Ito Thin Film Resistance Temperature Detector with Al/Al₂O₃ Protective Coating for High-Temperature Application

Thin film resistance temperature detectors (TFRTDs) are ideal for in-situ temperature measurements due to their non-intrusiveness and quick thermal response. Indium tin oxide (ITO) is a promising material for TFRTDs used in harsh environments due to its high melting point and large temperature coefficient of resistance (TCR). However, the performance of ITO TFRTDs at elevated temperatures has attracted little attention and needs further investigation. In this paper, ITO TFRTDs were fabricated on Al₂O₃ substrates by using magnetron sputtering technology. Their key indicators, including TCR, repeatability, and thermal stability, were systematically investigated from room temperature to 1000°C. Results show that ITO TFRTDs possess a large TCR but poor repeatability and thermal stability. Herein, a novel Al/Al₂O₃ heterogeneous protective coating was employed to improve the high-temperature performance of the ITO TFRTDs. By using this method, the repeatability and resistance drift were successfully reduced by an order of magnitude: from 23.3% to 4.2% and from 0.015%/h to 0.0077%/h, respectively. The prior performance of the enhanced ITO TFRTDs makes them attractive for in-situ temperature measurement, especially in harsh environments.