Complex fluoride powder, method for producing complex fluoride powder, and method for manufacturing structure

Abstract

This complex fluoride powder comprises a plurality of complex fluoride particles containing an alkali metal-containing complex fluoride, wherein the plurality of complex fluoride particles has an average particle size of 1 μm or less, the first weight loss rate when heated from 30°C to 200°C is 0.5 mass% or more, and the second weight loss rate when heated from 200°C to 500°C is 1 mass% or less.

Description

Complex fluoride powder, method for producing complex fluoride powder, and method for producing structure

[0001] The present invention relates to a complex fluoride powder, a method for producing the complex fluoride powder, and a method for producing 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, and an object of the present invention is to provide a complex fluoride powder capable of forming a structure suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors, a method for manufacturing the complex fluoride powder, and a method for manufacturing the structure.

[0006] In order to solve the above problems, a complex fluoride powder according to a first aspect of the present invention includes a plurality of complex fluoride particles including a complex fluoride containing an alkali metal. The average particle size of the plurality of complex fluoride particles is 1 μm or less. The complex fluoride powder exhibits a first weight loss rate of 0.5% by mass or more when heated from 30° C. to 200° C. The complex fluoride powder exhibits a second weight loss rate of 1% by mass or less when heated from 200° C. to 500° C.

[0007] A method for producing a complex fluoride powder according to a second aspect of the present invention includes the steps of: generating a plurality of complex fluoride particles by reacting, in a liquid phase, a first metal compound which is an alkali metal fluoride with a second metal compound which has a metal different from the alkali metal fluoride; separating the generated plurality of complex fluoride particles; heating the separated plurality of complex fluoride particles at 200°C or higher; and adding water to the heated plurality of complex fluoride particles.

[0008] The method for producing a structure according to the third aspect of the present invention includes a step of pressurizing and heating the complex fluoride powder obtained by the method for producing a complex fluoride powder.

[0009] 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 an SEM image of the complex fluoride powder obtained in Comparative Example 1, observed at 20,000x magnification. FIG. 4 is an SEM image of the complex fluoride powder obtained in Comparative Example 2, observed at 20,000x magnification. FIG. 5 is an SEM image of the complex fluoride powder obtained in Comparative Example 4, observed at 20,000x magnification. FIG. 6 is an SEM image of the complex fluoride powder obtained in Comparative Example 5, observed at 20,000x magnification. FIG. 7 is an SEM image of the complex fluoride powder obtained in Comparative Example 6, observed at 20,000x magnification. FIG. 8 is an SEM image of the complex fluoride powder obtained in Comparative Example 7, observed at 20,000x magnification. FIG. 9 is an SEM image of the complex fluoride powder obtained in Comparative Example 8, observed at 20,000x magnification. FIG. 10 is an SEM image of the complex fluoride powder obtained in Comparative Example 9, observed at 20,000x magnification. FIG. 11 is an SEM image of the complex fluoride powder obtained in Comparative Example 10, observed at 20,000x magnification. FIG. 12 is an SEM image of the complex fluoride powder obtained in Comparative Example 11, observed at 20,000x magnification. FIG. 13 is a graph showing the relationship between the heat treatment temperature and the average particle size of the hydrated complex fluoride powder. FIG. 14 shows the linear transmittance of the structures according to Examples 1 to 3 and Comparative Examples 13 and 14. FIG. 15 shows the linear transmittance of the structures according to Examples 4 to 6, Comparative Example 12, and Comparative Example 15. FIG. 16 is a scatter plot showing the relationship between the average particle size and linear transmittance of the complex fluoride powder according to the comparative example. Fig. 17 is a scatter diagram showing the relationship between the second weight loss rate and the linear transmittance when the complex fluoride powder according to the comparative example is heated from 200°C to 500°C. Fig. 18 is a scatter diagram showing the relationship between the first weight loss rate and the linear transmittance when the complex fluoride powder according to the comparative example is heated from 30°C to 200°C. Fig. 19 is a diagram comparing the TG curve of a complex fluoride powder subjected to a heat treatment at 400°C with the TG curve of a complex fluoride powder subjected to a heat treatment at 400°C and to which hydration has been added. Fig. 20 is a diagram comparing the weight loss rates of a complex fluoride powder subjected to a heat treatment at 400°C and a complex fluoride powder subjected to a heat treatment at 400°C and to which hydration has been added. Fig. 21 is a graph showing the relationship between the heat treatment temperature and the relative density of the hydrated complex fluoride powder.Fig. 22 is a graph showing the relationship between the heat treatment temperature and the in-line transmittance of a hydrated complex fluoride powder. Fig. 23 is an XRD pattern of the powder of the structure according to Examples 1 to 3 and Comparative Examples 13 and 14. Fig. 24 is an XRD pattern of the powder of the structure according to Examples 4 to 6 and Comparative Examples 12 and 15.

[0010] Hereinafter, the complex fluoride powder, structure, method for manufacturing the complex fluoride powder, and method for manufacturing the structure according to the present embodiment will be described in detail with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0011] [Complex Fluoride Powder] First, the complex fluoride powder according to this embodiment will be described. The complex fluoride powder according to this embodiment contains a plurality of complex fluoride particles containing a complex fluoride. The complex fluoride particles may contain 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more of the complex fluoride.

[0012] 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 Therefore, the complex fluoride containing an alkali metal has higher water resistance than the alkali metal fluoride.

[0013] The complex fluoride may contain fluorine, an alkali metal, and an additional metal as main components. The additional metal may include at least one metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. Specifically, the additional metal may include at least one metal selected from the group consisting of magnesium, calcium, strontium, barium, aluminum, gallium, indium, zinc, and yttrium. Inorganic substances containing these metal elements can easily form structures by a pressurized and heated method, as described below. Furthermore, such complex fluorides have low refractive index anisotropy, thereby improving infrared light transmittance. Note that 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%.

[0014] 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, Li ３ 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, LiMgF３ , 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.

[0015] 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 ３ AlF 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.

[0016] A part of the anions constituting the complex fluoride may be substituted with hydroxide ions or oxide ions. For example, in the case of complex fluoride particles synthesized in a liquid phase, a part 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 a filter for a sensor is formed using the complex fluoride powder, the sensor sensitivity can be improved by cutting unnecessary wavelengths with the filter. Furthermore, when a structure formed using the complex fluoride powder contains hydroxyl groups, the variation in transmittance due to humidity is reduced, and the sensor becomes less susceptible to the effects of humidity.

[0017] The complex fluoride may be crystalline or amorphous. The complex fluoride may be single crystal or polycrystalline. When the complex fluoride is polycrystalline, it is superior in terms of gas barrier properties or durability. The structure may contain 50% by mass or more of a polycrystalline complex fluoride. In this case, the resulting structure is one that can easily utilize the properties of the complex fluoride. By containing 50% by mass or more of a 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 portions with different refractive indices within the structure, thereby suppressing light scattering and increasing the infrared transmittance of the structure. In the structure, the mass proportion of the complex fluoride may be 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0018] The BET specific surface area of ​​the multiple complex fluoride particles is 2 to 200 m ２ / g. The BET specific surface area may be 2 m ２ When the BET specific surface area is 3 m / g or more, when a structure is formed, the influence of light scattering inside the structure is reduced, and the transmittance of the structure can be increased. ２ / g or more, 4m ２ / g or more, 5m ２ / g or more, 6m ２ / g or more, or 7m ２ The BET specific surface area may be 100 m / g or more.２ / g or less, 50m ２ / g or less, 20m ２ / g or less, 10m ２ / g or less, or 5m ２ The BET specific surface area can be measured by the method described in the Examples section below.

[0019] The average particle diameter of the multiple complex fluoride particles is 1 μm or less. When the average particle diameter is 1 μm or less, the small average particle diameter reduces the influence of light scattering inside the structure when a structure is formed, and the transmittance of the structure can be increased. The average particle diameter may be 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 500 nm or less. There is no particular limitation on the lower limit of the average particle diameter, but the average particle diameter may be 0.01 μm or more. The average particle diameter may be 100 nm or more, 200 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more. The average particle diameter can be calculated from the above BET specific surface area using the formula d=6 / (ρA ＢＥＴ In the above formula, d is the average particle diameter, ρ is the density of the complex fluoride particles, A ＢＥＴ represents the BET specific surface area.

[0020] The complex fluoride powder has a first weight loss rate of 0.5% by mass or more when heated from 30°C to 200°C. When the first weight loss rate is 0.5% by mass or more, there is a tendency for a large amount of water to be present on the surface of the complex fluoride particles. Therefore, when the structure is molded by the pressurized heating method described below, the fluidity of the complex fluoride particles themselves and dehydration condensation between the complex fluoride particles are promoted, improving the moldability of the structure and increasing the density of the structure. As a result, the moldability of the structure can be improved. The first weight loss rate may be 1% by mass or more, 2% by mass or more, 5% by mass or more, or 10% by mass or more. In addition, the upper limit of the first weight loss rate is not particularly limited, and the first weight loss rate may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less.

[0021] The second weight loss rate of the complex fluoride powder when heated from 200°C to 500°C is 1% by mass or less. When the second weight loss rate is 1% by mass or less, the moisture content inside the complex fluoride particles is low. Therefore, when a structure is molded, the number of water molecules or hydroxy groups inside the structure is reduced, which suppresses infrared absorption and increases the infrared light transmittance. The second weight loss rate may be 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, or 0.15% by mass or less. The lower limit of the second weight loss rate is not particularly limited, but the second weight loss rate may be 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more.

[0022] The weight loss rate can be measured by thermogravimetry (TG) in accordance with JIS K7120-1987. The first weight loss rate can be calculated by the following formula (1). The second weight loss rate can be calculated by the following formula (2).

[0023] First weight reduction rate (%) = (((mass of complex fluoride particles at 30°C) - (mass of complex fluoride particles at 200°C)) / (mass of complex fluoride particles at 30°C)) × 100 (1)

[0024] Second 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 (2)

[0025] The heated complex fluoride powder may contain hydrated water in addition to the complex fluoride particles. The raw material of the complex fluoride powder may contain by-products such as simple fluorides, oxides, and hydroxides containing a single metal element as inevitable impurities.

[0026] The content of the complex fluoride particles in the complex fluoride powder may be 50% by mass or more. By setting the content of the complex fluoride particles to 50% by mass or more, it becomes easy to form a structure using the complex fluoride powder. The content of the complex fluoride particles in the complex fluoride powder may be 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more.

[0027] [Structure] Next, a structure 1 according to this embodiment will be described with reference to Fig. 1 and Fig. 2. The structure 1 is a ceramic structure formed by pressing and heating a complex fluoride powder. As shown in Fig. 1, the structure 1 according to this embodiment includes a base material 10. The base material 10 includes a continuous phase 11 of a complex fluoride.

[0028] The structure 1 may contain 80% by mass or more of an inorganic substance. By containing 80% by mass or more of an inorganic substance, it is possible to obtain a structure 1 that is less likely to deteriorate over time and has high infrared transmittance, compared to when a resin is used. The inorganic substance contains the above-mentioned complex fluoride. Furthermore, the structure 1 may contain 85% by mass or more of the inorganic substance, 90% by mass or more, or 95% by mass or more. The structure 1 may contain 100% by mass or less of the inorganic substance.

[0029] 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.

[0030] The continuous phase 11 may be composed of a substance similar to the complex fluoride constituting the complex fluoride particles 12 as described above. The complex fluoride particles 12 may employ the same features as those described for the complex fluoride particles of the complex fluoride powder. That is, the complex fluoride particles 12 may have, for example, the same chemical and physical properties as the complex fluoride particles of the complex fluoride powder. For example, 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. Furthermore, from the viewpoint of light transmittance, the inorganic substance constituting the complex fluoride particles 12 is preferably amorphous. Note that, if crystalline, the complex fluoride particles 12 may be monocrystalline or polycrystalline.

[0031] The average particle diameter of the multiple complex fluoride particles 12 is preferably 1 μm or less. When the average particle diameter of the multiple fluoride particles 12 is 1 μm or less, the light transmittance of the structure 1 is increased. Furthermore, when the average particle diameter of the multiple fluoride particles 12 is within this range, the multiple 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 multiple fluoride particles 12 is within this range, the proportion of pores present inside the structure 1 is 30% or less, as described below. Furthermore, since the size of pores generated between the multiple fluoride particles 12 is reduced, the strength of the structure 1 can be increased. The average particle diameter of the multiple complex fluoride particles 12 may be 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, or 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).

[0032] 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.

[0033] 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 provide a structure 1 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.

[0034] 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.

[0035] The porosity in the cross section of the structure 1 may be 30% or less. That is, the porosity of pores exceeding 0 nm in the cross section of the structure 1 may be 30% or less. Specifically, when observing the cross section of the structure 1, the average ratio of pores per unit area may be 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.

[0036] 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.

[0037] The median pore diameter of the structure 1 may be 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.

[0038] 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 1 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.

[0039] The structure 1 is infrared light transmissive. The structure 1 may have a wavelength bandwidth in which the linear transmittance is equal to or greater than a predetermined value in the target wavelength band. The linear transmittance of the structure 1 can be obtained by measuring 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 which the linear transmittance is equal to or greater than a predetermined value in the target wavelength band. 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 which the linear transmittance is equal to or greater than a predetermined value in the target wavelength band. 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.

[0040] In a 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 is continuously 60% or more 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 3.8 μm or more. The target wavelength band may be 8 μm or less, 6 μm or less, or 4.4 μm or less. The wavelength bandwidth in which the linear transmittance is 60% or more 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 is 60% or more may be 3 μm or less, 2 μm or less, 1 μm or less, or 0.6 μm or less. The linear transmittance in the above wavelength bandwidth may be 65% or more. The upper limit of the linear transmittance in the above wavelength bandwidth is not particularly limited and may be, for example, 100%.

[0041] At a wavelength of 4 μm, the linear transmittance per mm of thickness of the structure 1 may be 60% or more, or may be 65% or more. Furthermore, 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. 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 be 60% or more, or may be 65% or more.

[0042] The thickness t of the structure 1 may be 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.

[0043] The structure 1 may be, for example, 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.

[0044] When the structure 1 is used as an infrared transmission filter, its shape is not particularly limited. The shape of the structure 1 may be a flat plate, a concave lens, or a convex lens. When the structure 1 is lenticular, it is 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.

[0045] The structure 1 may be used in an infrared detection device that is a flame sensor for detecting flames. That is, the infrared detection device may include the structure 1 that is an infrared transmission filter. Infrared rays emitted from a flame or the like pass through the structure 1, and the flame can be detected using the infrared rays emitted from the flame. The infrared detection device may also be used in a human presence sensor, a biosensor, a security sensor, a gas sensor, a non-contact thermometer, a solid-state imaging device, a camera module, or the like.

[0046] Furthermore, the structure 1 may be used in a light-emitting device. That is, a light-emitting device may include the structure 1. Light containing infrared rays emitted from a light source has a portion of the infrared rays cut by the structure 1, and the remaining infrared light passes through the structure 1. Therefore, the light-emitting device according to this embodiment can irradiate light having a specific wavelength. The light-emitting device 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.

[0047] [Method for producing complex fluoride powder] Next, a method for producing a complex fluoride powder according to this embodiment will be described. The method for producing a complex fluoride powder according to this embodiment includes a step of producing a plurality of complex fluoride particles, a step of separating the particles, a step of heating the particles, and a step of adding water.

[0048] In the step of producing a plurality of complex fluoride particles, a first metal compound which is an alkali metal fluoride and a second metal compound which has a metal different from the alkali metal fluoride are mixed and reacted in a liquid phase to produce a plurality of complex fluoride particles.

[0049] The method for mixing the alkali metal fluoride and the second metal compound is not particularly limited, and may be dry mixing or wet mixing. 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, the two solutions may be mixed simultaneously in equal amounts using a microchannel or the like. For example, water may be used as the solvent.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] The method for producing a complex fluoride powder does not require the use of hydrofluoric acid. Hydrofluoric acid is highly corrosive and dissolves glass, so there are limitations on the equipment that can be used. Furthermore, hydrofluoric acid is highly toxic, so safety measures are also necessary. However, in the method for producing a complex fluoride powder according to this embodiment, complex fluoride particles are produced by reacting a first metal compound, which is an alkali metal fluoride, with a second metal compound. Therefore, since hydrofluoric acid is not required, glass or the like can be used, and safety is higher than when hydrofluoric acid is used.

[0054] 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.

[0055] 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.

[0056] In the method for producing a complex fluoride powder, the complex fluoride particles may be dried after separation and before heating at 200°C or higher. The drying temperature is not particularly limited, but may 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, 250°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.

[0057] In the hydration step, hydration is added to a plurality of heated complex fluoride particles. As described above, when complex fluoride particles are heated, the water content inside the complex fluoride particles decreases, but the fluidity during the heating and pressurizing process described below is low, making it difficult to easily form Structure 1. Therefore, in the method for producing a complex fluoride powder according to this embodiment, hydration is added to a plurality of heated complex fluoride particles. This makes it possible to increase the amount of water adsorbed on the surfaces of the complex fluoride particles while maintaining a low water content inside the complex fluoride particles. This increases the fluidity during the heating and pressurizing process, making it easy to form Structure 1. Furthermore, by increasing the fluidity during the heating and pressurizing process, it is possible to form a dense and high-density Structure 1.

[0058] The amount of water added to the complex fluoride particles may be 0.5% by mass or more relative to the complex fluoride particles. The amount of water added to the complex fluoride particles may be 1% by mass or more, 2% by mass or more, 5% by mass or more, or 10% by mass or more relative to the complex fluoride particles. Furthermore, the amount of water added to the complex fluoride particles may be 50% by mass or less, 40% by mass or less, 30% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less relative to the complex fluoride particles.

[0059] [Method for manufacturing structure] Next, a method for manufacturing the structure 1 according to this embodiment will be described. The structure 1 can be manufactured by pressurizing and heating the above-mentioned complex fluoride powder. By using such a pressurizing and heating method, the complex fluoride particles are bonded to each other while being deformed, so that the structure 1 having a small porosity can be formed.

[0060] A complex fluoride powder containing complex fluoride particles is filled into a mold. After the complex fluoride powder is filled into the mold, the mold may be heated as needed. Then, pressure is applied to the complex fluoride powder inside the mold, creating a high-pressure state inside the mold. At this time, the complex fluoride powder is densified and the complex fluoride particles are bonded to each other.

[0061] The heating and pressing 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 complex fluoride powder to 50 to 300°C, and then pressurize it at a pressure of 10 to 600 MPa. The temperature at which the complex fluoride powder is heated is more preferably 80 to 250°C, and even more preferably 100 to 200°C. The pressure at which the complex fluoride powder is pressed is more preferably 50 to 600 MPa.

[0062] Then, the molded body is removed from the mold to obtain Structure 1. It is believed that by applying pressure to a complex fluoride powder 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.

[0063] 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.

[0064] In contrast, in the manufacturing method of this embodiment, a complex fluoride powder containing complex fluoride particles containing at least one of a hydroxyl group and a water molecule 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 pressing while being heated at 50°C to 300°C, precise temperature control is not required, and it is possible to reduce manufacturing costs.

[0065] As described above, the method for producing the structure 1 of this embodiment includes a step of pressurizing and heating the complex fluoride powder. 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.

[0066] 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.

[0067] (Comparative Example 1) First, sodium hexafluoroaluminate (Na ３ AlF ６ Specifically, 64 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., special grade reagent) and 8 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 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 to obtain Na ３ AlF ６ Particles (complex fluoride powder) were obtained.

[0068] Comparative Example 2: 24 mmol of NaF powder and 3 mmol of AlCl ３ ・6H ２ A complex fluoride powder was prepared in the same manner as in Comparative Example 1, except that O powder was used.

[0069] (Comparative Example 3) The residue was dried at -60 to -100 kPa and 200°C for 2 hours. The obtained powder was then pulverized in a mortar and heat-treated in air at 400°C for 2 hours to obtain a complex fluoride powder. Except for the above, the complex fluoride powder was produced in the same manner as in Comparative Example 2.

[0070] Comparative Example 4 A complex fluoride powder was produced in the same manner as in Comparative Example 2, except that the residue was dried at −60 to −100 kPa and 80° C. for 2 hours, and the resulting powder was then pulverized in a mortar and heat-treated in air at 300° C. for 2 hours to obtain a complex fluoride powder.

[0071] Comparative Example 5 A complex fluoride powder was produced in the same manner as in Comparative Example 4, except that the heat treatment temperature was set to 400°C.

[0072] Comparative Example 6 A complex fluoride powder was produced in the same manner as in Comparative Example 4, except that the heat treatment temperature was set to 500°C.

[0073] Comparative Example 7 A complex fluoride powder was produced in the same manner as in Comparative Example 4, except that the heat treatment temperature was set to 600°C.

[0074] (Comparative Example 8) A complex fluoride powder was produced in the same manner as in Comparative Example 1, except that after drying the residue, the obtained powder was pulverized in a mortar and heat-treated in air at 300°C for 2 hours to obtain a complex fluoride powder.

[0075] Comparative Example 9 A complex fluoride powder was produced in the same manner as in Comparative Example 8, except that the heat treatment temperature was set to 400°C.

[0076] Comparative Example 10 A complex fluoride powder was produced in the same manner as in Comparative Example 8, except that the heat treatment temperature was set to 500°C.

[0077] Comparative Example 11 A complex fluoride powder was produced in the same manner as in Comparative Example 8, except that the heat treatment temperature was set to 600°C.

[0078] [Evaluation] (Observation of Powder) Using a scanning electron microscope (SEM), the surfaces of the complex fluoride powders obtained by synthesis were observed at a magnification of 20,000 times. SEM images of the complex fluoride powders obtained in Comparative Examples 1 to 2 and Comparative Examples 4 to 11 are shown in Figs. 3 to 12. A graph showing the relationship between the heat treatment temperature and the average particle size is shown in Fig. 13.

[0079] (Specific Surface Area) Using a specific surface area measuring device, the adsorption isotherm of nitrogen gas was measured at 77 K by a constant volume method, and the BET specific surface area was calculated from the adsorption isotherm using the BET equation. The results are shown in Table 1.

[0080] (Average particle diameter) Assuming that the particles are spherical, from the BET specific surface area obtained as described above, d = 6 / (ρA ＢＥＴ The average particle size was calculated using the formula: A ＢＥＴis the BET specific surface area, ρ is the density of the complex fluoride particles, and d is the average particle diameter. ３ AlF ６ ) is a density of 2.98 g / cm ３ was used.

[0081] (Weight Loss Rate) The weight loss rate of the powder was measured using a thermogravimetry (TG) apparatus. Specifically, 15 to 20 mg of a powder 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 loss of the sample at 200°C by the weight of the sample at 30°C. The results are shown in Table 1 as the first weight loss rate. Similarly, the second weight loss rate from 200°C to 500°C was calculated by dividing the weight loss of the sample at 500°C by the weight of the sample at 200°C. The results are shown in Table 1 as the second weight loss rate.

[0082] (Linear transmittance) First, a complex fluoride powder was placed inside a cylindrical molding die (Φ12) having an internal space. The complex fluoride powder was heated and pressurized under conditions of 180°C, 400 MPa, and 20 minutes. In this way, a test sample having a solidified cylindrical structure was obtained. The test sample was measured by a transmission method using an FT-IR device to obtain an infrared transmission spectrum. The results are shown in Figures 14 and 15. 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. Table 1 also lists the average linear transmittance at wavelengths of 3.8 μm to 4.4 μm.

[0083]

[0084] As shown in Table 1 and Figure 13, when the heat treatment temperature is the same, the higher the raw material concentration during synthesis, the smaller the average particle size. Also, as shown in Table 1 and Figure 13, when the raw material concentration during synthesis is the same, the higher the heat treatment temperature, the larger the average particle size. That is, as shown in Table 1, when the raw material concentration during synthesis is the same, the higher the heat treatment temperature, the smaller the BET specific surface area.

[0085] 16, it can be seen that the linear transmittance is high when the average particle size of the complex fluoride powder is 1 μm or less, from a comparison between Comparative Examples 1 to 6 and 8 to 10 and Comparative Example 7 and Comparative Example 11. From this, it is considered that the small average particle size reduces the influence of light scattering inside the structure, and the linear transmittance of the solidified structure is high.

[0086] As shown in Table 1 and Fig. 16, a comparison of Comparative Examples 3 to 6 and 8 to 10 with Comparative Examples 1 to 2 reveals that structures formed from heat-treated complex fluoride powders have higher in-line transmittances than structures formed from non-heat-treated complex fluoride powders. As shown in Table 1 and Fig. 17, the second weight loss rates of heat-treated Comparative Examples 3 to 11 when heated from 200°C to 500°C were 1% by mass or less, which was smaller than that of Comparative Examples 1 to 2 without heat treatment. From this, it is thought that the water content inside the complex fluoride particles was reduced by heat treatment, resulting in reduced absorption of infrared light by hydroxyl groups and water, and therefore higher in-line transmittance.

[0087] However, the complex fluoride powders of Comparative Examples 3 to 11, which were subjected to heat treatment, did not have good moldability of the solidified structures compared to the complex fluoride powders of Comparative Examples 1 and 2, which were not subjected to heat treatment. As shown in Table 1 and Fig. 18, the first weight loss rates of Comparative Examples 3 to 11, which were subjected to heat treatment, when heated from 30°C to 200°C were 0.5% by mass or less, which was smaller than that of Comparative Examples 1 and 2, which were not subjected to heat treatment. From this, it was thought that the heat treatment reduced the amount of water adsorbed on the particle surfaces, resulting in poor moldability of the structures.

[0088] Therefore, an attempt was made to increase the amount of water adsorbed on the particle surface by adding 10% by mass of water to the complex fluoride particles of Comparative Example 5, which had been heat-treated at 400°C. This resulted in a structure with good moldability. Therefore, a thermogravimetric (TG) analyzer was used to measure the weight loss of samples with and without hydration under the same conditions as described above. The results are shown in Figure 19. Furthermore, the results of measuring the first weight loss rate when these samples were heated from 30°C to 200°C and the second weight loss rate when heated from 200°C to 500°C are shown in Figure 20.

[0089] As shown in Figures 19 and 20, the first weight loss rate of the hydrated complex fluoride powder was 0.5% or more. Furthermore, the second weight loss rate of the hydrated complex fluoride powder was 1% or less. From these results, it was considered that a structure with excellent linear transmittance and good moldability could be obtained by setting the first weight loss rate to 0.5% or more and the second weight loss rate to 1% or less. To demonstrate this, the following complex fluoride powder was produced.

[0090] Example 1 A complex fluoride powder was prepared in the same manner as in Comparative Example 4, except that the heat treatment temperature was set to 300° C. Next, 10% by mass of water was added to the complex fluoride particles, and the obtained powder was used as the complex fluoride powder according to this example.

[0091] Example 2 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 5 was used as the complex fluoride powder of this example.

[0092] Example 3 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 6 was used as the complex fluoride powder of this example.

[0093] Example 4 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 8 was used as the complex fluoride powder of this example.

[0094] Example 5 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 9 was used as the complex fluoride powder of this example.

[0095] Example 6 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 10 was used as the complex fluoride powder of this example.

[0096] Comparative Example 12 A powder obtained by adding 10% by mass of water to the complex fluoride particles of Comparative Example 1 was used as the complex fluoride powder of this example.

[0097] Comparative Example 13 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 2 was used as the complex fluoride powder of this example.

[0098] Comparative Example 14 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 7 was used as the complex fluoride powder of this example.

[0099] Comparative Example 15 A powder obtained by adding 10 mass % of water to the complex fluoride particles of Comparative Example 11 was used as the complex fluoride powder of this example.

[0100] [Evaluation] The specific surface area, average particle size, weight loss rate, and linear transmittance were measured in the same manner as described above. The relative density was also measured as follows.

[0101] (Relative Density) First, a structure was prepared from the complex fluoride powder obtained in each example in the same manner as described above. Next, the volume and mass of the structure were measured, and the apparent density of the structure was calculated. The apparent density of the test sample was then 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.

[0102]

[0103] From the results of Figures 19 and 20, it is considered that the first weight reduction rate is 0.5 mass% or more and the second weight reduction rate is 1 mass% or less in the complex fluoride powders of Examples 1 to 6 and Comparative Examples 12 to 15.

[0104] All of the structures of Examples 1 to 6 and Comparative Examples 12 to 15 had good moldability. As shown in Table 2 and Fig. 21, all of the structures had a relative density of 70% or more, and were confirmed to be dense. Furthermore, as shown in Table 2 and Fig. 22, the structures formed from the complex fluoride powders of Examples 1 to 6 were confirmed to have sufficient in-line transmittance.

[0105] Next, the powders obtained by pulverizing the structures of Examples 1 to 6 and Comparative Examples 12 to 15 were measured using a powder X-ray diffraction (XRD) device to obtain XRD patterns. These results are shown in Figures 23 and 24. As shown in Figures 23 and 24, when the heat treatment temperature was 300°C to 500°C, a heterophase (Na ５ Al ３ F １４ ) is present, but in all examples, the main phase is Na ３ AlF ６ It was confirmed that the structure is Na ３ AlF ６ It was confirmed that the polycrystalline material contained at least 95 mass % of the above.

[0106] From the above results, it was confirmed that when the average particle size of the complex fluoride particles is 1 μm or less, the first weight loss rate is 0.5 mass% or more, and the second weight loss rate is 1 mass% or less, a structure with excellent in-line transmittance can be successfully formed.

[0107] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0108] (Technology 1) A complex fluoride powder comprising a plurality of complex fluoride particles including a complex fluoride containing an alkali metal, wherein the plurality of complex fluoride particles have an average particle size of 1 μm or less, and exhibit a first weight loss rate of 0.5 mass % or more when heated from 30°C to 200°C, and a second weight loss rate of 1 mass % or less when heated from 200°C to 500°C.

[0109] 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.

[0110] (Technology 2) The BET specific surface area of ​​the multiple complex fluoride particles is 2 to 200 m ２ / g. With this configuration, when a structure is formed, the influence of light scattering inside the structure can be reduced, and therefore the transmittance of the structure can be increased.

[0111] (Technology 3) The complex fluoride powder according to Technology 1 or 2, wherein the complex fluoride contains fluorine, the alkali metal, and an additional metal, and the additional metal contains at least one metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. Such a complex fluoride can reduce the anisotropy of the refractive index. Therefore, the transmittance of infrared light can be improved.

[0112] (Technology 4) The complex fluoride powder according to any one of Technologies 1 to 3, wherein the complex fluoride contains fluorine, the alkali metal, and aluminum. Such a complex fluoride can reduce the anisotropy of the refractive index, thereby improving the transmittance of infrared light.

[0113] (Technology 5) A method for producing a complex fluoride powder according to any one of Technologies 1 to 4, comprising the steps of: generating a plurality of complex fluoride particles by reacting a first metal compound, which is an alkali metal fluoride, with a second metal compound, which has a metal different from the alkali metal fluoride, in a liquid phase; separating the generated plurality of complex fluoride particles; heating the separated plurality of complex fluoride particles at 200° C. or higher; and adding water to the heated plurality of complex fluoride particles. By such a production method, the above-mentioned complex fluoride powder can be easily produced.

[0114] (Technology 6) A method for producing a complex fluoride powder according to Technology 5, which does not use hydrofluoric acid. This configuration allows the production of a complex fluoride powder without using hydrofluoric acid. Therefore, glass or the like can be used, and the method is safer than the method using hydrofluoric acid.

[0115] (Technology 7) A method for producing a structure, comprising a step of pressurizing and heating the complex fluoride powder obtained by the method for producing a complex fluoride powder according to Technology 5 or 6. This configuration allows the structure to be produced by a simple low-temperature process, and the structure is not easily dissolved in water. Such a structure is suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors.

[0116] The entire contents of Japanese Patent Application No. 2023-112343 (filing date: July 7, 2023) are incorporated herein by reference.

[0117] 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.

[0118] According to the present disclosure, it is possible to provide a complex fluoride powder capable of forming a structure suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors, a method for manufacturing the complex fluoride powder, and a method for manufacturing the structure.

[0119] 1 Structure 10 Base material 11 Continuous phase

Claims

1. It contains multiple complex fluoride particles, including complex fluorides containing alkali metals. The average particle diameter of the aforementioned plurality of complex fluoride particles is 1 μm or less. The first weight loss rate when heated from 30°C to 200°C is 0.5% by mass or more. A complex fluoride powder in which the second weight loss rate when heated from 200°C to 500°C is 1% by mass or less.

2. The BET specific surface area of ​​the aforementioned plurality of complex fluoride particles is 2 to 200 m². ２ The complex fluoride powder according to claim 1, wherein the amount is / g.

3. The complex fluoride powder according to claim 1 or 2, wherein the complex fluoride comprises fluorine, the alkali metal, and an additional metal, the additional metal comprising at least one metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium.

4. The complex fluoride powder according to claim 1 or 2, wherein the complex fluoride comprises fluorine, the alkali metal, and aluminum.

5. A step of generating multiple polyfluoride particles by reacting a primary metal compound, which is an alkali metal fluoride, with a secondary metal compound having a different metal from the alkali metal fluoride in a liquid phase, A process for separating the multiple complex fluoride particles generated, A step of heating the separated multiple complex fluoride particles at 200°C or higher, A process of adding water to multiple heated polyfluoride particles, A method for producing a complex fluoride powder according to claim 1 or 2, comprising the above.

6. A method for producing a complex fluoride powder according to claim 5, without using hydrofluoric acid.

7. A method for manufacturing a structure, comprising the step of pressurizing and heating the complex fluoride powder obtained by the method for manufacturing complex fluoride powder according to claim 5.