Perovskite-type La-Sr-Co-Fe metal oxides have been demonstrated as sorbents in a high-temperature sorption separation process for production of an oxygen-enriched gas stream for oxycombustion application. This paper reports on characteristics and fixed-bed performance of improved perovskite-type sorbents, Sr-Ca-Co-Fe oxides, in comparison with a reference La-Sr-Co-Fe oxide sorbent for high-temperature production of an oxygen-enriched carbon dioxide stream. The optimum composition of Sr0.5Ca0.5Co0.5Fe0.5O2.47 (SCCF) is identified through study of carbonation (oxygen desorption) kinetics of Sr-Ca-Co-Fe oxides with different Ca and Fe concentrations. Carbonation kinetics of SCCF were studied at different temperatures from 700 to 900 degrees C. Below 750 degrees C, interaction of SCCF with carbon dioxide results in formation of Sr and Ca carbonates. At higher temperature, SCCF turns to form oxides of the respective metals under a stream of carbon dioxide. The improved sorbent has a faster oxygen desorption kinetic rate and higher oxygen storage capacity than the reference material. Effects of the operation temperature on the fixed-bed desorption/adsorption process for production of an oxygen-enriched carbon dioxide stream were investigated. Optimal temperatures for adsorption and desorption processes are determined to be 700 and 850 degrees C, respectively. The fixed-bed process can produce an oxygen-enriched stream at an oxygen concentration of 50%. The improved sorbent exhibits a gradually decreased carbonation (oxygen desorption) kinetics in the first few cycles of oxygen sorption and desorption and then stable kinetics in cycles afterward.