Luminescence of Sr_2MgSi_2O_(7-1.5x)N_x:Eu~(2+) ,Dy~(3+) phosphors with long-afterglow properties for white LEDs

摘要

To develop long-afterglow luminescent materials for white LEDs application, a series of Sr1.97MgSi2O7-1.5xNx:0.01Eu(2+),0.02Dy(3+) (0 = x = 0.49) phosphors were designed. The single-phase samples were confirmed and the introduction of N was verified by the XRD patterns and energy-dispersive X-ray spectrum. The average particle size of the phosphors was determined to be about 4.9 mu m. When the N is doped, it has been found the Eu2+ emission intensity decreases gradually, which could be owing to the increasing crystal defects by the nonequivalent substitution between N and O. The excitation spectra reveal that the broad and strong excitation bands from 240 to 450 nm can well match the LED chip. It is interesting that the incorporation of N can improve the afterglow time, which has been interpreted by the thermoluminescence curves. The investigation of the temperature-dependent luminescence indicates a beneficial effect on the thermal stability by doping N in the phosphors.