MIXED ELECTRONIC AND IONIC-CONDUCTIVITY OF LACO(M)O-3 (M = GA, CR, FEOR NI) - II - OXYGEN PERMEATION THROUGH CR-SUBSTITUTED AND NI-SUBSTITUTED LACOO3

The oxygen permeation fluxes, electrical conductivity and ther mal exp ansion of LaCo1-xCrxO3 (x = 0.1-0.4) solid solutions have been ascerta ined to decrease with increasing chromium concentration. The dependenc e of the oxygen permeability on thickness of the LaCo1-xCrxO3 (x < 0.3 ) dense ceramic membranes suggests a presence of surface-exchange limi tations of the oxygen transport. Introduction of nickel into the cobal t sublattice of LaCo1-xNixO3 has been found to result in a sharp decre ase of the oxygen ionic conductivity which is the flux-limiting factor . Electronic conductivity of the solid solutions increases with nickel content. A prolonged stabilization process to attain stationary oxyge n flux through LaCo(Cr)O-3 and LaCo(Ni)O-3 membranes has been pointed out. Thermal expansion coefficients of the ceramics have been calculat ed from the dilatometric data to be in the range (17.3-23.7)X 10(-6) K -1. (C) 1998 Elsevier Science B.V. All rights reserved.