Method for manufacturing nayf4 sintered body

Abstract

To provide a method for effectively manufacturing NaYF4 sintered bodies with high relative density.SOLUTION: The present invention provides a method for manufacturing a NaYF4 sintered body using a first mixed powder and a second mixed powder, both of which are composed of NaF powder and YF3 powder, where the method comprises a process of preparing a precursor molded body 12 by subjecting the first mixed powder, in which the molar ratio (NaF / YF3)A of NaF of NaF powder and YF3 of YF3 powder is 0.75 to 1.20, to press forming, a process of preparing a coated article 10 by coating the precursor molded body 12 with the second mixed powder 14, in which the molar ratio (NaF / YF3)B of NaF of the NaF powder and YF3 of the YF3 powder is 0.17 or more and less than 0.75, and a process of heating the obtained coated article 10, in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a NaYF4 sintered body having a high relative density. [Background technology]

[0002] Conventionally, NaYF4 has been used as a raw material for manufacturing mother crystals of phosphors, solid electrolytes for fluoride ion secondary batteries, etc. For example, Patent Document 1 discloses a touch screen cover comprising an upper surface facing the user of a touch screen, a lower surface facing the touch screen, and at least one ultraviolet emitting device or material for emitting energy having a wavelength in the range of 100 to 400 nm, which is in optical communication with the upper surface, and it is described that the ultraviolet emitting device is selected from an ultraviolet light emitting diode or an ultraviolet emitting material, and the ultraviolet emitting material can be a composition including at least one phosphor (such as NaYF4) capable of converting initial electromagnetic energy (A) into different electromagnetic energy (B). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-521417 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to apply metal fluorides to phosphors and battery components, it is necessary to create bulk materials. However, multi-element fluoride ceramics containing two or more elements are difficult to sinter, and currently, only powder molded materials are used. Therefore, there is a demand for the development of process technology for dense sintering of metal fluorides. An object of the present invention is to provide a method for producing a NaYF4 sintered body having a high relative density. [Means for solving the problem]

[0005] The inventors have demonstrated that by covering a precursor molded body consisting of NaF powder and YF3 powder, prepared under heating conditions in a molar ratio that results in the formation of NaYF4, with a mixed powder (mixed powder of eutectic composition) of NaF powder and YF3 powder prepared in a molar ratio (NaF / YF3) lower than the molar ratio (NaF / YF3) in the precursor molded body and then heat treating the same, a NaYF4 sintered body with high relative density can be obtained. The present invention is illustrated below. 1. A method for producing a NaYF4 sintered body using a first mixed powder and a second mixed powder each containing a NaF powder and a YF3 powder, The molar ratio of NaF in the NaF powder and YF3 in the YF3 powder (NaF / YF3) A A step of subjecting the first mixed powder having a molecular weight of 0.75 to 1.20 to press molding to prepare a precursor molded body; The precursor compact was mixed with the NaF powder and the YF3 powder in a molar ratio of NaF / YF3. B a step of coating the surface of the coated article with a second mixed powder having a refractive index of 0.17 or more and less than 0.75; heating the coating; A method for producing a NaYF4 sintered body, comprising the steps of: 2. The method for producing a NaYF4 sintered body according to item 1, wherein the heating temperature of the coating is 600°C to 1000°C. 3. A NaYF4 sintered body obtained by the method described in item 1 above, characterized in that the NaYF4 sintered body has a relative density of 95% or more. Effect of the Invention

[0006] According to the method for producing a NaYF4 sintered body of the present invention, a NaYF4 sintered body having a high relative density of 70% or more can be efficiently produced. The NaYF4 sintered body of the present invention has a relative density of 95% or more, and is therefore suitable as a manufacturing material for fluoride ion secondary batteries. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a schematic diagram showing an example of a coating before heat treatment in the method for producing a NaYF4 sintered body of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing another example of a coating before heat treatment in the method for producing a NaYF4 sintered body of the present invention. [Diagram 3] 1 is an X-ray diffraction image of the sintered bodies obtained in Examples 1 and 2. [Figure 4] 1 is an image showing the inside of the sintered body obtained in Example 1. [Diagram 5] 1 shows X-ray diffraction images of the heat-treated products obtained in Comparative Examples 1, 2, and 3. [Figure 6] 2 is an image showing the inside of the sintered body obtained in Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the method for producing a NaYF4 sintered body of the present invention, a first mixed powder and a second mixed powder each containing a NaF powder and a YF3 powder are used, and the molar ratio of NaF in the NaF powder to YF3 in the YF3 powder (NaF / YF3) is A a step of subjecting a first mixed powder having a molar ratio of NaF of the NaF powder and YF3 of the YF3 powder (NaF / YF3) of 0.75 to 1.20 to press molding to prepare a precursor molded body (hereinafter referred to as the "first step"); B The method includes a step of coating the surface of the material with a second mixed powder having a refractive index of 0.17 or more and less than 0.75 to produce a coated article (hereinafter referred to as the "second step"), and a step of heating the obtained coated article (hereinafter referred to as the "third step").

[0009] The first step is a step of press-molding the first mixed powder to produce a precursor molded body. The first mixed powder has a molar ratio of NaF of the NaF powder and YF3 of the YF3 powder (NaF / YF3) A The molar ratio (NaF / YF3) is not particularly limited as long as it is 0.75 to 1.20. A is preferably 0.81 to 1.10. Since the precursor compact is to be converted into a NaYF4 sintered compact in the third step, the ideal composition of the first mixed powder is (NaF / YF3) A= 1, but since the present invention includes the second step, the precursor compact has a structure of (NaF / YF3) A Even if the ratio is ≒ 1, a NaYF4 sintered body can be efficiently produced.

[0010] The method for preparing the first mixed powder used in the manufacture of the precursor compact is not particularly limited. The NaF powder and the YF3 powder used in the preparation of the first mixed powder are preferably fine particles, and although the size is not particularly limited, it is preferable to dry-grind them using a ball mill or the like to prepare the first mixed powder.

[0011] The precursor compact can be produced by subjecting the first mixed powder to a conventionally known press molding method. The shape and size of the precursor compact are not particularly limited. The load during press molding is usually 5 MPa or more.

[0012] The second step is a step of coating the precursor compact with a second mixed powder to produce a coating. The second mixed powder preferably has a composition near a eutectic temperature having a melting point lower than that of the first mixed powder, and the molar ratio of NaF in the NaF powder and YF3 in the YF3 powder (NaF / YF3) is B The molar ratio (NaF / YF3) is not particularly limited as long as it is 0.17 or more and less than 0.75. B is preferably 0.30 to 0.60.

[0013] The method for preparing the second mixed powder used in the production of the coating is not particularly limited. The NaF powder and the YF3 powder used in the preparation of the second mixed powder are preferably fine particles, and although the size is not particularly limited, it is preferable to dry-grind them using a ball mill or the like to prepare the second mixed powder.

[0014] The form of the coating according to the present invention is not particularly limited, and it is preferable that the coating is one in which at least 60%, preferably 80% or more of the surface area of ​​the precursor molded body is coated so as to be in contact with the second mixed powder (see Figures 1 and 2). The coated object 10 in FIG. 1 is produced by placing the precursor molded body 12 on a heat-resistant plate 16 made of a material (platinum, alumina, zirconia, etc.) that does not react with either the first mixed powder constituting the precursor molded body 12 or the second mixed powder coating the precursor molded body 12, and then forming a coating layer 14 made of the second mixed powder that covers the surface of the precursor molded body 12 by heating in the third step. FIG. 2 shows a base layer formed by spreading the second mixed powder, on which a precursor molded body 12 is placed, and further, a coating layer 14 is formed using the second mixed powder to cover the surface of this precursor molded body 12.

[0015] The third step is a step of heating the coating. The heating temperature of the coating is preferably 600°C or higher, more preferably 620°C or higher, because NaYF4 is efficiently produced and a sintered body is formed. The upper limit is preferably 1000°C, more preferably 800°C. The atmosphere during heating is not particularly limited, and may be air, an inert gas, or the like.

[0016] According to the method for producing a NaYF4 sintered body of the present invention, a NaYF4 sintered body having a relative density measured by a bulk density method of preferably 70% or more, more preferably 80% or more, and particularly preferably 95% or more can be produced. In addition, the obtained NaYF4 sintered body has a dense structure, so that it can be suitably used as a manufacturing material for a fluoride ion secondary battery.

[0017] The method for producing a NaYF4 sintered body of the present invention can be used to produce a NaYF4 sintered body doped with a rare earth element. For example, a precursor compact obtained by adding a rare earth metal fluoride to the first mixed powder and then molding the mixture can be used. Depending on the application of the sintered body, both a rare earth metal fluoride and an alkaline earth metal fluoride may be added to the first mixed powder.

[0018] In the present invention, the molar ratio (NaF / YF3) in the first mixed powder and the second mixed powder is set to a specific range, particularly (NaF / YF3) A >(NaF / YF3) BHowever, (NaF / YF3) A and (NaF / YF3) B Even when both are 0.75 to 1.20, a NaYF4 sintered body with high relative density can be produced by the same method. A ≧(NaF / YF3) B and (NaF / YF3) A <(NaF / YF3) B Either is acceptable. EXAMPLES

[0019] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0020] Example 1 NaF powder manufactured by Kojundo Chemical Laboratory Co., Ltd. and YF3 powder manufactured by Kojundo Chemical Laboratory Co., Ltd. were pulverized and mixed using a ball mill so that the molar ratio (NaF / YF3) was 45 / 55. The resulting mixed powder (first mixed powder) was then uniaxially pressed under a load of 10 MPa to produce a powder compact (diameter: 20 mm, thickness: 1 mm, hereinafter referred to as "powder compact (M1)"). Thereafter, this powder compact (M1) was placed on a platinum plate and covered with a mixed powder (second mixed powder) obtained by pulverizing and mixing NaF powder and YF3 powder using a ball mill so that the molar ratio (NaF / YF3) was 35 / 65, to produce a coated object (see FIG. 1). Next, the platinum plate with the coating placed on it was placed in an electric furnace and heat-treated at 700°C for 2 hours in an air atmosphere. After that, it was allowed to cool, the powder of the coating layer was removed, and a sintered product of the powder compact (M1) (hereinafter referred to as "sintered product (S1)") was obtained. Then, X-ray diffraction measurement of the sintered product (S1) was performed (see Figure 3). From the X-ray diffraction image in Figure 3, it was found that the sintered product (S1) contained a trace amount of NaF, but was mainly composed of NaYF4.

[0021] The obtained sintered body (S1) was broken, and the microstructure inside the sintered body (S1) was observed by an electron microscope (see Fig. 4). From Fig. 4, it was found that the sintered body (S1) had a sintered structure of grains with facets measuring 2 to 3 µm. Moreover, the relative density of the sintered body (S1) was measured by the bulk density method and was found to be 97%.

[0022] Example 2 A sintered body (hereinafter referred to as "sintered body (S2)") was obtained by the same operation as in Example 1, except that the heat treatment temperature of the coating was changed from 700°C to 600°C. From the X-ray diffraction image in FIG. 3, it was found that the sintered body (S2) was mainly composed of NaYF4. In addition, the relative density of the sintered body (S2) was 83%.

[0023] Comparative Example 1 A powder compact (hereinafter referred to as "powder compact (M2)") was produced in the same manner as in Example 1, using NaF powder and YF3 powder so that the molar ratio (NaF / YF3) was 55 / 45. Next, this powder compact (M2) was heat-treated at 600°C for 2 hours in a nitrogen gas atmosphere. Thereafter, it was allowed to cool to obtain a heat-treated product of the powder compact (M2) (hereinafter referred to as "heat-treated product (T1)"). Then, X-ray diffraction measurement of the heat-treated product (T1) was performed (see FIG. 5). From the X-ray diffraction image in FIG. 5, it was found that the heat-treated product (T1) contained YOF but was mainly composed of NaYF4.

[0024] The obtained heat-treated product (T1) was broken, and the microstructure inside the heat-treated product (T1) was observed by an electron microscope (see FIG. 6). From FIG. 6, it was found that the heat-treated product (T1) did not have a sintered structure, but had a granular structure. The relative density of the heat-treated product (T1) was 62%.

[0025] Comparative Example 2 A heat-treated product (hereinafter, referred to as "heat-treated product (T2)") was obtained by the same operation as in Comparative Example 1, except that the heat treatment temperature of the powder compact (M2) was changed from 600°C to 700°C. From the X-ray diffraction image in Fig. 5, it was found that the heat-treated product (T2) was mainly composed of YOF, NaF, and NaYF4.

[0026] Comparative Example 3 A heat-treated product (hereinafter, referred to as "heat-treated product (T3)") was obtained by the same operation as in Comparative Example 1, except that the heat treatment temperature of the powder compact (M2) was changed from 600°C to 800°C. From the X-ray diffraction image in Fig. 5, it was found that the heat-treated product (T3) was mainly composed of YOF and NaF. [Industrial Applicability]

[0027] The NaYF4 sintered body according to the present invention is suitable as a manufacturing material for a fluoride ion secondary battery. [Explanation of symbols]

[0028] 10: Precursor molded body coating 12: Precursor compact made of first mixed powder 14: Coating layer made of second mixed powder 16: Heat resistant plate

Claims

1. Both were made of NaF powder and YF ３ The first mixed powder and the second mixed powder consisting of NaYF ４ A method for producing a sintered body, comprising the steps of: The NaF and YF powder ３ Powdered YF ３ Molar ratio (NaF / YF ３ ) Ａ a step of subjecting the first mixed powder having a molecular weight of 0.75 to 1.20 to press molding to prepare a precursor molded body; The precursor compact is mixed with NaF and YF of the NaF powder. ３ Powdered YF ３ Molar ratio (NaF / YF ３ ) Ｂ a step of coating the surface of the coated article with a second mixed powder having a refractive index of 0.17 or more and less than 0.75; heating the coating; NaYF ４ A method for manufacturing a sintered body.

2. 2. The NaYF according to claim 1, wherein the heating temperature of the coating is 600° C. to 1000° C. ４ A method for manufacturing a sintered body.

3. NaYF obtained by the method according to claim 1 ４ A sintered body having a relative density of 95% or more. ４ Sintered body.

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