Fabrication and characterisation of La0.8Sr0.2MnO3/metal interfaces for application in SOFCs

Fabrication and characterisation of La(0.8)Sr(0.2)MnO(3) (LSMO)/metal interfaces are important for the application of LSMO as the cathode and the metal as the interconnector in solid oxide fuel cells (SOFCs). Interfaces between LSMO and either Fecralloy, or Cr-5Fe-Y(2)O(3), or Pt metal were fabricated by using screen printing, followed by sintering at 1200 degreesC in different atmospheres. The microstructures of these LSMO/metal interfaces were examined using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) and X-ray diffraction analysis. The electrical properties were characterised using impedance spectroscopy. The LSMO/Fecralloy interface fabricated in air shows a high electrical resistance (about 10(5) Ohm cm(2) at 800 degreesC) due to the formation of an interlayer consisting of alumina and the mixed oxide M(2)O(3). nAl(2)O(3) at the interface during the fabrication process. When the interface was fabricated at 1200 degreesC in argon or vacuum, a thicker interfacial layer was formed compared with that formed in air. In addition, the La(0.8)Sr(0.2)MnO(3) decomposed into (La(0.8)Sr(0.2))(2)MnO(4+lambda), (La, Sr)(2)O(3) and MnO. Annealing of the specimen at 1200 degreesC for 5 h in air can partially reverse the decomposition. The interface resistance of the annealed sample across the interface is one order of magnitude lower than that of an interface fabricated in air. A thick Cr(2)O(3) layer was found at the LSMO/Cr-5Fe-Y(2)O(3) interface fabricated in air and a spinel phase (Mn, Cr)(3)O(4) formed a network surrounding LSMO grains due to the reaction between LSMO phase and CrO(3) vapour released from the Cr(2)O(3) layer during the fabrication. The electrical resistances of both phases are high at room temperature, but become significantly lower at 400 degreesC. They can be negligible above 500 degreesC. However the evaporation of CrO(3) increases the resistivity of the LSMO layer. No reaction or oxidation interlayer was found between LSMO and Pt metal producing an interface resistance of 0.52 Ohm cm(2) at room temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.