Mass and charge transport properties of La0.9Ca0.1FeO3- δ

The mixed ionic electronic conducting perovskite La0.9Ca0.1FeO3 - (delta) (LCF91) was synthesized via a glycine-nitrate process. XRD measurements and Rietveld analysis showed LCF91 as the main phase and a minor amount of brownmillerite Ca2Fe2O5 as secondary phase. The oxygen exchange kinetics and the electronic conductivity of LCF91 were determined as functions of the oxygen partial pressure (1 x 10(-3) <= pO(2)/bar <= 0.1) and temperature (600 <= T/degrees C <= 800). The chemical surface exchange coefficient kalem and the chemical diffusion coefficient of oxygen Daiwa, were obtained from in-situ dc-conductivity relaxation experiments. High values of k(chem) = 9 x 10(-4) cm s(-1) and D-chem = 7 x 10(-6) cm(2) s(-1) were obtained at 800 degrees C and pO(2) = 0.01 bar. The activation energies for k(chem) and D-chem were in the range of 33 <= E-a/kJ mol(-1) <= 43 and 61 <= E-a/k(J) mol(-1) <= 67, respectively. The oxygen nonstoichiometry of LCF91 was described by a point defect model to obtain the concentrations of electronic and ionic defects as a function of pO(2) and temperature. Based on the defect model, the thermodynamic factors of oxygen and oxygen vacancies were determined. Self-diffusion coefficients for oxygen and oxygen vacancies were estimated to 13 x 10(-9) <= D-O/cm(2) s(-1) <= 1.2 x 10(-8) and 6.3 x 10(-7) <= D-V/cm(2) s(-1) <= 2.5 x 10(-6) at 700-800 degrees C, respectively. The electronic and ionic conductivities were in the range of 28 <= sigma(e)/S cm(-1) <= 35 (600-800 degrees C) and 5.7 x 10(-6) <= sigma(i)/S cm(-1) <= 4.9 x 10(-4) (700-800 degrees C), respectively. (C) 2016 Elsevier B.V. All rights reserved.