Dimensional and phase changes of four candidate oxygen carrier materials for chemical looping combustion are investigated by dilatometry and high-temperature X-ray diffraction during four redox cycles. NiO/Ni2AlO4 does not exhibit significant dimensional changes during cycling, and it is shown that the support material also contributes to the oxygen carrying capacity. CaMn0.875Ti0.125O3 exhibited good chemical stability and small dimensional changes upon redox cycling. Cu0.95Fe1.05AlO4 showed a one-dimensional expansion of 9% after the experiments, and significant phase changes were seen. The complex set of reactions occurring during redox cycling of ilmenite (FeTiO3) was shown to be accompanied by dimensional changes, giving non-steady dimensional changes during the oxidation and reduction steps.