Cerium-doped alkaline-earth hafnium oxide scintillators having improved transparency and method of making the same

Claim 2

1 . A scintillator composition comprising alkaline earth hafnium oxide doped with cerium, wherein said alkaline earth metal is selected from the group consisting of barium, strontium, calcium, and combinations thereof; and an atomic ratio of said alkali earth metal and said hafnium is from about 0.9 to about 1.1; said scintillator being capable of emitting visible light in response to high-energy radiation selected from the group consisting of X, β, and γ radiation and having improved light transparency.

Claim 3

2 . The scintillator composition according to claim 1 , wherein cerium is present in amount from about 0.005 atom percent to about 5 atom percent.

Claim 4

3 . The scintillator composition according to claim 1; wherein said atomic ratio is preferably in a range from about 0.95 to about 1.05.

Claim 5

4 . The scintillator composition according to claim 3; wherein cerium is preferably present in an amount in a range from about 0.01 to about 2 atom percent, and more preferably from about 0.01 to about 1 atom percent.

Claim 6

5 . The scintillator composition according to claim 1 , wherein said scintillator composition is a polycrystalline material.

Claim 7

6 . The scintillator composition according to claim 5 , wherein said polycrystalline material has a porosity less than about 0.05 percent.

Claim 8

7 . The scintillator composition according to claim 5 , wherein said polycrystalline material has a density greater than about 7.6 g/cm 3 .

Claim 9

8 . The scintillator composition according to claim 1 , further comprising at least a trivalent ion other than cerium and having a formula of Al 1−x−y M III x Ce y Hf 1−(x+y)/4 O 3 wherein 0<x≦0.5, 0<y≦0.05, and M III is a trivalent ion other than cerium.

Claim 10

9 . The scintillator composition according to claim 8 , wherein M III is selected from the group consisting of lanthanum, gadolinium, lutetium, and combinations thereof.

Claim 11

10 . The scintillator composition according to claim 1 further comprising at least a trivalent ion other than cerium and having a formula of A 1−3x−3y M III 2x Ce 2y HfO 3 wherein 0<x≦0.1, 0<y≦0.025, and M III is a trivalent ion other than cerium.

Claim 12

11 . The scintillator composition according to claim 10 , wherein M III is selected from the group consisting of lanthanum, gadolinium, lutetium, and combinations thereof.

Claim 13

12 . The scintillator composition according to claim 1 further comprising at least a trivalent ion other than cerium and having a formula of A 1−y Ce y Hf 1−z M III z O 3 wherein 0<y≦0.05, 0<z≦0.05, and M III is a trivalent ion other than cerium.

Claim 14

13 . The scintillator composition according to claim 12 , wherein M III is selected from the group consisting of lutetium, ytterbium, gadolinium, holmium, aluminum, gallium, indium, and combinations thereof.

Claim 15

14 . The scintillator composition according to claim 12 , wherein M III is selected from the group consisting of lutetium, aluminum, and combinations thereof.

Claim 16

15 . The scintillator composition according to claim 14 , wherein M III is lutetium.

Claim 17

16 . The scintillator composition according to claim 14 , wherein M III is aluminum.

Claim 18

17 . The scintillator composition according to claim 1 further comprising at least a tetravalent ion and having a formula of A 1−y Ce y Hf 1−z M IV z O 3 wherein 0<y≦0.05, 0<z≦0.05, and M IV is a tetravalent ion.

Claim 19

18 . The scintillator composition according to claim 17 , wherein M IV is selected from the group consisting of zirconium, tin, tellurium, titanium, germanium, silicon, and combinations thereof.

Claim 20

19 . The scintillator composition according to claim 1 further comprising at least a trivalent ion other than cerium and a divalent ion, and having a formula of A 1−2y−2v Ce 2y M III 2v Hf 1−y−v M II y+v O 3 wherein 0<y≦0.025, 0<v≦0.1, M III is a trivalent ion other than cerium, and M II is a divalent ion.

Claim 21

20 . The scintillator composition according to claim 19 , wherein M III is selected from the group consisting of lanthanum, gadolinium, lutetium, and combinations thereof; and M II is selected from the group consisting of magnesium, calcium, and combinations thereof.

Claim 22

21 . A method for producing a cerium-doped alkaline earth hafnium oxide scintillator composition that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof; said method comprising the steps of: providing a mixture of compounds of cerium, hafnium, and said at least one alkaline earth metal; firing said mixture in an oxygen-containing atmosphere at a firing temperature for a time sufficient to convert said mixture to a cerium-doped alkaline earth hafnium oxide; and annealing said cerium-doped alkaline earth hafnium oxide to produce said cerium-doped alkaline earth hafnium oxide scintillator composition; wherein amounts of compounds are chosen to obtain the final desired composition of said scintillator, and said scintillator is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 23

21 . A method for producing a cerium-doped alkaline earth hafnium oxide scintillator composition that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof; said method comprising the steps of: providing a mixture of compounds of cerium, hafnium, and said at least one alkaline earth metal; firing said mixture in an oxygen-containing atmosphere at a firing temperature for a time sufficient to convert said mixture to a cerium-doped alkaline earth hafnium oxide; and annealing said cerium-doped alkaline earth hafnium oxide to produce said cerium-doped alkaline earth hafnium oxide scintillator composition; wherein amounts of compounds are chosen to obtain the final desired composition of said scintillator, and said scintillator is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 24

22 . The method according to claim 21 , wherein said providing further comprises providing amounts of compounds of at least an ion selected from the group consisting of divalent ions, trivalent ions other than cerium, tetravalent ions, and combinations thereof.

Claim 25

23 . The method according to claim 21 further comprising the step of: calcining said cerium-doped alkaline earth hafnium oxide scintillator composition in a reducing atmosphere to produce a calcined scintillator material.

Claim 26

24 . The method according to claim 21 , wherein said firing in said oxygen-containing atmosphere is carried out at a temperature in a range from about 900° C. to about 1500° C. for a time of up to 10 hours.

Claim 27

25 . The method according to claim 21 , wherein said firing in said oxygen-containing atmosphere is preferably carried out at a temperature in a range from about 1000° C. to about 1400° C.

Claim 28

26 . The method according to claim 23 , wherein said calcining is carried out at a temperature in a range from about 1000° C. to about 1600° C. for a time of up to 10 hours.

Claim 29

27 . The method according to claim 23 , wherein said calcining is preferably carried out at a temperature in a range from about 1000° C. to about 1500° C., and more preferably from about 1000° C. to about 1450° C.

Claim 30

28 . The method according to claim 21 , wherein said annealing is conducted at a temperature greater than about 1600° C.

Claim 31

29 . A method for producing a shaped cerium-doped alkaline earth hafnium oxide scintillator that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof, said method comprising the steps of: providing a starting mixture of compounds of cerium, hafnium, and said at least one alkaline earth metal; converting said compounds in said starting mixture substantially to water-insoluble oxygen-containing compounds to form a mixture of water-insoluble oxygen-containing compounds; firing said mixture of said oxygen-containing compounds at a firing temperature for a time sufficient to convert said mixture to a cerium-doped alkaline earth hafnium oxide; and hot isostatically pressing said cerium-doped alkaline earth hafnium oxide to form said shaped cerium-doped alkaline earth hafnium oxide scintillator; wherein amounts of said compounds are chosen to obtain a final desired composition of said scintillator, and said scintillator is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 32

29 . A method for producing a shaped cerium-doped alkaline earth hafnium oxide scintillator that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof, said method comprising the steps of: providing a starting mixture of compounds of cerium, hafnium, and said at least one alkaline earth metal; converting said compounds in said starting mixture substantially to water-insoluble oxygen-containing compounds to form a mixture of water-insoluble oxygen-containing compounds; firing said mixture of said oxygen-containing compounds at a firing temperature for a time sufficient to convert said mixture to a cerium-doped alkaline earth hafnium oxide; and hot isostatically pressing said cerium-doped alkaline earth hafnium oxide to form said shaped cerium-doped alkaline earth hafnium oxide scintillator; wherein amounts of said compounds are chosen to obtain a final desired composition of said scintillator, and said scintillator is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 33

30 . The method according to claim 29 further comprising calcining said cerium-doped alkaline earth hafnium oxide under a reducing atmosphere before the step of hot isostatically pressing.

Claim 34

31 . The method according to claim 29 further comprising annealing said shaped cerium-doped alkaline earth hafnium oxide scintillator after the step of hot isostatically pressing.

Claim 35

32 . The method according to claim 30 further comprising annealing said cerium-doped alkaline earth hafnium oxide scintillator after the step of calcining and sintering said cerium-doped alkaline earth hafnium oxide scintillator before the step of hot isostatically pressing.

Claim 36

33 . The method according to claim 29 , wherein said mixture further comprises compounds of at least an ion selected from the group consisting of divalent ions, trivalent ions other than cerium, tetravalent ions, and combinations thereof.

Claim 37

34 . The method according to claim 29 , wherein said compounds are selected from the group consisting of oxides, carbonates, nitrates, halides, oxyhalides, oxynitrates, sulfates, salts of mono- and di-carboxylic acids containing 1 to 6 carbon atoms, esters of di-carboxylic acids containing 1 to 6 carbon atoms, salts of aromatic acids containing up to 2 aromatic rings, acetylacetonates, alkoxides, and mixtures thereof.

Claim 38

35 . A method for producing a cerium-doped alkaline earth hafnium oxide scintillator composition that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof; said method comprising the steps of: providing a first solution comprising compounds of at least cerium, hafnium, and said at least one alkaline earth metal; providing a second solution selected from the group consisting of ammonium hydroxide; alkyl esters of a di-carboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, and glutaric acid; amines selected from the group consisting of methanolamine, ethanolamine, propanolamine, dimethanolamine, diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, and tripropanolamine; and mixtures thereof; mixing together said first solution and said second solution to form a precipitate mixture of oxygen-containing compounds of at least cerium, hafnium, and said at least one alkaline earth metal; separating said precipitate mixture from a supernatant liquid; firing said precipitate mixture at a temperature and for a time sufficient to convert said dried precipitate mixture to said cerium-doped hafnium oxide scintillator composition; wherein amounts of said compounds are chosen to obtain a final desired composition of said scintillator that is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 39

35 . A method for producing a cerium-doped alkaline earth hafnium oxide scintillator composition that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof; said method comprising the steps of: providing a first solution comprising compounds of at least cerium, hafnium, and said at least one alkaline earth metal; providing a second solution selected from the group consisting of ammonium hydroxide; alkyl esters of a di-carboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, and glutaric acid; amines selected from the group consisting of methanolamine, ethanolamine, propanolamine, dimethanolamine, diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, and tripropanolamine; and mixtures thereof; mixing together said first solution and said second solution to form a precipitate mixture of oxygen-containing compounds of at least cerium, hafnium, and said at least one alkaline earth metal; separating said precipitate mixture from a supernatant liquid; firing said precipitate mixture at a temperature and for a time sufficient to convert said dried precipitate mixture to said cerium-doped hafnium oxide scintillator composition; wherein amounts of said compounds are chosen to obtain a final desired composition of said scintillator that is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 40

36 . The method according to claim 35 , wherein said first solution further comprises amounts of compounds of at least an ion selected from the group consisting of divalent ions, trivalent ions other than cerium, tetravalent ions, and combinations thereof.

Claim 41

37 . The method according to claim 35 further comprising the step of calcining said cerium-doped alkaline earth hafnium oxide scintillator composition in a reducing atmosphere to produce a calcined scintillator material.

Claim 42

38 . The method according to claim 35 , wherein said firing is carried out in an oxygen-containing atmosphere at a temperature in a range from about 900° C. to about 1500° C. for a time of up to 10 hours.

Claim 43

39 . The method according to claim 35 , wherein said firing in said oxygen-containing atmosphere is preferably carried out at a temperature in a range from about 1000° C. to about 1400° C.

Claim 44

40 . The method according to claim 37 , wherein said calcining is carried out at a temperature in a range from about 1000° C. to about 1600° C. for a time of up to 10 hours.

Claim 45

41 . The method according to claim 37 , wherein said calcining is preferably carried out at a temperature in a range from about 1000° C. to about 1500° C., and more preferably from about 1000° C. to about 1450° C.

Claim 46

42 . The method according to claim 35 further comprising the step of sintering said scintillator composition after firing to produce a sintered scintillator composition.

Claim 47

43 . The method according to claim 42 further comprising the step of annealing said sintered composition after sintering.

Claim 48

44 . A method for producing a shaped cerium-doped alkaline earth hafnium oxide scintillator that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof, said method comprising the steps of: providing a first solution that comprises amounts of compounds of at least cerium, hafnium, and said at least one alkaline earth metal; providing a second solution selected from the group consisting of ammonium hydroxide; alkyl esters of a di-carboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, and glutaric acid; amines selected from the group consisting of methanolamine, ethanolamine, propanolamine, dimethanolamine, diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, and tripropanolamine; and mixtures thereof; mixing together said first solution and said second solution to form a precipitate mixture of oxygen-containing compounds of at least cerium, hafnium, and said at least one alkaline earth metal; separating said precipitate mixture from a supernatant liquid; firing said precipitate mixture at a temperature and for a time sufficient to convert said precipitate mixture to a cerium-doped hafnium oxide; and hot isostatically pressing said cerium-doped hafnium oxide to form said shaped cerium-doped alkaline earth hafnium oxide scintillator; wherein amounts of compounds are chosen to obtain a final desired composition of said scintillator that is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 49

44 . A method for producing a shaped cerium-doped alkaline earth hafnium oxide scintillator that comprises at least one alkaline earth metal selected from the group consisting of barium, strontium, calcium, and combinations thereof, said method comprising the steps of: providing a first solution that comprises amounts of compounds of at least cerium, hafnium, and said at least one alkaline earth metal; providing a second solution selected from the group consisting of ammonium hydroxide; alkyl esters of a di-carboxylic acid selected from the group consisting of oxalic acid, malonic acid, succinic acid, and glutaric acid; amines selected from the group consisting of methanolamine, ethanolamine, propanolamine, dimethanolamine, diethanolamine, dipropanolamine, trimethanolamine, triethanolamine, and tripropanolamine; and mixtures thereof; mixing together said first solution and said second solution to form a precipitate mixture of oxygen-containing compounds of at least cerium, hafnium, and said at least one alkaline earth metal; separating said precipitate mixture from a supernatant liquid; firing said precipitate mixture at a temperature and for a time sufficient to convert said precipitate mixture to a cerium-doped hafnium oxide; and hot isostatically pressing said cerium-doped hafnium oxide to form said shaped cerium-doped alkaline earth hafnium oxide scintillator; wherein amounts of compounds are chosen to obtain a final desired composition of said scintillator that is capable of emitting visible light in response to an excitation of high-energy radiation selected from the group consisting of X, β, and γ radiation.

Claim 50

45 . The method according to claim 44 , wherein said first solution further comprises at least a compound of at least an ion selected from the group consisting of divalent ions, trivalent ions other than cerium, tetravalent ions, and combinations thereof.

Claim 51

46 . The method according to claim 44 , wherein said firing is followed by a step of calcining said cerium-doped alkaline earth hafnium oxide in a reducing atmosphere.

Claim 52

47 . The method according to claim 44 further comprising annealing said shaped cerium-doped alkaline earth hafnium oxide scintillator after the step of hot isostatically pressing.

Claim 53

48 . The method according to claim 46 further comprising annealing said cerium-doped alkaline earth hafnium oxide scintillator after the step of calcining and before the step of hot isostatically pressing.

Claim 54

49 . The method according to claim 44 , wherein said firing is conducted at a firing temperature in a range from about 900° C. to about 150° C.

Claim 55

50 . The method according to claim 44 , wherein said firing temperature is preferably in a range from about 1000° C. to about 1400° C.

Claim 56

51 . The method according to claim 46 , wherein said calcining temperature is conducted at a temperature in a range from about 1000° C. to about 1600° C.

Claim 57

52 . The method according to claim 44 , wherein said calcining temperature is preferably in a range from about 1000° C. to about 1500° C., more preferably from about 1000° C. to about 1450° C.

Claim 58

53 . A detector element of a positron emission tomography (“PET”) scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 1 .

Claim 59

54 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 3 .

Claim 60

55 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 6 .

Claim 61

56 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 7 .

Claim 62

57 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 8 .

Claim 63

58 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 10 .

Claim 64

59 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 12 .

Claim 65

60 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 17 .

Claim 66

61 . A detector element of a PET scanner comprising a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 19 .

Claim 67

62 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 1 .

Claim 68

63 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 3 .

Claim 69

64 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 6 .

Claim 70

65 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 7 .

Claim 71

66 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 8 .

Claim 72

67 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 10 .

Claim 73

68 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 12 .

Claim 74

69 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 17 .

Claim 75

70 . A PET scanner comprising an X-ray detector that comprises a cerium-doped alkaline earth hafnium oxide scintillator composition of claim 19.