Revealing the Atomic Scale Mechanism Behind Multi-Dopant Dispersion Driving Enhanced Oxygen-Ion Conduction in Nb-Ta Co-Doped BaCoO3 Perovskite.

Ion conduction in perovskites plays a crucial role in the performance of energy storage and conversion devices. While multielement doping is a well-established strategy to enhance ionic conductivity, the underlying mechanisms─particularly the relationship between dopant spatial arrangement and ionic conductivity─remain poorly understood. In this study, we introduce a degree of dispersion (DOD) metric to quantify the spatial arrangement of dopants in BaCo0.7Fe0.2Nb0.05Ta0.05O3 (BCFNT), an oxygen-ion conductor. Using deep-learning potential molecular dynamics (DPMD), we simulate large supercells and show that higher DOD correlates with faster oxygen-ion transport. This is due to oxygen ions preferentially migrating toward Ta atoms and away from Nb atoms in BCFNT, as indicated by ab initio molecular dynamics (AIMD) results. The thermodynamically favored spatial separation of Nb and Ta dopants creates efficient transport pathways, explaining why codoped materials exhibit superior conductivity compared to singly doped ones. Experimental validation, including relaxation time distribution analysis, confirms the favorable oxygen-ion transport properties of BCFNT, with a low activation energy of 78.83 kJ/mol for the oxygen reduction reaction. These findings highlight the link between dopant distribution and conductivity, offering a path for optimizing ionic conductors.