SAW sensor exploiting palladium layer properties for selective detection of hydrogen

For an increasing number of application (energy production, car industry, space, etc.), hydrogen appears as a solution of the future as it is the most common body in the Universe (and therefore on Earth). However, due to its unstable properties, a particular care must be dedicated to control possible gaseous leaks close to facilities using this resource. Here we propose surface acoustic wave sensors for detecting gaseous hydrogen in standard environmental conditions (atmospheric pressure and room temperature). The proposed SAW sensors consists in two Rayleigh-wave delay lines built on Quartz. One equipped with a Palladium overlay and the other exhibiting a free path between the two interdigitated transducers. A dedicated hermetical gas test cell has been developed to test the efficiency of the sensor when exposed to hydrogen-composed atmospheres. A particular care was paid to avoid hydrogen leakage in the working environment and to perform the regeneration of the gas absorbing layer. The developed SAW devices exploiting hydrogen absorption capabilities of palladium layers exhibiting different thicknesses have been here used to make the detection and the identification of hydrogen concentrations (in the 0.25-2% range) diluted in nitrogen and is also able to make detection in current atmosphere. The effect of the palladium thickness variations along with the influence of an Yttrium doping of the palladium layer on the sensor behavior will be studied here.