Method for producing a component of rare earth metal-doped quartz glass

Patent metadata

Field	Value
Publication number	US-10851008-B2
Application number	US-201815938156-A
Country	US
Kind code	B2
Filing date	Mar 28, 2018
Priority date	Mar 30, 2017
Publication date	Dec 1, 2020
Grant date	Dec 1, 2020

Abstract

A method for producing a component with portions of a rare earth metal-doped quartz glass, an intermediate product containing voids and consisting of a SiO 2 raw material doped with rare earth metal is introduced into a sinter mold the interior of which is bordered by a carbonaceous mold wall, and is melted therein into the component by gas pressure sintering at a maximum temperature above 1500° C. A shield is arranged between the mold wall and the intermediate product. In order to indicate a modified gas pressure sintering method that ensures the production of rare earth metal-doped quartz glass with reproducible properties, a bulk material of amorphous SiO 2 particles with a layer thickness of at least 2 mm is used as the shield, the softening temperature thereof being at least 20° C. higher than the softening temperature of the doped SiO 2 raw material, and the bulk material being gas-permeable at the beginning of the melting of the intermediate product, and the bulk material sintering during melting into an outer layer that is gas-tight to a pressure gas.

First claim

What is claimed is:

1. A method of producing a component that consists at least in portions of a rare earth metal-doped quartz glass, the method comprising:
(a) providing an intermediate product containing voids and consisting of a SiO 2 raw material doped with rare earth metal;
(b) introducing the intermediate product into a sinter mold with an interior bordered by a carbonaceous mold wall; and
(c) melting the intermediate product into the component by gas pressure sintering at a maximum temperature above 1500° C., a shield being arranged between the mold wall and the intermediate product,

characterized in that a bulk material of amorphous SiO 2 particles with a layer thickness of at least 2 mm is used as the shield, the softening temperature thereof being at least 20° C. higher than the softening temperature of the doped SiO 2 raw material, and the bulk material being gas-permeable at the beginning of the melting of the intermediate product according to the method step, the bulk material sintering during melting into an outer layer that is gas-tight to a pressure gas, and the bulk material has a gas permeability which is defined by a Darcy coefficient between 0.8×10 −11 m 2 and 3×10 −11 m 2 .

2. The method according to claim 1 , characterized in that the bulk material has a bulk density in the range of 0.75 g/cm 3 to 1.3 g/cm 3 .

3. The method according to claim 1 , characterized in that the SiO 2 particles have a mean particle size in the range of 150 μm to 300 μm (D 50 value).

4. The method according to claim 1 , characterized in that the gas pressure sintering according to method step (c) takes place at a maximum temperature above 1600° C.

5. The method according to claim 1 , characterized in that the softening temperature of the SiO 2 bulk material is higher by at least 50° C., but not more than 200° C., than the softening temperature of the doped SiO 2 raw material.

6. The method according to claim 1 , characterized in that the SiO 2 particles have a BET surface area of less than 2 m 2 /g.

7. The method according to claim 6 , characterized in that the SiO 2 particles have a BET surface area of less than 1 m 2 /g and that they have no open porosity.

8. The method according to claim 1 , characterized in that the bulk material has a gas permeability which is defined by a Darcy coefficient between 0.8×10 −11 m 2 and 1.3×10 −11 m 2 .

9. The method according to claim 1 , characterized in that the bulk material has an initial effective porosity in the range of 40% to 50%.

10. The method according to claim 1 , characterized in that the SiO 2 particles consist of quartz glass with a SiO 2 content of at least 99.9%, the viscosity of which is at least 10 12.5 dPa·s at a temperature of 1200° C.

11. The method according to claim 1 , characterized in that the SiO 2 particles have a total content of impurities Fe, Cu, Cr and Ti of less than 1000 wt. ppb.

12. The method according to claim 11 , characterized in that the SiO 2 particles have a total content of impurities Fe, Cu, Cr and Ti of less than 200 wt. ppb.

13. The method according to claim 1 , characterized in that the gas-permeable bulk material surrounds the intermediate product as a layer with a mean layer thickness of at least 5 mm.

14. The method according to claim 1 , characterized in that during melting of the intermediate product the shield is vitrified into a cladding material, and that after completion of the gas pressure treatment the cladding material is removed.

15. A method of producing a component that consists at least in portions of a rare earth metal-doped quartz glass, the method comprising:
(a) providing an intermediate product containing voids and consisting of a SiO 2 raw material doped with rare earth metal;
(b) introducing the intermediate product into a sinter mold with an interior bordered by a carbonaceous mold wall; and
(c) melting the intermediate product into the component by gas pressure sintering at a maximum temperature above 1500° C., a shield being arranged between the mold wall and the intermediate product,

characterized in that a bulk material of amorphous SiO 2 particles with a layer thickness of at least 2 mm is used as the shield, the softening temperature thereof being at least 20° C. higher than the softening temperature of the doped SiO 2 raw material, and the bulk material being gas-permeable at the beginning of the melting of the intermediate product according to the method step, and the bulk material sintering during melting into an outer layer that is gas-tight to a pressure gas, characterized in that the bulk material has a gas permeability which is defined by a Darcy coefficient in the range of 1.6×10 −11 m 2 to 3×10 −11 m 2 , and that the bulk material has a grain size distribution which is characterized by a D 10 value between 150 and 250 μm and by a D 90 value between 350 and 450 μm.

16. A method of producing a component that consists at least in portions of a rare earth metal-doped quartz glass, the method comprising:
(a) providing an intermediate product containing voids and consisting of a SiO 2 raw material doped with rare earth metal;
(b) introducing the intermediate product into a sinter mold with an interior bordered by a carbonaceous mold wall; and
(c) melting the intermediate product into the component by gas pressure sintering at a maximum temperature above 1500° C., a shield being arranged between the mold wall and the intermediate product,

characterized in that a bulk material of amorphous SiO 2 particles with a layer thickness of at least 2 mm is used as the shield, the softening temperature thereof being at least 20° C. higher than the softening temperature of the doped SiO 2 raw material, and the bulk material being gas-permeable at the beginning of the melting of the intermediate product according to the method step, the bulk material sintering during melting into an outer layer that is gas-tight to a pressure gas, characterized in that gas pressure sintering comprises:
(a) a pretreatment which comprises a heating up of the intermediate product to a temperature in the range between 1000° C. and 1300° C. with application and maintenance of a negative pressure,
(b) melting the intermediate product at a temperature above 1500° C. at a negative pressure and for a melting period of at least 30 min, wherein the bulk material sinters into the gas-impermeable outer layer, and
(c) a pressure treatment of the molten intermediate product at a temperature above 1500° C. in an inert gas atmosphere under an overpressure in the range between 2 bar and 20 bar for a period of at least 30 min.

17. The method according to claim 16 , characterized in that the intermediate product is temporarily exposed to an atmosphere which contains helium and/or hydrogen in a concentration of at least 50% by vol.

Assignees

• Heraeus Quarzglas

Inventors

• Lehmann Walter
• Such Mario
• Kayser Thomas
• Langner Andreas
• Schötz Gerhard

Classifications

• C03B2201/36

  doped with rare earth metals and aluminium, e.g. Er-Al co-doped · CPC title

• C03B19/14

  by gas- {or vapour-} phase reaction processes · CPC title

• C03B2215/66

  Means for providing special atmospheres, e.g. reduced pressure, inert gas, reducing gas, clean room · CPC title

• C03B2201/34

  doped with rare earth metals, i.e. with Sc, Y or lanthanides, e.g. for laser-amplifiers · CPC title

• C03B19/066 Primary

  for the production of quartz or fused silica articles (other processes specially adapted for the production of quartz or fused silica articles C03B20/00) · CPC title