Fabrication and Efficient Infrared‐to‐Visible Upconversion in Transparent Glass Ceramics of Er–Yb Co‐Doped CaF2 Nano‐Crystals

Abstract

Transparent glass ceramics containing CaF2 nano‐crystals co‐doped with Er–Yb were developed by heat treatment of glasses in the system SiO2–Al2O3–CaF2–LnF3 (Ln=Er, Yb). The crystal size of CaF2 increased with increasing heat‐treatment temperature. Upconversion emission intensities at 660 and 540 nm increased dramatically with increasing heat‐treatment temperature. The cathode luminescence mapping indicates that the visible Er‐luminescence arises mainly from the precipitated CaF2 nano‐crystals with a phonon energy lower than that of a silicate matrix. It is concluded that both Er and Yb were concentrated in the CaF2 nano‐crystals, and the quantum efficiency of Er3+‐luminescence and the energy transfer efficiency from Yb3+ were considerably improved after ceramization.