The influence of lithium ion incorporation on the luminescence enhancement of Gd2O3:Pr3+ nanophosphors for lighting applications

Abstract

In this study, nanosized Gd2O3: Pr3+ and Li+ co-doped Gd2O3: Pr3+ were synthesised by solution combustion method for analysing the structural, morphological and optical properties. X-ray diffraction patterns of as-prepared Gd2O3:Pr3+ indicated the existence of multiphase crystallites and it transformed to pure cubic phase upon annealing. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images confirmed that the particles are spherical. Upon 321 nm excitation, Gd2O3: Pr3+ phosphor exhibits characteristic emission bands at 613 nm, 529 nm and 439 nm. The photoluminescence emission intensity was found maximum for 2 wt% Pr3+ doped Gd2O3 powders. Li+ ions were co-doped into this Gd2O3:Pr3+ phosphor and were found to induce a considerable enhancement in PL emission intensity. Lithium co-doped samples crystallize in cubic structure. Raman spectra of the Li+ co-doped phosphors revealed characteristic Ag+ Fg mode of the cubic phase of Gd2O3, apart from other independent modes. The maximum emission intensity was obtained for 0.5 wt% Li+ co-doped samples, with an improved intensity of about 2.87 times that of Gd2O3:Pr3+. The new composition Gd2O3: Pr3+: Li+ with enhanced luminescence properties can be employed as a red light emitting phosphor for white light emitting diodes (WLEDs).