Microstructure, oxygen stoichiometry and electrical conductivity of flame-sprayed Sm0.7Sr0.3CoO3−δ

A SSC deposit has been prepared by flame spraying using Sm0.7Sr0.3CoO3−δ (SSC) powder synthesized by a solid-state reaction. A post-spray annealing treatment of the SSC deposit has been performed. The coating characterization includes: the electrical conductivity of the SSC deposit along the lamellar direction measured by a four-electrode D.C. approach, the microstructures of SSC powders and deposits characterized using X-ray diffraction and scanning electron microscopy, the oxygen stoichiometry in both the as-sprayed and annealed deposits and starting powder determined by redox titration. The results show that a significant oxygen deficiency (12%) occurs in the sprayed powder particles during high temperature flame spraying, leading to reduction of the electrical conductivity of the as-sprayed SSC deposit. It is found that oxygen can be recovered through post-spray annealing treatment. After annealing at 900 °C for 5 h or at 1100 °C for 10 h, the electrical conductivity of annealed SSC reaches 433 S cm−1 or 510 S cm−1 at 600 °C due to a sharp recovery of deficient oxygen and microstructural change.