Po₂^1/6. The trivalent dopants increased and the monovalent decreased the oxidation rate of CoO. The activation energies for the oxidation of pure and trivalent oxides doped, and Li₂O doped CoO were 33, and 37 kcal/mol, respectively. The effect of dopants on the electrical conductivity conformed to the theory of doping.
These results and the defective structure of the spinel Co₃O₄ suggest that the oxidation rate of CoO is controlled by the diffusion of cobalt ions, Co²⁺, in the spine! layer.