Oxygen carriers based on oxides of Mn and Si in combination with Mg, Al, Ca and Ti (Mn0.63Si0.27X0.1, X = Ca(OH)(2), TiO2, MgO, AIOOH were examined for CLOU (chemical-looping with oxygen uncoupling), in terms of oxygen uncoupling ability and ability to convert both methane and syngas. The focus was on the optimization of the production process to yield mechanically strong oxygen carrier particles with a reasonable activity. For this purpose, 15 types of oxygen carriers were produced by spray-drying and calcined for different time periods and at different temperatures. The oxygen uncoupling behavior and gas conversion of the materials were investigated in a batch fluidized-bed reactor under alternating oxidizing and reducing conditions in the temperature range 850-1050 degrees C. To determine attrition resistance and mechanical stability, a jet-cup attrition rig was used. Furthermore, physical and chemical properties such as specific surface area and crystal phase composition have been determined. For the oxygen carriers with additives of Mg, Al, Ca, Ti, some material combinations showed a significant increase in reactivity and improved mechanical stability compared to the unsupported Mn-Si particles. Changing the production process (milling process and calcination time) just caused slight difference in attrition resistance, gas conversion as well as oxygen release. (C) 2015 Elsevier Ltd. All rights reserved.