Device for producing a block of crystalline material with modulation of the thermal conductivity
The device for producing a block of crystalline material from a bath of molten material comprises a crucible having a bottom and heat extraction means arranged under the crucible. It also comprises means for modulating the thermal conductivity fitted between the bottom of the crucible and the heat extraction means. The means for modulating the thermal conductivity comprise a plurality of plates made from thermally conducting material of low emissivity, parallel to the bottom of the crucible, and means for moving said plates closer to and away from one another.
1. A device for producing a block of crystalline material by solidifying a bath of molten material, the device comprising:
a crucible having a bottom;
a heat extractor arranged under the crucible, the heat extractor being movable relative to the crucible;
first and second plates made from thermally conducting material having an emissivity of less than 0.5, said first and said second plates being parallel to the bottom of the crucible and arranged between the bottom of the crucible and the heat extractor; and
a moving device configured to move said first and said second plates toward and away from one another and toward and away from the bottom of the crucible to modulate a thermal conductivity between the bottom of the crucible and the heat extractor during the solidifying of the bath of the molten material.
2. The device according to claim 1 , wherein the first and the second plates have a thermal conductibility greater than or equal to 10 W/m·K.
3. The device according to claim 1 , wherein the first and the second plates are made from a molybdenum-based material.
4. The device according to claim 1 , wherein one of the first and the second plates comprises:
a first portion with a first thickness; and
a second portion with a second thickness, the first and the second thicknesses being measured between first and second faces of each of the first and the second portions that are parallel to the bottom of the crucible, respectively.
5. The device according to claim 1 , wherein the crucible and the first and the second plates are disposed inside a chamber comprising at least a gas having a thermal conductivity greater than or equal to 0.01 W/m·K.
6. The device according to claim 5 , wherein the gas is helium or argon.
7. The device according to claim 1 , wherein the bottom of the crucible comprises a layer made of a material having an emissivity of less than 0.5.
8. The device according to claim 7 , wherein the material has a thermal conductivity greater than or equal to 10 W/m·K.
9. The device according to claim 1 , wherein the first and the second plates are provided with a protuberance made of thermally insulating material forming a spacer between the first and the second plates.
10. The device according to claim 1 , wherein the moving device comprises a control rod integral to the heat extractor, the moving device being configured to move the first and the second plates toward and away from one another and toward and away from the bottom of the crucible.
11. The device according to claim 1 , wherein a bottom of the crucible is leak proof.
12. The device according to claim 1 , wherein the moving device is configured to move the first and the second plates toward and away from the bottom of the heat extractor.
13. The device according to claim 1 , wherein the crucible is supported by a supporting element, the supporting element comprising a first end of travel stop for the first plate and a second end of travel stop for the second plate.
14. The device according to claim 1 , wherein
a third plate made from a thermally conducting material having an emissivity of less than 0.5 and parallel to the bottom of the crucible, and
the third plate being arranged between a bottom of the first and the second plates and the heat extractor, the second plate separating the first plate from the third plate.
15. The device according to claim 1 , wherein the moving device is configured to move the first and the second plates from a first position where the first and the second plates are separated from the heat exchanger and from the crucible to a second position.
16. The device according to claim 15 , wherein the first and the second plates are connected to the heat exchanger and to the crucible in the second position.
17. The device according to claim 14 , comprising
a first spring with a first stiffness connecting the first plate to the second plate; and
a second spring with a second stiffness connecting the second plate to the third plate, the second stiffness being greater than the first stiffness.