Thermal, electrical, and electrochemical properties of Nd-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ as a cathode material for SOFC

Crystal structure, thermal expansion coefficient (TEC), electrical conductivity and AC-impedance of (Ba0.5Sr0.5) 1_xNdCo0.8Fe0.2O3-delta (BSNCF; 0.10 <= x <= 0.20) were studied in relation to their potential use as intermediate temperature solid oxide fuel cell (IT-SOFC) cathode. An emphasis is made on the effect of Nd-doping on these properties. A single cubic pervoskite were observed in the X-ray diffraction (XRD) measurement. The TEC of BSNCF values were 18.7-19.7 x 10(-6) K-1 from 30 to 800 degrees C. The electrical conductivity, which is the main defect of Ba0.5Sr0.5 Co0.8Fe0.2O3-delta (BSCF), was improved by Nd-doping, e.g. the compound of x=0.20 demonstrated a conductivity of sigma= 130 S.cm(-1) at 392 degrees C. The AC-impedance analyses were carried out on an electrolyte supported BSNCF/ Sm0.2Ce0.8O1.9 (SDC)/Ag half-cell and a BSCF/SDC/ Ag half-cell. The BSNCF cathode revealed lower polarization resistance than BSCF, e.g. at 500 degrees C, the values for the x=0.20 sample and BSCF were 1.79 Omega cm(2) and 4.52 Omega cm(2), respectively. (C) 2007 Elsevier B.V All rights reserved.