A new single-phase white-light-emitting CaWO4:Dy3+ phosphor: synthesis, luminescence and energy transfer

A series of single-phase CaWO4:Dy3+ phosphors have been prepared via a conventional solid state reaction process. X-Ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and fluorescent decay curves were used to characterize the synthesized samples. Under UV light excitation, the CaWO4 sample shows a blue emission in a broad band centered at about 415 nm originating from the WO42- groups, while the Dy3+ ions doped CaWO4 samples show strong line emissions coming from the characteristic f-f transitions due to an efficient energy transfer from WO42- to Dy3+. The decreases of decay lifetimes of host emissions in CaWO4:Dy3+ demonstrated the energy transfer from the host to Dy3+. The energy transfer mechanism in CaWO4:Dy3+ phosphors has been determined to be a resonant type via a dipole-dipole mechanism. By simply controlling the doping concentration of Dy3+, the PL color of CaWO4:Dy3+ phosphors varies from blue to yellow-green, and especially the white light emission is realized in CaWO4:xDy(3+) (x = 0.06). The PL properties of the as-prepared materials indicate that CaWO4:Dy3+ could potentially serve as a single-phase white-light-emitting phosphor in solid-state lighting and display fields.