Atomic-scale insight into LaFeO3 perovskite:: Defect nanoclusters and ion migration

Atomistic simulation techniques are employed to investigate the energetics of defect formation, dopant-defect association, and ion migration in orthorhombic LaFeO3 in relation to electrochemical applications. Point defect calculations suggest that intrinsic Schottky or Frenkel disorder is not significant. The results of redox reaction calculations suggest that at high oxygen partial pressures doped LaFeO3 will oxidize with the formation of holes, contributing to the p-type electronic conductivity that is observed experimentally. The binding energies of selected dopant-vacancy clusters are also derived. A minimum in the binding energy was found for Sr2+ on the La3+ site, which would be beneficial to oxide ion conductivity. Larger complex defect clusters within 2D and 3D configurations have also been considered as they may be important as precursors to possible short-range ordering or "nanodomain" formation. A number of different pathways for oxygen migration by a vacancy mechanism are investigated; the lowest activation energy for this process is via a curved path between oxygen sites. We also examine cation-vacancy transport in LaFeO3 and determine the migration energies for La and Fe migration.