Thin film platinum–palladium thermocouples for gas turbine engine applications

• Published in: Thin solid films 2013-07, Vol.539, p.345-349
• Main Authors: Tougas, Ian M., Gregory, Otto J.
• Format: Article
• Language: English
• Subjects: Chemical interdiffusion; diffusion barriers; Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Exact sciences and technology; Gas turbine engine; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Palladium; Physics; Platinum; Radio-frequency sputtering; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thermocouple; Thin film structure and morphology; Transport properties of condensed matter (nonelectronic)
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2013.05.076

Thin film platinum:palladium thermocouples were fabricated on alumina and mullite surfaces using radio frequency sputtering and characterized after high temperature exposure to oxidizing environments. The thermoelectric output, hysteresis, and drift of these sensors were measured at temperatures up to 1100°C. Auger electron spectroscopy was used to follow the extent of oxidation in each thermocouple leg and interdiffusion at the metallurgical junction. Minimal oxidation of the platinum and palladium thermoelements was observed after high temperature exposure, but considerable dewetting and faceting of the films were observed in scanning electron microscopy. An Arrhenius temperature dependence on the drift rate was observed and later attributed to microstructural changes during thermal cycling. The thin film thermocouples, however, did exhibit excellent stability at 1000°C with drift rates comparable to commercial type-K wire thermocouples. Based on these results, platinum:palladium thin film thermocouples have considerable potential for use in the hot sections of gas turbine engines. •Stable thin film platinum:palladium thermocouples for gas turbine engines•Little oxidation but significant microstructural changes from thermal cycling•Minimal hysteresis during repeated thermal cycling•Drift comparable to commercial wire thermocouples