High Temperature Oxidation Mechanism of CoO to Co3 O 4

Growth of Co 3 O 4 layers on the (100) surface of single crystal CoO was investigated in air at 700° and 800° C. These layers were of duplex structure due to simultaneous inside and outside growth. Measurements on the position of inert gold markers demonstrated that cobalt migration outward in Co 3 O 4 was the dominant diffusion mechanism. The oxidation kinetics were parabolic; the parabolic rate constant at 800°C was used to obtain an estimate of D Co = 3.0 × 10 − 12 cm 2 / sec for the self‐diffusion coefficient of cobalt in Co 3 O 4 .