WO2018235495A1

WO2018235495A1 - Storage phosphor, method for manufacturing storage phosphor, radiation detection element, personal dosimeter, and imaging plate

Info

Publication number: WO2018235495A1
Application number: PCT/JP2018/019619
Authority: WO
Inventors: 康武早川; 大平　晃也; 健之柳田; 範明河口; 豪岡田; 智久大矢
Original assignee: Ntn株式会社; 国立大学法人奈良先端科学技術大学院大学
Priority date: 2017-06-19
Filing date: 2018-05-22
Publication date: 2018-12-27

Abstract

Provided are: a storage phosphor comprising a sintered body containing a lanthanoid element and silicon nitride; a method for manufacturing the storage phosphor; a radiation detection element comprising the storage phosphor; a personal dosimeter comprising the storage phosphor; and an imaging plate comprising the storage phosphor.

Description

Storage phosphor, method of manufacturing storage phosphor, radiation detection element, individual dose meter and imaging plate

The present invention relates to a storage phosphor, a method of manufacturing the storage phosphor, a radiation detection element including the storage phosphor, an individual exposure dose meter including the storage phosphor, and an imaging plate including the storage phosphor.

Storage phosphors are widely used in radiation detection elements. The radiation detection element in the present invention represents an object having a function of detecting radiation. Radiation detection elements using storage phosphors have a wide range of application fields such as medicine, security and radiation protection. Personal exposure dosimeters in the field of radiation protection, imaging plates in medical image diagnosis, radiation environment monitoring, etc. are examples of radiation detection elements using typical storage phosphors. As existing storage phosphors, LiF: Mg, Ti mounted on thermoluminescent (TL) dosimeter, Al ₂ O ₃ : C mounted on photostimulated luminescence (OSL) dosimeter, radio photoluminescence (RPL) dosimeter An Ag-added phosphate glass to be mounted and BaFBr: Eu to be mounted on an imaging plate are known.

Non-Patent Document 1 describes that an alkaline earth metal halide based phosphor BaBrCl: Eu ²⁺ can be suitably used as a storage phosphor in medical imaging. Non-Patent Document 2 describes that Al ₂ O ₃ : C, which is an inorganic phosphor, can be suitably used as a storage phosphor in a personal exposure dose meter. However, many of these existing storage phosphors do not have sufficient mechanical properties, and enrichment of storage phosphors with good mechanical properties is desired.

An object of the present invention is to provide a novel storage phosphor having good mechanical properties, which comprises a sintered body containing a lanthanoid element and silicon nitride, and a method for producing the storage phosphor, Contribute to the enrichment of options.

Another object of the present invention is to provide a radiation detection element including the storage phosphor, an individual exposure dosimeter including the storage phosphor, and an imaging plate including the storage phosphor.

The present invention provides a storage phosphor as described below, and a radiation detection element using the storage phosphor, in particular, a personal exposure dosimeter and an imaging plate.

[1] A storage phosphor comprising a sintered body containing a lanthanoid element and silicon nitride.
[2] The storage fluorescence according to [1], wherein the lanthanoid element is at least one selected from the group consisting of dysprosium, ytterbium, cerium, europium, thulium, terbium, neodymium, praseodymium, samarium, holmium and erbium body.

[3] The storage phosphor according to [1] or [2], comprising a sintered body containing the lanthanoid compound having the lanthanoid element and the silicon nitride.

[4] A step of mixing a lanthanoid compound having a lanthanoid element and silicon nitride to obtain a mixture containing the lanthanoid compound and the silicon nitride, and forming the mixture to obtain a formed body of the mixture, Sintering the formed body to obtain a sintered body of the formed body, wherein the lanthanoid element is composed of dysprosium, ytterbium, cerium, europium, thulium, terbium, neodymium, praseodymium, samarium, holmium and erbium The content of the lanthanoid compound contained in the mixture is at least one selected from the group: 0.1 parts by mass relative to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture. A method of producing a storage phosphor, which is 5 to 15 parts by mass.

[5] Following (1) to (5):
(1) The lanthanoid compound is Dy ₂ O ₃ ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(2) The lanthanoid compound is Yb ₂ O ₃ ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(3) the lanthanoid compound is CeO ₂ ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(4) The lanthanoid compound is Eu ₂ O ₃ ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(5) The lanthanoid compound is Tm ₂ O ₃ ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
The manufacturing method of the storage fluorescent substance as described in [4] which satisfy | fills either.

[6] The method for producing a storage phosphor according to [4] or [5], wherein the sintering is performed in a state in which the periphery of the molded body is surrounded by a ceramic.

[7] The production method according to [6], wherein the ceramic is boron nitride.
[8] A radiation detection element comprising the storage phosphor according to any one of [1] to [3].

[9] A personal exposure dosimeter comprising the storage phosphor according to any one of [1] to [3].

[10] An imaging plate comprising the storage phosphor according to any one of [1] to [3].

It is possible to provide a novel storage phosphor having good mechanical properties, which comprises a sintered body containing a lanthanoid element and silicon nitride, and a method of manufacturing the storage phosphor, and the storage phosphor of choice It can contribute to enrichment. Further, it is possible to provide a radiation detecting element including the storage phosphor, an individual exposure dosimeter including the storage phosphor, and an imaging plate including the storage phosphor.

It is a schematic diagram which shows the sintering method of the molded object in Experimental example 82 and 83. FIG.

In the present specification, the meanings of the following terms are as follows.
(1) "Storage phosphor" refers to a material that stores energy of irradiated radiation and then emits light at an intensity according to the irradiation amount.

(2) "Radiation" means X-rays, gamma rays, alpha rays, beta rays, neutron rays and the like.
(3) The term "lanthanoid element" is generally a generic name of atomic number 57 to 71, that is, 15 elements from lanthanum (La) to lutetium (Lu), but in the present specification, an atom having no stable isotope A generic term of 14 elements excluding the 61 promethium (Pm) element is meant.

(4) "Good sinterability" refers to the property that a compact sintered body is easily produced even at a lower sintering temperature, or the property that a denser sintered body is easily produced even at the same sintering temperature.

(5) “A to B” (A and B are numerical values) means A or more and B or less.
(6) The "radiation detection element" is an object having a function of detecting radiation. Examples of radiation detection elements using storage phosphors include, for example, “individual dose meter” and “imaging plate”. The storage phosphor has the property of storing energy of irradiated radiation, and the detection unit operates with no power supply, and thus is suitable for these radiation detection elements.

(7) The “individual dose dosimeter” is, for example, an element for portable use of a radiation worker in a nuclear power plant or the like to measure the amount of radiation irradiated at the time of carrying.

(8) The “imaging plate” is a type of radiation image detector, and may be, for example, a form in which a storage phosphor is applied on a support plate such as plastic.

(9) "Ceramics" refers to a sintered product of an inorganic compound or a sintered product of a molded product of an inorganic compound.

<Storage phosphor>
The storage phosphor is made of a sintered body containing a lanthanoid element and silicon nitride. Hereinafter, the lanthanoid element and silicon nitride, and other components (impurities) that may be optionally contained will be described.
(Lanthanoid element)
The lanthanoid element plays a role as an activator. The storage phosphor may contain only one type of lanthanoid element, or may contain two or more types. When the storage fluorescent substance contains a lanthanoid element, the storage fluorescent substance can emit fluorescence that accompanies the electron orbital transition of the lanthanoid element ion due to the radiation irradiation.

The lanthanoid element is preferably at least one selected from the above 14 elements. That is, the storage phosphor according to the present invention includes lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb) At least one member selected from the group consisting of dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), silicon nitride and silicon nitride; And a silicon nitride, which is at least one selected from the group consisting of Dy, Yb, Ce, Eu, Tm, Tb, Nd, Pr, Sm, Ho and Er, and silicon nitride. It is more preferable to consist of a sintered body containing and.

The lanthanoid element can be contained in the storage phosphor as, for example, a metal lanthanoid or a lanthanoid compound such as a lanthanoid oxide. From the viewpoint of obtaining a storage phosphor having good sinterability, the storage phosphor preferably contains a lanthanoid compound having a lanthanoid element. That is, the storage phosphor according to the present invention is preferably a storage phosphor made of a sintered body containing a lanthanoid compound having a lanthanoid element and silicon nitride.
(Silicon nitride)
Silicon nitride (Si ₃ N ₄ ) is widely applied to bearings, turbine blades, and cutting tools, and has high mechanical properties and thermal shock resistance. Silicon nitride is usually contained in the storage phosphor as a sintered body (silicon nitride ceramic). Therefore, when the storage phosphor contains silicon nitride, a storage phosphor having excellent mechanical properties and thermal shock resistance can be obtained. In addition, silicon nitride is preferable also from the viewpoint of resources because it does not contain a rare element. (Other ingredients that may optionally be included)
The storage phosphor may further contain other components (impurities) other than the lanthanoid element and silicon nitride. Other components include unavoidable impurities which are unintentionally contained in the production process, and additives which are intentionally added. The unavoidable impurities and the additives may include impurity elements such as oxygen (O), carbon (C), aluminum (Al), magnesium (Mg) and the like.

Examples of the additive include a sintering aid for obtaining a storage phosphor having good sinterability. The storage phosphor can comprise one or more sintering aids. The sintering _aid, Al ₂ O 3, _MgO, known sintering aid such as Y 2 _{O 3} and the like.

<Method of Manufacturing Storage Phosphor>
The method of manufacturing a storage phosphor according to the present disclosure includes the following steps (1) to (3). Hereinafter, steps (1) to (3) will be described.

(1) a step of mixing a lanthanoid compound having a lanthanoid element and silicon nitride to obtain a mixture containing the lanthanoid compound and silicon nitride (first step);
(2) a step of forming the mixture obtained in the above step to obtain a formed body of the mixture (second step);
(3) A step (third step) of sintering the compact obtained in the above step to obtain a sintered body (storage phosphor) of the compact.

<< First step >>
This step is a step of obtaining a mixture containing a lanthanoid compound and silicon nitride by mixing a lanthanoid compound having a lanthanoid element and silicon nitride. The mixture containing a lanthanoid compound and silicon nitride may be in the form of powder (hereinafter, a powdery mixture containing a lanthanoid compound and silicon nitride is also referred to as “raw material powder”).
(Lanthanoid element)
The lanthanoid element is at least one selected from the group consisting of Dy, Yb, Ce, Eu, Tm, Tb, Nd, Pr, Sm, Ho and Er.
(Content of lanthanoid compound in mixture)
The content of the lanthanoid compound contained in the above mixture is 0.5 to 15 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the above mixture. When the content of the lanthanoid compound contained in the above mixture is less than 0.5 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the above mixture, the manufactured storage phosphor is It may not be possible to obtain sufficient intensity of light emission. When the content of the lanthanoid compound contained in the above mixture is more than 15 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the above mixture, the mechanical of the manufactured storage phosphor It tends to lack strength. If the mechanical strength of the storage phosphor decreases, more rare raw materials will be used, which may lead to an increase in manufacturing cost.

When the lanthanoid compound is a lanthanoid oxide, it is preferable to satisfy any of the following (1) to (5) from the viewpoint of obtaining better sinterability without reducing the performance as a storage phosphor.

(1) a lanthanide compound _Dy 2 _{O 3,} the content of the lanthanoid compounds contained in the mixture _(Dy 2 _{O 3)} is a lanthanoid compound contained in the mixture and _(Dy 2 _{O 3)} and silicon nitride And 0.5 to 10 parts by mass (more preferably 1 to 5 parts by mass) with respect to 100 parts by mass of the total amount of

(2) a lanthanide compound _Yb 2 _{O 3,} the content of the lanthanoid compounds contained in the mixture _(Yb 2 _{O 3)} is a lanthanoid compound contained in the mixture and _(Yb 2 _{O 3)} and silicon nitride And 0.5 to 10 parts by mass (more preferably 1 to 5 parts by mass) with respect to 100 parts by mass of the total amount of

(3) lanthanide compound is CeO _2, the content of the lanthanoid compounds (CeO ₂₎ contained in the mixture, lanthanoid compounds contained in the mixture (CeO ₂₎ and a total amount of 100 parts by mass of the silicon nitride Relative to 0.5 to 10 parts by mass (more preferably 1 to 5 parts by mass).

(4) a lanthanide compound _Eu 2 _{O 3,} the content of the lanthanoid compounds contained in the mixture _(Eu 2 _{O 3)} is a lanthanoid compound contained in the mixture and _(Eu 2 _{O 3)} and silicon nitride And 0.5 to 10 parts by mass (more preferably 1 to 5 parts by mass) with respect to 100 parts by mass of the total amount of

(5) a lanthanide compound _Tm 2 _{O 3,} the content of the lanthanoid compound in included in the mixture _(Tm 2 _{O 3)} is a lanthanoid compound contained in the mixture _(Tm 2 _{O 3)} and silicon nitride And 0.5 to 10 parts by mass (more preferably 1 to 5 parts by mass) with respect to 100 parts by mass in total.
That is, when the lanthanoid compound is any of Dy ₂ O ₃ , Yb ₂ O ₃ , CeO ₂ , Eu ₂ O ₃ , and Tm ₂ O _{3 in} the method for producing a storage phosphor according to the present invention, the lanthanoid compound and The content of the lanthanoid compound in the mixture obtained in the step of obtaining a mixture by mixing it with silicon nitride (the first step) is 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the mixture. The amount is preferably 0.5 to 10 parts by mass. (Additional amount of other components that may optionally be included)
The raw material powder may further contain other components (impurities) other than the lanthanoid compound and silicon nitride. Other components include unavoidable impurities which are unintentionally contained in the production process, and additives which are intentionally added. The unavoidable impurities and the additives may include impurity elements such as oxygen (O), carbon (C), aluminum (Al), magnesium (Mg) and the like. From the viewpoint of obtaining a storage phosphor having good sinterability, the content of the impurity element is 20 parts by mass or less with respect to 100 parts by mass in total of the lanthanoid compound and silicon nitride contained in the raw material powder. Is preferred. However, when the impurity element is excessively contained, the emission intensity of the storage phosphor may be reduced. Therefore, the content of the impurity element is more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less, based on 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the raw material powder. .

Examples of the additive include a sintering aid for obtaining a storage phosphor having good sinterability. The storage phosphor can comprise one or more sintering aids. The sintering _aid, Al ₂ O 3, _MgO, known sintering aid such as Y 2 _{O 3} and the like. Although the addition amount of the sintering aid is not particularly limited, it is preferable that the addition amount be such that the emission intensity at the time of radiation excitation is not significantly reduced. The addition amount of the sintering aid to the raw material powder is preferably 20 parts by mass or less and 10 parts by mass or less based on 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the raw material powder. Is more preferable, and 5 parts by mass or less is even more preferable. Thereby, a storage phosphor having good sinterability can be obtained without reducing the performance as a storage phosphor.

In order to obtain a storage phosphor having good sinterability, the particle size and particle shape of the raw material powder may be adjusted. The adjustment method may, for example, be crushing or granulation.

For example, the particle size of primary particles of the raw material powder can be reduced to the micrometer order or less by grinding. Also, by granulation, the shape of secondary particles of the raw material powder can be changed from a shape with many corners to a rounded shape, or the particle diameter of the secondary particles can be made to a size of about 50 to 150 μm. In addition, the fine particle which can observe the clear boundary which can be identified by fine structure observation is called a primary particle, and the aggregate of a primary particle is called a secondary particle.

The grinding method and the granulation method may be any method. Examples of the grinding method include methods using mortar grinding, a ball mill, a stamp mill, a jet mill and the like. Further, in order to realize high control of particle diameter and particle shape, it may be crushed and granulated in multiple stages by using a plurality of crushing methods and granulation methods in combination. The raw material powder may be ground and granulated, but in order to reduce the manufacturing cost, it is preferable to grind and granulate in the state of a mixed powder in which a plurality of raw material powders are mixed. By the above method, a mixture of a lanthanoid compound and silicon nitride can be obtained.

Second step
This process is a process of shape | molding the mixture obtained at the 1st process, and obtaining a molded object. By molding a mixture of a lanthanoid compound and silicon nitride, the sinterability can be improved in the third step described later.

The molded body may be obtained, for example, by press-forming (pressure-forming) the raw material pulverized in the first step using a mechanical press, a hydraulic press, a hydraulic press, a cold isostatic press (CIP) or the like. it can. If necessary, for example, two or more types of pressing methods may be used in combination, such as hydraulic pressing after mechanical pressing. The molding method is not limited to press molding, and a general molding method such as injection molding or tape molding may be used.

The pressing conditions in the press molding are not particularly limited, but in the case of mechanical press molding using a mold, for example, it can be performed under the conditions of about 150 to 200 kgf / cm ² . In the case of CIP, for example, it can be carried out under the conditions of 1000 to 2000 kgf / cm ² . A molded object can be obtained by the above method.

An organic binder may be added to the raw material powder in order to enhance the moldability of the molded body. When adding an organic binder, it is preferable to perform a pre-sintering process before the 3rd process which sinters in order to suppress the performance deterioration by a residual organic substance. The pre-sintering step is a step of densifying the molded body while burning away the organic binder, and may be a heat treatment step at a temperature of 400 to 600 ° C., for example.

<< 3rd process >>
This step is a step of sintering the molded body obtained in the second step. The sintering method may be any sintering method such as pressureless sintering, gas pressure sintering, hot press sintering, hot isostatic pressing sintering, pulse current pressure sintering and the like. The sintering atmosphere is preferably an inert gas atmosphere such as nitrogen or argon from the viewpoint of preventing the oxidation of silicon contained in silicon nitride. The sintering conditions are preferably set appropriately in accordance with the composition of the molded body and the sintering apparatus used. The sintering temperature is preferably set to a temperature of about 70% of the melting point of the compact.

From the viewpoint of obtaining a dense sintered body, the sintering method is preferably gas pressure sintering under an inert gas atmosphere such as nitrogen. The conditions for gas pressure sintering are preferably set appropriately in accordance with the composition of the compact and the sintering apparatus used. The conditions for gas pressure sintering are, for example, a sintering temperature of 1700 to 1800 ° C. and a sintering time of 0.5 to 2 hours in a nitrogen atmosphere of 50 to 300 MPa.

From the viewpoint of production cost, the sintering method is preferably pressureless sintering. The conditions for pressureless sintering are preferably set appropriately in accordance with the composition of the compact and the sintering apparatus used. The conditions for normal pressure sintering are, for example, a sintering temperature of 1700 to 1800 ° C., and a sintering time of 1 to 10 hours (for example, about 6 hours) in a nitrogen atmosphere of 0.2 to 5 MPa (for example, 0.8 MPa).

From the viewpoint of atmosphere control, the ceramic may be surrounded by ceramics at the time of sintering. This can further improve the scintillator performance of the obtained scintillator. As said ceramics, nitride ceramics are mentioned. Examples of nitride ceramics include silicon nitride ceramics (Si ₃ N ₄ ), aluminum nitride ceramics (AlN), boron nitride ceramics (BN), titanium nitride ceramics (TiN), and the like. Among them, boron nitride ceramics (BN) are preferably used from the viewpoint of improving the scintillator performance. By surrounding the periphery of the formed body with a ceramic, it is expected that the volatilization of the lanthanoid element contained in the formed body at the time of sintering is suppressed. In the “state in which the periphery of the formed body is surrounded by the ceramic”, the ceramic member surrounding the periphery of the formed body may be disposed such that a space is formed between the formed body and the ceramic member. It may be in a state of being arranged to be in contact with the entire outer surface of the molded body, or may be in a state of being arranged to be in contact with only the outer surface of a part of the molded body.

Processing may be performed on the sintered body (ie, storage phosphor) obtained by sintering. Examples of the processing include cutting processing and shape adjustment processing such as polishing processing. According to the above method, a storage phosphor made of a sintered body containing a lanthanoid element and silicon nitride can be manufactured.

<Application of storage phosphor>
In the storage phosphor, the amount of fluorescence changes in accordance with the amount of irradiated radiation, so the amount of emitted radiation can be detected by measuring the amount of fluorescence. The principles of fluorescence include, for example, TL, OSL, and RPL. The storage phosphor according to the present invention can be suitably used, for example, in the radiation detection elements shown below, and in particular, in personal dosimeters and imaging plates.

<Radiation detection element>
The storage phosphor according to the present invention may be included in a radiation detection element. The storage phosphor according to the present invention has a radiation detection ability and can be suitably used in a radiation detection element using any conventionally known technique. Among the radiation detection elements, it can be particularly suitably used for an individual dose meter and an imaging plate.

<Individual dose meter>
The storage phosphor according to the present invention may be included in an individual dose meter. Known techniques associated with personal exposure dosimeters that include storage phosphors include, for example, filter techniques. The filter technology uses a personal exposure dosimeter with an open window without a filter, a window with one or more plastic filters, a window with one or more sheet metal filters with a storage phosphor. In this method, the energy of radiation irradiated to the storage phosphor is changed, and energy information of the irradiated radiation is obtained by comparing the respective measurement results. The storage phosphor according to the present invention can be suitably used, for example, in an individual dose meter using such a known technique.

<Imaging plate>
The storage phosphor according to the present invention may be included in an imaging plate. The configuration of the imaging plate may be a conventionally known configuration including, for example, a storage phosphor layer formed on a flat plastic substrate, and a transparent protective layer for preventing dirt and scratches on the surface of the storage phosphor. . The imaging plate having such a configuration can reduce physical impact by the flexibility of the plastic substrate, and can prevent stains and scratches while taking out light emission by the transparent protective layer. The storage phosphor according to the present invention can be suitably used, for example, in an imaging plate using such a conventionally known known technique.

Hereinafter, the present invention will be described more specifically by showing experimental examples, but the present invention is not limited by these examples.

<Experimental examples 1 to 77, 82, 83>
(1) Production of Storage Phosphor (Sintered Body) Various lanthanoid oxides (Dy ₂ O ₃ , Yb ₂ O ₃ , CeO ₂ , manufactured by Kojundo Chemical Laboratory Co., Ltd.) as lanthanoid compounds (lanthanoid element source). Eu ₂ O ₃ , Tm ₂ O ₃ , Tb ₂ O ₃ , Nd ₂ O ₃ , Pr ₂ O ₃ , Sm ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , all having a purity of 99.9% by mass, powder ), And Si ₃ N ₄ (trade name: SN-9FWS, powder) manufactured by Denka Co., Ltd. was prepared as silicon nitride. Each lanthanoid compound and Si ₃ N ₄ were mixed to obtain a powdery mixture (raw material powder). The content of the lanthanoid compound contained in the raw material powder is 0.01 parts by mass, 0.5 parts by mass, and 1 part by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and Si ₃ N ₄ contained in the raw material powder. Parts, 5 parts by mass, 10 parts by mass, 15 parts by mass, or 20 parts by mass. To each raw material powder, add silicon nitride balls with a particle size of 10 mm so that the volume is the same as that of the raw material powder, and add ethanol as a whole to a volume of about 1.5 times that of the raw material powder. Mixed time. After drying each obtained slurry with an evaporator, it ground using a mortar and a pestle. Thereafter, the crushed raw materials were obtained by classifying through a sieve of 425 μm mesh. Subsequently, each of the crushed raw materials was press-molded under the condition of 200 kgf / cm ² to obtain a molded body having a cylindrical shape (diameter 10 mm × height 4 mm). The obtained compact was sintered at atmospheric pressure under the conditions of 0.9 MPa and 1725 ° C. for 4 hours in a nitrogen atmosphere to obtain storage phosphors (sintered bodies) according to Experimental Examples 1 to 77. Further, as shown in FIG. 1, sintering is performed on a compact having the same composition as that of Experimental Examples 11 and 26 in a state in which the periphery of the compact is surrounded by boron nitride (BN). A storage phosphor (sintered body) was obtained.

The differences between the experimental examples are the type of lanthanoid compound contained in the raw material powder and the content of the lanthanoid compound contained in the raw material powder. Type of lanthanoid compound contained in raw material powder and content of lanthanoid compound contained in raw material powder relative to 100 parts by mass in total of lanthanoid compound and silicon nitride contained in raw material powder in each experimental example (parts by mass) Is as shown in Table 1.

Experimental Examples 78 to 81
The content of Al ₂ O ₃ as a sintering aid is 5 parts by mass (Experimental Example 78) and 10 parts by mass (Experimental Example) with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the raw material powder. 79), 20 parts by mass (Example 80) and 25 parts by mass (Example 81), except that Al ₂ O ₃ was further added to the raw material powder, under the same conditions as in Example 2. Storage phosphors were produced, and storage phosphors according to Experimental Examples 78 to 81 were obtained.

(2) Evaluation of light emission performance of storage phosphors With respect to storage phosphors according to each experimental example, it is examined whether or not light is emitted with sufficiently high intensity by thermal stimulation after irradiation (hereinafter also referred to as “light emission performance”) It was evaluated whether it functions as a storage fluorescent substance. The specific evaluation method is as follows.

Using an X-ray generator (Spellman, Monoblock XRB80P & N200X4550) as a radiation source, the tube voltage is 40 kV, the tube current is 5.2 mA, and an amount of air absorbed dose equivalent to 1 Gy (gray) is stored The phosphor was irradiated.

About the sample (storage fluorescent substance) which irradiated the radiation, the thermoluminescent (TL) intensity | strength was measured, raising temperature, using the thermoluminescent measuring apparatus (made by nanoGray, TL-2000). The applied temperature range when measuring the TL intensity was 50 ° C. to 490 ° C., and the temperature rise rate was 1 ° C./sec, and a graph (glow curve) was measured according to the applied temperature and the emission intensity. In the measurement result of the glow curve obtained in this manner, the horizontal axis represents the applied temperature (° C.), and the vertical axis represents the charge (nC). The unit of the vertical axis, nC, represents nanocoulombs, which means 10 minus 9 coulombs. One coulomb is a charge (electric quantity) carried by a current of one ampere per second, and depends on a current value measured by a photomultiplier which is a light receiver of the present measuring apparatus. This current value also increases in accordance with the amount of background noise in addition to the thermal fluorescence (TL) intensity of the storage phosphor, so from the obtained measurement results, the result measured in the absence of a sample is referred to as background noise. The influence of background noise was removed by subtracting as the amount of V, and the abscissa represents the applied temperature (° C.), and the ordinate represents the glow curve of TL intensity (nC). Furthermore, the value of the vertical axis of the glow curve obtained in this manner is summed in the range of applied temperature of 50 ° C. to 490 ° C. to obtain an integrated value of TL intensity. The integrated values of the obtained TL intensities are shown in Table 1 for Experimental Examples 1 to 77, 82 and 83, and in Table 2 for Experimental Examples 78 to 81. The higher the integrated value is, the better the light emission performance is.

(3) Evaluation of mechanical strength of storage fluorescent substance About the storage fluorescent substance which concerns on each experiment example, it was evaluated whether it had sufficient mechanical strength as a storage fluorescent substance. As a specific evaluation method, the storage phosphor according to each experimental example was rubbed on paper, and it was observed whether or not the storage phosphor collapsed. The storage phosphor according to each experimental example did not collapse even when rubbed on paper, or was extremely fine even if it collapsed. This indicates that the storage phosphor according to the present invention has good mechanical properties.

<Discussion>
From the results of each experimental example in Table 1, it can be understood that the storage phosphor made of a sintered body containing a lanthanoid element and silicon nitride has sufficient light emission performance as a storage phosphor. In addition, as described above, each experimental storage phosphor had sufficient mechanical strength. That is, the storage phosphor according to the present application is a novel storage phosphor having good mechanical properties, and enrichment of the storage phosphor is achieved.

In Table 1, Experimental Examples 2 to 6 in which the content of the lanthanoid compound contained in the raw material powder is 0.5 to 15 parts by mass with respect to 100 parts by mass of the total of the lanthanoid compound and silicon nitride contained in the raw material powder. , 9 to 13, 16 to 20, 23 to 27, 30 to 34, 37 to 41, 44 to 48, 51 to 55, 58 to 62, 65 to 69, 72 to 76, 82, 83 It is shown that the light emitting performance is excellent, and the content of the lanthanoid compound contained in the raw material powder is 1 to 5 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the raw material powder. Examples 3, 4, 10, 11, 17, 18, 24, 25, 25, 32, 32, 38, 39, 45, 46, 52, 53, 59, 60, 66, 67, 73, 74 and 82. Strike Over di phosphors, it has been shown to have a particularly excellent luminescence performance. Although the cause of the change in the integrated value of the TL strength depending on the content of the lanthanoid compound contained in the raw material powder is not clear as such, the change in the sinterability of silicon nitride caused by the addition of the lanthanoid element affects There is a possibility.

Moreover, it was shown from Table 1 that the optimum content at which the integrated value of the TL intensity is maximum is different for each lanthanoid compound. Specifically, when the lanthanoid compound is Dy ₂ O ₃ , Yb ₂ O ₃ , Tb ₂ O ₃ , Nd ₂ O ₃ , Ho ₂ O ₃ or Er ₂ O ₃ , the lanthanoid compound contained in the raw material powder The integrated value of the TL strengths became maximum when the content of S is 5 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the raw material powder. In contrast, when the lanthanoid compound is CeO ₂ , Eu ₂ O ₃ , Tm ₂ O ₃ , Pr ₂ O ₃ , and Sm ₂ O ₃ , the content of the lanthanoid compound contained in the raw material powder is contained in the raw material powder The integrated value of the TL strength was maximum when the amount was 1 part by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride.

Further, from the comparison of Example 11 and Example 82 in Table 1 and the comparison of Example 26 and Example 83, sintering is performed in a state where the periphery of the formed body is surrounded by ceramics (BN). It was confirmed that the emission intensity was improved. There was no change in the peak wavelength of light. In Example 11 and Example 26, it is considered that part of the lanthanoid element was volatilized at the time of sintering. In Example 82 and Example 83, volatilization of the lanthanoid element during sintering is suppressed by surrounding the periphery of the formed body with a ceramic (BN), and the emission intensity is improved as compared with Example 11 and Example 26. It is considered to be

As shown in Table 2, integrated values of the TL intensities of Experimental Examples 78 to 81 were 1267, 721, 440, and 47 (nC), respectively. In the experimental example 81, the integrated value of the TL intensity decreased significantly, but in the experimental examples 78 to 80, the integrated value of the TL intensity did not decrease significantly. From this, in the method for producing a storage phosphor according to the present invention, 20 parts by mass or less of the conventionally known sintering aid is contained with respect to 100 parts by mass of the total amount of the lanthanoid compound and silicon nitride contained in the raw material powder. It was shown that it may be contained, 10 parts by mass or less may be contained, or 5 parts by mass or less may be contained.

The storage phosphor according to the present invention may have good mechanical properties in place of the alkaline earth metal halide-based phosphor BaBrCl: Eu ²⁺ and the inorganic phosphor Al ₂ O ₃ : C. Is expected as a stable storage phosphor.

11 compacts, 12 ceramics (BN).

Claims

A storage phosphor comprising a sintered body containing a lanthanoid element and silicon nitride.
The storage phosphor according to claim 1, wherein the lanthanoid element is at least one selected from the group consisting of dysprosium, ytterbium, cerium, europium, thulium, terbium, neodymium, praseodymium, samarium, holmium and erbium.
The storage fluorescent substance of Claim 1 or 2 which consists of a sintered compact containing the lanthanoid compound which has the said lanthanoid element, and the said silicon nitride.
Mixing a lanthanoid compound having a lanthanoid element and silicon nitride to obtain a mixture containing the lanthanoid compound and the silicon nitride;
Shaping the mixture to obtain a shaped body of the mixture;
Sintering the formed body to obtain a sintered body of the formed body,
The lanthanoid element is at least one selected from the group consisting of dysprosium, ytterbium, cerium, europium, thulium, terbium, neodymium, praseodymium, samarium, holmium and erbium,
The content of the lanthanoid compound contained in the mixture is 0.5 to 15 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
Storage phosphor manufacturing method.
The following (1) to (5):
(1) The lanthanoid compound is Dy 2 O 3 ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(2) The lanthanoid compound is Yb 2 O 3 ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(3) the lanthanoid compound is CeO 2 ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(4) The lanthanoid compound is Eu 2 O 3 ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
(5) The lanthanoid compound is Tm 2 O 3 ,
The content of the lanthanoid compound contained in the mixture is 0.5 to 10 parts by mass with respect to 100 parts by mass of the total amount of the lanthanoid compound and the silicon nitride contained in the mixture.
The manufacturing method of the storage fluorescent substance of Claim 4 which satisfy | fills either of these.
The method for manufacturing a storage phosphor according to claim 4, wherein the sintering is performed in a state in which the periphery of the compact is surrounded by a ceramic.
The method for manufacturing a storage phosphor according to claim 6, wherein the ceramic is boron nitride.
A radiation detection element comprising the storage phosphor according to any one of claims 1 to 3.
A personal exposure dosimeter comprising the storage phosphor according to any one of claims 1 to 3.
An imaging plate comprising the storage phosphor according to any one of claims 1 to 3.