A new glass-ceramic composition containing Si, Mg, Ca, Na, Al, Zr, and B is presented here as sealant for planar SOFCs/SOECs, with the aim of joining the metallic interconnect (Crofer22APU) to the solid oxide cell (YSZ electrolyte or CGO barrier layer). Characteristic temperature, thermo-mechanical properties, and compositional variations are reviewed and discussed by thermal analyses and in situ XRD, in order to design and optimize the sealing profile and reduce the residual porosity. The glass after heat treatment partially devitrifies into augite and nepheline with residual glass phase of around 64.3%; after crystallization the glass-ceramic sealant has a coefficient of thermal expansion of 12.8 9 10 À6 K À1 and it is compliant with the other materials typically used for stack components.This work shows that the developed glass-ceramic can successfully join the ceramic cell with the Crofer22APU (preoxidized and alumina coating), proven by tests on small and large-scale samples. No signs of unwanted reactions at the glass-metal and the glass-cell interface are observed and sufficient gas tightness is achieved. K E Y W O R D Sglass-ceramics, solid oxide fuel cell, synthesis, thermal analysis

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I.; Khajavi, P.; Talic, B.; Kiebach, R.; Hendriksen, P. V. AbstractFor long-term durability and robustness to withstand thermal cycles, the planar solid oxide cell (SOC) stack technologies are challenged by the use of brittle components. With the current trend of increasing the footprint of the SOC stacks, even larger thermal gradients and thermal stresses can be expected. In this overview paper, we present recent advances from our group on improving the fracture energy of three critical materials/interfaces. The fracture energy of the fuel electrode support is increased by ~50 % by tailoring composition and further optimizing the phase transformation toughening. The fracture energy of the air-side contact layer is increased by a factor of ~10 by using metallic pre-cursors that are transformed to spinels through in-situ reactive oxidative bonding. Finally, the fracture energy of the seal-interconnect interface is improved by a factor of 5 by combining an optimized sealing glass with aluminum based coatings for the interconnect.