A Single Phase LaAl(Si6-zAlz)(N10-zOz):Eu2+ Phosphor with Large Red-Shift of the Emission and Anomalous Decay Behavior

Phosphor-converted light-emitting diodes (pc-LEDs) have penetrated to solid-state lighting over the last decades because of high energy conversion efficiency, long lifetime and environmental benefits. White pc-LEDs with high luminous efficacy and color rendition are urgently required, especially for illumination-grade light sources. Ce doped LaAl(Si 6-z Al z )(N 10-z O z ) (termed JEM) phosphor has been reported as a promising phosphor for white LEDs using near UV excitation, particularly for home illumination. 1 However, the unavailability of a phase pure JEM:Ce phosphor prevents widespread application and detailed crystal structure analysis. In addition, Eu 2+ and Ce 3+ are the most effective activators for white LED phosphors, but there is no report on the photoluminescence properties of an Eu 2+ doped JEM phosphor. In the present study, a phase pure Eu 2+ doped JEM phosphor and non-doped JEM were successfully obtained with a solid-state reaction method by carefully controlling the synthesis temperature and chemical composition of starting materials. The Eu 2+ doped JEM phosphors show a very interesting red-shift of the emission band; the emission color after excitation with 355 nm light can be tuned from blue-green to yellow by increasing the Eu concentration. Furthermore, an anomalous decay behavior with bi-exponential decay was observed, although there is only one crystallographic site in the JEM structure. 2 With the single phase JEM sample achieved, we investigated the details of the crystal structure by XRD and magic-angle spinning (MAS) solid state nuclear magnetic resonance (NMR). Reference 1. K. Takahashi, N. Hirosaki, R.-J. Xie, M. Harada, K. Yoshimura and Y. Tomomura, Appl. Phys. Lett. 91, 091923 (2007). 2. J. Grins, Z. Shen, M. Nygren and T. Ekström, J. Mater. Chem. 5, 2001 (1995). Fig1. A scheme of the large red-shift emission (a) and anomalous decay behavior (b) for JEM:Eu 2+ phosphor and JEM crystal structure (c). Figure 1