SOFC Composite Cathodes Based on Perovskite and Fluorite Structures

摘要

This work presents the results related to the functionally graded fluorite (F) -perovskite (P) nanocomposite cathodes for IT SOFC. Nano-crystalline fluorites (GDC, ScCeSZ) and perovskites (LSrMn, LSrFNi) were synthesized by Pechini method. Nanocomposites were prepared by the ultrasonic dispersion of F and P powders in iso-propanol with addition of polyvinyl butyral. Different techniques for deposition and sintering of functionally graded cathode materials were applied including traditional approaches as well as original methods, such as radiation - thermal sintering under electron beam or microwave radiation. Morphology, microstructure and elemental composition of nano-composites was characterized by XRD and HRTEM/SEM with EDX. Even for dense composites, the sizes of perovskite and fluorite domains remain in the nano-range providing developed P-F interfaces. Oxygen isotope hetero-exchange and conductivity relaxation studies demonstrated that these interfaces provide a path for fast oxygen diffusion. The redistribution of the elements between P and F phases in nanocomposites occurs without formation of insulating zirconate phases. Button-size fuel cells with nano-composite functionally graded cathodes, thin YSZ layers and anode Ni/YSZ cermet (either bulk or supported on Ni-Al foam substrates) were manufactured. For optimized composition and functionally graded design of P-F nano-composite cathodes, a stable performance in the intermediate temperature range with maximum power density up to 0.5W/cm2 at 700 in wet H2/air feeds was demonstrated.