Synthesis and structure of oxygen-deficient La2NiCoO5 and LaSrCo2O5 phases

Abstract

The La₂NiCoO₅ and LaSrCo₂O₅ phases have been synthesized by the temperature-programmed reduction (TPR) of the parent mixed perovskites LaNi_0.5Co_0.5O₃ and La_0.5Sr_0.5CoO₃, respectively, under an ammonia atmosphere. While La₂NiCoO₅ adopts a structure similar to the vacancy-ordered La₂Ni₂O₅, LaSrCo₂O₅ crystallized in a brownmillerite-like structure. The reactivity of the perovskite oxides towards reduction by ammonia and the structure of the product oxides are found to be guided by factors such as the coordination and oxidation state of the transition-metal cations.