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

Mixed oxide‐ion and electronic conductivity can be exploited in dense ceramic membranes for controlled oxygen separation as a means of producing pure oxygen or integrating with catalytic oxidation. Atomistic simulation has been used to probe the energetics of defects, dopant‐vacancy association, nanoscale cluster formation, and oxide‐ion transport in mixed‐conducting CaTiO 3 . The most favorable energetics for trivalent dopant substitution on the Ti site are found for Mn 3+ and Sc 3+ . Dopant‐vacancy association is predicted for pair clusters and neutral trimers. Low binding energies are found for Sc 3+ in accordance with the high oxide‐ion conductivity of Sc‐doped CaTiO 3 . The preferred location for Fe 4+ is in a hexacoordinated site, which supports experimental evidence that Fe 4+ promotes the termination of defect chains and increases disorder. A higher oxide‐ion migration energy for a vacancy mechanism is predicted along a pathway adjacent to an Fe 3+ ion rather than Fe 4+ and Ti 4+ , consistent with the higher observed activation energies for ionic transport in reduced CaTi(Fe)O 3–δ .