Oxide crystals, methods for producing the same, and their uses

Abstract

This invention provides oxide crystals and methods for producing the same that are suitable for various applications such as scintillator materials, substrate materials, battery materials, sensor materials, dental materials, structural materials, and jewelry. [Solution] The oxide crystal according to one embodiment of the present invention has the general formula (Zr 1-x Hf x ) 1-y (RE z M 1-z ) y O 2-0.5y-p (In the formula, x, y, z, and p each independently satisfy 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.6, 0 ≤ z ≤ 1, and -0.5 ≤ p ≤ 0.5, RE is selected from at least one rare earth element, and M is selected from at least one element from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mg, and Ca.) It is characterized by being represented as and containing a hydrogen atom (H).

Description

[Technical Field]

[0001] This invention relates to oxide crystals, methods for producing the same, and applications thereof. [Background technology]

[0002] Zirconia (ZrO2) is known to undergo a phase transition in its crystal structure from cubic to tetragonal to monoclinic under normal pressure, starting from the high-temperature side. It is also widely known that cubic and tetragonal zirconia can be made stable or metastable at room temperature by solid-solutioning with rare earth oxides such as calcium oxide, magnesium oxide, or yttrium oxide. Zirconia with such stabilizers added is called stabilized zirconia or partially stabilized zirconia. Stabilized zirconia, especially yttria (yttrium oxide) stabilized zirconia (YSZ), has excellent ionic conductivity and becomes a solid electrolyte at high temperatures, making it used as a material for fuel cells and oxygen sensors. It is also attracting attention as a dental treatment material for crowns and bridges as an alternative to metal.

[0003] YSZ single crystals, which have a cubic crystal structure, have a Mohs hardness second only to sapphire and a high refractive index comparable to that of diamond, and have therefore been used in jewelry since ancient times. In addition, YSZ single crystals have been used as substrate crystals for a long time, and in recent years they have also been used as superconducting thin film substrates.

[0004] Because YSZ single crystals have a melting point exceeding 2700°C, crystal growth methods utilizing crucibles, such as the Czochralski (CZ) method, cannot be used. Therefore, floating zone (FZ) methods and skull melt methods are employed. Since it is difficult to grow large crystals using the FZ method, the skull melt method is mainly used for mass production.

[0005] In the skull melting method, powdered raw materials are packed into a cold crucible, and only the material in the center is melted and solidified while the material near the inner wall of the cold crucible remains unmelted. As a result, it is known that various defects remain in the grown crystal, such as growth fringes caused by light scattering and the non-uniform distribution of stabilizers, and residual stresses and dislocations caused by the steep temperature gradient in the crystal growth field. Since YSZ single crystals are expected to have many applications, including the substrates and jewelry mentioned above, there is a growing demand for single crystals with reduced defects and methods for growing them.

[0006] Similar to zirconia mentioned above, hafnia (HfO2) is also known to undergo a phase transition in its crystal structure from cubic to tetragonal to monoclinic under normal pressure, starting from the high-temperature side. Hafnia has traditionally been used in the semiconductor process field as a gate portion of semiconductor devices, for example, as a gate insulating film for CMOS (Complementary Metal-Oxide-Semiconductor). Furthermore, since it was reported that hafnia possesses ferroelectric properties, interest in its applications has increased, and research is being conducted on HfO2-ZrO2 solid solution thin films, for example.

[0007] On the other hand, most of the applications of hafnia reported so far have been in thin film materials, and there are very few reports on the growth of bulk single crystals. Therefore, if a method for growing bulk single crystals of hafnia is established, it is expected that it will have many more applications, including substrates and jewelry, similar to zirconia.

[0008] Hydrothermal synthesis is a method that allows for the growth of high-quality single crystals at relatively low temperatures and is also suitable for large-scale mass production. Therefore, attempts have been made to grow crystals using hydrothermal synthesis. For example, Non-Patent Literature 1 describes the growth of monoclinic zirconia crystals (see pages 295-302). According to Non-Patent Literature 1, it is difficult to grow zirconia single crystals using OH-based mineralizers such as KOH in hydrothermal synthesis. However, it is reported that monoclinic zirconia single crystals were obtained at a high temperature of 750°C using expensive and inconvenient mineralizers such as CsF and NH4F. Here, it is stated that the product was in powder form at 650°C, but by using the high temperature of 750°C, a single crystal of about 0.5 mm was obtained. In other words, Non-Patent Literature 1 suggests that increasing the temperature is the key point for increasing the size of the crystals. However, anyone skilled in the art who has read Non-Patent Document 1 would understand that a temperature of 750°C in the hydrothermal synthesis method, considering the configuration of the apparatus used for crystal growth, indicates that it is extremely difficult to grow large crystals. Furthermore, Non-Patent Document 1 reports that while monoclinic zirconia has been obtained, cubic zirconia has not yet been obtained (see page 305).

[0009] In addition, Non-Patent Document 1 describes the acquisition of cubic hafnia single crystals stabilized with Y, Nd, Ho, and Er (see page 308). However, the growth conditions were 750°C and 20M KOH, and as mentioned above, a person skilled in the art who has read Non-Patent Document 1 would understand that a temperature of 750°C in the hydrothermal synthesis method, considering the configuration of the apparatus used for crystal growth, indicates that it is extremely difficult to grow large crystals. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] James Mann, Hydrothermal Crystal Growth of Tetravalent and Pentavalent Metal Oxides, 2009, All Dissertations, 394.

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of such circumstances, and an object thereof is to provide an oxide crystal suitable for application to the above-described various uses and the like. Another object of the present invention is to provide a method for producing the above-described oxide crystal. Another object of the present invention is to provide uses of the above-described oxide crystal.

Means for Solving the Problems

[0012] The oxide crystal according to the present invention has a general formula (Zr 1-x Hf x ) 1-y (RE z M 1-z ) y O 2-0.5y-p (wherein x, y, z, and p each independently satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 1, -0.5 ≦ p ≦ 0.5, RE is at least one selected from rare earth elements, and M is at least one selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), magnesium (Mg), and calcium (Ca)). It is represented by and contains hydrogen atoms (H), thereby solving the above problems. In the oxide crystal of the present invention, the concentration of hydrogen atoms may be in the range of 1 × 10 16 atoms / cm 3 or more and 1 × 10 23 atoms / cm 3 or less. The oxide crystal of the present invention may have a crystal structure belonging to the P121 / c1 space group and the crystal phase may be a monoclinic single phase, or it may have a crystal structure belonging to the Fm-3m space group and the crystal phase may be a cubic single phase. The above rare earth elements may also be scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The oxide crystals of the present invention may further contain alkali metals and / or alkaline earth metals other than M mentioned above. The concentrations of the alkali metals and / or alkaline earth metals other than M are 1 × 10 12 atoms / cm 3 The above 1 x 10 20 atoms / cm 3 The following range is also acceptable. The oxide crystal of the present invention may further contain at least one element selected from the group consisting of aluminum (Al), gallium (Ga), and germanium (Ge). *Based on your preference regarding the RE2O3 system, the order of the descriptions for Al, Ga, and Ge has been moved to the end. As you may already know, a common point for the ZrO2-HfO2 system, BaHfO3 system, and RE2O3 system is that if traces are found in SIMS or similar in the future, this provision may be incorporated into higher-level claims to differentiate it from prior applications.

[0013] The method for producing the above-mentioned oxide crystals according to the present invention includes growing crystals by hydrothermal synthesis using raw materials containing each element included in the crystal, in the presence of a first mineralizing agent which is an alkali metal and / or an alkaline earth metal other than M mentioned above, or an acid mineralizing agent, or a mixture of both, and a second mineralizing agent which is at least one selected from the group consisting of aluminum oxide, gallium oxide, and germanium dioxide. This solves the above-mentioned problem. The concentration of the first mineralizing agent described above may be in the range of 1 M to 50 M. The concentration of the second mineralizing agent mentioned above may be in the range of 0.01 M to 20 M. In growing crystals using the hydrothermal synthesis method described above, the temperature may be in the range of 400°C to less than 750°C, and the maximum achievable pressure may be in the range of 25 MPa to 250 MPa.

[0014] The material or article according to the present invention includes the above-mentioned oxide crystals, thereby solving the above-mentioned problems. The above materials or articles may be substrate materials, battery materials, sensor materials, dental materials, structural materials, or jewelry. The scintillator material according to the present invention consists of the above-mentioned oxide crystal, thereby solving the above-mentioned problems. The radiation detector according to the present invention comprises the above-mentioned scintillator material and a photoelectric converter that detects light from the scintillator material and converts it into an electrical signal, thereby solving the above-mentioned problems. The radiation inspection apparatus according to the present invention comprises a radiation source that irradiates a subject with radiation and the above-mentioned radiation detector that detects radiation that penetrates the subject, thereby solving the above-mentioned problems. [Effects of the Invention]

[0015] The present invention provides oxide crystals suitable for application to the various uses described above. In one exemplary embodiment, an oxide crystal is provided that does not contain harmful substances such as cadmium and has scintillation properties comparable to or better than cadmium tungstate (CdWO4), a scintillator material used in conventional X-ray detectors. The oxide crystal of this embodiment is suitable for use as a scintillator material. The scintillator material of the present invention is suitable for use as a scintillator material for radiation detectors, and in particular for use as a scintillator material for X-ray radiation detectors. Furthermore, a radiation detector equipped with the scintillator material of the present invention can be suitably used in radiation inspection devices. Alternatively, in another exemplary embodiment, the oxide crystal of the present invention is suitable for use in various materials and articles such as substrate materials, battery materials, sensor materials, dental materials, structural materials, and jewelry.

[0016] Since the oxide crystals of the present invention are produced by hydrothermal synthesis, they can be grown under significantly lower temperature conditions and gentler temperature gradients compared to conventional methods. In addition, bulk single crystals can be grown under conditions of high oxygen partial pressure (an atmosphere containing a large amount of oxygen). As a result, the resulting crystals have suppressed oxygen defects and are defect-controlled crystals. Furthermore, in the present invention, there is no need to use iridium (Ir) or rhodium (Rh) components such as crucibles and dies used in conventional methods, thus reducing the production cost of the target crystal. Moreover, by using hydrothermal synthesis, it is relatively easy to increase the size and mass-produce crystals compared to conventional methods. In addition, since no harmful substances such as cadmium are used, it is an environmentally friendly material, and the manufacturing process is also environmentally friendly. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram showing the configuration of a radiation detector relating to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the configuration of a radiation inspection device relating to one embodiment of the present invention. [Figure 3-1] This figure shows a microscopic image of the crystal obtained in Example 1 in the example. [Figure 3-2] This figure shows a microscopic image of the crystal obtained in Example 2 in the example. [Figure 3-3] This figure shows a microscopic image of the crystal obtained in Example 3 in the examples. [Figure 3-4] This figure shows a microscopic image of the crystal obtained in Example 4 in the examples. [Figure 3-5] This figure shows a microscopic image of the crystal obtained in Example 5 in the examples. [Figure 3-6] This figure shows a microscopic image of the crystal of Example 6 obtained in the examples. [Figure 3-7] This figure shows a microscopic image of the crystal obtained in Example 7 in the examples. [Figure 3-8] This figure shows a microscopic image of the crystal of Example 8 obtained in the example. [Figure 4-1] This figure shows the results of powder X-ray diffraction measurements of the crystal in Example 1, and the simulation results of the diffraction chart of ZrO2 (monoclinic P121 / c1). [Figure 4-2] This figure shows the results of powder X-ray diffraction measurements of the crystal in Example 2, and the simulation results of the diffraction chart for YSZ (cubic system F m -3 m, and monoclinic system P 1 21 / c 1). [Figure 4-3] This figure shows the results of powder X-ray diffraction measurements of the crystal and raw materials in Example 3, as well as the simulation results of the diffraction chart of HfO2 (monoclinic P121 / c1). [Figure 4-4] This figure shows the results of powder X-ray diffraction measurements of the crystal in Example 4, and the simulation results of diffraction charts for HfO2 (monoclinic P121 / c1) and YSH (cubic Fm-3m). [Figure 5] This figure shows the results of secondary ion mass spectrometry of the crystal in Example 1, specifically the concentrations of hydrogen and potassium. [Figure 6] This figure shows the PL spectrum and excitation spectrum of sample 3. [Figure 7] This figure shows the XRL spectrum of sample 3. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present invention will be described.

[0019] [Oxide crystal] [Composition] The oxide crystal of the present invention has the general formula (Zr 1-x [[ID=1V]]Hf x )) 1-y (RE z M 1-z )) y O 2-0.5y-p (where x, y, z, and p each independently satisfy 0 ≦ x ≦ 1, 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 1, -0.5 ≦ p ≦ 0.5, RE is at least one selected from rare earth elements, and M is at least one selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), magnesium (Mg), and calcium (Ca)).) and contains a hydrogen atom (H). Hereinafter, unless otherwise specified, the description of "hydrogen" means a hydrogen atom.

[0020] In one aspect, x in the above general formula is zero. In this case, the oxide crystal has the composition represented by Zr 1-y (RE z M 1-z )) y O 2-0.5y-p (however, 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 1, -0.5 ≦ p ≦ 0.5). Here, when y is zero, the oxide crystal has the composition represented by ZrO 2-p (however, -z.5 ≦ p ≦ 0.5) and can be referred to as zirconia. On the other hand, when y satisfies the condition 0 < y ≦ 0.6, and z is 1 and RE is yttrium (Y), the oxide crystal can be referred to as yttria-stabilized zirconia (YSZ).

[0021] In another aspect, x in the above general formula is 1. In this case, the oxide crystal has the composition represented by Hf 1-y (RE z M 1-z ))y O 2-0.5y-p (where 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 1, -0.5 ≦ p ≦ 0.5). Here, when y is zero, the oxide crystal is HfO 2-p (where -0.5 ≦ p ≦ 0.5), and can be referred to as hafnia. On the other hand, when y satisfies the condition 0 < y ≦ 0.6, and z is 1, and RE is yttrium (Y), the oxide crystal can be referred to as yttria-stabilized hafnia (YSH).

[0022] In yet another aspect, x in the above general formula satisfies the condition 0 < x < 1. In this case, the oxide crystal is (Zr 1-x Hf x ) 1-y (RE z M 1-z ) y O 2-0.5y-p (where 0 ≦ y ≦ 0.6, 0 ≦ z ≦ 1, -0.5 ≦ p ≦ 0.5). Here, when y is zero, the oxide crystal is (Zr 1-x Hf x )O 2-p (where -0.5 ≦ p ≦ 0.5).

[0023] Y in the above general formula may satisfy the condition 0 < y ≦ 0.6. Thereby, it is expected that the stability of the cubic crystal of the oxide crystal of the present invention is improved. In this context, z in the above general formula is preferably 0 < z ≦ 1, more preferably 0.25 ≦ z ≦ 1, still more preferably 0.5 ≦ z ≦ 1, particularly preferably 0.75 ≦ z ≦ 1, and most preferably 0.8 ≦ z ≦ 1. Also, y preferably satisfies 0.1 ≦ y ≦ 0.6, more preferably 0.15 ≦ y ≦ 0.6, and still more preferably 0.2 ≦ y ≦ 0.6. Thereby, it is expected that the effect of improving the stability of the cubic crystal by RE (such as Y, etc.) can be more surely obtained.

[0024] In the above general formula, RE is selected from at least one rare earth element. Preferably, the rare earth element is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). RE may be a single element or a combination of two or more elements. In one exemplary embodiment, RE preferably contains Y.

[0025] In the above general formula, M is selected from at least one metal element other than RE (hereinafter also simply referred to as "metal element"). Preferably, the metal element is selected from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), magnesium (Mg), and calcium (Ca). The metal element may be a single element or a combination of two or more elements. In one exemplary embodiment, it is preferable that the metal element contributes to the oxide crystal exhibiting an arbitrary color and / or to further stabilization of the cubic crystal.

[0026] It should be noted that the above general formula represents the stoichiometric composition of the oxide crystals of the present invention. As will be described later, the oxide crystals of the present invention are grown by hydrothermal synthesis, and the resulting crystals are obtained with the most stable composition. Therefore, even if there is a deviation from the target composition, the difference is within a controllable range.

[0027] Furthermore, although the oxide crystal of the present invention may have a number of oxygen atoms that is smaller or larger than the stoichiometric composition due to defects in the crystal, the decrease in the transmittance of the crystal is sufficiently suppressed by satisfying the condition for p in the above general formula -0.5 ≤ p ≤ 0.5.

[0028] In one embodiment, the concentration of hydrogen contained in the oxide crystal of the present invention is 1 × 10⁻⁶ 16 atoms / cm 3 The above 1 x 10 23 atoms / cm 3 The range is as follows, preferably 1 × 10 17 atoms / cm 3 The above 1 x 10 22 atoms / cm 3 The range is as follows, more preferably 1 × 10 18 atoms / cm 3 The above 1 x 10 22 atoms / cm 3 The range is as follows:

[0029] The method for measuring the hydrogen concentration in the oxide crystal of the present invention is not particularly limited and can be confirmed by conventional methods, for example, secondary ion mass spectrometry (SIMS) can be used. The same applies to the concentrations of elements other than hydrogen (for example, the concentrations of arbitrary constituent elements described later (alkali metals and / or alkaline earth metals, or Al, Ga and / or Ge)). Here, when using SIMS, the hydrogen concentration is taken as the value at a depth of 3 μm, and the concentrations of alkali metals and alkaline earth metals are taken as the value at a depth of 6 μm. An example of SIMS measurement will be described in the Examples section.

[0030] <Optional constituent elements> The oxide crystals of the present invention may further contain any constituent elements other than Zr, Hf, RE, M(Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mg and / or Ca), O, and H as described above.

[0031] In one embodiment, the oxide crystal of the present invention further contains alkali metals and / or alkaline earth metals other than M as optional constituent elements. Hereinafter, when referring to alkaline earth metals as optional constituent elements, it is assumed that alkaline earth metals other than M are intended unless otherwise specified. In one exemplary embodiment, the alkali metal is selected from the group consisting of lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), and is preferably selected from the group consisting of K, Rb, and Cs. The alkaline earth metal is selected from the group consisting of beryllium (Be), strontium (Sr), barium (Ba), and radium (Ra), and is preferably selected from the group consisting of Sr and Ba. The alkali metal and alkaline earth metal may be present individually or in combination of two or more. It is expected that the inclusion of alkali metals and / or alkaline earth metals in the oxide crystal will deactivate defects within the crystal.

[0032] In an embodiment of the present invention in which the oxide crystal contains alkali metals and / or alkaline earth metals, the concentration of the alkali metals and / or alkaline earth metals is 1 × 10⁻⁶ 12 atoms / cm 3 The above 1 x 10 20 atoms / cm 3 The range is as follows, preferably 1 × 10 13 atoms / cm 3 The above 1 x 10 19 atoms / cm 3 The range is as follows, more preferably 1 × 10 14 atoms / cm 3 The above 1 x 10 18 atoms / cm 3 The range is as follows:

[0033] In one embodiment, the oxide crystal of the present invention further contains, as an optional constituent element, at least one element selected from the group consisting of aluminum (Al), gallium (Ga), and germanium (Ge). It is expected that the presence of these elements in the oxide crystal will deactivate defects within the crystal.

[0034] <Crystal structure> In one embodiment, the oxide crystal of the present invention belongs to the monoclinic crystal system and is P121 / c1 (space group 14 of the International Tables for Crystallography (also simply called the International Table(s))). In another embodiment, the oxide crystal of the present invention belongs to the cubic crystal system and is Fm-3m (space group 225 of the same). Tables 1 to 4 below show representative examples such as ZrO2 (P121 / c1) and YSZ (Zr 0.65 Y 0.35 O 1.825 )(F m -3 m), HfO2(P 1 21 / c 1), YSH(Hf 0.6 Y 0.4 O 1.8 The crystal parameters and atomic coordinate positions of (F m -3 m) are shown. Furthermore, it is preferable that the oxide crystal of the present invention has a single phase as identified by powder X-ray diffraction measurement.

[0035] The method for measuring the space group is not particularly limited, but for example, if the composition (design composition or result of compositional analysis) and structure of the target crystal are specified (or estimated or assumed), the space group can be estimated by obtaining a powder X-ray diffraction chart (also referred to as a simulation result in this specification) of a crystal having that composition and structure (or something similar) using information obtained from generally available databases, and comparing the simulation result with the powder X-ray diffraction measurement result of the target crystal. Specific examples of this method will be described in the Examples section.

[0036] [Table 1]

[0037] [Table 2]

[0038] [Table 3]

[0039] [Table 4]

[0040] In the embodiment of the present invention where y in the above general formula is zero, the lattice constant of the oxide crystal changes as its constituent elements are replaced by other elements. 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 skeletal atoms are broken, and the structure belonging to the P1 21 / c1 space group is maintained.

[0041] <Main Features> The oxide crystal of the present invention can have transparency comparable to that of conventional CdWO4. When the oxide crystal of the present invention is used as a scintillator material, light generated within the scintillator crystal can be efficiently transmitted, thus preventing a decrease in the amount of light emitted.

[0042] The oxide crystal of the present invention has a density and ρ·(Z) comparable to that of CdWO4. eff ) 4 It may have the above ρ·(Z eff ) 4 The value of is 0.8 or greater as a ratio to the value in CdWO4. Here, the value of the ratio is preferably 0.85 or greater, more preferably 0.9 or greater, even more preferably 0.95 or greater, even more preferably 1 or greater, and most preferably greater than 1.

[0043] Indicators representing the scintillation characteristics of the oxide crystal of the present invention include, for example, the amount of light emitted, the decay time (decay characteristics), and the afterglow (afterglow characteristics). In one preferred embodiment, the oxide crystal of the present invention may exhibit an amount of light emitted comparable to or exceeding that of conventional CdWO4. In another preferred embodiment, the oxide crystal of the present invention may exhibit a practically acceptable scintillation decay time. In yet another preferred embodiment, the oxide crystal of the present invention may exhibit an afterglow comparable to that of CdWO4.

[0044] In the context described above, it should be noted that the oxide crystal of the present invention does not necessarily require all properties to surpass those of CdWO4. That is, depending on the various applications as a scintillator material, as exemplified below, the oxide crystal of the present invention can be considered a practically useful scintillator material if it satisfies the scintillation properties required for that application. In other words, the oxide crystal of the present invention can be said to be environmentally friendly, both as a scintillator material itself and in its manufacturing method, because it does not contain harmful substances such as cadmium. Even if it has properties that are slightly inferior to (not comparable to) those of CdWO4, it can still serve as a scintillator material that can replace CdWO4.

[0045] Furthermore, in one embodiment, the oxide crystal of the present invention may exhibit properties suitable for each application, such as a substrate material, battery material, sensor material, dental material, structural material, or jewelry.

[0046] [Method for manufacturing oxide crystals] Next, the method for producing the oxide crystals described above will be explained.

[0047] A method for producing oxide crystals according to one embodiment of the present invention includes growing crystals from raw materials containing each element to be included in the crystal by hydrothermal synthesis in the presence of a first mineralizing agent which is an alkali metal and / or an alkaline earth metal other than M mentioned above, or an acid mineralizing agent, or a mixture of both, and a second mineralizing agent which is at least one selected from the group consisting of aluminum oxide, gallium oxide, and germanium dioxide. Here, the term "hydrothermal synthesis" in this specification refers to an embodiment in which water is used as the solvent in the "solvothermal method". An example of the production method is described below.

[0048] <Step S110: Step to prepare raw materials> In step S110, the raw materials necessary to obtain a compound that satisfies the composition of the target crystal are prepared.

[0049] Specifically, raw materials containing zirconium (Zr) and / or hafnium (Hf), and optionally raw materials containing RE (RE is selected from at least one rare earth element) and / or M (M is selected from at least one metallic element other than RE, preferably at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mg, and Ca), are prepared, and one or more compounds from these are used as oxides. For convenience, in this specification, the raw materials containing each constituent element prepared in step S110 will also be referred to as raw materials for each constituent element. For example, "raw material containing Zr" and "raw material for Zr" are synonymous.

[0050] The raw materials can include elemental elements, oxides, hydroxides, halides, inorganic salts (sulfates, nitrates, carbonates, etc.), and organic salts (acetates, etc.). Compounds other than elemental elements may be anhydrous or hydrated. The following are non-limiting examples of raw materials that can be used in the manufacturing method of this embodiment.

[0051] For example, ZrO2 can be used as a raw material for Zr. As a raw material for Hf, for example, HfO2 can be used. As a raw material for RE, for example, a simple substance of RE, an oxide of RE (such as RE2O3, etc.) can be used. As a raw material for M, for example, an oxide or carbonate of M (such as MO, MO2, MCO3, etc.) can be used. Exemplarily, CoO, NiO, TiO2, FeO, Fe2O3, CaCO3, etc. can be mentioned.

[0052] In one embodiment, the raw materials for Zr and Hf are prepared so as to satisfy the condition of x in the above general formula in terms of the atomic ratio. For example, when the composition of the target oxide crystal is Zr 1-x Hf x O2, and when x satisfies the condition 0 < x < 1, it may be prepared so as to satisfy Zr:Hf = 1 - x:x. When x is zero or 1, only the raw material for Zr or Hf may be prepared. Further, when the composition of the target oxide crystal contains RE and / or M (that is, when y in the above general formula satisfies the condition 0 < y ≤ 0.6), the raw materials for RE and M are prepared according to the value of y and the value of z. Here, if necessary, a raw material mixture containing each raw material may be prepared.

[0053] <Step S120: A step of crystal growth of the raw material by a hydrothermal synthesis method in the presence of a first mineralizer and a second mineralizer> In step S120, the raw material prepared in step S110 (or the raw material mixture prepared by mixing each raw material) is subjected to crystal growth by a hydrothermal synthesis method in the presence of a first mineralizer and a second mineralizer.

[0054] As the first mineralizing agent, a mineralizing agent containing an alkali metal and / or an alkaline earth metal other than M, an acid mineralizing agent, or a mixed mineralizing agent of both can be used. Hereafter, when alkaline earth metals are referred to in the context of the first mineralizing agent, it is assumed that alkaline earth metals other than M are intended unless otherwise specified. The mineralizing agent containing an alkali metal and / or an alkaline earth metal is a compound containing an alkali metal and / or an alkaline earth metal, and for example, hydroxides or inorganic salts (carbonates, etc.) of alkali metals and / or alkaline earth metals can be used. Non-limiting examples of the first mineralizing agent include, for example, KOH, K2CO3, RbOH, Rb2CO3, CsOH, Cs2CO3, Sr(OH)2, SrCO3, Ba(OH)2, BaCO3, etc., and it is preferable to select at least one from the group consisting of these compounds. Examples of acid mineralizers include, but are not limited to, hydrochloric acid, nitric acid, sulfuric acid, formic acid, and phosphoric acid. Furthermore, alkali metals and / or alkaline earth metals contained in the first mineralizing agent, or elements contained in the acid mineralizing agent, may be present in the final oxide crystal.

[0055] The second mineralizing agent is selected from the group consisting of aluminum oxide (Al2O3), gallium oxide (Ga2O3), and germanium dioxide (GeO2), with at least one selected from this group. In one preferred embodiment, the second mineralizing agent includes aluminum oxide, and in a more preferred embodiment, the second mineralizing agent is aluminum oxide. By using the first and second mineralizing agents described above, it becomes possible to grow crystals at significantly lower temperatures compared to conventional methods other than hydrothermal synthesis, and even at lower temperatures than the conventional hydrothermal synthesis method described in Non-Patent Document 1. Furthermore, by using the first and second mineralizing agents, it becomes possible to grow larger crystals. Furthermore, the elements contained in the second mineralizing agent may be present in the final oxide crystal.

[0056] The method for preparing the solution (reaction solution) used for crystal growth by hydrothermal synthesis is not particularly limited. For example, if a raw material mixture is prepared in step S110 described above, a solution of the first mineralizer and a solution of the second mineralizer, adjusted to any concentration, may be added to the raw material mixture and further mixed as necessary. Alternatively, the first mineralizer and the second mineralizer (preferably in powder or tablet form) may be added to the raw material mixture and further mixed as necessary. Alternatively, the above-mentioned raw materials may be added to an aqueous solution obtained by mixing a solution of the first mineralizer and a solution of the second mineralizer, adjusted to any concentration, and mixed as appropriate.

[0057] Here, the concentration of the first mineralizer in the final solution is preferably in the range of 1 M to 50 M, more preferably in the range of 3 M to 45 M, even more preferably in the range of 5 M to 40 M, and particularly preferably in the range of 7 M to 30 M. Within the above concentration range, the upper limit may be less than 30 M. In an exemplary embodiment, the concentration of the first mineralizer may be in the range of 1 M to less than 30 M, in the range of 1 M to 25 M, in the range of 1 M to 20 M, in the range of 3 M to 20 M, in the range of 5 M to 20 M, or in the range of 7 M to 20 M.

[0058] Here, the crystal growth conditions (specifically, temperature conditions) by hydrothermal synthesis can be adjusted by the type of alkali metal and / or alkaline earth metal contained in the first mineralizing agent used, and the concentration of the first mineralizing agent. Although certain care is required when handling highly alkaline solutions, the desired solution can be prepared by appropriately adjusting the concentration of the first mineralizing agent. It is also preferable to select the type of first mineralizing agent depending on the raw materials used and / or the type of constituent elements of the target crystal.

[0059] Furthermore, the concentration of the second mineralizer in the final prepared solution is preferably in the range of 0.01 M to 20 M, more preferably in the range of 0.02 M to 15 M, even more preferably in the range of 0.03 M to 12 M, even more preferably in the range of 0.05 M to 10 M, and particularly preferably in the range of 0.1 M to 7 M. By having the concentration of the second mineralizer within the above range, the growth temperature of the target crystal is lowered, making it possible to grow larger crystals. On the other hand, if the concentration of the second mineralizer is less than 0.01 M, the above effects may not be sufficiently obtained, and if the concentration of the second mineralizer exceeds 20 M, the contamination of elements derived from the second mineralizer may exceed the acceptable range, making it difficult to apply the solution to the intended use of growing crystals.

[0060] The crystal growth conditions for hydrothermal synthesis are not particularly limited and can be set according to the size of the hydrothermal synthesis vessel (reaction vessel) used. In one exemplary embodiment, the temperature is preferably in the range of 400°C to less than 750°C. This ensures that the desired crystals can be reliably obtained. If the temperature is below 400°C, the desired crystals may not be formed, if the temperature is above 750°C, it becomes difficult to increase the size of the crystals, and if the temperature exceeds 800°C, it may exceed the heat resistance temperature of the reaction vessel. The pressure is preferably in the range of 25 MPa to 250 MPa. In this context, the pressure is intended to be such that the maximum pressure achieved during crystal growth is within the above range. This pressure condition varies depending on the amount of water contained in the reaction vessel, the size of the ampoule (sealed container) containing the reaction solution, the temperature conditions, etc. In an exemplary embodiment, the maximum pressure achieved may be in the range of 30 MPa to 250 MPa, 50 MPa to 225 MPa, or 75 MPa to 200 MPa.

[0061] The time required for hydrothermal synthesis can be adjusted as appropriate to ensure the crystal growth is completed, depending on the type and amount of raw materials used. Here, two or more temperature conditions may be set within the aforementioned temperature range to establish a predetermined temperature profile. Such a temperature profile can be designed considering factors such as improving the homogeneity and stability of the solution, and more efficiently generating the desired crystals. An example of a specific temperature profile is shown in the embodiments described later.

[0062] In the manufacturing method according to this embodiment, crystals are grown by hydrothermal synthesis at significantly lower temperature conditions compared to conventional methods. In the above-mentioned FZ method, it is difficult to increase the size of the crystals. In contrast, while it is possible to increase the size of the crystals in the skull melt method, due to the principle of crystal growth, residual stresses and dislocations caused by the steep temperature gradient in the crystal growth field may occur, raising concerns that various defects may remain in the grown crystal. The manufacturing method of the present invention makes it possible to increase the size of the crystals and suppresses the various defects mentioned above. Furthermore, in other melt growth methods, including the FZ method, the phenomenon of evaporation of certain components during the crystal growth process is likely to occur due to the melting point of the target crystal, and such decomposition and evaporation phenomena may also occur in the grown crystal, potentially causing defects in the grown crystal. However, in the manufacturing method of the present invention, such decomposition and evaporation phenomena are less likely to occur, thus suppressing defects that may occur in the grown crystal. Furthermore, in the case of hydrothermal synthesis, the resulting crystals are obtained with the most stable composition. While this composition may deviate slightly from the target composition, any such deviation can be adjusted.

[0063] [Uses of oxide crystals] The oxide crystals of the present invention, which can be manufactured as described above, are not particularly limited in their applications, but in one exemplary embodiment, they are suitable for use as scintillator materials. In particular, because the oxide crystals of the present invention have very few defects, scintillator materials made from these oxide crystals may have properties such as density, fluorescence decay time, and fluorescence output comparable to existing materials, and may even exhibit scintillation properties comparable to or exceeding those of CdWO4.

[0064] [Applications of scintillator materials] The use of the above-mentioned scintillator material, which is in crystalline form, is not particularly limited, but it is preferably used in radiation detectors. The configuration of the radiation detector is not particularly limited, and a configuration similar to that of conventional radiation detectors can be adopted. Specifically, as schematically shown in Figure 1, a radiation detector 10 according to one embodiment of the present invention comprises a scintillator material (scintillator) 11 made of the above-mentioned oxide crystal, and a photoelectric converter 12 (for example, a photomultiplier tube (PMT), silicon photomultiplier (SiPM), solid-state image sensor (CCD), avalanche photodiode (APD), multipixel photon counter (MPPC), etc.) that detects light L emitted from the scintillator material 11 and converts it into an electrical signal. By using the above-mentioned scintillator material made of oxide crystal instead of the scintillator used in conventional radiation detectors, an improvement in the accuracy of radiation detection can be expected.

[0065] Furthermore, it is possible to construct a radiation inspection device by using the above-mentioned radiation detector and combining it with a radiation source that irradiates a subject with radiation. For example, as schematically shown in Figure 2, a radiation inspection device 20 according to one embodiment of the present invention comprises a radiation detector 10 (see Figure 1) and a radiation source 23, wherein the radiation source 23 irradiates the subject Sbj with radiation R, and the radiation detector 10 is configured to detect radiation E that penetrates the subject Sbj. In this case, the radiation detector 10 emits light L when excited by radiation E, and the photoelectric converter 12 detects the light L emitted from the scintillator material 11 and converts it into an electrical signal. Such a radiation inspection device 20 can be used, for example, as an inspection device for non-destructive testing such as a non-destructive testing detector, a resource exploration detector, or a high-energy physics detector, or as a medical diagnostic device such as a medical image processing device (X-ray CT, etc.).

[0066] Alternatively, the aforementioned radiation detectors may also be applied to the detection of radiation (such as gamma rays) emitted from a subject. Specifically, examples include medical image processing equipment such as SPECT (Single Photon Emission Computed Tomography) devices, exploration equipment for underground resource exploration, hazardous material detection equipment, and equipment used in research and development fields related to space, such as cosmic ray and astrophysics.

[0067] In addition, in another exemplary embodiment, the oxide crystals of the present invention are suitable for use in various materials and articles, such as substrate materials, battery materials, sensor materials, dental materials, structural materials, and jewelry.

[0068] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. [Examples]

[0069] [Crystal Manufacturing] <Example 1: ZrO2> Commercially available ZrO2 (powder, manufactured by Furuuchi Chemical Co., Ltd.) was prepared as the raw material for Zr. The ZrO2, KOH (a tablet equivalent to a 20M aqueous solution) as the first mineralizing agent, Al2O3 (a powder equivalent to a 0.2M aqueous solution) as the second mineralizing agent, and pure water (0.7 mL) were placed in a silver ampoule (5 mm in diameter x 10 cm in length) and sealed. This sealed ampoule was then placed in a reaction vessel containing pure water, and hydrothermal synthesis was carried out. The conditions for hydrothermal synthesis were to raise the temperature to 700°C over 12 hours, hold it for 24 hours, and then cool it down to 600°C over 100 hours to complete crystal growth. The maximum pressure reached during this process was 155 MPa. The cooling program from 600°C to room temperature at the end of crystal growth was set to 1 hour, after which natural cooling was allowed. This yielded the crystals of Example 1.

[0070] <Example 2: YSZ> As raw materials for Zr and Y (raw materials for RE), ZrO2 and Y2O3 (in powder form, manufactured by Furuuchi Chemical Co., Ltd.) were prepared, and each raw material was mixed to obtain a powdered raw material mixture. The obtained raw material mixture, KOH as the first mineralizing agent (in the form of a tablet equivalent to a 20M aqueous solution), Al2O3 as the second mineralizing agent (in the form of powder equivalent to a 0.2M aqueous solution), and pure water (0.65 mL) were placed in a silver ampoule (5 mm in diameter x 10 cm in length) and sealed. This sealed ampoule was then placed in a reaction vessel containing pure water, and hydrothermal synthesis was carried out. The conditions for hydrothermal synthesis were a temperature profile in which the temperature was raised to 700°C over 12 hours and held for 60 hours to complete crystal growth. The maximum pressure reached during this process was 157 MPa. After crystal growth, natural cooling was performed. This yielded the crystal of Example 2.

[0071] <Example 3: HfO2> Commercially available HfO2 (powdered, manufactured by Furuuchi Chemical Co., Ltd.) was prepared as the raw material for Hf. The HfO2, KOH (a tablet equivalent to a 20M aqueous solution) as the first mineralizing agent, Al2O3 (a powder equivalent to a 0.2M aqueous solution) as the second mineralizing agent, and pure water (0.65 mL) were placed in a silver ampoule (5 mm in diameter x 10 cm in length) and sealed. This sealed ampoule was then placed in a reaction vessel containing pure water, and hydrothermal synthesis was carried out. The conditions for hydrothermal synthesis were a temperature profile in which the temperature was raised to 700°C over 12 hours and held for 40 hours to complete crystal growth. The maximum pressure reached during this process was 155 MPa. After crystal growth, natural cooling was performed. This yielded the crystals of Example 3.

[0072] <Example 4: YSH> As raw materials for Hf and Y (raw materials for RE), HfO2 and Y2O3 (in powder form, manufactured by Furuuchi Chemical Co., Ltd.) were prepared, and each raw material was mixed to obtain a powdered raw material mixture. The subsequent procedures and crystal growth conditions were the same as in Example 3 to obtain the crystals of Example 4. The maximum pressure reached during crystal growth was 169 MPa.

[0073] <Example 5: ZrO2> Crystals for Example 5 were prepared using the same procedure as in Example 1. However, in this example, the second mineralizing agent was not used, and the amount of pure water added to the ampoule was 0.83 mL. The maximum pressure reached during crystal growth was 165 MPa.

[0074] <Example 6: YSZ> Crystals were prepared in Example 6 using the same procedure as in Example 2. However, in this example, the second mineralizing agent was not used, and the amount of pure water added to the ampoule was 0.83 mL. The crystal growth conditions were the same as in Example 5. The maximum pressure reached during crystal growth was 160 MPa.

[0075] <Example 7: HfO2> Crystals were prepared in Example 7 using the same procedure as in Example 3. However, in this example, the second mineralizing agent was not used, and the amount of pure water added to the ampoule was 0.83 mL. The crystal growth conditions were the same as in Example 5. The maximum pressure reached during crystal growth was 145 MPa.

[0076] <Example 8: YSH> Crystals were prepared in Example 8 using the same procedure as in Example 4. However, in this example, the second mineralizing agent was not used, and the amount of pure water added to the ampoule was 0.7 mL. The crystal growth conditions were the same as in Example 5. The maximum pressure reached during crystal growth was 154 MPa.

[0077] Table 5 shows the crystal manufacturing conditions for Examples 1 to 8 described above.

[0078] [Table 5]

[0079] [Measurement and Evaluation] <Microscopic observation> The crystals obtained in Examples 1 to 8 above were observed using an optical microscope. Figures 3-1 to 3-8 show microscopic images of the crystals from Examples 1 to 8, respectively. The scale bars in each image are 1 mm in Figure 3-1, 0.5 mm in Figures 3-2 to 3-4, and 200 μm (0.2 mm) in Figures 3-5 to 3-8.

[0080] According to FIGS. 3-1 to 3-4, the crystals of Examples 1 to 4 were confirmed to have a certain size in the as-grown state and to be highly transparent under microscopic observation. On the other hand, according to FIGS. 3-5 to 3-8, the crystals of Examples 5 to 8 were in the form of particles from submicron to several microns. When comparing crystals of the same common type (for example, the crystal of Example 1 and the crystal of Example 5), the difference in crystal size is clear. From this result, the effectiveness of using the above-mentioned first mineralizer and second mineralizer in combination as a mineralizer in the hydrothermal synthesis method was confirmed.

[0081] <X-ray diffraction measurement> Powder samples were prepared from the crystals of Examples 1 to 4, and powder X-ray diffraction measurements were performed. FIGS. 4-1 to 4-4 show the measurement results of the crystals of Examples 1 to 4, respectively.

[0082] The upper part of FIG. 4-1 shows the powder X-ray diffraction measurement results of the crystal of Example 1, and the lower part of FIG. 4-1 shows the simulation results of the diffraction chart of ZrO2 (monoclinic system P 1 21 / c 1). Here, by comparing the diffraction charts of both, the space group of the obtained crystal (the crystal of Example 1) can be simply estimated. It is advisable to use about 3 to 10 peaks with large peak intensities as the main peaks. The crystal parameters and atomic coordinate positions shown in Tables 1 to 4 above are important as reference in estimating or determining the space group of the oxide crystal of the present invention in that sense. In addition, the crystal structure of the oxide crystal of the present invention can define an approximate structure even using other crystal systems such as monoclinic or cubic crystals, and in that case, it will be expressed using different space groups, lattice constants, and plane indices, but the X-ray diffraction measurement results (for example, the upper part of FIG. 4-1) and the crystal structure remain unchanged, and the identification method and identification results using them are also the same thing. Therefore, in this example, powder X-ray diffraction measurements were performed as monoclinic or cubic crystals.

[0083] As shown in Figure 4-1, the diffraction chart of the crystal in Example 1 showed a high degree of agreement in peak position (angle 2θ) with the diffraction chart obtained from the above simulation. This confirmed that the obtained crystal has a monoclinic ZrO2 (P 1 21 / c 1) crystalline phase. Although there are a few peaks with low peak intensity that do not coincide with monoclinic ZrO2, these are due to some crystals of other phases that were not completely separated during the preparation of the powder sample being crushed together with the monoclinic crystals and appearing as peaks.

[0084] The upper part of Figure 4-2 shows the powder X-ray diffraction measurement results of the crystal in Example 2, and the middle and lower parts of Figure 4-2 show the results for Zr, respectively. 0.65 Y 0.35 O 1.825 The simulation results of diffraction charts for the cubic (F m -3 m) and monoclinic (P 1 21 / c 1) systems of YSZ with the above composition are shown. The above composition is based on the composition estimated by EDX measurements performed on the crystal of Example 2.

[0085] As shown in Figure 4-2, the diffraction chart of the crystal in Example 2 showed a high degree of agreement in peak position (angle 2θ) with the cubic crystal system (F m -3 m) from the diffraction chart obtained from the above simulation. This confirmed that the obtained crystal has a cubic YSZ (F m -3 m) crystal phase. Although the peak intensity is low, a few peaks matching the monoclinic crystal are also observed. These are monoclinic crystals that were not completely separated during the preparation of the powder sample and were crushed together with the cubic crystals, appearing as peaks.

[0086] The upper and middle sections of Figure 4-3 show the powder X-ray diffraction measurement results for the crystal and raw material HfO2 of Example 3, respectively, while the lower section of Figure 4-3 shows the simulation results of the diffraction chart for HfO2 (monoclinic P121 / c1).

[0087] As shown in Figure 4-3, the diffraction chart of the crystal in Example 3 showed a high degree of agreement in peak position (angle 2θ) with the diffraction chart obtained from the above simulation. This confirmed that the obtained crystal has a monoclinic HfO2 (P 1 21 / c 1) crystalline phase. Furthermore, the diffraction chart of the raw material HfO2 had broader peaks overall compared to the diffraction chart of the crystal in Example 3.

[0088] The upper panel of Figure 4-4 shows the powder X-ray diffraction measurement results of the crystal of Example 4, while the middle and lower panels of Figure 4-4 show HfO2 (monoclinic system P121 / c1) and Hf, respectively. 0.6 Y 0.4 O 1.8 The simulation results of the diffraction chart of YSH(F m -3 m) with the composition shown are presented. Note that the above composition is based on the composition estimated by performing EDX measurements on the crystal of Example 4.

[0089] As shown in Figure 4-4, the diffraction chart of the crystal in Example 4 showed a high degree of agreement in peak position (angle 2θ) with the diffraction chart obtained from the YSH simulation described above. This confirmed that the obtained crystal has a cubic YSH (F m - 3 m) crystalline phase. Although peaks matching the monoclinic phase are also observed, these are monoclinic crystals that were not completely separated during the preparation of the powder sample and were crushed together with the cubic crystals, resulting in the appearance of peaks.

[0090] <Secondary Ion Mass Spectrometry> For the crystal in Example 1, the hydrogen and potassium concentrations were measured using a secondary ion mass spectrometer (Cameca IMS-6F) and a time-of-flight secondary ion mass spectrometer (TOF-SIMS, IonTOF), respectively. The results are shown in Figure 5. The horizontal axis in Figure 5 represents the measurement depth (μm).

[0091] According to FIG. 5, in the obtained crystal, the hydrogen concentration is about 8×10 20 atoms / cm 3 at a depth of 3 μm, and satisfies 1×10 21 atoms / cm 3 or less. The potassium concentration is about 2×10 16 atom / cm 3 at a depth of 6 μm, and satisfies 1×10 19 atoms / cm 3 or less. It was also confirmed that zirconium and oxygen have a concentration ratio that almost matches the theoretical composition. Although not shown, as a result of performing component analysis on the crystals of Examples 2 to 4 in the same manner, the hydrogen concentration was 1×10 16 atoms / cm 3 or more and 1×10 23 atoms / cm 3 or less, and the potassium concentration was 1×10 12 atoms / cm 3 or more and 1×10 20 atoms / cm 3 or less.

[0092] <Luminescence characteristics> Powder samples obtained by pulverizing the crystals of Examples 1 to 4 were prepared, and the luminescence characteristics of each sample were measured. Hereinafter, the sample prepared from the crystal of Example 1 is referred to as Sample 1, and the same applies to Examples 2 to 4.

[0093] For the measurement of photoluminescence (PL), a spectrofluorometer (F-7100, manufactured by Hitachi High-Tech Corporation) was used to measure the emission wavelength (λ ex ) and emission intensity when excited at a predetermined excitation wavelength (λ em ). Also, the emission wavelength (λ em ) to be detected was fixed at a predetermined wavelength, and the emission intensity when excited at each excitation wavelength (λ ex ) was measured to obtain an excitation spectrum. For X-ray radioluminescence (XRL) measurements, a fiber multi-channel compact spectrometer (Stellarnet Inc., Blue Wave UVN-50) is used, and the emission wavelength (λ) when excited with X-rays (Rigaku Corporation, 18kW X-ray generator RA-HF 18RB) is measured. em ) and luminescence intensity were measured.

[0094] Figure 6 shows the PL spectrum of sample 3. Here, the excitation wavelength (λ) ex The wavelength was 282 nm. In Figure 6, the emission intensity on the vertical axis is normalized based on the peak value. Also, in Figure 6, based on the main emission wavelengths described later, 450 nm is the detection wavelength (λ). em The excitation spectrum (normalized spectrum) of sample 3 obtained as shown is also presented.

[0095] Figure 6 suggests that the crystal in Example 3 has emission wavelengths in the range of approximately 360 nm to 700 nm. Since the emission is primarily in the range of approximately 420 nm to 520 nm, i.e., in the blue to green wavelength region, the crystal in Example 3 can be said to be useful as a scintillator material used in combination with, for example, a Si photodiode. The presence of blue emission wavelengths in the scintillator is expected to improve sensitivity to the Si photodiode. This may allow the Si photodiode to be used as a photoelectric converter.

[0096] Figure 7 shows the XRL spectrum of sample 3. In Figure 7, the emission intensity on the vertical axis is normalized to the peak value.

[0097] As shown in Figure 7, and as described above with reference to the PL spectrum in Figure 6, the crystal of Example 3 was suggested to have emission wavelengths in the range of approximately 380 nm to 700 nm.

[0098] Here, the density of the crystal (HfO2) in Example 3 is 9.68 g / cm³. 3 (Reported value) and ρ·(Z eff ) 4 The value is 220.60 × 106 On the other hand, the density of the CdWO4 crystal (manufactured by Nippon Crystal Optics Co., Ltd.) prepared as a comparative sample was 7.9 g / cm³. 3 (Reported value) and ρ·(Z eff ) 4 The value is 133.98 × 10 6 These results suggest that the oxide crystal of the present invention may have X-ray stopping power comparable to or exceeding that of CdWO4. eff ) 4 The value was calculated based on the reference (HP Schatzler., Int. J. Appl. Radiat. Isot., 1979, 30, 115-121.).

[0099] As described above, the present invention can provide an oxide crystal that does not contain harmful substances such as cadmium and has scintillation properties comparable to or better than CdWO4. Furthermore, the oxide crystal of the present invention is suitable for use in various materials and articles such as substrate materials, battery materials, sensor materials, dental materials, structural materials, and jewelry. Furthermore, the present invention can provide a method for producing the above-mentioned oxide crystals under milder conditions than conventional methods, particularly at lower temperatures. According to the manufacturing method of the present invention, chemically stable bulk single crystal growth and production are possible, making it suitable for large-scale and mass production, and reducing manufacturing costs. In addition, since no harmful substances such as cadmium are used, it is an environmentally friendly material, and the manufacturing process is also environmentally friendly. The oxide crystals and their manufacturing methods of the present invention, possessing these characteristics, are expected to be applied to a variety of uses, either as a scintillator material and its manufacturing method that replaces conventional CdWO4, or as oxide crystals and their manufacturing methods suitable for the various applications mentioned above. [Explanation of Symbols]

[0100] 10. Radiation detectors 11. Scintillator materials (scintillators) 12 Photoelectric Converter 20. Radiation Inspection Equipment 23 Radiation Source L light R radiation E. Radiation that penetrates the subject Sbj subject

Claims

1. General formula (Zr １－ｘ HF ｘ ) １－ｙ (RE ｚ M １－ｚ ) ｙ O ２－０．５ｙ－ｐ An oxide crystal containing hydrogen atoms (H), represented by the formula (wherein x, y, z, and p are each independently satisfying 0 ≤ x ≤ 1, 0 ≤ y ≤ 0.6, 0 ≤ z ≤ 1, -0.5 ≤ p ≤ 0.5, RE is selected from at least one rare earth element, and M is selected from at least one element from the group consisting of titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), magnesium (Mg), and calcium (Ca).

2. The concentration of hydrogen atoms is 1×10 １６ atoms / cm ３ or more and 1×10 ２３ atoms / cm ３ or less, and the oxide crystal according to claim 1.

3. The oxide crystal according to claim 1 or 2, having a crystal structure belonging to the P 1 21 / c 1 space group and having a monoclinic single phase, or having a crystal structure belonging to the F m -3 m space group and having a cubic single phase.

4. The oxide crystal according to any one of claims 1 to 3, wherein the rare earth element is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

5. The oxide crystal according to any one of claims 1 to 4, further containing an alkali metal and / or an alkaline earth metal other than M.

6. The concentration of the alkali metal and / or alkaline earth metal other than M is 1 × 10 １２ atoms / cm ３ The above 1 x 10 ２０ atoms / cm ３ The oxide crystal according to claim 5, wherein the range is as follows.

7. The oxide crystal according to any one of claims 1 to 6, further containing at least one element selected from the group consisting of aluminum (Al), gallium (Ga), and germanium (Ge).

8. A method for producing an oxide crystal according to any one of claims 1 to 7, comprising growing a crystal from a raw material containing each element contained in the crystal by hydrothermal synthesis in the presence of a first mineralizing agent which is an alkali metal and / or an alkaline earth metal other than M, or an acid mineralizing agent, or a mixed mineralizing agent of both, and a second mineralizing agent which is at least one selected from the group consisting of aluminum oxide, gallium oxide, and germanium dioxide.

9. The method according to claim 8, wherein the concentration of the first mineralizing agent is in the range of 1 M to 50 M.

10. The method according to claim 8 or 9, wherein the concentration of the second mineralizing agent is in the range of 0.01 M or more and 20 M or less.

11. The method according to any one of claims 8 to 10, wherein, in growing crystals by the hydrothermal synthesis method, the temperature is in the range of 400°C or more and less than 750°C, and the maximum achievable pressure is in the range of 25 MPa or more and 250 MPa or less.

12. A substrate material, battery material, sensor material, dental material, structural material, or jewelry comprising an oxide crystal according to any one of claims 1 to 7.

13. A scintillator material comprising an oxide crystal according to any one of claims 1 to 7.

14. The scintillator material according to claim 13, A photoelectric converter that detects light from the scintillator material and converts it into an electrical signal. A radiation detector equipped with the following features.

15. A radiation source that irradiates the subject with radiation, A radiation detector according to claim 14, which detects radiation passing through the subject, A radiation inspection device equipped with the following features.

Images