Effect of Bi 3+ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One‐Pot Combustion Synthesized Nanocrystalline Bi‐Doped La 2 O 3

La 2‐2x Bi 2x O 3 (x=0‐0.04) nanocrystalline powders are synthesized by one‐pot single step solution combustion method. 4 atom% Bi doped La 2 O 3 reveals the presence of both Bi 3+ and metallic Bi. Temperature programmed reduction (TPR) of La 2 O 3 and La 2−2x Bi 2x O 3 (x=0.005‐0.04) indicates that the oxygen storage capacity changes with the dopant (Bi) concentration. La 2‐2x Bi 2x O 3 (x=0.04) has less hygroscopic behavior compared to La 2 O 3 and shown enhanced stability in an open atmosphere. The direct band gap of La 2 O 3 and La(OH) 3 decreases significantly after Bi doping. Further, PL studies of Bi doped compounds show a blue emission at 458 nm due to 3 P 1 ‐ 1 S 0 transition of the Bi 3+ ion substituted in La 2 O 3 . Emission intensity is maximum with 0.5 atom percent Bi doping, which decreases gradually with increasing Bi 3+ ion concentration. Bi doping also modifies the catalytic activity of La 2 O 3, resulting in higher CO oxidation activity than unsubstituted La 2 O 3 .