A thermogravimetric study of the phase diagram of strontium cobalt iron oxide, SrCo0.8Fe0.2O3 − δ

The phase diagram of the nonstoichiometric oxide SrCo0.8Fe0.2O3 − δ has been determined as a function of temperature (550 °C ≤ T ≤ 900 °C) and oxygen partial pressure (0.015 atm ≤ pO2 ≤ 1 atm) by thermogravimetric analysis. Two phases are observed, perovskite and brownmillerite, separated by a two phase region. Above 770 °C only the phase with the perovskite structure is stable. Over the range of conditions studied, the perovskite phase has maximum and minimum oxygen contents of 3 − δ = 2.65 (550 °C, pO2 = 1 atm) and 3 − δ = 2.43 (850 °C, pO2 = 5 × 10−4 atm), respectively.