Temperature Dependent Luminescence of Yellow‐Emitting α‐Sialon:Eu2+ Oxynitride Phosphors for White Light‐Emitting Diodes

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 val (m/val+) Si 12-(m+n) Al m+n O n N 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, 1≤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+ .

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