TY - JOUR
T1 - Atomistic study of doped BaCeO3
T2 - Dopant site-selectivity and cation nonstoichiometry
AU - Wu, J.
AU - Davies, R. A.
AU - Islam, M. S.
AU - Haile, S. M.
PY - 2005/2/22
Y1 - 2005/2/22
N2 - Rare earth (or yttrium) doped BaCeO3 has been widely investigated as a proton conducting material. Usually, the trivalent dopants are assumed to occupy the Ce4+-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 BaCeO3. Our calculations predict that, on energetic grounds, Ba2+-site deficiency shifts trivalent dopant incorporation onto the Ba2+-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 Ce4+ site.
AB - Rare earth (or yttrium) doped BaCeO3 has been widely investigated as a proton conducting material. Usually, the trivalent dopants are assumed to occupy the Ce4+-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 BaCeO3. Our calculations predict that, on energetic grounds, Ba2+-site deficiency shifts trivalent dopant incorporation onto the Ba2+-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 Ce4+ site.
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U2 - 10.1021/cm048763z
DO - 10.1021/cm048763z
M3 - Article
AN - SCOPUS:13944282010
SN - 0897-4756
VL - 17
SP - 846
EP - 851
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 4
ER -