Development and Application of Rare Earth-Doped Fluorescent Thermometry Materials
Traditional thermocouples and infrared thermometers, while widely deployed, exhibit fundamental limitations in temperature range, accuracy, and environmental stability. Rare earth-doped fluorescent materials offer a non-contact alternative by exploiting temperature-dependent optical properties such as fluorescence intensity ratio (FIR) and lifetime. This review systematically analyzes the measurement principles, operational ranges, and application domains of fluorescent thermometry materials. Key material systems including Er3+/Yb3+ co-doped fluorides, oxides, and oxyfluorides are evaluated for their performance in biomedical and aerospace contexts. The review identifies selection rules for rare earth dopants and host matrices, with emphasis on FIR thermometry in visible and near-infrared regions. Critical parameters such as absolute sensitivity, relative sensitivity, and temperature resolution are compared across material platforms. The analysis reveals that core-shell structures and multi-ion co-doping strategies significantly enhance thermal sensitivity and photostability. For biomedical applications, the biological windows (1000–1700 nm) enable deep-tissue penetration, while for thermal barrier coatings, thermographic phosphors provide non-destructive turbine blade temperature mapping. The review concludes with recommendations for future development, including the need for standardized calibration protocols and scalable synthesis routes for industrial adoption.