Dissociative water vapour absorption in BaZr_0.85Y_0.15O_2.925/H₂O: pressure-compositions isotherms in terms of Fermi-Dirac statistics

Thin films of proton-conducting BaZr_0.85Y_0.15O_2.925 perovskite-type ceramics, prepared in a sol-gel process by multiple dip-coating on silicon single crystal wafers, and powder samples, prepared by the conventional carbonate route, were charged with hydrogen by dissociative water absorption at definite values of water vapour pressures and temperatures. The absolute content of the absorbed hydrogen was determined ex situ at room temperature using the ¹⁵N nuclear resonance reaction analysis. From the resulting water vapour pressure-hydrogen composition isotherms the absorption enthalpies and entropy were caculated, using our two site model, based on Fermi-Dirac statistics.