Patent ID: 7470640

Claim:
A glass-ceramic seal composition, said seal composition comprising a glass-ceramic having a glass component and a crystalline component, wherein: said glass-ceramic comprises 30-50 wt. % SiO 2 , 2-8 wt. % Al 2 O 3 , 10-40 wt. % CaO, and at least one of 0-40 wt. % SrO, 0-35 wt. % BaO, 0-10 wt. % MgO; said glass-ceramic is boron free; the crystalline component of said glass-ceramic is >50% and the glass component is <50% of the glass-ceramic seal; referring only to the crystalline component, >50 wt. % of the crystalline component comprises a primary crystalline phase in which the crystals of the crystalline phase have a structure selected from the structures represented by the group consisting of walstromite, cyclowollastonite, and μ-(Ca,Sr)SiO 3 ), kalsilite, kaliophilite and wollastonite, and the remaining <50% of the crystalline component comprises at least one secondary crystalline phase; the primary crystalline phase is >50% of the crystalline component; and the glass ceramic has a CTE in the range 70-130×10 −7 /° C.