New cathode materials for solid oxide fuel cells - Ruthenium pyrochlores and perovskites

The ruthenium Pyrochlores, A(2)Ru(2)O(7-delta) (A = Pb Bi), and ruthenium p erovskites, (ARuO(3) (A = Ca, Sr) were characterized as new electrode mater ials fur solid oxide fuel cells. The electrical conductivity, cathodic pola rization, thermal expansion, and reactivity with yttria-stabilized zirconia were examined. The pyrochlores showed low cathodic overpotential even at 8 00 degrees C, metallic behavior with high electrical conductivity, and no r eaction with yttria-stabilized zirconia at 900 degrees C. The thermal expan sion coefficient of the bismuth pyrochlore was comparable to yttria-stabili zed (8 mol % Y2O3 content) zirconia. The pyrochlores are very attractive fo r application as cathode materials in a solid oxide fuel cell with low oper ating temperature. (C) 2000 The Electrochemical Society. S0013-4651(99)09-0 45-X. All rights reserved.