Down-Shifting and Up-Conversion Spectroscopic Properties of (Ca,Mg)_3(VO_4)_2:Yb~(3+),Eu~(3+) Phosphors

摘要

We found that substitution of not only a larger ion like Ba~(2+) [J. Am. Ceram. Soc, 93, 138 (2010)] but also a smaller one like Mg~(2+) (this paper) replacing no >14.9% Ca~(2+) ions could enhance integrated down-shifting (DS) emission intensity of red phosphor Ca_3(VO_4)_2:0.12Eu~(3+), indicating that both lattice expansion and contraction can decrease the site symmetry of Eu~(3+) in Ca_3(VO_4)_2:0.12Eu~(3+) phosphor. This finding is anticipated to improve the Eu~(3+) emission intensity of other Eu~(3+)-doped phosphors. To further investigate Eu~(3+) up-conversion (UC) behaviors, Yb~(3+) ion was used as a sensitizer. Interestingly, ~5D_1 → ~7F_(3,4,6) transitions of Eu~(3+), which were barely detectable under DS excitation, exhibited strong intensity under UC excitation. A "recycling" process, arising from the ~5D_1 → ~7F_3 transition of Eu~(3+) and cross-relaxation Eu~(3+) (~7F_3) + Eu~(3+) (~5D_0) → Eu~(3+) (~7F_0) + Eu~(3+) (~5D_1), is presumably the leading mechanism of such inconsistency.