MIXED ELECTRONIC AND IONIC-CONDUCTIVITY OF LACO(M)O-3 (M = GA, CR, FEOR NI) - III - DIFFUSION OF OXYGEN THROUGH LACO1-X-YFEXNIYO3+ -DELTA CERAMICS/

Formation of solid solutions with the rhombohedrally-distorted perovsk ite structure has been found in the LaCo1-x-yFexNiyO3 (x=0.1-0.2; y=0. 1-0.3) oxide system. Introducing nickel into the perovskite lattice le ads to increasing oxygen nonstoichiometry and electrical conductivity and decreasing thermal expansion. The effect of doping by iron has bee n demonstrated to be the opposite. Averaged thermal expansion coeffici ents of the ceramics at 300-1100 K are in the range (18.0 - 20.8)X 10( -6) K-1. For the solid solutions with equal concentrations of nickel a nd iron, oxygen permeation is limited predominantly by the bulk ionic conductivity. Further substitution of cobalt with nickel results in a sharp increase in the permeation flux due to increasing oxygen nonstoi chiometry which is accompanied by an occurrence of the surface exchang e limitations of the oxygen transport. The activation energy for elect rical conductivity of the perovskites has been calculated to be 10.8-1 8.4 kJ mol(-1). (C) 1998 Elsevier Science B.V. All rights reserved.