Structure and color-tunable luminescence properties of Ce{sup 3+} and Tb{sup 3+}-activated Mg{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2} phosphors based on energy transfer behavior
A series of novel luminescent emission-tunable phosphors Mg{sub 2}La{sub 8}(SiO{sub 4}){sub 6}O{sub 2}:Ce{sup 3+},Tb{sup 3+} (MLS:Ce{sup 3+},Tb{sup 3+}) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce{sup 3+},Tb{sup 3+} phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce{sup 3+} to Tb{sup 3+} ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb{sup 3+} ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'éclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce{sup 3+}/Tb{sup 3+}.