Down‐Shifting and Up‐Conversion Spectroscopic Properties of ( Ca , Mg ) 3 ( VO 4 ) 2 : Yb 3+ , Eu 3+ Phosphors

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 :0.12 Eu 3+ , indicating that both lattice expansion and contraction can decrease the site symmetry of Eu 3+ in Ca 3 ( VO 4 ) 2 :0.12 Eu 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, 5 D 1 → 7 F 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 5 D 1 → 7 F 3 transition of Eu 3+ and cross‐relaxation Eu 3+ ( 7 F 3 ) + Eu 3+ ( 5 D 0 ) → Eu 3+ ( 7 F 0 ) + Eu 3+ ( 5 D 1 ), is presumably the leading mechanism of such inconsistency.