System and method for vapor pressure controlled growth of infrared chalcogenide glasses
View Patent ↗A system and method for preparing chalcogenide glass are provided that allow for larger quantities of glass to be produced with lower production costs and less risks of environmental hazards. The system includes a reaction container operable to hold chalcogenide glass constituents during a glass formation reaction, a stirring rod operable to mix the contents of the reaction container, a thermocouple operable to measure the temperature inside the reaction container, and a reaction chamber operable to hold the reaction container. The method includes placing chalcogenide glass constituents in a reaction container, heating the chalcogenide glass constituents above the melting point of at least one of the constituents, promoting dissolving or reaction of the other constituents, stirring the reaction melt, maintaining an overpressure of at least one atmosphere over the reaction melt, and cooling the reaction melt to below the chalcogenide glass transition temperature.
1. A method for preparing chalcogenide glass, comprising:
placing a plurality of constituents of a chalcogenide glass in a reaction container, wherein each constituent has a respective melting point, boiling point, density, and vapor pressure, and wherein the chalcogenide glass has a glass transition temperature;
heating the constituents above the melting point of at least one of the plurality of constituents to form a reaction melt;
stirring the reaction melt;
maintaining an overpressure of at least one atmosphere over the reaction melt; and
cooling the reaction melt to below the glass transition temperature of the chalcogenide glass.
2. The method of claim 1 , wherein the constituents are selected from the group consisting of selenium, germanium, antimony, and tin.
3. The method of claim 1 , further comprising maintaining a pressure that is higher than the vapor pressure of the constituent having the highest vapor pressure at a current process temperature.
4. The method of claim 1 , further comprising introducing one or more inert gases into the reaction container in a quantity sufficient to maintain the overpressure.
5. The method of claim 4 , wherein the inert gas is selected from the group consisting of nitrogen, helium, or argon.
6. The method of claim 1 , further comprising introducing a non-reactive material into the reaction container to at least partially control mass transfer of the constituents out of the reaction melt; wherein a melting point of the non-reactive material is less than each of the respective boiling points of the constituents; and wherein a density of the non-reactive material is less than each of the respective densities of the constituents.
7. The method of claim 6 , wherein the non-reactive material includes boron oxide (B 2 O 3 ).
8. The method of claim 1 , further comprising disposing a quartz plate, or other non-reactive material above the reaction melt to control mass transfer, of the constituent having the lowest boiling point, out of the reaction melt.
9. The method of claim 1 , further comprising placing the reaction container within an externally heated, hot-wall reaction chamber.
10. The method of claim 9 , wherein the reaction chamber includes a nickel-chromium-iron alloy liner.
11. The method of claim 10 , wherein the nickel-chromium-iron alloy liner includes Inconel®.
12. The method of claim 9 , wherein heating the constituents comprises providing heat to the reaction chamber.
13. The method of claim 12 , further comprising:
monitoring a temperature of the reaction melt; and
adjusting the heat supplied to the reaction chamber according to the temperature of the reaction melt.
14. The method of claim 13 , wherein adjusting the heat supplied to the reaction chamber includes adjusting power supplied to an external heater operable to heat the reaction chamber.
15. The method of claim 12 , further comprising:
monitoring exothermic heats of reaction given off by the reaction melt; and
adjusting the heat supplied to the reaction chamber according to the monitored exothermic heats of reaction.
16. The method of claim 15 , wherein adjusting the heat supplied to the reaction chamber includes adjusting power supplied to an external heater operable to heat the reaction chamber.
17. The method of claim 1 , wherein stirring the reaction melt includes mechanically rotating a stirring rod positioned at least partially within the reaction melt; and
wherein the stirring rod is rotated at a stirring rate.
18. The method of claim 17 , further comprising:
monitoring a temperature of the reaction melt; and
adjusting the stirring rate of the stirring rod to minimize rapid temperature rises.
19. The method of claim 17 , further comprising:
monitoring a torque applied to the stirring rod; and
adjusting the stirring rate of the stirring rod in response to the torque detected.
20. The method of claim 1 , further comprising:
monitoring a temperature of the reaction melt;
detecting temperature spikes by calculating time derivatives of the temperature of the reaction melt; and
adjusting the temperature of the reaction melt in response to the temperature spikes.
21. The method of claim 1 , further comprising providing constituents having large volume to surface area ratios in order to present a relatively small reaction interface.
22. The method of claim 1 , wherein the reaction container comprises a quartz container being disposed within a closed, pressurized, externally heated, hot-wall reaction chamber.