JP2016164208A - Scintillator material, radiation detector, and radiation inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scintillator material high in transmittance of scintillate light for a scintillator for an X-ray CT device, having an emission wavelength capable of photoelectric conversion with an Si photodiode, having a short decay time, capable of producing by heat treatment at 1,800°C or less, and suppressed in a production cost.SOLUTION: The scintillator material comprises a light-transmissive ceramic containing a complex oxide represented by following formula (1): (TbRCeQ)BO(1) as a principal constituent, or a single crystal of the complex oxide represented by the formula (1), where 0<x<1, 0.00001≤y≤0.015, 0.000002≤z≤0.02, x≥2y, x+y+z≤1, 1.76≤p≤2.00, 0.80≤p/q≤1.0, r is a positive number for keeping electric neutrality, R is at least one rare earth element selected from the group consisting of Y, Gd, Lu, La, Ho, Tm, and Dy, Q is Eu and/or Pr, and B is at least one element selected from the group consisting of Ti, Sn, Hf, Si, Ge, and Zr.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a scintillator material used for a radiation detector for detecting X-rays and / or a radiation detector for detecting gamma rays, and more particularly to a radiation detector used for an X-ray CT apparatus and / or a gamma-ray PET apparatus. The present invention relates to a scintillator material, a radiation detector, and a radiation inspection apparatus made of translucent ceramics or a single crystal containing an applicable complex oxide.

  A solid scintillator material that emits visible and / or near-visible light energy when excited by radiation energy (high energy electromagnetic photons) such as X-rays and gamma rays is a photoelectric conversion circuit that converts an optical signal into an electrical signal. As a radiation detector in combination with the above, it has been used for various purposes such as resource searching, security, luggage and food inspection, and high energy research. Among them, the above-mentioned solid scintillator material that converts radiation energy into visible and / or near-visible light energy, a photoelectric conversion circuit that converts light energy into an electrical signal, and the output electrical signal are digitized and calculated. X-ray CT devices and gamma-ray PET (Positron Emission Tomography) devices combined with computed tomography (CT) systems that process and image images are rapidly growing mainly in medical institutions as the aging society progresses in recent years. It is becoming popular.

  The X-ray CT apparatus and the gamma-ray PET apparatus are greatly different in the wavelength of the emitted radiation, the optical signal to be obtained and the system for processing it, and each has advantages and disadvantages. For example, an X-ray CT apparatus is less expensive than a gamma ray PET apparatus, but the exposure dose is larger than that of a gamma ray PET apparatus. On the other hand, the gamma-ray PET apparatus is capable of high-speed imaging and is suitable for detecting the position of the cancer by detecting the radioisotope specifically accumulated in the cancer cells, but is an extremely expensive apparatus. For this reason, both devices have been widely spread while being properly separated. Nonetheless, in order to further promote the spread of radiological medical devices to cope with the aging society in the future, development of new scintillator materials that contribute to the reduction of exposure dose in both X-ray CT equipment and gamma-ray PET equipment Is required.

Scintillator materials for X-ray CT apparatus include a majority amount of yttria (Y ₂ O ₃ ), up to about 50 mol% gadolinia (Gd ₂ O ₃ ), and a small amount of activity (typically about 0.02 mol%). A translucent oxide sintered scintillator having a cubic structure containing europium as a rare earth activator oxide (about 12 mol%, preferably about 1 mol% to 6 mol%, most preferably about 3 mol%). It has been known for a long time (US Pat. No. 4,421,671 (Patent Document 1)). This europium activated scintillator has been used for commercial use since it has high luminous efficiency, low afterglow level, and other desirable characteristics.

Other scintillator materials for X-ray CT apparatuses are, for example, powder scintillators that emit light by radiation in Japanese Patent Publication No. 7-97139 (Patent Document 2), and are represented by the general formula (Ln _{1 -xy} Pr _x Ce _y ) ₂ O. ₂ S: (X)
(However, Ln represents at least one element selected from the group consisting of Gd, La and Y, X represents at least one element selected from the group consisting of F and Cl, and x represents 3 × 10 ^−6. ≦ x ≦ 0.2, y is 1 × 10 ⁻⁶ ≦ x ≦ 5 × 10 ⁻³ and X is in the range of 2 to 1000 ppm). Adding a binder, filling in a metal container, vacuum-sealing, hot isostatic pressing, and annealing, and a light-transmitting sintered scintillator that detects the light emitted from the scintillator And a scintillator material with high luminous efficiency is obtained.

  In addition, the material of this system has been widely used as a scintillator material for an X-ray CT apparatus for a long time, and continuously improved inventions have been proposed as disclosed in, for example, Japanese Patent No. 3741302 (Patent Document 3). Yes.

Furthermore, as a scintillator material for other X-ray CT apparatuses, JP 2007-169647 A (Patent Document 4) includes:
“[Claim 1]
A sintered and annealed scintillator composition comprising a garnet having the formula A ₃ B ₂ C ₃ O ₁₂ prior to annealing, wherein A is at least one of the group consisting of Tb, Ce and Lu A position having one element or a combination thereof, B is octahedral (Al), C is tetrahedral (also Al), and the garnet is
(1) In the above formula, 0.05 to 2 atoms of Al in the octahedral position B are replaced with Sc,
(2) In the above formula, 0.005 atom to 2 atoms of oxygen is replaced with fluorine, and the same number of Ca atoms are replaced at the A position,
(3) In the above formula, 0.005 atom to 2 atom at the B position is replaced with Mg, and the same number of oxygen atoms are replaced with fluorine,
(4) In the above formula, 0.005 atoms to 2 atoms at the B position were replaced with at least one combination of atoms selected from the group consisting of Mg / Si, Mg / Zr, Mg / Ti, and Mg / Hf. thing,
(5) In the above formula, 0.005 atom to 2 atoms at the B position are replaced with at least one combination of atoms selected from the group consisting of Li / Nb and Li / Ta, and (6) the above formula Wherein 0.005 atom to 2 atom at the A position is replaced with Ca, and an equal number of B or C positions are replaced with silicon,
Having at least one substitution selected from the group consisting of:
A scintillator composition. "
Is disclosed, and it is said that damage during exposure with a high energy ray can be reduced with a shorter decay time than known scintillator compositions.

A scintillator material having a garnet structure of this system has been newly invented, and recently, similar inventions have been actively proposed (for example, Japanese Patent Application Laid-Open No. 2012-72331 (Patent Document 5) and Japanese Patent Application Laid-Open No. 2012-184397). Gazette (patent document 6) etc.).
It seems that such scintillator materials are being installed in the flagship model of the latest X-ray CT system.

On the other hand, Bi ₄ Ge ₃ O ₁₂ single crystal (commonly known as BGO) has been used for a long time as a scintillator material for a gamma ray PET apparatus. BGO has a strong emission intensity to some extent and a short decay time, but has a low melting point and a low manufacturing cost. Therefore, BGO is in demand as a relatively inexpensive material for PET devices. Thereafter, a Gd ₂ SiO ₅ : Ce (commonly referred to as GSO) single crystal whose light emission amount has been increased and whose decay time has been drastically shortened has been developed and adopted in a high-end model of a gamma ray PET apparatus (for example, Japanese Patent Publication No. 62). No. 8472 (Patent Document 7)).
Thereafter, a Lu ₂ SiO ₅ : Ce (commonly referred to as LSO) single crystal having a larger light emission amount and a shorter decay time was developed, and is still mounted on a flagship machine in a gamma ray PET apparatus (for example, Japanese Patent Application Laid-Open No. Hei 9). -118593 (patent document 8)).

US Pat. No. 4,421,671 Japanese Examined Patent Publication No. 7-97139 Japanese Patent No. 3741302 JP 2007-169647 A JP 2012-72331 A JP 2012-18497A Japanese Examined Patent Publication No. 62-8472 JP-A-9-118593

However, with regard to the X-ray CT apparatus, the scintillator material based on (Y- _{major amount} Gd _{≦ 0.5} ) ₂ O ₃ : Eu based on the X-ray CT apparatus has a long decay time and a density of 6.0 g / cm ^3. The problem was that the film had to be used in the form of a thicker film.
In addition, the (Gd _1-xy Pr _x Ce _y ) ₂ O ₂ S scintillator material disclosed in Patent Documents 2 and 3 has a monoclinic crystal and has a low scintillation light transmittance of about 30%. The point and the point at which the damage at the time of exposure with a high energy ray is comparatively large have been a problem.
Further, disclosed in Patent Document _{4,5,6 (Tb 1-xy Lu x} Ce y) 3 (Al 1-z Sc z) 2 Al 3 O 12 based scintillator material is shorter decay time, Because it is cubic, the transmittance of scintillate light is as high as 80% or more, and it has very little damage when exposed to high energy rays. It is a very suitable material as a scintillator material for X-ray CT equipment. is there. However, there is a problem that a complex oxide having a very complicated composition must be processed and produced at a high temperature, which makes it extremely expensive. Or although the Example which can lower | hang a sintering process temperature is also disclosed depending on a composition, since there are many kinds of constituent elements, there also existed a problem that a yield fell considerably when it was going to manufacture with a desired composition.
On the other hand, regarding the gamma ray PET apparatus, the production cost of the BGO single crystal is reasonable, but the emission intensity and the decay time are insufficient. Further, the GSO single crystal and the LSO single crystal have a high emission intensity and a short decay time, and thus are very suitable substances as a scintillator material for a gamma ray PET apparatus. However, since the melting point is as extremely high as about 2000 ° C., there is a problem that it is much more expensive than other scintillator materials.

  The present invention has been made in view of the above circumstances, and emits scintillation light having an emission peak wavelength in a wavelength region that can be photoelectrically converted by a Si photodiode by excitation of X-rays and / or gamma rays, and the transmittance of the scintillation light is It is an object of the present invention to provide a novel scintillator material, radiation detector, and radiation inspection apparatus capable of producing a complex oxide having a high decay time and a very short decay time by a heat treatment of 1800 ° C. or less and suppressing the production cost.

In order to achieve the above object, the present invention provides the following scintillator material, radiation detector and radiation inspection apparatus.
[1] A scintillator material comprising a translucent ceramic containing a complex oxide represented by the following formula (1) as a main component or a single crystal of a complex oxide represented by the following formula (1).
(Tb _x R _1-xy Ce _y Q _z ) _p B _{q Or} (1)
(Where 0 <x <1, 0.00001 ≦ y ≦ 0.015, 0.000002 ≦ z ≦ 0.02, x ≧ 2y, x + y + z ≦ 1, 1.76 ≦ p ≦ 2.00, 0. 80 ≦ p / q ≦ 1.0, r is a positive number for maintaining electrical neutrality, R is at least one selected from the group consisting of yttrium, gadolinium, lutetium, lanthanum, holmium, thulium, dysprosium Two rare earth elements (but not two or more selected from the group consisting of holmium, thulium, dysprosium), Q is europium and / or praseodymium, B is a group consisting of titanium, tin, hafnium, silicon, germanium, zirconium At least one selected element (except for silicon and germanium, which is not the only element))
[2] The scintillator material according to [1], which emits light having an emission peak in a wavelength range of 540 to 650 nm when excited with X-rays and / or gamma rays.
[3] The scintillator material according to [1] or [2], wherein the transmittance of light having a wavelength of 633 nm at a thickness of 1 mm is 70% or more.
[4] The scintillator material according to any one of [1] to [3], wherein the main phase is a cubic crystal having a pyrochlore lattice.
[5] A radiation detector comprising the scintillator material according to any one of [1] to [4].
[6] A radiation inspection apparatus comprising the radiation detector according to [5].

  According to the present invention, a scintillator material mainly composed of a cubic rare earth oxide different from the garnet phase is co-active with cerium and europium and / or co-active with cerium and praseodymium. , Emits scintillation light having a light emission peak wavelength in a wavelength region that can be photoelectrically converted by a Si photodiode by excitation of X-rays and / or gamma rays, and has high transmittance while the scintillation light has a high transmittance and further has a short decay time. A novel scintillator material can be provided that can provide an output and can be manufactured at a manufacturing temperature of 1800 ° C. or lower, thereby reducing manufacturing costs.

It is the schematic which shows the structure of the radiation detector concerning this invention, (a) is the front view, (b) is AA sectional drawing in (a). It is a figure of the emission spectrum of Example 1-1. It is a figure of the emission spectrum of Example 1-2.

[Scintillator materials]
Hereinafter, the scintillator material according to the present invention will be described.
The scintillator material according to the present invention is made of a translucent ceramic containing a composite oxide represented by the following formula (1) as a main component or a single crystal of the complex oxide represented by the following formula (1).
(Tb _x R _1-xy Ce _y Q _z ) _p B _{q Or} (1)
(Where 0 <x <1, 0.00001 ≦ y ≦ 0.015, 0.000002 ≦ z ≦ 0.02, x ≧ 2y, x + y + z ≦ 1, 1.76 ≦ p ≦ 2.00, 0. 80 ≦ p / q ≦ 1.0, r is a positive number for maintaining electrical neutrality, R is at least one selected from the group consisting of yttrium, gadolinium, lutetium, lanthanum, holmium, thulium, dysprosium Two rare earth elements (but not two or more selected from the group consisting of holmium, thulium, dysprosium), Q is europium and / or praseodymium, B is a group consisting of titanium, tin, hafnium, silicon, germanium, zirconium At least one selected element (except for silicon and germanium, which is not the only element))
Tb, R, Ce, and Q are collectively referred to as elements at the A site.

  In the above formula (1), terbium (Tb) is a skeletal material that is efficiently excited by X-ray and / or gamma ray irradiation, and the excitation energy is efficient for cerium ions that are activators (activators). It has an excitation level that can be well transferred, and the excitation energy of the energy-transferred cerium is at a level that can emit light with a light emission peak in the wavelength region that can be photoelectrically converted by the Si photodiode. It is an element that can be adjusted, and is an essential element in the present invention. It is preferable that energy can be efficiently transferred to the cerium ion, which is an activator, because the emission intensity increases. In addition, it is preferable that photoelectric conversion can be performed with a Si photodiode because a radiation detector can be manufactured at a much lower cost than that received with a photomultiplier tube. Furthermore, if light can be emitted with light having an emission peak in the visible light region on the longer wavelength side than before, the bias voltage can be lowered in a radiation detector using a Si photodiode, so that the circuit can be simplified. preferable.

  Cerium (Ce) is an element that rapidly receives X-ray and / or gamma-ray energy absorbed by terbium and one or more other rare earth elements and enters an excited state, and quickly transitions to a low energy state. In the present invention, it is another essential element. Use of cerium as the activator is preferred because the decay time is much shorter than with terbium alone.

  Q is an element group that assists in quickly transitioning to a low energy state after cerium is in an excited state, that is, cerium emits light, and as an effect, without increasing the decay time, The amount of light emission can be increased, and is another essential element in the present invention.

  The element entering Q (Q element) is at least one rare earth element selected from the group consisting of europium (Eu) and praseodymium (Pr).

  Moreover, there exists a wavelength lock effect as another effect of Q element. That is, by containing Q element, it is always selected from specific wavelengths such as 590 nm ± 7 nm, 615 nm ± 6 nm, 630 nm ± 5 nm, and 640 nm ± 5 nm regardless of the excitation source of ultraviolet rays, X-rays and gamma rays. It emits light with a strong emission peak in the wavelength range of 2 or 3. Therefore, according to the scintillator material of the present invention, high-intensity light can be obtained in a specific wavelength region that is longer than the wavelength region of light emitted from the conventional scintillator material, for example, a wavelength region of 585 to 635 nm. (See FIG. 2). The emission wavelength range is a wavelength range that can be photoelectrically converted by the Si photodiode.

  In addition, the said specific wavelength range is based on the quantity (molar ratio) of the combination of elements other than said Q element and Q, and terbium and Q. The wavelength locking effect is an effect of the Q element that appears regardless of the presence or absence of other rare earth elements, and is an effect that can be obtained even when the content of the Q element is small, as if the main component is a different element. (I.e., when the molar ratio of R is 0.5 or more in the Tb-R-Ce-Q system at the A site), and it appears as if it is a minor component containing a small amount of element Q This is an effect obtained even with an oxide having a composition.

  Note that terbium also has a wavelength locking effect, like the Q element. In this case, by containing terbium, a particularly strong emission peak (the maximum emission peak is always present at a specific wavelength, typically 545 nm ± 6 nm, regardless of the excitation source of ultraviolet rays, X-rays, and gamma rays). Thus, light having a peak having a light emission intensity that is twice or more that of other light emission peaks) can be emitted. The emission spectrum at this time has an emission peak only in the wavelength region of 545 nm ± 6 nm, and the half width of the emission spectrum is very narrow, for example, 12 to 20 nm.

  Regarding the wavelength locking effect, the element Q is dominant in the composite oxide of the above formula (1) and emits intensely in the specific wavelength range. For example, the amount of the element Q is close to the lower limit of the range of z. When the amount decreases, terbium becomes dominant, and light having an emission peak in a wavelength region of 545 nm ± 6 nm is emitted due to the wavelength locking effect of terbium. Terbium is an important and essential element that is preferably contained even in a trace amount in order to ensure that it is an oxide having an emission peak at least at 545 nm or more when producing oxide groups having various compositions. .

Therefore, the scintillator material of the present invention emits light with a stable light emission intensity in a specific wavelength range of 540 nm or more.
In addition, although the light emission peak of the light which the conventional scintillator material emits changes with some compositions, it exists in the wavelength range of 510-590 nm.

  Note that cerium and Q are both elements that can exhibit the above-described effects in a very small amount, and in the present invention, they are essential and important although they are not the main components when viewed quantitatively. Element group.

  R is an element group that has the effect of increasing the density of the material to improve the absorption cross-sectional area of X-ray and / or gamma ray energy. This is a group of elements that have the effect of defining cubic crystals.

  Examples of such elements include yttrium (Y), gadolinium (Gd), lutetium (Lu), lanthanum (La), holmium (Ho), thulium (Tm), and dysprosium (Dy). In particular, yttrium, gadolinium, lutetium, and lanthanum are transparent element groups that do not have excessive absorption levels over a wide wavelength range from the ultraviolet to the infrared region, and thus emit light from terbium, cerium, europium, and / or praseodymium. This is preferable because it does not have the side effect of unnecessarily absorbing and darkening.

  Also, when looking at the electron orbit of each element, the number of electrons occupying the f orbit is exactly zero (when one electron does not enter the f orbit), when all the upwards are occupied (seven), If the total number is downward (14), the Gibbs free energy is small, so that the transparent element group does not have an extra absorption level over a wide wavelength range from ultraviolet to infrared. Examples of element groups that meet this condition include yttrium, gadolinium, lutetium, and lanthanum. All are transparent elements, and there is no superiority or inferiority in the scintillator.

  On the other hand, since holmium, thulium, and dysprosium are not in the electronic state as described above, they have several absorption levels in the visible light region. Therefore, some care is required for handling, and it is preferable that at least one composition should not select two or more from the group consisting of holmium, thulium and dysprosium in order to produce a transparent material.

  Note that yttrium has an effect of lowering the melting point of the material, and is therefore an element that can be suitably used to lower the production temperature of the target material.

  Further, gadolinium, lutetium, and lanthanum are heavy element groups, and thus are element groups that can be suitably used to increase the density of a target material.

  B is an element having an effect of defining the crystal structure of the scintillator material as a pyrochlore type cubic crystal, and is an important element in the present invention. As a result, the scintillator material of the present invention has a cubic crystal (pyrochlore type cubic crystal) having a pyrochlore lattice as a main phase, preferably a pyrochlore type cubic crystal. The main phase means that the pyrochlore type cubic crystal accounts for 90% by volume or more, preferably 95% by volume or more, more preferably 99% by volume or more, and particularly preferably 99.9% by volume or more as a whole. Say. When the crystal structure is a cubic crystal, the effect of scattering due to birefringence is eliminated, the transmittance of scintillation light that is output when excited by X-rays and / or gamma rays is improved, and light with a wavelength of 633 nm at a thickness of 1 mm is obtained. The transmittance is preferably 70% or more.

As such an element, titanium (Ti), tin (Sn), hafnium (Hf), silicon (Si), germanium (Ge), or zirconium (Zr) can be suitably used. However, for silicon and germanium, the case where the element is used alone is excluded.
An element entering this position is referred to as an element at the B site. That is, the scintillator material of the present invention is mainly composed of an A ₂ B ₂ O ₇ type composite oxide.

  In the formula (1), terbium and cerium, Q as europium and / or praseodymium, R as yttrium, gadolinium, lutetium, lanthanum, holmium, thulium, dysprosium, and at least one rare earth element selected from the group consisting of And B includes at least one element selected from the group consisting of titanium, tin, hafnium, silicon, germanium, and zirconium (however, silicon and germanium are not included in the case of the element alone). However, it may further contain other elements. As other elements, ytterbium can be exemplified, and calcium, aluminum, phosphorus, tungsten, molybdenum and the like can be typically exemplified as various impurity groups.

  The content of other elements is preferably 10 or less, more preferably 0.1 or less, and substantially 0.001 or less (substantially zero), assuming that the total amount of elements at the A site position is 100. It is particularly preferred that

  In the formula (1), x related to terbium is in the range of more than 0 and less than 1, preferably more than 0 and 0.8 or less, more preferably 0.001 or more and 0.4 or less, and further preferably 0.001 or more and 0.00. 1 or less, particularly preferably 0.002 or more and 0.05 or less. An activator that, when x is 1, cannot secure y of 0.00001 or more related to cerium, promptly receives absorbed X-ray and / or gamma-ray energy, enters an excited state, and quickly transitions to a low energy state. Cannot be added. When x is less than or equal to 0.1, the tendency to increase the amount of emitted light becomes remarkable, which is preferable.

  In formula (1), y related to cerium is 0.00001 or more and 0.015 or less, and preferably 0.0001 or more and 0.015 or less. If y is less than 0.00001, the absorbed X-ray and / or gamma ray energy is promptly received to be in an excited state, and the concentration of the active agent that quickly transitions to the low energy state is too thin, resulting in a decrease in emission intensity. Or / and a longer decay time. On the other hand, if y exceeds 0.015, the emission intensity starts to decrease again.

  In the formula (1), z relating to the Q element is 0.000002 or more and 0.02 or less, preferably 0.00001 or more and 0.01 or less. If z is less than 0.000002, the effect of increasing the light emission amount of cerium cannot be obtained without increasing the decay time. If z is more than 0.02, the effect of increasing the amount of light emission is remarkable, but the decay time becomes significantly longer.

  Note that x is at least twice y (x ≧ 2y). When x <2y, the emission intensity decreases. Further, x + y + z ≦ 1.

  Moreover, it is preferable that y> z as a relationship between y and z. If cerium is not relatively large as a molar ratio with respect to Q, the decay time may be long.

  Furthermore, it is preferable that 20z ≧ y. If 20z <y, the effect of increasing the amount of cerium emitted by Q may not be obtained.

  In formula (1), p, q, and r are all positive numbers, and p is 1.76 or more and 2.00 or less, preferably 1.76 or more and less than 2.00, more preferably 1.76 or more and 1. 98 or less, more preferably 1.76 or more and 1.90 or less. Further, p / q is 0.80 or more and 1.0 or less, preferably 0.80 or more and less than 1.0, more preferably 0.80 or more and 0.98 or less, and further preferably 0.80 or more and 0.90 or less. is there. Furthermore, r is a positive number for maintaining electrical neutrality. When p is less than 1.76 or p / q is less than 0.80, the pyrochlore cubic crystal is not the main phase, and in the case of ceramics, the translucency is remarkably lowered, which is not preferable. When p / q is larger than 1.0, Tb ions and at least one of R, Ce, and Q occupy the B site position, and Tb tetravalent, Ce tetravalent, etc. are generated, resulting in light emission. This is not preferable because the strength is lowered. It is preferable that p + q = 4 because a scintillator material having a crystal structure with a cubic pyrochlore phase as a main phase can be easily obtained.

When considering the overall composition of this A ₂ B ₂ O ₇ type composite oxide, the selection and molar ratio of the element group at the A site and the element group at the B site can be controlled within a certain appropriate range. Thus, it is possible to obtain a scintillator material having a crystal structure having a cubic pyrochlore phase as a main phase more reliably.

As such a range, the range which satisfy | fills the following formula | equation (2) and Formula (3) simultaneously with the said prescription | regulation regarding p and p / q in Formula (1) is mentioned.

p × (92.3x + 101y + 94.7z1 + 99.7z2 + 90α + 93.8β + 86.1γ + 105δ + 90.1ε + 88ζ + 91.2η) + (q−4.58) × (60.5j + 69k + 71L + 40m + 54n + 72o) ≧ 0 (2)

(5.2-q) × (60.5j + 69k + 71L + 40m + 54n + 72o) −p × (92.3x + 101y + 94.7z1 + 99.7z2 + 90α + 93.8β + 86.1γ + 105δ + 90.1ε + 88ζ + 91.2η) ≧ 0 (3)

(In the formula, p, q, x and y are p, q, x and y in the formula (1). Moreover, as a molar ratio in the element at the A site position in the formula (1), z1 is a range of europium, z2 is the praseodymium range, z1 + z2 = z, α is the yttrium range, β is the gadolinium range, γ is the lutetium range, δ is the lanthanum range, ε is the holmium range, ζ is the thulium range, and η is the displo range Α + β + γ + δ + ε + ζ + η = 1−x−y−z, where j is the titanium range, k is the tin range, and L is the hafnium. , M is the silicon range, n is the germanium range, o is the zirconium range, and j + k + L + m + n + o = 1, that is, the number of moles of the B site is q × (j + k + L + m + n + o). A q.)

  In addition, since the attenuation time is shortened as the number of selected element groups entering R, Q, and B in the formula (1) is increased, the selected element is appropriately selected within the range that can be actually manufactured. It is preferable to increase the number.

  The scintillator material of the present invention contains the composite oxide represented by the above formula (1) as a main component. That is, the scintillator material of the present invention may contain the composite oxide represented by the above formula (1) as a main component, and may contain other components as subcomponents.

  Here, containing as a main component means containing 50 mass% or more of complex oxide represented by the said Formula (1). The content of the composite oxide represented by the formula (1) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 99% by mass or more, and 99.9 It is particularly preferable that the content is at least mass%.

  Other subcomponents that are generally exemplified include dopants and fluxes doped during single crystal growth, and sintering aids added during ceramic production.

  As a manufacturing method of the scintillator material of the present invention, there are a single crystal manufacturing method such as a floating zone method and a micro pull-down method, and a ceramic manufacturing method, and any manufacturing method may be used. However, in general, the single crystal manufacturing method has a certain degree of restriction in the design of the concentration ratio of the solid solution, and the ceramic manufacturing method is more preferable in the present invention.

  Hereinafter, the ceramic production method will be described in more detail as an example of the production method of the scintillator material of the present invention, but the single crystal production method that follows the technical idea of the present invention is not excluded.

《Ceramics manufacturing method》
[material]
As raw materials used in the present invention, cerium and terbium, and rare earth element Q (Q is at least one rare earth element selected from the group consisting of europium and praseodymium), rare earth element R (R is yttrium, gadolinium, lutetium, Is at least one rare earth element selected from the group consisting of lanthanum, holmium, thulium, dysprosium), and further B element (B is at least selected from the group consisting of titanium, tin, hafnium, silicon, germanium, zirconium) A metal powder which is a constituent element of the scintillator material of the present invention comprising one element), an aqueous solution of nitric acid, sulfuric acid, uric acid or the like, or a composite oxide powder of the above elements can be suitably used. In particular, each oxide powder of each element is preferable because it is stable and safe and easy to handle. The purity of these raw materials is preferably 99.9% by mass or more.

  Moreover, it does not specifically limit about the powder shape of the said raw material, For example, square, spherical, and plate-shaped powder can be utilized suitably. Moreover, it can use suitably even if it is the powder which carried out secondary aggregation, and it can use suitably also if it is the granular powder granulated by granulation processes, such as a spray-dry process. Furthermore, the preparation process of these raw material powders is not particularly limited. A raw material powder produced by a coprecipitation method, a pulverization method, a spray pyrolysis method, a sol-gel method, an alkoxide hydrolysis method, or any other synthesis method can be suitably used. Further, the obtained raw material powder may be appropriately treated by a wet ball mill, a bead mill, a jet mill, a dry jet mill, a hammer mill or the like.

  In the composite oxide powder raw material used in the present invention, a sintering suppression aid (sintering aid) may be appropriately added. In particular, in order to obtain a high translucency, it is often preferable to add a suitable sintering inhibitor that is suitable for the host material. However, the purity is preferably 99.9% by mass or more. In addition, when a sintering inhibitor is not added, it is preferable to select a raw material powder that has a primary particle size of nano-size and extremely high sintering activity. Such a selection may be made as appropriate.

  Furthermore, various organic additives may be added for the purpose of improving the quality stability and the yield in the manufacturing process. In the present invention, these are not particularly limited. That is, various dispersants, binders, lubricants, plasticizers, and the like can be suitably used.

[Manufacturing process]
In the present invention, the above raw material powder is pressed into a predetermined shape, degreased, and then sintered to produce a sintered body with a relative density of at least 95% or more. It is preferable to perform a hot isostatic pressing (HIP) process as a subsequent process.

(Molding)
In the production method of the present invention, a normal press molding process can be suitably used. That is, it is possible to use a very general pressing process in which raw material powder is filled in a mold and pressurized from a certain direction, or a CIP (Cold Isostatic Pressing) process in which the raw material powder is sealed in a deformable waterproof container and pressurized with hydrostatic pressure. The applied pressure may be appropriately adjusted while confirming the relative density of the obtained molded body, and is not particularly limited. For example, if the pressure is controlled within a pressure range of about 300 MPa or less that can be handled by a commercially available CIP device, the manufacturing cost can be suppressed. It's okay. Alternatively, not only a molding process but also a hot press process, a discharge plasma sintering process, a microwave heating process, and the like that can be performed all at once at the time of molding can be suitably used. Furthermore, it is possible to produce a molded body by a cast molding method instead of the press molding method. Molding methods such as pressure casting molding and extrusion molding can also be employed by optimizing the combination of the shape and size of the oxide powder as a starting material and various organic additives.

(Degreasing)
In the production method of the present invention, a normal degreasing step can be suitably used. That is, it is possible to go through a temperature rising degreasing process by a heating furnace. Also, the type of atmospheric gas at this time is not particularly limited, and air, oxygen, hydrogen, and the like can be suitably used. The degreasing temperature is not particularly limited, but when a raw material mixed with an organic additive is used, it is preferable to raise the temperature to a temperature at which the organic component can be decomposed and eliminated.

(Sintering)
In the production method of the present invention, a general sintering process can be suitably used. That is, a heating and sintering process such as a resistance heating method or an induction heating method can be suitably used. The atmosphere at this time is not particularly limited, but an inert gas, oxygen, hydrogen, vacuum, or the like can be suitably used.

  The sintering temperature in the sintering step of the present invention is appropriately adjusted depending on the starting material selected. In general, using a selected starting material, a temperature that is several tens of degrees Celsius to 100 degrees Celsius or 200 degrees Celsius lower than the melting point of various composite oxide sintered bodies to be produced is suitably selected. In addition, when trying to produce a pyrochlore-type composite oxide sintered body in which there is a temperature zone in which a phase change to a phase other than a cubic crystal exists in the vicinity of the selected temperature, the conditions under which the temperature zone is strictly excluded and If controlled and sintered, the mixture of phases other than cubic crystals can be suppressed, and birefringence scattering can be reduced.

  The sintering holding time in the sintering process of the present invention is appropriately adjusted depending on the starting material selected. In general, a few hours is often sufficient. However, the relative density of the composite oxide sintered body after the sintering process must be densified to at least 95%.

(Hot isostatic pressing (HIP))
In the production method of the present invention, after the sintering process, an additional step of performing a hot isostatic pressing (HIP (Hot Isostatic Pressing) process) can be provided.

Incidentally, the pressurized gas medium type in this case, argon, an inert gas such as nitrogen or Ar-O ₂ can be used suitably. The pressure applied by the pressurized gas medium is preferably 50 to 300 MPa, and more preferably 100 to 300 MPa. If the pressure is less than 50 MPa, the translucency improvement effect may not be obtained. If the pressure exceeds 300 MPa, no further improvement in translucency can be obtained even if the pressure is increased, and the load on the device may be excessive and damage the device. There is. The applied pressure is preferably 196 MPa or less, which can be processed with a commercially available HIP device, for convenience and convenience.

  Further, the treatment temperature (predetermined holding temperature) at that time may be appropriately set depending on the type of material and / or the sintering state, and is set in the range of, for example, 1000 to 2000 ° C, preferably 1300 to 1800 ° C. At this time, as in the case of the sintering step, it is essential that the temperature be below the melting point and / or the phase transition point of the composite oxide constituting the sintered body. The composite oxide sintered body exceeds the melting point or exceeds the phase transition point, making it difficult to perform an appropriate HIP treatment. Moreover, if the heat treatment temperature is less than 1000 ° C., the effect of improving the translucency of the sintered body cannot be obtained. In addition, although there is no restriction | limiting in particular about the holding time of heat processing temperature, It is good to adjust suitably, checking the characteristic of the complex oxide which comprises a sintered compact.

  In addition, the heater material, heat insulating material, and processing container for HIP processing are not particularly limited, but graphite, molybdenum (Mo), or tungsten (W) can be suitably used.

(Optical polishing)
In the manufacturing method of the present invention, both ends of the light-transmitting composite oxide sintered body (translucent ceramic) that has undergone the above-described series of manufacturing steps on the optically utilized axis can be optically polished. preferable. The optical surface accuracy at this time is preferably λ / 4 or less, particularly preferably λ / 8 or less, when the measurement wavelength λ = 633 nm. Note that it is possible to further reduce the optical loss by appropriately forming an antireflection film on the optically polished surface.

  The scintillator material of the present invention obtained as described above has a cubic crystal having a pyrochlore lattice as a main phase, and when excited by X-rays and / or gamma rays, it has a wavelength region that can be photoelectrically converted by a Si photodiode. Scintillation light having an emission peak, for example, preferably emits light having an emission peak in the wavelength range of 540 to 700 nm, more preferably 540 to 650 nm, and particularly preferably having the strongest emission peak in these wavelength ranges. Further, the transmittance of light having a wavelength of 633 nm when the thickness is 1 mm is 70% or more.

[Radiation detector]
The scintillator material of the present invention is suitable for X-ray CT apparatus applications and / or gamma-ray PET apparatus applications. A large number of arrays are arranged in the apparatus, and the radiation detection is excited by X-ray irradiation and / or gamma irradiation. Suitable for dexterity. Note that X-rays and gamma rays assumed in the present invention include, for example, X-rays generated in an X-ray tube using a target having an electron beam irradiation surface made of tungsten or a tungsten alloy (Re-W alloy), and radioisotopes. Examples include gamma rays generated from a gamma ray source of body cobalt 60.

  The radiation detector of the present invention comprises a plate made of the scintillator material of the present invention and a light receiving element such as a Si photodiode at the subsequent stage. An example of the configuration is shown in FIG. In the radiation detector 10 of the present invention, a scintillator plate 11 made of the scintillator material of the present invention is partitioned by a reflector 12 and arranged in 36 elements in 6 rows and 6 columns, and further receives light at the subsequent stage of each scintillator plate 11. The element 13 is arranged and stored in the container 14. In this radiation detector 10, the scintillator plate 11 is excited by X-rays and / or gamma rays incident from the front, and the light emission energy output from the scintillator plate 11 is converted into an electric signal by the light receiving element 13 and amplified. It is configured to output.

  The light receiving element 13 can detect light in the region of the emission peak wavelength of the scintillator material of the present invention, and is a general element used for a radiation detector mounted on an X-ray CT apparatus or a gamma ray PET apparatus. Si photodiode (PD), Si-APD (Avalanche Photodiode), CCD (Charge Coupled Device) image sensor, photomultiplier tube (PMT), and the like. As the light receiving element 13, for example, Si-APD (Avalanche Photodiode) having a sensitivity wavelength range of 450 to 1050 nm and a maximum sensitivity wavelength of 550 nm or more, preferably a sensitivity wavelength range of 450 to 800 nm and a maximum sensitivity wavelength of 590 nm or more is preferable.

  A combination of the radiation detector 10 of the present invention arranged in an array in this way and a computed tomography (CT) system that digitizes an electrical signal output from the radiation detector 10 and calculates and images it. Thus, a radiation inspection apparatus such as an X-ray CT apparatus or a gamma ray PET apparatus is manufactured.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the examples. In addition, the primary particle diameter of the raw material powder was calculated | required as a weight average value by a laser beam diffraction method.

[Example 1, Comparative Example 1]
In the above formula (1), p = 2 and q = 2 (that is, p / q = 1.0), and the concentration of terbium and cerium is fixed for the composition in which cerium and europium or praseodymium are co-added. An example in which titanium, tin, hafnium or zirconium is selected as the element at the B site will be described.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, yttrium oxide powder, lanthanum oxide powder, and gadolinium oxide powder manufactured by Shin-Etsu Chemical Co., Ltd. were obtained. In addition, titanium oxide powder, stannic oxide powder, Hafnium oxide powder manufactured by American Elements, and zirconium oxide powder manufactured by Daiichi Elemental Chemical Co., Ltd. were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio as shown in Table 1 having a final composition was produced. That is, the final sum of the molar ratios of terbium, cerium, Q element, and R element (that is, the number of moles of the element at the A site position) and the number of moles of titanium, tin, hafnium, or zirconium (that is, the B site position). Each of the mixed powders weighed so as to have an equimolar molar ratio of the number of moles of the element) was prepared. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put in an iridium crucible and fired at 1600 ° C. for 3 hours in a high temperature muffle furnace to obtain 12 kinds of firing raw materials including comparative examples. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, it was confirmed that any of the fired raw materials was an oxide raw material having a pyrochlore cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure.
The obtained various raw materials were again dispersed and mixed in ethanol in a zirconia ball mill apparatus. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.

Each ceramic sintered body thus obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm to obtain a scintillator plate. Next, a reflector (made of magnesium oxide powder dispersed in a silicone paste and bonded by drying) is provided between the scintillator plates and partitioned into 36 elements in 6 rows and 6 columns. The optical end surfaces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when the measurement wavelength was λ = 633 nm).
About each obtained scintillator plate, the transmittance | permeability was measured in the following ways using HeNe laser (wavelength 633nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.

(Measurement method of transmittance)
The transmittance was measured by the intensity of light when light having a wavelength of 633 nm was transmitted, and was determined based on the following equation.
Transmittance = I / Io × 100
(In the formula, I represents transmitted light intensity (intensity of light transmitted through a sample having a thickness of 1 mm), and Io represents incident light intensity.)

Thereafter, each scintillator plate 11 was placed on the light receiving element 13 to produce the radiation detector 10 of FIG. Next, using a light output measuring device manufactured by combining the radiation detector 10 and an X-ray tube of a tungsten target, the scintillator plate 11 is irradiated with X-rays at a tube voltage of the X-ray tube of 120 kV, and the light receiving element 13 is irradiated. The value of the flowing current was obtained as the light output. In addition, Si-APD (Hamamatsu Photonics Co., Ltd. short wavelength type, model number S5343, sensitivity wavelength range 450 to 800 nm, maximum sensitivity wavelength 590 nm) was used as the light receiving element 13. In addition, the sensitivity and wavelength of this Si-APD at a wavelength of 540 nm (emission peak wavelength of CdWO ₄ single crystal (CWO single crystal) scintillator as a reference sample) and a wavelength of 580 to 650 nm (a range corresponding to a wavelength range in which the example sample emits strongly) The sensitivity at is similar.
At this time, the emission wavelength range, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were determined as follows.

(Measurement method of maximum emission peak wavelength and emission wavelength range)
Before the light output is evaluated by the X-ray irradiation evaluation system, photoluminescence (PL) measurement is performed with a fluorescence lifetime measuring apparatus (Quantaurus-Tau: model number C11367-1 manufactured by Hamamatsu Photonics Co., Ltd.), and the emission peak wavelength is determined from the result. Asked. That is, excitation is performed with light having an excitation wavelength of 280 nm, the emitted fluorescence is subjected to spectroscopy by a grating, a fluorescence wavelength spectrum (emission spectrum) is detected by a CCD camera, and the wavelength at which the fluorescence output is maximized is irradiated with X-rays. The wavelength range until the emission intensity becomes half value with respect to the maximum emission peak in the emission spectrum was determined as the emission wavelength region. The light having an excitation wavelength of 280 nm is ultraviolet light having the shortest wavelength that can be incident on the fluorescence lifetime measuring apparatus, that is, the maximum energy, and does not cause vibration of the skeleton material during X-ray irradiation. The excitation energy that has been gradually relaxed when excited is an excitation wavelength sufficient to confirm the wavelength at which light is finally emitted, and is used as a substitute for X-rays for measuring the emission peak wavelength during X-ray irradiation. Can be used.

As an example of the emission spectrum at this time, FIG. 2 shows the emission spectrum of Example 1-1, and FIG. 3 shows the emission spectrum of Example 1-2. In Example 1-1, strong emission peaks were observed at wavelengths of 590, 615, and 630 nm, respectively, and in Example 1-2, strong emission peaks were observed at wavelengths of 615 and 640 nm, respectively.
In addition, the pattern of the emission spectrum of the other examples (however, examples in which x> 0.5, that is, excluding Examples 2-3, 2-6, 2-9, and 2-12) are emission peak wavelengths. Except for the luminescence intensity and the luminescence intensity, a strong luminescence peak at a specific wavelength was exhibited in the same manner as in Example 1-1 or Example 1-2. Specifically, strong emission peaks were exhibited in two or three wavelength regions selected from 590 nm ± 7 nm, 615 nm ± 6 nm, 630 nm ± 5 nm, and 640 nm ± 10 nm.

(Measurement method of light output)
Here, for the purpose of facilitating the comparison, a CdWO ₄ single crystal (CWO single crystal) scintillator separately obtained in the radiation detector 10 is arranged in place of the scintillator plate 11, and an evaluation method using the light output measuring device is used. The light output in this case was obtained, and the ratio of the light output of the sample (vs. CWO ratio) when the value was “1.0” was shown as the value of the light output of each sample. The light output here is an integrated value of the light output intensity at a wavelength of 450 to 800 nm.

(Measurement method of decay time)
As described above, the state in which the light output of each sample is stabilized by irradiating the X-ray with the light output measuring apparatus is set to 100%, then the X-ray irradiation is stopped, and the light output intensity of each sample is stopped. Was measured until the time of decay to 5% of the stable state (decay time during X-ray irradiation).
In addition, as described above, the fluorescence lifetime measurement apparatus is used to irradiate light with an excitation wavelength of 280 nm so that the light output of each sample is stabilized to 100%, and then the light irradiation is stopped. The time until the light output intensity of the light was attenuated to 5% of the stable state was measured (attenuation time during ultraviolet irradiation).
Table 2 summarizes the above series of evaluation results.

From the above results, the scintillator materials mainly composed of pyrochlore type complex oxides of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 77% or more. Because the light emitted as a scintillator material is not scattered and lost in the interior, and the strongest emission peak wavelength when excited by X-rays is 545 nm or more, photoelectric conversion is a problem with a Si photodiode as a light receiving element. Furthermore, the light output is twice as large as that of the conventional material, and furthermore, the decay time at 5% afterglow output by X-ray irradiation is as short as 7 ms or less. Further, the decay time when the afterglow output was 5% due to ultraviolet irradiation was 10 ns or less, depending on the composition, it was 1 nm which is the measurement lower limit level (apparatus performance limit). When europium is co-added, the strong emission peak when excited by X-rays is locked at wavelengths of 590, 615, and 630 nm, and when praseodymium is co-added, the wavelength is locked at 615 and 640 nm. The locking effect was also confirmed. As a result, when the scintillator material of the present invention is used in a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be speeded up, so that the operability and safety of a low exposure dose are excellent. It is possible to finish the radiation inspection apparatus.
In the comparative example of the composition using only cerium as the activator, the output is slightly lower than that of the co-added composition with europium and praseodymium, and the light output ratio with respect to the CWO single crystal is 1.5 or less.

[Example 2]
In the above formula (1), an example in which p = 2 and q = 2 (that is, p / q = 1.0) and the amount of terbium is changed will be described.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, lutetium oxide powder, lanthanum oxide powder, and gadolinium oxide powder manufactured by Shin-Etsu Chemical Co., Ltd. were obtained. In addition, titanium oxide powder, stannic oxide powder, Hafnium oxide powder manufactured by American Elements, and zirconium oxide powder manufactured by Daiichi Elemental Chemical Co., Ltd. were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio having a final composition as shown in Table 3 was produced. That is, the final sum of the molar ratios of terbium, cerium, Q element, and R element (that is, the number of moles of the element at the A site position) and the number of moles of titanium, tin, hafnium, or zirconium (that is, the B site position). Each of the mixed powders weighed so as to have an equimolar molar ratio of the number of moles of the element) was prepared. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put in an iridium crucible and fired at 1600 ° C. for 3 hours in a high temperature muffle furnace to obtain 12 kinds of firing raw materials. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, it was confirmed that any of the fired raw materials was an oxide raw material having a pyrochlore cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure.
Various raw materials thus obtained were again dispersed and mixed in ethanol in a zirconia ball mill. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.
Subsequently, each ceramic sintered body obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm. Next, they were processed into a scintillator material consisting of 36 elements of 6 × 6 via a reflective material, and the optical end faces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when measurement wavelength λ = 633 nm).
The transmittance of each scintillator plate obtained was measured in the same manner as in Example 1 using a HeNe laser (wavelength 633 nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.
Thereafter, each scintillator plate 11 was placed on the light receiving element 13 in the same manner as in Example 1 to produce the radiation detector 10 of FIG. Next, a light output measuring device was produced in the same manner as in Example 1, and the scintillator plate 11 was irradiated with X-rays at a tube voltage of 120 kV of an X-ray tube of a tungsten target, and the current value flowing through the light receiving element 13 was obtained as the light output. At this time, in the same manner as in Example 1, the emission wavelength region, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were obtained.
Table 4 summarizes the above series of evaluation results.

From the above results, the scintillator materials mainly composed of pyrochlore type complex oxides of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 76% or more. The light emitted as the scintillator material does not wastefully scatter inside, and the wavelength of the strong emission peak when excited with X-rays is 590 nm or more, and a Si photodiode is used as the light receiving element. In addition, photoelectric conversion can be performed without the need to increase the bias voltage as in the case of the conventional material (CWO single crystal). Furthermore, the light output is larger than that of the conventional material. Particularly, when the terbium content is small, for example, when x ≦ 0.8, the light output (light quantity) is 1.8 times or more that of the conventional material. The light output is about twice or more that of the material. In addition, in any of the examples, the decay time when the afterglow output is 5% by X-ray irradiation is as short as 7 ms or less. Further, the decay time when the afterglow output is 5% due to ultraviolet irradiation is 10 ns or less. As a result, when the scintillator material of the present invention is used in a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be speeded up, so that the operability and safety of a low exposure dose are excellent. It is possible to finish the radiation inspection apparatus.
By the way, when the terbium content is x ≦ 0.5, the wavelength locking effect of the emission wavelength of europium or praseodymium, ie, any two or three of wavelengths 590, 615, 630, 640 nm is particularly strong. Light emission having an emission peak was confirmed. Further, when the terbium content was x> 0.5, a long wavelength side shift of the wavelength of the strongest emission peak was confirmed, and light emission having a certain intensity was confirmed in a wide wavelength range.

[Example 3, Comparative Example 3]
In the above formula (1), an example in which p = 2 and q = 2 (that is, p / q = 1.0) and the amounts of cerium and the Q element are changed will be described.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, yttrium oxide powder, and lanthanum oxide powder manufactured by Shin-Etsu Chemical Co., Ltd. were obtained. In addition, titanium oxide powder manufactured by Kojundo Chemical Laboratory Co., Ltd. and hafnium oxide powder manufactured by American Elements were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio having a final composition as shown in Table 5 was produced. That is, the final sum of the molar ratios of terbium, cerium, Q element, and R element (that is, the number of moles of the element at the A site) and the number of moles of titanium and hafnium (that is, the number of moles of the element at the B site) ) And the mixed powders weighed so as to have an equimolar molar ratio. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put in an iridium crucible and fired at 1600 ° C. for 3 hours in a high temperature muffle furnace to obtain 18 kinds of firing raw materials including comparative examples. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, it was confirmed that any of the fired raw materials was an oxide raw material having a pyrochlore cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure.
Various raw materials thus obtained were again dispersed and mixed in ethanol in a zirconia ball mill. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.
Subsequently, each ceramic sintered body obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm. Next, they were processed into a scintillator material consisting of 36 elements of 6 × 6 via a reflective material, and the optical end faces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when measurement wavelength λ = 633 nm).
The transmittance of each scintillator plate obtained was measured in the same manner as in Example 1 using a HeNe laser (wavelength 633 nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.
Thereafter, each scintillator plate 11 was placed on the light receiving element 13 in the same manner as in Examples 1 and 2, and the radiation detector 10 of FIG. Next, a light output measuring device was produced in the same manner as in Example 1, and the scintillator plate 11 was irradiated with X-rays at a tube voltage of 120 kV of an X-ray tube of a tungsten target, and the current value flowing through the light receiving element 13 was obtained as the light output. At this time, in the same manner as in Example 1, the emission wavelength region, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were obtained.
The series of evaluation results described above are summarized in Table 6.

From the above results, the scintillator materials mainly composed of pyrochlore type complex oxides of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 76% or more. As a scintillator material, there is a strongest emission peak wavelength in the wavelength band where light emitted without scintillation loss inside it can be performed without problems with Si photodiodes when excited by X-rays. Furthermore, the light output is also larger than that of the conventional material. In addition, the decay time when the afterglow output is 5% due to X-ray irradiation is 13 ms or less, and the decay time when the afterglow output is 5% due to ultraviolet irradiation is 3000 ns or less. is there. As a result, when the scintillator material of the present invention is used in a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be speeded up, so that the operability and safety of a low exposure dose are excellent. It is possible to finish the radiation inspection apparatus.
In addition, when details are individually seen, when the content of europium or praseodymium is larger than the content of cerium (y <z) as in Examples 3-2 and 3-7, the light output is sufficiently large, and the wavelength lock Although the effect can be obtained, the decay time becomes longer. Further, when the content of europium or praseodymium increases as in Examples 3-11 and 3-12 (z = 0.02), the light output is sufficiently large and the wavelength lock effect is obtained, but the decay time becomes long. .
When both the contents of cerium and europium or praseodymium are small as in Examples 3-3 and 3-8 (y = 0.00001, z = 0.000005), the light output tends to decrease. Further, as in Examples 3-4 and 3-9, when the content of europium or praseodymium is small (z = 0.000005), the relationship between the content of europium or praseodymium with respect to the cerium content is y> 20z. In addition, the wavelength lock effect at the time of light output of europium or praseodymium is lost, the wavelength lock effect of terbium is expressed, and light having a maximum emission peak wavelength of 545 nm is output. Incidentally, in Examples 3-1 to 3-3, 3-5 to 3-8, and 3-10 to 3-12, the wavelength locking effect of the emission wavelength of europium or praseodymium was confirmed.
Moreover, when there is too much content of cerium like Comparative Examples 3-1 and 3-3 (y = 0.03), an optical output will fall. On the contrary, the light output decreases even when cerium is not contained as in Comparative Examples 3-2 and 3-4. Furthermore, as in Comparative Examples 3-5 and 3-6, when the relationship between the terbium content and the cerium content is x <2y, the light output is drastically decreased.

[Example 4, Comparative Example 4]
In the above formula (1), an example in which p = 2 and q = 2 (ie, p / q = 1.0) and the R element is changed will be described.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, yttrium oxide powder, lutetium oxide powder, lanthanum oxide powder, gadolinium oxide powder, dysprosium oxide powder, holmium oxide powder, manufactured by Shin-Etsu Chemical Co., Ltd. Thulium oxide was obtained. In addition, titanium oxide powder manufactured by Kojundo Chemical Laboratory Co., Ltd. and hafnium oxide powder manufactured by American Elements were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio as shown in Table 7 having a final composition was produced. That is, the final sum of the molar ratios of terbium, cerium, Q element, and R element (that is, the number of moles of the element at the A site) and the number of moles of titanium and hafnium (that is, the number of moles of the element at the B site) ) And the mixed powders weighed so as to have an equimolar molar ratio. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put in an iridium crucible and fired at 1600 ° C. for 3 hours in a high-temperature muffle furnace to obtain 8 kinds of firing raw materials including comparative examples. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, it was confirmed that any of the fired raw materials was an oxide raw material having a pyrochlore cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure.
Various raw materials thus obtained were again dispersed and mixed in ethanol in a zirconia ball mill. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.
Subsequently, each ceramic sintered body obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm. Next, they were processed into a scintillator material consisting of 36 elements of 6 × 6 via a reflective material, and the optical end faces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when measurement wavelength λ = 633 nm).
The transmittance of each scintillator plate obtained was measured in the same manner as in Example 1 using a HeNe laser (wavelength 633 nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.
Thereafter, each scintillator plate 11 was placed on the light receiving element 13 in the same manner as in Examples 1, 2, and 3, and the radiation detector 10 of FIG. Next, a light output measuring device was produced in the same manner as in Example 1, and the scintillator plate 11 was irradiated with X-rays at a tube voltage of 120 kV of an X-ray tube of a tungsten target, and the current value flowing through the light receiving element 13 was obtained as the light output. At this time, in the same manner as in Example 1, the emission wavelength region, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were obtained.
Table 8 summarizes the series of evaluation results described above.

From the above results, the scintillator materials mainly composed of pyrochlore type complex oxides of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 76% or more. The light emission as the scintillator material has the strongest emission peak wavelength in the wavelength band in which photoelectric conversion can be performed without problems with the Si photodiode when excited with X-rays without wasteful scattering loss inside the material, Furthermore, the light output is not inferior to conventional materials. In addition, the decay time when the afterglow output is 5% due to X-ray irradiation is as short as 6 ms or less. In addition, the decay time when the afterglow output is 5% due to ultraviolet irradiation is 10 ns or less. As other special notes, emission with particularly strong emission peaks at any two or three of the wavelengths 590, 615, 630, and 640 nm was confirmed by adding europium and praseodymium slightly. (Wavelength lock effect). As a result, when the scintillator material of the present invention is used in a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be speeded up, so that the operability and safety of a low exposure dose are excellent. It is possible to finish the radiation inspection apparatus.
In the compositions of Comparative Examples 4-1 and 4-2, the total absorption amount is accumulated and the light output is reduced by simultaneously mixing a plurality of slightly absorbing elements such as dysprosium, holmium, and thulium.

[Example 5, Comparative Example 5]
In the above formula (1), p = 2, q = 2 (that is, p / q = 1.0), and the element at the B site position is selected from the group consisting of silicon, germanium, zirconium, and hafnium. explain.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, lutetium oxide powder, yttrium oxide powder, and gadolinium oxide powder manufactured by Shin-Etsu Chemical Co., Ltd. were obtained. In addition, silica powder, germanium oxide powder manufactured by Kojundo Chemical Laboratory Co., Ltd., zirconium oxide powder manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., and hafnium oxide powder manufactured by American Elements were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio with a final composition as shown in Table 9 was produced. That is, the sum of the final molar ratios of terbium, cerium, europium or praseodymium and lutetium, yttrium or gadolinium (ie, the number of moles of the element at the A site) and silicon and zirconium or hafnium, or germanium and zirconium or hafnium. The mixed powders weighed so that the sum of the molar ratios or the number of moles of silicon and germanium (that is, the number of moles of the element at the B site) were the same molar ratio were prepared. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put in an iridium crucible and fired at 1600 ° C. for 3 hours in a high-temperature muffle furnace to obtain 8 kinds of firing raw materials including comparative examples. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, all examples were confirmed to be oxide raw materials having a pyrochlore cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure. Moreover, although it was a pyrochlore type, the raw materials in which the crystal system was orthorhombic were the groups of Comparative Examples 5-1 and 5-2.
Various raw materials thus obtained were again dispersed and mixed in ethanol in a zirconia ball mill. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.
Subsequently, each ceramic sintered body obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm. Next, they were processed into a scintillator material consisting of 36 elements of 6 × 6 via a reflective material, and the optical end faces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when measurement wavelength λ = 633 nm).
The transmittance of each scintillator plate obtained was measured in the same manner as in Example 1 using a HeNe laser (wavelength 633 nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.
Then, each scintillator plate 11 was arrange | positioned on the light receiving element 13 similarly to Examples 1-4, and the radiation detector 10 of FIG. 1 was produced. Next, a light output measuring device was produced in the same manner as in Example 1, and the scintillator plate 11 was irradiated with X-rays at a tube voltage of 120 kV of an X-ray tube of a tungsten target, and the current value flowing through the light receiving element 13 was obtained as the light output. At this time, in the same manner as in Example 1, the emission wavelength region, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were obtained.
The series of evaluation results described above are summarized in Table 10.

From the above results, scintillator materials mainly composed of pyrochlore type complex oxides consisting of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 78% or more. As a scintillator material, there is a strongest emission peak wavelength in the wavelength band where light emitted without scintillation loss inside it can be performed without problems with Si photodiodes when excited by X-rays. Furthermore, the light output is more than twice that of the conventional material. In addition, the decay time when the afterglow output is 5% due to X-ray irradiation is as short as 7 ms or less. Further, the decay time when the afterglow output is 5% due to ultraviolet irradiation is 20 ns or less. As a result, when the scintillator material of the present invention is used in a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be speeded up, so that the operability and safety of a low exposure dose are excellent. It is possible to finish the radiation inspection apparatus.
In the compositions of Comparative Examples 5-1 and 5-2, the crystal system was orthorhombic, so that the transmittance was lowered, thereby reducing the light output.

[Example 6, Comparative Example 6]
In the above formula (1), europium or praseodymium is selected as the Q element, lutetium, yttrium or lanthanum is selected as the R element, and the element at the B site is selected from the group consisting of hafnium, silicon, germanium and zirconium. An example in which the ratio of p to q (p / q) is changed will be described.
Terbium oxide powder, cerium oxide powder, europium oxide powder, praseodymium oxide powder, lutetium oxide powder, yttrium oxide powder, and lanthanum oxide powder manufactured by Shin-Etsu Chemical Co., Ltd. were obtained. In addition, silica powder, germanium oxide powder manufactured by Kojundo Chemical Laboratory Co., Ltd., zirconium oxide powder manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., and hafnium oxide powder manufactured by American Elements were obtained. All the purity was 99.9 mass% or more.
Using the raw materials, each mixed oxide raw material having a mixing ratio having a final composition as shown in Table 11 was produced. That is, the final total p of terbium, cerium, europium or praseodymium, and the number of moles of the element at the R site (that is, the number of moles of the element at the A site), silicon and hafnium, germanium and hafnium, silicon and zirconium Or the total number of moles of germanium and zirconium, or the number of moles of hafnium or silicon q (that is, the number of moles of the element at the B site) is p / q = 1.00, 0.80, or 0.33 Each of the mixed powders weighed so that In addition, the numerical value of p / q is rounded off to two decimal places based on the molar ratio of the composition. Subsequently, the mixture was dispersed and mixed in a zirconia ball mill apparatus in ethanol while preventing mixing of the test samples. The treatment time was 24 hours. Thereafter, spray drying treatment was performed to produce a granular raw material having an average particle diameter of 20 μm.
Furthermore, these powders were put into an iridium crucible and fired at 1600 ° C. for 3 hours in a high-temperature muffle furnace to obtain 11 kinds of firing raw materials including comparative examples. Each obtained firing raw material was subjected to diffraction pattern analysis by a powder X-ray diffractometer manufactured by Panalytical. As a result, a group of all Examples (Examples 6-1 to 6-8) was confirmed as an oxide raw material having a pyrochlore type cubic crystal (cubic crystal having a pyrochlore lattice) as a main phase as a crystal structure. It was. Moreover, the raw material in which the fluorite type tetragonal crystal was mixed in addition to the pyrochlore type cubic crystal was the group of Comparative Examples 6-1 and 6-2. Furthermore, although it was a pyrochlore type, the raw material in which the crystal system was orthorhombic was Comparative Example 6-3.
Various raw materials thus obtained were again dispersed and mixed in ethanol in a zirconia ball mill. At this time, an organic dispersant and an organic binder were appropriately added. The processing time was 40 hours. Thereafter, spray drying treatment was performed again to produce granular pyrochlore oxide raw materials (starting raw materials) having an average particle diameter of 20 μm.

Next, the obtained starting material is filled into a 40 mm diameter mold, temporarily formed into a 6 mm thick rod with a uniaxial press molding machine, and then hydrostatically pressed at a pressure of 198 MPa to obtain a CIP compact. It was. Subsequently, the obtained CIP compact was put into a muffle furnace, and degreased by heat treatment in the atmosphere at 800 ° C. for 3 hours.
Next, the obtained degreased molded body was charged into a vacuum heating furnace, heated to 1500-1700 ° C. at a temperature increase rate of 100 ° C./h, held for 3 hours, and then cooled at a temperature decrease rate of 600 ° C./h. Thus, a sintered body was obtained. At this time, the sintering temperature and holding time were adjusted so that the sintered relative density of the sample was 95% or more.
Further, the sintered body was subjected to HIP treatment using an Ar gas as a pressure medium at a HIP heat treatment temperature of 1500 to 1750 ° C. and a pressure of 190 MPa for a holding time of 3 hours.
Subsequently, each ceramic sintered body obtained was cut, ground, and polished so as to have a length and width of 2 mm × 2 mm and a thickness of 1 mm. Next, they were processed into a scintillator material consisting of 36 elements of 6 × 6 via a reflective material, and the optical end faces of the sample were subjected to final optical polishing with an optical surface accuracy of λ / 4 (when measurement wavelength λ = 633 nm).
The transmittance of each scintillator plate obtained was measured in the same manner as in Example 1 using a HeNe laser (wavelength 633 nm). At this time, care was taken so that the laser beam did not strike the reflective material between the scintillator plate and the scintillator plate.
Then, each scintillator plate 11 was arrange | positioned on the light receiving element 13 similarly to Examples 1-5, and the radiation detector 10 of FIG. 1 was produced. Next, a light output measuring device was produced in the same manner as in Example 1, and the scintillator plate 11 was irradiated with X-rays at a tube voltage of 120 kV of an X-ray tube of a tungsten target, and the current value flowing through the light receiving element 13 was obtained as the light output. At this time, in the same manner as in Example 1, the emission wavelength region, maximum emission peak wavelength, light output, and decay time of the scintillator plate 11 were obtained.
The series of evaluation results described above are summarized in Table 12.

From the above results, the scintillator materials mainly composed of pyrochlore type complex oxides of the group of examples are transparent with a light transmittance of 633 nm when the thickness is 1 mm, which is 77% or more. As a scintillator material, there is a strongest emission peak wavelength in the wavelength band where light emitted without scintillation loss inside it can be performed without problems with Si photodiodes when excited by X-rays. Furthermore, the light output is more than twice that of the conventional material. In addition, the decay time when the afterglow output is 5% due to X-ray irradiation is as short as 7 ms or less. Further, the decay time when the afterglow output is 5% due to ultraviolet irradiation is 20 ns or less. When europium is co-added, the strong emission peak when excited by X-rays is locked at wavelengths of 590, 615, and 630 nm, and when praseodymium is co-added, the wavelength is locked at 615 and 640 nm. The locking effect was also confirmed. Comparing in more detail, in the composition group in which the element at the A site and the element at the B site are the same, the light output is remarkably increased when the p / q is decreased from 1.00 to 0.80. In Examples 6-1 and 6-2, p / q is 1.00, that is, a pyrochlore oxide composition having a stoichiometric composition. In Examples 6-2 and 6-4, this stoichiometric composition is used. By shifting the composition ratio in the direction in which q increases and p decreases, a light output greater than that of a scintillator material having a stoichiometric composition can be obtained. However, as shown in Comparative Examples 6-1 and 6-2, if p / q is too small, that is, if q is excessively decreased or p is excessively increased, the light output is significantly decreased and the decay time is increased. It will occur. In Comparative Example 6-3, since the crystal system is orthorhombic, the transmittance is reduced, thereby reducing the light output.
According to the present invention, it contains terbium, a co-active type with cerium and europium, and / or a co-active type with cerium and praseodymium, and a cubic rare earth oxide different from the garnet phase as a main component, By using a scintillator material in which the composition ratio (molar ratio) of the element at the A site and the element at the B site is slightly shifted from the stoichiometric composition, photoelectric conversion is performed with the Si photodiode by excitation of X-rays and / or gamma rays. Produces scintillation light having an emission peak wavelength in a convertible wavelength range, and has a high light output than a scintillator material having a stoichiometric composition while having a high transmittance of the scintillation light and further shortening the decay time. A novel scintillator material with reduced manufacturing cost can be provided because the temperature is 1800 ° C. or lower.
As described above, when the scintillator material of the present invention is used for a radiation inspection apparatus such as an X-ray CT apparatus or a gamma-ray PET apparatus, the switching cycle can be accelerated, so that the operability and safety of a low exposure dose are reduced in a short time. It is possible to finish the radiation inspection apparatus excellent in.

  The present invention has been described with the embodiment. However, the present invention is not limited to the above embodiment, and other embodiments, additions, modifications, deletions, and the like can be conceived by those skilled in the art. As long as the effects of the present invention are exhibited in any aspect, the present invention is included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Radiation detector 11 Scintillator plate 12 Reflector 13 Light receiving element 14 Container

Claims (6)

A scintillator material comprising a translucent ceramic containing a complex oxide represented by the following formula (1) as a main component or a single crystal of a complex oxide represented by the following formula (1).
(Tb _x R _1-xy Ce _y Q _z ) _p B _{q Or} (1)
(Where 0 <x <1, 0.00001 ≦ y ≦ 0.015, 0.000002 ≦ z ≦ 0.02, x ≧ 2y, x + y + z ≦ 1, 1.76 ≦ p ≦ 2.00, 0. 80 ≦ p / q ≦ 1.0, r is a positive number for maintaining electrical neutrality, R is at least one selected from the group consisting of yttrium, gadolinium, lutetium, lanthanum, holmium, thulium, dysprosium Two rare earth elements (but not two or more selected from the group consisting of holmium, thulium, dysprosium), Q is europium and / or praseodymium, B is a group consisting of titanium, tin, hafnium, silicon, germanium, zirconium At least one selected element (except for silicon and germanium, which is not the only element))   The scintillator material according to claim 1, which emits light having an emission peak in a wavelength range of 540 to 650 nm when excited by X-rays and / or gamma rays.   The scintillator material according to claim 1 or 2, wherein the transmittance of light having a wavelength of 633 nm at a thickness of 1 mm is 70% or more.   The scintillator material according to any one of claims 1 to 3, wherein the main phase is a cubic crystal having a pyrochlore lattice.   A radiation detector comprising the scintillator material according to claim 1.   A radiation inspection apparatus comprising the radiation detector according to claim 5.

Images