US20030127630A1 — Terbium or lutetium containing garnet scintillato…

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.

Terbium or lutetium containing garnet scintillators having increased resistance to radiation damage

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