Proton conduction of BaCe0.90Y0.10O3 -δ thin film with lattice distortion

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• We have realized the high proton conduction of BaCe0.9Y0.1O3-δ thin film.

The proton conduction of BaCe0.9Y0.1O3 -δ (BCY) film on Al2O3 (0001) substrate grown by RF magnetron sputtering has been studied as a function of film thickness (20–600 nm) in the temperature region of 300–700 °C. The lattice constants and grain size of the as-deposited film increase with increasing film thickness. The film thickness above ~ 200 nm, which close to the lattice constants of the bulk, shows high proton conductivity with small activation energy (EA) of ~ 0.3 eV below 500 °C. The BCY thin film has the mixed valent states of Ce4 + and Ce3 + created by the charge transfer from O 2p to Ce 4f states. The EA corresponds to the energy difference between the top of valence band and the Fermi level. These results originate to the changes of O–O bond length and oxygen vacancies in the a–c plane of the BCY thin film.