In this work, we have developed solid oxide fuel cells with a bi-layered electrolyte of 2 mu m SSZ and 4 mu m SDC using tape casting, screen printing, and co-firing processes. The cell reached power densities of 0.54 W cm(-2) at 650 degrees C and 0.85 W cm(-2) at 700 degrees C, with open circuit voltage (OCV) values larger than 1.02 V. The electrical leaking between anode and cathode through an SDC electrolyte has been blocked in the bi-layered electrolyte structure. However, both the electrolyte resistance (R-el) and electrode polarization resistance (R-p,R-a+c) increased in comparison to cells with single-layered SDC electrolytes. The formation of a solid solution of (Ce, Zr)O2-x during sintering process and the flaws in the bi-layered electrolyte structure seem to be the main causes for the increase in the R-el value (0.32 Omega cm(2)) at 650 degrees C, which is almost one order of magnitude higher than the calculated value. Crown Copyright (C) 2007 Published by Elsevier B.V. All rights reserved.