Synthesis and luminescent properties of KLa1−x−y(MoO4)2−z(WO4)z:xEu3+, yDy3+ phosphors for WLEDs

Abstract

A series of Dy3+ or/and Eu3+ co-doped KLa(MoO4)2−z(WO4)z phosphors were prepared by a solid state reaction. The as-prepared samples were characterized by X-ray diffraction, field emission scanning electronic microscope, Raman spectra and photoluminescence spectra. The results indicated that the as-prepared samples had a monoclinic structure of KLa(MoO4)2 and both had tungstate and molybdate, and show irregular polyhedron. The optimal reaction temperature and time for synthesizing KLa(MoO4)1.5(WO4)0.5:Eu3+ samples were 900 °C and 4 h, respectively. The optimal doping concentrations of WO42−, Eu3+, and Dy3+ were about 50, 17 and 5 mol%, respectively. The KLa(MoO4)1.5(WO4)0.5:Eu3+ samples could be excited by near-UV chips (394 nm) and blue chips (465 nm), and could emit red light at about 618 nm. The Dy3+ doped KLa(MoO4)1.5(WO4)0.5 samples also could be excited by near-UV chips (389 nm) and emit yellow light due to the 4F9/2→6H13/2 transition of Dy3+. It was found that the emission intensity of Dy3+ decreased and that of Eu3+ declined with increasing Eu3+ concentration due to the energy transfer from Dy3+ to Eu3+. Moreover, the chromaticity color coordinates of Eu3+, and Dy3+ single-doped KLa(MoO4)1.5(WO4)0.5 and Eu3+ and Dy3+ co-doped KLa(MoO4)1.5(WO4)0.5 samples were close to red, green and white light region, respectively. All results indicated that this kind of phosphors exhibited a great potential application in the field of white light diodes.