Temperature Dependent Luminescence of Yellow-Emitting α-Sialon:Eu~(2+) Oxynitride Phosphors for White Light-Emitting Diodes

摘要

Yellow-emitting α-sialon:Eu~(2+)phosphors have been reported as interesting down-conversion luminescent materials in white LEDs. In this work, the thermal quenching of α-sialon: Eu~(2+)with the compositions of M_((m/val+))~(val+)Si_(12-(m+n))Al_(m+n)O_nN_(16-n) (M = Ca, Mg, Lu) is studied by investigating the effects of chemical composition, activator concentration, and substitution cation on the temperature-dependent luminescence. The chemical composition of α-sialon:Eu~(2+)was varied in a wide range (0.5≤m≤2.0, l≤n≤1.8). It shows that the m value significantly affects the thermal quenching of α-sialon, whereas the n value hardly does. This difference is ascribed to the obvious lattice expansion and the increase of absolute activator concentration as m increases. The thermal quenching increases with increasing the Eu~(2+)concentration, which is due to enhanced Stokes shift. The type of substitution cation also has an influence on thermal quenching. Among the substitution cations in this work, Lu-α-sialon:Eu~(2+)exhibits largest thermal quenching. Photoionization is considered as the mechanism for the thermal quenching of Lu-α-sialon: Eu~(2+).