Enhancing sensitivity and detection range of Ca2GdZr2Al3O12:Bi3+,Tb3+ fluorescent thermometer via multi-excitation pathways and anti-thermal quenching.

Developing fluorescence intensity ratio (FIR) thermometers with low cost, high sensitivity and wide measurement range is a key bottleneck in this field, which poses severe challenges to conventional thermosensitive materials. Herein, a series of Ca2GdZr2Al3O12:Bi3+,Tb3+ phosphors with multi-excitation pathways were fabricated, and anti-thermal quenching (ATQ) behavior was attributed to the synergistic effect of electron-phonon coupling and crystal field, boosting the sensitivity and temperature detection range of fluorescent thermometers. Among them, under the excitation pathway where both Bi3+ and Tb3+ ions exhibit typical TQ behaviors, the FIR309 thermometer achieves a maximum Sr309 value of 1.46% K-1 (at 353 K), thereby exhibiting excellent temperature sensing performance in the range of 293-433 K. In contrast, for the excitation pathway where the ATQ behavior of Tb3+ ions is realized via the synergistic effect of electron-phonon coupling and crystal field, the Sr322 value of the FIR322 optical thermometer increases to 2.05% K-1, and shifts the high-sensitivity detection range to 413-573 K. Notably, the combined temperature detection range (293-573 K) of the FIR309 and FIR322 thermometers is two times that of the single FIR309 thermometer. Moreover, the multi-pathway FIR optical thermometer exhibits outstanding temperature measurement performance on the optical fiber temperature detection platform. These promising findings offers a new perspective for developing optical thermometer with exceptional performance.