PNNL

Abstract

Planar solid oxide fuel cells (SOFC) require sealants to function properly in harsh environments at elevated temperatures. The SOFC stacks are expected to experience multiple thermal cycles (perhaps thousands of cycles for some applications) during their life time service in stationary or transportation applications. As a result, thermal cycle stability is considered a top priority for SOFC sealant development. In previous work, we have developed a hybrid mica-based compressive seal with very low leak rates of 2-4x10-2 to 10-3 sccm/cm at 800oC, and showed stable leak rates over limited thermal cycles In this paper we present results of long-term thermal cycle testing (> 1000 thermal cycles) of Phlogopite mica-based compressive seals. Open circuit voltage (OCV) was measured on a 2”x2” 8-YSZ plate with the hybrid Phlogopite mica seals during thermal cycling in a dual environment (2.75% H2/Ar vs. air). During two long-term cycling tests, the measured OCVs were found to be consistent with the calculated Nernst voltages. The hybrid mica seal showed excellent thermal cycle stability over 1000 thermal cycles and can be considered a strong candidate for SOFC applications.