For Cr2O3-free samples, Sb6O13 was identified as the secondary phase, which was replaced by the CrBi18O30 and Co2Cr0.5Sb0.5O4 phases for the samples doped with 0.2–0.4 mol% Cr2O3. When increasing the contents of Cr2O3 up to 0.5–0.6 mol%, the secondary phase was turn into MnCr2O4. This indicates that Cr2O3 has an impact on the lattice distortion