TY - JOUR

T1 - Electronic structure, phase formation, and defect distribution in the Ba(Ce,Fe,Acc)O3-δ system

AU - Merkle, Rotraut

AU - Hoedl, Maximilian Felix

AU - Chesnokov, Andrei

AU - Gryaznov, Denis

AU - Bucher, Edith

AU - Kotomin, Eugene A.

AU - Sitte, Werner

AU - Maier, Joachim

PY - 2025/1/12

Y1 - 2025/1/12

N2 - Composites of two perovskites are one possibility to combine protonic and p-type electronicconductivity as required for oxygen electrodes in protonic ceramic electrochemical cells. The BaCeO3-BaFeO3 system can be acceptor-doped to increase proton uptake and transport. However, precedingexperiments [C. Berger et al., J. Mater. Chem. A 10 (2022) 2474; C. Nader et al., Solid State Ionics406 (2024) 116474] indicated that the dopants are inhomogeneously distributed between the twophases, which is decisive for hydration ability and proton conductivity of such composites. Here, weuse extended density functional theory calculations (DFT+U, Hubbard approach) for a comprehensivecharacterization of the BaCeO3-BaFeO3 system including acceptors. Supercells of variouscompositions are calculated to derive chemical reaction energies, for example for the transfer of defectsbetween the phases. Two key aspects related to the hydration ability of such materials are: (i) Thedevelopment of the electronic structure with increasing Fe content in a (hypothetical) single-phaseBaCe1-xFexO3 perovskite. (ii) The distribution of acceptors (Ga3+, Sc3+, In3+, Y3+) and oxygen vacancies(VO••) between Ce- and Fe-rich phases. The segregation driving forces of acceptor dopant and VO •• arecalculated individually. VO•• have the largest driving force towards the Fe-rich phase; ion radii andacid/base properties of the different acceptor dopants play a secondary role. The co-segregation ofacceptors and VO •• into the ferrate phase unfortunately decreases the hydration ability of the Ce-richproton conductor phase. Analogous trends are expected for related proton- and hole-conductorperovskite composites, which partially counteracts the intended mixed conductivity.

AB - Composites of two perovskites are one possibility to combine protonic and p-type electronicconductivity as required for oxygen electrodes in protonic ceramic electrochemical cells. The BaCeO3-BaFeO3 system can be acceptor-doped to increase proton uptake and transport. However, precedingexperiments [C. Berger et al., J. Mater. Chem. A 10 (2022) 2474; C. Nader et al., Solid State Ionics406 (2024) 116474] indicated that the dopants are inhomogeneously distributed between the twophases, which is decisive for hydration ability and proton conductivity of such composites. Here, weuse extended density functional theory calculations (DFT+U, Hubbard approach) for a comprehensivecharacterization of the BaCeO3-BaFeO3 system including acceptors. Supercells of variouscompositions are calculated to derive chemical reaction energies, for example for the transfer of defectsbetween the phases. Two key aspects related to the hydration ability of such materials are: (i) Thedevelopment of the electronic structure with increasing Fe content in a (hypothetical) single-phaseBaCe1-xFexO3 perovskite. (ii) The distribution of acceptors (Ga3+, Sc3+, In3+, Y3+) and oxygen vacancies(VO••) between Ce- and Fe-rich phases. The segregation driving forces of acceptor dopant and VO •• arecalculated individually. VO•• have the largest driving force towards the Fe-rich phase; ion radii andacid/base properties of the different acceptor dopants play a secondary role. The co-segregation ofacceptors and VO •• into the ferrate phase unfortunately decreases the hydration ability of the Ce-richproton conductor phase. Analogous trends are expected for related proton- and hole-conductorperovskite composites, which partially counteracts the intended mixed conductivity.

U2 - 10.1016/j.actamat.2025.120739

DO - 10.1016/j.actamat.2025.120739

M3 - Article

VL - ??? Stand: 22. Jänner 2025

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

IS - ??? Stand: 22. Jänner 2025

ER -