Materials for Solid Oxide Fuel Cells (SOFCs) are being developed continuously. Cuprous delafossites (CuBO2 where B=Cu, Cr) are being developed for cathode side applications in SOFCs, due to their semiconducting properties. CuFeO2 transforms from delafossite to spinel in an oxidising atmosphere at high temperatures, while CuCrO2 is stable. Solid solution compositions between these two parents also experience the transition. Data on four samples will be collected: CuFe1-xCrxO2 (x=0, 0.25, 0.5 and 1). Study of the role of oxygen in the mechanism of the delafossite-spinel transition is important ¿ the identification of intermediate phases, oxygen incorporation and transport in the structure will clarify the structure-property relationships of these systems, and the mechanism through which the delafossite-spinel transition occurs. This is important for further material development.