Glass-ceramic seals for use in solid oxide fuel cells

The invention is directed to a glass-ceramic seal, said seal comprising a boron-free, zinc-free glass-ceramic. The seals have a coefficient of thermal expansion in the range of 70-130 x 10 -7 °C, preferably 85-115 x 10- 7 °C. The glass-ceramic materials have a crystalline component and a glass component, the crystalline component being >50% of the glass-ceramic and the glass component being 50% of the crystals in the crystalline component of the glass-ceramic has a structure selected from the structural groups represented by kalsilite, kaliophilite and wollastonite (the primary crystalline phase) and the remaining