METHOD FOR PREPARING RARE-EARTH HALIDE BLOCKS

• US 20110293499A1
• Filed: 08/10/2011
• Published: 12/01/2011
• Est. Priority Date: 11/27/2002
• Status: Active Grant

• Current Assignee: Luxium Solutions LLC
• Original Assignee: Saint-Gobain Cristaux et Detecteurs
• Inventors: ILTIS, Alain
• Granted Patent: US 8,252,260 B2
• Time in Patent Office: Days
• US Class Current: 423/263
• CPC Class Codes: C04B 2235/3201 Alkali metal oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/444 Halide containing anions, e.g. bromide, iodate, chlorite
• CPC Class Codes: C04B 2235/6562 Heating rate
• CPC Class Codes: C04B 2235/658 Atmosphere during thermal treatment
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 35/5152 based on halogenides other than fluorides
• CPC Class Codes: C04B 35/653 Processes involving a melting step
• CPC Class Codes: C09K 11/7704 Halogenides C09K11/7701 takes precedence
• CPC Class Codes: C09K 11/7772 Halogenides C09K11/7767 takes precedence
• CPC Class Codes: C30B 11/00 Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method C30B13/00, C30B15/00, C30B17/00, C30B19/00 take precedence; under a protective fluid C30B27/00
• CPC Class Codes: C30B 29/12 Halides

Abstract

The invention relates to a method of preparing a polycrystalline block of a halide of formula A_eLn_fX_(3f+e) in which Ln represents one or more rare earths, X represents one or more halogen atoms selected from the group consisting of Cl, Br and I, and A represents one or more alkali metals selected from the group consisting of K, Li, Na, Rb and Cs, e, which may be zero, being less than or equal to 3f, and f being greater than or equal to 1, having a low water and oxyhalide content, in which the method comprises heating a mixture of, on the one hand, at least one compound having at least one Ln-X bond and, on the other hand, a sufficient amount of NH₄X in order to obtain the oxyhalide content, resulting in a molten mass comprising the rare-earth halide, the heating being followed by cooling, and the heating, after having reached 300° C., never going below 200° C. before the molten mass has been obtained. The blocks thus produced allow very pure single crystals having remarkable scintillation properties to be grown.

Claims

1. A single crystal of formula A_eLn_fX_(3f+e) in which Ln represents one or more rare earths, X represents one or more halogen atoms from selected from the group consisting of Cl, Br and I, and A represents one or more alkali metals selected from the group consisting of K, Li, Na, Rb and Cs, e and f representing values such that:

e, which may be zero, is less than or equal to 3f; and

f is greater than or equal to 1;

comprising less than 0.1% by weight of rare-earth oxyhalide.

2. The single crystal as claimed in claim 1, wherein its oxyhalide content is less than 0.05% by weight.

3. The single crystal as claimed in claim 2, wherein its oxyhalide content is less than 0.02% by weight.

4. The single crystal as claimed in claim 1, wherein Ln is chosen from selected from the group consisting of La, Gd, Y, Lu and Ce, and X is selected from the group consisting of Cl and Br.

5. The single crystal as claimed in claim 1, wherein the single crystal has a volume is at least 10 cm³.

6. The single crystal as claimed in claim 1, wherein the single crystal has a luminous efficiency at least 90% of that of a NaI crystal doped with 600 ppm by weight of TI iodide, the energy resolution of which at 622 keV is 6.8%, the integration time being 1 μ

s, and the radioactive source being Cs at 622 keV.

7. The single crystal as claimed in claim 1, wherein its the single crystal has an energy resolution is less than 5%.

8. The single crystal as claimed in claim 7, wherein the single crystal has an energy resolution less than 4%.

9. The single crystal as claimed in claim 8, wherein its the single crystal has an energy resolution is less than 3.5%.

10. The single crystal as claimed in claim 1, wherein the time for the main component to decay is less than 40 nanoseconds.

11. The single crystal as claimed in claim 10, wherein the time for the main component to decay is less than 30 nanoseconds.

12. The single crystal as claimed in claim 11, wherein the time for the main component to decay is less than 20 nanoseconds.