Efficient and thermally stable blue-emitting Ce³⁺ doped LaAl(Si_6−zAl_z)(N_10−zO_z) (JEM:Ce) phosphors for white LEDs

Abstract

La₂O₃, LaN, Si₃N₄, AlN and CeO₂ have been used as starting materials to synthesize Ce doped LaAl(Si_6−zAl_z)(N_10−zO_z) (z ≈ 1, termed the JEM phase) phosphors, via a solid-state reaction method in a gas pressure furnace at a high temperature. Nearly single phase JEM:Ce phosphors have been obtained by carefully controlling the synthesis conditions. The 5% Ce doped JEM phosphor displays a broad excitation band extending from UV to 425 nm, with a maximum at 355 nm. Excitation with 355 nm light results in a Ce³⁺ 5d–4f emission band (FWHM = 81 nm) centered at 430 nm, with a high internal quantum efficiency of 75%. The emission of the JEM:0.01Ce phosphor has only quenched 3% at room temperature as compared to the intensity at 4 K and still 57% of the luminescence is left at 573 K, which is superior to JEM:Eu phosphors. These performances make JEM:Ce phosphors very promising blue-emitting phosphors for white LED applications.