Strong sensitivity to the presence of gaseous hydrogen of the resistivity of yttrium iron garnet

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Abstract
The electrical resistivity of pure bulk yttrium iron garnet has been found to decrease considerably in presence of gaseus hydrogen, in the temperature range 50≤T≤600 °C. A relative resistivity decrease of about 45%, almost temperature independent, is observed when yttrium iron garnet is exposed to pure hydrogen. Exposing the sample to H2‐N2 gas mixtures, hydrogen relative concentrations as small as 100 ppm are detectable. This phenomenon is interpreted in terms of hydrogen diffusion into the garnet, with simultaneous formation of OH− and Fe2+ centers, the latter causing the resistivity drop. Pure yttrium iron garnet thus appears promising as the basic material for chemical sensors of hydrogen, working at temperatures much higher than conventional semiconductor devices.