abstract
NiO-Ce0.9Gd0.1O1.95 (NiO-CGO) composite powders produced by a one-step chemical route were assessed as precursors of fuel cell anode cermets. Porous NiO-CGO composites were prepared by uniaxial pressing followed by firing at 1400 degrees C for 4 h. Ni-CGO cermets were subsequently obtained by reduction in 10 vol% H-2 + 90 vol% N-2 at 750 degrees C. Similar materials obtained by conventional mechanical mixing of commercial powders were also prepared and tested. The structure and particle size of the calcined material were investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). The electrical properties of all materials were duly studied by impedance spectroscopy (NiO-CGO) (in air and several N-2 + O-2 gas mixtures) or dc conductivity (Ni-CGO). The total and relative magnitude of impedance arcs observed in the low temperature impedance spectra can be used to obtain significant insight on microstructural characteristics, due to a variable role of NiO when shifting from a well percolated electronic conducting pathway to a dispersed ion-blocking phase. The confirmed superior conductivity of one-step materials was interpreted as a consequence of the presence of a network of well-connected and homogeneously distributed NiO(/Ni) grains, as shown by SEM.
keywords
OXIDE FUEL-CELLS; X-RAY-DIFFRACTION; NANOCOMPOSITE POWDERS; ELECTRICAL-PROPERTIES; SOFC ELECTRODES; GDC COMPOSITES; ANODE; BLOCKING; MICROSTRUCTURE; DEGRADATION
subject category
Chemistry; Physics
authors
Grilo, JPF; Macedo, DA; Nascimento, RM; Marques, FMB
our authors
Fernando Manuel Bico Marques
Full professor
João Grilo
Junior Researcheracknowledgements
The authors would like to express their appreciation for the financial support of CNPq (Brazil, 447797/2014-0) and from CICECO-Aveiro Institute of Materials, project POCI-01-0145-FEDER-007679 (Ref. FCT UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.