Phase transitions and optical properties of Tb3+activated NaY (WO4)2 phosphors

Well-defined NaY(WO4)2:Tb3+ nanoflowers were prepared through the controllable structural transition of hydroxyl sodium yttrium tungstate precursor, which exhibit a fascinating luminescent property as activated by Tb3+ dopant. NaY(WO4)2:Tb3+ nanoflowers were systematically characterized with a series of tests including XRD, SEM, FT-IR, TG-DTA, UV-Vis, and PL. XRD analyses indicate that NaY(WO4)2:Tb3+ crystalizes in the scheelite structure with broadened diffraction peaks and expanded cell volume with increasing Tb3+ content as revealed by Rietveld refinement. FT-IR and TG-DTA results show that NaY(WO4)2:Tb3+ is formed via the structural transition of hydroxyl sodium yttrium tungstate at calcination temperature above 600 degrees C. UV-Vis test discloses the bandgap red-shift of NaY(WO4)2 via doping Tb3+ ions. Noticeably, PL measurement discloses the green luminescence of NaY(WO4)2:Tb3+ attributable to 5D4 -> 7F5 transition with the optimal Tb3+ doping content of 13 mol%, which manifests the effective energy transfer from WO42- groups to Tb3+ ions and reveals relatively good thermal stability. Furthermore, the tunable color emission from blue to green to yellowish green can be achieved in flower-like NaY(WO4)2:Tb3+ phosphors by controlling the doping content of Tb3+ ions, which may provide promising application in the field of multicolor lighting and displays.