Luminescence properties of Eu3+, Bi3+ coactivated CaLaNbWO8 red phosphors under near UV and blue excitations

Abstract

Scheelite type red phosphors CaLa1-xNbWO8:xEu(3+) (x = 0.01, 0.03, 0.05, 0.1, 0.15, 0.2, and 0.25) and CaLa0.8-yNbWO8: 0.2Eu(3+), yBi(3+) (y = 0.1, 0.15, and 0.2) were prepared by conventional solid state reaction route. The crystalline structure, morphology and absorbance of these phosphors were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and UV Visible absorption spectroscopy. Investigations on their photoluminescent properties indicated that both Eu3+ doped and Eu3+, Bi3+ coactivated samples emit strong red light at 615 nm under both near UV (394 nm) and blue (465 nm) excitations. Bi3+ codoped system showed broadened charge transfer band (CTB) and stronger excitation peaks at 394 and 465 nm. The red emission intensity of CaLa0.8NbWO8:0.2Eu(3+) phosphor is improved by a factor of 2 as 20 mol% Bi3+ is introduced into the system, and is four times stronger than that of the commercial Y2O3:Eu3+ red phosphor. These phosphors are characterized by sharp red emission with color coordinates closer to the standard red phosphors. Thus, the above phosphors could be a promising red candidate for the phosphor converted white light emitting diodes (pc-WLEDs).