Chemical looping combustion is an attractive method for CO2 capture in power plants, while maintaining high energy efficiency. The cyclic nature of the process, however, places significant demands on the redox and mechanical characteristics of the oxygen carrier. In this work, NiO/NiAl2O4 and (NiO)(1-y)(MgO)(y)/Ni(1-x)MgxAl2O4 were synthesized by solution combustion and investigated in two forms: porous extruded and dense pressed pellets. The pressed oxygen carriers of both compositions exhibited excellent stability during thermogravimetric analysis at temperatures 800-1200 degrees C with cycling of oxidizing/reducing gases while, due to sintering effects, the extruded pellets showed deteriorating performance. The addition of magnesium to the structure decreased reduction of the spinel, thus stabilizing the support. Attrition tests revealed superior performance of the (NiO)(0.21)(MgO)(0.79)/Ni0.62Mg0.38Al2O4, exceeding that of commercially available sintered iron oxide reference. (c) 2007 Elsevier Ltd. All rights reserved.