Plasma sprayed LSCF oxygen electrode for SOFC

摘要

La_(1-x)Sr_xCo_(0.2)Fe_(0.8)O_(3-δ) deposits, of different stochiometery, were fabricated for SOFC oxygen electrode using atmospheric plasma spraying (APS) with TriplexPro gun. The spraying conditions were developed by correlating, plasma jet characteristics (enthalpy and velocity), in-flight particle properties (temperature and velocity) and deposit quality (phase composition, porosity, coefficient of thermal expansion, electrochemical testing). The optimal cathode deposits exhibited a porosity of about 20 vol.%. The CTE in air flow at 800℃ was, however, 15.6×10~(-6) K~(-1) and it was independent of the processing conditions. Electrochemical tests for cathodes were conducted on SOFCs that were produced following metal supported design and had YSZ as electrolyte and NiO+YSZ as anode. At 800℃, power densities of above 640 mW/cm~2 at 0.7 V were recorded with H_2/air for cell having La_(0.60)Sr_(0.40)Co_(0.2)Fe_(0.8)O_(3-δ) as cathode. Cells consisting of La_(0.58)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) and La_(0.78)Sr_(0.2)Co_(0.2)Fe_(0.8)O_(3-δ) had 479 and 496 mW/cm~2 under similar conditions. Using equivalent circuit diagrams the contribution of different polarizations on the cell performance were separated and cathodes were compared. La_(0.60)Sr_(0.40)Co_(0.2)Fe_(0.8)O_(3-δ) was found to have the best electrochemical performance followed by La_(0.58)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) and La_(0.78)Sr_(0.2)Co_(0.2)Fe_(0.8)O_(3-δ).