Improved thermal stability of the red-emitting Gd3+ - Modulated La2LiSbO6:Eu3+ phosphors for WLED

Red-emitting phosphors play an important role in the warm white light emitting diodes (LEDs). However, the development of red phosphors with high luminous efficiency and high thermal stability still faces severe challenges. A series of novel red emitting Eu3+ doped La2LiSbO6 phosphors have been synthesized by the conventional solid-state reaction route. The effects of sintering temperatures as well as co-doped Gd3+ ions were discussed. X - ray diffraction (XRD), photoluminescence excitation (PLE) and emission (PL) spectra, temperature-dependent photoluminescence spectra, and CIE chromaticity coordinates were used to analyze these phosphors. The optimum sintering temperature for La2LiSbO6: Eu3+ phosphors was 1200 °C. The emission intensity reached the maximum when Eu3+ ion concentration was 18 mol%, and the dipole-dipole interaction may be responsible for the concentration quenching mechanism of Eu3+ in the La2LiSbO6:Eu3+ phosphors. Furthermore, the emission intensity could be increased by Gd3+ ions doping and the sample reached the best emission intensity when both dopant contents of Gd3+ and Eu3+ ion concentration were 10 mol%. However, due to the destabilization of the double perovskite structure caused by the doping of Gd3+ ions, the emission intensity of (La0.80Gd0.10Eu0.10)2LiSbO6 (LGLSO: Eu3+) sample was weaker than that of (La0.82Eu0.18)2LiSbO6 (LLSO: Eu3+). Impressively, LGLSO: Eu3+ phosphor exhibited good thermal stability and the luminous intensity at 423 K maintained 84% compared with its initial value at room temperature, which was higher than that of LLSO: Eu3+ (68%). The thermal quenching phenomenon and the enhancement mechanism of thermal stability were analyzed by the configuration coordinate diagram of Eu3+ ion. In addition, both chromaticity coordinates of samples located in red region, demonstrating their potential applications in white LEDs.