Stability Enhancement of the Platinum Thin-Film Temperature Detector up to 1400 °C by Printing Al₂O₃ Protective Layer

Platinum (Pt) resistance temperature detectors (RTDs) are extensively employed as thin film temperature sensors. However, agglomeration of Pt thin films occurs above 800°C due to grain boundary grooving on the free surface, ultimately limiting its application at high temperatures. In this work, a Pt RTD was prepared by depositing multilayer Al ₂ O ₃ protective layer on Pt thin films using electrodynamic jet printing (EJP) technology. The surface morphology and energy dispersive spectroscopy spectrum of Pt thin films indicated that the voids on the surface are reduced, the grains growth are inhibited, the movement and grooving of grain boundaries are limited. The test results indicate that the Pt RTD has not failed after 6 cycles of repeated warming and cooling from 800°C to 1300°C. After repeated cycles, the initial resistance of the Pt RTD with a rate of change of less than 0.5%. In addition, the maximum relative deviation of the resistance in a single cycle is less than 1.6%. The Pt RTD with an 18-layer Al ₂ O ₃ protective layers has undergone 12 cycles without failure, indicating a cycle life exceeding 10 h. Pt RTDs are stable over the range of 25°C to 1400°C with correlation coefficients R ² greater than 0.999, showing good linear correlation. It can withstand temperatures up to 1440°C when printed with 18 protective layers. Compared to a Pt RTD without protective layers, the operating temperature is increased by 40%. This advancement provides a viable solution for the high-temperature monitoring of hot end components in aerospace applications.