Physicochemical and optical properties of one-pot combustion synthesized Pr doped La2O3/La(OH)3

Different concentrations of Pr doped La<inf>2</inf>O<inf>3</inf> and La(OH)<inf>3</inf> nanopowders are synthesized by solution combustion method. The X-ray diffraction (XRD) analysis confirms the pure phase and hexagonal structure of compounds. The physical and optical properties are investigated and compared. X-ray photoelectron spectroscopy (XPS) confirms the presence of both Pr³⁺ and Pr⁴⁺ in 15 atom % Pr doped La<inf>2</inf>O<inf>3</inf>. The band gap of La<inf>2</inf>O<inf>3</inf> and La(OH)<inf>3</inf> decreases significantly after Pr doping. Further, photoluminescence (PL) studies of Pr doped La<inf>2</inf>O<inf>3</inf>/La(OH)<inf>3</inf> compounds show a sharp green emission due to ³P<inf>0</inf> → ³H<inf>4</inf> transition of Pr³⁺ ions, and the emission properties depend upon the doping concentration. The emission intensity of Pr³⁺ is optimized with concentration. Hydroxides show slightly lower emission intensity compared to oxides. 1 atom % Pr doped La<inf>2</inf>O<inf>3</inf> (La<inf>1.98</inf>Pr<inf>0.02</inf>O<inf>3</inf>) heated at higher temperatures shows slightly higher emission intensity compare to heated at low temperature due to the increase in crystallites size. 1 atom % Pr doped La<inf>2</inf>O<inf>3</inf> (oxide) shows the highest emission intensity in all the compounds (oxides/hydroxides).