Highly dense (Mn,Co)3O4 spinel protective coating derived from Mn–Co metal precursors for SOFC interconnect applications

Abstract

The major degradation issues of solid oxide fuel cells (SOFC) are associated with the Cr2O3 scale growth and Cr diffusion of the Cr-based ferritic stainless steel (FSS) interconnects. Although (Mn,Co)3O4 has been proved as a suitable material for protecting FSS interconnects, the porous structure of the coatings prepared with the pre-synthesized spinel weakens the protective capability of the coatings. In this paper, the widely-used pre-synthesized spinel is replaced with metal precursors (Mn and Co powders). Due to the low melting point (≤1290 °C) and the volume expansion during oxidation, the metal precursors, can be effectively sintered at 900 °C in a reducing atmosphere and form dense, well-protective coatings at 850 °C in the air. The samples are characterized with X-ray diffraction (XRD), scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), and a 4-probe area-specific resistance (ASR) test. Compared with the coatings derived from pre-synthesized spinel, the metal-derived coatings present denser structures with better electrical conductivity (ASR = 5.76 mΩ cm2). The weight gain and ASR measurement results indicate that the metal-derived coatings significantly mitigate the increase of weight gain and ASR by inhibiting scale formation and growth, showing better protective capability for SOFC applications.