Synthesis, crystal structure and photoluminescence properties of high-color-purity red-emitting SrLu2O4:Eu3+ phosphors with excellent thermal stability

Abstract

Red-emitting SrLu2O4:Eu3+ phosphors were prepared by a high-temperature solid-state reaction approach, and they were characterized by X-ray diffraction (XRD), excitation and emission spectra, luminescence decay lifetimes, CIE chromaticity coordinates, and temperature-dependent emission spectra. Rietveld refinement of XRD pattern revealed that the SrLu2O4:Eu3+ phosphors crystallized into orthorhombic crystal system with a space group of Pnma and cell parameters of a = 9.962(1) Å, b = 3.343(5) Å, c = 11.746(2) Å, α = β = γ = 90°, and V = 391.24(3) Å3. Under 395 nm excitation, these SrLu2O4:Eu3+ phosphors showed intense red emissions in the 550-750 nm wavelength range with peaks around 581, 593, 611, 653, and 708 nm, corresponding to the 5D0→7FJ (J = 0-4) transitions of Eu3+ ions. Investigation on Eu3+ doping concentration dependent emission spectra demonstrated the critical quenching concentration of Eu3+ ions was 9 mol%. The luminescence decay lifetimes declined from 1.77 to 1.51 ms with increasing Eu3+ concentration from 1 to 10 mol%. Notably, the CIE chromaticity coordinates (0.646, 0.354) of composition-optimal SLO:9%Eu3+ phosphors were close to the standard red light (0.67, 0.33), and its color purity reached as high as 94.1%. Finally, it was found that the SLO:9%Eu3+ phosphors also had excellent thermal stability and color stability at higher temperatures. The emission intensity at 423 K was dropped to 89% of that at 303 K, and the activation energy of thermal quenching was 0.32 eV.