Study on the Conductivity of La sub(0.4)Sr sub(1.6)CoNbO sub(6- delta ) as an Electrode Material for Symmetrical SOFC

The double-perovskite La sub(0.4)Sr sub(1.6)CoNbO sub(6- delta ) (LSCN) powders were synthesized by the solid-state reaction method. The electrical conductivities of LSCN samples were tested in air and 5 vol%H sub(2)/Ar. The results show that the conductivity of LSCN in 5 vol%H sub(2)/Ar (8.12 Scm super(-1)) at 850 [degrees]C was higher than that in air (7.03 Scm super(-1)). The activation energy obtained from the Arrhenius function was 0.821 eV in air and 0.707 eV in 5 vol%H sub(2)/Ar. The analysis of XPS shows that there exit three valence states of Co (Co super(+2), Co super(+3), Co super(+4)) and two of Nb (Nb super(+4), Nb super(+5)). The loss of lattice oxygen in LSCN not only produces oxygen vacancies, but also generates excess electrons, which contributes to the electrical conductivity of the LSCN samples.