Structure and Conductivity of Epitaxial Thin Films of In-Doped BaZrO3-Based Proton Conductors

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• 作者：Laura Mazzei ; Max Wolff ; Daniele Pergolesi ; Joseph A. Dura ; Lars Börjesson ; Philipp Gutfreund ; Marco Bettinelli ; Thomas Lippert ; Maths Karlsson
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 22, 2016
• 年：2016
• 卷：120
• 期：50
• 页码：28415-28422
• 全文大小：391K
• ISSN：1932-7455

文摘

Epitaxial thin films of the proton-conducting perovskite BaZr_0.53In_0.47O_3−δH_0.47–2δ, grown by pulsed laser deposition, were investigated in their hydrated and dehydrated conditions through a multitechnique approach with the aim to study the structure and proton concentration depth profile and their relationship to proton conductivity. The techniques used were X-ray diffraction, X-ray and neutron reflectivity, nuclear reaction analysis, and Rutherford backscattering, together with impedance spectroscopy. The obtained proton conductivity and activation energy are comparable to literature values for the bulk conductivity of similar materials, thus showing that grain-boundary conductivity is negligible due to the high crystallinity of the film. The results reveal an uneven proton concentration depth profile, with the presence of a 3–4 nm thick, proton-rich layer with altered composition, likely characterized by cationic deficiency. While this surface layer either retains or reobtains protons after desorption and cooling to room temperature, the bulk of the film absorbs and desorbs protons in the expected manner. It is suggested that the protons in the near-surface, proton-rich region are located in proton sites characterized by relatively strong O–H bonds due to weak hydrogen-bond interactions to neighboring oxygen atoms and that the mobility of protons in these sites is generally lower than in proton sites associated with stronger hydrogen bonds. It follows that strongly hydrogen-bonding configurations are important for high proton mobility.