Electronic structure and luminescence studies of Bi doped MgO nanophosphors

Mg1−xO:Bix (x = 0.01–0.5 mol%) nanophosphors have been prepared using the solution combustion method and subsequent annealing at 1173 K in air. Rietveld refinement on X-ray diffraction (XRD) data confirmed the rock-salt phase formation in pure and Bi3+ doped MgO (space group; Fm‾3m). Lower Bi3+ ion concentrations in Mg1−xO:Bix (x = 0.01 and 0.05 mol%) lead to tensile strain and increased lattice parameters of MgO. Higher doping concentrations of Bi3+ ions (x = 0.1–0.5 mol%) lead to a decrease in the lattice strain, unit cell parameters, and Mg–O bond length. Transmission electron microscopy (TEM) images along with selected area electron diffraction (SAED) patterns confirmed the crystalline nature of Mg1−xO:Bix samples with an average particle size of ∼37.5 nm. X-ray absorption spectroscopy (XAS) results at the Mg K-edge and Bi L-edge confirmed the Mg2+ ions and Bi3+ ions in Mg1−xO:Bix samples throughout the Bi doping range. O–K edge XAS conveys the hybridization of the frontier orbitals of O and Bi atoms. UV–visible absorption spectroscopy measurements convey the defect-induced absorption peak shifting in Mg1−xO:Bix compounds. Dopant and host defect-assisted PL emission is observed, with prominent emission in the blue region owing to the transition between 3P1 to 1S0 and 3P0 to 1S0 of Bi3+. The quenching effect on PL properties has been observed beyond 0.05 mol% doping of Bi3+ ions. The presence of various defect states and their stability with re-trapping and charge transfer behaviour have been analyzed by thermoluminescence studies of gamma-irradiated samples, which enable the Mg1−xO:Bix samples for potential applications in display device dosimetry.