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Study of the oxide layer formed on potential SOFC interconnect materials in dry and humid air

: Vargas, M.J.G.; Lelait, L.; Kolarik, V.; Fietzek, H.; Juez-Lorenzo, M.

Electrochemical Society -ECS-:
207th Meeting of the Electrochemical Society. Meeting abstracts. CD-ROM : Québec City, Canada, May 15 - 20, 2005 ; MA 2005-01
Pennington, NJ: ECS, 2005
Electrochemical Society (Meeting) <207, 2005, Québec>
Fraunhofer ICT ()

In the last years a greater importance has been given to several chromia-forming stainless steels as interconnects for solid oxide fuel cells (SOFC). These steels were selected due to a lower price and a good electrical conductivity without limiting the lifetime of the stack. The interconnect materials have to present a good behaviour not only in dry but also in humid air, which is the anode side atmosphere of the fuel cell. In this context, studies were performed on different chromia-forming alloys using high temperature X-ray diffraction (XRD) in dry and humid air, to evaluate in-situ the growth of the oxide scale (Fig.1). Afterwards, a microscopic analysis by field emission-scanning microscopy (FE-SEM) was done to verify the composition and structure of the oxide scale (Fig.2,3). Impedance measurements of the oxidized samples were carried out during temperature cycles in order to determine the electrical conductivity and activation energy of the oxide layer. The pape r will show the results obtained by oxidation at 800°C of two potential interconnect materials having a similar composition, Crofer 22 APU and ZMG 232 (Tab.1), which form principally chromia (Cr2O3) and the Cr-Mn spinel (MnCr2C4). A time evolution of the oxide formation and growth observed in the XRD analysis will also be presented (Fig.1). In addition, to corroborate this first approximation to the oxidation behaviour, the microscopy study of the surface and a transversal cut of the oxide scale will also be presented (Fig. 2,3).