On the photoluminescence of multi-sites Ce3+ in T-phase orthosilicate and energy transfer from Ce3+ to Tb3+

Abstract

Ce3+, Tb3+ co-doped T-phase orthosilicate Ba1.2Ca0.8SiO4 phosphors were prepared by means of solid state reactions. The synthesized samples were investigated using XRD and PL emission and excitation spectra. The emission spectra for Ce3+ doped Ba1.2Ca0.8SiO4 phosphors show broad bands in the 320–550 nm spectral region. The excitation spectra exhibit several absorption peaks in the range of 250–400 nm. Both the emission and excitation spectra are dependent on the excitation or monitoring wavelengths. We attribute these results to Ce3+ ions occupying two different crystallographic sites (i.e., Ce I and Ce II). The Ce3+, Tb3+ co-doped Ba1.2Ca0.8SiO4 phosphors show Tb3+-related line emissions in the 475–600 nm spectral region and Ce3+-related band emissions in the 350–525 nm spectral region when the 4f → 5d transition of Ce3+ is excited (λex = 345 nm), indicating that energy transfer from Ce3+ to Tb3+ takes place. Moreover, the emission intensity of 5D4 → 7F5 transition for Ba1.00Ce0.02Tb0.08Li0.10Ca0.8SiO4 is 30 times stronger than that of Ba1.04Tb0.08Li0.08Ca0.8SiO4 sample under 345-nm UV excitation.