Crystal structure and luminescent properties of Li+ ions doped double tungstate KEu(WO4)2 red emitting phosphors

Abstract Li+ ions doped double tungstate KEu(WO4)2 phosphors were prepared by using sol-gel method. The crystal structure and luminescence properties of K1-xLixEu(WO4)2 (0 ≤ x ≤ 0.5) were characterized by means of X-ray diffraction (XRD) Rietveld refinement, photoluminescence and absorption spectra. The results show that the addition of Li+ ions can change the lattice parameters, Eu–O and W–O bond distance of K1-xLixEu(WO4)2. The phosphors consist of K1-xLixEu(WO4)2 and LiEu(WO4)2 phase as the concentration of Li+ is over 0.2 and the volume fraction of LiEu(WO4)2 increase with increase of Li+ ions concentration. The dopant of Li+ in KEu(WO4)2 obviously enhance band gap energy. Under excitation at 393 nm, K0.7Li0.3Eu(WO4)2 phosphor exhibits strongest red emitting light at 615 nm from 5D0 → 7F2 transition of Eu3+ ions. K0.7Li0.3Eu(WO4)2 phosphor shows higher thermal activation energy than that of KEu(WO4)2 phosphors, better thermal stability, the long lifetime value and better internal quantum efficiency.