Mechanical reliability of Ce_0.8Gd_0.2O_2−δ-FeCo₂O₄ dual phase membranes synthesized by one-step solid-state reaction

Ce_0.8Gd_0.2O_2−δ-FeCo₂O₄ composites are attractive candidate materials for high-purity oxygen generation providing robust chemical stability. Aiming for future industrial applications, a feasible solid-state reaction process with one thermal processing step was used to synthesize 50 wt% Ce_0.8Gd_0.2O_2−δ:50 wt% FeCo₂O₄ and 85 wt% Ce_0.8Gd_0.2O_2−δ:15 wt% FeCo₂O₄ composites. Mechanical reliabilities of the sintered membranes were assessed based on the characterized mechanical properties and subcritical crack growth behavior. In general, the fracture strengths of as-sintered membranes were reduced by tensile residual stresses and microcracks. In particular, the enhanced subcritical crack growth behavior, which leads to limited stress tolerance and high failure probability after a 10-year operation, was evaluated in more detail. Further materials and processing improvements are needed to eliminate the tensile stress and microcracks to warrant a long-term reliable operation of the composites.