Redox behavior and ionic conductivity of Al-doped Sr3LaFe3O10-δ

Mixed ionic-electronic conductors derived from Ruddlesden-Popper type Sr3LaFe3O10-delta are promising materials for numerous energy- and environment-related applications, such as electrodes of fuel cells, batteries and capacitors. In this work, oxygen deficiency and electrical conductivity of Sr3LaFe3xAlxO10-delta (x = 0.3-0.6) were studied at 973-1273 K in the oxygen partial pressure range from 10 (24) to 0.8 atm. The p(O-2)-T-delta diagrams determined by coulometric titration and thermogravimetry, were described by a statistical thermodynamic model taking into account the site-exclusion effects near oxygen vacancies, energetic non-equivalence of different crystallographic sites, and partial localization of electron holes in the vicinity of Al3+ cations. Doping with Al3+ was found to increase oxygen nonstoichiometry under oxidizing conditions and to decrease the electronic charge-carrier concentrations. Although the oxygen vacancy mobility tends to decrease on doping due to stable tetrahedral coordination of Al3+ cations, a moderate increase in the ionic conductivity with respect to parent Sr3LaFe3O10-delta is observed at x = 0.3 and temperatures below 1100 K. (C) 2020 Elsevier B.V. All rights reserved.