Demixing transient

In concluding, let us comment on the time needed to attain the steady state after establishing the surface activities. Two transient processes having different relaxation times occur I) the steady state vacancy concentration profile builds up and 2) the component demixing profile builds up until eventually the system becomes truly stationary. Even if the vacancies have attained a (quasi-) steady state, their drift flux is not stationary until the demixing profile has also reached its steady state. This time dependence of the vacancy drift is responsible for the difficulties that arise when the transient transport problem must be solved explicitly, see, for example, [G. Petot-Er-vas, et al. (1992)]. 

The quantity of ambipolar conductivity is widely used for the analysis of -> electrolytic permeability of -> solid electrolytes, caused by the presence of electronic conductivity. Other important cases include transient behavior of electrochemical cells and ion-conducting solids, dense ceramic membranes for gas separation, reduction/ oxidation of metals, and kinetic demixing phenomena [iv]. In most practical cases, however, the ambipo-... 

K. Vedula, Modelling of transient and steady-state demixing of oxide solid solutions in an oxygen chamical potential gradients. Oxid. Met., 28 (1987) 99-108. 

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