Defect and Dopant Properties of the SrCeO₃-Based Proton Conductor

Atomic-scale studies using advanced simulation techniques have investigated the energetics of defects, oxygen migration, and dopant incorporation in the proton-conducting SrCeO 3 system. The interatomic potential model first reproduces the observed distorted perovskite structure of SrCeO 3 . Substitution with trivalent dopants (M) on the A site in SrCe(Yb)O 3 - δ (via V o • • consumption) is compared with substitution on the B site (via V o • • creation); the results support the premise that the absence of ionic conductivity at low doping levels is associated with dopant partitioning over both A and B sites. Dopant-vacancy association is predicted to occur in SrCe 0.9 M 0.1 O 2.95 for a wide range of M cations. Formation of (M‘ Ce −OH o • ) clusters is also calculated to be favorable in accordance with reported proton-trapping effects. The lowest M‘ Ce −OH o • binding energies and the largest M−H distances are found for the most common dopants for proton conductivity in the SrCeO 3 system, namely, Y and Yb. The pathway for oxygen migration is proposed as a curved trajectory with an asymmetric energy distribution. The lowest energy redox process is calculated to be oxidation with the formation of holes in accordance with the observation of p-type conductivity at increasing oxygen partial pressures ( p O 2 ).