Red, green and blue low-voltage cathodoluminescence of rare-earth doped BaWO4 phosphors

Abstract

Spherical phosphors BaWO4 doped with rare-earth ions (RE = Eu, Tb, Tm) were prepared by the polyol method. The crystal structure and morphology of the powders were investigated using X-ray diffraction, field emission scanning electron microscopy and Fourier transform spectroscopy. The as-prepared BaWO4-based phosphors processed as low as 160 °C show mono-dispersive and highly crystalline nanostructure. The optical characteristics of the phosphors were investigated using low-voltage cathodoluminescence. Efficient energy transfer between the host and RE ions were revealed in the spectra. Red, green and blue cathodoluminescence were observed corresponding to sharp dominant emission peaks located at 616 nm, 545 nm and 473 nm for Eu3+, Tb3+ and Tm3+ doped phosphors, respectively. Those peaks are attributed to the characteristic emission from Eu3+ (5D0 − 7FJ transitions), Tb3+ (5D3 − 7FJ and 5D4 − 7FJ transitions) and Tm3+ (1D2 − 3F4 and 1D2 − 3H4 transitions) under low-voltage (≤5 kV) excitation of electron beam. Luminescent intensities in the annealed BaWO4-based phosphors were significantly enhanced. The characteristics of the phosphors are investigated in terms of luminance, chromaticity and color purity. Fundamental mechanisms responsible for the low-voltage cathodoluminescence of BaWO4-based phosphors are discussed.