A double perovskite phase SmBaCo2O6-delta powder was successfully synthesized by the citric acid-nitrate gel combustion process after calcining at 900 degrees C for 4 h, using undissolved and relatively inexpensive Co3O4 as a starting material for the first time. TGA-DTA and XRD results revealed the formation mechanism of the double perovskite phase. The BaCoO3-delta was generated firstly, then the formation of Ba-doped SmCoO3-delta occurred, and finally Sm3+ and Ba2+ were distributed orderly, obtaining SmBaCo2O6-delta with a double perovskite phase. SEM analysis indicated that Co3O4 might play as a "template" in the synthesis process of SmBaCo2O6-delta via this special method. The conductivity of SmBaCo2O6-delta was still higher than 200 S cm(-1) at 850 degrees C, which is adequate as a cathode material for Solid Oxide Fuel Cells (SOFCs). (C) 2009 Elsevier B.V. All rights reserved.