JP2012136667A - Luminescent material for scintillator, scintillator using the same, and radiation detector and radiation inspection apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescent material for a scintillator, which has an extremely short fluorescence lifetime of subnanoseconds, and to provide a scintillator, a radiation detector and a radiation inspection apparatus using the luminescent material.SOLUTION: There is provided the luminescent material for a scintillator represented by chemical formula: (RYb)O(wherein R is at least one element selected from rare earth elements consisting of Sc, Y and lanthanoid; and 0<x<0.1). The luminescent material for a scintillator generates fluorescence having an emission peak wavelength in the wavelength range of about 300-600 nm by exposure to radiation, has less absorption in the wavelength range of 300-530 nm which corresponds to the emission peak wavelength, and is transparent. The luminescent material for a scintillator comprises polycrystalline or monocrystalline. The scintillator is composed of the above luminescent material. A radiation detector 10 comprises a scintillator 13, and a light-receiving element 14 which receives fluorescence from the scintillator 13.

Description

  The present invention relates to a light emitting material for scintillators, a scintillator using the same, a radiation detector using the scintillator, and a radiation inspection apparatus.

  In image diagnosis based on nuclear decay events in high energy physics or positron emission tomography (PET), a collision of radiation generated by a nuclear decay event is detected by a scintillator to create an image or the like. Positrons are also called positrons.

  For example, in image diagnosis by the PET method, a positron-emitting drug is administered into a subject. A positron emitting pharmaceutical is a compound labeled with a positron emitting nuclide, and is produced by irradiating a compound with protons or deuterons with cycloton or the like. The positron emitting nuclide administered into the subject decays in the body and generates one positron. These positrons annihilate with the electrons of neighboring atoms. At this time, two opposite γ-rays having energy of 511 keV are generated by the interaction between the positron and the corresponding electron. The γ rays enter a scintillator crystal in the scintillator and are converted into light (photons). This light is detected by the light receiving element. In this way, light emitted from a specific position in the subject is converted into an electrical signal through the scintillator and detected. For example, a photodiode (PD) or a photomultiplier tube (PMT) is used as the light receiving element.

  Examination using PET is being used for diagnosis of clinical stage by diagnosis of tumor malignancy before treatment, detection of cancer invasion range and metastatic lesion. For example, in the case of cancer diagnosis, it is expected that accurate information will be obtained for judgment and evaluation of response to cancer treatment during treatment and immediately after treatment, prognosis prediction after treatment and recurrence diagnosis, etc. Is spreading.

  However, from the viewpoint of accurate diagnosis of the cancer infiltration range, there are disadvantages that an S / N ratio and resolution are poor only by an image obtained by normal PET, and accurate position information of a living organ or tissue is difficult to obtain.

Until now, materials used as light emitting materials for scintillators are materials using the 5d-4f transition of Ce ³⁺ (trivalent cerium ion) as represented by Ce: GSO, Ce: LSO, and Ce: YAP. Yes (see Non-Patent Document 1). A normal Ce-based scintillator crystal made of such a light emitting material for scintillator has a fluorescence lifetime of several tens of ns (see Non-Patent Document 2).

  In radiation detectors used for PET and the like, a radiation detector having a high response speed is required to reduce counting down. In particular, the PET apparatus is required to reduce the burden on the subject to be examined by shortening the examination time. Furthermore, a radiation detector used for PET or the like is required to have a high temporal resolution capable of preventing a phenomenon in which a plurality of fluorescences overlap, that is, a so-called pile-up phenomenon. As described above, in order to obtain a high response time and a high time resolution, a scintillator having a short fluorescence lifetime even with a low light emission amount and a light-receiving element having a high quantum conversion efficiency at the emission peak wavelength of the scintillator and a quick time response. There is a need for a combined, fast-response radiation detector.

However, since the general scintillator crystal described in Non-Patent Document 2 has a fluorescence lifetime of several tens of ns, a high-speed response of, for example, 1 ns or less has not been obtained. 1 ns is 10 ⁻⁹ seconds.

Patent Document 1 describes that the scintillator has a time resolution of 1 ns or less, but does not show the specific configuration of the scintillator and data related to the time response.

Special table 2008-536600 gazette Patent No. 3883106 Patent No. 4033451

Charles L. Melcher, “Scintillation Crystals for PET”, The Journal Of Nuclear Medicine, Vol.41, No.6, pp.1051-1055, June 2000 M. Nikl and 16 others, “An effect of Zr4 + co-doping of YAP: Ce scintillator”, Nuclear Instrument and Methods in Physics Research Section A, 486, pp. 250-253, 2002

In the conventional scintillator, an inorganic scintillator that includes a so-called effective atomic number Z _eff element as a structural constituent element of a mother crystal, which has high sensitivity to γ rays such as Lu, and exhibits a fluorescence lifetime of 1 ns or less to several ns seconds is used. There are no reports on radiation detectors. The time of 1 ns or less is also called sub-nanosecond.

  In view of the above problems, the present invention provides a scintillator light-emitting material that exhibits an extremely short fluorescence lifetime of sub-nanoseconds to 5 ns, a scintillator using the novel light-emitting material, and a radiation detector and a radiation inspection apparatus equipped with the scintillator The purpose is to provide.

  The present inventors have found that Yb mixed crystal rare earth oxide operates as a scintillator that responds at high speed at room temperature. By combining with an appropriate light receiving element, the present inventors realized a radiation detector with excellent characteristics and a high-speed response. The invention has been reached.

In order to achieve the first object, the light-emitting material for scintillators of the present invention has a chemical formula (R _1-X Yb _X ) ₂ O ₃ (where R is a rare earth element composed of Sc, Y, and a lanthanoid) One or more elements selected from the group consisting of 0 <x <0.1).
In the above configuration, the rare earth element is preferably one or more elements selected from Sc, Y, La, Gd, and Lu.
The scintillator light-emitting material preferably emits fluorescence having a light emission peak wavelength in a wavelength region of approximately 300 to 600 nm when irradiated with radiation.
The scintillator light-emitting material is preferably transparent with little absorption in the wavelength region of 300 to 530 nm corresponding to the emission peak wavelength.
The scintillator light-emitting material preferably emits fluorescence resulting from a transition from the charge transfer state (CTS) of Yb ³⁺ . The scintillator luminescent material is preferably made of polycrystal or crystal.

The scintillator light-emitting material of the present invention is characterized by being composed of any of the above-described scintillator light-emitting materials.
In the above configuration, the fluorescence lifetime at room temperature is preferably 5 ns or less.

A radiation detector according to the present invention includes a scintillator made of any one of the above-described scintillator light emitting materials and a light receiving element that receives fluorescence from the scintillator.
In the above configuration, the light receiving element is preferably any one of a photomultiplier tube, a photodiode, an avalanche photodiode, a Geiger mode avalanche photodiode, an image intensifier, and a charge coupled device.

A radiation inspection apparatus according to the present invention includes the radiation detector described above.
A method for producing a light-emitting material for scintillator according to the present invention is a method for producing a light-emitting material for scintillator according to any one of the above, wherein the raw material powder is molded by mixing the following R oxide powder and Yb oxide powder: A polycrystal of (R _1-X Yb _X ) ₂ O ₃ is produced by firing the molded body for a predetermined time.
In the above configuration, the oxide powder preferably has a BET specific surface area of 2 m ² / g or more and 15 m ² / g or less, and secondary aggregated particles exceeding 5 μm are 10% or less by mass fraction. It is good also considering the density of a molded object as 58% or more.
A single crystal of a light emitting material for scintillator may be grown using raw material powder having a composition represented by the chemical formula.

The scintillator luminescent material of the present invention has a chemical formula (R _1-X Yb _X ) ₂ O ₃ (where R is one or more elements selected from rare earth elements composed of Sc, Y, and lanthanoids). 0 <x <0.1) and exhibits an extremely short fluorescence lifetime of sub-nanoseconds to 5 ns, and can be applied to high-speed scintillators for radiation.

  According to the radiation detector of the present invention, since the high-speed scintillator and the light-receiving element having a high response speed are combined, high-speed response, high time resolution, and pile-up can be prevented. Less radiation can be detected with high accuracy.

  According to the radiation inspection apparatus of the present invention, since the radiation detector described above is provided, it can be applied to, for example, an image diagnostic apparatus using the PET method and can detect radiation with high accuracy.

It is a schematic diagram explaining CTS by Yb ion and O ion contained in the luminescent material for scintillators of the present invention. It is a schematic diagram which shows a micro pulling-down apparatus. It is sectional drawing which shows the structure of the radiation detector which concerns on the 1st Embodiment of this invention using the luminescent material for scintillators of this invention. It is a block diagram which shows the structure of the radiation inspection apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the modification of the radiographic inspection apparatus which concerns on the 2nd Embodiment of this invention. ₂ is an optical image showing transparency of a scintillator crystal made of (Lu _X0.99 Yb _0.01 ) ₂ O _{3 in} Example 1. FIG. It is a diagram showing the results of measurement of the absorption coefficient of the _{(Lu 1-X Yb X)} 2 O 3 (x = 0.003,0.01,0.03). It is a diagram showing the results of measuring the fluorescence intensity by radio luminescence _{(Lu 1-X Yb X)} 2 O 3 (x = 0.01). The _{(Lu 1-X} Yb _X) fluorescence decay time of 2 _{O 3,} shows the results of measurement by radio luminescence, (a) shows the x = 0.003, (b) is x = 0.01, ( c) is x = 0.03. Energy when detecting 0.66 MeV gamma ray from a ¹³⁷ Cs source using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and a photomultiplier tube of Example 1 It is a figure which shows wave height distribution. Energy when detecting 1.8 MeV β-rays from a ⁹⁰ Sr radiation source using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1 and a photomultiplier tube It is a figure which shows wave height distribution. Energy when using a radiation detector comprising a scintillator _{(Lu X0.997 Yb 0.003) 2 O} 3 and photomultiplier tubes of Example 1 ^was used to detect α rays 5.5MeV from ²⁴¹ Am-ray source It is a figure which shows wave height distribution. Energy wave height when detecting 0.66 MeV γ-ray from a ¹³⁷ Cs source using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and avalanche photodiode of Example 1 It is a figure which shows distribution. Energy wave height when detecting a 1.8 MeV β-ray from a ⁹⁰ Sr radiation source using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1 and an avalanche photodiode It is a figure which shows distribution. Using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1 and an avalanche photodiode, the energy wave height when detecting 5.5 MeV α-ray from a ²⁴¹ Am radiation source It is a figure which shows distribution. Using the radiation detector comprising the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1 and an avalanche photodiode, the energy wave height when detecting 5.5 MeV α-ray from a ²⁴¹ Am radiation source It is a figure which shows distribution. Using the radiation detector composed of the scintillator (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and Geiger mode avalanche photodiode of Example 1 when detecting 1.8 MeV β-ray from a ⁹⁰ Sr radiation source It is a figure which shows energy wave height distribution.

Hereinafter, several embodiments of the present invention will be specifically described with reference to the drawings.
The scintillator luminescent material according to the embodiment of the present invention has a chemical formula (R _1-X Yb _X ) ₂ O ₃ composition (where R is selected from rare earth elements composed of Sc, Y, and a lanthanoid). It is a transparent ceramic represented by 0 <x <0.1. Lanthanoids are elements having element numbers 57 to 71. The composition x of Yb serving as the emission center is set to be larger than 0 so that Yb is the emission center, and the upper limit is set to x <0.1. This is because, as will be described later, if there is too much CTS of Yb ³⁺ , concentration quenching occurs and the amount of light emission decreases.

  When irradiated with radiation, the scintillator luminescent material of the present invention generates fluorescence having an emission peak wavelength in a wavelength region of approximately 300 to 600 nm. This fluorescence is generated by Yb (an element that forms an optically active state called a charge transfer state (hereinafter referred to as CTS) with oxygen ions, which are adjacent anions in the light emitting material. It is based on interaction with ytterbium. In the present invention, radiation refers to particles (α rays, β rays, neutron rays, etc.) and photons (γ rays, X rays, etc.) having sufficient energy to ionize atoms and molecules.

R is one or more elements selected from rare earth elements composed of Sc (scandium), Y (yttrium), and lanthanoids. Preferably, one or more elements selected from Sc, Y, La (lanthanum), Gd (gadolinium), Lu (lutetium) and the like can be used.

In order to increase the amount of fluorescence generated from the light-emitting material for scintillator of the present invention, the composition x of the chemical formula (R _1-X Yb _X ) ₂ O ₃ is 0 <x <0.006, more preferably 0.001 <x <0.005 may be satisfied. It is not preferable that the composition x of Yb is less than 0.001, because the amount of CTS of Yb ^{3+ serving as} the emission center is too small and the emission amount is lowered. On the other hand, the upper limit is set to a value that does not cause a decrease in the amount of light emission due to Yb ³⁺ concentration quenching. In the case of light emission from Yb ³⁺ CTS, complete quenching is as high as several tens of percent. However, since the phenomenon in which the light emission amount of Yb ³⁺ begins to decrease is observed from a concentration of several percent, the Yb composition x may be smaller than 0.006 or smaller than 0.005.

  For high-speed response, 0.007 <x <0.1, more preferably 0.01 <x <0.05. The response speed is shorter than 1 ns.

FIG. 1 is a schematic diagram for explaining CTS by Yb ions contained in the light emitting material for scintillator of the present invention.
As shown in FIG. 1, Yb ³⁺ cations form an optically active state called CTS with oxygen ions, which are adjacent anions. When the scintillator is irradiated with radiation, the Yb ³⁺ cation shown on the left side of FIG. 1 interacts with surrounding O, and the electrons in the ground state 4f ¹³ 2P ⁶ are in the excited state 4f ¹⁴ 2P. ⁵ and excited to emit fluorescence in the process of relaxation (see right side of FIG. 1). Ce (see Non-Patent Documents 1 and 2), which is a conventional additive for a scintillator luminescent material, forms an excited state of a 5d-4f transition in its nucleus. However, in the case of light emission from CTS by Yb ions (Yb ³⁺ ) contained in the light-emitting material for scintillator of the present invention, CTS formed by the interaction between Yb ions and O is not in the Yb nucleus but in the excited state. There is light emission accompanying the transition from this state.

The fluorescence lifetime from CTS by Yb ³⁺ contained in the light emitting material for scintillator of the present invention is 100 to 300 ns at low temperature and 1 to 5 ns at room temperature. The fluorescence lifetime at room temperature from the CTS by Yb ³⁺ is about one order of magnitude faster than the conventional Ce ³⁺ fluorescence lifetime of 10 to 80 ns.

The wavelength range of fluorescence from CTS with Yb ³⁺ ranges from UV to red. The wavelength range of conventional Ce ³⁺ fluorescence is from UV to blue. From now on, since the fluorescence wavelength region from the light emitting material for scintillator according to the present invention is wider than the conventional Ce ³⁺ fluorescence wavelength region and covers visible light up to red, various semiconductor detectors described later are used for fluorescence detection. Can be used.

The CTS with Yb ³⁺ has a large Stokes shift, whereas the conventional Ce ³⁺ has a small Stokes shift.

According to the scintillator luminescent material of the present invention, the fluorescence lifetime at room temperature is shorter than 5 ns due to thermal quenching. According to (R _1-X Yb _X ) ₂ O ₃ of the present invention, the temperature dependence of the light emission amount depends on the composition other than Yb serving as the light emission center, that is, the host. For this reason, the fluorescence lifetime can be changed by combining with a host that exhibits a high light emission amount even at room temperature.

Table 1 summarizes the comparison between fluorescence lifetime, fluorescence wavelength region, Stokes shift, and concentration quenching in the 5d-4f transition of Cb and Ce ³⁺ of Yb ³⁺ according to the present invention.

  As the light emitting material for scintillator, a sintered body or a single crystal made of polycrystal can be used. A sintered body made of polycrystal is also simply called ceramics. A scintillator light-emitting material made of a polycrystalline sintered body can be produced by mixing raw materials, solidifying and firing this raw material powder. A single crystal of a scintillator luminescent material can be grown by a melt growth method such as the Bridgman method, the zone melt method, the Bernoulli method, the heat exchange method, the CZ method, the FZ method, or the micro-pulling down method. As the polycrystal used as the raw material of the single crystal, the same raw material as the polycrystal used as the light emitting material for the scintillator can be used.

(Production method of light emitting material for scintillator made of polycrystal)
As each raw material powder of (R _1-X Yb _X ) ₂ O ₃ (where R is one or more elements selected from rare earth elements composed of Sc, Y and lanthanoid), an oxide of R And ytterbium oxide (Yb ₂ O ₃ ) which is an oxide of Yb can be used. Examples of the oxide of R include scandium oxide (Sc ₂ O ₃ ) _, yttrium oxide (Y ₂ O ₃ ), and lanthanoid oxides. Examples of lanthanoid oxides include lutetium oxide (Lu ₂ O ₃ ) and gadolinium oxide (Gd ₂ O ₃ ).

Each raw material powder has a purity of 99.9% or more, a BET value (BET specific surface area) of 2 m ² / g or more and 15 m ² / g or less, and secondary aggregated particles exceeding 5 μm are 10% by mass fraction. The following. This raw material powder is molded to form a raw material powder compact. This raw material powder compact is sintered at a temperature of 1750 ° C. or lower, which is extremely lower than the melting point, to synthesize a translucent sintered body. In order to make the average particle diameter of the translucent sintered body 20 μm or less, it is necessary to produce a high-density molded body. The raw material powder compact before sintering may have a compact density of 58% or more empirically after degreasing.

When the BET value of the raw material powder exceeds 15 m ² / g, it is too fine to handle, and it is difficult to increase the density of the compact. Conversely, when the BET value of the raw material powder is less than 2 m ² / g, it is not preferable because it is not easy to densify at a low temperature. For this reason, from the viewpoint of sinterability, packing property, and ease of handling, the BET value of the raw material powder to be used is set to 2 m ² / g or more and 15 m ² / g or less. The BET value of the raw material powder is more preferably about 4 m ² / g or more and 8 m ² / g or less.

  The size of secondary agglomerated particles is also a problem for the production of a high-density molded body. There are voids in the secondary aggregated particles or between the secondary aggregated particles that are several μm larger than those produced by general molding. Such a large void is difficult to remove even if pressure sintering such as hot isostatic pressing (HIP) is performed, and causes a decrease in transmittance. Therefore, a secondary agglomerated particle exceeding 5 μm is preferably a raw material powder having a mass fraction of 10% or less, preferably 5% or less and a uniform particle size distribution. When the secondary agglomerated particles exceed 10% by mass fraction, a high-density molded body cannot be obtained, which is not preferable.

(Manufacturing method of light emitting material for scintillator made of single crystal)
A manufacturing method for growing a single crystal as a light emitting material for a scintillator with a micro-pulling-down apparatus will be described.
FIG. 2 is a schematic diagram showing the micro pull-down device 1. First, the configuration of the micro pulling device will be described. As shown in FIG. 2, the micro-pulling device 1 includes a crucible 3 that holds a melt 2 and a seed crystal that holds a seed crystal 4 a that is brought into contact with the melt 2 flowing out from a pore 3 a provided at the bottom of the crucible 3. A holding unit 4, a moving mechanism unit 5 that moves the seed crystal holding unit 4 downward, and an induction heating unit 6 that heats the crucible 3 are provided. Around the crucible 3, a heat insulating material 7 a made of zirconia or the like is disposed as the furnace material 7. The crucible 3 is accommodated in a crystal synthesis chamber 8 made of a quartz tube or the like disposed outside the heat insulating material 7. The crystal synthesis chamber 8 includes a vacuum exhaust unit 8a and a gas introduction unit 8b, and is a container that can be evacuated.

  The induction heating unit 6 that heats the crucible 3 includes an induction heating coil 6a that heats the crucible 3, an AC frequency power source (not shown) that supplies power to the induction heating coil 6a, and the like.

  The moving mechanism unit 5 includes a pulling shaft 5a that moves the seed crystal holding unit 4 downward, a moving mechanism 5b that moves the pulling shaft 5a in the vertical direction, and a moving mechanism control unit 5c. The moving mechanism control unit 5c performs position control of the pulling shaft 5a, speed control for moving the pulling shaft 5a downward during single crystal growth, and the like.

  An after heater 7 b as a heating element is disposed on the outer periphery of the bottom of the crucible 3. The heating temperature of the solid-liquid boundary phase of the melt 2 drawn from the pores provided at the bottom of the crucible 3 is controlled by the crucible 3 and the after heater 7b heated by the induction heating coil 6a.

Next, a method for growing a single crystal of (R _1-X Yb _X ) ₂ O ₃ using the micro-pulling device will be described.
The polycrystal of (R _1-X Yb _X ) ₂ O ₃ described above is put into the crucible 3 as a raw material, and the crystal synthesis chamber 8 is evacuated by the vacuum evacuation unit 8a. An inert gas Ar is introduced to make the inside of the crystal synthesis chamber 8 an inert gas atmosphere. The inert gas Ar (85 to 99%) may be a mixed gas in which hydrogen gas (H ₂ , 1 to 15%) is mixed to prevent oxidation of the crucible 3.
Next, the crucible 3 is heated by the induction heating coil 6a and the after heater 7b to completely melt the raw material in the crucible 3.

  The seed crystal 4a is gradually raised at a predetermined speed, and the tip of the seed crystal 4a is brought into contact with the pores at the lower end of the crucible 3 so that the seed crystal 4a is sufficiently adapted. Then, the single crystal 9 is grown by lowering the pulling shaft 5a while adjusting the melt temperature. When the melt 2 in the crucible 3 is all crystallized and the melt 2 is exhausted, the crystal growth is terminated.

  When the micro-pulling device 1 is used, the effective segregation coefficient at the time of single crystallization from the melt is close to 1, and the light emitting material for scintillator is compared with the case of using the conventional pulling method or Bridgman method. There is an advantage that variation in composition is reduced. Compared to the case where the single crystal growth of one composition in the case of using the conventional pulling method or Bridgman method takes one week, the micro pulling down method has the advantage that it takes 5 to 10 hours, and the single crystal can be obtained in a short time. Can do growth.

(Radiation detector)
Next, a radiation detector according to the first embodiment in which the scintillator luminescent material of the present invention is incorporated will be described.
FIG. 3 is a cross-sectional view showing the configuration of the radiation detector 10 according to the first exemplary embodiment of the present invention. As shown in FIG. 3, the radiation detector 10 of the present invention includes a chamber 12, a scintillator 13 accommodated in the chamber 12, a light receiving element 14 that detects fluorescence from the scintillator 13, and a reflector 15. It is configured. The light receiving element 14 is provided in contact with the lower surface of the scintillator 13. Except for the surface of the scintillator 13 that is in contact with the light receiving element 14, the fluorescent material may be covered with a reflector 15 so that the fluorescence does not leak outside the scintillator 13. Further, the light receiving element 14 includes a power connection terminal 14a to which power is supplied and an output terminal 14b.

The light receiving element 14 converts the fluorescence emitted from the scintillator 13 made of (R _1−X Yb _X ) ₂ O ₃ into an electrical signal. The material of the scintillator 13 made of (R _1-X Yb _X ) ₂ O ₃ is also called Yb mixed crystal rare earth oxide. The light receiving element 14 is preferably capable of detecting the emission peak wavelength of the scintillator 13, that is, the wavelength region of 300 to 600 nm, and has high quantum conversion efficiency. The quantum conversion efficiency is preferably 10% or more. As such a light receiving element 14, a photomultiplier tube (PMT), a photodiode (PD), an avalanche photodiode (APD), a Geiger mode avalanche photodiode (Geiger mode APD), an image intensifier (IIT), A charge coupled device (also referred to as a charge coupled device or CCD) can be used.

Examples of commercially available products that can be used for the light receiving element 14 include photomultiplier tubes, photodiodes, avalanche photodiodes, Geiger mode avalanche photodiodes, and the like manufactured by Hamamatsu Photonics. Each of these light receiving elements 14 can detect a wavelength region of 200 nm to 900 nm, and has a quantum conversion efficiency of 10% or more in a wavelength region of 300 nm to 600 nm.

The Yb mixed crystal rare earth oxide scintillator 13 has a fluorescence lifetime of 0.05 ns to 5 ns seconds due to light emission resulting from the transition from the charge transfer state (CTS) of Yb ³⁺ . The scintillator 13 made of Yb mixed crystal rare earth oxide has an emission peak wavelength in the range of 300 nm to 600 nm.

Next, the operation of the radiation detector 10 will be described.
In the radiation detector 10, when the radiation enters the Yb mixed crystal rare earth oxide scintillator 13, the Yb mixed crystal rare earth oxide scintillator 13 emits fluorescence, and the light receiving element 14 detects this fluorescence and converts it into an electrical signal. Output.

In the radiation detector 10, both the Yb mixed crystal rare earth oxide scintillator 13 and the light receiving element 14 have high-speed response in the sub-nanosecond range of 0.05 ns to 1 ns. Furthermore, since the Yb mixed crystal rare earth oxide scintillator 13 contains an element having a high effective atomic number Z _eff such as Lu as a constituent element of the mother crystal structure, it can detect radiation with high sensitivity and high accuracy. For this reason, the time resolution of the radiation detector 10 is also increased.
Thereby, the radiation detector 10 has high time resolution and can prevent pile-up. For this reason, counting down decreases.

(Radiation inspection equipment)
A radiation inspection apparatus 20 using the radiation detector 10 will be described as a second embodiment of the present invention.
FIG. 4 is a block diagram showing the configuration of the radiation inspection apparatus 20 according to the second embodiment of the present invention. As shown in FIG. 4, the radiation inspection apparatus 20 of the present invention includes the radiation detector 10 described above, a bias power source 22, a preamplifier 23, a waveform shaping amplifier 24, a multichannel analyzer 25, a computer 26, and a radiation detector. And a radiation source 30.
The bias power source 22 is connected to the power connection terminal 14 a of the light receiving element 14 in order to supply power to the radiation detector 10. The preamplifier 23 is connected to the output terminal 14b of the light receiving element 14, and amplifies the electric signal output from the light receiving element 14. The waveform shaping amplifier 24 is connected to the preamplifier 23, and shapes and further amplifies the signal waveform output from the preamplifier 23. The multi-channel analyzer 25 is connected to the waveform shaping amplifier 24 and receives a signal from the waveform shaping amplifier 24 to perform sampling, data storage, data display, and the like. A computer such as a personal computer (PC) can be used as the computer 26.

  The computer 26 is connected to the multi-channel analyzer 25 and can perform various arithmetic processes on the measurement data. Thereby, the radiation inspection apparatus 20 can detect the radiation from the radiation source 30 with the radiation detector 10, can preserve | save and analyze the detected data.

(Modification of radiation inspection equipment)
FIG. 5 is a block diagram showing a configuration of a modification of the radiation inspection apparatus 20 according to the second embodiment of the present invention.
As shown in FIG. 5, the radiation inspection apparatus 20 a of the present invention uses the light receiving element 14 of the radiation detector 10 as an image intensifier (IIT) 31, and further receives the output light from the image intensifier 31 by the CCD 32. The readout circuit 33 for reading out the output from the CCD is outputted to the personal computer 26. A high voltage power supply 34 is connected to the image intensifier 31 as a bias power supply. The readout circuit 33 includes an amplifier, an A / D converter that converts an amplified analog signal into a digital signal, and the like.

  The radiation inspection apparatuses 20 and 20a can configure, for example, PET, X-ray CT, SPECT (single photon emission tomography), etc., depending on the radiation source 30 used. The radiation inspection apparatuses 20 and 20a are not particularly limited when made of PET, but are MRI-PET, CT-PET, two-dimensional PET, three-dimensional PET, time-of-flight positron emission apparatus (TOF type PET). It is preferably made of a depth detection (DOI) type PET or OPEN-PET. Furthermore, the radiation inspection apparatuses 20 and 20a may be configured by a combination of these.

In particular, TOF type PET, which is currently expected to be realized, differs from the conventional two scintillators, that is, a method of detecting with equal probability on a straight line (LOR) connecting both detectors. The coordinate point of the radiation source 30 is obtained from the difference in measurement time, and the distribution blurred with a Gaussian function corresponding to the time resolution of the detector along the LOR is used as position information. For this reason, the response speed of the conventional scintillator has a position identification capability of less than 100 cm.
In contrast, in the radiation inspection apparatus 20 using the scintillator 13 made of the Yb mixed crystal rare earth oxide of the present invention, the fluorescence lifetime of the scintillator 13 is about an order of magnitude faster than that of the conventional scintillator. A position identification capability of several centimeters can be provided, and high performance can be achieved.

Since the radiation inspection apparatus 20 includes the radiation detector 10 having a high-speed response, the data acquisition time can be greatly shortened. For this reason, by using the radiation inspection apparatus 20 for a medical imaging apparatus or the like, the inspection time can be shortened, and the burden on the subject can be greatly reduced.
Hereinafter, the present invention will be described in more detail by way of examples.

As Example 1, a scintillator crystal made of (Lu _1-X Yb _X ) ₂ O ₃ (x = 0.003, 0.01, 0.03) was produced.
Ultrapure water was added to a high-purity lutetium chloride solution (Shin-Etsu Chemical Co., Ltd.) having a purity of 99.99% to prepare an aqueous lutetium chloride solution having a concentration of 0.5 M (mol · dm ⁻³ ). 5 liters of this solution was placed in a polytetrafluoroethylene container and stirred. To a lutetium chloride aqueous solution, 2 liters of an ammonium hydrogen carbonate solution having a concentration of 3 M (mol · dm ⁻³ ) was dropped at a rate of 5 ml per minute, followed by stirring and curing at room temperature for 7 days. After curing, filtration and washing with ultrapure water were repeated several times, and then put into a dryer at 150 ° C. and dried for 3 days to prepare a precursor powder. The obtained precursor powder is put into an alumina crucible and calcined in an electric furnace at 1200 ° C. for 10 hours, whereby lutetium oxide having a BET specific surface area value of 5.0 m ² / g and an average primary particle size of 0.13 μm. Raw material powder was prepared.

As a peptizer, 0.297 g of ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ^{2 /} g) is added to 100.0 g of lutetium oxide raw material powder. 2 g of Kyoeisha Chemical's Floren G700 (Floren is a trade name of Kyoeisha Chemical) and 0.5 g of Sekisui Chemical PVB-BL1 (PVB-BL1 is a trade name of Sekisui Chemical) were added as a binder. Ethanol 35g was added to this mixture, and it mixed for 50 hours using the nylon pot and the nylon ball, and was set as the alcohol slurry.
Next, the molded article was produced by pouring the alcohol slurry into a gypsum mold and curing for 3 days. When the composition of Yb _x is changed, the amount of the ytterbium oxide raw material powder may be adjusted. When x is 0.01, the amount of the ytterbium oxide raw material powder is 0.99 g.

The molded body was heated at 5 ° C./hour in an oxygen stream, and degreased at 900 ° C. for 40 hours. The composition ratio of the compact was determined by ICP (inductively coupled plasma) emission spectrometry, and was (Lu _0.997 Yb _0.003 ) ₂ O ₃ .

In order to sufficiently perform the degreasing treatment, the compact was further heated to 1200 ° C. and held for 10 hours.
Then, it sintered for 10 hours at the temperature of 1650 degreeC in the vacuum baking furnace. At this time, the heating rate was 300 ° C./hour up to 1200 ° C., 50 ° C./hour above that, and the degree of vacuum in the furnace was 10 ⁻² Pa or less.
Next, the obtained sintered body was annealed in the atmosphere at 900 ° C. for 50 hours, and then mirror-polished using a diamond slurry to produce a transparent polycrystalline ceramic.

FIG. 6 is an optical image showing the transparency of the scintillator crystal made of (Lu _X0.99 Yb _0.01 ) ₂ O _{3 in} Example 1. As can be seen from FIG. 6, since the lower pattern of the scintillator crystal made of (Lu _X0.99 Yb _0.01 ) ₂ O _{3 of} Example 1 is seen through, it can be seen that the scintillator crystal is highly transparent.

FIG. 7 is a diagram showing the results of measuring the absorption coefficient of (Lu _1-X Yb _X ) ₂ O ₃ (x = 0.003, 0.01, 0.03). FIG. 7 also shows Lu ₂ O ₃ data to which Yb is not added for comparison. As is apparent from FIG. 7, it can be seen that there is no absorption in the vicinity of 300 to 530 nm, which is the emission peak due to the transition from the charge transfer state (CTS) of Yb ³⁺ .

FIG. 8 is a diagram illustrating a result of measuring the fluorescence intensity of (Lu _1-X Yb _X ) ₂ O ₃ (x = 0.01) by radioluminescence. In FIG. 8, the horizontal axis represents wavelength (nm) and the vertical axis represents fluorescence intensity (arbitrary scale). As is clear from FIG. 8, the fluorescence intensity spectrum has two peaks characteristic of the emission peak caused by the transition from the charge transfer state (CTS) of Yb ³⁺ near 370 nm and 480 nm. I understand that.

FIG. 9 is a diagram showing the results of measuring the fluorescence decay time of (Lu _1-X Yb _X ) ₂ O ₃ by radioluminescence, where (a) is x = 0.003 and (b) is x = 0. .01, (c) where x = 0.03. The horizontal axis of FIG. 9 is time (ns), and the vertical axis is the fluorescence count.
As can be seen from FIG. 9, these scintillators 13 have an extremely short sub-nanosecond fluorescence lifetime of 0.8 ns. As shown in FIG. 9B, the scintillator 13 made of (Lu _X0.99 Yb _0.01 ) ₂ O ₃ has a light emission amount of about 1000 photons / MeV.

(Radiation detector)
Using the scintillator 13 of Example 1, the radiation detector 10 was manufactured. As the reflecting member 14 covering the scintillator 13, a fluororesin tape was used. As the light receiving element 14, a photomultiplier tube, an avalanche photodiode, or a Geiger mode avalanche photodiode was used. As shown in FIG. 9, the radiation detector 10 has a light emission amount of about 1000 photons / MeV when a photomultiplier tube is used as the light receiving element 14.

(Radiation inspection equipment)
A radiation inspection apparatus 20 was manufactured using the radiation detector 10 of Example 2. The radiation inspection apparatus 20 has the configuration shown in FIG. As a radiation source 30, a γ ray having an energy of 0.66 MeV from a ¹³⁷ Cs source, a β ray having an energy of 1.8 MeV from a ⁹⁰ Sr source, from a ²⁴¹ Am source Α rays with an energy of 5.5 MeV were used.

An example of measurement using the radiation detector 10 using a photomultiplier tube as the light receiving element 14 will be described.
FIG. 10 shows a 0.66 MeV gamma ray from a ¹³⁷ Cs radiation source using the radiation detector 10 comprising the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and a photomultiplier tube of Example 1. It is a figure which shows energy wave height distribution when detecting. The horizontal axis in FIG. 10 is the channel, and the vertical axis is the fluorescence count in each channel. The display in FIGS. 11 to 17 described later is also the same.
As shown in FIG. 10, the radiation detector 10 was able to detect 0.66 MeV γ rays from a ¹³⁷ Cs radiation source with high sensitivity by using a photomultiplier tube as the light receiving element 14.

FIG. 11 shows a β-ray of 1.8 MeV from a ⁹⁰ Sr radiation source using the radiation detector 10 composed of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and a photomultiplier tube of Example 1. It is a figure which shows energy wave height distribution when detecting. As shown in FIG. 11, the radiation detector 10 was able to detect 1.8 MeV β-rays from a ⁹⁰ Sr radiation source with high sensitivity using a photomultiplier tube as the light receiving element 14.

FIG. 12 shows a 5.5 MeV alpha ray from a ²⁴¹ Am radiation source using the radiation detector 10 comprising the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and a photomultiplier tube of Example 1. It is a figure which shows energy wave height distribution when detecting. As shown in FIG. 12, the radiation detector 10 was able to detect the 5.5 MeV α ray from the ²⁴¹ Am ray source with high sensitivity by using a photomultiplier tube as the light receiving element 14.

Next, a measurement example of the radiation detector 10 using an avalanche photodiode as the light receiving element 14 will be described.
FIG. 13 shows a case in which 0.66 MeV γ-rays from a ¹³⁷ Cs radiation source are obtained using the radiation detector 10 composed of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and an avalanche photodiode in Example 1. It is a figure which shows energy wave height distribution when it detects. In FIG. 13, the γ-ray signal is shown by a straight line, and the gentle slope in the figure is a γ-ray direct detection signal by an avalanche photodiode. As shown in FIG. 13, the radiation detector 10 was able to detect 0.66 MeV γ rays from a ¹³⁷ Cs source with high sensitivity by using an avalanche photodiode as the light receiving element 14.

FIG. 14 shows a case where 1.8 MeV β-rays from a ⁹⁰ Sr radiation source are obtained using the radiation detector 10 composed of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and an avalanche photodiode in Example 1. It is a figure which shows energy wave height distribution when it detects. As shown in FIG. 14, the radiation detector 10 was able to detect 1.8 MeV β-ray from a ⁹⁰ Sr radiation source with high sensitivity by using an avalanche photodiode as the light receiving element 14.

FIG. 15 shows a case where 5.5 MeV α rays from a ²⁴¹ Am radiation source are obtained using the radiation detector 10 made of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and an avalanche photodiode according to the first embodiment. It is a figure which shows energy wave height distribution when it detects. As shown in FIG. 15, the radiation detector 10 can detect the 5.5 MeV α ray from the ²⁴¹ Am radiation source with high sensitivity by using an avalanche photodiode as the light receiving element 14.

Next, a measurement example of the radiation detector 10 using a Geiger mode avalanche photodiode as the light receiving element 14 will be described.
FIG. 16 shows a 5.5 MeV α from a ²⁴¹ Am radiation source using the radiation detector 10 composed of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and Geiger mode avalanche photodiode of Example 1. The energy wave height distribution when a line is detected is shown. As shown in FIG. 16, the radiation detector 10 was able to detect the 5.5 MeV α ray from the ²⁴¹ Am radiation source with high sensitivity by using a Geiger mode avalanche photodiode as the light receiving element 14.

FIG. 17 shows a 1.8 MeV β from a ⁹⁰ Sr source using the radiation detector 10 composed of the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O ₃ and Geiger mode avalanche photodiode of Example 1. The energy wave height distribution when a line is detected is shown. As shown in FIG. 17, the radiation detector 10 was able to detect 1.8 MeV β-ray from a ⁹⁰ Sr radiation source with high sensitivity by using a Geiger mode avalanche photodiode as the light receiving element 14.

In the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1, the characteristics of the radiation detector 10 were the same even if the light receiving element 14 was replaced with IIT and CCD. From the above measurement, in the scintillator 13 (Lu _X0.997 Yb _0.003 ) ₂ O _{3 of} Example 1, the light receiving peak wavelength is 360 to 370 nm, the light emission amount is 1500 photons / MeV, and the fluorescence lifetime is 1 ns. It was about.

As Example 4, a fluorescent material having a blending ratio of (Lu _0.99 Sc _0.007 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and the ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) prepared in Example 1 and scandium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) was weighed so as to have a composition ratio of (Lu _0.99 Sc _0.007 Yb _0.003 ) ₂ O ₃ Thereafter, they were mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours, thereby comprising (Lu _0.99 Sc _0.007 Yb _0.003 ) ₂ O _{3 of} Example 4. A transparent polycrystalline ceramic was produced. Next, a radiation detector 10 using this transparent polycrystalline ceramic was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 4, the light receiving peak wavelength was 360 to 370 nm, the light emission amount when irradiated with γ rays was 1800 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 5, a fluorescent material having a blending ratio of (Lu _0.99 Y _0.007 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and yttrium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) prepared in Example 1 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) was weighed so as to have a composition ratio of (Lu _0.99 Y _0.007 Yb _0.003 ) ₂ O ₃ Thereafter, they were mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours, thereby comprising (Lu _0.99 Y _0.007 Yb _0.003 ) ₂ O _{3 of} Example 5. A transparent polycrystalline ceramic was produced. Next, a radiation detector 10 using this transparent polycrystalline ceramic was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 5, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1400 photons / MeV, and the fluorescence lifetime was about 1 ns.

As Example 6, a fluorescent material having a blending ratio of (Lu _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ was produced.
Lutetium oxide raw material powder and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) and gadolinium oxide raw material powder (Shin-Etsu Chemical Industry) Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) was weighed so as to have a composition ratio of (Lu _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ Then, it mixed and it was set as the raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours, thereby comprising (Lu _0.99 Gd _0.007 Yb _0.003 ) ₂ O _{3 of} Example 6. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 6, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1500 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 7, a fluorescent material having a blending ratio of (Lu _0.99 La _0.007 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and the lanthanum oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) prepared in Example 1 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) was weighed so as to have a composition ratio of (Lu _0.99 La _0.007 Yb _0.003 ) ₂ O ₃ Then, it mixed and it was set as the raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours, thereby comprising (Lu _0.99 La _0.007 Yb _0.003 ) ₂ O _{3 of} Example 6. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 7, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1000 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 8, a fluorescent material having a blending ratio of (Lu _0.99 Sc _0.003 Y _0.004 Yb _0.003 ) ₂ O ₃ was produced.
Lutetium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) and yttrium oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Sc _0.003 Y _0.004 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. The raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Sc _0.003 Y _0.004 Yb _0.003 ) _{2 of} Example 6. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 8, the light receiving peak wavelength was 360 to 370 nm, the light emission amount was 1700 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 9, a fluorescent material having a blending ratio of (Lu _0.99 Sc _0.003 Gd _0.004 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) and gadolinium oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Sc _0.003 Gd _0.004 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Sc _0.003 Gd _0.004 Yb _0.003 ) _{2 of} Example 9. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 9, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1600 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 10, a fluorescent material having a blending ratio of (Lu _0.99 Sc _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ was produced.
Lutetium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) and lanthanum oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Sc _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Sc _0.005 La _0.002 Yb _0.003 ) _{2 of} Example 10. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

In the scintillator 13 of Example 10, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1400 photons / MeV, and the fluorescence lifetime was about 1.7 ns.

As Example 11, a fluorescent material having a blending ratio of (Lu _0.99 Y _0.004 Gd _0.003 Yb _0.003 ) ₂ O ₃ was produced.
Lutetium oxide raw material powder and yttrium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) and gadolinium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Y _0.004 Gd _0.003 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. The raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Y _0.004 Gd _0.003 Yb _0.003 ) _{2 of} Example 11. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 11, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1500 photons / MeV, and the fluorescence lifetime was about 1 ns.

As Example 12, a fluorescent material having a blending ratio of (Lu _0.99 Y _0.005 La _0.02 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and yttrium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) and lanthanum oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Y _0.005 La _0.02 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Y _0.005 La _0.02 Yb _0.003 ) _{2 of} Example 12. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 12, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1400 photons / MeV, and the fluorescence lifetime was about 1 ns.

As Example 13, a fluorescent material having a blending ratio of (Lu _0.99 Gd _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ was produced.
The lutetium oxide raw material powder and gadolinium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) and lanthanum oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 1 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Lu _0.99 Gd _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ and mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1650 ° C. for 10 hours to obtain (Lu _0.99 Gd _0.005 La _0.002 Yb _0.003 ) _{2 of} Example 13. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 13, the light receiving peak wavelength was 360 to 370 nm, the light emission amount was 1500 photons / MeV, and the fluorescence lifetime was about 1 ns.

Table 2 summarizes the emission peak wavelength, emission amount, and fluorescence lifetime when the radiation detector 10 using the scintillators 13 of Examples 3 to 13 is irradiated with γ rays.

As Example 14, a fluorescent material with a blending ratio of (Gd _0.997 Yb _0.003 ) ₂ O ₃ was produced.
The single crystal for the scintillator 13 was produced using a micro pulling method. As the melt, a mixture of oxide powders of Gd ₂ O ₃ and Yb ₂ O ₃ was used so that the single crystal had a composition ratio of (Gd _0.997 Yb _0.003 ) ₂ O ₃ . That is, an oxide powder raw material having a purity of 99.99% was prepared, and Re metal was used as a crucible. As the atmosphere, a mixed gas composed of Ar (97%) gas and H ₂ (3%) gas was used. A single crystal having the same composition as the single crystal to be produced was cut in the [111] direction to obtain a seed crystal. The solid-liquid interface was observed with a CCD camera to determine the appropriate temperature and crystal production rate. A typical condition for the crystal production speed was 0.05 to 0.1 mm / min.

The radiation detector 10 using the scintillator 13 made of (Gd _0.997 Yb _0.003 ) ₂ O ₃ was manufactured, incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3. In the scintillator 13 of Example 14, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1600 photons / MeV, and the fluorescence lifetime was about 1 ns. In the scintillator 13 of Example 14, Lu in Example 3 is replaced with Gd, but the received light peak wavelength is 360 to 370 nm as in Example 3. Furthermore, the light emission amount and fluorescence lifetime of Example 14 were the same as those of Example 3.

As Example 15, a fluorescent material having a blending ratio of (Gd _0.947 Sc _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In Example 15, the radiation detector 10 using the scintillator 13 made of (Gd _0.947 Sc _0.05 Yb _0.003 ) ₂ O ₃ was manufactured in the same manner as in Example 14, and incorporated in the radiation inspection apparatus 20. The characteristics of the scintillator 13 were measured in the same manner as in Example 3. In the scintillator 13 of Example 15, the light receiving peak wavelength was 360 to 370 nm, the light emission amount was 1800 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 16, a fluorescent material having a blending ratio of (Gd _0.947 Y _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In Example 16, the radiation detector 10 using the scintillator 13 made of (Gd _0.947 Y _0.05 Yb _0.003 ) ₂ O ₃ was produced in the same manner as in Example 14, and incorporated in the radiation inspection apparatus 20. The characteristics of the scintillator 13 were measured in the same manner as in Example 3. In the scintillator 13 of Example 16, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1600 photons / MeV, and the fluorescence lifetime was about 1 ns.

As Example 17, a fluorescent material having a blending ratio of (Gd _0.947 La _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In Example 17, the radiation detector 10 using the scintillator 13 made of (Gd _0.947 La _0.05 Yb _0.003 ) ₂ O ₃ was manufactured in the same manner as in Example 14, and incorporated in the radiation inspection apparatus 20. The characteristics of the scintillator 13 were measured in the same manner as in Example 3. In the scintillator 13 of Example 17, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1200 photons / MeV, and the fluorescence lifetime was about 1 ns. Table 3 summarizes the emission peak wavelength, emission amount, and fluorescence lifetime when the radiation detector 10 using the scintillators 13 of Examples 14 to 17 is irradiated with γ rays.

As Example 18, a fluorescent material having a blending ratio of (La _0.997 Yb _0.003 ) ₂ O ₃ was produced.
In Examples 18 to 21, polycrystal was used as in Example 1. In Example 18, the radiation detector 10 using the scintillator 13 made of (La _0.997 Yb _0.003 ) ₂ O ₃ is manufactured and incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 are the same as in Example 3. Was measured. In the scintillator 13 of Example 18, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 200 photons / MeV, and the fluorescence lifetime was about 1 ns. In the scintillator 13 of Example 14, Lu in Example 3 is replaced with La, but the received light peak wavelength is 360 to 370 nm as in Example 3. Further, the light emission amount of Example 14 was about 13% of Example 3, but the fluorescence lifetime was the same as that of Example 3.

As Example 19, a fluorescent material having a blending ratio of (La _0.947 Sc _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In the nineteenth embodiment, the radiation detector 10 using the scintillator 13 made of (La _0.947 Sc _0.05 Yb _0.003 ) ₂ O ₃ is manufactured and incorporated in the radiation inspection apparatus 20, similarly to the third embodiment. The characteristics of the scintillator 13 were measured. In the scintillator 13 of Example 19, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 400 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 20, a fluorescent material having a blending ratio of (La _0.947 Y _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In Example 20, the radiation detector 10 using the scintillator 13 made of (La _0.947 Y _0.05 Yb _0.003 ) ₂ O ₃ is manufactured and incorporated in the radiation inspection apparatus 20, similarly to Example 3. The characteristics of the scintillator 13 were measured. In the scintillator 13 of Example 20, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 300 photons / MeV, and the fluorescence lifetime was about 1 ns.

As Example 21, a fluorescent material having a blending ratio of (La _0.947 Gd _0.05 Yb _0.003 ) ₂ O ₃ was produced.
In Example 21, the radiation detector 10 using the scintillator 13 made of (La _0.947 Gd _0.05 Yb _0.003 ) ₂ O ₃ was manufactured and incorporated in the radiation inspection apparatus 20, as in Example 3. The characteristics of the scintillator 13 were measured. In the scintillator 13 of Example 21, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 300 photons / MeV, and the fluorescence lifetime was about 1 ns. Table 4 summarizes the emission peak wavelength, emission amount, and fluorescence lifetime when the radiation detector 10 using the scintillators 13 of Examples 18 to 21 is irradiated with γ rays.

As Example 22, a fluorescent material having a blending ratio of (Sc _0.997 Yb _0.003 ) ₂ O ₃ was produced.
First, a scandium oxide raw material powder was produced (see Patent Document 2, paragraph [0040]). Scandium oxide having a purity of 99.9% or more and Si of 5 ppm was dissolved in hydrochloric acid to prepare an aqueous scandium chloride solution having a concentration of 0.25 M (mol · dm ⁻³ ). 500 ml of this solution was placed in a polytetrafluoroethylene beaker and stirred. A 0.5M (mol · dm ⁻³ ) ammonium hydrogen carbonate solution was dropped into an aqueous scandium chloride solution at a rate of 5 ml / min until pH 8.0 was reached, followed by curing at room temperature for 10 days. . After curing, filtration and washing with ultrapure water were repeated several times, and then placed in a dryer at 150 ° C. and dried for 2 days. The obtained precursor powder was put into an alumina crucible and calcined (1250 ° C. × 3 hours) in an electric furnace to prepare a scandium oxide raw material powder having an average primary particle size of 0.35 μm.

Next, scandium oxide raw material powder and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity: 99.99%, BET specific surface area value: 2.7 m ² / g) are used as (Sc _0.997 Yb _0.003). ) Weighed so as to have a composition ratio of ₂ O ₃ and mixed to obtain a raw material mixed powder. The raw material mixed powder was treated in the same manner as in Example 1 and subjected to vacuum baking at 1700 ° C. for 5 hours, whereby the scintillator 13 made of (Sc _0.997 Yb _0.003 ) ₂ O _{3 of} Example 22 was obtained. Produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 22, the light receiving peak wavelength was 360 to 370 nm, the light emission amount was 2000 photons / MeV, and the fluorescence lifetime was about 2 ns. In the scintillator 13 of Example 22, Lu in Example 3 is replaced with Sc, but the received light peak wavelength is 360 to 370 nm as in Example 3. Furthermore, the light emission amount of Example 22 was about 133% of Example 3, but the fluorescence lifetime was 2 ns, about twice that of Example 3.

As Example 23, a fluorescent material having a blending ratio of (Sc _0.99 Y _0.007 Yb _0.003 ) ₂ O ₃ was produced.
Scandium oxide raw material powder and yttrium oxide raw material powder produced in Example 22 (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) and ytterbium oxide (Shin-Etsu Chemical Co., Ltd.) ), Purity 99.99%, BET specific surface area value 2.7 m ² / g), and weighed so as to have a composition ratio of (Sc _0.99 Y _0.007 Yb _0.003 ) ₂ O ₃ And mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1700 ° C. for 5 hours to be made of (Sc _0.99 Y _0.007 Yb _0.003 ) ₂ O _{3 of} Example 23. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 23, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1800 photons / MeV, and the fluorescence lifetime was about 1.8 ns.

As Example 24, a fluorescent material having a blending ratio of (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ was produced.
Scandium oxide raw material powder and yttrium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) prepared in Example 22 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) is weighed so as to have a composition ratio of (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ And mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1700 ° C. for 5 hours to be composed of (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O _{3 of} Example 24. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 24, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1800 photons / MeV, and the fluorescence lifetime was about 2 ns.

As Example 25, a fluorescent material having a blending ratio of (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ was produced.
Scandium oxide raw material powder and yttrium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.5 m ² / g) prepared in Example 22 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) is weighed so as to have a composition ratio of (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ And mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1700 ° C. for 5 hours, thereby comprising (Sc _0.99 Gd _0.007 Yb _0.003 ) ₂ O _{3 of} Example 25. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 25, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 1600 photons / MeV, and the fluorescence lifetime was about 2 ns.

Table 5 summarizes the emission peak wavelength, emission amount, and fluorescence lifetime when the radiation detector 10 using the scintillators 13 of Examples 22 to 25 is irradiated with γ rays.

As Example 26, a fluorescent material having a blending ratio of (Y _0.997 Yb _0.003 ) ₂ O ₃ was produced.
First, as described in paragraph [0037] of Patent Document 3 where an yttrium oxide raw material powder was prepared, an average primary particle diameter of 0.3 μm and a purity of 99.9 were based on the technique of JP-A-11-157933. % Or more, Si 3 wtppm yttrium oxide raw material powder was produced.
That is, an aqueous solution of yttrium nitrate, an aqueous solution of urea, and an aqueous solution of ammonium sulfate were mixed to give a yttrium: urea: ammonium sulfate molar ratio of 1: 6: 1 and hydrothermally reacted in an autoclave at 125 ° C. for 2 hours. Carbonate was obtained. The obtained carbonate was washed with pure water and dried.
Next, this dry powder was calcined at 1200 ° C. for 3 hours in an air atmosphere using an alumina crucible to obtain an yttrium oxide raw material powder.

The above yttrium oxide raw material powder and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g), (Y _0.997 Yb _0.003 ) After weighing so as to have a composition ratio of ₂ O ₃ , mixing was performed to obtain a raw material mixed powder. The raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours to produce the scintillator 13 made of (Y _0.997 Yb _0.003 ) ₂ O _{3 of} Example 26. did. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 26, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 200 photons / MeV, and the fluorescence lifetime was about 1 ns. In the scintillator 13 of Example 22, Lu in Example 3 is replaced with Y, but the received light peak wavelength is 360 to 370 nm as in Example 3. Furthermore, the light emission amount of Example 22 was about 13% of Example 3, but the fluorescence lifetime was 1 ns, the same as that of Example 3.

As Example 27, a fluorescent material having a blending ratio of (Y _0.99 Sc _0.007 Yb _0.003 ) ₂ O ₃ was produced.
The yttrium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) prepared in Example 26 and ytterbium oxide (Shin-Etsu Chemical Co., Ltd. ( Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) was weighed so as to have a composition ratio of (Y _0.99 Sc _0.007 Yb _0.003 ) ₂ O ₃ Then, it mixed and it was set as the raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours, thereby comprising (Y _0.99 Sc _0.007 Yb _0.003 ) ₂ O _{3 of} Example 27. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 27, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 250 photons / MeV, and the fluorescence lifetime was about 2 ns.

As Example 28, a fluorescent material having a blending ratio of (Y _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ was produced.
Yttrium oxide raw material powder and gadolinium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) prepared in Example 26 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) was weighed so as to have a composition ratio of (Y _0.99 Gd _0.007 Yb _0.003 ) ₂ O ₃ And mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours, thereby comprising (Y _0.99 Gd _0.007 Yb _0.003 ) ₂ O _{3 of} Example 28. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 28, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 300 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 29, a fluorescent material having a blending ratio of (Y _0.995 La _0.002 Yb _0.003 ) ₂ O ₃ was produced.
Yttrium oxide raw material powder and lanthanum oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) prepared in Example 26 and ytterbium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ² / g) is weighed so as to have a composition ratio of (Y _0.995 La _0.002 Yb _0.003 ) ₂ O ₃ And mixed to obtain a raw material mixed powder. This raw material mixed powder is treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours, thereby comprising (Y _0.995 La _0.002 Yb _0.003 ) ₂ O _{3 of} Example 29. A scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 29, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 250 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 30, a fluorescent material having a blending ratio of (Y _0.99 Sc _0.004 Gd _0.003 Yb _0.003 ) ₂ O ₃ was produced.
Yttrium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) prepared in Example 26 and gadolinium oxide raw material powder (Shin-Etsu Chemical Co., Ltd.) Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 4.3 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Y _0.99 Sc _0.004 Gd _0.003 Yb _0.003 ) ₂ O ₃ and then mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours to obtain (Y _0.99 Sc _0.004 Gd _0.003 Yb _0.003 ) _{2 of} Example 30. A scintillator 13 made of O ₃ was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 30, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 500 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 31, a fluorescent material having a blending ratio of (Y _0.99 Sc _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ was produced.
Yttrium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) and lanthanum oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 26 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Y _0.99 Sc _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ and then mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours to obtain (Y _0.99 Sc _0.005 La _0.002 Yb _0.003 ) ₂ O of Example 31. ₃ scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 31, the light receiving peak wavelength was 360 to 370 nm, the light emission amount was 600 photons / MeV, and the fluorescence lifetime was about 1.5 ns.

As Example 32, a fluorescent material having a blending ratio of (Y _0.99 Gd _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ was produced.
Yttrium oxide raw material powder and scandium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 3.5 m ² / g) and lanthanum oxide raw material powder (Shin-Etsu Chemical Industry) produced in Example 26 Manufactured by Co., Ltd., purity 99.99%, BET specific surface area value 3.8 m ² / g) and ytterbium oxide raw material powder (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.99%, BET specific surface area value 2.7 m ²⁾ / G) was weighed so as to have a composition ratio of (Y _0.99 Gd _0.005 La _0.002 Yb _0.003 ) ₂ O ₃ and then mixed to obtain a raw material mixed powder. This raw material mixed powder was treated in the same manner as in Example 1 and vacuum baked at 1600 ° C. for 10 hours to obtain (Y _0.99 Gd _0.005 La _0.002 Yb _0.003 ) ₂ O of Example 32. ₃ scintillator 13 was produced. Next, the radiation detector 10 using this scintillator 13 was manufactured. The radiation detector 10 was incorporated in the radiation inspection apparatus 20, and the characteristics of the scintillator 13 were measured in the same manner as in Example 3.

  In the scintillator 13 of Example 32, the light reception peak wavelength was 360 to 370 nm, the light emission amount was 500 photons / MeV, and the fluorescence lifetime was about 1 ns.

Table 6 summarizes the emission peak wavelength, emission amount, and fluorescence lifetime when the radiation detector 10 using the scintillators 13 of Examples 26 to 32 is irradiated with γ rays.

  The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Nor. For example, the composition of the scintillator 13 may be set as appropriate in consideration of the fluorescence emission amount and the fluorescence lifetime.

1: Micro pulling device 2: Melt 3: Crucible 3a: Fine pore 4: Seed crystal holding unit 4a: Seed crystal 5: Moving mechanism unit 5a: Pulling shaft 5b: Moving mechanism 5c: Moving mechanism control unit 6: Induction heating unit 6a: induction heating coil 7: furnace material 7a: heat insulating material 7b: after heater 8: crystal synthesis chamber 8a: vacuum exhaust unit 8b: gas introduction unit 9: single crystal 10: radiation detector 12: chamber 13: scintillator 14: light reception Element 14a: Power connection terminal 14b: Output terminal 15: Reflector 17: Read circuit 20, 20a: Radiation inspection apparatus 22: Bias power supply 23: Preamplifier 24: Waveform shaping amplifier 25: Multichannel analyzer 26: Computer 30: Radiation source 31: Image intensifier (IIT)
32: CCD
33: Read circuit 34: High voltage power supply

Claims (15)

Chemical formula (R _1−X Yb _X ) ₂ O ₃ (where R is one or more elements selected from rare earth elements composed of Sc, Y and lanthanoid, and 0 <x <0.1) A light emitting material for scintillators, characterized by   The light emitting material for a scintillator according to claim 1, wherein the rare earth element is one or more elements selected from Sc, Y, La, Gd, and Lu.   The light emitting material for scintillators according to claim 1 or 2, wherein the light emitting material for scintillators generates fluorescence having an emission peak wavelength in a wavelength region of approximately 300 to 600 nm by irradiation of radiation.   The light emitting material for scintillators according to claim 3, wherein the light emitting material for scintillators has little absorption in a wavelength region of 300 to 530 nm corresponding to the emission peak wavelength and is transparent. 2. The scintillator light-emitting material according to claim 1, wherein the scintillator light-emitting material emits fluorescence resulting from a transition from a charge transfer state (CTS) of Yb ³⁺ .   The luminescent material for scintillators according to any one of claims 1 to 5, wherein the luminescent material for scintillators is made of polycrystal or crystals.   A scintillator comprising the light emitting material for scintillators according to any one of claims 1 to 6.   The scintillator according to claim 7, wherein a fluorescence lifetime at room temperature is 5 ns or less.   A radiation detector comprising: a scintillator made of the light emitting material for scintillators according to any one of claims 1 to 6; and a light receiving element for receiving fluorescence from the scintillator.   10. The radiation detection according to claim 9, wherein the light receiving element is any one of a photomultiplier tube, a photodiode, an avalanche photodiode, a Geiger mode avalanche photodiode, an image intensifier, and a charge coupled device. vessel.   A radiation inspection apparatus comprising the radiation detector according to claim 9. It is a manufacturing method of the luminescent material for scintillators in any one of Claims 1-6,
The R oxide powder and the Yb oxide powder are mixed to form a raw material powder compact,
A method for producing a light-emitting material for a scintillator, characterized in that a polycrystal of (R _1-X Yb _X ) ₂ O ₃ is produced by firing the molded body for a predetermined time. The BET specific surface area of the oxide powder is 2 m ² / g or more and 15 m ² / g or less, and secondary aggregated particles exceeding 5 μm are 10% or less by mass fraction. Of manufacturing a light emitting material for a scintillator.   The method for producing a scintillator luminescent material according to claim 12, wherein the density of the molded body is 58% or more. A method of manufacturing a scintillator for emitting material according to claim 1, wherein the chemical formula _{(R 1-X Yb X)} 2 O 3 ( wherein, R represents, Sc, is composed of Y and lanthanoids A single crystal of a light emitting material for scintillator is grown using a raw material powder having a composition represented by 0 <x <0.1). , Manufacturing method of scintillator luminescent material.