EP0097295A1 — Rare earth doped yttria-gadolinia ceramic scintil…

Claim 1

Independent Claim 112 words

A polycristalline ceramic scintillator comprising between 5 and 50 mole percent Gd 2 O 3 , between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr2O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of C aO and SrO, the remainder being Y 2 0 3 .

Claim 2

Dependent Claim 112 words

A polycristalline ceramic scintillator comprising between 5 and 50 mole percent Gd 2 O 3 , between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr2O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of C aO and SrO, the remainder being Y 2 0 3 .

Claim 3

Dependent Claim 24 words

The polycristalline ceramic scintillator of claim 1 wherein said transparency promoter comprises between 0.2 and 0.7 mole percent ThO 2 or Zr0 2 .

Claim 4

Dependent Claim 23 words

The polycristalline ceramic scintillator of claim 1 wherein said transparency promoter comprises between 0.1 and 0.5 mole percent Ta 2 O 5 .

Claim 5

Dependent Claim 20 words

The polycristalline ceramic scintillator of claim 1 wherein said light output restorer comprises between 0.2 and 4 mole percent CaO.

Claim 6

Dependent Claim 82 words

A polycristalline ceramic scintillator comprising between 5 and 50 mole percent Gd 2 O 3 , at least one rare-earth activator oxide selected from the group consisting of Eu 2 0 31 Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb203, and Pr 2 O 3 and up to about 0.35 mole percent of a transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 .

Claim 7

Dependent Claim 82 words

A polycristalline ceramic scintillator comprising between 5 and 50 mole percent Gd 2 O 3 , at least one rare-earth activator oxide selected from the group consisting of Eu 2 0 31 Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb203, and Pr 2 O 3 and up to about 0.35 mole percent of a transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 .

Claim 8

Dependent Claim 21 words

The polycristalline ceramic scintillator of claims 1 or 5 comprising between 20 and 40 mole percent Gd 2 O 3 .

Claim 9

Dependent Claim 17 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 1 and 6 mole percent Eu203.

Claim 10

Dependent Claim 21 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 0.05 and 1.5 mole percent ND 2 O 3 .

Claim 11

Dependent Claim 21 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 0.1 and 0.5 mole percent Nd 2 O 3 .

Claim 12

Dependent Claim 22 words

The polycristalline ceramic scintallator of any of claims 1-6 comprising between 0.05 and 3 mole percent T b 2 0 3 .

Claim 13

Dependent Claim 22 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 0.1 and 2 mole percent Y b 2 0 3 .

Claim 14

Dependent Claim 21 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 0.03 and 1 mole percent Dy 2 O 3 .

Claim 15

Dependent Claim 22 words

The polycristalline ceramic scintillator of any of claims 1-6 comprising between 0.02 and 0.05 mole percent P r 2 0 3 .

Claim 16

Dependent Claim 20 words

The polycristalline ceramic scintillator of claim 1 wherein said light output restorer comprises between 0.1 and 3 mole percent SrO.

Claim 17

Independent Claim 151 words

A method for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , D Y 2 0 31 Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of Cao and SrO; pressing said multicomponent powder to form a powder compact: sintering said powder compact to the closed porosity stage; and pressing the sintered powder compact by the gas hot isostatic process to form said polycristalline ceramic scintillator body.

Claim 18

Independent Claim 151 words

A method for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 O 3 , Nd 2 O 3 , Yb 2 O 3 , D Y 2 0 31 Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , ZrO 2 , and Ta 2 O 5 , and at least one light output restorer selected from the group consisting of Cao and SrO; pressing said multicomponent powder to form a powder compact: sintering said powder compact to the closed porosity stage; and pressing the sintered powder compact by the gas hot isostatic process to form said polycristalline ceramic scintillator body.

Claim 19

Dependent Claim 170 words

A methode for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu203, Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta205, and a least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent powder being Y 2 0 3 ; pressing said multicomponent powder under vacuum at a first temperature and pressure for a first predetermined period of time; and increasing said first temperature and pressure to a second temperature and pressure and maintaining said second temperature and pressure for a second period of time to form said polycrystalline ceramic scintillator body.

Claim 20

Dependent Claim 170 words

A methode for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu203, Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta205, and a least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent powder being Y 2 0 3 ; pressing said multicomponent powder under vacuum at a first temperature and pressure for a first predetermined period of time; and increasing said first temperature and pressure to a second temperature and pressure and maintaining said second temperature and pressure for a second period of time to form said polycrystalline ceramic scintillator body.

Claim 21

Independent Claim 145 words

A method for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 0 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta205, and at least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent powder being Y 2 0 3 ; cold pressing said heated multicomponent powder to form a powder compact; and sintering said powder compact to form said polycristalline ceramic scintillator body.

Claim 22

Independent Claim 145 words

A method for preparing a polycristalline ceramic scintillator body comprising the steps of: preparing a multicomponent powder having between 5 and 50 mole percent Gd203, between 0.02 and 12 mole percent of at least one rare-earth activator oxide selected from the group consisting of Eu 2 0 3 , Nd 2 O 3 , Yb 2 O 3 , Dy 2 O 3 , Tb 2 O 3 , and Pr 2 O 3 , at least one transparency promoter selected from the group consisting of ThO 2 , Zr0 2 , and Ta205, and at least one light output restorer selected from the group consisting of CaO and SrO, the remainder of said multicomponent powder being Y 2 0 3 ; cold pressing said heated multicomponent powder to form a powder compact; and sintering said powder compact to form said polycristalline ceramic scintillator body.

Claim 23

Dependent Claim 21 words

The methode of any of claims 15-17 wherein said transparency promoter comprises between 0.2 and 0.7 mole percent Th0 2 .

Claim 24

Independent Claim 22 words

The method of any of claims 15-17 wherein said transparency promoter comprises between 0.2 and 0.7 mole percent Zr 0 2 .

Claim 25

Independent Claim 24 words

The method of any of claims 15-17 wherein said transparency promoter comprises between 0.1 and 0.5 mole percent T a 2 0 5 .

Claim 26

Independent Claim 23 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 20 and 40 mole percent Gd 2 O 3 .

Claim 27

Independent Claim 19 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.2 and 4 mole percent CaO.

Claim 28

Independent Claim 23 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 1 and 6 mole percent Eu 2 O 3 .

Claim 29

Independent Claim 23 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.05 and 1.5 mole percent Nd 2 0 3 .

Claim 30

Independent Claim 22 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.05 and 3 mole percent Tb 2 0 3.

Claim 31

Independent Claim 24 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.1 and 2 mole percent Y b 2 0 3 .

Claim 32

Independent Claim 23 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.03 and 1 mole percent Dy 2 O 3 .

Claim 33

Independent Claim 24 words

The method of any of claims 15-17 wherein said multicomponent powder comprises between 0.02 and 0.05 mole percent P r 2 0 3 .

Claim 34

Independent Claim 19 words

The method of any claims 15-17 wherein said light output restorer comprises between 0.1 and 3 mole percent SrO.

Claim 35

Independent Claim 57 words

The method of any of claims 15-17 wherein said step of preparing said multicomponent powder comprises mixing the high purity, micrometer-to-submicrometer powders of Gd 2 0 3 , Y 2 0 3 , at least one of said rare-earth activator oxides, at least one of said transparency promoters, and at least one of said light output restorers.

Claim 36

Independent Claim 76 words

The method of any of claims 15-17 wherein said step of preparing said multicomponent powder comprises the steps of: coprecipitating by the wet chemical oxalate process the oxalates of Y, Gd, and at least one of said rare-earth activator oxides; calcining said oxalates so as to obtain the corresponding oxides; and mixing at least one of said transparency promoters and at least one of said light output restorers with said oxides obtained in said calcining step.

Claim 37

Dependent Claim 34 words

The method of claim 31 wherein said step of calcining comprises the step of heating said oxalates in air at a temperature of between 700°C and 900°C for between 1 hour and 4 hours.

Claim 38

Dependent Claim 19 words

The method of claim 31 wherein said step of calcining is preceded by the step of milling said oxalates.

Claim 39

Independent Claim 22 words

The method of any of claims 31 or 33 further comprising the step of milling said oxides obtained in said calcining step.

Claim 40

Independent Claim 82 words

The method of any of claims 15, 30 or 31 wherein said step of pressing to form said powder compact comprises the steps of: cold pressing said multicomponent powder at a pressure of between 2.063 daN/mm 2 (3,000 psi) and 6.89 daN/mm 2 (10,000 psi) to form a preliminary powder compact; and then isostatically pressing said preliminary powder compact at a pressure of between 10.34 daN/mm 2 (15,000 psi) and 41.36 da N/mm 2 (60,000 psi) to increase the green density thereof.

Claim 41

Dependent Claim 29 words

The method of claim 35 wherein said step of sintering comprises heating said powder compact at a temperature of between 1500°C and 1700°C for between 1 and 10 hours.

Claim 42

Dependent Claim 57 words

The method of claim 36 wherein said step of pressing the sintered powder compact by the gas hot isostatic process comprises the step of heating at a temperatures of between 1500°C and 1800°C for between 1 and 2 hours at an argon gas pressure of between 0.689 daN/mm 2 (1,000 psi) and 20.68 daN/mm 2 (30,000 psi)

Claim 43

Dependent Claim 101 words

The method of claim 37 wherein said step of pressing the sintered powder compact by the gas hot isostatic process more specifically comprises the steps of: heating said powder compact for one hour to raise the temperature thereof to 1400°C, continue heating said powder compact for an additional one hour to raise the temperature thereof to 1750°C; and then maintaining the temperature of said powder compact at 1750°C for 1 hour prior to furnance-cooling said powder compact to room temperature, said steps of heating and maintaining the temperature being performed at an argon gas pressure of 17.225 daN/mm 2 (25,000 psi).

Claim 44

Independent Claim 61 words

The method of any of claims 16, 30 or 31 wherein said step of pressing comprises the step of pressing said multicomponent powder at a pressure of between 0.689 daN/mm 2 (1,000 psi) and 0.827 da N/mm 2 (1,200 psi) at a temperature of between 600°C and 700°C under a vacuum of up to 200 micrometers for up to 1 hour.

Claim 45

Dependent Claim 58 words

The method of claim 39 wherein said step of increasing said first temperature and pressure comprises increasing the temperature to between 1300°C and 1600°C, increasing the pressure to between 2,75 da N/ mm 2 (4,000 psi) and 6,89 da N/ mm 2 (10,000 psi), and maintaining said increased temperature and pressure for between one-half hour to 4 hours.

Claim 46

Dependent Claim 48 words

The methode of claim 40 further comprising the step of oxidizing the resulting hot pressed ceramic, said step of oxidizing including heating said ceramic in an oxygen-containing atmosphere for between 1 and 20 hours at a temperature of between 800°C and 1200°C so as to remove any discoloration.

Claim 47

Independent Claim 44 words

The method of any of claims 17, 30 or 31 wherein said step of cold pressing comprises the step of die pressing said multicomponent powder at a pressure of between 2.068 da N/mm 2 (3,000 psi) and 10.34 da N/ mm 2 (15,000 psi).

Claim 48

Dependent Claim 50 words

The method of claim 42 wherein said step of cold pressing further comprises the step of isostatically pressing the die pressed multicomponent powder at a pressure of between 6.89 da N/mm 2 (10,000 psi) and 41.36 daN/mm 2 (60,000 psi) to further increase the green density of said powder compact.

Claim 49

Dependent Claim 50 words

The method of claim 42 wherein said step of sintering comprises the steps of: heating said powder compact at a rate of between 100°C per hour and 700°C per hour to a sintering temperature of between 1800°C and 2100°C; and holding said sintering temperature for between 1 and 30 hours.

Claim 50

Dependent Claim 80 words

The method of claim 42 wherein said step of sintering comprises the steps of: heating said powder compact at a rate of between 300°C/hr and 400°C/hr to a holding temperature of between 1600°C and 1700°C; maintaining said holding temperature for between 1 and 20 hours and then increasing the temperature at a rate of between 25°C/hr and 75°C/hr to a final sintering temperature of between 1800°C and 2100°C; and maintaining the final sintering temperature for between 1 and 10 hours.

Claim 51

Dependent Claim 21 words

The method of claim 44 wherein said step of heating comprises heating said powder compact in vacuum or a reducing atmosphere.

Claim 52

Dependent Claim 30 words

.47. The method of claim 44 further comprising the step of cooling the resulting polycristalline ceramic scintillator body to room temperature over a period of between 2 and 10 hours.

Rare earth doped yttria-gadolinia ceramic scintillators and methods for making

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