Valence transfer of Eu3+ activated in Yb2Si2O7 phosphors: Luminescence and self reduction.

Generally, the reduction of Eu 3+ to Eu 2+ in solids requires annealing in a reducing atmosphere. In this work, we find that the reduction of Eu 3+ to Eu 2+ can be realized in Yb 2 Si 2 O 7 phosphors after being soaked in boiling water. Eu 3+ -activated Yb 2 Si 2 O 7 with different doping concentrations was synthesized by a sol-gel method. The as-prepared Yb 2 Si 2 O 7 :Eu 3+ phosphors showed strong red emission at 612 nm under ultraviolet light, corresponding to the 5 D 0 → 7 F 2 transition of Eu 3+ . The optimized doping concentration of Eu 3+ was 7 mol% with the highest emission intensity at 612 nm. The valence change and luminescence properties of Eu-doped Yb 2 Si 2 O 7 phosphors after being soaked in boiling water are reported and the reduction mechanism from Eu 3+ to Eu 2+ in the compounds is discussed. Our findings suggest that this kind of Eu 3+ → Eu 2+ valence transfer might shed light on the development of phosphors for display applications. [ABSTRACT FROM AUTHOR]