# US 7,608,828 B2 · Solid solution material of rare earth element fluoride (polycrystal and single crystal), and method for preparation thereof, and radiation detector and test device

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- Number: US 7,608,828 B2
- Document ID: US7608828B2
- Status: Granted
- Kind: B2
- Application number: 11/578,248
- Filed: 2005-04-12
- Published: 2007-11-29
- Granted: 2009-10-27
- Earliest claimed: 2004-04-12
- Assignees: Stella Chemifa Corporation; Tohoku Techno Arch Co., Ltd.
- Inventors: Akira Yoshikawa; Kenji Aoki; Tomohiko Satonaga; Kei Kamada; Tsuguo Fukuda
- Web page: https://patentgrep.com/patent/US7608828B2

## CPC

- C09K 11/7719: {Halogenides (C09K11/7716 takes precedence)}
- C09K 11/7772: {Halogenides (C09K11/7767 takes precedence)}
- C30B 29/12: Halides
- 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)
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR
- G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES

## Abstract

A rare earth fluoride solid solution material (polycrystal and/or single crystal) characterized in that the material is obtained by mutually combining a plurality of rare earth fluorides having phase transitions and having different ion radii, respectively, so that the rare earth fluoride solid solution material is free of phase transitions. A rare earth fluoride solid solution material (polycrystal and/or single crystal) characterized in that the material is represented by (REyRE′1−y)F3 (0.0000<y<1.0000), wherein RE represents one or two or more selected from Sm, Eu, and Gd, and RE′ represents one or two or more selected from Er, Tm, Yb, Lu, and Y. A rare earth fluoride solid solution material (polycrystal and/or single crystal) represented by MxREyRE′1−x−yFz., wherein RE is one or two or more selected from Ce, Pr, Nd, Eu, Tb, Ho, Er, Tm, or Yb, RE′ is one or two or more selected from La, Sm, Gd, Dy, Lu, Y, and Sc, and M is one or more of Mg, Ca, Sr, and Ba.

## Claims

### Claim 1

A rare earth fluoride solid solution single crystal wherein said rare earth fluoride solid solution single crystal is represented by MxREyRE′1−x−yFz,
where RE is one or two or more selected from the group consisting of Ce, Pr, Nd, Eu, Tb, Ho, Er, Tm, and Yb,
RE′ is one or two or more selected from the group consisting of La, Sm, Gd, Dy, Lu, Y, and Sc,
M is one or more of Mg, Ca, Sr, and Ba,
0.0000<y<1.0000,
1.5000≦z≦3.5000, and
0.0000<x<0.1500.

### Claim 2 (depends on 1)

The rare earth fluoride solid solution single crystal of claim 1, wherein said rare earth fluoride solid solution single crystal has an absolute photoyield ratio between 1 inclusive and 25 exclusive, relative to BGO.

### Claim 3 (depends on 1)

The rare earth fluoride solid solution single crystal of claim 1, wherein said rare earth fluoride solid solution single crystal is a scintillator material where M is Sr.

### Claim 4

A rare earth fluoride solid solution single crystal wherein said rare earth fluoride solid solution single crystal is a rare earth fluoride solid solution material comprising a plurality of mutually combined rare earth fluorides having different ion radii, respectively;
wherein said rare earth fluoride solid solution material includes cations having an averaged ion radius which is in a size equal to or less than an ion radius of La3+ and larger than an ion radius of Sm3+, or in a size smaller than an ion radius of Gd3+ and larger than an ion radius of Er3+;
wherein said rare earth fluoride solid solution material includes Ce, and is free of primary phase transitions over a temperature range from room temperature to a melting point of said rare earth fluoride solid solution; and
wherein said rare earth fluoride solid solution single crystal includes an alkaline earth metal (AE) which is one or more of Mg, Ca, Sr, and Ba.

### Claim 5 (depends on 4)

The rare earth fluoride solid solution single crystal of claim 4, wherein the content of the alkaline earth metal is 0.0010 to 15.0000 (wt %).

### Claim 6

A rare earth fluoride solid solution single crystal wherein said rare earth fluoride solid solution single crystal is a rare earth fluoride solid solution material comprising a plurality of mutually combined rare earth fluorides having different ion radii, respectively;
wherein said rare earth fluoride solid solution material includes cations having an averaged ion radius which is in a size equal to or less than an ion radius of La3+ and larger than an ion radius of Sm3+, or in a size smaller than an ion radius of Gd3+ and larger than an ion radius of Er3+;
wherein said rare earth fluoride solid solution material includes Ce, and is free of primary phase transitions over a temperature range from room temperature to a melting point of said rare earth fluoride solid solution; and
wherein said rare earth fluoride solid solution material has fluorescence components at least one of which has a decay time of 50 nsec or shorter at a room temperature.

### Claim 7 (depends on 6)

The rare earth fluoride solid solution single crystal of claim 6, wherein the content of Ce is 0.0010 to 10.0000 (wt %).

### Claim 8 (depends on 6)

The rare earth fluoride solid solution single crystal of claim 6, wherein said rare earth fluoride solid solution single crystal has an absolute photoyield ratio between 1 inclusive and 25 exclusive, relative to Bi4Ge3O12 (BGO).

### Claim 9 (depends on 6)

The rare earth fluoride solid solution single crystal of claim 6, wherein an oxygen concentration is less than 10,000 wtppm.

### Claim 10 (depends on 9)

The rare earth fluoride solid solution single crystal of claim 9, wherein an oxygen concentration is less than 100 wtppm.

### Claim 11 (depends on 6)

A radiation detector wherein said radiation detector is provided by mutually combining:
a scintillator comprising the rare earth fluoride solid solution single crystal of claim 6; and
optical response means (photomultiplier tube (PMT), position sensitive photomultiplier tube (PSPMT), photodiode (PD), avalanche photodiode (APD), or the like).

### Claim 12 (depends on 11)

A radiographic inspection apparatus wherein said radiographic inspection apparatus is provided with the radiation detector of claim 11 as a radiation detector.

### Claim 13 (depends on 12)

The radiographic inspection apparatus of claim 12, wherein said rare earth fluoride solid solution single crystal has fluorescence components at least one of which has a decay time of 2 nsec or shorter at room temperature.

### Claim 14 (depends on 13)

The radiographic inspection apparatus of claim 13, wherein said radiographic inspection apparatus is a type of simplex form, or a type combined with either or both of MRI and CT.

### Claim 15 (depends on 13)

The radiographic inspection apparatus of claim 13 for a medical image processor, wherein said radiographic inspection apparatus is a type of simplex form, or a type combined with a magnetic resonance imaging (MRI), computed tomography (CT), single photon emission computed tomography (SPECT) apparatus, or a gamma camera, or any combination thereof.

### Claim 16 (depends on 13)

The radiographic inspection apparatus of claim 13, wherein said radiographic inspection apparatus is a positron emission tomography PET apparatus.

### Claim 17 (depends on 16)

The radiographic inspection apparatus of claim 16, wherein said PET is a two-dimensional PET, a three-dimensional PET, a time of flight (TOF) type PET, a depth of interaction (DOI) type PET, or any combination thereof.

### Claim 18 (depends on 17)

The radiographic inspection apparatus of claim 17, wherein said TOF type PET is combined with a position sensitive photomultiplier tube.

### Claim 19

A rare earth fluoride solid solution single crystal wherein said rare earth fluoride solid solution single crystal is represented by (REyRE′1−y)F3 (0.2<y<0.9), wherein RE represents one or two or more selected from the group consisting of Sm, Eu, and Gd, and RE′ represents one or two or more selected from the group consisting of Er, Tm, Yb, Lu, and Y, except for GdyY1−yF3, GdyEr1−yF3, and Gdy(YEr)1−yF3); and
wherein the solid solution material of rare earth element fluoride is free of primary phase transitions over a temperature range from room temperature to a melting point of said rare earth fluoride solid solution; and
wherein said rare earth fluoride solid solution material has fluorescence components at least one of which has a decay time of 50 nsec or shorter at a room temperature.

### Claim 20 (depends on 19)

The rare earth fluoride solid solution single crystal of claim 19, wherein said rare earth fluoride solid solution single crystal includes Ce.

### Claim 21

A rare earth fluoride solid solution single crystal wherein said rare earth fluoride solid solution single crystal is represented by (REyRE′1−y)F3 (0.0000<y<1.0000), where RE represents one or two or more selected from the group consisting of Sm, Eu, and Gd, and RE′ represents one or two or more selected from the group consisting of Er, Tm, Yb, Lu, and Y;
wherein said rare earth fluoride solid solution single crystal includes Ce, and is free of primary phase transitions over a temperature range from room temperature to a melting point of said rare earth fluoride solid solution; and
wherein said rare earth fluoride solid solution material has fluorescence components at least one of which has a decay time of 50 nsec or shorter at a room temperature.

### Claim 22 (depends on 21)

The rare earth fluoride solid solution single crystal of claim 21, wherein 0.2000≦y≦0.9000.

### Claim 23 (depends on 22)

The rare earth fluoride solid solution single crystal of claim 22, wherein 0.6≦y≦0.8.

### Claim 24 (depends on 21)

The rare earth fluoride solid solution single crystal of claim 21, wherein said rare earth fluoride solid solution single crystal is a scintillator material where RE is Gd, and RE′ is either or both of Lu and Y.

### Claim 25 (depends on 24)

The rare earth fluoride solid solution single crystal of claim 24, wherein said rare earth fluoride solid solution single crystal is a scintillator material where RE is Ce.

### Claim 26

A rare earth fluoride solid solution single crystal, wherein said rare earth fluoride solid solution single crystal is a single crystal and is represented by GdyY1−yF3, GdyEr1−yF3, or Gdy(YEr)1−yF3) 0.4≦y<0.6); and
wherein said rare earth fluoride solid solution single crystal includes Ce, and is free of primary phase transitions over a temperature range from room temperature to a melting point of said rare earth fluoride solid solution.

### Claim 27 (depends on 26)

The rare earth fluoride solid solution single crystal of claim 26, wherein said single crystal is grown by any one of a micro-pulling-down method, Czochralski method, Bridgman method, zone melt method, and Edge-defined Film-fed Growth Method (EFG method).