In solid oxide fuel cell (SOFC) stacks the sealing is a critical element which has to ensure gas tightness between different gas streams as well as electrical insulation in several parts of the system depending on its design. It has therefore to establish stable interfaces with different materials such as the ferritic stainless steel (FSS) used for interconnects frame or gas manifolds and the ceramic materials of the cell electrolytes. Therefore, sealants have to be chemically and mechanically stable in contact with such materials at the SOFC working conditions in terms of temperatures, thermal and stress gradients, and exposition to different gas compositions.

Glasses are widely used as sealing material because of their thermal expansion characteristics, mechanical properties, the possibility to obtain gas tight structures and ease of application. However, due to the operating temperatures, reactions and diffusion processes can occur at the interfaces resulting in the formation of undesirable phases that could compromise the glass properties increasing the risk of failures. The application of a barrier layer between the two components is considered as suitable countermeasure avoiding the migration of elements at the interfaces. In this work the barrier properties and compatibility at the interfaces of Yttria-stabilized zirconia (YSZ) has been investigated. YSZ layers have been applied by means of plasma spraying on as-rolled FSS substrates. Several glass compositions, applied on substrates with and without YSZ coating, have been tested at 780°C in static air up to 1000 h to investigate the barrier layer effects, the compatibility of the materials and the stability of the interfaces. Microstructural changes and migration of elements have been characterized post-experiment in cross-section by means of scanning electron microscopy- energy dispersive X-ray analysis.