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 R_p=2.14%, R_wp=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). - Highlights: • Eu³⁺:RGW phosphors were synthesized by the modified sol–gel method. • Exhibits strong red emission at about 616 nm (⁵D₀→⁷F₂) under the excitation of NUV and blue LEDs. • Decay measurement and Judd–Ofelt parameter were calculated and dicussed. • These phosphors are potential candidates as red source for white LEDs application.