Quartz glass component of high thermal stability, semifinished product therefor, and method for producing the same
In a known method for producing a quartz glass component, a crystal formation layer containing a crystallization promoter is produced on a coating surface of a base body of quartz glass. Starting therefrom, to provide a method for producing a quartz glass component of improved thermal strength and long-term stability which displays a comparatively small deformation particularly also in the case of rapid heating-up processes, it is suggested according to one aspect that a porous crystal formation layer containing amorphous SiO 2 particles is produced with a mean thickness in the range of 0.1 to 5 mm, and that a substance which contains cesium and/or rubidium is used as the crystallization promoter.
1. A method for producing a quartz glass component, with a crystal formation layer containing a crystallization promoter being produced on a coating surface of a base body of quartz glass, comprising:
producing a porous cristobalite crystal formation layer containing amorphous SiO 2 particles with a mean thickness in the range of 0.1 to 5 mm;
wherein the crystallization promoter is a substance that contains cesium and/or rubidium; and
wherein the amount of the crystallization promoter substance in the porous crystal formation layer is at least 0.025 mole % and not more than 0.5 mole %.
2. The method of claim 1 , wherein the crystallization promoter substance has a melting temperature below 1150° C.
3. The method of claim 1 , wherein the crystallization promoter substance has a melting temperature below 1100° C.
4. The method of claim 1 , wherein the porous cristobalite crystal formation layer is produced with a mean thickness in the range of 0.5 to 3 mm.
5. The method of claim 1 , wherein amorphous SiO 2 particles produced by comminuting quartz glass make up the greatest volume proportion of the crystal formation layer.
6. The method of claim 1 , wherein the production of the porous cristobalite crystal formation layer comprises:
applying a dispersion which contains the amorphous SiO 2 particles in a liquid, as a slurry layer to the coating surface; and
drying the slurry layer while forming a green layer.
7. The method of claim 6 , wherein the crystallization promoter or a precursor substance thereof is contained in the dispersion in dissolved form.
8. The method of claim 6 , wherein the green layer has a green density of at least 1.7 g/cm 3 .
9. The method of claim 6 , wherein the green layer is thermally densified at a temperature in the range of 670° C. to 1000° C.
10. The method of claim 1 , wherein the porous cristobalite crystal formation layer is heated to a temperature of less than 1250° C. and that the formation of cristobalite sets in during heating of the layer.
11. The method of claim 1 , wherein the porous cristobalite crystal formation layer is heated to a temperature of less than 1150° C. and that the formation of cristobalite sets in during heating of the layer.