Interfacial study between high temperature SiO₂-B ₂O₃-AO-La₂O₃ (A = Sr, Ba) glass seals and Crofer 22APU for solid oxide fuel cell applications

In the present work, the adhesion and chemical compatibility of two glass compositions are investigated with interconnect Crofer 22APU as a function of different heating durations for solid oxide fuel cell applications. Initially, the selected glasses have been characterized using differential thermal analyzer and dilatometer to check their suitability as a sealing material. After that, Crofer 22APU/glass-ceramics are joined to make diffusion couples. Furthermore, these diffusion couples have been heat-treated at 850 °C for different time durations of 5, 100 and 750 h and morphologically characterized. X-ray diffraction (XRD) indicates surface crystallization of various crystalline phases formed in the glass/Crofer 22APU diffusion couple. Coefficient of thermal expansion (CTE) of both the glasses is in good agreement with the CTE of Crofer 22APU. The overall analysis of resulting microstructure by scanning electron microscopy (SEM)/electron probe microanalysis (EPMA) revealed improvement in adhesion with increase in time duration of heat-treatment. Both the sealants have not shown delamination with Crofer 22APU interface even after prolonged duration of heat-treatment. The absence of unwanted oxide products in all the diffusion couples further confirms high gas tightedness and hermeticity of seals with low embrittlement.