Molded body of quartz glass and process for the production of a molded body of quartz glass

Process for the production of a molded body of quartz glass with at least one surface region of transparent quartz glass, the exposed surface of which is smooth, with a microroughness of less than 8 .mu.m, comprising the steps of producing a base by the slip casting method, where quartz glass of a purity of at least 99.9% is ground into a powder with a particle size of less than 70 .mu.m;

• forming a slip from the powder and stabilizing the slip over the course of 1-240 hours by keeping it in continuous motion;
• loading the stabilized slip into a porous mold corresponding to the base, where it is allowed to remain for a predetermined period of time;
• after removal from the mold, drying the base blank and heating it in a furnace at a heating rate of 5-60 K/min to a sintering temperature in the range of 1,350.degree.-1,450.degree. C. and then exposing the blank to a temperature of more than 1,300.degree. C. for a period of at least 40 minutes;
• cooling the sintered base and then heating a surface region of the opaque, porous, gas-impermeable base material forming the base locally by means of a heat source to a temperature in the range of 1,650.degree.-2,000.degree. C. to transform the porous, opaque base material into transparent quartz glass until the thickness of the transparent surface region is at least 0.5 mm and its direct spectral transmission in the wavelength range of .lambda.=600 nm to .lambda.=2,650 nm has a value of at least 60% for a layer thickness of 1 mm.