Self‐Compressive Stress Promoting Densification of Proton‐Conducting Electrolyte Membranes

Dense asymmetric ceramic membranes are key components in solid oxide cells (SOCs) and gas separation technologies. In particular, proton-conducting SOCs efficiently generate power and hydrogen at low temperatures. However, high-temperature sintering of these membranes causes elemental volatilization, segregation, and migration, significantly reducing the protonic conductivity of the electrolyte layer (e.g., BaCe_0.7Zr_0.1Y_0.2O_3-δ (BCZY712)) and limiting cell performance. Here we report a self-compressive stress strategy to promote densification of a BCZY712 proton-conducting electrolyte layer. By precisely regulating the pore former content and the pre-sintering temperature of the anode substrate which shrinks more than the electrolyte layer, a compressive stress is applied to the electrolyte layer. Under the compressive stress, the densification temperature decreased by ∼150 °C, achieving a relative density of ∼99%. The reduced co-sintering temperature effectively suppresses barium evaporation, Y₂O₃ impurity segregation, and Ni migration from the anode substrate to the electrolyte. Consequently, the electrolyte exhibits a markedly 151%-higher conductivity and the cell delivers an 89%-improved peak power density compared to a cell co-sintered at conventional high-temperature.