Relaxation of point defects during interdiffusion of oxides in solid solution

Abstract

For interdiffusing NiO-CoO oxides, the local cation vacancy concentration is determined as a function of time by subsequent spinel precipitation at sufficiently low temperature. From the known equilibrium data of point defect concentrations, one can evaluate the cation vacancy supersaturation during reaction due to insufficient vacancy relaxation at outer and inner surfaces. As a consequence of the sluggish defect relaxation processes, the interdiffusion coefficients D̃( x) are not any more functions of the composition alone, but become (in contrast to local equilibrium state functions) dependent on sample geometry and time explicitly.