Computational and experimental analysis of Ba0.95La0.05FeO3−δ as a cathode material for solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) may play a crucial role in solving the energy crisis because they are clean and energy efficient. Finding suitable cathode materials for SOFCs is key to facilitating their widespread use. Besides developing high performance materials, understanding the stability and intrinsic properties of a material is equally important. Herein, Ba_0.95La_0.05FeO_3−δ (BLF) is studied combining molecular simulations and experiments on single crystal thin films. Lattice dynamics simulations are applied to study the stabilization of barium orthoferrate BaFeO_3−δ upon doping with La³⁺. Simulation results reveal the defect energy for substituting one Ba²⁺ with La³⁺ in the cubic phase to be lower than that in the monoclinic phase, contributing to its stabilization. Analogous results are also found by doping the Ba site with Sm³⁺, Gd³⁺ and Y³⁺. In addition, the simulation results suggest that the charge compensation mechanism upon doping is filling oxygen vacancies and La³⁺ tends to trap the mobile oxygen anions. In turn, as the doping level increases the oxygen anion diffusivity decreases, as is also supported by molecular dynamics simulations. In light of this conclusion, single crystal thin films of La³⁺ slightly doped BaFeO_3−δ, BLF, are grown on yttria-stabilized zirconia substrates using pulsed laser deposition. The polarization resistance of the dense film is 0.07 Ω cm² at 700 °C in an ambient atmosphere, which is comparable to state-of-the-art Co-based materials.