Patent ID: 8592041

Claim:
A glass ceramic composition comprising: at least 55 weight % of a first ceramic comprising forsterite as the main constituent, a second ceramic comprising at least one of strontium titanate and titanium oxide as the main constituent, a third ceramic comprising barium zirconate as the main constituent, a fourth ceramic comprising zirconium oxide or manganese oxide as the main constituent, and a borosilicate glass, wherein the first ceramic is the main constituent of the composition, the content of said second ceramic is 3 weight % to 13 weight % when the second ceramic has strontium titanate as the main constituent, and is 0.3 weight % to 10 weight % when the second ceramic has titanium oxide as the main constituent, the content of said third ceramic is 4 weight % to 8 weight %, the content of said fourth ceramic is 5 weight % to 20 weight % when the fourth ceramic has zirconium oxide as the main constituent, and is 1 weight % to 9 weight % when the fourth ceramic has manganese oxide as the main constituent, the content of said borosilicate glass is 3 weight % to 15 weight %, and wherein said borosilicate glass contains lithium in an amount of 4 to 10 weight % on a Li 2 O equivalent basis, magnesium in an amount of 30 to 45 weight % on a MgO equivalent basis, boron in an amount of 15 to 25 weight % on a B 2 O 3 equivalent basis, silicon in an amount of 15 to 30 weight % on a SiO 2 equivalent basis and zinc in an amount of 6 to 20 weight % on a ZnO equivalent basis, up to 15 weight % Al on an Al 2 O 3 equivalent basis, and further contains at least 2 weight percent on a CaO equivalent basis plus SrO equivalent basis of an additive constituent comprising at least one of calcium oxide and strontium oxide, wherein the upper limit of the content of said additive constituent is 15 weight % on a CaO equivalent basis in the case of calcium oxide and is 25 weight % on a SrO equivalent basis in the case of strontium oxide based on the total weight of the borosilicate glass.