Figure 4: O2 concentration profile in inert cycles. Tests were carried out on the 5.6% MgO 1300 sample. (a) inert cycles at 900°C; (b) 1800 s inert cycle at 1000°C. For the experiments in Figure 4(a), three cycles were conducted before and following the fuel cycles. In Figure 4(b), the oxidation was performed at 900°C