ELECTRON MICROSCOPY STUDY OF THE `CUBIC` PEROVSKITE PHASE SrFe1 - xVxO2. 5 + x (0. 05 less than equivalent to x less than equivalent to 0. 1).

The oxygen-deficient 'cubic' perovskite phase SrFe//1// minus //xV//xO//2//. //5// plus //x (0. 05 less than equivalent to x less than equivalent to 0. 10) quenched from 1473 K has been investigated by electron microscopy. Samples show a microdomain structure composed of ordered grains less than 20 nm. Oxygen vacancies form a brownmillerite-type superlattice in each microdomain, while six orientation variants have been observed within a particle; the oxygen vacancies in one domain are stringed along one of the six possible LT AN BR 110 RT AN BR //c directions of the cubic host lattice. The domain size decreases as x or oxygen content increases. Vacancy arrangements within the domains observed in high-resolution lattice images indicate that good structural coherence exists between microdomains and that a basic cubic perovskite skeleton is framed throughout a particle; they also suggest that vacancy content decreases in the boundary regions.