Thermoelectric characteristics of silicon carbide and tungsten-rhenium-based thin-film thermocouples sensor with protective coating layer by RF magnetron sputtering

Abstract

A thin-film thermocouples (TFTCs) sensor based on silicon carbide substrate, 95 wt% tungsten-5 wt% rhenium (W-5Re) and 74 wt% tungsten-26 wt% rhenium (W-26Re) thermosensitive part with aluminum oxide protective coating layer was designed and fabricated by radio frequency (RF) magnetron sputtering. It exhibited a high thermoelectric voltage of 35.51 mV when the temperature difference was 1240 °C (the hot junction temperature was 1420 °C), with an average Seebeck coefficient of 28.63 μV/°C, which was 27% larger than the standard C-type thermocouple wires at the same temperature difference. The repeatability error was ±4.1%, the drift rate was 9.6 °C/h for 10 h and the laser response time was 0.36 ms. Compared to the traditional thermocouple, it could provide long-term temperature testing within 1420 °C for the requirement of high-temperature measurement and high response speed.