Ceramic fuel cells and H2 permeation membranes are key technologies to accelerate the transition from a carbon economy based on fossil fuels to a H2 economy based on the use of renewable resources. The competitiveness of these technologies in the market depends on the identification and optimization of stable and effective low-cost materials. Perovskite−fluorite ceria-based composites show suitable properties, and studies on the mechanism that rules their mechanical, thermal, and redox stability are crucial for further technological advances. This study focuses on the redox behavior of BaCe0.65Zr0.20Y0.15O3−δ−Ce0.85Gd0.15O2−δ (BCZY−GDC) dual-phase ceramic. Temperature-programmed reduction, thermogravimetry, temperature-dependent X-ray diffraction, and Raman analyses are used to understand the dynamics of the interaction between the ceramic oxide components. It is shown how the simultaneous occurrence of structural changes in BCZY and GDC reduction helps in decreasing the mechanical stresses induced by temperature and by the reducing atmosphere. The interfacial processes between the single GDC and BCZY oxides contribute to limit reduction of GDC in the composite, which allows complete reversibility of the redox process investigated in this study. Thus, it is suggested that the redox behavior of this class of materials may be a descriptor of their mechanical and thermal stability.
