Pressure/composition isotherms of proton conducting SrYb_0.05Zr_0.95O_2.975/H₂O by means of nuclear resonance reaction analysis

Films of SrYb0.05Zr0.095O2.975 were prepared by sol-gel processing. Water vapour pressure/hydrogen composition isotherms were recorded ex-situ comprising
pressures between 0 and 84.5 kPa and temperatures between 873 and 1073 K. Nuclear Resonance Reaction Analysis (NRRA) was used to determine the
hydrogen concentration and, in addition, depth profiles of hydrogen concentration. The chemical potential of interstitial hydrogen in oxides could be determined; from
its temperature dependence thermodynamical constants were calculated. We observe two hydrogen fractions with a site energy difference of 20 kJ/mol. A size effect
of the thermodynamic properties is observed below a thickness of 350 nm: nanofilms exhibit higher solubility than bulk material.