Oxygen stoichiometry and phase transitions of SrCo1-xFexO3-delta

The oxygen stoichiometry of SrCo1-xFexO3-delta (0.1 less than or equal to x less than or equal to 0.9) solid solutions was determined by solid-electro lyte coulometry as a function of temperature (20-1000 degreesC) and oxygen partial pressure (1-100 Pa). The results, together with X-ray diffraction s tudies between 400 and 900 degreesC, indicated a sequence of phase transiti ons: perovskite. --> brownmillerite --> high-temperature perovskite. The co mposition stability region of the parent perovskite structure was shown to be 0.2 < x <less than or equal to> 1.0. The Co-rich samples (x less than or equal to 0.2) consisted of perovskite and hexagonal phases.