In Situ Synthesis of β-Na(1).(5)Y(1).(5)F(6): Er(3+) Crystals in Oxyfluoride Silicate Glass for Temperature Sensors and Their Spectral Conversion and Optical Thermometry Analysis

Transparent oxyfluoride glass-ceramics (GCs) with embedded β-Na(1).(5)Y(1).(5)F(6) crystals doped with Er(3+) ions were fabricated by a melt-quenching method with subsequent heat-treatment. The structural characterizations and spectroscopic techniques were performed to verify the precipitation of β-Na(1).(5)Y(1).(5)F(6) crystals and partition of the Er(3+) dopant into the crystals. Bright green up-conversion (UC) emission was achieved in Er(3+)-doped glass-ceramic (Er-GC). Furthermore, the temperature-dependent visible UC behavior based on thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs) was also examined in the temperature range 298 k to 823 K with maximum relative sensitivity (S(r)) of 1.1% K(−1) at 298 K for TCLs in Er-G and Er-GC samples.