Impact of strontium non-stoichiometry of SrxTi0.3Fe0.7O3-d on structural, electrical, and electrochemical properties for potential oxygen electrode of intermediate temperature solid oxide cells

This work presents the results of a comprehensive study on the impact of the A-site non-stoichiometry of SrxTi0.3Fe0.7O3-d (x = 0.90, 0.95, 1.00, 1.05) ceramics on their physico-chemical properties. The materials were fabricated by the conventional solid-state reaction method and their structure was determined by X-ray diffractometry, X-ray photoelectron spectroscopy and electron microscopy. Their sintering and thermal expansion properties were then evaluated. The electrical properties of the materials were determined by elec-trical conductivity and electrical relaxation measurements (on bulk materials) and by electrochemical impedance spectroscopy (EIS) studies of symmetrical, CGO-electrolyte based, porous electrodes. Finally, fuel cell tests with the non-stoichiometric electrodes were evaluated. To elucidate the electrochemical reaction pathways for oxygen reduction/ evolution reaction, EIS measurements were carried out in different pO2 and were analysed via the distribution of relaxation times method. The results showed a dependence of materials' properties on the A-site non-stoichiometry, which can be used to fine-tune their properties, e.g. increase the surface exchange rate or decrease the thermal expansion coefficient.(c) 2023 The Authors. Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY license (http://creativecommons.org/ licenses/by/4.0/).

Automated summary

This work presents a comprehensive study on the impact of A-site non-stoichiometry on the physico-chemical properties of SrxTi0.3Fe0.7O3-d ceramics. The study includes structural analysis, evaluation of sintering and thermal expansion properties, determination of electrical properties, and fuel cell tests. The results show a dependence of the materials' properties on A-site non-stoichiometry.