Highly sensitive optical thermometry based on Tm3+/Yb3+ doped NaGd2F7 glass ceramics

Abstract

Developing transparent glass ceramics (GC) with high stability and good repeatability for reliable and accurate optical fiber temperature sensing is significant. In this study, a sequence of transparent Tm3+/Yb3+ doped oxyfluoride NaGd2F7 GC were successfully produced through self-crystallization. By precisely controlling the heat treatment time and temperature, the obtained NaGd2F7 nanocrystals (NCs) were evenly dispersed in glass host with particle size in tens of nanometers. The enhanced up-conversion intensity, noticeable Stark splitting and prolonged lifetime of Tm3+ emission manifest better crystallization of NaGd2F7 GC by heat treatment. More importantly, optical temperature performance of NaGd2F7 GC based on the splits of thermally coupled energy level was explored through fluorescence intensity ratio. The maximum relative sensitivity for 3F2 → 3H6 (679 nm) and 1G4 → 3F4 (644 nm) attains 3.33% K−1 at 313 K. Moreover, temperature resolution of GC20 is 0.03 K at 573 K and repeatability is high up to 99.5%. Our investigations above demonstrate that NaGd2F7 GC with high sensitivity, superior precision and stability are potential materials in the field of temperature measurement.