Blue-emitting MWO₄:Tm³⁺ (M: Sr, Ba) phosphors prepared by coprecipitation method at room temperature

MWO₄ host matrices (M: Sr, Ba) doped with different Tm³⁺ concentrations (0.02, 0.04, 0.06, 0.08 and 0.10 mol%) have been successfully prepared by the coprecipitation method at room temperature. The as-prepared nanophosphors were characterized by infrared spectroscopy showing intense absorption bands in the range of 700-1000 cm^-1 attributed to the symmetrical and asymmetrical stretching vibrations (ν) of the tetrahedral [WO₄]^2- group. The X-ray diffraction (XRD) measurements reveal the tetragonal scheelite phase with the I4_1/a (No. 88) space group. The emission spectra of the MWO₄:Tm³⁺ materials are dominated by the highest intensity narrow band of the intraconfigurational ¹D₂ → ³F₄ transitions in the blue region (ca. 456 nm) arising from the Tm³⁺ ions. Additional low-intensity emission bands originated from the ¹G₄ → ³H₆ (ca. 475 nm), ¹G₄ → ³F₄ (660 nm) and ³H₄ → ³H₆ (700 nm) transitions are also observed. These optical results indicate that the materials can be used as an alternative to blue-emitting markers. (author)