Abstract:

Sr₂MgSi₂O₇: Ce³⁺,Tb³⁺,Eu³⁺ phosphors were prepared by high temperature solid state reaction. Crystallization and optical properties were investigated via powder X-ray diffraction and fluorescence spectra, respectively. Under the excitation of ultraviolet(327 nm), the emission spectra of these phosphors exhibited multi-emission lines peaked at about 387(blue-purple color), 542(green color) and 611 nm(red color). Monitored at 387, 542 and 611 nm, respectively, the Sr₂MgSi₂O₇: Ce³⁺,Tb³⁺,Eu³⁺ powder got optimally excited at λ_ex=327 nm, the Sr₂MgSi₂O₇: Tb³⁺ powder got optimally excited at λ_ex=235 nm. It has been found that the chromaticity coordinates (0.337, 0.313) for the nominal composition Sr_1.91MgSi₂O₇: 0.01Ce³⁺,0.05Tb³⁺,0.03Eu³⁺ is very close to the CIE(Commission International de I'Eclairage 1931 chromaticity) standard white coordinates (0.33, 0.33), showing that Sr_1.91MgSi₂O₇: 0.01Ce³⁺,0.05Tb³⁺,0.03Eu³⁺ is a potential single-phased white phosphor for LED-based UV-chip. The energy transfer processes from Ce³⁺ to Tb³⁺ and from Ce³⁺ to Eu³⁺ were discussed. There may be two kinds of energy transfer process in the Sr₂MgSi₂O₇: Ce³⁺,Tb³⁺,Eu³⁺ system, which is from Ce³⁺(5d) to Eu³⁺(⁵D₄)+Tb³⁺(⁵D_3,4) and Tb³⁺(⁵D_2,3)→Ce³⁺(5d)→Eu³⁺(⁵L₆).

Key words: Sr₂MgSi₂O₇: Ce³⁺, Tb³⁺, Eu³⁺, White phosphor, White light emitting diode, Energy transfer