Characterization of GdBa1 − x Sr x Co2O5 + δ ( 0 ⩽ x ⩽ 1.0 ) Double Perovskites as Cathodes for Solid Oxide Fuel Cells

By Jung-Hyun Kim, F. Prado, Arumugam Manthiram. 2008

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The effect of Sr2 + substitution for Ba 2+ on the crystal chemistry, oxygen content, thermal expansion, electrical conductivity, and catalytic activity for oxygen reduction reaction (ORR) of the double perovskite oxides GdBa 1-x Sr x Co 2 O 5+δ has been investigated for 0 ≤ x ≤ 1.0. The GdBa 1-x SrCo 2 O 5+δ system exhibits a structural change from orthorhombic (x = 0) to tetragonal (0.2 as x ≤ 0.6) to orthorhombic (x = 1) with increasing Sr content. The difference in ionic radii between (Ba 1-x Sr x ) 2+ and Gd 3+ plays a dominant role in determining the oxygen-content value in GdBa 1-x Sr X Co 2 O 5+δ , and the oxygen content and the oxidation state of cobalt increase with increasing Sr content. The electrical conductivity of the GdBa 1-x Sr x Co 2 O 5+δ system increases with Sr content due to an increasing oxygen content and a straightening of the O-Co-O bonds as evidenced by the structural change from orthorhombic to tetragonal. Sr substitution also improves the chemical stability of the GdBa 1-x Sr x Co 2 O 5+δ cathodes in contact with the Ce 0.9 Gd 0.1 O 1.95 and La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 2.8 electrolytes at 1100°C. The x = 0.2 and 0.6 samples with a tetragonal structure exhibit higher catalytic activity for ORR in single-cell solid oxide fuel cell than the x = 0 and 1.0 samples with an orthorhombic structure.

Subfields: Electronic, Optical and Magnetic Materials, Materials Chemistry

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