Structure and optical properties of transparent Er3+-doped CaF2–silica glass ceramic prepared by controllable sol–gel method

Transparent Er 3+ -doped CaF 2 –silica glass ceramics were prepared by the direct physical introduction of Er 3+ doped CaF 2 nanocrystals into acid-catalyzed sol–gel silica glass . The physical methods of ball milling , ultrasonic baths, and stirring were investigated to disperse Er 3+ doped CaF 2 nanocrystals in the silica sols. The CaF 2 –silica sol mixture went through gelation and heat-treatment to form Er 3+ -doped CaF 2 –silica glass ceramics. The morphology of Er 3+ doped CaF 2 in silica glass did not change after heat-treatment at 600   °C for 10   h. The experimental results showed that Er 3+ doped CaF 2 in the glass ceramic prepared with the assistance of ball milling possesses the best dispersity and homogeneity. The highest in-line transmittance of the glass ceramic reached up to 85% in visible region. Glass ceramic exhibits efficient up-conversion emissions corresponding to the Er 3+ : 4 F 9/2 → 4 I 15/2 transition and long lifetime of 4 F 9/2 level (1.73   ms) under 980   nm excitation.