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

[Technical Field]

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

[0002] Conventionally, infrared-transmitting windows based on inorganic fluorides have been used for special applications in fields such as academic research and industry, such as window materials for scientific and chemical instruments. Patent Document 1 discloses a Fourier transform infrared spectrophotometer that measures fluorine-based gases in a sample containing corrosive gases, and includes a measuring cell whose cell window is composed of one selected from the group consisting of CaF2, BaF2, MgF2, LiF, and ZnSe. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 176624 [Overview of the project]

[0004] On the other hand, technologies are known that use infrared detection elements and infrared-transmitting optical filters to sense various gases and flames. However, alkali metal fluorides, as mentioned 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, and it may be impossible to manufacture structures with high infrared transmittance without using advanced technologies that require high temperatures of at least 1000°C or higher.

[0005] This invention has been made in view of the problems of the prior art. The object of this invention is to provide a structure suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors, and an infrared detection device using the same. Another object of this invention is to provide a method for manufacturing the above structure, which can be manufactured by a simple low-temperature process.

[0006] To solve the above problems, a structure according to a first aspect of the present invention comprises a base material containing a continuous phase of polycrystalline polyfluoride containing an alkali metal. The structure contains 85% by mass or more of inorganic material, 50% by mass or more of polycrystalline polyfluoride, the porosity of the structure is 30% or less, the median pore diameter of the structure is 500 nm or less, and the thickness of the structure is 10 μm or more.

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

[0008] A third aspect of the present invention provides a light-emitting device comprising 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 a raw material containing at least one of a primary fluoride containing an alkali metal, a secondary fluoride containing a metal other than an alkali metal, water, and a polyfluoride 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 inorganic material, 50% by mass or more of polycrystalline polyfluoride, the porosity of the structure is 30% or less, the median pore diameter of the structure is 500 nm or less, and the thickness of the structure is 10 μm or more. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a structure according to this embodiment. [Figure 2] Figure 2 is an enlarged cross-sectional view schematically showing another example of the structure according to this embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing an example of an infrared detection device according to this embodiment. [Figure 4] Figure 4 is a schematic diagram showing an example of a light-emitting device according to this embodiment. [Figure 5] Figure 5 shows an SEM image of the synthesized Na3AlF6 powder observed at 10,000x magnification. [Figure 6] Figure 6 is a SEM image of the synthesized K2NaAlF6 powder observed at a magnification of 10,000 times. [Figure 7] Figure 7 is a SEM image of the synthesized NaMgF3 powder observed at a magnification of 10,000 times. [Figure 8] Figure 8 is the XRD pattern of the powder of the test sample according to Example 1. [Figure 9] Figure 9 is the XRD pattern of the powder of the test sample according to Example 2. [Figure 10] Figure 10 is the XRD pattern of the powder of the raw material and the test sample according to Example 3. [Figure 11] Figure 11 is the XRD pattern of the powder of the raw material and the test sample according to Example 4. [Figure 12] Figure 12 is the XRD pattern of the powder of the raw material and the test sample according to Example 5. [Figure 13] Figure 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 a magnification of 10,000 times. [Figure 14] Figure 14 is a backscattered electron image of the CP-processed cross-section of the test sample according to Example 1 observed at a magnification of 10,000 times. [Figure 15] Figure 15 is a secondary electron image of the CP-processed cross-section of the test sample according to Example 2 observed at a magnification of 10,000 times. [Figure 16] Figure 16 is a backscattered electron image of the CP-processed cross-section of the test sample according to Example 2 observed at a magnification of 10,000 times. [Figure 17] Figure 17 is a secondary electron image of the CP-processed cross-section of the test sample according to Example 3 observed at a magnification of 10,000 times. [Figure 18] Figure 18 is a backscattered electron image of the CP-processed cross-section of the test sample according to Example 3 observed at a magnification of 10,000 times. [Figure 19] Figure 19 is a secondary electron image of the CP-processed cross-section of the test sample according to Example 4 observed at a magnification of 10,000 times. [Figure 20] Figure 20 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Example 4 at a magnification of 10,000 times. [Figure 21] Figure 21 is a secondary electron image obtained by observing the CP processed cross-section of the test sample according to Example 5 at a magnification of 10,000 times. [Figure 22] Figure 22 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Example 5 at a magnification of 10,000 times. [Figure 23] Figure 23 is a secondary electron image obtained by observing the CP processed cross-section of the test sample according to Example 1 at a magnification of 2,000 times. [Figure 24] Figure 24 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Example 1 at a magnification of 2,000 times. [Figure 25] Figure 25 is a secondary electron image obtained by observing the CP processed cross-section of the test sample according to Comparative Example 1 at a magnification of 2,000 times. [Figure 26] Figure 26 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Comparative Example 1 at a magnification of 2,000 times. [Figure 27] Figure 27 is a secondary electron image obtained by observing the CP processed cross-section of the test sample according to Example 3 at a magnification of 2,000 times. [Figure 28] Figure 28 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Example 3 at a magnification of 2,000 times. [Figure 29] Figure 29 is a secondary electron image obtained by observing the CP processed cross-section of the test sample according to Comparative Example 2 at a magnification of 2,000 times. [Figure 30] Figure 30 is a backscattered electron image obtained by observing the CP processed cross-section of the test sample according to Comparative Example 2 at a magnification of 2,000 times. [Figure 31] Figure 31 is an infrared spectrum obtained by measuring the test samples according to Example 1 and Example 2 by the transmission method. [Figure 32] Figure 32 is an infrared spectrum obtained by measuring the test samples according to Example 3 to Example 5 by the transmission method. [Figure 33]Figure 33 shows the infrared spectra of the test samples for Comparative Example 1 and Comparative Example 2, measured by transmission. [Figure 34] Figure 34 is a secondary electron image of the cross-section of the test sample according to Example 6, observed at a magnification of 10,000 times. [Figure 35] Figure 35 is a secondary electron image of the fracture surface of the test sample according to Example 6, observed at a magnification of 2,000 times. [Figure 36] Figure 36 shows a secondary electron image of the fracture surface of the test sample related to Comparative Example 3, observed at a magnification of 10,000 times. [Figure 37] Figure 37 shows a secondary electron image of the fracture surface of the test sample relating to Comparative Example 3, observed at a magnification of 2,000 times. [Figure 38] Figure 38 is a secondary electron image of the cross-section of the test sample according to Example 7, observed at a magnification of 10,000 times. [Figure 39] Figure 39 is a secondary electron image of the cross-section of the test sample according to Example 7, observed at a magnification of 2,000 times. [Figure 40] Figure 40 shows a secondary electron image of the fractured surface of the test sample related to Comparative Example 4, observed at a magnification of 10,000 times. [Figure 41] Figure 41 is a secondary electron image of the fractured surface of the test sample related to Comparative Example 4, observed at a magnification of 2,000 times. [Figure 42] Figure 42 is an SEM image of the Na3AlF6 powder obtained in Example 8. [Figure 43] Figure 43 is an SEM image of the Na3AlF6 powder obtained by heat treatment at 300°C in Example 9. [Figure 44] Figure 44 is an SEM image of the Na3AlF6 powder obtained by heat treatment at 400°C in Example 10. [Figure 45] Figure 45 is an SEM image of the Na3AlF6 powder obtained by heat treatment at 500°C in Example 11. [Figure 46] Figure 46 shows the XRD patterns of the Na3AlF6 powder obtained in each example. [Figure 47]Figure 47 is a secondary electron image of the structure formed from Na3AlF6 powder in Example 9. [Figure 48] Figure 48 is a backscattered electron image of the structure formed from Na3AlF6 powder in Example 9. [Figure 49] Figure 49 is a secondary electron image of the structure formed from Na3AlF6 powder in Example 10. [Figure 50] Figure 50 is a backscattered electron image of the structure formed from Na3AlF6 powder in Example 10. [Figure 51] Figure 51 is a secondary electron image of the structure formed from Na3AlF6 powder in Example 11. [Figure 52] Figure 52 is a backscattered electron image of the structure formed from Na3AlF6 powder in Example 11. [Figure 53] Figure 53 is a graph comparing the linear transmittance of the structures obtained in each example. [Figure 54] Figure 54 is a graph showing the relationship between heat treatment temperature and relative density. [Figure 55] Figure 55 is a graph showing the relationship between heat treatment temperature and linear transmittance. [Figure 56] Figure 56 shows the TG curves obtained by thermogravimetric analysis of Examples 8 and 10. [Figure 57] Figure 57 is a graph showing the relationship between the first weight loss rate and the second weight loss rate. [Modes for carrying out the invention]

[0011] The structure, infrared detection device, light-emitting device, and manufacturing method of the structure according to this embodiment will be described in detail below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0012] [Structure] As shown in Figure 1, the structure 1 of this embodiment comprises a base material 10. The base material 10 contains a continuous phase 11 of polycrystalline polyfluoride. The structure 1 of this embodiment is a ceramic structure.

[0013] Double fluorides contain alkali metals. For example, a double fluoride may contain at least one alkali metal selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. Alkali metal fluorides have high solubility in water, but double fluorides containing alkali metals have low solubility in water. The solubility of alkali metal fluorides in 100g of water at 25°C is, for example, 0.134g for LiF, 4.13g for NaF, 102g for KF, 300g for RbF, and 573g for CsF. On the other hand, the solubility of double fluorides containing alkali metals in 100g of water at 25°C is, for example, 0.042g for Na3AlF6 and 0.025g for NaMgF3.

[0014] The double fluoride may contain fluorine, alkali metals, and at least one additional metal selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium as its main components. 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. Because such double fluorides have low refractive index anisotropy, they can improve the transmittance of infrared light. Furthermore, inorganic substances containing these metal elements can be easily formed into structure 1 by a pressurized heating method, as described later. Here, "main component" means that the total content of fluorine, alkali metals, and additional metals in the double fluoride is 80% or more in molar ratio. The above total content may be 85% or more, 90% or more, 95% or more, or 100%.

[0015] The polyfluoride may specifically contain at least one of A3AlF6 and ABF3 (wherein the above compositional formula, A represents one or more alkali metals as described above, and B represents one or more alkaline earth metals as described above). A3AlF6 may contain, for example, at least one selected from the group consisting of Li3AlF6, Li2NaAlF6, Li2KAlF6, Na3AlF6, Na2LiAlF6, Na2KAlF6, K3AlF6, K2LiAlF6, and K2NaAlF6. ABF3 may contain, for example, at least one selected from the group consisting of LiMgF3, NaMgF3, KMgF3, LiCaF3, NaCaF3, and KCaF3. More specifically, the polyfluoride may contain at least one selected from the group consisting of Na3AlF6, K2NaAlF6, and NaMgF3. Na3AlF6 and K2NaAlF6 have cryolite-type crystal structures, and NaMgF3 has a perovskite-type crystal structure. Since these materials exhibit small refractive index anisotropy depending on crystal orientation, they are preferable from the viewpoint of infrared transmission.

[0016] The complex fluoride may contain fluorine, alkali metals, and aluminum as its main components. Here, "main components" means that the total molar content of fluorine, alkali metals, and aluminum in the complex fluoride is 80% or more. This total content may be 85% or more, 90% or more, 95% or more, or even 100%. The complex fluoride may contain, for example, sodium hexafluoroaluminate (Na3AlF6). Na3AlF6 is also known as a component of cryolite. Na3AlF6 has low refractive index anisotropy, and therefore exhibits excellent infrared light transmission.

[0017] The complex fluoride may have some of its constituent anions substituted with hydroxide ions and oxide ions. For example, in the case of complex fluoride particles synthesized in the 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 specific wavelengths. Therefore, when structure 1 is used, for example, as a sensor, the sensor sensitivity can be improved by cutting out unwanted wavelengths. Also, when structure 1 contains hydroxyl groups, the transmittance fluctuation due to humidity is reduced, making the sensor less susceptible to humidity.

[0018] Structure 1 contains 85% by mass or more of inorganic material. Therefore, compared to the case where resin is used, it is possible to obtain Structure 1 that is less prone to degradation over time and has high infrared transmittance. The inorganic material includes the above-mentioned complex fluoride. Furthermore, Structure 1 may contain 90% by mass or more of inorganic material, or 95% by mass or more. Structure 1 may contain 100% by mass or less of inorganic material.

[0019] The polycrystalline nature of the polycrystalline polyfluoride provides superior gas barrier properties and durability. Structure 1 may contain 50% by mass or more of polycrystalline polycrystalline polyfluoride. In this case, the resulting structure 1 is a structure that easily utilizes the properties of the polyfluoride. Including 50% by mass or more of polyfluoride results in a structure with higher moisture resistance than alkali metal fluoride. Furthermore, a higher mass percentage of polyfluoride reduces the proportion of parts with different refractive indices within structure 1, thereby suppressing light scattering and increasing the infrared transmittance of structure 1. In structure 1, the mass percentage of polyfluoride may be 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0020] As shown in Figure 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. Alternatively, the continuous phase 11 may cover at least a portion of the surface of each of the plurality of complex fluoride particles 12, or it may cover the entire surface of each of the plurality of complex fluoride particles 12. Each of the plurality of complex fluoride particles 12 may be bonded to one another. The complex fluoride particles 12 may be in point contact with each other, or they may be in surface contact where 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 material as the complex fluoride constituting the continuous phase 11 described above. The inorganic material constituting the complex fluoride particles 12 may be crystalline or amorphous. From the viewpoint of gas barrier properties or durability, the inorganic material constituting the complex fluoride particles 12 is preferably crystalline. Furthermore, from the viewpoint of light transmittance, the inorganic material constituting the complex fluoride particles 12 is preferably amorphous. If it is crystalline, the complex fluoride particles 12 may be single crystals 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. An average particle diameter of 50 μm or less for the complex fluoride particles 12 increases the light transmittance of the structure 1. Furthermore, having an average particle diameter within this range allows the complex fluoride particles 12 to bond strongly to each other, increasing the strength of the structure 1. Also, having an average particle diameter within this range results in a pore ratio of 30% or less within the structure 1, as described later. Additionally, the size of pores between the complex fluoride particles 12 becomes smaller. 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, unless otherwise specified, the value of "average particle diameter" refers to the value calculated as the average particle diameter of particles observed within several to tens of fields of view using observation methods such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0023] Structure 1 may contain impurities generated during manufacturing. These impurities may, for example, be raw materials for producing complex fluorides and may contain elements that constitute complex fluorides. 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 mentioned above. The impurities may also contain chalcogen compounds, halides, hydroxides, nitrides, or carbides containing oxides composed of a single metallic element. The impurities may be crystalline or amorphous.

[0024] The refractive index difference between the aforementioned double 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, resulting in a structure with high transmittance. There is no particular lower limit to the refractive index difference. The refractive index difference may be 0.08 or less, or 0.04 or less.

[0025] Structure 1 may contain organic materials such as resin particles. As will be described later, since Structure 1 can be obtained by heating and pressurizing at 100 to 300°C, materials with low heat resistance can be added to Structure 1. Furthermore, Structure 1 is not limited to materials with low heat resistance such as organic materials, and may also contain inorganic compounds other than polyfluorides and impurities to impart functionality.

[0026] The porosity of the cross-section of structure 1 is 30% or less. That is, the porosity of pores greater than 0 nm in the cross-section of structure 1 is 30% or less. Specifically, when the cross-section of structure 1 is observed, the average value of the proportion of pores per unit area is 30% or less. When the porosity is 30% or less, the number of pores inside the matrix portion decreases, resulting in a solidified body with high strength. It is preferable that the porosity of the cross-section of structure 1 be 20% or less, more preferably 10% or less, and even more preferably 5% or less. The smaller the porosity of the cross-section of structure 1, the more cracks originating from pores are suppressed, making it possible to increase the strength of structure 1. Furthermore, the smaller the porosity of the cross-section of structure 1, the more light scattering by pores is suppressed, making it possible to increase the transmittance of structure 1.

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

[0028] The median pore diameter of 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 structure 1 having high transmittance. Preferably, the median pore diameter is 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 refers to the pore diameter when the cumulative value of the pore diameter distribution based on area is 50%. The pore diameter refers to the diameter of a perfect circle when the shape of the pores in the cross-section of structure 1 is assumed to be a perfect circle.

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

[0030] Structure 1 has infrared light transmittance. In the target wavelength band, the linear transmittance of Structure 1 may have a wavelength bandwidth greater than or equal to a predetermined value. The linear transmittance of Structure 1 can be obtained by measuring it using the transmission method with an FT-IR (Fourier Transform Infrared Spectroscopy) instrument. The linear transmittance of the infrared transmission spectrum is converted based on the Lambert-Beer law so that it is 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 greater than or equal to a predetermined value. The wavelength bandwidth may be the wavelength bandwidth in which the linear transmittance is continuously greater than or equal to a predetermined value, or it may be the sum of the wavelength bandwidths in which the linear transmittance is continuously and intermittently greater than or equal to a predetermined value. That is, the wavelength bandwidth is the sum of the wavelength bandwidths in the target wavelength band where the linear transmittance is greater than or equal to a predetermined value. Therefore, if the linear transmittance is intermittently greater than or equal to a predetermined value, the wavelength bandwidths in which the linear transmittance is greater than or equal to a predetermined value may be far apart in the target wavelength band. It is preferable that the wavelength bandwidth is the wavelength bandwidth in which the linear transmittance is continuously greater than or equal to a predetermined value.

[0031] In the target wavelength band from 3 μm to 10 μm, the wavelength bandwidth in which the linear transmittance per 1 mm thickness of structure 1 continuously exceeds 10% may be 0.1 μm or more. Such 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. Furthermore, 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. Furthermore, 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 from 3 μm to 5 μm, 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 is, for example, 100%.

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

[0033] Furthermore, in the wavelength range of 3.8 to 4.4 μm, the average value of linear transmittance per 1 mm thickness of structure 1 may exceed 20%, 30%, 40%, 50%, or 60%. Also, throughout the entire wavelength range of 3.8 to 4.4 μm, the average value of linear transmittance per 1 mm thickness of structure 1 may exceed 20%, 30%, 40%, 50%, or 60%.

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

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

[0036] Weight loss 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] Structure 1 may be an infrared transmission filter. By using Structure 1 as an infrared transmission filter, it is possible to provide an infrared detection device and a light-emitting device that can suppress diffuse reflection of infrared light due to pores. If Structure 1 is a single layer that can transmit light in a specific infrared region, it is possible to transmit specific infrared light without stacking multiple dielectrics, as in an interference filter, or by providing a separate light-shielding filter to improve sensor sensitivity.

[0038] The thickness t of structure 1 is 10 μm or more. Structure 1 in this embodiment is formed by a pressurized heating method, as will be described later. Therefore, a bulk body with a thickness of 10 μm or more can be easily formed without having to laminate thin films to form structure 1. The thickness of structure 1 may be 100 μm or more, 500 μm or more, 1 mm or more, or 1 cm or more. There is no particular upper limit to the thickness of structure 1, but for example it may be 50 cm.

[0039] When 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 applied, it becomes possible to incident light rays perpendicularly on the dielectric multilayer bandpass filter, thereby canceling the light ray incidence angle dependence of the dielectric multilayer bandpass filter. Furthermore, a microstructure having an anti-reflective function may be formed on the surface of structure 1.

[0040] As described above, structure 1 comprises a base material 10 containing a continuous phase 11 of polycrystalline complex fluoride containing alkali metals. Structure 1 contains 85% by mass or more of inorganic material, 50% by mass or more of polycrystalline complex fluoride, the porosity of structure 1 is 30% or less, the median pore size of structure 1 is 500 nm or less, and the thickness of structure 1 is 10 μm or more.

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

[0042] [Infrared detection device] Next, the infrared detection device 100 according to this embodiment will be described with reference to Figure 3. As shown in Figure 3, the infrared detection device 100 includes the structure 1 described above. The infrared detection device 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 the substrate 130 using die bonding material 131. The infrared detection element 110 and the IC element 120 are electrically connected to each other by wire 140. In addition, the infrared detection element 110 is connected to an electrical circuit wiring (not shown) on the substrate 130 by wire 140.

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

[0045] The IC element 120 includes an amplification circuit that amplifies the electrical signal output from the infrared detection element 110, and a detection circuit that determines the presence of a flame when the electrical signal amplified by the amplification circuit exceeds a threshold.

[0046] The metal case 150 is attached to the substrate 130. The metal case 150 surrounds 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 positioned opposite the infrared detection element 110, and the infrared detection element 110 is provided on the substrate 130 to receive infrared light that has passed through the structure 1. The side wall 152 connects the edge of the top wall 151 and the edge of the substrate 130.

[0047] Infrared rays emitted from flames or other sources pass through structure 1 and are received by the infrared detection element 110. The infrared detection element 110 outputs an electrical signal to IC element 120 according to the amount of infrared light received. IC element 120 determines whether a flame is present 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] Furthermore, gas molecules such as inorganic gases like SO2, CO2, PH3, N2O, and NO have characteristic absorption properties in the mid-infrared region. These gas molecules also emit corresponding infrared radiation at high temperatures. Therefore, the structure 1 according to this embodiment is not limited to CO2, but can also be used as a sensor for gases that have characteristic absorption properties in the infrared region. Specifically, the structure 1 according to this embodiment is useful as an infrared-transmitting window because it has high infrared transmittance.

[0049] In this embodiment, an example of using the infrared detection device 100 as a flame sensor for detecting flames has been described, but the applications of the infrared detection device 100 are not limited to this form. The infrared detection device 100 can also be used as a motion sensor, biosensor, security sensor, gas sensor, non-contact thermometer, solid-state imaging device, or camera module, etc.

[0050] [Light-emitting device] Next, the light-emitting device 200 according to this embodiment will be described with reference to Figure 4. As shown in Figure 4, the light-emitting device 200 includes the structure 1 described above. 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 is equipped with a structure 1, a portion of the infrared radiation emitted from the light source 210 can be cut off by the structure 1. Therefore, according to the light-emitting device 200 of this embodiment, it is possible to emit light having a specific wavelength. The light-emitting device 200 can be used, for example, as a light-emitting device for gas detection, an inspection light-emitting device, a light-emitting device for surveillance cameras, a light-emitting device for hair removal, a light-emitting device for curing infrared-curable resins, and the like.

[0052] [Method for manufacturing the structure] (First Embodiment) Next, a method for manufacturing the structure 1 according to the first embodiment will be described. The structure 1 can be manufactured by pressurizing and heating a raw material containing complex fluoride particles. By using such a pressurized heating method, the complex fluoride particles deform and bond with each other, thereby forming a structure 1 with low porosity. The raw material containing fluoride particles may include a step of generating multiple complex fluoride particles, a step of separating them, a step of heating, and a step of adding water.

[0053] In the process of producing multiple complex fluoride particles, specifically, complex fluoride particles are prepared by first mixing and reacting a primary metal compound, which is an alkali metal fluoride, with a secondary metal compound that is different from the fluoride. The method of mixing the alkali metal fluoride and the secondary metal compound is not particularly limited and may be dry or wet mixing. These solutions may be mixed by adding the secondary metal compound solution to the alkali metal fluoride solution, or by adding the alkali metal fluoride solution to the secondary metal compound solution. Alternatively, the two solutions may be mixed simultaneously in equal amounts using a microfluidic channel or the like. As a solvent, for example, water can be used.

[0054] The concentration of the mixture of alkali metal fluoride and metallic compound can be adjusted as appropriate. The concentration of alkali metal fluoride may be 100 mM or higher, or 200 mM or higher. The concentration of alkali metal fluoride may be 1000 mM or lower. The concentration of metallic compound may be 20 mM or higher, or 40 mM or higher. The concentration of metallic compound may be 200 mM or lower. As the concentrations of these raw materials increase, the particle size tends to decrease, thus improving the permeability of structure 1.

[0055] Examples of alkali metals contained in alkali metal fluorides include lithium, sodium, potassium, rubidium, and cesium. Specifically, alkali metal fluorides 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 secondary metal compound is at least one selected from the group consisting of metal chlorides, metal nitrates, metal sulfates, and metal organic acid salts, and may include metal salts other than metal fluorides. The metal included in the secondary metal compound may be at least one selected from the group consisting of alkaline earth metals, aluminum, gallium, indium, zinc, and yttrium. The secondary metal compound may include, for example, aluminum chloride.

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

[0058] In the heating process, the separated complex fluoride particles are heated to 200°C or higher. By heating 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 structure 1 is reduced, and the transmittance of 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 more, 1 hour or more, or 1.5 hours or more. Furthermore, the heating time of the complex fluoride particles may be 24 hours or less, 12 hours or less, 6 hours or less, or 3 hours or less.

[0059] In the method for producing complex fluoride powder, the complex fluoride particles may be separated by removing by-products as needed, and then dried. The drying temperature is not particularly limited, but can be set at 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. Alternatively, 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. Alternatively, 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 materials may contain hydrated water in addition to the complex fluoride. Furthermore, the raw materials may contain by-products such as elemental 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 mold. After filling the mold with the raw material, the mold may be heated if necessary. Then, by applying pressure to the raw material inside the mold, the inside of the mold becomes high-pressure. At this time, the complex fluoride particles become densified and simultaneously bond with each other.

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

[0063] Then, the molded body can be removed from the inside of the mold to obtain structure 1. By heating and pressurizing a raw material containing polyfluoride particles that contain at least one of hydroxyl groups and water molecules, it is thought that the polyfluoride particles react with each other via hydroxyl groups or water molecules to form a continuous phase 11 of polycrystalline polyfluoride containing alkali metals. This makes it possible to form the structure 1 described above.

[0064] Through the pressurized and heated reaction described above, a structure 1 with a dense structure can be obtained. Another method for forming an aggregate of inorganic particles is to press only inorganic particle powder to form a compact, and then sinter it at a high temperature (e.g., 1700°C or higher). However, even if the inorganic particle compact is sintered at a high temperature, the resulting structure 1 will have many pores, resulting in insufficient mechanical strength and insufficient transmittance due to light scattering. Furthermore, sintering inorganic particles at high temperatures requires precise temperature control, which increases manufacturing costs.

[0065] In contrast, the manufacturing method of this embodiment involves heating and pressurizing a raw material containing complex fluoride particles that include at least one of hydroxyl groups and water molecules, thereby obtaining a dense structure 1 with excellent permeability. Furthermore, since the manufacturing method of this embodiment can be obtained by heating and pressurizing at 50°C to 300°C, precise temperature control is unnecessary, making it possible to reduce manufacturing costs.

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

[0067] (Second embodiment) Next, a method for manufacturing the structure 1 according to the second embodiment will be described. The structure 1 can also be manufactured by pressurizing and heating a raw material containing primary fluoride particles containing alkali metals and secondary fluoride particles containing metals other than alkali metals. By using such a pressurized heating method, each fluoride particle bonds with each other while forming complex fluorides, making it possible to form a structure 1 with low porosity.

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

[0069] The secondary fluoride particles contain metallic elements different from alkali metals. The metallic elements different from alkali metals are 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 metallic elements different from alkali metals may include at least one metal selected from the group consisting of magnesium, calcium, strontium, barium, aluminum, gallium, indium, zinc, and yttrium. The secondary fluoride particles may contain at least one metallic fluoride selected from the group consisting of magnesium fluoride (MgF2), calcium fluoride (CaF2), strontium fluoride (SrF2), barium fluoride (BaF2), aluminum fluoride (AlF3), gallium fluoride (GaF3), indium fluoride (InF3), yttrium fluoride (YF3), and zinc fluoride (ZnF2).

[0070] Next, a solvent is added to the raw material containing the primary fluoride particles and the secondary fluoride particles. The solvent is not particularly limited, but for example, a solvent capable of dissolving some of the primary and secondary 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 subjected to pressure and heating in the same manner as in the above embodiment to form structure 1. The first fluoride particles and the second fluoride particles react in the solvent when subjected to pressure and heating to form a continuous phase 11 of a polycrystalline complex fluoride containing alkali metals. This allows for the formation of the structure 1 described above.

[0072] As described above, the method for manufacturing the structure 1 according to this embodiment includes a step of pressurizing and heating raw materials including a first fluoride containing an alkali metal, a second fluoride containing a metal other than an alkali metal, and water. According to the method for manufacturing the structure 1 according to this embodiment, the above-described structure 1 can be manufactured by a simple low-temperature process.

[0073] (Third embodiment) Next, a method for manufacturing the structure 1 according to the third embodiment will be described. The structure 1 can also be manufactured by pressurizing and heating a raw material containing the complex fluoride particles obtained by the method for manufacturing the structure 1 according to the first embodiment, and the first fluoride particles and second fluoride particles described in the second embodiment.

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

[0075] A raw material containing primary fluoride particles and secondary fluoride particles can form structure 1 by pressurizing and heating it, similar to the embodiment described above. The primary fluoride particles and secondary fluoride particles react in the solvent when pressurized and heated, bonding with each other while forming a complex fluoride. Furthermore, the complex fluoride particles bond with each other while deforming. This allows for the formation of the structure 1 described above.

[0076] As described above, the method for manufacturing the structure 1 according to this embodiment includes a step of pressurizing and heating a raw material containing at least one of a primary fluoride containing an alkali metal, a secondary fluoride containing a metal other than an alkali metal, water, and a double fluoride. According to the method for manufacturing the structure 1 according to this embodiment, the above-described structure 1 can be manufactured by a simple low-temperature process.

[0077] In other words, as described in the first to third embodiments, the method for manufacturing the structure 1 includes a step of pressurizing and heating a raw material containing at least one of a primary fluoride containing an alkali metal, a secondary fluoride containing a metal other than an alkali metal, water, and a double 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 1 contains 85% by mass or more of inorganic material, the structure 1 contains 50% by mass or more of polycrystalline double fluoride, the porosity of the structure 1 is 30% or less, the median pore diameter of the structure 1 is 500 nm or less, and the thickness of the structure 1 is 10 μm or more. According to the method for manufacturing the structure 1 according to these embodiments, the above-described structure 1 can be manufactured by a simple low-temperature process. [Examples]

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

[0079] (Example 1) First, sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade) and aluminum fluoride (AlF3) powder (High Purity Chemical Laboratory) were prepared. Next, the sodium fluoride powder and aluminum fluoride powder were mixed in a pot mill to a molar ratio of 3:1. Then, using an agate mortar and pestle, 20% by weight of ion-exchanged water relative to the total amount of powder was added and mixed to obtain a mixed powder.

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

[0081] (Example 2) First, sodium hexafluoroaluminate (Na3AlF6) was synthesized. Specifically, 32 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 4 mmol of aluminum chloride (AlCl3·6H2O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 100 mL of H2O were mixed and stirred at 25°C for 1 hour. This stirred solution was filtered by suction 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 single-phase Na3AlF6 powder.

[0082] In addition, sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade) and aluminum fluoride (AlF3) powder (High Purity Chemical Laboratory) were prepared. Next, the sodium fluoride powder, aluminum fluoride powder, and Na3AlF6 powder were mixed using an agate mortar and pestle in a molar ratio of 3:1:9, with 20% by weight of ion-exchanged water added to the total amount of powder, to obtain a mixed powder.

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

[0084] (Example 3) First, sodium hexafluoroaluminate (Na3AlF6) was synthesized. Specifically, 32 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 4 mmol of aluminum chloride (AlCl3·6H2O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 100 mL of H2O were mixed and stirred at 25°C for 1 hour. This stirred solution was filtered by suction 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 single-phase Na3AlF6 powder. Figure 5 shows an SEM image of the synthesized Na3AlF6 powder.

[0085] Next, Na3AlF6 powder was placed inside a cylindrical molding die (Φ12) with an internal space. The Na3AlF6 powder was then heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, the cylindrical test sample of this example was obtained.

[0086] (Example 4) First, K2NaAlF6 was synthesized. Specifically, 32 mmol of potassium fluoride (KF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 6 mmol of sodium chloride (NaCl) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 2 mmol of aluminum chloride (AlCl3·6H2O), and 20 mL of H2O were mixed and stirred at 25°C for 1 hour. This stirred solution was filtered by suction 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 single-phase K2NaAlF6 powder. Figure 6 shows an SEM image of the synthesized K2NaAlF6 powder.

[0087] Next, K2NaAlF6 powder was placed inside a cylindrical molding die (Φ12) with an internal space. The K2NaAlF6 powder was then heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, the cylindrical test sample of this example was obtained.

[0088] (Example 5) First, NaMgF3 was synthesized. Specifically, 48 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 12 mmol of magnesium chloride (MgCl2·6H2O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 100 mL of H2O were mixed and stirred at 80°C for 3 hours. This stirred solution was filtered by suction 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 single-phase NaMgF3 powder. Figure 7 shows an SEM image of the synthesized NaMgF3 powder.

[0089] Next, NaMgF3 powder was placed inside a cylindrical molding die (Φ12) with an internal space. The NaMgF3 powder was then heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, the cylindrical test sample of this example was obtained.

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

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

[0092] [Evaluation of test samples] For the test samples prepared as described above, we performed crystal structure analysis, pore observation, and measurements of porosity, pore size, and linear transmittance.

[0093] (Crystal structure analysis) Next, using a powder X-ray diffraction (XRD) apparatus, the powders obtained by grinding the test samples from Examples 1 to 5 were measured, and XRD patterns were acquired. These results are shown in Figures 8 to 12. Furthermore, the proportions of each component were determined by Rietveld analysis of the obtained XRD patterns. These results are shown in Tables 1 and 2. In Tables 1 and 2, the units of the values ​​in the upper row are mass%, and the units of the values ​​in parentheses in the lower row are volume%.

[0094] (Observation of stomata) First, the cross-section of each test sample was subjected to cross-section polishing (CP processing). Next, a scanning electron microscope (SEM) was used to observe secondary electron images and backscattered electron images of the cross-section of the test samples at magnifications of 10,000x or 2,000x. The secondary electron images and backscattered electron images of Examples 1 to 5 and Comparative Examples 1 to 2 are shown in Figures 13 to 30.

[0095] (Measurement of porosity and pore size) Next, the backscattered electron images obtained as described above were binarized to clarify the pore areas. Then, the porosity was obtained by calculating the area ratio of the pore areas from the binarized images. The porosity was calculated for pores with 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. Furthermore, the pore diameter was defined as the cumulative value of the pore diameter distribution based on area at 10% (d 10 ), 50%(d 50 ) and 90% (d 90 The calculations were performed for the case of ). These calculation results are shown in Table 4.

[0096] (Linear transmittance) Each test sample was measured using the transmission method with an FT-IR instrument to obtain infrared transmission spectra. These results are shown in Figures 31 to 33. Note that the linear transmittance of the infrared transmission spectra has been converted according to the Lambert-Beer law so that it represents the linear transmittance at a thickness of 1 mm.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [Table 4]

[0101] As shown in Table 1, the test sample of Example 1 contained NaF and AlF3, which are the same components as the raw materials, and Na3AlF6 produced by a hydrothermal reaction. In Example 1, since particulate NaF and AlF3 were used as raw materials, it is possible that the center of the particles remained unreacted. On the other hand, the test sample of Example 2 contained a small amount of Na5Al3F in addition to Na3AlF6. 14 It was found that it contains [something].

[0102] As shown in Table 2, the test sample of Example 3 contained a small amount of Na5Al3F in addition to Na3AlF6. 14 It was found that the following substances were present. The sample in Example 4 contained 100% by mass of K2NaAlF6, the same as the raw material. Similarly, the sample in Example 5 also contained 100% by mass of NaMgF3, the same as the raw material.

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

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

[0105] These results indicate that the test samples of Examples 1 to 5 had higher linear transmittance compared to the test samples of Comparative Examples 1 and 2. This is likely because, in the test samples of Examples 1 to 5, the median pore size of the structure was 500 nm or less, resulting in less light scattering due to coarse pores.

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

[0107] Next, test samples were prepared by molding under pressure and heating, and by pressurizing and firing, as described below.

[0108] (Example 6) A cylindrical test sample for this example was obtained using the same process as in Example 3.

[0109] (Example 7) A cylindrical test sample for this example was obtained using the same process as in Example 1.

[0110] (Comparative Example 3) The Na3AlF6 powder synthesized in Example 6 was placed inside a molding die. Next, the Na3AlF6 powder was pressurized at room temperature (25°C) and 50 MPa. The resulting cylindrical compact was then calcined at 800°C for 2 hours.

[0111] (Comparative Example 4) The mixed powder prepared in Example 7 was placed inside a molding die. Next, the mixed powder was pressurized at room temperature (25°C) and 50 MPa. The resulting cylindrical compact was then fired at 800°C for 2 hours.

[0112] (Structural observation) The fracture surfaces of the test samples from Examples 6-7 and Comparative Examples 3-4 were observed using a scanning electron microscope (SEM) at magnifications of 10,000x or 2,000x. These secondary electron images are shown in Figures 34-41. Gold sputtering was applied to the observation surfaces of the test samples.

[0113] The pores of the test sample in Comparative Example 3 were larger than those of the test sample in Example 6. Similarly, the pores of the test sample in Comparative Example 4 were larger than those of the test sample in Example 7. These results indicate that the test samples molded by pressurization and heating are denser than the test samples molded by pressurization and firing.

[0114] Next, in order to confirm the effect of heat treatment on Na3AlF6 powder, the following structures were fabricated according to the examples below.

[0115] (Example 8) A cylindrical test sample for this example was obtained using the same process as in Example 3.

[0116] (Example 9) First, sodium hexafluoroaluminate (Na3AlF6) was synthesized. Specifically, 24 mmol of sodium fluoride (NaF) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), 3 mmol of aluminum chloride (AlCl3·6H2O) powder (Fujifilm Wako Pure Chemical Industries, Ltd., reagent grade), and 100 mL of H2O were mixed and stirred at 28°C for 20 hours. This stirred solution was filtered by suction 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 ground in a mortar and pestle, and heat-treated in air at 300°C for 2 hours to obtain Na3AlF6 powder.

[0117] 10% by mass of water was added to heat-treated Na3AlF6 powder. Next, the hydrated Na3AlF6 powder was placed inside a cylindrical molding die (Φ12) with an internal space. The hydrated Na3AlF6 powder was then heated and pressurized at 180°C, 400 MPa, and for 20 minutes. In this way, the cylindrical test sample of this example was obtained.

[0118] (Example 10) Test samples were 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) Test samples were 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] (SEM image of Na3AlF6 powder) The Na3AlF6 powder obtained from the synthesis in Examples 8 to 11 after 2 hours of heat treatment was observed using a scanning electron microscope (SEM). These SEM images are shown in Figures 42 to 45.

[0121] (Crystal structure analysis) Using a powder X-ray diffraction (XRD) apparatus, the XRD patterns of the Na3AlF6 powder after 2 hours of heat treatment in each example were obtained. These results are shown in Figure 46.

[0122] (Observation of pores) Similar to the above, using a scanning electron microscope (SEM), the cross-section of the test sample was observed at a magnification of 10,000 times for secondary electron images and backscattered electron images. The secondary electron images and backscattered electron images of Example 9 are shown in FIGS. 47 and 48. The secondary electron images and backscattered electron images of Example 10 are shown in FIGS. 49 and 50. The secondary electron images and backscattered electron images of Example 11 are shown in FIGS. 51 and 52.

[0123] (Measurement of porosity and pore diameter) Similar to the above, the porosity was measured from the obtained backscattered electron images. The porosity was determined for pores with a pore diameter of 5 nm or more. The results are shown in Table 5. Also, the pore diameter was determined for the cases where the cumulative value of the pore diameter distribution based on area was 10% (d 10 ), 50% (d 50 ), and 90% (d 90 ). The calculated results 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 relative density of the structure was calculated by dividing the apparent density of the test sample by the density of cryolite (2.98 g / cm 3 ).

[0125] (Linear transmittance) Each test sample was measured by the transmission method using an FT-IR device to obtain infrared transmission spectra. These results are shown in FIGS. 53 to 55. The linear transmittance of the infrared transmission spectrum is converted based on Lambert-Beer's 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 thermogravimetric (TG) apparatus. Specifically, 15-20 mg of test sample was placed in an aluminum container and heated from 30°C to 560°C at a rate of 10°C / min while dry air was introduced at a rate of 20 mL / min. The first weight loss rate from 30°C to 200°C and the second weight loss rate from 200°C to 500°C were then 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, Figure 56, and Figure 57.

[0127] [Table 5]

[0128] [Table 6]

[0129] As shown in Figure 46, when the heat treatment temperature is 300°C to 500°C, the different phase (Na5Al3F 14 ) was present. However, in all examples, it was confirmed that the main phase was Na3AlF6 and the structure contained at least 95% by mass of polycrystalline Na3AlF6.

[0130] As shown in Table 5, the median pore size (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 Figure 54, all structures had a relative density of 70% or more, confirming their denseness. These results confirm that the structures are dense.

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

[0132] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0133] (Technical 1) A structure comprising a base material containing a continuous phase of polycrystalline polyfluoride containing an alkali metal, wherein the structure contains 85% by mass or more of inorganic material, the structure contains 50% by mass or more of the polycrystalline polyfluoride, the porosity of the structure is 30% or less, the median pore diameter of the structure is 500 nm or less, and the thickness of the structure is 10 μm or more.

[0134] This configuration makes the structure less soluble in water, and allows it to be manufactured using a simple low-temperature process. Therefore, it is 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 mainly comprises 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 can improve infrared light transmission. Therefore, they are suitable for applications such as infrared transmission windows for gas sensors and flame detection sensors.

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

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

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

[0139] (Technology 6) A 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 by hydroxyl groups and water molecules. As a result, infrared transmittance can be further increased.

[0140] (Technology 7) An infrared transmission filter, the structure described in any one of Technologies 1 to 6. This configuration makes it possible to provide an infrared detection device and a light-emitting device that can suppress diffuse reflection of infrared light by pores.

[0141] (Technology 8) An infrared detection device comprising the structure described in any one of Technologies 1 to 7. This configuration makes it possible to provide an infrared detection device that can suppress diffuse reflection of infrared light by the pores of the structure.

[0142] (Technology 9) A light-emitting device comprising the structure described in any one of Technologies 1 to 7. This configuration makes it possible to provide a light-emitting device that can suppress diffuse reflection of infrared light by the pores of the structure.

[0143] (Technical 10) A method for manufacturing a structure, comprising the step of pressurizing and heating a raw material containing at least one of a primary fluoride containing an alkali metal, a secondary fluoride containing a metal other than an alkali metal, water, and a double 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 inorganic material, the structure contains 50% by mass or more of the polycrystalline form of the double fluoride, the porosity of the structure is 30% or less, the median pore diameter of the structure is 500 nm or less, and the thickness of the structure is 10 μm or more. This allows the structure to be manufactured 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 this embodiment has been described above, this embodiment is not limited to these, and various modifications are possible within the scope of the gist of this embodiment. [Industrial applicability]

[0146] This disclosure provides a structure suitable for applications such as infrared-transmitting windows for gas sensors and flame detection sensors, as well as an infrared detection device and a light-emitting device using the same. Furthermore, this disclosure provides a method for manufacturing the above structure, which can be produced by a simple low-temperature process. [Explanation of symbols]

[0147] 1 structure 10 Base material 11 Continuous Phases 100 Infrared detection device 200 Light-emitting devices

Claims

1. The structure comprises a base material containing a continuous phase of polycrystalline alkali metal-containing complex fluorides, The aforementioned structure contains 85% by mass or more of inorganic material, The structure contains 50% by mass or more of the polycrystalline compound of the polyfluoride, The porosity of the aforementioned structure is 30% or less. The median pore size of the aforementioned structure is 500 nm or less. The thickness of the aforementioned structure is 10 μm or more. The aforementioned complex fluoride mainly contains fluorine, the aforementioned alkali metal, and an additional metal. The alkali metal includes sodium, or sodium and potassium. The additional metal includes at least one metal selected from the group consisting of magnesium and aluminum. A structure in which, within the target wavelength band of 3 μm to 5 μm, the wavelength bandwidth in which the linear transmittance continuously exceeds 50% is 0.1 μm or more.

2. The structure comprises a base material containing a continuous phase of polycrystalline alkali metal-containing complex fluorides, The aforementioned structure contains 85% by mass or more of inorganic material, The structure contains 50% by mass or more of the polycrystalline compound of the polyfluoride, The porosity of the aforementioned structure is 30% or less. The median pore size of the aforementioned structure is 500 nm or less. The thickness of the aforementioned structure is 10 μm or more. The aforementioned complex fluoride mainly contains fluorine, the aforementioned alkali metal, and an additional metal. The alkali metal includes sodium, or sodium and potassium. The additional metal includes at least one metal selected from the group consisting of magnesium and aluminum. A structure in which the weight loss rate when the structure is heated from 200°C to 500°C is 0.5% or less.

3. The structure comprises a base material containing a continuous phase of polycrystalline alkali metal-containing complex fluorides, The aforementioned structure contains 85% by mass or more of inorganic material, The structure contains 50% by mass or more of the polycrystalline compound of the polyfluoride, The porosity of the aforementioned structure is 30% or less. The median pore size of the aforementioned structure is 500 nm or less. The thickness of the aforementioned structure is 10 μm or more. The aforementioned complex fluoride mainly contains fluorine, the aforementioned alkali metal, and an additional metal. The alkali metal includes sodium, or sodium and potassium. The additional metal includes at least one metal selected from the group consisting of magnesium and aluminum. A structure that acts as an infrared transmission filter.

4. The structure according to any one of claims 1 to 3, wherein the complex fluoride mainly comprises fluorine, the alkali metal, and aluminum.

5. An infrared detection device comprising a structure, The aforementioned structure comprises a base material including a continuous polycrystalline phase of alkali metal-containing polyfluoride, The aforementioned structure contains 85% by mass or more of inorganic material, The structure contains 50% by mass or more of the polycrystalline compound of the polyfluoride, The porosity of the aforementioned structure is 30% or less. The median pore size of the aforementioned structure is 500 nm or less. The thickness of the aforementioned structure is 10 μm or more. The aforementioned complex fluoride mainly contains fluorine, the aforementioned alkali metal, and an additional metal. The alkali metal includes sodium, or sodium and potassium. An infrared detection device wherein the additional metal includes at least one metal selected from the group consisting of magnesium and aluminum.

6. The infrared detection device according to claim 5, wherein the complex fluoride mainly comprises fluorine, the alkali metal, and aluminum.

7. A light-emitting device comprising a structure, The aforementioned structure comprises a base material including a continuous polycrystalline phase of alkali metal-containing polyfluoride, The aforementioned structure contains 85% by mass or more of inorganic material, The structure contains 50% by mass or more of the polycrystalline compound of the polyfluoride, The porosity of the aforementioned structure is 30% or less. The median pore size of the aforementioned structure is 500 nm or less. The thickness of the aforementioned structure is 10 μm or more. The aforementioned complex fluoride mainly contains fluorine, the aforementioned alkali metal, and an additional metal. The alkali metal includes sodium, or sodium and potassium. The light-emitting device wherein the additional metal includes at least one metal selected from the group consisting of magnesium and aluminum.

8. The light-emitting device according to claim 7, wherein the complex fluoride mainly comprises fluorine, the alkali metal, and aluminum.

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