Blue-Emitting Li2Sr1−3x/2CexSiO4 Phosphors for Ultraviolet White Light-Emitting Diodes
Abstract:A potential ultraviolet light-emitting diode (UV-LED) blue phosphor, Li2Sr1−3x/2CexSiO4, was synthesized by firing at 900°C for 4 h in a reducing atmosphere of N2/H2 (5%). The crystal structure and photoluminescence properties of Li2Sr1−3x/2CexSiO4 were reported. On the basis of the Rietveld refinement of X-ray powder diffraction measurement, the synthesized phosphor is nearly a single-phase material in the trigonal system with the space group P3121 (No. 152) and Z=3. It is confirmed that Ce3+ occupies the Sr2+ site, which is located in the channels formed by two [SiO4] and three [LiO4] tetrahedral with eight coordination. The Li2Sr1−3x/2CexSiO4 could be efficiently excited by UV light and yielded a blue emission band centered at 442 nm, originating from the 4f 05d1→4f 1 of Ce3+. The concentration quenching occurs at x=0.03 and no shift in emission band is observed with the increase of x value. Upon the 358 nm excitation, the absorption, internal, and external quantum efficiencies are 81%, 81%, and 65.9%, respectively. Furthermore, the sample shows high thermal stability, the luminescence intensity of which, measured at 150°C, maintains about 92% of that at room temperature.
Document Type: Research Article
Affiliations: 1: Nitride Particle Group, Nano Ceramics Center, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan 2: College of Materials Science and Engineering, Nanjing University of Technology, Nanjing, Jiangsu 210009, China 3: Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), School of Materials and Metallurgy, Northeastern University, Shenyang, Liaoning 110004, China
Publication date: July 1, 2010