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