Molybdenum-doping-induced photoluminescence enhancement in Eu3+-activated CaWO4 red-emitting phosphors for white light-emitting diodes

Abstract

A series of Eu3+-activated CaW1-xMoxO4 red-emitting phosphors were prepared through a high-temperature solid-state reaction route to study the influence of molybdenum ions doping on the luminescent performances of CaWO4:Eu3+ phosphor. Their phase composition, microstructure and luminescent properties were characterized by X-ray diffraction, field-emission scanning electron microscope, photoluminescence spectra and decay curves. Under 280 nm excitation, all the samples exhibited an intense red emission at around 614 nm due to the 5D0 → 7F2 transition of Eu3+ ions, indicating that the Eu3+ ions populated the non-inversion symmetry sites in the host lattices. Furthermore, with the increase of Mo6+ ion concentration, the emission intensity of CaW1-xMoxO4:Eu3+ phosphors was firstly improved, and reached a maximum value at 60 mol% Mo6+. Compared to the CaWO4:Eu3+ sample, the integrated emission intensity of CaW0.4Mo0.6O4:Eu3+ sample was enhanced by about 8.3 times. The temperature-dependent emission spectra showed that the as-prepared phosphors possessed superior thermal stability with an activation energy of 0.239 eV. In addition, the as-prepared phosphors also exhibited good colour coordinates and high colour purity. These characteristics make the CaW1-xMoxO4:Eu3+ compounds promising candidates as red-emitting phosphors for white light-emitting diodes. Finally, the Judd-Oflet theory was used to study the local structure environment surrounding the Eu3+ ions in the host lattices.