Abstract
The proton local coordination environments and vibrational dynamics associated with the two order of magnitude change in proton conductivity in hydrated forms of hexagonal and cubic structured BaTi...
Highlights
IntroductionAcceptor-doped perovskites, based on barium zirconate, BaZrO3, and barium cerate, BaCeO3, are currently the most studied electrolyte candidates, due to good thermal and chemical stability in addition to high proton conductivity.[11−17] Materials based on titanates, such as acceptor-doped BaTiO3,21−26 and Ti-doped Ba2In2O5,18−20 are less well-studied, yet show great promise
Proton-conducting oxides find uses in many energy-related applications, including membranes for steam methane reforming,[1,2] steam electrolysis,[3,4] and hydrogen separation,[5] or as electrolyte materials in a solid-state proton-conducting fuel cell (PCFC).[6−15] The development of the PCFC technology depends on the discovery of novel materials with high proton conduction in the intermediate temperature regime, T = 200−600 °C
The asymmetry of the band toward lower energy may indicate the presence of a distinct second population of proton sites, or it may be an effect of the increased IR cross-section of the increasingly polarized O−H unit when its hydrogen bond is strengthened
Summary
Acceptor-doped perovskites, based on barium zirconate, BaZrO3, and barium cerate, BaCeO3, are currently the most studied electrolyte candidates, due to good thermal and chemical stability in addition to high proton conductivity.[11−17] Materials based on titanates, such as acceptor-doped BaTiO3,21−26 and Ti-doped Ba2In2O5,18−20 are less well-studied, yet show great promise. Of particular interest to this work is the solid solution of scandium doping into barium titanate,[25] BaTi1−xScxO3−x (BTSX where X is the scandium doping x expressed as a percentage from 0−100), assuming ideal substitution of Sc3+ for Ti4+. The BTSX solid solution (0 < X < 70) exhibits a structural phase transition from a 6H hexagonal perovskite to a cubic perovskite phase with increasing X. There is a high activation energy for bulk proton conduction of about 0.77−0.80 eV.[25,26]
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