Antioxidation and High-Resolution Ultrasonic Temperature Sensor Based on Cr³⁺:MgAl₂O₄ Single Crystal Fiber

Abstract

High-quality pure MgAl 2 O 4 and Cr 3+ :MgAl 2 O 4 crystal fibers were grown using laser heating pedestal growth method successfully. The antioxidation ultrasonic temperature sensors (UTSs) were designed using MgAl 2 O 4 single crystal fibers (SCFs) as the acoustic waveguide for the first time. The ultrasonic velocity and the unit sensitivity were investigated, which illustrate that the MgAl 2 O 4 SCF-UTS is more sensitive compared with the YAG SCF-UTS because of the order−disorder phase transition of the spinel. Furthermore, due to the lattice distortion induced by doping ions, the unit sensitivity was further optimized by 18% when using Cr 3+ :MgAl 2 O 4 crystal fiber as the probe, and the achieved unit sensitivity of 43.94 ns•C 1− •m −1 is the record for SCF-UTS. This work represents a feasible approach for high-resolution temperature sensing through the ultrasonic technique and crystal design and optimization.

Design and Directional Growth of (Mg1−xZnx)(Al1−yCry)2O4 Single‐Crystal Fibers for High‐Sensitivity and High‐Temperature Sensing Based on Lattice Doping Engineering and Acoustic Anisotropy

“…[19] The maximum unit sensitivity of the Cr 3+ :MgAl 2 O 4 SCF-UTS was measured to be 43.94 ns C −1 m −1 , corresponding to a maximum resolution of 1.51 °C, representing record performance for SCF-UTS at that time. [20] Previous studies have found that a lower ultrasonic velocity and larger temperature-dependent velocity variation lead to higher sensor sensitivity. [20][21] The ultrasonic velocity of the crystal fibers is anisotropic and is mainly determined by the elastic properties and crystal density.…”

“…[20] Previous studies have found that a lower ultrasonic velocity and larger temperature-dependent velocity variation lead to higher sensor sensitivity. [20][21] The ultrasonic velocity of the crystal fibers is anisotropic and is mainly determined by the elastic properties and crystal density. Therefore, orientation optimization and doping modification are feasible approaches for regulating the ultrasonic velocity, thereby improving the sensor performance.…”