The invention is directed to highly crystalline, frit-sintered glass-ceramic materials and seals made using them that are suitable for solid oxide fuel cell applications. The seals have a coefficient of thermal expansion in the range of 70-130×10−7° C., preferably 85-115×10−7° 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 75%. Regarding the crystalline component only, >50% of the crystals in the crystalline component of the glass-ceramic has a structure selected from the structural groups represented by walstromite, cyclowollastonite, μ-(Ca,Sr)SiO3, kalsilite, kaliophilite and wollastonite (the primary crystalline phase) and the remaining