Effects of annealing temperature, doping concentration, and excitation wavelength on photoluminescence characteristics of GdOCl:Bi3+ phosphor powders

This study presents a novel investigation of the structure, particle morphology and photoluminescence (PL) characteristics of Gd1-xOCl:Bix phosphors prepared by a solid-state reaction method. X-ray diffraction data confirmed the formation of the tetrahedral GdOCl phase. The phosphors emitted peculiar photoluminescence that was dependent on the excitation wavelength, annealing temperature and doping concentration. When undoped GdOCl host was excited at 275 nm, a narrowband ultraviolet B (UVB) was observed at 315 nm. This emission is ascribed to the 8S7/2 → 6IJ transition of Gd3+. After doping with Bi3+, two excitation bands were observed at 275 nm (major excitation) and 336 nm (minor excitation). Exciting Bi3+ doped GdOCl at 275 and 366 nm resulted in two broad emission bands at 455 nm (bluish green) and 428 nm (blue) ascribed to and 3P0,1 → 1S0 transitions of Bi3+. The PL peak intensities of these emissions were found to vary with Bi3+ doping concentrations and annealing temperatures. The decay characteristics and photoluminescence quantum yield of the blue photoluminescence were determined, and the mechanism of the blue Bi3+ emission is proposed.