Preparation and Performance of SrWO4:RE3+ (RE = Eu, Sm, Pr) Fluorescent Powders for White LEDs

Abstract

The SrWO₄:RE³⁺ (RE = Eu, Sm, Pr) fluorescent powders are synthesized using a high-temperature solid-state method. The phase structures and morphologies of the fluorescent powders are examined using X- ray diffraction and field-emission scanning electron microscopy, respectively. The results reveal that pure phase SrWO₄ can be prepared via calcination at 900 °C for 4 h and that doping with rare-earth ions has no effect on the crystal phase of the fluorescent powders; SrWO₄ powders doped with three rare earth ions all form spherical-like structures. The luminescence properties of the samples are evaluated using a fluorescence spectrometer, and the excitation and emission spectra of the SrWO₄:RE³⁺ (RE = Eu, Sm, Pr) fluorescent powders are analyzed. The results indicate that SrWO₄:Eu³⁺ fluorescent powder can be effectively excited by ultraviolet light at 395 nm and emit red light at 615 nm when a doping concentration of Eu³⁺ is 7%; Sm³⁺ and Pr³⁺ doped SrWO₄ can emit red light at 650 and 687 nm when excited at 406 nm and 460 nm, respectively, with a doping concentration of 5% each. A W-LED device with SrWO₄:Eu³⁺ pink fluorescent powder and a 395 nm UV chip is successfully assembled. The chromaticity coordinates of the device are (0.3055, 0.3532), exhibiting prominent white light. SrWO₄:RE³⁺ (RE = Eu, Sm, Pr) fluorescent powders are expected to be red fluorescent powders for UV-excited white LEDs.