Mechanical properties of proton conductor ceramics: pristine and fully hydrated

Following a literature review to address the existing gaps, this study analyzes the mechanical behavior of the proton-conducting ceramics BZY20 ( BaZ r 0.8 Y 0.2 O 3 − δ ) and BCZYYb7111 ( BaC e 0.7 Z r 0.1 Y 0.1 Y b 0.1 O 3 − δ ), in pristine and fully hydrated states. Key mechanical properties, including elastic modulus, fracture stress, and fracture toughness, are evaluated together with the statistical variability of fracture stress, to assess material reliability and the influence of processing-induced defects. The results highlight distinct mechanical responses between the two compositions with BZY20 exhibiting superior mechanical properties compared to the cerium-rich composition. However, hydration reduces fracture stress and toughness in BZY20, associated with lattice expansion, and a partial shift toward intragranular fracture. In contrast, BCZYYb7111 displays hydration-induced toughening behavior, driven by a transition from predominantly intergranular to intragranular fracture. Overall, these findings suggest that the mechanical performance of proton-conducting ceramics is governed by an interaction between composition, crystal structure, microstructure, and hydration. The results also provide insights for mechanically robust protonic ceramics and support the development of durable, scalable materials for long-term energy applications.