Abstract: The electrolytes materials Ce_0.85Sm_0.15O_1.925(SDC) and La_0.9Sr_0.1Ga_0.8Mg_0.2O_2.85(LSGM) were synthesized by means of glycine-nitrate process(GNP), respectively, then the composite electrolytes were prepared by mixing SDC and LSGM(the mass ratio of SDC powder to LSGM powder are 9∶1, 8∶2, 5∶5, respectively). Its electrical properties were investigated by impedance spectroscopy in air. The results obtained shows that when the composition was 90% SDC and 10%(mass fraction) LSGM(SL91), the electrolyte has a higher electrical conductivity in comparison to SDC in the temperature range of 350—800 ℃. Electrolyte-supported solid oxide fuel cells(SOFC) was fabricated with NiO/SDC as the anode and Sm_0.5Sr_0.5CoO₃ as the cathode. The V-I characteristics of single fuel cell shows that the maximum output power density was 0.25 W/cm² at 800 ℃ and the maximum current density was 1.06 A/cm² for the cell with SL91 as the electrolyte. The open circuit voltage(OCV) of the single fuel cell using the composite as the electrolytes was higher than the cell using single SDC as the electrolyte in the working temperature range of 600—800 ℃. It can be confirmed that to some extent, doping LSGM to SDC can block off the electronic current caused by the Ce⁴⁺/Ce³⁺ reduction process.

Key words: Intermediate-temperature solid oxide fuel cell, Ce_0.85Sm_0.15O_2-δ, La_0.9Sr_0.1Ga_0.8Mg_0.2O_3-δ, Composite electrolyte