Investigation of CuxMn3-xO4 coatings for solid oxide fuel cell interconnect applications

Abstract

In order to investigate the performance of Cu–Mn spinel coatings used for solid oxide fuel cell interconnect, a series of CuxMn3-xO4 (x = 0.6, 0.8, 1.0, 1.1, 1.2, and 1.3) coatings are prepared using supersonic spraying via subsequent sintering. The chemical composition and distribution, lattice structures, morphology, and electrical properties are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and area-specific resistance (ASR) measurements. The experimental results show that with the increase of Cu concentration in the coatings, the crystalline structure gradually changes from inverse spinel into normal spinel, especially when 0.6 ≤ x ≤ 1.0. An improvement in electrical conductivity accompanies the crystalline structural transformation. The coatings show high electrical conductivity when 1.0 ≤ x ≤ 1.3, especially from 600 to 800 °C. However, the scale (mainly Cr2O3) is reactive to the CuxMn3-xO4 coatings (especially when 1.1 ≤ x ≤ 1.3) at elevated temperatures. During the long-term experiment, the reaction corrodes the coatings, consumes the materials in coatings and scale, and forms new phases (mainly (Cu,Mn,Cr)3O4 and (Cr,Mn)3O4). This phenomenon (Cr-corrosion) aggravates the Cr diffusion, causes a quick increase of ASR, and weakens the oxidation resistance. The adverse effects of Cr-corrosion can be alleviated by appropriately lowering the operating temperature. Among the coatings, Cu1.0Mn2.0O4 exhibited good electrical conductivity and soundness against the Cr-corrosion and can be considered a competitive candidate for SOFC applications.