Method for manipulating a rare earth chloride or bromide or iodide in a crucible comprising carbon
The invention relates to the handling of a composition comprising a rare-earth halide, especially within the context of the growth of crystals from said composition, said crystals generally being of formula A e Ln f X (3f+e) in which Ln represents one or more rare earths, X represents one or more halogen atoms chosen from Cl, Br or I, and A represents one or more alkaline metals such as K, Li, Na, Rb or Cs, e and f representing values such that e, which may be zero, is less than or equal to 2f and f is greater than or equal to 1. It is possible in this way to grow single crystals exhibiting remarkable scintillation properties.
1. A method of handling a composition comprising placing a composition into contact with a material wherein said composition is in the molten state and said composition comprises at least 80% by weight of a rare-earth halide of formula A e Ln f X (3f+e) wherein Ln represents one or more rare earth elements, X represents one or more halogen atoms chosen from Cl, Br and I, and A represents one or more alkali metals chosen from K, Li, Na, Rb and Cs, e and f representing values such that:
e, which may be zero, is less than or equal to 2f,
f is greater than or equal to 1,
wherein said material comprises at least 20% carbon by weight, the surface of said material that is in contact with said composition comprises at least 20% carbon by weight and said composition in the molten state coming into contact with said material is at a temperature above 500° C.
2. The method as claimed in claim 1 , wherein the material forms part of a crucible.
3. The method as claimed in claim 2 , wherein the same crucible is used in the method at least five times, the crucible returning to ambient temperature between each time.
4. The method as claimed in claim 2 , wherein the same crucible is used in the method at least ten times, the crucible returning to ambient temperature between each time.
5. The method as claim 1 , wherein the material comprises graphite or amorphous carbon.
6. The method as claimed in claim 5 , wherein the material comprises a graphite substrate and a lining intended to come into contact with the composition comprising the rare-earth halide.
7. The method as claimed in claim 6 , wherein the lining is made of pyrolytic carbon.
8. The method as claimed in claim 6 , wherein the lining is made of silicon carbide.
9. The method as claimed in claim 5 , wherein the material is entirely made of graphite or of amorphous carbon.
10. The method as claimed in claim 1 , wherein contact takes place between 500° C. and 1000° C.
11. The method as claimed in claim 1 , wherein the composition comprises at least 10% by weight of at least one rare earth element.
12. The method as claimed in claim 1 , wherein the composition comprises at least 20% by weight of at least one rare earth element.
13. The method as claimed in claim 1 , wherein the handling is carried out under an oxygen/water partial pressure of less than 10 millibars.
14. The method as claimed in claim 1 , wherein the handling takes place within the context of the growth, from the composition, of a single crystal comprising the rare-earth halide.
15. The method as claimed in claim 14 , wherein the growth is carried out with a growth rate of less than 5 mm/h.
16. The method as claimed in claim 14 , wherein the growth is of the Bridgeman type.
17. The method as claimed in claim 14 , wherein the growth is of the Kyropoulos or Czochralski type.
18. The method as claimed in claim 14 , wherein the single crystal is of formula A e Ln f X (3f+e) in which Ln represents one or more rare earth elements, X represents one or more halogen atoms chosen from Cl, Br and I, and A represents one or more alkali metals chosen from K, Li, Na, Rb and Cs, e and f representing values such that:
e, which may be zero, is less than or equal to 2f,
f is greater than or equal to 1.
19. The method as claimed in claim 18 , wherein the single crystal is of formula ALn 2 X 7 in which Ln represents one or more rare earth elements and X represents one or more halogen atoms, chosen from Cl, Br and I, A representing Rb or Cs.
20. The method as claimed in claim 18 , wherein the composition comprises LaCl 3 and/or LaBr 3 and/or GdBr 3 and/or La x Gd (1-x) Br 3 with x ranging from 0 to 1.
21. The method as claimed in claim 18 , wherein the composition also comprises CeCl 3 and/or CeBr 3 .
22. The method as claimed in claim 1 , wherein the material is heated by graphite elements.