Low-temperature densification of constrained GDC interlayers via chemo-mechanical regulation for stable solid oxide fuel cells

Constrained densification of ceramic interlayers in solid oxide fuel cells (SOFCs) is strongly influenced by the interplay between constraint effects and diffusion kinetics. While elevated sintering temperatures are commonly employed to overcome stress-retarded densification, they simultaneously accelerate interfacial interdiffusion and reaction-layer formation, creating a long-standing trade-off between microstructural integrity and chemical stability. Here, we demonstrate a chemo-mechanical regulation strategy that effectively mitigates the conflict between these competing processes through concurrent enhancement of sintering kinetics and regulation of green-state packing homogeneity. By combining Co3O4-assisted sintering activation with cold isostatic pressing (CIP), ultrathin Gd-doped ceria (GDC) interlayers achieve an apparent relative density of 98.5% after constrained sintering, enabling densification at 1200 °C, below the temperatures commonly reported for constrained GDC films processed without sintering activation. The resulting dense and continuous interlayer limits Ce–Zr interdiffusion during fabrication and mitigates Sr-related interfacial reaction and reaction-layer formation during operation. Consequently, the optimized anode-supported SOFC delivers a peak power density of 1.36 W·cm−2 at 800 °C and exhibits a normalized degradation rate of 0.48% per 1000 h, calculated from the stabilized 200–460 h operation period at 750 °C. Accelerated thermal aging at 850 °C for 600 h further supports the stability of the engineered heterointerface. The chemo-mechanical strategy was successfully extended to 10 × 10 cm2 cells, supporting its compatibility with scalable wet-processing routes. This work provides a chemo-mechanical perspective for mitigating the interplay between constrained densification and interfacial reactivity in multilayer ceramic systems.