Oxygen nonstoichiometry and defect chemistry of the mixed conductor La0.9Ca0.1FeO3 − δ at low oxygen partial pressure

• The oxygen nonstoichiometry of La0.9Ca0.1FeO3 − δ was measured as a function of pO2 and temperature via coulometric titration.
• Measurement at low pO2 reveals an n-type conducting regime.
• The reducibility of La0.9Ca0.1FeO3 − δ is similar to that of La0.9Sr0.1FeO3 − δ.

The equilibrium oxygen nonstoichiometry, δ, for the mixed ionic and electronic conducting perovskite La0.9Ca0.1FeO3 − δ (LCF91) was measured for oxygen partial pressures, pO2, between 10− 3 and 10− 21 atm and temperatures of 750 to 900 °C using a tubular, two-probe Pt|YSZ|LCF coulometric titration cell. XRD experiments confirmed that LCF91 remains a single phase perovskite under the reducing conditions of a fuel electrode, and reveal no evidence of reaction with the zirconia electrolyte. The pO2-nonstoichiometry relationship can be interpreted using a dilute-solution point-defect model involving oxygen vacancies, electrons, and electron holes.