In this work, calcium-based sorbents were developed by doping metal oxides through the sol–gel process based on orthogonal design. Metal oxides of high melting point such as MgO and MnO2 were chosen to dope into the sorbents to enhance their sin- tering resistance and attempt to overcome the decay problem with CaO. The effect of steam on the reactivity of synthesized sorbents in the carbonation, calcination and both the carbonation and calci- nation atmosphere was investigated. Pore characteristics were also measured as a supplement to the reaction study.