F. PRADO; T. ARMSTRONG; A. CANEIRO; A. MANTHIRAM

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2001 vol. 148 p. 7 - 11

0013-4651

The structural stability and oxygen permeation properties of Sr3-xLaxFe2-yCoyO7- with 0  x  0.3 and 0  y  1.0 have been studied at high temperature (800  T  900 °C) and in the oxygen partial pressure range 0.21  pO2  10-5 atm. These phases have a perovskite-related intergrowth structure with tetragonal symmetry, which does not change with temperature up to 1000 °C and when the oxygen partial pressure changes from air to pO2 = 10-5 atm. The oxygen permeation flux of Sr3-xLaxFe2-yCoyO7- membranes increases with increasing Co content, decreases with increasing lanthanum content, and does not change with time. Measurements of oxygen permeation flux as a function of membrane thickness for Sr2.7La0.3Fe1.4Co0.6O7- at 900 °C indicates the oxygen transport is bulk limited for this composition. Assuming that this observation is also valid for other compositions, the ionic conductivity i and the vacancy diffusion coefficient Dv have been estimated. The structural stability and permeation properties of Sr3-xLaxFe2-yCoyO7- are compared with those of the perovskite phases SrFe0.2Co0.8O3- and Sr0.6La0.4Fe0.2Co0.8O3-.