Effect of heat treatment on thermoelectric properties of tungsten-rhenium thin-film thermocouples by RF magnetron sputtering

Tungsten-rhenium thin-film thermocouples (TFTCs) are designed by finite element analysis (FEA) and fabricated based on radio frequency (RF) magnetron sputtering technology to meet the requirement of high temperature measurement in narrow space. The changes with thickness and thermoelectric property (including Seebeck coefficient, repeatability error) of TFTCs are investigated under different heat treatment time and temperature by the result of morphology observation and heat recycling experiment analysis to optimize heat treatment process parameters. The repeatability error of tungsten-rhenium TFTCs with heat treatment at 300 °C for 6 hours can reach to ±1.028%. The electromotive force behavior (EMF) experiments shows the average Seebeck coefficient of heat treated tungsten-rhenium TFTCs reach to 18.92 µV/°C when the temperature difference is 1165 °C (hot junction temperature is 1327 °C) in inert gases protection environment. The thermoelectric service properties of tungsten-rhenium TFTCs sensor have been improved to be a viable replacement candidate for high temperature measurement in narrow space through this technology.