A glass-ceramic composition was designed and tested for use as a sealant in solid oxide fuel cell (SOFC) planar stack design. The crystallization behaviour was investigated by calculating the Avrami parameter (n) and the activation energy for crystallization (E-c) was obtained. The calculated values for n and Ec were 3 and 413.5 kj/mol respectively. The results of thermal analyses indicate that this composition shows no overlap between the sintering and crystallization stages and thus an almost pore-free sealant can be deposited and sintered at 850 degrees C in air for 30 min. A gas tightness test has been carried out at 800 degrees C for 1100 h in dual atmosphere (Ar-H-2 and air) without recording any leakage. Morphological and crystalline phase analyses were conducted prior and following tests in dual atmospheres in order to assess the compatibility of the proposed sealant with the metallic interconnect

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This work deals with the design, the characterization, and testing of a novel glass-ceramic to be used as sealant for planar solid oxide fuel cells and its compatibility with Mn1.5Co1.5O4-coated Crofer22APU. Thermal, sintering, and crystallization behavior and thermo mechanical properties of the sealant are reviewed and discussed, indicating therefore that these compositions can be deposited at 850C and provide an excellent compatibility with both the Mn1.5Co1.5O4-coated Crofer22APU and the anode-supported electrolyte. In particular, Mn1.5Co1.5O4-coated Crofer22APU/sealant/anode-supported-electrolyte joined samples have been submitted to thermal tests (in air atmosphere) from RT to 800C (SOFC operating temperature) up to 500 h. No interactions, cracks formation, or failure were observed at the Mn1.5Co1.5O4-coated Crofer22APU/sealant interface and between the glass-ceramic and the anode-supported-electrolyte after 500 h of thermal tests in air atmosphere

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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In this work, three new glass-ceramic compositions are designed and characterized as sealant materials for solid oxide electrolysis cells (SOEC), having operating temperature of 850°C. The crystallization and the sintering behavior of the glasses are investigated by using differential thermal analysis (DTA) and heating stage microscopy (HSM) respectively. The glasses show glass transition temperatures of 715-740°C, while the coefficients of thermal expansion (CTE) of 9.3-10.3 9 10 À6 K À1 (200-500°C) are measured for the glass-ceramics, matching with the CTEs of the other cell components. The compatibility between the glassceramic sealants, the 3YSZ electrolyte and the Crofer22APU interconnect is examined by means of SEM and EDS, in the as-joined condition and after 1000 hours at 850°C in air. Compositional changes in the glass-ceramic sealants are reviewed and discussed with respect to the formed crystalline phases before and after the aging treatment at 850°C. K E Y W O R D S crystals/crystallization, Interfaces, SOEC, thermal expansion ---

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