Influence of crystal structure on the Co(II) diffusion behavior in the Zn(1−x)CoxO system

Abstract

The solid state interaction of the Zn(1−x)CoxO nominal system is investigated by means of diffusion couples and analysis of co-precipitated samples. The formation of a homogeneous Co:ZnO solid solution is found to be determined by the crystal structure from which Co(II) ions diffuse into the wurtzite lattice. No diffusion is observed whenever the CoO rock-salt structure is formed from the Co(II) precursor. On the contrary, the diffusion from the Co3O4 spinel phase is feasible but has a limited temperature range defined by the reduction at a high temperature of Co(III)–Co(II), since this process again leads to the formation of the rock-salt structure. However, when using a highly reactive and homogeneous co-precipitated starting powder, neither the spinel phase nor the rock-salt structure is formed, and a Co(II):ZnO solid solution is obtained, which remains stable up to high temperatures.