Non-stoichiometry and chemical diffusion coefficients were measured by means of steady-state and transient thermogravimetry, at 790 to 1200C, under various O partial pressures. At high O partial pressures, the chemical diffusion coefficient ranged from 10-4 to 7 x 10-4cm2/s. This fact, when combined with the high concentrations of disordered vacancies, was suggested to make these materials some of the fastest known solid O-ion diffusers at high temperatures and high O partial pressures. Due to the high defect concentration, the compound transformed from a disordered cubic perovskite to a brownmillerite-type structure, under reduced O partial pressures, at temperatures below about 900C. Due to this phase transition, the mobility of O vacancies decreased by up to about an order of magnitude at 850C. An ordering effect was also observed at 1000C. It was smaller in size, and this was suggested to be due to the short-range ordering of 4-coordinated Fe polyhedra.

Defects and Transport in Sr(Fe,Co)O3. A.Jost, T.Norby, D.Leone: Ionics, 1999, 5[5-6], 434-43