Theoretical insights, structural and electrochemical characteristics of Lanthanum doped Sr2FeMoO6−δ

Abstract

In this study, we investigate the effects of lanthanum doping on the structural, electronic and ionic conduction, and electrochemical properties of the Sr_2-xLa_xFeMoO_6-δ perovskite oxide using a combined ab initio and experimental approach. The theoretical results are obtained using Density Functional Theory with Hubbard correction. Structural parameters are derived through full geometry optimization, also the electronic and ionic conduction mechanisms are investigated via spin- and orbital-resolved projected density of states analysis, oxygen vacancy formation energy and migration energy barriers calculations. The material is synthesized via the modified Pechini method, thermogravimetric analysis and differential scanning calorimetry are used to determine the calcination temperature while temperature-programmed reduction is employed to define the reducing conditions of the compounds. The formation of a single phase at low temperatures is confirmed by X-ray diffraction. Rietveld refinement X-ray diffraction of powder reveals crystalline symmetry compatible with theoretical predictions and is compared with other results in the literature. The theoretical results suggest that La substitution enhances overall conductivity. This prediction is supported by electrochemical testing, which shows that the 0.5 La-doped material exhibits the lowest activation energy and better electrochemical performances among the studied doping ratios, being a potential candidate for oxygen electrode applications in solid oxide fuel/electrolyzer cells.