Chemical looping combustion (CLC) technology is a promising CO2 capture technology with advantages inherent to CO2 separation and energy gradient utilization. The oxygen carrier itself is considered one of the most important parts of the CLC technology that provides fuel conversion and system economy. Iron-based oxygen carriers are promising candidates for CLC; doping them with Bi2O3 may further improve their reactivities through oxygen vacancy formation that is promoted by high anion conductivity and reducibility. Hence, in this study, the effects of Bi2O3 concentrations and calcination temperatures on the reactivity of iron-based oxygen carriers were parametrically investigated using TGA and bench-scale CLC experiments. Additionally, the oxygen carriers were analytically characterized before and after CLC testing using X-ray diffraction, scanning electron microscopy/energy dispersive spectrometry, and Brunauer-Emmett-Teller surface area/porosity measurements. The analytic results showed that addition of Bi2O3 did not affect surface areas to any significant extent; however, it did increase average pore sizes. The CLC data showed that Bi2O3 addition improved the oxygen carriers' reactivities by decreasing the reduction activation energy and caused BiFeO3 solid solutions to form which, because of the introduction of more labile lattice oxygen transfer, may increase surface reactivity.