Synthesis of SmBaCo₂O_6-δ powder by the combustion process using Co₃O₄ as precursor

A double perovskite phase SmBaCo₂O_6-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 BaCoO_3-δ was generated firstly, then the formation of Ba-doped SmCoO_3-δ occurred, and finally Sm³⁺ and Ba²⁺ were distributed orderly, obtaining SmBaCo₂O_6-δ with a double perovskite phase. SEM analysis indicated that Co₃O₄ might play as a "template" in the synthesis process of SmBaCo₂O_6-δ via this special method. The conductivity of SmBaCo₂O_6-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).