Abstract
Glass-ceramics containing Er3+/Yb3+ codoped CaF2 nanocrystals have been prepared by using the controlled crystallization above 650°C of the (Yb3+/Er3+) codoped CaF2–SiO2 xerogels. X-ray diffraction and scanning electron microscopy data have revealed the formation of CaF2 nanocrystals of about 16nm size. For pumping at 973nm, this glass-ceramics shows, besides green and red up-conversion luminescence, violet (at ∼408nm) and near-ultraviolet emission (at ∼380nm). The mechanisms responsible for the upconversion luminescence are presented and discussed. The fluorescence lifetimes of the metastable levels responsible for violet, green and red luminescence are measured and their quantum efficiencies are estimated.
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