Upconversion Luminescence Properties of NaYF4 Nanocrystals Precipitated Nd3+/Nb3+/Ho3+ Tri-Doped Oxyfluoride Glass Ceramics.

Transparent oxyflouride glass ceramics composed of SiO2-Al2O3-Na2O-NaF-YF3 tri-coped with Nd3+/Yb3+/Ho3+ were prepared by thermal treatment. Segregation of NaYF4 nanocrystals in the matrix was confirmed from structural analysis by means of X-ray diffraction and transmission electron microscopy. Compared with glass samples, very strong green upconversion (UC) luminescence due to the Ho3+: (4F5, 5S2) --> 51(8) transition was observed in the glass ceramics under 808 nm excitation. It was found that upconversion intensity of Ho3+ strongly depends on the Nd3+ concentration, and the energy transfer process from Nd3+ to Ho3+ via Yb3+ was proposed.