Analysis of palladium and yttrium-palladium alloy layers used for hydrogen detection with SAW device

Because of its physicochemical properties, hydrogen appears as an efficient source of energy for powering devices. Its abundance on earth and the simplicity of the process needed for its extraction from water make this compound a promising solution for an increasing number of applications (energy production and storage, car industry, space, etc.). However, due to its unstable properties, a particular care must be dedicated to control gaseous leaks close to facilities using this resource. Surface Acoustic Wave (SAW) sensors consisting in Rayleigh-wave delay lines equipped with a sensitive overlay can be efficiently used to detect hydrogen. In this paper, we propose a SAW device exhibiting either pure palladium or palladium-yttrium alloy sensing area for the detection of hydrogen in standard environmental conditions. An X-ray diffraction analysis of these sensitive materials is also presented and correlated with the simultaneously acquired signal of our sensor. Measurements of hydrogen in the 0.5-2% concentration range diluted in nitrogen are presented. The effect of combining yttrium and palladium as sensing layer on the sensor response is reported and its interest for improving our sensor's sensitivity is finally discussed.