Effect of High-Temperature Exposure on Degradation of La_0.6Sr_0.4CoO₃ Coated Metallic Interconnects for ITSOFC and SOEC

Abstract

Previous studies showed the formation of new phases affecting the electrical properties of LSC thin films deposited on stainless steel substrates, which are commonly tested for ITSOFC and SOEC interconnects. A 4.3 μm thick La_0.6Sr_0.4CoO₃ coating was deposited on AISI430 steel by spray pyrolysis, followed by heat treatment (800°C/2h) and an oxidation in air (800°C/96h). The La_0.6Sr_0.4CoO₃ phase interacted with the metallic substrate and formed SrCrO₄, causing degradation of the perovskite into La_0.9Sr_0.1CoO₃. An EDS mapping showed Sr and Cr enrichment in the coating/substrate interface. TG analysis indicated a lower mass gain for the coated substrate. The total ASR at 800°C of the interconnect before and after oxidation was 3.23 Ω.cm² and 3.98 Ω.cm², respectively. The Ea underwent very small variation, remaining around 0.24 eV (T≤300°C) and 0.65 eV (T≥400°C). The reaction of Cr from the substrate and Sr from LSC seems to have impaired the performance of the interconnect.

Keywords:
steel intreconnect; coating; lanthanum cobaltite; impedance spectroscopy