Optical Properties of Blue-Emitting Ce[sub x]Si[sub 6−z]Al[sub z−x]O[sub z+1.5x]N[sub 8−z−x] for White Light-Emitting Diodes

Abstract

In this work, blue-emitting CexSi6−zAlz−xnormalOz+1.5xnormalN8−z−x (0.3≤z≤2.5,0.5≤x≤2.5) phosphors were synthesized by firing powder mixtures of α-Si3normalN4 , AlN, Al2normalO3 , and CeO2 at 1950°C for 2 h under 1.0 MPa normalN2 . The resultant phosphors were characterized by phase identification, diffuse reflectance spectra, photoluminescence spectra, quantum efficiency, and temperature-dependent luminescence. The samples showed high purity at the overall range of the varied x and z values. A single broad emission band centered at about 486 nm at 410 nm excitation was observed. Moreover, the CexSi6−zAlz−xnormalOz+1.5xnormalN8−z−x phosphors showed high thermal stability, which could sustain 79–88% emission intensity measured at room temperature. These results indicate that the CexSi6−zAlz−xnormalOz+1.5xnormalN8−z−x phosphors are promising wavelength-conversion materials for white light emitting diodes (LEDs) using near-UV LED chips as the primary light source.

Luminescent properties of Eu2+ and Ce3+ ions in strontium litho-silicate Li2SrSiO4

“…This can be assigned to the differences in the coordination polyhedra of the Ce 3 + ions in these compounds. Also note that the found value of E cfs (20,200 cm À 1 ) essentially differs from that (E cfs ¼11,400 cm -1 ) reported for Ce 3 + ions in Li 2 SrSiO 4 by Liu et al [13]. The most probable explanation is that Liu et al [13] have used a lamp source with a very low output at wavelengths shorter than 240 nm, so that the excitation bands at 209 and 218 nm were not recorded in their experiments.…”

“…This differs from that (d¼2400 cm À 1 ) found in the present work. This discrepancy can be explained by the existence of several kinds of cerium centers in the sample studied by Liu et al [13]. As seen from Fig.…”

“…Recently, Liu at al. [13] have reported the value of 5300 cm À 1 as the Stokes shift of the emission of Li 2 Sr 1 À x Ce x SiO 4 (x¼0.045). This differs from that (d¼2400 cm À 1 ) found in the present work.…”

“…Based on the results of XANES study, these authors came to conclusion that the introduction of Ce 3 + ions in Li 2 SrSiO 4 causes the stabilization of Li-vacancies, and thus suppresses the oxidation of Eu 2 + ions. Also note that Ce 3 + -doped Li 2 SrSiO 4 has been recently presented as a potential blue phosphor for solid-state lighting [13].…”

Inorganic Phosphor Materials for Lighting

“…Liu et al [106] have reported on the phosphor Li 2 Sr 1-3x/2 Ce x SiO 4 (x = 0.0025-0.07). The material was prepared by high temperature solid state synthesis as a single phase and it was found that Ce 3?…”