Doped cadmium tungstate scintillator with improved radiation hardness

• US 7,279,120 B2
• Filed: 08/27/2004
• Issued: 10/09/2007
• Est. Priority Date: 09/04/2003
• Status: Expired due to Fees

• Current Assignee: Intematix Corporation
• Original Assignee: Intematix Corporation
• Inventors: Cheng, Shifan, Li, Yi-Qun
• Primary Examiner(s): KOSLOW, CAROL M
• Application Number:
  US10/928,755
• Publication Number:
  US 20060043335A1
• Time in Patent Office: 1,138 Days
• Field of Search: 252/301.5, 252/301.6 R, 378/4, 378/98.8, 378/98.12, 250/362, 250/367, 250/475.2, 250/483.1, 250/370.09
• US Class Current: 252/301.5
• CPC Class Codes: C04B 2235/3201 Alkali metal oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3203 Lithium oxide 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 2235/3225 Yttrium oxide or oxide-forming salts thereof
• 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 2235/3258 Tungsten oxides, tungstates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3284 Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3291 Silver oxides
• CPC Class Codes: C04B 2235/3298 Bismuth oxides, bismuthates or oxide forming salts thereof, e.g. zinc bismuthate
• CPC Class Codes: C04B 35/495 based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates
• CPC Class Codes: C09K 11/682 with zinc or cadmium
• CPC Class Codes: C09K 11/7457 Vanadates; Chromates; Molybdates; Tungstates
• CPC Class Codes: C09K 11/7708 Vanadates; Chromates; Molybdates; Tungstates
• CPC Class Codes: C30B 15/00 Single-crystal growth by pulling from a melt, e.g. Czochralski method under a protective fluid C30B27/00
• CPC Class Codes: C30B 29/32 Titanates; Germanates; Molybdates; Tungstates
• CPC Class Codes: G21K 4/00 Conversion screens for the conversion of the spatial distribution of X-rays or particle radiation into visible images, e.g. fluoroscopic screens photographic processes using X-ray intensifiers G03C5/17; discharge tubes comprising luminescent screens H01J1/62; cathode ray tubes for X-ray conversion with optical output H01J31/50

Abstract

This invention provides novel cadmium tungstate scintillator materials that show improved radiation hardness. In particular, it was discovered that doping of cadmium tungstate (CdWO₄) with trivalent metal ions or monovalent metal ions is particularly effective in improving radiation hardness of the scintillator material.

Claims

1. A sintered body comprising a scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, the scintillator composition being a component of the sintered body, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄.

2. The sintered body of claim 1, wherein the doped cadmium tungstate is represented by the formula:

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

X ranges from 0 to about 0.01;

Y ranges from 0 to about 0.01; and

at least one of X or Y is non-zero.

6. The sintered body of claim 2, wherein Y is about 0.005.

7. The sintered body of claim 2, wherein Y is about 0.001.

8. The sintered body of claim 6, wherein X is 0.

9. The sintered body of claim 7, wherein X is 0.

10. The sintered body of claim 2, wherein X is zero, and Y is greater than zero.

11. The sintered body of claim 10, wherein B is Gd³⁺.

17. A detector element of an X-ray CT scanner comprising a scintillator composition of any one of claims 1 through 16.

18. An x-ray detector comprising:

a scintillator composition of any one of claims 1 through 16; and

a photodetector disposed to detect light emitted by said scintillator composition.

19. The detector of claim 18, wherein said photodetector is selected from the group consisting of a photomultiplier, a photodiode, and photographic-film.

20. A method of producing an X-ray image, said method comprising:

providing an x-ray detector comprising a scintillator composition of any one of claims 1 through 16;

subjecting said scintillator composition to X-ray radiation; and

detecting light emission from said scintillator composition.

3. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

wherein X is about 0.005; and

,

Y ranges from 0 to about 0.01.

4. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

wherein X is about 0.001; and

Y ranges from 0 to about 0.01.

5. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

wherein X is about 0.001 or about 0.005; and

,

wherein Y is 0.

12. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

wherein X ranges from 0 to about 0.01; and

,

B is Gd³⁺ and Y ranges from about 0.0002 to about 0.001.

13. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

wherein X and Y are both 0.01 or less; and

,

wherein X and Y are both greater than zero.

14. The scintillator composition of claim 13, wherein A is K¹⁺ or Rb¹⁺ and B is Bi³⁺.

15. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Li, Na, K, Rb, Cs, Ag, Tl, and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Y, La, Ce, Pr, Nd, Gd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof;

wherein X ranges from greater than zero to about 0.01, and Y is zero.

16. A scintillator composition comprising a cadmium tungstate doped with a monovalent metal ion and/or a trivalent metal ion, wherein said scintillator composition shows higher radiation tolerance than undoped CdWO₄;

and,

wherein the doped cadmium tungstate is represented by the formula;

Cd<sub>(1−

(x+y))</sub>A_xB_yWO₄

where;

A is a monovalent metal ion selected from the group consisting of;

Na, K and combinations thereof;

B is a trivalent metal ion selected from the group consisting of;

Bi, Gd, and combinations thereof;

wherein said doped cadmium tungstate is selected from the group consisting of Cd_0.9995Na_0.0005WO₄, Cd_0.9995Gd_0.0005WO₄, and Cd_0.999(KBi)_0.001WO₄.