Fluoride crystals, methods for producing them, phosphors, scintillators, laser elements, and magnetic refrigeration materials using them.

Abstract

To provide defect-controlled fluoride crystals, methods for producing the same, and their applications. [Solution] The fluoride crystal of the present invention contains cesium (Cs), rare earth element RE, and fluorine (F), and has the general formula CsRE2F 7-x The inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) contains at least hydrogen (H). The present invention relates to a method for producing fluoride crystals, which involves growing crystals by solvothermal method from a raw material containing a rare earth element RE and a raw material containing a fluorine element (F) in the presence of a mineralizing agent containing at least cesium element (Cs).

Description

Technical Field

[0001] The present invention relates to fluoride crystals, a method for producing the same, phosphors, scintillators, laser elements, and magnetic refrigeration materials using the same.

Background Art

[0002] Although there are various fluoride crystals, CsGd2F7 has been reported as a luminescent compound (see, for example, Patent Document 1). Patent Document 1 discloses that such a single crystal luminescent compound is produced by the Czochralski (CZ) method, the Bridgman method or the EFG method.

[0003] Generally, crystals obtained by these methods have defects and cracks may occur. Therefore, there is a need to develop crystals with suppressed defects and cracks, and a technique for growing such crystals.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide a fluoride crystal with controlled defects, a method for producing the same, and uses thereof.

Means for Solving the Problems

[0006] The fluoride crystal of the present invention contains cesium (Cs), a rare earth element RE, and a fluorine element (F), and at least a hydrogen element (H) in an inorganic crystal represented by the general formula CsRE2F 7-x (where x satisfies 0 ≦ x ≦ 0.5), thereby solving the above problems. The concentration of the hydrogen element is 1×10 14 atoms / cm 3 or more to 1×10 23 atoms / cm 3 and may be in the following range. The RE may be at least one element selected from the group consisting of scandium (Sc), yttrium (Y), cerium (Ce), praseodymium (Pr), lanthanum (La), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The RE may be at least one element selected from the group consisting of samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The inorganic crystal may have a triclinic crystal structure and may have the symmetry of the space group P1121 / b. The inorganic crystal may further contain an alkali metal element and / or an alkaline earth metal element other than the Cs. The concentration of the alkali metal element and / or the alkaline earth metal element is 1×10 12 atoms / cm 3 or more to 1×10 23 atoms / cm 3 and may be in the following range. The alkali metal element may be at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and francium (Fr). The alkaline earth metal element may be at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). The method for producing the above-mentioned fluoride crystals according to the present invention includes growing crystals by solvothermal method from a raw material containing a rare earth element RE and a raw material containing a fluorine element (F) in the presence of a mineralizing material containing at least cesium element (Cs), thereby solving the above-mentioned problems. The concentration of the mineralizing agent may be in the range of 1 M to 50 M. In growing crystals using the solvothermal method described above, the temperature may be in the range of 400°C to 800°C, and the maximum achievable pressure may be in the range of 25 MPa to 250 MPa. A mineralizing agent selected from the group consisting of a mineralizing agent containing an alkali metal element other than Cs, a mineralizing agent containing an alkaline earth metal element, a mineralizing agent containing a normal salt, and an acid mineralizing agent may be further included. The phosphor of the present invention contains the above-mentioned fluoride crystals, thereby solving the above-mentioned problems. The scintillator of the present invention contains the above-mentioned fluoride crystals, thereby solving the above-mentioned problems. The laser element according to the present invention contains the above-mentioned fluoride crystal, thereby solving the above-mentioned problems. The magnetic refrigeration material according to the present invention contains the above-mentioned fluoride crystals, thereby solving the above-mentioned problems. [Effects of the Invention]

[0007] The fluoride crystal of the present invention contains cesium (Cs), a rare earth element RE, and a fluorine element (F), and has the general formula CsRE2F 7-x Since the inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) contains at least hydrogen (H), the crystal structure can be controlled and crack formation can be suppressed. Such fluoride crystals can be used to provide phosphors, laser elements, magnetic refrigeration materials, scintillators, and birefringent materials, depending on the selection of RE.

[0008] The present invention's method for producing fluoride crystals allows for synthesis under lower temperature conditions compared to conventional methods such as the Czochralski process. As a result, the resulting crystals have controlled defects and a stable composition. Furthermore, the solvothermal method is suitable for mass production, making it practically advantageous. [Brief explanation of the drawing]

[0009] [Figure 1] A flowchart showing the manufacturing process of the fluoride crystals of the present invention. [Figure 2] Schematic diagram showing a light-emitting device using the fluoride crystal of the present invention. [Figure 3] Schematic diagram showing a magnetic refrigeration apparatus using fluoride crystals of the present invention. [Figure 4] Schematic diagram showing a radiation detector using the fluoride crystal of the present invention. [Figure 5] Figure showing an optical microscope image of the crystal in Example 1. [Figure 6] Figure showing an optical microscope image of the crystal in Example 2. [Figure 7] Figure showing an optical microscope image of the crystal in Example 3. [Figure 8] Figure showing an optical microscope image of the crystal in Example 4. [Figure 9] Figure showing the powder XRD pattern of the crystal in Example 1. [Figure 10] Figure showing the powder XRD pattern of the crystal in Example 2. [Figure 11] Figure showing the powder XRD pattern of the crystal in Example 3. [Figure 12] Figure showing the powder XRD pattern of the crystal in Example 4. [Figure 13] Figure showing the excitation and emission spectra of the crystal in Example 1. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. Similar elements will be given the same numbers, and their descriptions will be omitted. In this specification, numerical ranges represented by "~" mean a range that includes the numbers written before and after "~" as the lower limit and upper limit, respectively.

[0011] (Embodiment 1) Embodiment 1 details the fluoride crystal of the present invention and a method for producing the same.

[0012] The fluoride crystal of the present invention contains cesium (Cs), a rare earth element RE, and fluorine (F), and has the general formula CsRE2F 7-x The inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) contains at least hydrogen (H). Hereafter in this specification, the general formula CsRE2F 7-x Inorganic crystals represented by are simply called inorganic crystals. Since the crystal structure cannot be maintained if the parameter x exceeds 0.5, it is preferable that it be 0.5 or less. The parameter x preferably satisfies 0 ≤ x ≤ 0.25, and more preferably 0 ≤ x ≤ 0.1. Hereafter, for simplicity, the elements cesium, fluorine, and hydrogen will simply be referred to as cesium (Cs), fluorine (F), and hydrogen (H).

[0013] In the general formula above, Cs and RE are expressed in a 1:2 ratio, but if the crystal structure described later is maintained, even if the ratio does not perfectly satisfy 1:2 due to slight compositional deviations or measurement errors, the general formula CsRE2F 7-x It is assumed to be an inorganic crystal represented by [formula].

[0014] The fluoride crystal of the present invention, by containing hydrogen in the inorganic crystal, has controlled defects and can exhibit the inherent properties of the material. Depending on the selection of rare earth elements RE, the fluoride crystal of the present invention can exhibit high transmittance to light of specific wavelengths, emit light, emit laser light, exhibit magnetocaloric effects, or exhibit scintillation, and can therefore function as a phosphor, laser element, magnetic refrigeration material, or scintillator. Furthermore, because it exhibits transmittance to specific wavelengths, it can also function as an optical filter or window material. In addition, the fluoride crystal of the present invention exhibits different refractive indices depending on the direction of light vibration and the direction of incidence, and can therefore function as a birefringent material.

[0015] Rare earth elements (RE) are elements that include scandium and yttrium in addition to lanthanide elements, but more specifically, they are elements selected from the group consisting of scandium (Sc), yttrium (Y), cerium (Ce), praseodymium (Pr), lanthanum (La), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The rare earth element RE is preferably selected from the group consisting of samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Fluoride crystals are readily obtained from these elements.

[0016] The rare earth element RE is more preferably an element selected from the group consisting of Tb, Gd, Sm, and Lu. These elements are preferred because they exhibit excellent fluorescence properties, scintillation properties, laser properties, and magnetocaloric effects.

[0017] In the fluoride crystal of the present invention, preferably, the hydrogen concentration is 1 × 10⁻⁶ 14 atoms / cm 3 The above 1 x 10 23atoms / cm 3 The range is as follows. This allows for control of defects in the fluoride crystal. The hydrogen concentration is more preferably 1 × 10⁻⁶. 16 atoms / cm 3 The above 1 x 10 22 atoms / cm 3 The range is as follows. This allows for further control of defects in the fluoride crystal. In one example, the hydrogen concentration is 1 × 10⁻⁶. 18 atoms / cm 3 The above 1 x 10 21 atoms / cm 3 The following ranges are acceptable. In this specification, the hydrogen concentration is the value at a depth of 3 μm, measured using secondary ion mass spectrometry (SIMS).

[0018] In the fluoride crystal of the present invention, the inorganic crystal may further contain alkali metal elements and / or alkaline earth metal elements other than Cs. The inclusion of alkali metal elements and / or alkaline earth metal elements in the inorganic crystal can deactivate defects within the crystal. Hereafter, for simplicity, alkali metal elements and alkaline earth metal elements will simply be referred to as alkali metals and alkaline earth metals.

[0019] The alkali metal is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and francium (Fr), with K and / or Rb being preferred. This allows for the deactivation of defects within the crystal.

[0020] Alkaline earth metals are selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), with a preference being the group consisting of Ca, Sr, and Ba. This allows for the deactivation of defects within the crystal.

[0021] Alkali metals and alkaline earth metals may be used individually or in combination of two or more types.

[0022] The concentrations of alkali metals and / or alkaline earth metals other than Cs are preferably 1 × 10⁻⁶ 12 atoms / cm 3 The above 1 x 10 23 atoms / cm 3 The range is as follows, preferably 1 × 10 14 atoms / cm 3 The above 1 x 10 20 atoms / cm 3 The following range is possible. This allows for further deactivation of defects within the crystal. In one example, the concentration of alkali metals and / or alkaline earth metals is 1 × 10⁻⁶. 17 atoms / cm 3 The above 1 x 10 20 atoms / cm 3 The following ranges are acceptable. In this specification, the concentrations of alkali metals and alkaline earth metals are values ​​measured at a depth of 6 μm using secondary ion mass spectrometry (SIMS).

[0023] In a fluoride crystal according to one embodiment of the present invention, the inorganic crystal, in which the rare earth element RE is Tb and / or Gd, contains hydrogen, and optionally alkali metals and / or alkaline earth metals.

[0024] The inorganic crystal described above is preferably a triclinic crystal and has the symmetry of space group P1121 / b (space group 14 in the International Tables for Crystallography).

[0025] The above inorganic crystal preferably has lattice constants a, b, and c. a = 1.5956 ± 0.05 nm b = 1.5975 ± 0.05 nm c = 1.2436 ± 0.05 nm It may be within that range. Such fluoride crystals have controlled defects.

[0026] The above inorganic crystal is CsTb2F 7-x , CsGd2F 7-x , CsSm2F7-x ,CsLu2F 7-x , Cs(Tb,Gd)2F 7-x , Cs(Tb,Lu)2F 7-x , Cs(Tb,Gd,Sm)2F 7-x These crystals may contain hydrogen (H) and, if necessary, alkali metals other than Cs and / or alkaline earth metals. In this specification, descriptions such as (Tb,Gd) indicate that the elements of RE are present in any ratio.

[0027] For example, in one embodiment of the present invention, a fluoride crystal in which the rare earth element RE is Tb has defects in the crystal controlled, and when irradiated with deep ultraviolet to visible light, Tb 3+ Because it exhibits green emission, it functions as a phosphor or laser element. Furthermore, when the fluoride crystal is irradiated with radiation such as X-rays, it exhibits scintillation properties and functions as a scintillator. In particular, because it contains a large amount of Tb, which has a large atomic number, the density of the fluoride crystal increases, and the radiation stopping power becomes high.

[0028] Furthermore, since the above-mentioned fluoride crystal exhibits a transmittance of 70% or more in the wavelength range of 0.2 μm to 10.5 μm, it can be used in optical components such as prisms, lenses, and window materials.

[0029] For example, a fluoride crystal according to one embodiment of the present invention, in which the rare earth element RE is Gd, exhibits scintillation properties when irradiated with radiation such as X-rays, and therefore functions as a scintillator. Because defects are controlled, the number of light scattering centers in the crystal is also reduced, and an increase in the amount of light emitted can be expected. In particular, because it contains a large amount of Gd, which has a large atomic number, the density of the fluoride crystal increases, and the stopping power becomes high. Furthermore, since the transmittance of the above fluoride crystal is 70% or more in the wavelength range of 0.2 μm to 10.5 μm, it can be used in optical components such as prisms, lenses, and window materials.

[0030] Furthermore, because the concentration of Gd in the above-mentioned fluoride crystal is high, it can function as a magnetic refrigeration material.

[0031] The fluoride crystal of the present invention may contain, in addition to the rare earth element RE constituting the inorganic crystal, an activating element A that functions as a light-emitting center. This allows it to function as a laser element or a phosphor. Such an activating element A is at least one element selected from the group consisting of manganese (Mn), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), ytterbium (Yb), thulium (Tm), holmium (Ho), and erbium (Er), which are different from the rare earth element RE constituting the fluoride crystal. The content of activating element A is in the range of 0.01% to 5% relative to the rare earth element RE. Within this range, the fluoride crystal can maintain the crystalline structure of the inorganic compound.

[0032] For example, CsGd2F 7-x When a fluoride crystal containing at least hydrogen in the inorganic crystal represented by is activated with Pr or Tb, it becomes a visible light laser; when activated with Nd, it becomes a 1 μm band laser; when activated with Tm and / or Ho, it becomes a 2 μm band laser; when activated with Er, it becomes a 3 μm band laser; and when activated with Dy, it becomes a 4 μm band laser.

[0033] As explained above, the fluoride crystal of the present invention has the general formula CsRE2F 7-x Because the inorganic crystals represented by this formula contain hydrogen, defects within the crystal are controlled, and cracks are suppressed to the greatest extent possible, resulting in high-quality crystals. Therefore, when the crystals are cut according to their intended use, crack formation within the crystal can be effectively suppressed, resulting in excellent yield.

[0034] Next, a method for producing the fluoride crystals of the present invention will be described. Figure 1 shows a flowchart for manufacturing the fluoride crystals of the present invention.

[0035] Step S110: Crystals are grown by solvothermal method from raw materials containing rare earth elements RE and raw materials containing fluorine (F) in the presence of a mineralizing agent containing at least cesium (Cs).

[0036] As mentioned above, rare earth elements (RE) are elements selected from the group consisting of scandium (Sc), yttrium (Y), cerium (Ce), praseodymium (Pr), lanthanum (La), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Step S110 will be explained in detail below.

[0037] In step S110, the mineralizing agent containing cesium (Cs) can be a Cs halide, hydroxide, or inorganic salt (such as a carbonate), for example, CsOH, Cs2CO3, or CsF. The Cs mineralizing agent is preferably a Cs halide, as this promotes crystal growth. The Cs mineralizing agent is more preferably CsF, as this promotes crystal growth and makes it easier to obtain large crystals.

[0038] In step S110, the raw material containing the rare earth element RE can be elemental RE, oxides, hydroxides, halides (fluorides, chlorides, bromides, iodides, etc.), inorganic salts (sulfates, nitrates, carbonates, etc.), organic salts (acetates, etc.), etc. Compounds other than elemental RE may be anhydrous or hydrated. Preferably, the raw material containing RE is RE fluoride. This allows for the growth of large crystals.

[0039] In step S110, the raw material containing fluorine (F) can be an inorganic acid, organic acid, or fluoride of RE containing fluorine. Furthermore, fluoride of Cs can be used as the mineralizing agent containing Cs and the raw material containing F, or fluoride of RE can be used as the raw material containing RE and the raw material containing F.

[0040] For example, the fluoride crystal of the present invention is CsTb2F 7-x When the inorganic crystal represented by contains at least hydrogen, it is preferable to use Tb fluoride (TbF3) as the raw material containing RE and F, and CsF as the mineralizing agent containing Cs.

[0041] For example, the fluoride crystal of the present invention is CsGd2F 7-x When the inorganic crystal represented by contains at least hydrogen, it is preferable to use Gd fluoride (GdF3) as the raw material containing RE and F, and CsF as the mineralizing agent containing Cs.

[0042] For example, the fluoride crystal of the present invention is CsSm2F 7-x When the inorganic crystal represented by contains at least hydrogen, it is preferable to use Sm fluoride (SmF3) as the raw material containing RE and F, and CsF as the mineralizing agent containing Cs.

[0043] For example, the fluoride crystal of the present invention is CsLu2F 7-x When the inorganic crystal represented by contains at least hydrogen, it is preferable to use Lu fluoride (LuF3) as the raw material containing RE and F, and CsF as the mineralizing agent containing Cs. Using these raw materials promotes crystal growth and makes it easier to obtain large crystals.

[0044] Furthermore, when producing fluoride crystals activated by activating element A as the fluoride crystals of the present invention, a raw material containing at least one element selected from the group consisting of manganese (Mn), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium (Tb), dysprosium (Dy), ytterbium (Yb), thulium (Tm), holmium (Ho), and erbium (Er), different from the rare earth element RE that constitutes the fluoride crystals, may be used as a raw material. In this case as well, the same raw materials as the raw material containing RE may be used.

[0045] In step S110, a mineralizer may be further included, selected from the group consisting of mineralizers containing alkali metals other than Cs, mineralizers containing alkaline earth metals, mineralizers containing normal salts, and acid mineralizers. In this case as well, the mineralizers containing alkali metals and mineralizers containing alkaline earth metals are compounds containing alkali metals or alkaline earth metals, and for example, halides, hydroxides, inorganic salts (carbonates, etc.) of alkali metals or alkaline earth metals can be used.

[0046] Non-limiting examples of mineralizing agents include, for example, KOH, K2CO3, KF, RbOH, Rb2CO3, RbF, Ca(OH)2, CaCO3, CaF2, Sr(OH)2, SrCO3, SrF2, Ba(OH)2, BaCO3, and BaF2, and it is preferable to select at least one from the group consisting of these compounds. Among these, fluorides are preferred. This allows for production with a good yield.

[0047] The mineralizing agent for normal salts is a salt produced by the complete neutralization of the hydrogen atoms of the acid and the hydroxyl groups of the salt. Specifically, examples include, but are not limited to, sodium chloride, calcium sulfate, and sodium phosphate. Examples of mineralizing agents for acids include, but are not limited to, hydrochloric acid, nitric acid, sulfuric acid, and formic acid.

[0048] The method for preparing the solution (reaction solution) to be used in synthesis by the solvothermal method is not particularly limited. For example, if a raw material mixture is prepared, a solution of the mineralizer may be added to the raw material mixture, and may be further mixed as needed. Alternatively, the mineralizer (preferably in powder or tablet form) may be added to the raw material mixture, and may be further mixed as needed. Alternatively, the above raw materials may be added to an aqueous solution of the mineralizer and mixed as appropriate. Here, the concentration of the mineralizer in the final reaction solution is preferably 1M or more and 50M or less, more preferably 1M or more and 20M or less, and even more preferably 1M or more and 10M or less.

[0049] The solvent can be any protic polar solvent, including water or organic solvents such as alcohols. If water is used, tap water, distilled water, RO water, deionized water, or pure water (ultrapure water) can be used.

[0050] Here, the reaction conditions (specifically temperature conditions) of the solvothermal method can be adjusted by taking advantage of the fact that the pH of the reaction solution changes depending on the Cs contained in the mineralizer, the type of alkali metal and / or alkaline earth metal used as needed, and the concentration of the mineralizer. Although certain care is required when handling highly alkaline solutions, the desired reaction solution can be prepared by appropriately adjusting the concentration of the mineralizer. It is also preferable to select the type of mineralizer depending on the raw materials used and / or the type of constituent elements of the target fluoride crystal.

[0051] The reaction conditions for the solvothermal method are not particularly limited, and conditions used in conventional solvothermal methods can be applied. The temperature is preferably in the range of 400°C to 800°C. This allows for a high yield of the desired fluoride crystals. Preferably, the temperature is in the range of 450°C to 750°C, more preferably 500°C to 750°C, even more preferably 550°C to 750°C, and particularly preferably 550°C to 650°C. The pressure is preferably in the range of 25 MPa to 250 MPa. The pressure is preferably adjusted by the amount of protic solvent, such as water, contained in the reaction vessel.

[0052] The crystal growth time using the solvothermal method can be adjusted as appropriate to ensure the reaction is completed, depending on the type and amount of raw materials used. For example, the crystal growth time may be between 1 hour and 300 hours within the temperature range mentioned above.

[0053] Within the temperature range described above, two or more temperature conditions may be set to establish a predetermined temperature profile. Such a temperature profile may be designed with considerations such as improving the homogeneity and stability of the reaction solution and more efficiently generating the target fluoride crystals.

[0054] The manufacturing method of the present invention reacts the raw materials (or mixtures of raw materials) by solvothermal reaction at significantly lower temperatures and with gentler temperature gradients compared to the conventional Czochralski (CZ), Bridgman, or EFG methods, thus minimizing evaporation. Therefore, the crystals obtained by the manufacturing method of the present invention can significantly suppress the formation of defects in the crystal due to decomposition evaporation. In addition, in general, with solvothermal methods, the crystals obtained have the most stable composition, and although there is a possibility of a slight deviation from the target composition, even if such a deviation occurs, the difference from the target composition is considered to be very small and is adjustable. Furthermore, since the present invention does not require the use of expensive platinum crucibles essential for the CZ method, the manufacturing cost of the target crystal can be reduced.

[0055] The fluoride crystal of the present invention contains cesium (Cs), the rare earth element RE, and the element fluorine (F), and has the general formula CsRE2F 7-x Although the inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) has been described as containing at least hydrogen (H), the fluoride crystal of the present invention can also be described as a crystal containing at least rare earth element RE (RE is as described above), fluorine (F), cesium (Cs), and hydrogen (H) as constituent elements, and having the same crystal structure as the crystal represented by CsGd2F7.

[0056] Crystals having the same crystal structure as the crystal represented by CsGd2F7 include, as described later, the CsGd2F7 crystal itself, crystals in which the lattice constant and atomic positions have changed due to the replacement of constituent elements with other elements in the CsGd2F7 crystal, crystals in which some elements are missing, and crystals in which some elements are present in excess. Here, a case in which constituent elements are replaced with other elements is, for example, a case in which some or all of the Gd in the CsGd2F7 crystal is replaced with RE other than Gd.

[0057] The lattice constant of the CsGd2F7 crystal changes when its constituent elements are replaced by other elements, or when hydrogen and, if necessary, alkali metals and / or alkaline earth metals are dissolved in it. However, the atomic positions given by the crystal structure, the sites occupied by atoms, and their coordinates do not change so drastically that the chemical bonds between the skeletal atoms are broken.

[0058] In this invention, the length of the chemical bond calculated from the lattice constant and atomic coordinates obtained by Rietveld analysis of X-ray diffraction results using the space group P1121 / b is compared with the length of the chemical bond of the crystal shown in Table 3 below. If the difference is, for example, within ±5%, it is defined as the same crystal structure, and a determination is made as to whether it is the same crystal. This determination criterion is based on experimental results showing that if the chemical bond length changes by more than ±5%, the chemical bond breaks and a different crystal is formed.

[0059] Crystals having the same crystal structure as the crystal represented by CsGd2F7 may include CsGd2F7, CsTb2F7, CsSm2F7, CsEu2F7, CsDy2F7, CsHo2F7, CsEr2F7, CsTm2F7, CsYb2F7, CsLu2F7, Cs(Gd,Tb)2F7, Cs(Gd,Tb,Sm)2F7, Cs(Gd,Tb,Sm,Lu)2F7, etc.

[0060] (Embodiment 2) Embodiment 2 describes the applications of the fluoride crystals of the present invention.

[0061] Figure 2 is a schematic diagram showing a light-emitting device using the fluoride crystal of the present invention.

[0062] The light-emitting device 1 of the present invention comprises at least a light-emitting element 10, which is an LED or laser diode (LD) that emits purple to blue light, and a single-crystal phosphor 2 that is excited by the LED and emits light having a wavelength longer than the wavelength of purple to blue light. The single-crystal phosphor 2 is a fluoride crystal as described in Embodiment 1, so its description is omitted. In the following description, for simplicity, a light-emitting device equipped with an LED will be described, but the present invention may use an LD as the light source instead of an LED.

[0063] As shown in Figure 2, the light-emitting device 1 is generally configured to include a ceramic substrate 3, a light-emitting element (LED) 10 arranged on the ceramic substrate 3, and a main body 4 provided on the ceramic substrate in a wall-like manner around the light-emitting element 10.

[0064] The ceramic substrate 3 is a plate-shaped member made of a ceramic such as Al2O3. Wiring sections 31 and 32 made of a metal such as tungsten are patterned on its surface.

[0065] The main body 4 is a component made of white resin formed on a ceramic substrate 3, with an opening 4A formed in its center. The opening 4A is tapered, with the opening width gradually increasing from the ceramic substrate 3 side toward the outside. The inner surface of the opening 4A is a reflective surface 40 that reflects light from the light-emitting element 10 toward the outside.

[0066] The light-emitting element 10 has its n-side electrode (not shown) and p-side electrode (not shown) mounted on the wiring portions 31 and 32 of the ceramic substrate 3 by bumps and electrically connected. Such a light-emitting element 10 can be manufactured by known methods such as those described in Japanese Patent Application Publication No. 5-152609, Japanese Patent Application Publication No. 7-99345, and Japanese Patent Publication No. 2927279.

[0067] When power is applied to the light-emitting device 1, the light-emitting element 10 emits light, which is incident on the single-crystal phosphor 2. The single-crystal phosphor 2 is excited by the light emitted from the light-emitting element 10, and for example, the single-crystal phosphor 2 becomes CsTb2F 7-x If the inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) is a fluoride crystal containing at least hydrogen (H), then Tb 3+ It emits green light due to the light-emitting element 10. The light-emitting device 1 can emit light that is a mixture of light emitted from the light-emitting element 10 and fluorescence emitted from the single-crystal phosphor 2. For example, by combining the green-emitting single-crystal phosphor 2 with a red-emitting phosphor and a blue-emitting phosphor, a light-emitting device 1 that emits white light can be provided.

[0068] Figure 3 is a schematic diagram showing a magnetic refrigeration apparatus using the fluoride crystal of the present invention.

[0069] The magnetic refrigeration apparatus 300 further comprises an AMR bed 320 filled with magnetic refrigeration material, a magnetic field applying means 330 for applying a magnetic field to it, a cooling stage 390 for cooling an object to be cooled by cold temperature, and a heat exchanger 340 for dissipating the heat generated by the magnetic refrigeration material in the AMR bed 320. Here, the magnetic refrigeration material 301 contains fluoride crystals as described in Embodiment 1, but here it is CsGd2F7-x The inorganic crystal (where x satisfies 0 ≤ x ≤ 0.5) is assumed to be a fluoride crystal containing at least hydrogen (H). Due to the high concentration of Gd, it functions as a magnetic refrigeration material.

[0070] The magnetic field application means 330 can be any means used to apply a magnetic field to the AMR bed 320, and it is practical to use a magnetic field with an intensity of approximately 1 to 10 Tesla, for example. A superconducting magnet, a permanent magnet, etc., can be used as the magnetic field application means 330. Furthermore, the relative position between the magnetic field application means 330 and the AMR bed 320 can be changed by a drive mechanism (not shown), thereby changing the magnitude of the magnetic field applied to the AMR bed 320.

[0071] A pre-cooling stage 360 ​​is provided on the high-temperature side of the AMR bed 320, and an 80K shield 370 is connected to the low-temperature side of the pre-cooling stage 360, while a 300K shield 380 is connected to the high-temperature side of the pre-cooling stage 360. Furthermore, a cooling stage 390 is provided on the low-temperature side of the AMR bed 320, and a liquefaction container 350 is provided, thermally connected to the cooling stage 390. In other words, the liquefaction container 350 is the object being cooled. The AMR bed 320 is also provided with an inlet and outlet for the heat-transporting refrigerant, and is structured to allow the heat-transporting refrigerant to flow back and forth inside the AMR bed 320 through the gaps in the magnetic refrigeration material 301.

[0072] The liquefaction container 350 is supplied with the gas 310 to be liquefied (for example, hydrogen, helium (He), etc.) from a tank (not shown).

[0073] The magnetic refrigeration apparatus 300 of the present invention operates as follows and can produce liquid hydrogen or gas-cool it. First, a magnetic field is applied to the AMR bed 320 filled with magnetic refrigeration material 301 by the magnetic field application means 330 to raise the temperature of the magnetic refrigeration material 301.

[0074] Next, the heat-transporting refrigerant is flowed in a direction 300A from the low-temperature end to the high-temperature end of the AMR bed 320. The heat-transporting refrigerant exchanges heat with the magnetic refrigeration material 301 filled inside the AMR bed 320, receiving heat as it flows through the gaps in the magnetic refrigeration material 301 and flows out from the high-temperature end of the AMR bed 320. The heat-transporting refrigerant that has flowed out from the high-temperature end of the AMR bed 320 flows into the heat exchanger 340, which dissipates heat via the pre-cooling stage 360, and the excess heat is dissipated to the outside.

[0075] Next, the magnetic field of the AMR bed 320, which is filled with magnetic refrigeration material 301, is removed (reduced) to lower the temperature of the magnetic refrigeration material 301. The heat transport refrigerant is flowed in a direction 300B from the high-temperature end to the low-temperature end of the AMR bed 320. The heat transport refrigerant flows into the high-temperature end of the AMR bed 320 via the pre-cooling stage 360, and while being cooled by heat exchange with the magnetic refrigeration material 301 filled inside, it flows through the gaps in the magnetic refrigeration material 301 and reaches the low-temperature end of the AMR bed 320. The flow of the heat transport refrigerant is driven by a refrigerant driving means (not shown). The refrigerant driving means is not particularly limited as long as it can drive an oscillating flow that reciprocates the heat transport refrigerant in synchronization with the AMR cycle, and examples include a piston, a blower and valve combination.

[0076] When the temperature at the low-temperature end of the AMR bed 320 drops below the boiling point of liquid hydrogen (20K at atmospheric pressure), the hydrogen gas supplied to the liquefaction container 350 is cooled and concentrated through heat exchange with the cooling stage 390 located on the low-temperature end side of the AMR bed 320.

[0077] This process is repeated, and the gas inside the liquefaction container 350 is periodically liquefied or cooled. Although the explanation has so far described the magnetic refrigeration material 301 as containing only the fluoride crystal of the present invention, by appropriately combining multiple magnetic refrigeration materials having different peak temperatures, taking into account the temperature dependence characteristics of the magnetic entropy change, and arranging them sequentially in order of operating temperature range, multiple highly efficient thermal cycles can be combined, making it possible to efficiently cool, for example, from high temperatures to extremely low temperatures of 20K or less.

[0078] Figure 4 is a schematic diagram showing a radiation detector using the fluoride crystal of the present invention.

[0079] The radiation detector 400 comprises a scintillator 410 and a photoelectron converter 420 that detects light L emitted from the scintillator 410 and converts it into an electrical signal. The scintillator 410 contains the fluoride crystal described in Embodiment 1, so its description is omitted, but here it is CsGd2F 7-x The inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5) is assumed to be a fluoride crystal containing at least hydrogen (H). Because it contains many Gd atoms with high atomic numbers, the density of the fluoride crystal is high, and a large amount of luminescence can be expected.

[0080] The photoelectron converter 420 is, for example, a photomultiplier tube (PMT), silicon photomultiplier (SiPM), solid-state image sensor (CCD), avalanche photodiode (APD), multipixel photon counter (MPPC), etc.

[0081] When radiation is irradiated onto the radiation detector 400, the scintillator 410 is excited and emits light L. The photoelectron converter 420 detects light L and converts it into an electrical signal. By using such a radiation detector 400 and combining it with a radiation source that irradiates a subject with radiation, a radiation inspection device can also be provided.

[0082] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. [Examples]

[0083] [Crystal Manufacturing] <Examples 1-4> In Examples 1 to 4, fluoride crystals were grown under the conditions shown in Table 1.

[0084] In Examples 1 to 4, crystals were grown by solvothermal method in the presence of cesium fluoride (CsF, Furuuchi Chemical Co., Ltd.) as a mineralizing agent and F-containing raw material, and from TbF3 powder, GdF3 powder, SmF3 powder, and LuF3 powder (Furuuchi Chemical Co., Ltd.) as RE-containing raw materials (Step S110 in Figure 1).

[0085] In detail, TbF3 powder, GdF3 powder, SmF3 powder, or LuF3 powder, CsF powder, and pure water (0.6 mL) were placed in a silver ampoule (5 mm in diameter x 10 cm in length) and sealed. The CsF powder was mixed with 0.6 mL of pure water to make a 5 mM aqueous solution. The sealed ampoule was then placed in a reaction vessel containing pure water, and the solvothermal method was carried out.

[0086] The solvothermal synthesis conditions involved heating to 600°C over 12 hours, holding at the maximum pressure shown in Table 1 for the time shown in Table 1, and then rapidly cooling to room temperature. Crystals of Examples 1 to 4 were obtained in this manner.

[0087] [Table 1]

[0088] [Crystal Analysis] <Microscopic observation> The crystals from Examples 1 to 4 were observed using an optical microscope. The results are shown in Figures 5 to 8. Figure 5 shows an optical microscope image of the crystal from Example 1. Figure 6 shows an optical microscope image of the crystal from Example 2. Figure 7 shows an optical microscope image of the crystal from Example 3. Figure 8 shows an optical microscope image of the crystal from Example 4.

[0089] Figures 5 to 8 show that bulk crystals can be obtained by performing the solvothermal method described in Figure 1. All crystals exhibited high transparency and no cracks were observed under microscopic observation. Due to their transparency, they can be applied to optical components such as prisms, lenses, window materials, and birefringent materials.

[0090] <X-ray Diffraction Analysis> Powder samples were prepared from the crystals of Examples 1 to 2, subjected to powder X-ray diffraction measurement, and subjected to structural analysis. The results are shown in FIGS. 9 to 12 and Tables 2 to 3.

[0091] FIG. 9 is a diagram showing the powder XRD pattern of the crystal of Example 1. FIG. 10 is a diagram showing the powder XRD pattern of the crystal of Example 2. FIG. 11 is a diagram showing the powder XRD pattern of the crystal of Example 3. FIG. 12 is a diagram showing the powder XRD pattern of the crystal of Example 4.

[0092] The powder XRD patterns of FIGS. 9 to 12 also show the results of simulation. According to FIG. 9, the peak positions (angle 2θ) and intensities (normalized intensities) of the XRD pattern of the crystal of Example 1 coincide with the XRD pattern by simulation of CsTb2F7, and no second phase was observed. Further, as a result of the crystal structure analysis of the crystal of Example 1, the crystal structure parameters shown in Table 2 were obtained. From this, it was confirmed that the crystal of Example 1 contains Cs, Tb, and F, is a triclinic crystal, and belongs to the symmetry of the space group P1121 / b.

[0093]

Table 2

[0094] According to FIG. 10, the peak positions (angle 2θ) and intensities (normalized intensities) of the XRD pattern of the crystal of Example 2 coincide with the XRD pattern by simulation of CsGd2F7, and no second phase was observed. Further, as a result of the crystal structure analysis of the crystal of Example 2, the crystal structure parameters shown in Table 3 were obtained. From this, it was confirmed that the crystal of Example 2 contains Cs, Gd, and F, is a triclinic crystal, and belongs to the symmetry of the space group P1121 / b.

[0095]

Table 3

[0096] As shown in Figure 11, the peak position (angle 2θ) and intensity (normalized intensity) of the XRD pattern of the crystal in Example 3 matched the XRD pattern obtained from the simulation of CsGd2F7, and no second phase was observed. Furthermore, the crystal structure analysis of the crystal in Example 3 confirmed that it contains Cs, Sm, and F, is a triclinic crystal, and belongs to the symmetry of space group P1121 / b.

[0097] As shown in Figure 12, the peak position (angle 2θ) and intensity (normalized intensity) of the XRD pattern of the crystal in Example 4 matched the XRD pattern obtained from the simulation of CsGd2F7, and no second phase was observed. Furthermore, the crystal structure analysis of the crystal in Example 4 confirmed that it contains Cs, Lu, and F, is a triclinic crystal, and belongs to the symmetry of space group P1121 / b.

[0098] The lattice constants a, b, and c of the crystals in Examples 1 to 4 are, respectively: a = 1.5956 ± 0.05 nm b = 1.5975 ± 0.05 nm c = 1.2436 ± 0.05 nm It met the requirements.

[0099] CsSm2F7 and CsLu2F7, which are triclinic crystals belonging to the space group P1121 / b symmetry, have not been reported to date, and the inventors of this invention are the first to successfully synthesize and discover these crystals. Furthermore, since fluoride crystals with RE Sm were obtained in Example 3 and fluoride crystals with RE Lu were obtained in Example 4, it is suggested that by employing the method shown in Figure 1, the fluoride crystals of the present invention can be obtained using various rare earth element REs, as can be seen from the periodic table.

[0100] Furthermore, by comparing Figure 10 with a comparable substance, a simple determination can be made as to whether or not it is the fluoride crystal of the present invention. It is advisable to make this determination based on about 10 peaks with strong diffraction intensity as the main peaks. In this sense, Table 2 is important as it serves as a reference for identifying the fluoride crystal of the present invention. In addition, the crystal structure of the fluoride crystal of the present invention can be approximated using other crystal systems of the triclinic crystal, in which case it will be expressed using different space groups, lattice constants, and plane indices, but the X-ray diffraction results (e.g., Figure 10) and crystal structure will remain the same, and the identification method and identification results will also be the same. For this reason, in this invention, X-ray diffraction analysis will be performed as if it were a triclinic crystal.

[0101] <Secondary Ion Mass Spectrometry> For the crystals in Examples 1 to 4, the hydrogen (H) concentration was measured using a secondary ion mass spectrometer (Cameca, IMS-6F) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS, IonTOF). As a result, the hydrogen concentration of the crystals in Examples 1 to 4 was 1 × 10⁻¹⁶ at a depth of 3 μm. 16 atoms / cm 3 The above 1 x 10 23 atoms / cm 3 It was found to be within the following range.

[0102] Based on the above, by performing the solvothermal method shown in Figure 1, a substance containing cesium (Cs), the rare earth element RE, and fluorine (F) is obtained, with the general formula CsRE2F. 7-x It was shown that fluoride crystals containing at least hydrogen (H) can be obtained from inorganic crystals represented by (where x satisfies 0 ≤ x ≤ 0.5). Similarly, it was shown that fluoride crystals containing at least rare earth elements RE, fluorine (F), cesium (Cs), and hydrogen (H) as constituent elements, and having the same crystal structure as the crystal represented by CsGd2F7, can be obtained.

[0103] Furthermore, the crystal in Example 1 was a fluoride crystal containing hydrogen in the CsTb2F7 crystal, the crystal in Example 2 was a fluoride crystal containing hydrogen in the CsGd2F7 crystal, the crystal in Example 3 was a fluoride crystal containing hydrogen in the CsSm2F7 crystal, and the crystal in Example 4 was a fluoride crystal containing hydrogen in the CsLu2F7 crystal.

[0104] <Optical properties> A powder sample was prepared by grinding the crystal from Example 1, and the emission spectrum and excitation spectrum were measured using a fluorescence spectrophotometer.

[0105] Figure 13 shows the excitation spectrum and emission spectrum of the crystal in Example 1.

[0106] According to Figure 13, the crystal in Example 1 can be excited most efficiently at 227 nm, and the emission spectrum when excited at 227 nm is Tb 3+ It was found that it emits green light with a peak at 545 nm based on the given data. This suggests that the crystal in Example 1 can function as a phosphor, and that the fluoride crystal of the present invention can function as a matrix crystal for phosphors. [Industrial applicability]

[0107] As described above, the present invention can provide fluoride crystals with controlled defects. The fluoride crystals of the present invention are industrially advantageous because they can be manufactured under milder conditions than conventional methods, and in particular, at lower temperatures. The fluoride crystals of the present invention can be applied to phosphors, scintillators, laser elements, magnetic refrigeration materials, and various optical components such as prisms, lenses, window materials, and birefringent materials. [Explanation of Symbols]

[0108] 1. Light-emitting device 2. Single-crystal phosphors 3. Ceramic substrate 4 Main unit 10 light-emitting elements 31, 32 Wiring section 40 reflective surface 300 Magnetic Refrigeration System 301 Magnetic Refrigeration Materials 320 AMR bed 330 Magnetic field application means 350 liquefaction containers 360 Pre-cooling stage 370 80K Shield 380 300K Shield 390 Cooling Stage 400 Radiation Detectors 410 Scintillator 420 Photoelectron Converter

Claims

1. It contains cesium (Cs), rare earth element RE, and fluorine element (F), and its general formula is CsRE. ２ F ７－ｘ A fluoride crystal containing at least hydrogen (H) in an inorganic crystal represented by (where x satisfies 0 ≤ x ≤ 0.5).

2. The concentration of the element hydrogen is 1 × 10⁻⁶ １４ atoms / cm ３ The above 1 x 10 ２３ atoms / cm ３ The fluoride crystal according to claim 1, wherein the crystal is within the following range.

3. The fluoride crystal according to claim 1 or 2, wherein RE is an element selected from at least one of the group consisting of scandium (Sc), yttrium (Y), cerium (Ce), praseodymium (Pr), lanthanum (La), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

4. The fluoride crystal according to claim 3, wherein RE is an element selected from the group consisting of samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

5. The inorganic crystal has a triclinic crystal structure and space group P112 １ A fluoride crystal according to claim 4, having the symmetry of / b.

6. The fluoride crystal according to any one of claims 1 to 5, wherein the inorganic crystal further contains alkali metal elements other than Cs and / or alkaline earth metal elements.

7. The concentration of the alkali metal element and / or alkaline earth metal element is 1 × 10 １２ atoms / cm ３ or more and 1 × 10 ２３ atoms / cm ３ or less, and the fluoride crystal according to claim 6.

8. The fluoride crystal according to claim 6 or 7, wherein the alkali metal element is at least one element selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and francium (Fr).

9. The fluoride crystal according to any one of claims 6 to 8, wherein the alkaline earth metal element is an element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

10. A method for producing fluoride crystals according to any one of claims 1 to 9, comprising growing crystals by solvothermal method from a raw material containing a rare earth element RE and a raw material containing a fluorine element (F) in the presence of a mineralizing agent containing at least cesium element (Cs).

11. The method according to claim 10, wherein the concentration of the mineralizing agent is in the range of 1 M or more and 50 M or less.

12. The method according to claim 10 or 11, wherein, in growing crystals by the solvothermal method, the temperature is in the range of 400°C to 800°C, and the maximum achievable pressure is in the range of 25 MPa to 250 MPa.

13. The method according to any one of claims 10 to 12, further comprising a mineralizing agent selected from the group consisting of a mineralizing agent containing an alkali metal element other than Cs, a mineralizing agent containing an alkaline earth metal element, a mineralizing agent containing a normal salt, and an acid mineralizing agent.

14. A phosphor containing fluoride crystals according to any one of claims 1 to 9.

15. A scintillator containing fluoride crystals according to any one of claims 1 to 9.

16. A laser element containing a fluoride crystal according to any one of claims 1 to 9.

17. A magnetic refrigeration material containing fluoride crystals according to any one of claims 1 to 9.

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