Sandwich probe temperature sensor based on In₂O₃-IZO thin film for ultra-high temperatures

Abstract

High-temperature thin-film thermocouples (TFTCs) have garnered significant attention in aerospace and steel metallurgy industries. However, previous studies on TFTCs have primarily focused on the two-dimensional planar type, whose thermal sensitive area has to be perpendicular to the test environment, and therefore affects the thermal fluids pattern or loses the accuracy. In order to address this problem, recent studies have developed the three-dimensional probe-type TFTCs, which can be set parallelly to the test environment. Nevertheless, the probe-type TFTCs are limited by their measurement threshold and poor stability at high-temperature. To address these issues, in this study, we propose a novel probe-type TFTCs temperature sensor with a sandwich structure. The sensitive layer is compounded with indium oxide (In2O3) doped zinc oxide (ZnO) and fabricated using screen-printing technology. With the protection of sandwich structure on electrode film, the sensor demonstrates robust high-temperature stability, enabling continuous working at 1200 °C above 5 hours with a low drift rate of 2.3 °C/h. This sensor exhibits a high repeatability of 99.3% when measures the low to high temperatures, which is beyond the most existing probe-type TFTCs reported in the literature. With its excellent high-temperature performance, this temperature sensor holds immense potential for enhancing equipment safety in the aerospace engineering and ensuring product quality in steel metallurgy industries.