J. Jamnik et J. Maier, TRANSPORT ACROSS BOUNDARY-LAYERS IN IONIC-CRYSTALS PART II - STATIONARY CHEMICAL DIFFUSION, Journal of physics and chemistry of solids, 59(9), 1998, pp. 1555-1569
Defect concentration and charge density profiles are derived for a mix
ed conductor MO1+delta with two carriers under a small chemical potent
ial gradient. The description starts from the formulation of the flux
equations for the diffusing species of relevance (e.g. O2- and 2e(-) i
n an oxide), takes account of the Poisson equation and is restricted t
o dilute systems and linear regime. Several examples are discussed in
detail: (i) it is shown analytically that chemical diffusion involving
carriers with different diffusion coefficients leads to a kinetic bui
ld-up of subsurface space charges; (ii) the influence of sluggish surf
ace reactions on the steady state flux and the concentrations profiles
is studied on both a ''black box'' and a mechanistic level; (iii) the
impact of different prototype grain boundaries (amorphous blocking co
re, depletion of carriers in adjacent space charge layers) on chemical
diffusion is treated in detail numerically. (C) 1998 Elsevier Science
Ltd. All rights reserved.