Structure, infrared detection device, light-emitting device, and method for producing structure

Abstract

A structure (1) comprises a base material (10) that contains a continuous phase (11) of a polycrystalline body of a complex fluoride containing an alkali metal. The structure (1) contains at least 85 mass% of an inorganic substance, and the structure (1) contains at least 50 mass% polycrystalline body of a complex fluoride. The porosity of the structure (1) is 30% or less, the median value of the pore diameter of the structure (1) is 500 nm or less, and the thickness of the structure (1) is 10 μm or thicker.

Description

Structure, infrared detector, light-emitting device, and method for manufacturing the structure

[0001] The present invention relates to a structure, an infrared detection device, a light emitting device, and a method for manufacturing a structure.

[0002] Conventionally, infrared-transmitting windows based on inorganic fluorides have been used for special applications in the fields of academic research and industry, such as window materials for scientific and chemical instruments. ２ , BaF ２ , MgF ２ The document discloses a Fourier transform infrared spectrophotometer that includes a measurement cell made of one material selected from the group consisting of LiF, LiF, and ZnSe, and that measures fluorine-based gases in a sample that contains corrosive gases.

[0003] International Publication No. 2019 / 176624

[0004] Meanwhile, technologies for sensing various gases and flames using infrared detection elements and infrared-transmitting optical filters are known. However, the alkali metal fluorides described above are highly hygroscopic and may not be suitable for general applications such as gas sensors and flame detection sensors. Furthermore, alkaline earth metal fluorides have high melting points of 1200 to 1500°C, so structures with high infrared transmittance may not be manufactured without using advanced technology requiring high temperatures of at least 1000°C or higher.

[0005] The present invention has been made in view of the problems associated with the prior art. An object of the present invention is to provide a structure suitable for use as an infrared-transmitting window for a gas sensor or a flame detection sensor, and an infrared detection device using the same. Another object of the present invention is to provide a method for manufacturing the structure, which can be manufactured using a simple low-temperature process.

[0006] In order to achieve the above object, a structure according to a first aspect of the present invention comprises a base material including a continuous phase of a polycrystalline body of a complex fluoride containing an alkali metal, the structure comprising 85 mass % or more of an inorganic substance, 50 mass % or more of the polycrystalline body of the complex fluoride, a porosity of the structure being 30% or less, a median pore diameter of the structure being 500 nm or less, and a thickness of the structure being 10 μm or more.

[0007] An infrared detection device according to a second aspect of the present invention includes a structure.

[0008] A light emitting device according to a third aspect of the present invention includes a structure.

[0009] A method for producing a structure according to a fourth aspect of the present invention includes a step of pressurizing and heating raw materials containing at least one of a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal and water, and a complex fluoride containing at least one of a hydroxyl group and a water molecule under conditions of a pressure of 10 to 600 MPa and a temperature of 50 to 300° C. The structure contains 85% by mass or more of an inorganic substance, 50% by mass or more of a polycrystalline body of the complex fluoride, a porosity of the structure is 30% or less, a median pore size of the structure is 500 nm or less, and a thickness of the structure is 10 μm or more.

[0010] FIG. 1 is a cross-sectional view schematically showing an example of a structure according to this embodiment. FIG. 2 is an enlarged cross-sectional view schematically showing another example of a structure according to this embodiment. FIG. 3 is a cross-sectional view schematically showing an example of an infrared detection device according to this embodiment. FIG. 4 is a schematic view showing an example of a light-emitting device according to this embodiment. FIG. 5 is a cross-sectional view of Na obtained by synthesis. ３ AlF ６ The SEM image of the powder was observed at a magnification of 10,000 times. ２ NaAlF ６ 7 is an SEM image of the powder observed at 10,000x magnification. ３FIG. 8 is an SEM image of the powder observed at 10,000x magnification. FIG. 8 is an XRD pattern of the powder of the test sample according to Example 1. FIG. 9 is an XRD pattern of the powder of the test sample according to Example 2. FIG. 10 is an XRD pattern of the powder of the raw material and test sample according to Example 3. FIG. 11 is an XRD pattern of the powder of the raw material and test sample according to Example 4. FIG. 12 is an XRD pattern of the powder of the raw material and test sample according to Example 5. FIG. 13 is a secondary electron image of the CP-processed (cross-section polisher-processed) cross section of the test sample according to Example 1 observed at 10,000x magnification. FIG. 14 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 1 observed at 10,000x magnification. FIG. 15 is a secondary electron image of the CP-processed cross section of the test sample according to Example 2 observed at 10,000x magnification. FIG. 16 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 2, observed at 10,000x magnification. FIG. 17 is a secondary electron image of the CP-processed cross section of the test sample according to Example 3, observed at 10,000x magnification. FIG. 18 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 3, observed at 10,000x magnification. FIG. 19 is a secondary electron image of the CP-processed cross section of the test sample according to Example 4, observed at 10,000x magnification. FIG. 20 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 4, observed at 10,000x magnification. FIG. 21 is a secondary electron image of the CP-processed cross section of the test sample according to Example 5, observed at 10,000x magnification. FIG. 22 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 5, observed at 10,000x magnification. Fig. 23 is a secondary electron image of the CP-processed cross section of the test sample according to Example 1, observed at a magnification of 2,000 times. Fig. 24 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 1, observed at a magnification of 2,000 times. Fig. 25 is a secondary electron image of the CP-processed cross section of the test sample according to Comparative Example 1, observed at a magnification of 2,000 times. Fig. 26 is a backscattered electron image of the CP-processed cross section of the test sample according to Comparative Example 1, observed at a magnification of 2,000 times. Fig. 27 is a secondary electron image of the CP-processed cross section of the test sample according to Example 3, observed at a magnification of 2,000 times.FIG. 28 is a backscattered electron image of the CP-processed cross section of the test sample according to Example 3, observed at 2,000x magnification. FIG. 29 is a secondary electron image of the CP-processed cross section of the test sample according to Comparative Example 2, observed at 2,000x magnification. FIG. 30 is a backscattered electron image of the CP-processed cross section of the test sample according to Comparative Example 2, observed at 2,000x magnification. FIG. 31 is an infrared spectrum of the test samples according to Examples 1 and 2, measured by the transmission method. FIG. 32 is an infrared spectrum of the test samples according to Examples 3 to 5, measured by the transmission method. FIG. 33 is an infrared spectrum of the test samples according to Comparative Examples 1 and 2, measured by the transmission method. FIG. 34 is a secondary electron image of the cut surface of the test sample according to Example 6, observed at 10,000x magnification. FIG. 35 is a secondary electron image of the cut surface of the test sample according to Example 6, observed at 2,000x magnification. FIG. 36 is a secondary electron image of the fractured surface of the test sample according to Comparative Example 3, observed at a magnification of 10,000 times. FIG. 37 is a secondary electron image of the fractured surface of the test sample according to Comparative Example 3, observed at a magnification of 2,000 times. FIG. 38 is a secondary electron image of the fractured surface of the test sample according to Example 7, observed at a magnification of 10,000 times. FIG. 39 is a secondary electron image of the fractured surface of the test sample according to Example 7, observed at a magnification of 2,000 times. FIG. 40 is a secondary electron image of the fractured surface of the test sample according to Comparative Example 4, observed at a magnification of 10,000 times. FIG. 41 is a secondary electron image of the fractured surface of the test sample according to Comparative Example 4, observed at a magnification of 2,000 times. FIG. 42 is a secondary electron image of the Na obtained in Example 8. ３ AlF ６ 43 shows an SEM image of the Na powder obtained by heat treatment at 300° C. in Example 9. ３ AlF ６ 44 shows an SEM image of the Na powder obtained by heat treatment at 400° C. in Example 10. ３ AlF ６ 45 shows an SEM image of the Na powder obtained by heat treatment at 500° C. in Example 11. ３ AlF ６ The SEM images of the powders obtained in each example are shown in FIG. ３ AlF ６ 47 is an XRD pattern of the powder of Example 9. ３ AlF６ FIG. 48 shows a secondary electron image of the structure formed from the powder of Example 9. ３ AlF ６ FIG. 49 is a backscattered electron image of the structure formed from the powder. ３ AlF ６ 50 is a secondary electron image of the structure formed from the powder of Example 10. ３ AlF ６ 51 is a backscattered electron image of the structure formed from the powder. ３ AlF ６ FIG. 52 is a secondary electron image of the structure formed from the powder of Example 11. ３ AlF ６ FIG. 53 is a backscattered electron image of a structure formed from powder. FIG. 53 is a graph comparing the linear transmittance of the structures obtained in each example. FIG. 54 is a graph showing the relationship between heat treatment temperature and relative density. FIG. 55 is a graph showing the relationship between heat treatment temperature and linear transmittance. FIG. 56 is a TG curve obtained by thermogravimetry of Examples 8 and 10. FIG. 57 is a graph showing the relationship between the first weight loss rate and the second weight loss rate.

[0011] The structure, infrared detector, light emitting device, and method for manufacturing the structure according to the present embodiment will be described in detail below with reference to the drawings. Note that the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions.

[0012] 1, the structure 1 of this embodiment includes a base material 10. The base material 10 includes a continuous phase 11 of a polycrystalline body of a complex fluoride. The structure 1 of this embodiment is a ceramic structure.

[0013] The complex fluoride contains an alkali metal. The complex fluoride may contain at least one alkali metal selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, for example. Alkali metal fluorides have high solubility in water, but complex fluorides containing an alkali metal have low solubility in water. The solubility of alkali metal fluorides in 100 g of water at 25°C is, for example, 0.134 g for LiF, 4.13 g for NaF, 102 g for KF, 300 g for RbF, and 573 g for CsF. On the other hand, the solubility of complex fluorides containing an alkali metal in 100 g of water at 25°C is, for example, 0.134 g for NaF, 4.13 g for NaF, 102 g for KF, 300 g for RbF, and 573 g for CsF. ３ AlF ６ 0.042 g, NaMgF ３ is 0.025g.

[0014] The complex fluoride may contain, as a main component, at least one additional metal selected from the group consisting of fluorine, an alkali metal, and an alkaline earth metal, aluminum, gallium, indium, zinc, and yttrium. Specifically, the additional metal may contain at least one metal selected from the group consisting of magnesium, calcium, strontium, barium, aluminum, gallium, indium, zinc, and yttrium. Such complex fluorides have low refractive index anisotropy, thereby improving the transmittance of infrared light. Furthermore, inorganic substances containing these metal elements can easily form the structure 1 by a pressurized and heated method, as described below. The term "main component" as used herein means that the total content of fluorine, alkali metal, and additional metal contained in the complex fluoride is 80% or more in molar ratio. The total content may be 85% or more, 90% or more, 95% or more, or even 100%.

[0015] The complex fluoride is specifically A ３ AlF ６ and ABF ３ (wherein, in the above composition formula, A represents one or more of the above-mentioned alkali metals, and B represents one or more of the above-mentioned alkaline earth metals). ３ AlF ６ For example, Li３ AlF ６ , Li ２ NaAlF ６ , Li ２ KAlF ６ , Na ３ AlF ６ , Na ２ LiAlF ６ , Na ２ KAlF ６ , K. ３ AlF ６ , K. ２ LiAlF ６ and K. ２ NaAlF ６ ABF ３ For example, LiMgF ３ , NaMgF ３ , KMgF ３ , LiCaF ３ , NaCaF ３ and KCaF ３ The complex fluoride may contain at least one selected from the group consisting of: ３ AlF ６ , K. ２ NaAlF ６ and NaMgF ３ The compound may contain at least one selected from the group consisting of: ３ AlF ６ and K. ２ NaAlF ６ is a cryolite crystal structure, NaMgF ３ has a perovskite crystal structure and is a material with small refractive index anisotropy due to crystal orientation, and is therefore preferable from the viewpoint of infrared transmission.

[0016] The complex fluoride may contain fluorine, an alkali metal, and aluminum as main components. The term "main component" as used herein means that the total content of fluorine, alkali metal, and aluminum contained in the complex fluoride is 80% or more in molar ratio. The total content may be 85% or more, 90% or more, 95% or more, or even 100%. The complex fluoride may be, for example, sodium hexafluoroaluminate (Na ３AlF ６ ) may be included. ３ AlF ６ is also known as a component of cryolite. ３ AlF ６ The anisotropy of the refractive index of is small, so it has excellent infrared light transmittance.

[0017] The complex fluoride may have some of its constituent anions substituted with hydroxide ions or oxide ions. For example, in the case of complex fluoride particles synthesized in a liquid phase, some of the complex fluoride ions may be substituted with at least one of hydroxide ions and oxide ions. When the complex fluoride has hydroxyl groups, the hydroxyl groups absorb infrared light of a specific wavelength. Therefore, when the structure 1 is used as, for example, a sensor, the sensor sensitivity can be improved by cutting unnecessary wavelengths. Furthermore, when the structure 1 contains hydroxyl groups, the transmittance fluctuation due to humidity is reduced, and the sensor becomes less susceptible to the influence of humidity.

[0018] The structure 1 contains 85% by mass or more of an inorganic substance. Therefore, compared to when a resin is used, the structure 1 is less likely to deteriorate over time and has high infrared transmittance. The inorganic substance contains the above-mentioned complex fluoride. The structure 1 may also contain 90% by mass or more of the inorganic substance, or may contain 95% by mass or more. The structure 1 may also contain 100% by mass or less of the inorganic substance.

[0019] The complex fluoride is a polycrystalline body. The polycrystalline body of the complex fluoride is excellent in terms of gas barrier properties or durability. The structure 1 may contain 50 mass% or more of a polycrystalline body of the complex fluoride. In this case, the obtained structure 1 is a structure that can easily utilize the properties of the complex fluoride. By containing 50 mass% or more of the complex fluoride, the structure has higher moisture resistance than alkali metal fluorides. Furthermore, a high mass proportion of the complex fluoride reduces the proportion of parts with different refractive indexes in the structure 1, thereby suppressing light scattering and increasing the infrared transmittance of the structure 1. In the structure 1, the mass proportion of the complex fluoride may be 60% or more, 70% or more, 80% or more, 90% or more, or even 95% or more.

[0020] As shown in Fig. 2, the base material 10 may include a continuous phase 11 and a plurality of complex fluoride particles 12. The continuous phase 11 may be present between adjacent complex fluoride particles 12. The continuous phase 11 may bond each of the plurality of complex fluoride particles 12. The continuous phase 11 may be in direct contact with the complex fluoride particles 12. Furthermore, the continuous phase 11 may cover at least a portion of the surface of each of the plurality of complex fluoride particles 12, or may cover the entire surface of each of the plurality of complex fluoride particles 12. The plurality of complex fluoride particles 12 may be bonded to each other. The complex fluoride particles 12 may be in point contact with each other, or may be in surface contact in which the surfaces of the complex fluoride particles 12 are in contact with each other.

[0021] The complex fluoride particles 12 may be composed of the same substance as the complex fluoride constituting the continuous phase 11 as described above. The inorganic substance constituting the complex fluoride particles 12 may be crystalline or amorphous. From the viewpoint of gas barrier properties or durability, the inorganic substance constituting the complex fluoride particles 12 is preferably crystalline. From the viewpoint of light transmittance, the inorganic substance constituting the complex fluoride particles 12 is preferably amorphous. When the inorganic substance is crystalline, the complex fluoride particles 12 may be monocrystalline or polycrystalline.

[0022] The average particle diameter of the multiple complex fluoride particles 12 is preferably 10 nm or more and 50 μm or less. When the average particle diameter of the complex fluoride particles 12 is 50 μm or less, the light transmittance of the structure 1 is high. Furthermore, when the average particle diameter of the complex fluoride particles 12 is within this range, the complex fluoride particles 12 are firmly bonded to each other, thereby increasing the strength of the structure 1. Furthermore, when the average particle diameter of the complex fluoride particles 12 is within this range, the proportion of pores present inside the structure 1 is 30% or less, as will be described later. Furthermore, the size of pores generated between the complex fluoride particles 12 is reduced. Therefore, the strength of the structure 1 can be increased. From the viewpoint of improving the light transmittance of the structure 1, the average particle diameter of the multiple complex fluoride particles 12 is more preferably 10 μm or less, even more preferably 2 μm or less, particularly preferably 1 μm or less, and most preferably 500 nm or less. The average particle diameter of the multiple complex fluoride particles 12 may be, for example, 1 nm or more, or 10 nm or more. In this specification, the value of "average particle diameter" is, unless otherwise specified, a value calculated as the average value of particle diameters of particles observed in several to several tens of fields of view using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0023] The structure 1 may contain impurities generated during the manufacturing process. The impurities may be, for example, raw materials for generating a complex fluoride and may contain elements constituting the complex fluoride. The elements contained in the impurities may include, for example, at least one element selected from the group consisting of fluorine, alkali metals, and the additional metals described above. The impurities may include a chalcogen compound including an oxide composed of one type of metal element, a halide, a hydroxide, a nitride, or a carbide. The impurities may be crystalline or amorphous.

[0024] The refractive index difference between the complex fluoride and the impurity may be 0.1 or less. When the refractive index difference is 0.1 or less, light scattering can be suppressed to form a structure with high transmittance. The lower limit of the refractive index difference is not particularly limited. The refractive index difference may be 0.08 or less, or may be 0.04 or less.

[0025] The structure 1 may contain an organic material such as resin particles. As will be described later, the structure 1 can be obtained by applying pressure while heating to 100 to 300°C, and therefore a material with low heat resistance can be added to the structure 1. Furthermore, the structure 1 is not limited to a material with low heat resistance such as an organic material, and may contain an inorganic compound other than the complex fluoride and impurities in order to impart functionality.

[0026] The porosity in the cross section of the structure 1 is 30% or less. That is, the porosity of pores exceeding 0 nm in the cross section of the structure 1 is 30% or less. Specifically, when the cross section of the structure 1 is observed, the average ratio of pores per unit area is 30% or less. When the porosity is 30% or less, the number of pores inside the matrix portion is reduced, resulting in a solidified body with high strength. The porosity in the cross section of the structure 1 is preferably 20% or less, more preferably 10% or less, and even more preferably 5% or less. The smaller the porosity in the cross section of the structure 1, the more cracks originating from the pores are suppressed, thereby enabling the strength of the structure 1 to be increased. Furthermore, the smaller the porosity in the cross section of the structure 1, the more light scattering due to the pores is suppressed, thereby enabling the transmittance of the structure 1 to be increased.

[0027] In this specification, the porosity can be determined as follows. First, the cross section of the structure 1 is observed to distinguish between pores and non-pore areas. Then, the area of ​​the pores in a unit area is measured to determine the proportion of pores per unit area. The porosity is defined as the average value of the proportions of pores per unit area determined at multiple locations. When observing the cross section of the structure 1, an optical microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM) can be used. Furthermore, the unit area and the area of ​​pores in the unit area may be measured by binarizing an image observed with a microscope.

[0028] The median pore diameter of the structure 1 is 500 nm or less. When the median pore diameter is 500 nm or less, light scattering by the pores is suppressed, resulting in a structure 1 with high transmittance. The median pore diameter is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 100 nm or less. In this specification, the median pore diameter means the pore diameter when the cumulative value of the pore size distribution on an area basis is 50%. The pore diameter means the diameter of a perfect circle when the shape of the pores in the cross section of the structure 1 is assumed to be a perfect circle.

[0029] In the cross section of the structure 1, the area ratio of pores having a pore diameter exceeding 500 nm is preferably 1% or less per unit area. In such a case, light scattering by the pores is suppressed, resulting in a structure having even higher transmittance. The area ratio is more preferably 0.5% or less, even more preferably 0.1% or less, and particularly preferably 0.0%. Note that the area ratio of 0.0% means that no pores having a median pore diameter exceeding 500 nm are observed per unit area.

[0030] The structure 1 has infrared light transparency. In the target wavelength band, the linear transmittance of the structure 1 may have a wavelength bandwidth equal to or greater than a predetermined value. The linear transmittance of the structure 1 can be obtained by measurement by transmission using an FT-IR (Fourier transform infrared spectroscopy) device. The linear transmittance of the infrared transmission spectrum is converted based on the Beer-Lambert law so as to be the linear transmittance at a thickness of 1 mm. The wavelength bandwidth can be obtained by measuring the wavelength bandwidth in the target wavelength band where the linear transmittance is equal to or greater than a predetermined value. The wavelength bandwidth may be the wavelength bandwidth in which the linear transmittance is continuously equal to or greater than a predetermined value, or may be the total wavelength bandwidth of the wavelength bandwidths in which the linear transmittance is continuously and intermittently equal to or greater than a predetermined value. In other words, the wavelength bandwidth is the total wavelength bandwidth in the target wavelength band where the linear transmittance is equal to or greater than a predetermined value. Therefore, when the linear transmittance is intermittently equal to or greater than a predetermined value, the wavelength bands in which the linear transmittance is equal to or greater than a predetermined value may be separated from each other in the target wavelength band. It is preferable that the wavelength bandwidth be the wavelength bandwidth in which the linear transmittance is continuously equal to or greater than a predetermined value.

[0031] In the target wavelength band of 3 μm or more and 10 μm or less, the wavelength bandwidth in which the linear transmittance per mm of thickness of the structure 1 continuously exceeds 10% may be 0.1 μm or more. Such a structure 1 can be expected to be used as an infrared transmitting optical filter. The target wavelength band may be 8 μm or less, or 6 μm or less. The wavelength bandwidth in which the linear transmittance exceeds 10% may be 0.5 μm or more, 1 μm or more, 1.5 μm or more, or 2 μm or more. The wavelength bandwidth in which the linear transmittance exceeds 10% may be 3 μm or less. The linear transmittance in the above wavelength bandwidth may exceed 20%, 30%, 40%, 50%, or 60%. For example, in the target wavelength band of 3 μm or more and 5 μm or less, the wavelength bandwidth in which the linear transmittance continuously exceeds 50% may be 0.1 μm or more. The upper limit of the linear transmittance in the above wavelength bandwidth is not particularly limited and may be, for example, 100%.

[0032] At a wavelength of 4 μm, the linear transmittance per mm of thickness of the structure 1 may be greater than 20%, 30%, 40%, 50%, or 60%. Within a wavelength range of 3.8 μm to 4.4 μm, the average linear transmittance per mm of thickness of the structure 1 may be 60% or more, or may be 65% or more.

[0033] At wavelengths of 3.8 to 4.4 μm, the average linear transmittance per mm of thickness of the structure 1 may exceed 20%, 30%, 40%, 50%, or 60%. Over the entire wavelength range of 3.8 to 4.4 μm, the average linear transmittance per mm of thickness of the structure 1 may exceed 20%, 30%, 40%, 50%, or 60%.

[0034] The weight loss rate when the structure 1 is heated from 200°C to 500°C may be 0.5% or less. Such a structure 1 has a small amount of internal hydroxyl groups and water molecules, and infrared absorption and scattering by hydroxyl groups and water molecules can be suppressed. Therefore, infrared transmittance can be further increased. The weight loss rate may be 0.4 or less, or may be 0.3 or less. The weight loss rate may also be 0% or more.

[0035] The weight loss rate can be measured by thermogravimetry (TG) in accordance with JIS K7120-1987. The weight loss rate when heated from 200°C to 500°C can be calculated by the following formula (1).

[0036] Weight reduction rate (%) = (((mass of complex fluoride particles at 200°C) - (mass of complex fluoride particles at 500°C)) / (mass of complex fluoride particles at 200°C)) × 100 (1)

[0037] The structure 1 may be an infrared transmission filter. By using the structure 1 as an infrared transmission filter, it is possible to provide an infrared detection device, a light emitting device, or the like that can suppress diffuse reflection of infrared light by pores. When the structure 1 is capable of transmitting light in a specific infrared region as a single layer, it is possible to transmit the specific infrared light without stacking multiple dielectrics as in, for example, an interference filter, or providing a separate light-shielding filter to improve sensor sensitivity.

[0038] The thickness t of the structure 1 is 10 μm or more. The structure 1 of this embodiment is formed by a pressure and heat method, as described below. Therefore, a bulk body having a thickness of 10 μm or more can be easily formed without forming the structure 1 by stacking thin films. The thickness of the structure 1 may be 100 μm or more, 500 μm or more, 1 mm or more, or 1 cm or more. The upper limit of the thickness of the structure 1 is not particularly limited, but may be, for example, 50 cm.

[0039] When the structure 1 is used as an infrared transmission filter, its shape is not particularly limited. It may be flat, concave, or convex. When a lens shape is imparted, it becomes possible to allow light rays to be incident perpendicularly on the dielectric laminated bandpass filter, thereby canceling the light incident angle dependence of the dielectric laminated bandpass filter. In addition, a microstructure having an anti-reflection function may be formed on the surface of the structure 1.

[0040] As described above, the structure 1 includes the base material 10 including the continuous phase 11 of the polycrystalline body of the alkali metal-containing complex fluoride. The structure 1 includes 85 mass % or more of an inorganic substance, 50 mass % or more of the polycrystalline body of the complex fluoride, a porosity of the structure 1 of 30% or less, a median pore diameter of the structure 1 of 500 nm or less, and a thickness of the structure 1 of 10 μm or more.

[0041] This structure makes the structure less soluble in water and allows it to be manufactured using a simple low-temperature process, making it suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0042] [Infrared Detector] Next, an infrared detector 100 according to this embodiment will be described with reference to Fig. 3. As shown in Fig. 3, the infrared detector 100 includes the above-described structure 1. The infrared detector 100 also includes an infrared detection element 110, an IC element 120, a substrate 130, and a metal case 150.

[0043] The infrared detection element 110 and the IC element 120 are mounted on a substrate 130 by a die bond material 131. The infrared detection element 110 and the IC element 120 are electrically connected to each other by wires 140. The infrared detection element 110 is also connected to electrical circuit wiring (not shown) of the substrate 130 by the wires 140.

[0044] The infrared detection element 110 receives infrared rays, converts the thermal energy of the received infrared rays into electrical energy, and outputs an electrical signal corresponding to the amount of the received infrared rays to the IC element 120. The infrared detection element 110 may be a thermal infrared detection element such as a pyroelectric element, a thermopile infrared detection element, or a bolometer infrared detection element, or a quantum infrared detection element.

[0045] The IC element 120 includes an amplifier circuit that amplifies the electrical signal output from the infrared detection element 110, and a determination circuit that determines that a flame is present when the electrical signal amplified by the amplifier circuit exceeds a threshold value.

[0046] The metal case 150 is attached to the substrate 130. The metal case 150 surrounds the periphery of the infrared detection element 110 and the IC element 120, and the infrared detection element 110 and the IC element 120 are sealed by the substrate 130 and the metal case 150. The metal case 150 includes a top wall 151 and a side wall 152. An opening is provided in the top wall 151, and the opening is covered by the structure 1. The structure 1 is disposed so as to face the infrared detection element 110, and the infrared detection element 110 is provided on the substrate 130 so as to receive infrared light that has passed through the structure 1. The side wall 152 connects the edge of the top wall 151 to the edge of the substrate 130.

[0047] Infrared rays emitted from a flame or the like pass through the structure 1 and are received by the infrared detection element 110. The infrared detection element 110 outputs an electrical signal corresponding to the amount of infrared rays received to the IC element 120. The IC element 120 determines whether a flame is present or not based on the electrical signal. In this way, the infrared detection device 100 can detect a flame by utilizing the infrared rays emitted from the flame.

[0048] In addition, SO２ , CO ２ , P.H. ３ , N ２ Gas molecules such as inorganic gases like O and NO have characteristic absorption properties in the mid-infrared region. Furthermore, these gas molecules emit corresponding infrared rays at high temperatures. Therefore, the structure 1 according to this embodiment can absorb CO ２ The structure 1 according to the present embodiment is useful as an infrared-transmitting window, because it has a high transmittance of infrared light.

[0049] In this embodiment, an example has been described in which the infrared detection device 100 is used as a flame sensor for detecting flames, but the use of the infrared detection device 100 is not limited to this form. The infrared detection device 100 can also be used as a human presence sensor, a biological sensor, a security sensor, a gas sensor, a non-contact thermometer, a solid-state imaging device, a camera module, or the like.

[0050] [Light-emitting device] Next, a light-emitting device 200 according to this embodiment will be described with reference to Fig. 4. As shown in Fig. 4, the light-emitting device 200 includes the above-described structure 1. The light-emitting device 200 also includes a light source 210 that irradiates the structure 1 with light including infrared rays. The light source 210 may include an LED, a xenon lamp, a laser diode, or a combination thereof.

[0051] Since the light-emitting device 200 includes the structure 1, the structure 1 can cut a portion of the infrared light emitted from the light source 210. Therefore, the light-emitting device 200 according to this embodiment can emit light having a specific wavelength. The light-emitting device 200 can be used, for example, as a light-emitting device for gas detection, a light-emitting device for inspection, a light-emitting device for a surveillance camera, a light-emitting device for hair removal, a light-emitting device for curing infrared-curable resins, and the like.

[0052] [Method for Producing Structure] (First Embodiment) Next, a method for producing the structure 1 according to the first embodiment will be described. The structure 1 can be produced by pressurizing and heating a raw material containing complex fluoride particles. By using such a pressurizing and heating method, the complex fluoride particles bond to each other while deforming, so that the structure 1 having a low porosity can be formed. The raw material containing fluoride particles may include a step of generating a plurality of complex fluoride particles, a separation step, a heating step, and a hydration step.

[0053] Specifically, in the step of producing a plurality of complex fluoride particles, complex fluoride particles are prepared by first mixing and reacting a first metal compound, which is an alkali metal fluoride, with a second metal compound other than fluoride. The method for mixing the alkali metal fluoride and the second metal compound is not particularly limited, and either dry mixing or wet mixing may be used. The solutions may be mixed by adding a second metal compound solution to an alkali metal fluoride solution, or by adding an alkali metal fluoride solution to a second metal compound solution. Furthermore, equal amounts of the two liquids may be mixed simultaneously using a microchannel or the like. For example, water may be used as the solvent.

[0054] The concentration of the alkali metal fluoride and the second metal compound when mixed can be adjusted appropriately. The concentration of the alkali metal fluoride may be 100 mM or more, or may be 200 mM or more. The concentration of the alkali metal fluoride may be 1000 mM or less. The concentration of the second metal compound may be 20 mM or more, or may be 40 mM or more. The concentration of the second metal compound may be 200 mM or less. The higher the concentration of these raw materials, the smaller the particle size tends to be, and therefore the permeability of the structure 1 can be improved.

[0055] Examples of alkali metals contained in the alkali metal fluoride include lithium, sodium, potassium, rubidium, and cesium. Specifically, the alkali metal fluoride may contain at least one alkali metal selected from the group consisting of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, and cesium fluoride.

[0056] The second metal compound may contain at least one metal salt selected from the group consisting of metal chlorides, metal nitrates, metal sulfates, and metal organic acid salts, excluding metal fluorides. The metal contained in the second metal compound may be at least one metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. The second metal compound may contain, for example, aluminum chloride.

[0057] In the separation step, the generated multiple complex fluoride particles are separated. When the second metal compound is a metal chloride, metal nitrate, metal sulfate, or metal organic acid salt, when the alkali metal fluoride and the second metal compound are mixed, in addition to the complex fluoride, alkali metal chloride, nitrate, sulfate, or metal organic acid salt is generated as a by-product. Therefore, a washing operation to remove the by-product may be performed. The alkali metal compound may be removed by washing with a solvent such as water during filtration or centrifugation, for example.

[0058] In the heating step, the separated multiple complex fluoride particles are heated at 200°C or higher. By setting the heating temperature to 200°C or higher, the water content inside the complex fluoride particles is reduced. As a result, the absorption of infrared light by hydroxyl groups and water inside the structure 1 is reduced, and the transmittance of the structure 1 can be increased. The heating temperature of the complex fluoride particles may be 300°C or higher, 350°C or higher, 400°C or higher, 450°C or higher, or 500°C or higher. The heating temperature of the complex fluoride particles may be 900°C or lower, 800°C or lower, 700°C or lower, 600°C or lower, or 550°C or lower. The heating time of the complex fluoride particles may be 0.5 hours or longer, 1 hour or longer, or 1.5 hours or longer. The heating time of the complex fluoride particles may be 24 hours or shorter, 12 hours or shorter, 6 hours or shorter, or 3 hours or shorter.

[0059] In the method for producing a complex fluoride powder, by-products may be removed as necessary to separate the complex fluoride particles, followed by drying. The drying temperature is not particularly limited, but can be a temperature below the melting point of the complex fluoride. The drying temperature may be, for example, 40°C or higher, 80°C or higher, 100°C or higher, or 200°C or higher. The drying temperature may be, for example, 600°C or lower, 400°C or lower, 300°C or lower, or 200°C or lower. The drying time for the complex fluoride particles may be 0.5 hours or more, 1 hour or more, or 1.5 hours or more. The drying time for the complex fluoride particles may be 24 hours or less, 12 hours or less, 6 hours or less, or 3 hours or less.

[0060] The raw material may contain water of hydration in addition to the complex fluoride. The raw material may also contain by-products such as simple fluorides, oxides, and hydroxides containing a single metal element as unavoidable impurities.

[0061] Next, the raw material containing the complex fluoride particles is filled into the interior of the mold. After the raw material is filled into the mold, the mold may be heated as needed. Then, pressure is applied to the raw material inside the mold, creating a high-pressure state inside the mold. At this time, the complex fluoride particles are densified and simultaneously bonded to each other.

[0062] The heating and pressurizing conditions are not particularly limited as long as they are conditions that promote densification of the complex fluoride particles. For example, it is preferable to heat the raw material to 50 to 300°C and then pressurize it at a pressure of 10 to 600 MPa. The temperature at which the raw material is heated is more preferably 80 to 250°C, and even more preferably 100 to 200°C. The pressure at which the raw material is pressed is more preferably 50 to 600 MPa.

[0063] Then, the molded body is removed from the mold to obtain Structure 1. It is believed that by applying pressure to a raw material containing complex fluoride particles containing at least one of hydroxyl groups and water molecules while heating, the complex fluoride particles react with each other via the hydroxyl groups or water molecules to form a continuous phase 11 of a polycrystalline body of a complex fluoride containing an alkali metal. This allows the above-mentioned Structure 1 to be formed.

[0064] The above-described reaction by pressure and heat can produce a structure 1 having a dense structure. Another possible method for forming an aggregate of inorganic particles is to press only inorganic particle powder to form a green compact, and then sinter it at a high temperature (e.g., 1700°C or higher). However, even if the green compact of inorganic particles is sintered at a high temperature, the resulting structure 1 contains many pores, resulting in insufficient mechanical strength and insufficient transmittance due to light scattering. Furthermore, sintering inorganic particles at a high temperature requires precise temperature control, which increases manufacturing costs.

[0065] In contrast, in the manufacturing method of this embodiment, a raw material containing complex fluoride particles containing at least one of hydroxyl groups and water molecules is pressurized while being heated, so that a dense structure 1 having excellent transmittance can be obtained. Furthermore, since the manufacturing method of this embodiment can be obtained by applying pressure while being heated at 50°C to 300°C, precise temperature control is not required, and it is possible to reduce manufacturing costs.

[0066] As described above, the method for producing the structure 1 of this embodiment includes a step of pressurizing and heating a raw material containing a complex fluoride. According to the method for producing the structure 1 of this embodiment, the above-described structure 1 can be produced by a simple low-temperature process.

[0067] Second Embodiment Next, a method for producing the structure 1 according to a second embodiment will be described. The structure 1 can also be produced by pressurizing and heating a raw material containing first fluoride particles containing an alkali metal and second fluoride particles containing a metal different from the alkali metal. By using such a pressurizing and heating method, the fluoride particles bond to each other while forming a complex fluoride, so that the structure 1 can be formed with low porosity.

[0068] The first fluoride particles contain an alkali metal. Examples of the alkali metal contained in the first fluoride particles include lithium, sodium, potassium, rubidium, and cesium. Specifically, the first fluoride particles may contain at least one metal fluoride selected from the group consisting of lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, and cesium fluoride.

[0069] The second fluoride particles contain a metal element other than an alkali metal. The metal element other than an alkali metal is not particularly limited, but may be at least one selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. Specifically, the metal element other than an alkali metal may contain at least one metal selected from the group consisting of magnesium, calcium, strontium, barium, aluminum, gallium, indium, zinc, and yttrium. The second fluoride particles are magnesium fluoride (MgF ２ ), calcium fluoride (CaF ２ ), strontium fluoride (SrF ２ ), barium fluoride (BaF ２ ), aluminum fluoride (AlF ３ ), gallium fluoride (GaF ３ ), indium fluoride (InF ３ ), yttrium fluoride (YF ３ ), zinc fluoride (ZnF ２ ) may contain at least one metal fluoride selected from the group consisting of

[0070] Next, a solvent is added to the raw material containing the first fluoride particles and the second fluoride particles. The solvent is not particularly limited, but for example, a solvent that can dissolve a portion of the first fluoride particles and the second fluoride particles when the raw material is pressurized and heated can be used. For example, water can be used as such a solvent.

[0071] The raw material containing the first fluoride particles and the second fluoride particles can be pressurized and heated in the same manner as in the above embodiment to form the structure 1. The first fluoride particles and the second fluoride particles react in a solvent by pressurizing and heating to form a continuous phase 11 of a polycrystalline body of a complex fluoride containing an alkali metal. This allows the above-mentioned structure 1 to be formed.

[0072] As described above, the method for producing the structure 1 according to this embodiment includes a step of pressurizing and heating a raw material containing a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal, and water. According to the method for producing the structure 1 according to this embodiment, the above-described structure 1 can be produced by a simple low-temperature process.

[0073] Third Embodiment Next, a description will be given of a method for producing the structure 1 according to a third embodiment. The structure 1 can also be produced by pressurizing and heating a raw material containing the complex fluoride particles obtained by the method for producing the structure 1 according to the first embodiment and the first fluoride particles and second fluoride particles described in the second embodiment.

[0074] Specifically, first, the raw material is prepared by mixing the complex fluoride particles with the first fluoride particles and the second fluoride particles. The method for mixing these particles is not particularly limited, and may be dry mixing or wet mixing. When a solvent is added to the raw material, for example, water may be used as the solvent.

[0075] The raw material containing the first fluoride particles and the second fluoride particles can be pressurized and heated to form the structure 1, as in the above embodiment. The first fluoride particles and the second fluoride particles react in a solvent by pressurizing and heating, and bond to each other while forming a complex fluoride. Furthermore, the complex fluoride particles bond to each other while deforming. This allows the above-mentioned structure 1 to be formed.

[0076] As described above, the method for producing the structure 1 according to this embodiment includes a step of pressurizing and heating raw materials containing at least one of a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal, water, and a complex fluoride. According to the method for producing the structure 1 according to this embodiment, the above-mentioned structure 1 can be produced by a simple low-temperature process.

[0077] That is, as explained in the first to third embodiments, the method for producing structure 1 includes a step of pressurizing and heating raw materials containing at least one of a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal and water, and a complex fluoride containing at least one of a hydroxyl group and a water molecule under conditions of a pressure of 10 to 600 MPa and a temperature of 50 to 300°C. Structure 1 contains 85% by mass or more of an inorganic substance, structure 1 contains 50% by mass or more of a polycrystalline body of the complex fluoride, structure 1 has a porosity of 30% or less, structure 1 has a median pore diameter of 500 nm or less, and structure 1 has a thickness of 10 μm or more. According to the method for producing structure 1 according to these embodiments, the above-mentioned structure 1 can be produced by a simple low-temperature process.

[0078] Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present embodiment is not limited to these examples.

[0079] (Example 1) First, sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and aluminum fluoride (AlF ３Next, sodium fluoride powder and aluminum fluoride powder were mixed in a pot mill so that the molar ratio was 3:1, and then 20 wt % of ion-exchanged water relative to the total powder amount was added and mixed using an agate mortar and agate pestle, to obtain a mixed powder.

[0080] Next, the mixed powder was placed in a cylindrical molding die (Φ12) having an internal space. The mixed powder was heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, a cylindrical test sample of this example was obtained.

[0081] (Example 2) First, sodium hexafluoroaluminate (Na ３ AlF ６ Specifically, 32 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 4 mmol of aluminum chloride (AlCl ３ ・6H ２ O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 100 mL of H ２ The mixture was mixed with NaO and stirred at 25°C for 1 hour. The stirred solution was suction filtered using a membrane filter with a pore size of 0.1 µm, and the residue was dried at -60 to -100 kPa and 80°C for 2 hours to obtain a single-phase Na ３ AlF ６ A powder was obtained.

[0082] Sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and aluminum fluoride (AlF ３ ) powder (High Purity Chemical Laboratory) was prepared. Next, sodium fluoride powder, aluminum fluoride powder, and Na ３ AlF ６ The powders were mixed in an agate mortar and agate pestle with 20% by weight of ion-exchanged water added to the total powder amount so that the molar ratio was 3:1:9, to obtain a mixed powder.

[0083] Next, the mixed powder was placed in a cylindrical molding die (Φ12) having an internal space. The mixed powder was heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, a cylindrical test sample of this example was obtained.

[0084] (Example 3) First, sodium hexafluoroaluminate (Na ３ AlF ６ Specifically, 32 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 4 mmol of aluminum chloride (AlCl ３ ・6H ２ O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 100 mL of H ２ The mixture was mixed with NaO and stirred at 25°C for 1 hour. The stirred solution was suction filtered using a membrane filter with a pore size of 0.1 µm, and the residue was dried at -60 to -100 kPa and 80°C for 2 hours to obtain a single-phase Na ３ AlF ６ The powder obtained was Na ３ AlF ６ An SEM image of the powder is shown in FIG.

[0085] Next, Na ３ AlF ６ The powder was then added. ３ AlF ６ The powder was heated and pressed at 180° C. under 400 MPa for 20 minutes, thereby obtaining a cylindrical test sample of this example.

[0086] (Example 4) First, K ２ NaAlF ６ Specifically, 32 mmol of potassium fluoride (KF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), 6 mmol of sodium chloride (NaCl) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent), and 2 mmol of aluminum chloride (AlCl ３ ・6H ２ O) and 20 mL of H ２The mixture was mixed with 0 and stirred at 25°C for 1 hour. The stirred solution was suction filtered using a membrane filter with a pore size of 0.1 µm, and the residue was dried at -60 to -100 kPa and 80°C for 2 hours to obtain a single-phase K ２ NaAlF ６ Powder was obtained. ２ NaAlF ６ An SEM image of the powder is shown in FIG.

[0087] Next, K ２ NaAlF ６ The powder was added. ２ NaAlF ６ The powder was heated and pressed at 180° C. under 400 MPa for 20 minutes, thereby obtaining a cylindrical test sample of this example.

[0088] (Example 5) First, NaMgF ３ Specifically, 48 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 12 mmol of magnesium chloride (MgCl ２ ・6H ２ O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 100 mL of H ２ The mixture was mixed with NaMgF and stirred at 80°C for 3 hours. The stirred solution was suction filtered using a membrane filter with a pore size of 0.1 µm, and the residue was dried at -60 to -100 kPa and 80°C for 2 hours to obtain a single-phase NaMgF ３ The powder obtained was NaMgF ３ An SEM image of the powder is shown in FIG.

[0089] Next, NaMgF was placed inside a cylindrical molding die (Φ12) having an internal space. ３ The NaMgF powder was then added. ３ The powder was heated and pressed at 180° C. under 400 MPa for 20 minutes, thereby obtaining a cylindrical test sample of this example.

[0090] Comparative Example 1 The test sample obtained in Example 1 was fired at 800° C. for 2 hours to obtain a test sample of this example.

[0091] Comparative Example 2 The test sample obtained in Example 3 was fired at 800° C. for 2 hours to obtain a test sample of this example.

[0092] [Evaluation of Test Samples] The test samples prepared as described above were subjected to crystal structure analysis, pore observation, and measurements of porosity, pore diameter, and in-line transmittance.

[0093] (Crystal Structure Analysis) Next, a powder X-ray diffraction (XRD) device was used to measure the powders obtained by pulverizing the test samples of Examples 1 to 5, and XRD patterns were obtained. These results are shown in Figures 8 to 12. The obtained XRD patterns were also subjected to Rietveld analysis to determine the proportions of each component. These results are shown in Tables 1 and 2. In Tables 1 and 2, the units of the values ​​in the upper rows are mass%, and the units of the values ​​in parentheses in the lower rows are volume%.

[0094] (Observation of Pores) First, the cross section of each test sample was subjected to cross-section polishing (CP processing). Next, using a scanning electron microscope (SEM), secondary electron images and backscattered electron images of the cross section of the test sample were observed at a magnification of 10,000 times or 2,000 times. The secondary electron images and backscattered electron images of Examples 1 to 5 and Comparative Examples 1 and 2 are shown in FIGS. 13 to 30.

[0095] (Measurement of porosity and pore diameter) Next, the backscattered electron image obtained as described above was binarized to clarify the pore portions. The porosity was then obtained by calculating the area ratio of the pore portions from the binarized image. The porosity was determined for pores with pore diameters of 0 nm or more, 200 nm or more, 300 nm or more, and 500 nm or more. The results are shown in Table 3. The pore diameter was determined when the cumulative value of the pore diameter distribution on an area basis was 10% (d １０ ), 50% (d ５０ ) and 90% (d ９０ The results of these calculations are shown in Table 4.

[0096] (Linear transmittance) Each test sample was measured by a transmission method using an FT-IR device to obtain an infrared transmission spectrum. These results are shown in Figures 31 to 33. The linear transmittance of the infrared transmission spectrum was converted based on the Beer-Lambert law so as to be the linear transmittance at a thickness of 1 mm.

[0097]

[0098]

[0099]

[0100]

[0101] As shown in Table 1, the test sample of Example 1 contained NaF and AlF, which are the same components as the raw materials. ３ and Na produced by the hydrothermal reaction ３ AlF ６ In Example 1, the raw material contained particulate NaF and AlF ３ On the other hand, the test sample of Example 2 contains Na ３ AlF ６ In addition, a small amount of Na ５ Al ３ F １４ was found to contain.

[0102] As shown in Table 2, the test sample of Example 3 contained Na ３ AlF ６ In addition, a small amount of Na ５ Al ３ F １４ It was found that the sample of Example 4 contained the same K as the raw material. ２ NaAlF ６ The sample of Example 5 also contained 100 mass % of NaMgF, the same as the raw material. ３ was contained at 100% by mass.

[0103] As shown in Table 3, the porosity of pores exceeding 500 nm was 0.27% in Example 1 and 0.00% in Examples 2 to 5. On the other hand, the porosity of pores exceeding 500 nm was 3.59% in Comparative Example 1 and 6.11% in Comparative Example 2. Furthermore, as shown in Table 4, the median pore diameter (d ５０ ) was very small compared to Comparative Example 1 and Comparative Example 2.

[0104] As shown in Figure 31, the linear transmittance continuously exceeded 10% in the range of 4.30 μm to 5.80 μm (wavelength bandwidth 1.5 μm) in Example 1 and in the range of 3.62 μm to 5.96 μm (wavelength bandwidth 2.34 μm) in Example 2. Also, as shown in Figure 32, the linear transmittance continuously exceeded 10% in the range of 3.50 μm to 5.88 μm (wavelength bandwidth 2.38 μm) in Example 3, in the range of 3.74 μm to 5.62 μm (wavelength bandwidth 1.88 μm) in Example 4, and in the range of 3.78 μm to 5.62 μm (wavelength bandwidth 1.84 μm) in Example 5. On the other hand, as shown in Figure 33, the linear transmittance of Comparative Example 1 and Comparative Example 2 was less than 1% over the entire wavelength range of 3 μm or more and 10 μm or less.

[0105] These results show that the test samples of Examples 1 to 5 have higher in-line transmittance than the test samples of Comparative Examples 1 and 2. This is thought to be because the test samples of Examples 1 to 5 had median pore diameters of the structures of 500 nm or less, and light scattering due to coarse pores was low.

[0106] Furthermore, the test sample of Example 2 had a higher infrared transmittance than the test sample of Example 1. This may be partly because the test sample of Example 2 contained a smaller proportion of remaining unreacted raw materials.

[0107] Next, test samples were prepared by molding under pressure and heat, and test samples were prepared by pressing and firing, as follows.

[0108] Example 6 A cylindrical test sample of this example was obtained by the same process as in Example 3.

[0109] Example 7 A cylindrical test sample of this example was obtained by the same process as in Example 1.

[0110] (Comparative Example 3) Na synthesized in Example 6 ３ AlF ６ The powder was placed inside a molding die. ３ AlF ６ The powder was pressed at room temperature (25° C.) under 50 MPa, and the cylindrical green compact thus obtained was fired at 800° C. for 2 hours.

[0111] Comparative Example 4 The mixed powder prepared in Example 7 was placed in a molding die. The mixed powder was then compressed at room temperature (25°C) and 50 MPa. The cylindrical green compact thus obtained was fired at 800°C for 2 hours.

[0112] (Structural Observation) The fractured surfaces of the test samples according to Examples 6 and 7 and Comparative Examples 3 and 4 were observed using a scanning electron microscope (SEM) at a magnification of 10,000 or 2,000 times. These secondary electron images are shown in Figures 34 to 41. The surfaces of the test samples to be observed were subjected to gold sputtering.

[0113] The pores of the test sample of Comparative Example 3 were larger than the pores of the test sample of Example 6. Similarly, the pores of the test sample of Comparative Example 4 were larger than the pores of the test sample of Example 7. These results show that the test sample molded under pressure and heat is denser than the test sample molded under pressure and sintered.

[0114] Next, Na ３ AlF ６ In order to confirm the effect of heat treatment on powder, structures according to the following examples were fabricated.

[0115] Example 8 A cylindrical test sample of this example was obtained by the same process as in Example 3.

[0116] (Example 9) First, sodium hexafluoroaluminate (Na ３ AlF ６Specifically, 24 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 3 mmol of aluminum chloride (AlCl ３ ・6H ２ O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 100 mL of H ２ The mixture was mixed with NaO and stirred at 28°C for 20 hours. The stirred solution was suction filtered using a membrane filter with a pore size of 0.1 μm, and the residue was dried at −60 to −100 kPa and 80°C for 2 hours. The resulting powder was then crushed in a mortar and heat-treated in air at 300°C for 2 hours to obtain Na. ３ AlF ６ A powder was obtained.

[0117] Heat-treated Na ３ AlF ６ 10% by mass of water based on the powder ３ AlF ６ Next, the hydrated Na was added to the inside of a cylindrical molding die (Φ12) having an internal space. ３ AlF ６ The hydrated Na powder was then added. ３ AlF ６ The powder was heated and pressed at 180° C. under 400 MPa for 20 minutes, thereby obtaining a cylindrical test sample of this example.

[0118] Example 10 A test sample was prepared in the same manner as in Example 9, except that the heat treatment temperature was changed from 300°C to 400°C.

[0119] Example 11 A test sample was prepared in the same manner as in Example 9, except that the heat treatment temperature was changed from 300°C to 500°C.

[0120] [Evaluation] (Na ３ AlF ６ SEM image of powder) The Na powder obtained by the synthesis of Examples 8 to 11 after 2 hours of heat treatment was observed by scanning electron microscope (SEM). ３ AlF ６ The powder was observed, and the SEM images are shown in Figures 42 to 45.

[0121] (Crystal structure analysis) Using a powder X-ray diffraction (XRD) device, the Na obtained in each example after 2 hours of heat treatment was analyzed. ３ AlF ６ XRD patterns were obtained for the powders and the results are shown in Figure 46.

[0122] (Observation of Pores) As in the above, secondary electron images and backscattered electron images were observed for the cross sections of the test samples at a magnification of 10,000 times using a scanning electron microscope (SEM). The secondary electron image and backscattered electron image of Example 9 are shown in Figures 47 and 48. The secondary electron image and backscattered electron image of Example 10 are shown in Figures 49 and 50. The secondary electron image and backscattered electron image of Example 11 are shown in Figures 51 and 52.

[0123] (Measurement of porosity and pore diameter) In the same manner as above, the porosity was measured from the obtained backscattered electron image. The porosity was determined for pores with a pore diameter of 5 nm or more. The results are shown in Table 5. The pore diameter was determined when the cumulative value of the pore diameter distribution on an area basis was 10% (d １０ ), 50% (d ５０ ) and 90% (d ９０ The results of these calculations are shown in Table 5.

[0124] (Relative Density) First, the volume and mass of the structure were measured, and the apparent density of the structure was calculated. Next, the apparent density of the test sample was calculated using the density of cryolite (2.98 g / cm ３ The relative density of the structure was calculated by dividing the density by the mass of the structure.

[0125] (Linear transmittance) Each test sample was measured by a transmission method using an FT-IR device to obtain an infrared transmission spectrum. These results are shown in Figures 53 to 55. The linear transmittance of the infrared transmission spectrum was converted based on the Beer-Lambert law so that it becomes the linear transmittance at a thickness of 1 mm.

[0126] (Weight Loss Rate) The weight loss rate of the structure was measured using a thermogravimetry (TG) device. Specifically, 15 to 20 mg of test sample was placed in an aluminum container and heated from 30°C to 560°C at 10°C / min with dry air flowing in at 20 mL / min. Then, a first weight loss rate from 30°C to 200°C and a second weight loss rate from 200°C to 500°C were calculated. Specifically, the first weight loss rate from 30°C to 200°C was calculated by dividing the weight of the sample at 200°C by the weight of the sample at 30°C. Similarly, the second weight loss rate from 200°C to 500°C was calculated by dividing the weight of the sample at 500°C by the weight of the sample at 200°C. These results are shown in Table 6, Figures 56 and 57.

[0127]

[0128]

[0129] As shown in FIG. 46, when the heat treatment temperature is 300° C. to 500° C., the heterogeneous phase (Na ５ Al ３ F １４ However, in all cases, the main phase was Na ３ AlF ６ and the structure is Na ３ AlF ６ It was confirmed that the polycrystalline material contained at least 95 mass % of the above.

[0130] As shown in Table 5, the median pore diameter (d50) of Examples 8 to 11 was 500 nm or less, which was very small. The porosity of Examples 8 to 11 was 30% or less. Furthermore, as shown in FIG. 54, it was confirmed that all of the structures had a relative density of 70% or more and were dense. These results confirmed that the structures were dense.

[0131] As shown in FIG. 53 , the average linear transmittance per mm of the structure 1 according to Examples 9 to 11 exceeded 60% at wavelengths of 3.8 to 5.7 μm (wavelength bandwidth 1.9 μm). Furthermore, as shown in Table 6, FIGS. 53 and 55 , the test samples of Examples 9 to 11 had higher linear transmittance at wavelengths of around 4 μm compared to the test sample of Example 8, and it was found that the linear transmittance was maximized when the heat treatment temperature was 400°C. As shown in Table 6, FIGS. 56 and 57 , the second weight loss rate of Example 10 was 0.5% or less, less than half that of Example 8. From the results of FIGS. 53 , 56 and 57 , it is believed that the amount of hydroxyl groups and water molecules inside the structure was reduced by heat treatment, suppressing infrared absorption and scattering by the hydroxyl groups and water molecules, thereby improving the transmittance of the structure.

[0132] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0133] (Technology 1) A structure comprising a base material including a continuous phase of a polycrystalline body of a complex fluoride containing an alkali metal, the structure including 85% by mass or more of an inorganic substance, 50% by mass or more of the polycrystalline body of the complex fluoride, a porosity of the structure being 30% or less, a median pore diameter of the structure being 500 nm or less, and a thickness of the structure being 10 μm or more.

[0134] This structure makes the structure less soluble in water and allows it to be manufactured using a simple low-temperature process, making it suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0135] (Technology 2) The structure according to Technology 1, wherein the complex fluoride contains, as main components, fluorine, the alkali metal, and at least one additional metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. Such complex fluorides have low refractive index anisotropy, and therefore can improve infrared light transmittance. Therefore, they are suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0136] (Technology 3) The structure according to Technology 1 or 2, wherein the complex fluoride contains fluorine, the alkali metal, and aluminum as main components. Such complex fluorides have low refractive index anisotropy, and therefore can improve infrared light transmittance. Therefore, they are suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0137] (Technology 4) The structure according to any one of Technologies 1 to 3, wherein the wavelength bandwidth in which the linear transmittance continuously exceeds 10% is 0.1 μm or more in the target wavelength band of 3 μm or more and 10 μm or less. This configuration increases infrared transmittance. Therefore, the structure is suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0138] (Technology 5) The structure according to any one of Technologies 1 to 4, wherein the wavelength bandwidth in which the linear transmittance continuously exceeds 50% is 0.1 μm or more in the target wavelength band of 3 μm or more and 5 μm or less. This configuration further enhances infrared transmittance. Therefore, it is further suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0139] (Technology 6) The structure according to any one of Technologies 1 to 5, wherein the weight loss rate when the structure is heated from 200°C to 500°C is 0.5% or less. This configuration reduces the amount of hydroxyl groups and water molecules inside the structure, thereby suppressing infrared absorption and scattering due to hydroxyl groups and water molecules. As a result, infrared transmittance can be further increased.

[0140] (Technology 7) The structure according to any one of Technologies 1 to 6, which is an infrared transmission filter. With this configuration, it is possible to provide an infrared detection device, a light emitting device, or the like that can suppress diffuse reflection of infrared light due to pores.

[0141] (Technology 8) An infrared detection device comprising the structure according to any one of Technologies 1 to 7. With this configuration, it is possible to provide an infrared detection device that can suppress diffuse reflection of infrared light due to pores in the structure.

[0142] (Technology 9) A light-emitting device comprising the structure according to any one of Technologies 1 to 7. With this configuration, it is possible to provide a light-emitting device that can suppress diffuse reflection of infrared light due to pores in the structure.

[0143] (Technology 10) A method for producing a structure, comprising a step of pressurizing and heating raw materials containing at least one of a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal and water, and a complex fluoride containing at least one of a hydroxyl group and a water molecule under conditions of a pressure of 10 to 600 MPa and a temperature of 50 to 300°C, wherein the structure contains 85% by mass or more of an inorganic substance, 50% by mass or more of a polycrystalline body of the complex fluoride, a porosity of the structure is 30% or less, a median pore diameter of the structure is 500 nm or less, and a thickness of the structure is 10 μm or more. This allows the structure to be produced by a simple low-temperature process.

[0144] The entire contents of Japanese Patent Application No. 2022-114679 (filing date: July 19, 2022) are incorporated herein by reference.

[0145] Although the present embodiment has been described above, the present embodiment is not limited to this, and various modifications are possible within the scope of the gist of the present embodiment.

[0146] According to the present disclosure, it is possible to provide a structure suitable for applications such as an infrared-transmitting window for a gas sensor or a flame detection sensor, as well as an infrared detection device and a light-emitting device using the same. Furthermore, according to the present disclosure, it is possible to provide a method for manufacturing the structure, which can be manufactured using a simple low-temperature process.

[0147] REFERENCE SIGNS LIST 1 Structure 10 Base material 11 Continuous phase 100 Infrared detector 200 Light-emitting device

Claims

1. A structure including a base material including a continuous phase of a polycrystalline body of a complex fluoride including an alkali metal, The structure contains 85% by mass or more of an inorganic material, the structure contains 50 mass % or more of polycrystals of the complex fluoride, The porosity of the structure is 30% or less, The median pore size of the structure is 500 nm or less; The structure has a thickness of 10 μm or more.

2. 2. The structure of claim 1, wherein said complex fluoride comprises as major components fluorine, said alkali metal, and at least one additional metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium.

3. 3. The structure according to claim 1, wherein the complex fluoride contains fluorine, the alkali metal, and aluminum as main components.

4. 3. The structure according to claim 1, wherein a wavelength bandwidth in which the linear transmittance continuously exceeds 10% is 0.1 μm or more in a target wavelength band of 3 μm or more and 10 μm or less.

5. 3. The structure according to claim 1, wherein a wavelength bandwidth in which the linear transmittance continuously exceeds 50% is 0.1 μm or more in a target wavelength band of 3 μm or more and 5 μm or less.

6. 3. The structure according to claim 1, wherein the weight loss rate of the structure when heated from 200°C to 500°C is 0.5% or less.

7. 3. The structure of claim 1 or 2, which is an infrared transmitting filter.

8. An infrared detection device comprising the structure according to claim 1 or 2.

9. A light emitting device comprising the structure according to claim 1 or 2.

10. A method for producing a structure, comprising a step of pressurizing and heating raw materials containing at least one of a first fluoride containing an alkali metal, a second fluoride containing a metal different from the alkali metal, water, and a complex fluoride containing at least one of a hydroxyl group and a water molecule under conditions of a pressure of 10 to 600 MPa and a temperature of 50 to 300° C., The structure contains 85% by mass or more of an inorganic material, the structure contains 50 mass % or more of polycrystals of the complex fluoride, The porosity of the structure is 30% or less, The median pore size of the structure is 500 nm or less; The method for manufacturing a structure, wherein the thickness of the structure is 10 μm or more.