Up-conversion luminescence properties and energy transfer of Er~(3+)/Yb~(3+)co-doped oxyfluoride glass ceramic containing CaF_2 nano-crystals

The Er3+/Yb3+co-doped transparent oxyfluoride glass-ceramics containing CaF2nano-crystals were successfully prepared. After heat treatments, transmission electron microscopy(TEM) images showed that CaF2nano-crystals of 20–30 nm in diameter precipitated uniformly in the glass matrix. Comparing with the host glass, high efficiency upconversion luminescence of Er3+at 540 nm and 658 nm was observed in the glass ceramics under the excitation of 980 nm. Moreover,the size of the precipitated nano-crystals can be controlled by heat-treatment temperature and time. With the increase of the nano-crystal size, the intensity of the red emission increased more rapidly than that of the green emission. The energy transfer process of Er3+and Yb3+was convinced and the possible mechanism of Er3+up-conversion was discussed.