Down-Shifting and Up-Conversion Spectroscopic Properties of (Ca,Mg)3(VO4)2:Yb3+,Eu3+ Phosphors

We found that substitution of not only a larger ion like Ba2+ [J. Am. Ceram. Soc., 93, 138 (2010)] but also a smaller one like Mg2+ (this paper) replacing no > 14.9% Ca2+ ions could enhance integrated down-shifting (DS) emission intensity of red phosphor Ca-3(VO4)(2):0.12Eu(3+), indicating that both lattice expansion and contraction can decrease the site symmetry of Eu3+ in Ca-3(VO4)(2):0.12Eu(3+) phosphor. This finding is anticipated to improve the Eu3+ emission intensity of other Eu3+-doped phosphors. To further investigate Eu3+ up-conversion (UC) behaviors, Yb3+ ion was used as a sensitizer. Interestingly, D-5(1) -> F-7(3,4,6) transitions of Eu3+, which were barely detectable under DS excitation, exhibited strong intensity under UC excitation. A "recycling" process, arising from the D-5(1) -> F-7(3) transition of Eu3+ and cross-relaxation Eu3+ (F-7(3)) + Eu3+ (D-5(0)) -> Eu3+ (F-7(0)) + Eu3+ (D-5(1)), is presumably the leading mechanism of such inconsistency.