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

Abstract

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:xDy³⁺ (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.