Effect of Bi3+ Ion Concentration on Physicochemical, Optical and Catalytic Properties of One-Pot Combustion Synthesized Nanocrystalline Bi-Doped La2O3

La<inf>2-2x</inf>Bi<inf>2x</inf>O<inf>3</inf> (x=0-0.04) nanocrystalline powders are synthesized by one-pot single step solution combustion method. 4 atom% Bi doped La<inf>2</inf>O<inf>3</inf> reveals the presence of both Bi³⁺ and metallic Bi. Temperature programmed reduction (TPR) of La<inf>2</inf>O<inf>3</inf> and La<inf>2−2x</inf>Bi<inf>2x</inf>O<inf>3</inf> (x=0.005-0.04) indicates that the oxygen storage capacity changes with the dopant (Bi) concentration. La<inf>2-2x</inf>Bi<inf>2x</inf>O<inf>3</inf> (x=0.04) has less hygroscopic behavior compared to La<inf>2</inf>O<inf>3</inf> and shown enhanced stability in an open atmosphere. The direct band gap of La<inf>2</inf>O<inf>3</inf> and La(OH)<inf>3</inf> decreases significantly after Bi doping. Further, PL studies of Bi doped compounds show a blue emission at 458 nm due to ³P<inf>1</inf> - ¹S<inf>0</inf> transition of the Bi³⁺ ion substituted in La<inf>2</inf>O<inf>3</inf>. Emission intensity is maximum with 0.5 atom percent Bi doping, which decreases gradually with increasing Bi³⁺ ion concentration. Bi doping also modifies the catalytic activity of La<inf>2</inf>O<inf>3,</inf> resulting in higher CO oxidation activity than unsubstituted La<inf>2</inf>O<inf>3</inf>.