A solid oxide fuel cell with Sm0.2Ce0.8O1.9 (SDC) electrolyte of 10 mu m in thickness and Ni-SDC anode of 15 mu m in thickness on a 0.8 mm thick Ni-YSZ cermet substrate was fabricated by tape casting, screen printing and co-firing. A composite cathode, 75 wt.% Sm0.5Sr0.5CoO3 (SSCo) + 25 wt.% SDC, approximately 50 mu m in thickness, was printed on the co-fired half-cell, and sintered at 950 degrees C. The cell showed a high electrochemical performance at temperatures ranging from 500 to 650 degrees C. Peak power density of 545 MW cm(-2) at 600 degrees C was obtained. However, the cell exhibited severe internal shorting due to the mixed conductivity of the SDC electrolyte. Both the amount of water collected from the anode outlet and the open circuit voltage (OCV) indicated that the internal shorting current could reach 0.85 A cm(-2) or more at 600 degrees C. Zr content inclusions were found at the surface and in the cross-section of the SDC electrolyte, which could be one of the reasons for reduced OCV and oxygen ionic conductivity. Fuel loss due to internal shorting of the thin SDC electrolyte cell becomes a significant concern when it is used in applications requiring high fuel utilization and electrical efficiency. (c) 2006 Elsevier B.V. All rights reserved.