Oxygen permeability of La2Cu(Co)O4+delta solid solutions

Formation of the La2Cu1-xCoxO4+delta solid solutions with orthorhombic K2Ni F4-type structure was found to be in the range of 0 less than or equal to x less than or equal to 0.30 at temperatures above 1270 K. Incorporating cob alt into the copper sublattice of lanthanum cuprate leads to increasing oxy gen hyperstoichiometry and decreasing electrical conductivity. Thermal expa nsion coefficients of the La2Cu1-xCoxO4+delta (x = 0.02-0.30) ceramics at 4 70-1100 K were calculated from the dilatometric data to vary in the range ( 12.2-13.2) x 10(-6) K-1. Studying the dependence of oxygen permeation fluxe s through La,Cu(Co)O4+delta on the membrane thickness demonstrated that the oxygen transport at the thickness values below 1 mm is limited by both sur face exchange rate and bulk ionic conductivity. Oxygen permeability of the La2Cu1-xCoxO4+delta solid solutions was ascertained to increase with cobalt concentration at x = 0.02-0.10 and to decrease with further dopant additio ns, indicating a participation of interstitial oxygen in the ionic transpor t. (C) 1999 Elsevier Science B.V. All rights reserved.