Atomistic Study of Doped BaCeO₃:  Dopant Site-Selectivity and Cation Nonstoichiometry

Abstract

Rare earth (or yttrium) doped BaCeO 3 has been widely investigated as a proton conducting material. Usually, the trivalent dopants are assumed to occupy the Ce 4+ -site, which introduces oxygen vacancies into the perovskite structure and furthers the protonic conductivity. Recent studies indicate the possibility of dopant incorporation on the Ba 2+ -site, which is unfavorable for protonic conductivity. In this work atomistic simulation techniques, especially the supercell approach, have been developed to investigate the questions of dopant site-selectivity and cation nonstoichiometry in doped BaCeO 3 . Our calculations predict that, on energetic grounds, Ba 2+ -site deficiency shifts trivalent dopant incorporation onto the Ba 2+ -site. These results confirm that the dopant partitioning or site-occupancy of trivalent dopants will be sensitive to the precise Ba/Ce ratio, and hence to the experimental processing conditions. The relative energies explain the experimentally observed "amphoteric" behavior of Nd with significant dopant partitioning over both Ba and Ce sites. Such partitioning reduces the concentration of oxygen vacancies, which, in turn, lowers proton uptake and decreases proton conductivity relative to dopant incorporation solely on the Ce 4+ site.

Performance and stability of proton conducting solid oxide fuel cells based on yttrium-doped barium cerate-zirconate thin-film electrolyte

“…The diffraction patterns of BCZY heat-treated at high temperatures over 900 ºC show peak shift towards higher 2 theta, indicating a smaller unit cell volume than the stoichiometric compound, resulting from the loss of BaO at high temperatures [47]. Ba-deficient doped barium cerate formed by the loss of BaO can readily incorporate a B-site doping element with a smaller ionic radius than Ba 2+ onto the A-site as described by the equation (4), resulting in the decrease of a unit cell volume [48].…”

Correlation between Thermal Properties, Electrical Conductivity, and Crystal Structure in the BaCe0.80Y0.20O2.9 Proton Conductor

“…With the progress in the synthesis and characterization of the newly discovered materials, such as the BaCeO 3 and CaZrO 3 perovskites, an intense research has also been devoted to the comprehension of the defect chemistry of the same materials, in order to optimize their performance and build the basis for the development of other solid-state proton conductors [10][11][12][13][14][15] (1) with oxygen vacancies constituting the site for the incorporation of water in the form of hydroxyl groups through:…”

Atomistic Study of a CaTiO3‐Based Mixed Conductor: Defects, Nanoscale Clusters, and Oxide‐Ion Migration

“…Atomistic simulation techniques are wellsuited to studying defect properties on this scale, as demonstrated in previous simulations of oxide-ion and proton conductors such as LaGaO 3 [22,23] and BaCeO 3 . [24,25] Herein, we have employed a wide-ranging sequence of atomistic simulations to address a number of important topics concerning pure and substituted CaTiO 3 , with particular attention paid to its application as a mixed-conducting membrane. These include the energetic and mechanistic features of intrinsic defects, dopant incorporation, defect-cluster formation and oxide-ion migration.…”