| Summary: | Solid oxide fuel cells (SOFCs) are promising devices for electrical power generation from hydrogen or hydrocarbon fuels. The paper reports our study of CaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> material with composition 36 mol.% SiO<sub>2</sub>, 26 mol.% B<sub>2</sub>O<sub>3</sub>, and 38 mol.% CaO as a high-temperature sealant for SOFCs with an operating temperature of 850 °C. The material was studied as an alternative to presently existing commercial glass and glass-ceramics sealants for SOFCs with operating temperature of 850 °C. Many of these sealants have limited adhesion to the surface of Crofer 22APU steel, commonly used in these SOFCs. The present study included X-ray diffraction, dilatometric, thermal, and microstructural analysis The study has shown that the softening point of the CaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> glass is around 900 °C, allowing sealing of the SOFCs with this glass at convenient temperature of 925 °C. The CaO-SiO<sub>2</sub>-B<sub>2</sub>O<sub>3</sub> glass sealant has shown excellent adhesion to the surface of Crofer 22APU steel; SEM images demonstrated evidences of chemical reaction and formation of strong interface on sealant–steel contact surface. Furthermore, the glass has shown a coefficient of thermal expansion about 8.4 × 10<sup>−6</sup> 1/K after sealing, making it thermomechanically compatible with the existing SOFC materials.
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