Use of an “Open” Triple-Phase Boundary to Demonstrate Where Chromium Contaminants Initially Deposit at the LSM-YSZ Interface

Abstract

Through the design of a densified (La 0.8 Sr 0.2 ) 0.98 MnO 3 (LSM) embedded 8% YSZ ceramic wafer with a well defined, readily observable triple-phase boundary (TPB), we have demonstrated that (Cr,Mn) 3 O 4 spinel crystals grow preferentially on the YSZ side of the TPB during cathodic polarization of a half-cell at 800°C in the presence of a chromia-forming stainless steel electrical contact. In all examples studied, chromium species transfer to the TPB region is seen well before any observable degradation of the half-cell performance. Because solid Cr 2 O 3 was not observed at or near the TPB, it is believed that the open design allows rapidly equilibration of deposited Cr 2 O 3 with the gaseous Cr species, while the more stable spinel phases remain at the interface. The results presented here show that, if the TPB region is not blocked by solid species, little if any effects due to chromium poisoning are observed.