Phase stability of la_0.5Sr_0.5CoO_3-y films upon annealing in hydrogen atmosphere

The effect of annealing epitaxial La0.5Sr0.5CoO 3-y films in forming gas (FG) mixed with 0.01%, 0.1%, and 1 % mol oxygen was investigated using in situ x-ray diffraction at temperatures up to 800 °C. The phase transition that occurs at 275 °C in pure FG is shifted to higher temperatures by small admixtures of oxygen in FG. Electron diffraction patterns demonstrate that this is a transition into an oxygen-deficient ordered phase with 0,1/3,0 and 0,2/3,0 superstructures. The La0.5Sr0.5CoO3-y phase can be recovered by annealing in oxygen at moderate temperatures as long as it has not decomposed at higher temperatures. © 2006 American Institute of Physics.