Blue-green, red, and white light emission of ZnWO₄ -based phosphors for low-voltage cathodoluminescence applications

ZnWO4 and ZnWO4: Eu3+ particles were prepared by refluxing in water solution using polyethylene glycol as a capping agent and then annealed at different temperatures. The samples were characterized by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy, and cathodoluminescence spectra. The as-prepared amorphous samples annealed at high temperature (500-700°C) are sanmartinite structure of ZnWO4, and the spherical morphologies are basically retained, except for the increase of the particles size (from 28 to 56 nm). The low-voltage luminescent properties of these tungstate phosphors can be tuned by the doping of Eu3+ ions and annealing treatment. ZnWO4 and ZnWO4: Eu3+ particles annealed at 500°C or above exhibit strong blue-green and white light emission under the excitation of low-voltage electron beams, respectively, the former originating from the intrinsic WO 6 6- complex, and the latter due to the combination of the emissions arising from the intrinsic WO 6 6- and doped Eu3+ ions. The as-prepared ZnWO4: Eu3+ particles only emit a red light resulting from the D5 0 → F7 J (J=1, 2, 3, 4) transitions of Eu3+ ions.