Fabrication of a scintillator material of elpasolite type
A process for fabricating a crystalline scintillator material with an elpasolite structure that has a theoretical composition of A 2 BC (1-y) M y X (6-y) can include conducting crystallization by cooling from a melt bath including r moles of A and s moles of B. A is chosen from Cs, Rb, K, and Na. B is chosen from Li, K, and Na. C is chosen from athe rare earth elements, Al, and Ga. M is chosen from the alkaline earth elements. X is chosen from F, Cl, Br, and I, and y represents the atomic fraction of substitution of C by M and is in the range extending from 0 to 0.05. The melt bath can be in contact with the material containing A and B in such a way that 2s/r is above 1. The process shows an improved fabrication yield. The crystals formed therefrom can have improved scintillation properties.
1. A process for fabricating a crystalline scintillator material with a structure of elpasolite type of theoretical composition A 2 BC (1-y) M y X (6-y) , comprising conducting crystallization by cooling from a melt bath comprising r moles of A and s moles of B,
wherein:
A is chosen from among Cs, Rb, K, Na;
B is chosen from among Li, K, Na and comprises Li;
C is chosen from among the rare earths, Al, and Ga;
M is chosen from among the alkaline earths; and
X is chosen from among F, Cl, Br, and I and comprises Cl or Br or I, y representing an atomic fraction of substitution of C by M and being in a range extending from 0 to 0.05;
wherein the crystalline scintillator material is doped with an element activating scintillation;
wherein the melt bath in contact with the material contains A and B in such a way that 2s/r is above 1; and
wherein a first two-thirds in volume of growth of the crystalline material comprises less than 10% in volume of a phase different to that of the elpasolite.
2. The process as claimed in claim 1 , wherein 2s/r is above 1.05.
3. The process as claimed in claim 1 , wherein 2s/r is above 1.15.
4. The process as claimed in claim 1 , wherein 2s/r is above 1.25.
5. The process as claimed in claim 1 , wherein 2s/r is above 1.35.
6. The process as claimed in claim 1 , wherein 2s/r is above 1.5.
7. The process as claimed in claim 1 , wherein 2s/r is below 10.
8. The process as claimed in claim 1 , wherein 2s/r is below 5.
9. The process as claimed in claim 1 , wherein 2s/r is below 3.
10. The process as claimed in claim 1 , wherein 2s/r is enough for a ratio of a double of an atomic fraction of B-type element to an atomic fraction of the A-type element in the crystalline material to be of at least 0.97.
11. The process as claimed in claim 1 , wherein M is chosen from among Ca, Mg, Sr, and Ba.
12. The process as claimed in claim 1 , wherein C comprises at least one activating rare earth chosen from among Ce, Pr, Eu, Tb and Nd, wherein a ratio of an atomic fraction of the at least one activating rare earth to a sum of atomic fractions of elements C and M in the crystalline material is above 0.00001 and below or equal to 0.1.
13. The process as claimed in claim 1 , wherein 2s/r is not enough to generate formation of a phase of B 3 C (1-y) M y X 6 at start of the crystallization.
14. The process as claimed in claim 1 , wherein B is Li.
15. The process as claimed in claim 1 , wherein the rare earth comprises La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y.
16. The process as claimed in claim 1 , wherein A comprises Cs and B comprises Li.
17. The process as claimed in claim 16 , wherein C comprises La and X comprises Br.
18. The process as claimed in claim 17 , wherein C is at over 80% in moles lanthanum and X is at over 80% in moles bromine.
19. The process as claimed in claim 16 , wherein C comprises Y and X comprises Cl.
20. The process as claimed in claim 19 , wherein C is at over 80% in moles Y and in that X is at over 80% in moles Cl.
21. The process as claimed in claim 1 , wherein 2t/r is above 1, t representing the number of moles of C in the bath.
22. The process as claimed in claim 1 , wherein:
2t/r is above 1, t representing the number of moles of C in the bath;
C comprises La, wherein C is at over 80% in moles La;
X comprises Br, wherein X is at over 80% in moles Br; and
2s/r is above 1.05.
23. The process as claimed in claim 1 , wherein the process is a monocrystalline growth process.
24. The process as claimed in claim 23 , wherein the crystalline material is a monocrystalline material.
25. The process as claimed in claim 24 , wherein the process is a Czochralski type, wherein the first two-thirds in volume of the growth of the monocrystalline material do not contain any phase different to that of the elpasolite.
26. The process as claimed in claim 23 , wherein the crystalline material is an ingot, wherein a first two-thirds in volume of the monocrystalline growth comprises less than 10% in volume of a phase different to that of the elpasolite material.
27. The process as claimed in claim 26 , wherein the crystalline material is a monocrystalline material, and the first two-thirds in volume of the monocrystalline growth of the monocrystalline material do not contain any phase different to that of the elpasolite material.
28. The process as claimed in claim 1 , wherein the crystalline material is made from incongruent fusion.
29. A crystalline scintillator material, wherein the crystalline scintillator material:
is doped with an element that activates scintillation;
has a structure of an elpasolite type of a theoretical composition A 2 BC (1-y) M y X (6-y) ; and has a real formula A a B b C c M m X x , wherein
A is chosen from among Cs, Rb, K, Na;
B is chosen from among Li, K, Na and comprises Li;
C is chosen from among the rare earths, Al, Ga;
M is chosen from among the alkaline earths; and
X is chosen from among F, Cl, Br, I and comprises Cl or Br or I;
y representing an atomic fraction of substitution of C by M and being in a range extending from 0 to 0.05, a, b, c, m, and x representing respective atomic fractions of A, B, C, M, and X, a 2b/a ratio being in a range extending from 0.97 to 1.4, wherein the crystalline scintillator material is monocrystalline.
30. The crystalline scintillator material as claimed in claim 29 , wherein C contains at least one activating rare earth chosen from among Ce, Pr, Eu, Tb, and Nd, wherein a ratio of an atomic fraction of the at least one activating rare earth to a sum of the atomic fractions of elements C and M is above 0.00001 and below or equal to 0.1.
31. The crystalline scintillator material as claimed in claim 29 , characterized in that A comprises Cs.
32. The crystalline scintillator material as claimed in claim 31 , wherein C comprises La and X comprises Br.
33. The crystalline scintillator material as claimed in claim 32 , wherein C is at over 80% in moles lanthanum and X is at over 80% in moles bromine.
34. The crystalline scintillator material as claimed in claim 32 , wherein the 2b/a ratio is in the range extending from 1.1to 1.4.
35. The crystalline scintillator material as claimed in claim 31 , wherein C comprises Y and X comprises Cl.
36. The crystalline scintillator material as claimed in claim 35 , wherein C is at over 80% in moles Y and X is at over 80% in moles Cl.
37. The crystalline scintillator material as claimed in claim 29 , wherein;
A comprises Cs;
C comprises La and Ce; and
X comprises Br.
38. The crystalline scintillator material as claimed claim 29 , wherein C comprises La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y.
39. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of Y and Ce, and X is Cl.
40. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of La and Ce, and X is Br.
41. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of La and Ce, and X is Cl.
42. The crystalline scintillator material as claimed in claim 29 , wherein A is a mixture of Cs and Rb, B is Li, C is a mixture of La and Ce, and X is Br.
43. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of La and Ce, and X is a mixture of Cl and Br.
44. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of Y and Ce, and X is a mixture of Cl and Br.
45. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of La, Y and Ce, and X is Cl.
46. The crystalline scintillator material as claimed in claim 29 , wherein A is a mixture of Cs and Na, B is a mixture of Li and Na, C is a mixture of Y and Ce, and X is Cl.
47. The crystalline scintillator material as claimed in claim 29 , wherein A is Cs, B is Li, C is a mixture of Y and Ce, and X is F.
48. The crystalline scintillator material as claimed in claim 29 , wherein the crystalline material is made from incongruent fusion.
49. An ingot comprising a crystalline scintillator material of claims 48 , wherein a first two-thirds in volume of a monocrystalline growth of the ingot comprises less than 10% in volume of a phase different to that of the elpasolite material.
50. The ingot of claim 49 , wherein the first two-thirds in volume of the monocrystalline growth does not contain any phase different to that of the elpasolite material.
51. The crystalline scintillator material as claimed in claim 29 , wherein the crystalline scintillator material has a scintillation energy resolution below 6%, measured with a source of 137 Cs gamma rays of 662 keV.
52. An ingot comprising a crystalline scintillator material of claim 29 .
53. A monocrystalline scintillator material, wherein the monocrystalline scintillator material
is doped with an element that activates scintillation;
has a structure of an elpasolite type of a theoretical composition A 2 BC (1-y) M y X (6-y) ; and has a real formula A a B b C c M m X x , wherein
A comprises Cs;
B comprises Li;
C is chosen from among the rare earths, Al, Ga;
M is chosen from among the alkaline earths; and
X comprises Cl or Br;
y representing an atomic fraction of substitution of C by M and being in a range extending from 0 to 0.05, a, b, c, m, and x representing respective atomic fractions of A, B, C, M, and X, a 2b/a ratio being in a range extending from 0.97 to 1.4.
54. The monocrystalline scintillator material of claim 53 , wherein C comprises La and X comprises Br.
55. The monocrystalline scintillator material of claim 53 , wherein C comprises Y and X comprises Cl.