Abstract
A formalism for tracer diffusion in nonstoichiometric compounds is developed at the Bragg-Williams approximation along parallel lines with the Anderson theory of nonstoichiometry. It is specifically assumed that both components of a Frenkel pair may contribute independently to the diffusion coefficient. The equation for the tracer diffusion coefficient leads to a “transition” region in a In D ∗ vs 1 T plot for one side of stoichiometry. In this region the slope may attain the value of the sum of the high and low temperature branches. It is also shown that under certain conditions the compositional behavior of the activation energy of diffusion should parallel the compositional behavior of the heat of solution. The success of the mass action law approach, as manifested in ln D ∗/ln po 2 plots in the case of nonstoichiometric oxides, is also shown to be due to a self cancellation of terms involving defect interactions.
Published Version
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