Electrochemical determination of the oxygen permeability of La1-xCaxCrO3-δ (x=0.27)

The oxygen permeability of La0.73C0.27Cr0.98O3-delta was measured in the ranges of temperature and oxygen partial pressure, 1173 less than or equal to T/K less than or equal to 1373 and 10(-18) less than or equal to P-O2/atm less than or equal to 1, respectively, by using electrochemical permeation cells of which all the mechanical and electrochemical leakage sources were eliminated by cell design and operation. The ionic partial conductivity was derived therefrom and turned out to vary isothermally as sigma(ion) proportional to p(O2)(m) with the oxygen exponent m changing from m approximate to 0 to - 1/2 to + 1/2 as p(O2) increases in its range examined. The ionic carrier was Identified, via electrotransport experiments, as being oxide anions over the entire p(O2) range, thus suggesting the anti-Frenkel disorder as being the majority ionic defects. The ionic conductivity, and the oxygen vacancy diffusivity and redox equilibrium constant therefrom are exhaustively compared with the literature data. (C) 2000 The Electrochemical Society. S0013-4651(99)10-047-8. All rights reserved.