High-Temperature PdCr Thin-Film Strain Gauge With High Gauge Factor Based on Cavity Structure

In aerospace engine applications, high-temperature thin-film strain gauges play a crucial role in the field of material damage state detection and the assessment of the condition of high-temperature turbine blades for aerospace engines. However, several obstacles still exist toward their broad applications, such as low sensitivity, vulnerability to ambient temperature variations, and inaccuracies due to resistance temperature drift. In this work, we introduce an optimized structural strategy to improve the sensitivity of high-temperature thin-film strain gauges. In simulations, structures with varying sensitive grid and cavity sizes were designed, and optimization resulted in improved strain transfer efficiency on the sensitive grid. Subsequently, the strain gauge was fabricated on an aluminum oxide substrate via micro-electromechanical system (MEMS) technology, and the sputtered PdCr thin film was annealed in different gas atmospheres to evaluate their impact on sensor performance. The results indicate that during annealing in an air environment, PdO and Cr{2}O{3} oxides are formed in advance in PdCr. This will adversely affect the performance of the strain gauge, leading to inaccurate measurement results. Furthermore, the sensor demonstrated excellent stability across a wide range of temperature conditions. At room temperature, both single- and pair-cavity designs exhibited high strain sensitivity, with gauge factors of 1.91 and 1.90, respectively. This work presents a strategy for simultaneously improving sensitivity, paving the way for broader applications of high-temperature thin-film strain gauges.