Rational composition design of sesquioxide (Y,Sc,Lu)2O3 single-crystal fibers for robust and high-sensitivity ultrasonic temperature sensor beyond 2100 °C

Abstract

Extreme-environment temperature sensing above 2000°C represents a critical technological challenge for next-generation nuclear reactors, hypersonic propulsion systems, and deep-earth energy extraction. This study pioneers the development of novel mixed sesquioxide (YxSc1-x)2O3 single-crystal fibers (SCF) with ultra-high melting point via micro-pulling down method (μ-PD), establishing an innovative acoustic waveguide platform for ultrasonic temperature sensors (UTS). The lattice component variations exhibit remarkable influence on the acoustic properties as well as the temperature sensing performance. The Y3+-rich (Y0.6Sc0.4)2O3 SCF features a lower elastic modulus and higher density compared to the (YxSc1-x)2O3 with lower Y3+ concentration, which leads to a decreased acoustic velocity and a greater velocity variation, dramatically increasing the thermometry sensitivity. Subsequent investigations reveal that Lu³⁺ doping in (Y0.6Sc0.4)2O3 SCF amplifies lattice disorder, yielding superior acoustic characteristics and enhanced unit sensitivity. Specifically, the optimized 10% Lu3+:(Y0.6Sc0.4)2O3 SCF-UTS demonstrates exceptional temperature sensing capabilities in the range of 25−2100 °C with a maximum unit sensitivity of 108.67 ns⋅°C −1⋅m−1 achieved at 2100 °C, representing the highest working temperature among the contact fiber sensors and the highest unit sensitivity of the crystal-based UTS to date. This work proposes a feasible strategy to improve ultrasonic thermometry performance through rational component design, providing promising candidates for high-temperature sensing towards extreme environments.