Alkali free glass-ceramics as sealing material for high temperature applications

摘要

The present invention relates to the use of an alkali-free oxide mixture comprising at least the following components: (a) silicon dioxide in a molar fraction of 35 to 55%, (b) magnesium oxide in a molar fraction of 20 to 50% and, (c) at least one oxide, selected from calcium oxide, strontium oxide and barium oxide, with the proviso that the mole fraction of calcium oxide, strontium oxide and barium oxide together is at least 5% and the mole fraction of each of these three oxides does not exceed 15%, as a glass-ceramic joining material with a coefficient of thermal expansion of = 10 10 -6 K -1 for use at high temperatures, or for the production of such a joining material. The oxide mixture can additionally contain one or more oxides selected from the group B2O3, Al2O3, La2O3, Y2O3 ZnO, TiO2 ZrO2 FeO and Fe2O3. A glass is melted from the crystalline or amorphous components, which is exposed to a temperature profile which first causes a widening and then the crystallization of material.