The mechanism and kinetics of thermal decomposition of Co 3− xNi xO 4

Abstract

Thermal decomposition of Co 3− x Ni x O 4, x = 0.1, 0.15 and 0.2, at oxygen pressures 2.7–20.0 kPa at linearly growing temperature was examined. Decomposition of Co 3− x Ni x O 4 was found to be mixed-control diffusion–reaction process. Observed activation energy of studied process strongly depends on the oxygen pressure–dissociation pressure ratio. Comparison of the results obtained with earlier study on electrical conductivity of Co 3− x Ni x O 4 showed linear correlation between activation energy of new phase nucleation and activation energy of electrical conductivity. Transport of electrons from oxygen ions to Co 3+ ions leading to CoO nuclei formation was found to be one of two rate limiting steps of thermal decomposition of Co 3O 4.