The aim of the proposal is to investigate changes in the crystal structure of A-site disordered La0.5Ba0.5CoO3-d; and layered LnBaCo2O6-d; (Ln = La, Y) perovskites at high-temperatures under a nitrogen atmosphere. These materials show reversible loss and gain of oxygen under temperature cycling and are of interest for a wide range of applications including as cathodes in solid oxide fuel cells. We are interested in chemical looping, where the oxidation/reduction of the metal oxide is used to drive chemical reactions. This experiment will enable us to determine which oxygen sites are preferably emptied and re-populated. Variable temperature neutron powder diffraction studies on the analogous Pr and Nd materials have been reported but there is no detailed neutron study of the La and Y materials yet, perhaps due the greater difficulty in synthesising phase pure materials.