Synthesis and characterization of Gd1-xSrxMnO3 cathode for solid oxide fuel cells

Gd1-xSrxMnO3 (0 less than or equal tox less than or equal to0.6) is synthes ized as the cathode material for solid oxide fuel cells (SOFC) using a citr ate process. Properties of the oxides such as the crystal structure, electr ical conductivity, thermal expansion coefficient (TEC) and reactivity with 8 mol% yttria-stabilized zirconia (8YSZ) or Ce0.8Gd0.2O1.9 (CGO) electrolyt e are investigated. The crystal structure is orthorhombic (0 less than or e qual tox less than or equal to0.3), cubic (0.4 less than or equal tox less than or equal to0.5) or tetragonal (x=0.6), as dictated by the composition. The electrical conductivity increases, but the activation energy for condu ction decreases, with increasing Sr content. The TEC displays normal behavi or for x greater than or equal to0.3 and increases with increasing Sr conte nt. When heated at 1300 degreesC for 48 h, Gd1-xSrxMnO3 reacts with 8YSZ to produce SrZrO3, but does not react at all with CGO. The cathodic polarizat ion of the mixed cathode, Gd0.6Sr0.4MnO3-delta-CGO, is reduced with increas e in the CGO content. The maximum power density is about 210 mW/cm(2) in th e vicinity of 50 vol.% CGO in the mixed cathode at an operating temperature of 800 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.