Interdiffusion Studies of the System Fe _x O‐MgO

Abstract

The solid‐state reaction between Fe,O and MgO is best described as counterdiffusion of the magnesium and iron ions through a relatively rigid oxygen ion lattice of the rock salt structure. A relation between a mutual diffusion coefficient and a controlled cation vacancy concentration was determined by an analysis of the concentration‐penetration curve of the Fe,O‐MgO solid solution. The diffusion coefficient increased approximately exponentially with a linear increase of the cation vacancy concentration. This may be represented by a linear increase of the entropy of activation with vacancy concentration. The enthalpy of activation for the diffusion reaction, 47.5 kcal per mole, remained independent of vacancy concentration.