Patent ID: 7417001

Claim:
A glass ceramic composition comprising: about 55 percent by weight or more of a first ceramic powder mainly composed of forsterite; about 6 to 30 percent by weight of a second ceramic powder containing at least one ceramic powder selected from the group consisting of a ceramic powder mainly composed of calcium titanate, a ceramic powder mainly composed of strontium titanate, and a ceramic powder mainly composed of titanium oxide; about 3 to 20 percent by weight or more of a borosilicate glass powder containing about 3 to 15 percent by weight of lithium calculated as Li 2 O, about 20 to 50 percent by weight of magnesium calculated as MgO, about 15 to 30 percent by weight of boron calculated as B 2 O 3 , about 10 to 45 percent by weight of silicon calculated as SiO 2 , about 6 to 20 percent by weight of zinc calculated as ZnO, and 0 to about 15 percent by weight of aluminum calculated as Al 2 O 3 , and a positive amount up to about 1 part by weight of silicon calculated as SiO 2 relative to 100 parts by weight of the total amount of the first ceramic powder, the second ceramic powder and the borosilicate glass powder; wherein the borosilicate glass powder contains at least about 2 percent by weight of an additive selected from the group consisting of calcium oxide, barium oxide, strontium oxide and mixtures thereof, calculated as CaO, BaO and SrO, respectively, and wherein the upper limit of the calcium oxide content of the borosilicate glass powder is about 15 percent by weight, the upper limit of the barium oxide content of the borosilicate glass powder is about 25 percent by weight and the upper limit of the strontium oxide content of the borosilicate glass powder is about 25 percent by weight.