Photoluminescence properties of Eu3+:RbGd(WO4)2 red phosphors prepared by sol-gel method

RbGd(WO4)2 (RGW) phosphors with different concentration of Eu3+ ions were synthesized by the modified sol-gel method. Powder X-ray diffraction (XRD) with structure refinement, Raman, scanning electron microscopy (SEM), high resolution transmission electron microscope (HR-TEM), photoluminescence (PL) and lifetime analysis were employed to characterize the synthesized phosphors. The crystal structure of RGW was refined and determined to be monoclinic system with the refinement converged to Rp=2.14%, Rwp=8.09%, and X2=6.46 by Rietveld process. The excitation spectra consist of a broad charge transfer band from 240 to 350 nm and several other sharp peaks at around 360-550 nm due to f-f transition of Eu3+ ions. The phosphor exhibits strong red luminescence peak at 616 nm for 5D0→7F2 transitions of Eu3+ ions excited under 395 nm. The critical distance was calculated to be 9.21 Å. In addition, Judd-Ofelt parameters of Eu3+:RGW phosphor were obtained using the emission spectrum and the chromaticity coordinates were found to be (x=0.660, y=0.339). This is closer to the standard values of the National Television Standard Committee (x=0.67, y=0.33).