GLASS CERAMICS AND PRODUCTION THEREOF

PURPOSE:To improve machinability with a low thermal expansion coefficient and a small quantity of an adsorbed and a desorbed gas by including fluorphlogopite crystallites and Li2O-Al2O3-SiO2-based crystallites in a glass matrix. CONSTITUTION:Alkoxide compounds and fluorine compounds of various metallic components are dissolved in a polar solvent so as to provide 30-70wt.% SiO2 component, 10-25wt.% Al2O3 component, 7-25wt.% MgO component, 2-12wt.% K2O component, 1-7wt.% Li2O component and 1-15wt.% F component. A B2O3 component in an amount of 1-10wt.% is then added to the resultant solution and water is further added to hydrolyze the compounds. The prepared hydrolyzate is subsequently dried at 25-130 deg.C and heat-treated at 500-1050 deg.C to afford the objective glass ceramics, containing 10-60wt.% fluorphlogopite crystallites and 10-50wt.% Li2O-Al2O3-SiO2-based crystallites in the glass matrix and having 4.0X10 to 6.0X10/ deg.C thermal expansion coefficient (25-280 deg.C) and 1X10 to 10X10atm.cc/see quantity of adsorbed and desorbed He.