Demixing of mixed oxide (A,B)O in an oxygen potential gradient: numerical solution of the time evolution of the demixing process

The time evolution of the demixing process in a transition metal oxide soli d solution, (A.B)(1-delta)O, under a stationary oxygen potential gradient i s calculated by solving the governing continuity equations numerically with a finite difference technique. The transient solution of the chemical diff usion process of a monoxide is also computed. From the time variations of t he demixing profile and the spatial distribution of the chemical potential of oxygen in the oxide, it is found that two transient processes are involv ed in demixing leading to the steady state: (1) the establishment of a grad ient in the chemical potential of oxygen across the system oxide; and (2) t he redistribution of the cations leading to demixing. (C) 1999 Elsevier Sci ence B.V. All rights reserved.