Strontium transport and conductivity of Mn1.5Co1.5O4 coated Haynes 230 and Crofer 22 APU under simulated solid oxide fuel cell condition

Interaction of current collectors with coated interconnect alloys was examined using dual-coating specimens. Oxidation kinetics of (La,Sr)(Co,Fe)O3 (LSCF)/Mn1.5Co1.5O4 (MCO) and (La,Sr)(Mn)O3 (LSM)/MCO coated Haynes 230 (H230) was determined at 750 °C in air via a gravimetric method. The LSCF/MCO dual coating samples exhibited a rate constant 2 times larger than that of the LSM/MCO coated H230. SrCrO4 that formed at the LSCF/MCO coated H230 interface contributed to the increased rate constant. No SrCrO4 was detected at the interface of the LSM/MCO coated H230. Chemical stability of LSCF in air at 750 °C was confirmed by TGA. Area specific resistance (ASR) of MCO coated Haynes 230 (H230) and Crofer 22 APU with LSCF and LSM (coated H230 only) current collectors was measured at 800 °C for 1100 h. No gross difference in ASR evolution was observed between the LSCF/MCO-H230 and LSM/MCO-H230 assemblies. Activation energy of conduction of the LSCF/MCO-H230 and LSCF/MCO-Crofer 22 samples evolved from 0.63 eV to 0.80 eV and from 0.53 eV to 0.63 eV respectively over a period of ca. 1100 h, suggesting somewhat different interface chemistry evolution. Sr transport was observed in the LSCF/MCO-H230 samples subjected to both exposure test and ASR measurement, whereas it was not detected on the LSCF/MCO-Crofer 22 sample. Mechanism of the Sr transport is discussed on a qualitative basis to account for the observations.

► Sr transport observed in Mn1.5Co1.5O4 coated Haynes 230 but not in coated Crofer22. ► Negligible impact of SrCrO4 on the conductivity of coated H230 observed. ► Interface chemistry of coated H230 evolved differently for that of coated Crofer22.