US20030127630A1
Expired / Lapsed
US
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Terbium or lutetium containing garnet scintillators having increased resistance to radiation damage
Assignee: General Electric Co
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Filing: 2002-12-10
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Granted: —
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Expires: 2022-12-10
Abstract
Abstract The present invention provides terbium or lutetium garnet x ray scintillators activated with a rare earth metal ion, such as cerium, and treated by annealing in a controlled atmosphere comprising a predetermined amount of oxygen for a predetermined time and temperature to reduce radiation damage that would otherwise occur when the scintillator material is exposed to high energy radiation, such as the type of radiation required to use the scintillator for medical radiographic imaging and the like. In an embodiment, a single crystal or a polycrystalline scintillator comprising the general formula (Tb 1−x Lu x Ce y ) 3 Al 5 O 12 (where 0<x≦0.5, and y is in the range from about 0.0005 to about 0.2, and annealed at 1400° C. to 1500° C. in a controlled atmosphere comprising 1×10 −6 to 0.22 atm oxygen shows an increased resistance to radiation damage.
Inventors
- 👤 James Vartuli
- 👤 Steven Duclos
- 👤 Robert Lyons
- 👤 Charles Greskovich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 07:52
CPC Classifications
G; G01; G01T; G01T1/00; G01T1/16; G01T1/20; G01T1/202; G01T1/2023; C; C09; C09K; C09K11/00; C09K11/08; C09K11/77; C09K11/7766; C09K11/7767; C09K11/7769; C09K11/7774; C30; C30B; C30B15/00; C30B29/00; C30B29/10; C30B29/16; C30B29/22; C30B29/28; C30B33/00; C30B33/02
Claims Analysis
Total Claims: 74
Claim 1
Independent Claim
134 words
1 . A method for preparing a terbium or lutetium containing garnet scintillator having increased resistance to radiation-induced changes in scintillator efficiency comprising annealing a garnet scintillator in a controlled atmosphere comprising a predetermined amount of oxygen for a predetermined time and temperature, such that the annealed scintillator comprises a smaller radiation-induced change in efficiency of signal generation than a same scintillator not treated by said annealing, wherein said garnet scintillator comprises at least one metal selected from the group consisting of terbium (Tb) and lutetium (Lu), and is activated with at least one rare earth element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er and Tm, said scintillator being capable of emitting visible light in response to excitation by high-energy radiation comprising x, β, or γ radiation:
Claim 2
Dependent Claim
134 words
1 . A method for preparing a terbium or lutetium containing garnet scintillator having increased resistance to radiation-induced changes in scintillator efficiency comprising annealing a garnet scintillator in a controlled atmosphere comprising a predetermined amount of oxygen for a predetermined time and temperature, such that the annealed scintillator comprises a smaller radiation-induced change in efficiency of signal generation than a same scintillator not treated by said annealing, wherein said garnet scintillator comprises at least one metal selected from the group consisting of terbium (Tb) and lutetium (Lu), and is activated with at least one rare earth element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er and Tm, said scintillator being capable of emitting visible light in response to excitation by high-energy radiation comprising x, β, or γ radiation:
Claim 3
Dependent Claim
15 words
2 . The method of claim 1 , wherein said scintillator is prepared by sintering.
Claim 4
Dependent Claim
15 words
3 . The method of claim 2 , wherein said scintillator comprises a polycrystalline ceramic.
Claim 5
Dependent Claim
18 words
4 . The method of claim 1 , wherein said scintillator is prepared by a crystal growth process.
Claim 6
Dependent Claim
18 words
5 . The method of claim 4 , wherein said scintillator comprises at least one isolated single crystal.
Claim 7
Dependent Claim
31 words
6 . The method of claim 1 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −18 atm up to and including 1 atm.
Claim 8
Dependent Claim
31 words
7 . The method of claim 1 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −13 atm up to and including 1 atm.
Claim 9
Dependent Claim
31 words
8 . The method of claim 1 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −8 atm up to and including 0.5 atm.
Claim 10
Dependent Claim
31 words
9 . The method of claim 1 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 6 atm up to and including 0.22 atm.
Claim 11
Dependent Claim
21 words
10 . The method of claim 1 , wherein the annealing temperature comprises a range from 1000° C. to 1500° C.
Claim 12
Dependent Claim
21 words
11 . The method of claim 1 , wherein the annealing temperature comprises a range from 1400° C. to 1500° C.
Claim 13
Dependent Claim
23 words
12 . The method of claim 1 , wherein the time period for annealing comprises a range from 0.5 to 12 hours (h).
Claim 14
Dependent Claim
23 words
13 . The method of claim 1 , wherein the time period for annealing comprises a range from 1 to 8 hours (h).
Claim 15
Dependent Claim
23 words
14 . The method of claim 1 , wherein the time period for annealing comprises a range from 1 to 4 hours (h).
Claim 16
Dependent Claim
19 words
15 . The method of claim 1 , wherein the scintillator is cooled to room temperature after said annealing.
Claim 17
Dependent Claim
25 words
16 . The method of claim 15 , wherein the rate of cooling to room temperature ranges between 150° C. and 500° C. per hour.
Claim 18
Dependent Claim
82 words
17 . The method of claim 1 , wherein prior to annealing, said scintillator comprises the formula (Tb 1−y Ce y ) a D z O 12 ; wherein D is at least one metal selected from the group consisting of Al, Ga, and In; a is in a range from about 2.8 up to and including 3.1; y is in a range from 0.0005 up to including 0.2; and z is in a range from 4 up to and including 5.1.
Claim 19
Dependent Claim
83 words
18 . The method of claim 1 , wherein prior to annealing, said garnet scintillator comprises the formula (Lu 1−y Ce y ) a D z O 12 ; wherein D is at least one metal selected from the group consisting of Al, Ga, and In; a is in a range from 2.8 up to and including 3.1; y is in a range from 0.0005 up to and including 0.2; and z is in a range from 4 up to and including 5.1.
Claim 20
Dependent Claim
177 words
19 . The method of claim 1 , wherein prior to annealing, said garnet scintillator comprises the formula (G 1−x−y A x RE y ) a D z O 12 ; wherein G is at least one metal selected from the group consisting of Tb and Lu; A is at least one rare earth metal selected from the group consisting of Y, La, Gd, Lu, and Yb when G is Tb and selected from the group consisting of Y, La, Gd, Tb, and Yb when G is Lu; RE is at least one rare earth metal selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er, and Tm; D is at least one metal selected from the group consisting of Al, Ga, and In; a is a range from about 2.8 up to and including 3.1; x is in a range from 0 up to and including 0.5; y is in a range from 0.0005 up to and including 0.2; and z is in a range from 4 up to and including 5.1.
Claim 21
Dependent Claim
19 words
20 . The method of claim 19 , wherein A is Lu, RE is Ce, and D is Al.
Claim 22
Dependent Claim
25 words
21 . The method of claim 19 , wherein said scintillator comprises the formula (Tb 1−y Ce y ) a Al 5 O 12 .
Claim 23
Dependent Claim
27 words
22 . The method of claim 19 , wherein said scintillator comprises the formula (Tb 1−x−y Lu x Ce y ) a Al 5 O 12 .
Claim 24
Dependent Claim
29 words
23 . The method of claim 19 , wherein said scintillator comprises the formula (Tb 1−x Lu x Ce y ) 3 Al 5 O 12 , where 0<x≦0.5.
Claim 25
Dependent Claim
76 words
24 . The method of claim 1 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−y Ce y ) 3 (Al 1−r−s Ga r In s ) z O 12 , where y is in the range from about 0.0005 up to and including 0.2, and z is in the range from about 4 up to and including 5.1, and 0≦r≦0.5 when 0<s≦0.5 and r+s≦1, or 0<r≦0.5 when 0≦s≦0.5 and r+s≦1.
Claim 26
Dependent Claim
69 words
25 . The method of claim 1 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−y−u−v−w Ce y Y u Gd v Sm w ) 3 Al 5 O 12 , where y is in the range from about 0.0005 up to and including 0.2; and z is in the range from about 4 up to and including 5.1, 0≦u, v, w≦0.5, and 0.0005≦y+u+v+w<1.
Claim 27
Dependent Claim
67 words
26 . The method of claim 1 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−x−y A x Ce y ) 3 Al z O 12 , where A is Y or Gd, 0<x≦0.5, and y is in the range from about 0.0005 up to and including 0.2, and z is in the range from about 4 up to and including 5.1.
Claim 28
Dependent Claim
31 words
27 . The method of claim 1 , wherein prior to annealing, said garnet scintillator comprises Lu 0 8 Tb 2 2 Al 5 O 12 activated with Ce 3+ ions.
Claim 29
Dependent Claim
19 words
28 . The method of claim 1 , wherein said annealing step changes the oxygen content of the scintillator.
Claim 30
Dependent Claim
140 words
29 . The method of claim 2 , wherein said sintered scintillator is prepared by the following steps: (a) providing amounts of: (i) oxygen-containing compounds of at least one first metal selected from the group consisting of terbium and lutetium; (ii) oxygen-containing compounds of at least one rare-earth metal selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er, and Tm; and (iii) oxygen-containing compounds of at least one second metal selected from the group consisting of Al, Ga, and In, wherein said amounts of oxygen-containing compounds are chosen to obtain the final desired composition of said scintillator; and (b) mixing together said oxygen-containing compounds to form a mixture; and (c) firing said mixture by calcining at a temperature for a time sufficient to convert said mixture to a rare earth-activated garnet scintillator of defined composition.
Claim 31
Dependent Claim
24 words
30 . The method of claim 29 , wherein said calcining comprises firing at a temperature that ranges from 700° C. to 1500° C.
Claim 32
Dependent Claim
24 words
31 . The method of claim 29 , wherein said calcining comprises firing at a temperature that ranges from 800° C. to 1200° C.
Claim 33
Dependent Claim
25 words
32 . The method of claim 29 , further comprising packing the calcined oxygen-containing compounds into compact comprising a scintillator body of the desired shape.
Claim 34
Dependent Claim
26 words
33 . The method of claim 32 , further comprising sintering the compacted scintillator body by firing at high temperature to minimize porosity of the compact.
Claim 35
Dependent Claim
19 words
34 . The method of claim 33 , wherein the sintering temperature ranges from 1500° C. to 1800° C.
Claim 36
Dependent Claim
19 words
35 . The method of claim 33 , wherein the sintering temperature ranges from 1600° C. to 1780° C.
Claim 37
Dependent Claim
35 words
36 . The method of claim 1 , wherein said annealed scintillator comprises a change in efficiency of light emission having an absolute value of less than 3% upon treatment with high energy X radiation.
Claim 38
Dependent Claim
125 words
37 . A scintillator having increased resistance to radiation-induced changes in scintillator efficiency comprising a garnet scintillator capable of emitting visible light in response to excitation by high-energy radiation comprising X, β, or γ radiation, wherein said garnet scintillator comprises at least one metal selected from the group consisting of terbium (Tb) and lutetium (Lu), and is activated with at least one rare earth element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er and Tm, and wherein said scintillator has been annealed in a controlled atmosphere containing a predetermined amount of oxygen for a predetermined time and temperature, such that the annealed scintillator comprises a smaller radiation-induced change in efficiency than a same scintillator not treated by said annealing.
Claim 39
Dependent Claim
125 words
37 . A scintillator having increased resistance to radiation-induced changes in scintillator efficiency comprising a garnet scintillator capable of emitting visible light in response to excitation by high-energy radiation comprising X, β, or γ radiation, wherein said garnet scintillator comprises at least one metal selected from the group consisting of terbium (Tb) and lutetium (Lu), and is activated with at least one rare earth element selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er and Tm, and wherein said scintillator has been annealed in a controlled atmosphere containing a predetermined amount of oxygen for a predetermined time and temperature, such that the annealed scintillator comprises a smaller radiation-induced change in efficiency than a same scintillator not treated by said annealing.
Claim 40
Dependent Claim
16 words
38 . The garnet scintillator of claim 37 , wherein said scintillator comprises a polycrystalline ceramic.
Claim 41
Dependent Claim
19 words
39 . The garnet scintillator of claim 37 , wherein said scintillator comprises at least one isolated single crystal.
Claim 42
Dependent Claim
30 words
40 . The garnet scintillator of claim 37 , wherein the annealed scintillator comprises an altered oxygen content as compared to the oxygen content of said scintillator prior to annealing.
Claim 43
Dependent Claim
33 words
41 . The garnet scintillator of claim 37 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −18 atm up to and including 1 atmosphere (atm).
Claim 44
Dependent Claim
32 words
42 . The garnet scintillator of claim 37 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −13 atm up to and including 1 atm.
Claim 45
Dependent Claim
32 words
43 . The garnet scintillator of claim 37 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −8 atm up to and including 0.5 atm.
Claim 46
Dependent Claim
32 words
44 . The garnet scintillator of claim 37 , wherein the controlled oxygen atmosphere comprises an oxygen partial pressure in the range from 1×10 −6 atm up to and including 0.22 atm.
Claim 47
Dependent Claim
22 words
45 . The garnet scintillator of claim 37 , wherein the annealing temperature comprises a range from 1000° C. to 1500° C.
Claim 48
Dependent Claim
22 words
46 . The garnet scintillator of claim 37 , wherein the annealing temperature comprises a range from 1400° C. to 1500° C.
Claim 49
Dependent Claim
24 words
47 . The garnet scintillator of claim 37 , wherein the time period for annealing comprises a range from 0.5 to 12 hours (h).
Claim 50
Dependent Claim
24 words
48 . The garnet scintillator of claim 37 , wherein the time period for annealing comprises a range from 1 to 8 hours (h).
Claim 51
Dependent Claim
24 words
49 . The garnet scintillator of claim 37 , wherein the time period for annealing comprises a range from 1 to 4 hours (h).
Claim 52
Dependent Claim
19 words
50 . The garnet scintillator of claim 37 , wherein the scintillator is cooled to room temperature after annealing.
Claim 53
Dependent Claim
26 words
51 . The garnet scintillator of claim 50 , wherein the rate of cooling to room temperature ranges between 150° C. and 500° C. per hour.
Claim 54
Dependent Claim
83 words
52 . The garnet scintillator of claim 37 , wherein prior to annealing, said garnet scintillator comprises the formula (Tb 1−y Ce y ) a D z O 12 ; wherein D is at least one metal selected from the group consisting of Al, Ga, and In; a is in a range from 2.8 up to and including 3.1; y is in a range from 0.0005 up to and including 0.2; and z is in a range from 4 to and including 5.1.
Claim 55
Dependent Claim
82 words
53 . The garnet scintillator of claim 37 , wherein prior to annealing, said scintillator comprises the formula (Lu 1−y Ce y ) a D z O 12 ; wherein D is at least one metal selected from the group consisting of Al, Ga, and In; a is in a range from 2.8 up to and including 3.1; y is in a range from 0.0005 up to including 0.2; and z is in a range from 4 up to and including 5.1.
Claim 56
Dependent Claim
176 words
54 . The garnet scintillator of claim 37 , wherein prior to annealing, said scintillator comprises the formula (G 1−x−y A x RE y ) a D z O 12 ; wherein G is at least one metal selected from the group consisting of Tb and Lu; A is at least one rare earth metal selected from the group consisting of Y, La, Gd, Lu, and Yb when G is Tb and selected from the group consisting of Y, La, Gd, Tb, and Yb when G is Lu; RE is at least one rare earth metal selected from the group consisting of Ce, Pr, Nd, Sm, Eu, Dy, Ho, Er, and Tm; D is at least one metal selected from the group consisting of Al, Ga, and In; a is a range from about 2.8 to and including 3.1; x is in a range from 0 up to and including 0.5; y is in a range from 0.0005 up to and including 0.2; and z is in a range from 4 up to and including 5.1.
Claim 57
Dependent Claim
21 words
55 . The scintillator of claim 54 , wherein a is in a range from 2.9 up to and including 3.05.
Claim 58
Dependent Claim
21 words
56 . The scintillator of claim 54 , wherein x is in a range from 0 up to and including 0.3.
Claim 59
Dependent Claim
21 words
57 . The scintillator of claim 54 , wherein x is in a range from 0 up to and including 0.2.
Claim 60
Dependent Claim
21 words
58 . The scintillator of claim 54 , wherein y is in a range from 0.005 up to and including 0.1.
Claim 61
Dependent Claim
21 words
59 . The scintillator of claim 54 , wherein y is in a range from 0.005 up to and including 0.07.
Claim 62
Dependent Claim
21 words
60 . The scintillator of claim 54 , wherein z is in a range from 4.5 up to and including 5.05.
Claim 63
Dependent Claim
21 words
61 . The scintillator of claim 54 , wherein z is in a range from 4.6 up to and including 5.0.
Claim 64
Dependent Claim
20 words
62 . The scintillator body of claim 54 , wherein A is Lu, RE is Ce, and D is Al.
Claim 65
Dependent Claim
25 words
63 . The scintillator of claim 54 , wherein said scintillator comprises the formula (Tb 1−y Ce y ) a Al 5 O 12 .
Claim 66
Dependent Claim
27 words
64 . The scintillator of claim 54 , wherein said scintillator comprises the formula (Tb 1−x−y Lu x Ce y ) a Al 5 O 12 .
Claim 67
Dependent Claim
29 words
65 . The scintillator of claim 54 , wherein, said scintillator comprises the formula (Tb 1−x Lu x Ce y ) 3 Al 5 O 12 , where 0<x≦0.5.
Claim 68
Dependent Claim
72 words
66 . The scintillator of claim 37 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−y Ce y ) 3 (Al 1−r−s Ga r In s ) z O 12 where y is in the range from about 0.0005 to about 0.2, and z is in the range from about 4 to and including 5.1, and 0≦r≦0.5 when 0<s≦0.5 and r+s<1, or 0<r≦0.5 when 0≦s≦0.5 and r+s<1.
Claim 69
Dependent Claim
66 words
67 . The scintillator of claim 37 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−y−u−v−w Ce y Y u Gd v Sm w ) 3 Al z O 12 , where y is in the range from about 0.0005 to about 0.2; and z is in the range from about 4 to and including 5.1, 0≦u, v, w≦0.5, and 0.0005≦y+u+v+w<1.
Claim 70
Dependent Claim
67 words
68 . The scintillator of claim 37 , wherein prior to annealing, said garnet scintillator has the formula of (Tb 1−x−y A x Ce y ) 3 Al z O 12 , where A is Y or Gd, 0<x≦0.5, and y is in the range from about 0.0005 up to and including 0.2, and z is in the range from about 4 up to and including 5.1.
Claim 71
Dependent Claim
31 words
69 . The scintillator body of claim 37 , wherein prior to annealing, the scintillator comprises Lu 0 8 Tb 2 2 Al 5 O 12 activated with Ce 3+ ions.
Claim 72
Dependent Claim
36 words
70 . The scintillator body of claim 37 , wherein said annealed scintillator comprises a change in efficiency of light emission having an absolute value of less than 3% upon treatment with high energy X radiation.
Claim 73
Dependent Claim
18 words
71 . A detector element of an x ray CT scanner comprising the scintillator of claim 37 .
Claim 74
Dependent Claim
17 words
72 . A detector element of an x ray CT scanner comprising the scintillator of claim 54.
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