Phosphor and method for manufacturing the same

Abstract

To provide a novel phosphor which shows fluorescent properties even without using a rare earth element, and a method for manufacturing the phosphor.SOLUTION: A phosphor of the present invention contains an oxyhydroxide which contains at least Ba and In, and has a crystal structure in which a diffraction peak appears at least within the range of 2θ=8.91 to 9.41°, 18.12 to 18.62°, 23.73 to 24.23°, 27.44 to 27.94°, 29.75 to 30.25°, 31.73 to 32.23°, 39.56 to 40.06°, and 44.93 to 45.43°in a diffraction pattern measured by X-ray diffraction measurement.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a phosphor and a method for producing the same.

Background Art

[0002] White LED (Light Emitting Diode) lighting, which has advantages such as long life and low power consumption compared to conventional incandescent lamps and fluorescent lamps, has been rapidly spreading in recent years. This white LED lighting employs a mechanism that emits white light by combining a light emitting diode and an inorganic phosphor, and conventionally, rare earth-based phosphors have been widely used as the inorganic phosphor.

[0003] 10 O 17 :Eu 2+ is used for the blue-emitting phosphor, LaPO4:Ce 3+ ,Tb 3+ is used for the green-emitting phosphor, and Y2O3:Eu 3+ is used for the red-emitting phosphor.

[0004] However, rare earth elements such as Eu (europium), Ce (cerium), and Tb (terbium) that are activated as luminescent factors of phosphors are rare and expensive elements. Moreover, since the resources of rare earth elements are concentrated in some countries, there is a risk that the supply may become unstable, and there is also a concern that the price may further increase in the future.

[0005] 1-x (Mn,Ti) x )F6 (where x is the concentration of Mn or Ti and 0 < x ≦ 0.02.) has been proposed.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-210986 Summary of the Invention [Problem to be solved by the invention]

[0007] To create a white LED, it is necessary to prepare phosphors of three colors: green, red, and blue. Furthermore, there is a demand for a variety of colors in lighting equipment, etc. As such, there is a growing demand for rare-earth element-free phosphors that emit light in a variety of colors.

[0008] The present invention has been made in view of the above circumstances, and has as its object to provide a new phosphor that exhibits fluorescent properties without using rare earth elements, and a method for producing the same. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems. As a result, they have surprisingly found that an oxyhydroxide containing at least Ba and In and having a crystal structure in which diffraction peaks appear in the ranges of 2θ=8.91 to 9.41°, 18.12 to 18.62°, 23.73 to 24.23°, 27.44 to 27.94°, 29.75 to 30.25°, 31.73 to 32.23°, 39.56 to 40.06°, and 44.93 to 45.43° in a diffraction pattern measured by X-ray diffraction measurement exhibits fluorescent properties without the use of rare earth elements, leading to the completion of the present invention. Specifically, the present invention provides the following.

[0010] (1) Contains at least Ba and In; In the diffraction pattern measured by X-ray diffraction measurement, the diffraction peak is at least 2θ=8.91~9.41°, 18.12~18.62°, 23.73~24.23°, 27.44~27.94°, 29.75~30.25°, 31.73~32.23°, 39.56~40.06°, 44.93~45.43° A phosphor comprising an oxyhydroxide having a crystal structure appearing in the range of

[0011] (2) In the diffraction pattern of the oxyhydroxide measured by X-ray diffraction measurement, when the diffraction peak intensity appearing in the range of 2θ=27.44 to 27.94° is taken as 100%, each of the diffraction peaks is 29~43% (2θ=8.91~9.41°) 11~17% (2θ=18.12~18.62°) 9~13% (2θ=23.73~24.23°) 7~11% (2θ=29.75~30.25°) 30~45% (2θ=31.73~32.23°) 5~8% (2θ=39.56~40.06°) 8~12% (2θ=44.93~45.43°) The phosphor according to claim 1, having a crystal structure that appears at an intensity of

[0012] (3) The phosphor according to claim 1 or 2, wherein the mass loss when heated from 25° C. to 600° C. at a heating rate of 10° C. / min is 2.7% by mass or less relative to the mass before heating.

[0013] (4) A method for producing a phosphor according to claim 1 or 2, comprising heating a composite oxide containing Ba and In or a doped material thereof at 300°C or higher in an atmosphere containing 30% or more by volume of water vapor. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a new phosphor that exhibits fluorescent properties without using rare earth elements, and a method for producing the same. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of a perovskite structure. [Figure 2] 1 is a schematic diagram of a Brownmillerite structure. [Figure 3] Schematic diagram of Ba2In2O4(OH)2 with a cubic crystal structure. [Figure 4] 1 shows X-ray diffraction patterns of the oxyhydroxide sample of Example 1 and the samples of Comparative Examples 1 and 2. [Figure 5] 1 is a TG chart of the oxyhydroxide sample of Example 1 and the samples of Comparative Examples 1 and 2. [Figure 6] 1 is a Q-MS chart of an oxyhydroxide sample of Example 1. [Figure 7] 1 is a Q-MS chart of the sample of Comparative Example 2. [Figure 8] 1 shows fluorescence spectra of the oxyhydroxide samples of Example 1, Example 2, and Comparative Example 2. [Figure 9] 1 shows X-ray diffraction patterns of the oxyhydroxide samples of Examples 1, 6, and 7. DETAILED DESCRIPTION OF THE INVENTION

[0016] A specific embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and modifications are possible within the scope of the present invention.

[0017] 1. Phosphor The phosphor according to this embodiment contains at least Ba and In, and comprises an oxyhydroxide having a crystalline structure in which, in a diffraction pattern measured by X-ray diffraction measurement, diffraction peaks appear in the ranges of 2θ=8.91 to 9.41°, 18.12 to 18.62°, 23.73 to 24.23°, 27.44 to 27.94°, 29.75 to 30.25°, 31.73 to 32.23°, 39.56 to 40.06°, and 44.93 to 45.43°.

[0018] Such an oxyhydroxide exhibits pale blue fluorescence without containing any rare earth elements. Furthermore, when heat-treated in a nitrogen atmosphere, it exhibits a yellow color. The crystal structure of the oxyhydroxide of this embodiment is currently unclear, but from the X-ray diffraction pattern, it is believed to be a misfit layered compound in which InO layers and Ba(O,OH) layers are alternately stacked, with the repeating period of the crystal structure differing in one direction in the plane of each layer. Furthermore, the reason why such an oxyhydroxide exhibits fluorescence is also currently unclear.

[0019] [Oxyhydroxide] The oxyhydroxide of this embodiment has a crystalline structure in which, in a diffraction pattern measured by X-ray diffraction measurement, diffraction peaks appear at least in the ranges of 2θ=8.91 to 9.41°, 8.12 to 18.62°, 23.73 to 24.23°, 27.44 to 27.94°, 29.75 to 30.25°, 31.73 to 32.23°, 39.56 to 40.06°, and 44.93 to 45.43°. The peak intensity ratios of these peaks are not particularly limited, as they merely represent the orderliness of specific directions in the crystalline structure. Furthermore, since other peaks may appear depending on the orderliness of the crystalline structure or the presence of impurities, diffraction peaks other than these diffraction peaks may also appear. Note that "a diffraction peak appears in the range of 2θ=X to Y°" means that the peak top of the peak is included in the range of X to Y. Therefore, for example, in the case of a broad peak, it is not necessary for the peak to be included from end to end.

[0020] As will be described in detail later, these diffraction peaks do not coincide with the positions of the diffraction peaks that appear in Ba2In2O4(OH)2, which is known as an oxyhydroxide of Ba and Indium. Furthermore, neither the ICDD (International Centre for Diffraction Data) nor the ICSD (Inorganic Crystal Structure Database) databases contain any compounds that contain at least Ba and In and that match these patterns.

[0021] The peak intensity ratios in the diffraction pattern measured by X-ray diffraction measurement are not limited as described above, but the ordered structure of the crystal can be greatly affected by, for example, the production method. As an example, the production method described below produces an oxyhydroxide having the peak intensity ratios shown in Table 1 below. Note that Table 1 shows the ratios of the peak intensities of the diffraction peaks other than the intensity (i.e., peak height) of the diffraction peak appearing at 2θ = 27.44 to 27.94°, taken as 100%.

[0022] [Table 1]

[0023] Such an oxyhydroxide can contain doping elements or impurity elements at each of the Ba sites, In sites, O sites, and OH sites relative to the total number of ions.

[0024] The doping element is not particularly limited, but may include, for example, one or more elements selected from the group consisting of manganese (Mn) and rare earth elements. The rare earth elements are not particularly limited, but examples thereof include 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), lutetium (Lu), yttrium (Y), and scandium (Sc). The phosphor according to this embodiment exhibits fluorescent properties even without these elements, but the phosphor may include these elements.

[0025] The impurity elements are not particularly limited, but may include, for example, Ca, Sr, and La located at the Ba site, and Ga, Al, Sc, and Fe located at the In site. Furthermore, impurity elements such as F and Cl may be included at the O site. Furthermore, each site may contain lattice defects.

[0026] The amount of doping element contained in the Ba site and the In site is not particularly limited, but may be, for example, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2% or less by molar ratio relative to the total amount of Ba and In. The amount of doping element contained in the Ba site and the In site may be 0% or more (including 0%), 0.01% or more, 0.05% or more, 0.1% or more, 0.5% or more, or 1% or more.

[0027] The amount of impurity elements contained in the Ba site and the In site is not particularly limited, but may be, for example, 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, or 0.1% or less in terms of molar ratio relative to the total amount of Ba and In. The amount of impurity elements contained in the Ba site and the In site may be 0% or more (including 0%), 0.01% or more, 0.05% or more, 0.1% or more, 0.5% or more, or 1% or more.

[0028] The oxyhydroxide according to this embodiment has high thermal stability. Specifically, when heated from 25°C to 600°C at a heating rate of 10°C / min, the mass loss is preferably 2.7% by mass or less, 2.5% by mass or less, 2.2% by mass or less, 2.0% by mass or less, or 1.7% by mass or less, or 1.5% by mass or less, relative to the mass before heating. However, the lower the mass loss, the better, and it is not particularly limited, and may be, for example, 0% by mass or more, 0.1% by mass or more, 0.5% by mass or more, or 1% by mass or more. Note that this mass loss is assumed to be primarily due to the desorption of water. In other words, if other compounds are desorbed, such as when the sample is coated with an organic compound, they should be removed to an extent that does not affect the mass loss before measurement. Note that the mass loss measured for Ba2In2O4(OH)2, a conventionally known tetragonal crystal structure, is approximately 2.9% by mass.

[0029] 2. Phosphor manufacturing method An example of a method for producing the above-mentioned phosphor will be described below. Such a phosphor can be produced by heating a composite oxide containing Ba and In or a doped material thereof (hereinafter collectively referred to as "composite oxide containing Ba and In") at 300°C or higher in an atmosphere containing 30% or more by volume of water vapor.

[0030] In one embodiment, the raw material composite oxide containing Ba and In contains, as a main phase, the metal oxide Ba2In2O5 or a doped material thereof, which has a crystal structure called an orthorhombic Brownmillerite structure, represented by the general formula A2B2O5. This crystal structure corresponds to an atomic arrangement in which one-sixth of the oxygen atoms are missing from the perovskite structure, represented by the general formula ABO3. FIG. 1 is a schematic diagram of the perovskite structure. FIG. 2 is a schematic diagram of the Brownmillerite structure. As shown in FIG. 2, in Ba2In2O5, InO6 octahedra and InO4 tetrahedra are alternately stacked, and the oxygen vacancy sites are ordered.

[0031] This Ba- and In-containing composite oxide is highly hygroscopic. When it is exposed to a water vapor partial pressure (p(HO)) of approximately 30 hPa (approximately 2% by volume of water vapor, close to the saturated water vapor concentration at room temperature) for several days, the oxygen vacancy sites react with water molecules in the gas phase (see equation (1) below), and the water molecules are incorporated into the crystal lattice, transforming it into Ba2In2O4(OH)2 with a tetragonal crystal structure (see W. Fischer, G. Reck, T. Schober, Solid State Ionics 116, 211 (1999)). Figure 3 is a schematic diagram of Ba2In2O4(OH)2 with a cubic crystal structure. H2O+V o ·· +O o× →2OH o · ···(1) (V o ·· : Oxygen vacancy site, O o × : lattice oxygen)

[0032] In the method for producing an oxyhydroxide according to the present embodiment, a composite oxide containing Ba and In as a raw material is subjected to a heat treatment at 300°C or higher in an atmosphere containing 30% or more by volume of water vapor, i.e., under conditions of higher humidity and higher temperature, to obtain an oxyhydroxide different from BaInO(OH). The oxyhydroxide thus obtained exhibits fluorescent properties even without containing a rare earth metal.

[0033] The heat treatment temperature is not particularly limited as long as it is 300°C or higher, but is preferably 350°C or higher, 370°C or higher, 400°C or higher, 450°C or higher, or 470°C or higher. By setting the heat treatment temperature at a required value or higher, the resulting oxyhydroxide exhibits fluorescent properties. In particular, at 400°C or higher, a clear phase transition occurs, resulting in the formation of an oxyhydroxide that exhibits stronger fluorescent properties. On the other hand, the heat treatment temperature is preferably 800°C or lower, 750°C or lower, 720°C or lower, 700°C or lower, 770°C or lower, or 650°C or lower. Setting the heat treatment temperature at a required value or lower can suppress desorption of water from the oxyhydroxide once formed.

[0034] The atmosphere used in the treatment is not particularly limited as long as it contains 30% or more by volume of water vapor. However, the amount of water vapor in the atmosphere is preferably, for example, 32% or more by volume, 35% or more by volume, 37% or more by volume, 40% or more by volume, or 42% by volume. By ensuring that the amount of water vapor is equal to or greater than the required value, the resulting oxyhydroxide exhibits fluorescent properties. On the other hand, the amount of water vapor in the atmosphere may be, for example, 100% or less by volume, 97% or less by volume, 95% or less by volume, 92% or less by volume, 90% or less by volume, 87% or less, or 85% or less by volume. By ensuring that the amount of water vapor in the atmosphere is equal to or less than the required value, gas blockage and other problems can be prevented, and reaction efficiency can be improved. It is preferable that the gas other than water vapor in the atmosphere be one that does not react with the composite oxide containing Ba and In, the resulting oxyhydroxide, or water vapor, or that does not release compounds that react with these compounds during heat treatment due to decomposition or the like. Examples of such gases include nitrogen and argon, which are generally known as inert gases. In the following description, gases that can be used as gases other than water vapor in the atmosphere will be referred to as "inert gases" for convenience.

[0035] The heat treatment time is not particularly limited, but is preferably 30 minutes or more, 1 hour or more, 1.5 hours or more, 2 hours or more, or 2.5 hours or more. By ensuring that the heat treatment time is at least the required value, the reaction of forming the oxyhydroxide can be sufficiently promoted. On the other hand, the heat treatment time may be, for example, 1000 hours or less, 700 hours or less, 500 hours or less, 400 hours or less, 300 hours or less, 200 hours or less, 100 hours or less, 70 hours or less, 50 hours or less, 40 hours or less, 30 hours or less, 20 hours or less, or 10 hours or less.

[0036] The amount of water vapor in the atmosphere described above is significantly greater than the saturated water vapor amount of 2.4% by volume at 20° C. Specific means for achieving such a water vapor amount will be described below.

[0037] For example, a composite oxide containing Ba and In is placed in a space (hereinafter sometimes referred to as the "reaction space") set to a predetermined temperature of 300°C or higher. Liquid water is then introduced into this reaction space. The water introduced into the reaction space, which is maintained at a temperature above its boiling point, immediately evaporates into water vapor, which reacts with the composite oxide containing Ba and In to form an oxyhydroxide.

[0038] This reaction system may be a batch type or a continuous type, but a continuous type is preferable from the viewpoint of continuously introducing a gas containing water vapor to efficiently react the composite oxide containing Ba and In with the water vapor.

[0039] When the reaction system is a batch system, the reaction space is not particularly limited as long as it is sealed and can maintain the temperature of the heat treatment. For example, various containers and reactors can be used. During the heat treatment, a heating device such as a heater may be provided around the container or reactor to heat the interior. Note that as the heat treatment progresses, the amount of water vapor decreases as it reacts with Ba2In2O5. To obtain the oxyhydroxide of this embodiment, it is necessary to treat the composite oxide containing Ba and In in an atmosphere with a water vapor content of 30% by volume or more for at least a predetermined time. Therefore, if the amount of water vapor in the system falls below 30% by volume, new water can be introduced.

[0040] When the reaction system is a continuous system, the reaction space is not particularly limited as long as it can continuously introduce and exhaust water vapor (and an inert gas as needed) and can maintain the temperature of the heat treatment, and for example, a cylindrical reaction tube is used. The operation when using such a reaction tube will be described in more detail below.

[0041] The reaction tube is provided with a gas inlet, through which an inert gas is introduced, passed through the inside of the reaction tube body, and discharged from the gas outlet. A composite oxide containing Ba and In is disposed inside the reaction tube body as a precursor. A heating device, such as a heater, is disposed at the location where the precursor is disposed and in the surrounding area, thereby maintaining these locations at 300°C or higher. A water inlet is provided upstream of the location where the composite oxide containing Ba and In is disposed in the gas flow direction to introduce water into the reaction tube. The water inlet is connected to a syringe pump, and water is introduced from the water inlet in an amount set by the syringe pump.

[0042] In the reaction tube arranged in this manner, an inert gas is introduced through the gas inlet. Meanwhile, water introduced into the high-temperature reaction tube in a liquid state through the reaction water inlet is immediately converted into steam and flows downstream to the precursor location together with the inert gas flowing from upstream of the water inlet. The steam that reaches the precursor P in this manner reacts with the precursor to form an oxyhydroxide. The inert gas and unreacted steam are then discharged through the gas outlet. The piping may be straight or curved, and its orientation is not limited, and may be oriented up, down, left, or right.

[0043] In such a case, the sum of the flow rate of the water vapor gas and the flow rate of the inert gas (hereinafter referred to as the "total gas flow rate") is not particularly limited, but for example, the flow rate per 1 g of the raw material composite oxide containing Ba and In is preferably 10 mL / min or more, 20 mL / min or more, 30 mL / min or more, 40 mL / min or more, 50 mL / min or more, 60 mL / min or more, 70 mL / min or more, 80 mL / min or more, 90 mL / min or more, or 100 mL / min or more. By ensuring that the total gas flow rate is equal to or greater than the required value, the oxyhydroxide of this embodiment can be formed more quickly. On the other hand, the sum of the total gas flow rates may be 500 mL / min or less, 400 mL / min or less, 300 mL / min or less, or 200 mL / min or less per 1 g of the composite oxide containing Ba and In.

[0044] The composite oxide containing Ba and In as a raw material is not particularly limited, and the manufacturing method thereof is also not limited, and for example, those manufactured by conventionally known manufacturing methods (various solid-phase methods and liquid-phase methods) can be used.

[0045] For example, a powder mixture of a Ba source and an In source (and other metal sources as needed) may be pre-fired at 700° C. or higher and lower than 1100° C. for 1 hour to 50 hours, and then fired at 1100° C. or higher and 1500° C. or lower for 1 hour to 50 hours. The pre-fired and pre-fired temperatures may be in any atmosphere as long as a sufficient amount of oxygen is supplied, and may be, for example, air.

[0046] Alternatively, for example, solutions of a Ba source and an In source (and other metal sources, if necessary) are mixed to a Ba:In ratio of approximately 1.1:1 (e.g., 1.05:1 to 1.15:1, 1.07:1 to 1.12:1, or 1.09:1 to 1.11:1), and citric acid is added in an amount 3 to 5 times the total metal equivalent to obtain a gel. This gel may be pre-baked once or multiple times, followed by a main baking at 100°C to 1500°C for 1 hour to 50 hours. The pre-baking and main baking may be performed in any atmosphere that provides a sufficient supply of oxygen, such as air. When performing multiple baking, the mixture may be heated, for example, at 400°C to 480°C for 10 minutes to 20 hours, at 480°C to 800°C for 10 minutes to 20 hours, or at 800°C to 1100°C for 1 hour to 50 hours.

[0047] In this case, oxides, carbonates, nitrates, acetates, lactates, etc. can be used as the Ba source, In source, and other metal sources. Specifically, BaCO3, BaO2, Ba(NO3)2, Ba(CH3COO)2, Ba(CH3CH(OH)COO)2, etc. can be used as the Ba source. Furthermore, In2O3, In(NO3)3, etc. can be used as the In source. [Example]

[0048] The present invention will be described in more detail below by showing specific examples, but the present invention is not limited to the following examples in any way.

[0049] [Sample preparation] [Example 1] (Synthesis of raw material Ba-In oxide) A barium solution was obtained by dissolving 3.3 g of BaCO3 and 5.2 g of lactic acid in 20 mL of water. Also, an indium solution was obtained by dissolving 2.1 g of In2O3 in 30 mL of concentrated nitric acid. A mixed solution was prepared by mixing 20 mL of the barium solution and 5 mL of the indium solution (the molar ratio of Ba:In was 1.1:1).

[0050] The resulting mixed solution was left to stand overnight in a dryer at 120°C to allow gelation. The resulting gel was calcined in air at 450°C for 0.5 hours using a mantle heater. It was then fired in air at 550°C for 1 hour in a box furnace to remove organic matter. The resulting calcined powder was calcined in air at 1000°C for 10 hours, and then fired in air at 1200°C for 10 hours to obtain a raw material Ba-In oxide precursor.

[0051] The reaction between the raw material Ba-In oxide and water vapor was carried out using a gas-flow type reaction tube as the reaction field. During the reaction, nitrogen gas was introduced into the reaction tube through a gas inlet, passed through the inside of the tube, and continuously discharged through a gas outlet. 0.5 g of the raw material Ba-In oxide was placed in the center of the reaction tube. Heaters were placed at and around the location of the Ba2In2O5, and these locations were heated to 500 °C during the reaction. In addition, a water inlet for introducing water into the reaction tube was installed downstream of the gas inlet and upstream of the location of the Ba-In oxide, at the heater location (500 °C).

[0052] In this setup, nitrogen gas was introduced through the gas inlet of the reaction tube at a rate of 20 mL / min during the reaction. Liquid water was introduced through the water inlet at a rate of 64 μL / min (80 mL / min, 80% by volume, equivalent to water vapor, assuming an ideal gas). The Ba-In oxide was heated under these conditions for 3 hours to obtain an oxyhydroxide sample.

[0053] [Example 2] An oxyhydroxide sample was obtained in the same manner as the sample in Example 1, except that the raw material Ba—In oxide was annealed at 800°C for 1 hour in a N atmosphere before being introduced into the gas flow type reaction tube, and heavy water (DO) was used as the water vapor introduced into the gas flow type reaction tube.

[0054] [Example 3] An oxyhydroxide sample was obtained in the same manner as in Example 1, except that 0.0072 g of La(NO) was dissolved in 10 mL of ultrapure water to obtain a lanthanum solution, and 10 mL of barium solution, 5 mL of indium solution, and 10 mL of lanthanum solution were mixed to prepare a mixed solution (the molar ratio of Ba:In:La was 1.093:1:0.005).

[0055] [Example 4] An oxyhydroxide sample was obtained in the same manner as in Example 1, except that 0.029 g of Sm2O3 was dissolved in 10 mL of 13.8 mol / L concentrated nitric acid to obtain a samarium solution, and a mixed solution of 10 mL of barium solution, 5 mL of indium solution, and 5 mL of samarium solution was prepared (the molar ratio of Ba:In:Sm was 1.047:1:0.05).

[0056] [Example 5] An oxyhydroxide sample was obtained in the same manner as in Example 1, except that 0.029 g of Eu2O3 was dissolved in 10 mL of concentrated nitric acid to obtain a europium solution, and a mixed solution of 10 mL of barium solution, 5 mL of indium solution, and 5 mL of europium solution was prepared (the molar ratio of Ba:In:Eu was 1.047:1:0.05).

[0057] [Example 6] The oxyhydroxide sample of Example 1 was heated at 500°C for 3 hours in an N2 atmosphere to obtain an oxyhydroxide sample of Example 6.

[0058] [Example 7] The oxyhydroxide sample of Example 6 was introduced into the reaction tube again and subjected to steam treatment under the same conditions as in Example 1, thereby obtaining an oxyhydroxide sample of Example 7.

[0059] [Example 8] The oxyhydroxide sample of Example 3 was heated at 500°C for 3 hours in an N2 atmosphere to obtain the oxyhydroxide sample of Example 6.

[0060] [Example 9] The oxyhydroxide sample of Example 4 was heated at 500°C for 3 hours in an N2 atmosphere to obtain the oxyhydroxide sample of Example 6.

[0061] [Comparative Example 1] A Ba—In oxide was produced in the same manner as in Example 1 except that the molar ratio of Ba:In was 1:1. This was used as a sample for Comparative Example 1.

[0062] Comparative Example 2 A sample was obtained in the same manner as in Example 1, except that the heating temperature of the heater was changed to 200°C and the Ba—In oxide was heated.

[0063] [Sample analysis] [X-ray diffraction measurement] X-ray diffraction measurements were performed on the oxyhydroxide sample of Example 1 and the samples of Comparative Examples 1 and 2. FIG. 4 shows the X-ray diffraction patterns of the oxyhydroxide sample of Example 1 and the samples of Comparative Examples 1 and 2. From the X-ray diffraction pattern in FIG. 4, it was confirmed that the sample of Comparative Example 1 was a single phase Ba2In2O5. Furthermore, it was confirmed that the sample of Comparative Example 2 was a single phase Ba2In2O4(OH)2 having a tetragonal crystal structure. On the other hand, the X-ray diffraction pattern of the sample of Example 1 did not match either the X-ray diffraction pattern of Ba2In2O5 or the X-ray diffraction pattern of Ba2In2O4(OH)2 having a tetragonal crystal structure. Furthermore, it was confirmed that there are no compounds in the ICDD and ICSD databases that contain at least Ba and In and that match these patterns.

[0064] Table 2 shows the position of each peak, the corresponding d value, and the intensity ratio of the diffraction peak.

[0065] [Table 2]

[0066] [TG and Q-MS measurements] TG measurements were carried out on the sample of Example 1 and the samples of Comparative Examples 1 and 2. Fig. 5 shows TG charts of the oxyhydroxide sample of Example 1 and the samples of Comparative Examples 1 and 2.

[0067] Furthermore, Q-MS measurements were performed on the sample of Example 1 and the samples of Comparative Examples 1 and 2. Fig. 6 is a Q-MS chart of the oxyhydroxide sample of Example 1. Fig. 7 is a Q-MS chart of the sample of Comparative Example 2.

[0068] 5 to 7, the sample of Comparative Example 2 showed a large weight loss at approximately 300°C. The weight loss rate was approximately 3%. On the other hand, the sample of Example 1 did not show a large weight loss until approximately 700°C. This indicates that the sample of Example 1 can retain hydroxide ions up to high temperatures.

[0069] Furthermore, from the results of the qualitative analysis of the desorbed gas in FIG. 5, it can be said that in both the sample of Example 1 and the sample of Comparative Example 2, desorption of water from the crystal lattice occurred, which corresponds to the weight loss behavior.

[0070] [Evaluation of fluorescence spectra] The samples of Examples 1 to 9 and Comparative Examples 1 and 2 were irradiated with UV light of λ=254 nm and visually evaluated for their fluorescent properties. Table 3 shows the visual evaluation results of the fluorescent properties.

[0071] [Table 3]

[0072] 8 shows the fluorescence spectra of the oxyhydroxide samples of Examples 1 and 2 and Comparative Example 2. In Fig. 8, the peaks appearing at approximately 250 to 280 nm and approximately 500 to 530 nm are due to the characteristics of the analyzer used to measure the fluorescence spectra. In the fluorescence spectra shown in Fig. 8, broad peaks were observed at 420 to 570 nm for the oxyhydroxide samples of Examples 1 and 2.

[0073] The evaluation results of Example 1 confirmed that the oxyhydroxide according to this embodiment exhibits fluorescent properties even without containing a rare earth element. From the above, it was found that the oxyhydroxide according to this embodiment is an effective material as a rare earth element-free phosphor material.

[0074] Furthermore, the evaluation results of Examples 2 to 5 revealed that the pale blue fluorescent properties did not change significantly even when hydrogen was replaced with deuterium or when doped with a rare earth element, suggesting that the fluorescent properties of the oxyhydroxide according to this embodiment are derived from the crystal structure of the oxyhydroxide.

[0075] Comparing the evaluation results of Examples 1 and 6, it was confirmed that the fluorescent properties of the oxyhydroxide sample of Example 1 changed from pale blue to yellow when it was subjected to heat treatment. It was also confirmed that the fluorescent properties of the oxyhydroxide sample of Example 6, which emitted yellow light, returned to pale blue when it was subjected to steam treatment. Therefore, it can be said that the change from pale blue to yellow by heat treatment in the oxyhydroxide sample of this embodiment is reversible. Figure 9 shows the X-ray diffraction patterns of the oxyhydroxide samples of Examples 1, 6, and 7. This reversibility was also confirmed from the X-ray diffraction patterns.

[0076] From these results and the result in FIG. 5 that partial release of hydroxide ions occurs when the oxyhydroxide sample of Example 1 is heated, it is presumed that hydroxide ions of the oxyhydroxide are somehow involved in luminescence.

[0077] Furthermore, similar trends were observed when doped with lanthanum (see Examples 4 and 8) and when doped with samarium (see Examples 5 and 9), suggesting that the fluorescent properties of oxyhydroxides do not depend on the presence or absence of a fluorescent center.

Claims

1. Contains at least Ba and In, In a diffraction pattern measured by X-ray diffraction measurement, the diffraction peaks are at least 2θ=8.91-9.41°, 18.12-18.62°, 23.73-24.23°, 27.44-27.94°, 29.75-30.25°, 31.73-32.23°, 39.56-40.06°, 44.93-45.43° A phosphor comprising an oxyhydroxide having a crystal structure appearing in the range of

2. In the diffraction pattern of the oxyhydroxide measured by X-ray diffraction measurement, when the diffraction peak intensity appearing in the range of 2θ = 27.44 to 27.94 ° is set to 100%, each of the diffraction peaks is 29~43% (2θ=8.91~9.41°) 11~17% (2θ=18.12~18.62°) 9~13% (2θ=23.73~24.23°) 7~11% (2θ=29.75~30.25°) 30~45% (2θ=31.73~32.23°) 5~8% (2θ=39.56~40.06°) 8~12% (2θ=44.93~45.43°) The phosphor of claim 1 , having a crystalline structure that appears at an intensity of

3. 3. The phosphor according to claim 1, wherein the mass loss when heated from 25° C. to 600° C. at a heating rate of 10° C. / min is 2.7% by mass or less relative to the mass before heating.

4. 3. A method for producing a phosphor according to claim 1, wherein a composite oxide containing Ba and In or a doped composite oxide thereof is heated at 300° C. or higher in an atmosphere containing 30% or more by volume of water vapor to obtain the phosphor according to claim 1.

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