Examination of wet coating and co-sintering technologies for micro-SOFCs fabrication

Preparation conditions to obtain a dense electrolyte layer on a micro-tubular electrode support were investigated using wet coating and subsequent co-firing techniques. An anode-supported micro-tubular SOFC with 1.5 mm diameter was successfully fabricated by careful control of the co-sintering process of electrolyte/anode support laminates. The densification of the electrolyte layer deposited on the support surface was greatly affected by the shrinkage of tubular support during the co-sintering process. Support shrinkage above 15% was found to produce a fully densified electrolyte layer on the anode support. In contrast, the use of an anode support with shrinkage below 10% constrained gadolinium-doped ceria (GDC) sintering, resulting in a poorly densified GDC microstructure. Finally, we obtained a micro-tubular cell composed of a dense GDC and a porous (La,Sr)(Co,Fe)O3–GDC multi-layered structure on a NiO–GDC micro-tubular anode support. The cell, with a dense and ≈15 μm thick GDC electrolyte layer, was electrochemically evaluated in a temperature range from 450 to 550 °C. This micro-tubular cell with an electrode length of 6.3 mm showed a power density above 0.1, 0.2 and 0.4 W/cm2 at 450, 500 and 550 °C, respectively, in wet H2 fuel flow.