Optical Thermometry Based on Up‐Conversion Luminescence Behavior of Er 3+ ‐Doped Transparent Sr 2 YbF 7 Glass‐Ceramics

Transparent novel glass‐ceramics containing Sr 2 YbF 7 :Er 3+ nanocrystals were successfully fabricated by melt‐quenching technique. Their structural and up‐conversion luminescent properties were systemically investigated by XRD , HRTEM , and a series of spectroscopy methods. The temperature‐dependent up‐conversion spectra prove that 2 H 11/2 and 4 S 3/2 levels of Er 3+ are thermally coupled energy levels ( TCEL ). Consequently, the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 emissions of Er 3+ in Sr 2 YbF 7 :Er 3+ glass‐ceramics can be used as optical thermometry based on fluorescence intensity ratio ( FIR ) technique. Combined with low phonon energy and high thermal stability, Er 3+ ions in Sr 2 YbF 7 glass‐ceramics present broad operating temperature range (300–500 K), large energy gap of TCEL (786 cm −1 ) and high theoretical maximum value of relative sensitivity (62.14 × 10 −4  K −1 at 560 K), which suggests that Sr 2 YbF 7 :Er 3+ glass‐ceramics may be excellent candidates for optical temperature sensors.