Producing method of porous sinter

Abstract

To provide a method for efficiently producing a porous sinter using sintering oxide ceramic particles and a sintering aid.SOLUTION: The present invention provides a method for producing a porous sintered body 30, which includes a step of press-molding a mixed powder containing sintering ceramic oxide particles having a number average particle size of 1.2 to 25 μm and a narrow particle size distribution, and a sintering aid containing a metal fluoride, to produce a precursor molded body 12, and a step of irradiating the precursor molded body 12 with a laser. Alternatively, the present invention provides a method for producing a porous sintered body 30, which includes a step of press-molding a mixed powder containing sintering ceramic oxide particles having a number average particle size of 0.1 μm or more and less than 1.2 μm, and a sintering aid containing a metal fluoride, to produce a precursor molded body 12, and a step of irradiating the precursor molded body 12 with a laser.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a porous sintered body made of oxide ceramics by using a laser. [Background technology]

[0002] 2. Description of the Related Art Porous ceramic bodies are used for filtering, separating, concentrating, etc. in the fields of electronic materials, medicines, food, etc., or as catalyst carriers, lightweight jigs, soundproofing materials, etc.

[0003] The following techniques are known as methods for producing porous ceramics. For example, Patent Document 1 discloses a method for producing porous ceramics, which is characterized by sintering a compact of ceramic particles under a predetermined gas pressure to obtain a sintered body with a desired pore size distribution.

[0004] Patent Document 2 discloses a method for producing a high-alumina porous sintered body, which is characterized by coating alumina particles as aggregate with an alumina sol, molding the resulting product, and then firing the product at 1800° C. or higher in a reducing atmosphere. Patent document 3 also discloses a method for producing a porous ceramic sintered body, which includes a step of mixing ceramic powder with a plurality of first pore-forming materials having an aspect ratio of 5 or more and 500 or less, and a plurality of second pore-forming materials having an aspect ratio of 1 or more and 3 or less, a step of adding a binder to the mixture obtained in the mixing step and kneading while heating, a step of molding the molding material obtained in the kneading step, a step of removing the pore-forming materials and binder from the molded body obtained in the molding step, and a step of firing the degreased body obtained in the removing step.

[0005] In recent years, in order to shorten production times, methods of producing ceramic porous bodies by sintering ceramic materials using lasers have been investigated.

[0006] In Patent Document 4, the bulk density is 1.0 g / cm 3The present invention discloses a method for producing a porous ceramic sintered body, which includes the steps of: forming a ceramic powder to obtain a ceramic article; forming a carbon powder-containing layer on the surface of the ceramic article to obtain a laminate; and irradiating a laser onto the surface of the carbon powder-containing layer of the laminate to form a porous ceramic sintered portion. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 2-83277 [Patent Document 2] Japanese Patent Application Publication No. 2-149482 [Patent Document 3] JP 2014-227324 A [Patent Document 4] JP 2022-166681 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a method for efficiently producing a porous sintered body made of oxide ceramics. [Means for solving the problem]

[0009] The present invention is illustrated below. 1. A method for producing a porous sintered body, comprising the steps of: subjecting a mixed powder containing sintering oxide ceramic particles having a number average particle size of 1.2 to 25 μm and a narrow particle size distribution, and a sintering aid containing a metal fluoride, to press molding to produce a precursor molded body; and irradiating the precursor molded body with a laser. 2. A method for producing a porous sintered body, comprising the steps of press-molding a mixed powder containing sintering oxide ceramic particles having a number average particle size of 0.1 μm or more and less than 1.2 μm and a sintering aid containing a metal fluoride to produce a precursor molded body, and irradiating the precursor molded body with a laser. 3. The wavelength of the laser is 350-2500 nm and the output is 1-1000 W / cm 2 3. A method for producing a porous sintered body according to item 1 or 2, wherein 4. The above metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, titanium fluoride, 3. A method for producing a porous sintered body according to item 1 or 2, wherein the fluoride is at least one selected from the group consisting of niobium, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride. 5. A method for producing a porous sintered body according to item 1 or 2, wherein the content of the oxide ceramic particles for sintering and the sintering aid constituting the precursor compact is 90 to 97% by volume and 3 to 10% by volume, respectively, when the total of the two is taken as 100% by volume. Effect of the Invention

[0010] According to the method for producing a porous sintered body of the present invention, a porous sintered body having a uniform pore size can be efficiently produced according to the particle size of the oxide ceramic particles to be sintered. Such a porous sintered body can be used for filtration, separation, concentration, etc. in the fields of electronic materials, medicines, foods, etc., or as a catalyst carrier, lightweight jigs, soundproofing materials, etc. [Brief description of the drawings]

[0011] [Figure 1]FIG. 1 is a schematic diagram showing a method for producing a porous sintered body by irradiating a precursor molded body with a laser, in which (A) is an example of the laser irradiation process, (B) is the molded body after laser irradiation, and (C) is the porous sintered body after the non-laser irradiated portion has been removed. [Diagram 2] 1 is an image showing the inside of the sintered body (Q1) obtained in Comparative Example 1. [Diagram 3] This is an enlarged image of Figure 3. [Figure 4] 1 is an image for measuring the average particle size of α-alumina single crystal particles used in producing a sintered body in Example 1. [Diagram 5] This is a binarized image of FIG. [Figure 6] 1 is an image showing the inside of the porous sintered body (P1) obtained in Example 1. [Figure 7] This is an enlarged image of Figure 6. [Figure 8] 1 is an image for measuring the average particle size of α-alumina single crystal particles used in producing a sintered body in Example 2. [Figure 9] This is a binarized image of FIG. [Figure 10] 1 is an image showing the inside of the porous sintered body (P2) obtained in Example 2. [Figure 11] 1 is an image showing the inside of the porous sintered body (P3) obtained in Example 3. [Figure 12] 1 is an image showing the inside of the porous sintered body (P4) obtained in Example 4. [Figure 13] FIG. 13 is an enlarged image of FIG. [Figure 14] 1 is an image showing the inside of the porous sintered body (P5) obtained in Example 5. [Figure 15] FIG. 15 is an enlarged image of FIG. [Figure 16] 1 is an image showing the inside of the porous sintered body (P6) obtained in Example 6. [Figure 17] FIG. 17 is an enlarged image of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A first embodiment of the method for producing a porous sintered body of the present invention (hereinafter referred to as the "first invention") includes a step of press-molding a mixed powder containing sintering oxide ceramic particles having a number average particle size of 1.2 to 25 μm and a narrow particle size distribution and a sintering aid containing a metal fluoride to produce a precursor molded body (hereinafter referred to as the "precursor molded body (1)"), and a step of irradiating the precursor molded body (1) with a laser. A second embodiment of the method for producing a porous sintered body of the present invention (hereinafter referred to as the "second invention") includes a step of press-molding a mixed powder containing sintering oxide ceramic particles having a number average particle size of 0.1 μm or more and less than 1.2 μm and a sintering aid containing a metal fluoride to produce a precursor molded body (hereinafter referred to as the "precursor molded body (2)"), and a step of irradiating the precursor molded body (2) with a laser.

[0013] The sintering ceramic oxide particles and sintering aids used in the first and second inventions are shown below.

[0014] The oxide constituting the oxide ceramic particles for sintering is not particularly limited, and examples thereof include aluminum oxide, mullite, magnesium oxide, zinc oxide, titanium oxide, iron oxide, yttrium oxide, zirconium oxide, stabilized zirconia, and barium titanate.

[0015] The shape of the oxide ceramic particles for sintering is not particularly limited, and the particle shape may be a solid body, such as a sphere, an oval sphere, or a polyhedron.

[0016] The sintering aid is usually a solid powder, contains a metal fluoride, and may further contain conventionally known sintering aids (hereinafter referred to as "other sintering aids") depending on the type of oxide ceramic for sintering that constitutes the oxide ceramic particles for sintering, but usually consists of one or more types of metal fluorides.

[0017] Metal fluorides include calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, and Examples of fluoride include antimony, titanium fluoride, niobium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride, and lutetium fluoride. The above metal fluorides are treated with a compound having the general formula MF n In the case where M is a metal atom, the precursor compact (1) and the precursor compact (2) are produced using MF containing M different from the metal atom of the oxide ceramic for sintering that constitutes the oxide ceramic particle for sintering. n It is preferable to use:

[0018] The shape and size of the sintering aid are not particularly limited.

[0019] The ceramic oxide particles for sintering according to the first aspect of the invention must have a larger number average particle size and a narrower particle size distribution than the ceramic oxide particles for sintering according to the second aspect of the invention. The particle size distribution of the ceramic oxide particles for sintering according to the second aspect of the invention is not particularly limited. Here, the "oxide ceramic particles for sintering having a narrow particle size distribution" used in the preparation of the precursor molded body (1) is ideally a particle group with small variation in particle size, and means a particle group having a number average particle size of 1.2 to 25 μm and a standard deviation of 20% or less, as determined by measuring the particle sizes of 100 or more particles using a device capable of measuring particle size (electron microscope, particle size measuring device, etc.) with the attached analysis software or manually, and then calculating the average particle size per number (number average particle size) and standard deviation. When a precursor compact containing sintering oxide ceramic particles having a wide particle size distribution and a sintering aid is irradiated with a laser, a dense sintered body, rather than a porous one, tends to be obtained.

[0020] The manufacturing method of the precursor molded body (1) according to the first invention and the precursor molded body (2) according to the second invention is not particularly limited. Both can be manufactured by subjecting a mixed powder obtained by mixing oxide ceramic particles for sintering and a sintering aid in a preferred ratio to a conventionally known press molding method. The shape and size of each precursor molded body are not particularly limited. The load during press molding is usually 10 MPa or more.

[0021] The proportions of the sintering ceramic oxide particles and the sintering aid in each mixed powder used to produce the precursor molded body (1) and the precursor molded body (2) are preferably 90 to 97 volume % and 3 to 10 volume %, more preferably 92 to 96 volume % and 4 to 8 volume %, and even more preferably 93 to 95 volume % and 5 to 7 volume %, respectively, when the total of both is taken as 100 volume %, because a porous sintered portion is efficiently formed by irradiating the precursor molded body with a laser.

[0022] In the first and second inventions, after each precursor molded body is produced, it is irradiated with a laser. The type of laser to be irradiated onto the precursor molded body is not particularly limited, and a solid-state laser, a gas laser, a semiconductor laser, a fiber laser, etc. can be used. Among these, a fiber laser is preferred.

[0023] A fiber laser is a laser that is transmitted in a state in which a laser is confined in the fiber by generating an induced discharge in a core doped with a rare earth element or the like in an optical fiber. A device that oscillates a fiber laser may be connected to a device that oscillates another laser such as a solid-state laser to form a laser oscillation device with a higher output.

[0024] The laser irradiation conditions are appropriately selected depending on the type of ceramic constituting the oxide ceramic particles for sintering, the type of sintering aid, the ratio of the oxide ceramic particles for sintering and the sintering aid contained in the precursor compact, and the like.

[0025] The wavelength of the laser is not particularly limited and can be 300 to 10,000 nm, preferably 350 to 2,500 nm, and more preferably 500 to 1,500 nm. The laser oscillation operation may be either continuous wave or pulsed wave.

[0026] From the viewpoint of smooth sintering, the laser output is preferably 1 to 1000 W / cm 2 , more preferably 100 to 500 W / cm 2 It is.

[0027] In the present invention, the method of irradiating the precursor molded body with a laser is not particularly limited. When a large-area sintered portion is formed on the precursor molded body, a method of irradiating the precursor molded body while scanning it with a laser or changing the optical path via a light diffusion lens, or a method of irradiating the precursor molded body with a laser with a fixed optical path while moving the precursor molded body, can be applied.

[0028] When the precursor molded body is irradiated with a laser, the atmosphere is not particularly limited and may be air, nitrogen, argon, helium, or the like.

[0029] In addition, when irradiating the laser, the precursor molded body may be preheated as necessary. The preheating method is not particularly limited, and may be an infrared lamp, a halogen lamp, resistance heating, high-frequency induction heating, microwave heating, or the like.

[0030] In the first and second inventions, depending on the configuration of each precursor molding, laser irradiation of the precursor molding may cause a reaction between the oxide ceramic particles and the metal fluoride (or its decomposition products), and the reaction products may deposit on the surface of the porous sintered body or become interposed between the sintered oxide ceramic particles (at the interface).

[0031] FIG. 1 is a schematic diagram showing a laser irradiation step in the method for producing a porous sintered body according to the first and second aspects of the invention.

[0032] FIG. 1(A) is a schematic diagram of a porous sintered body manufacturing apparatus 10 that irradiates a laser oscillated from a laser light source 14 onto the surface of a precursor molded body 12 consisting of a precursor molded body (1) or precursor molded body (2) containing oxide ceramic particles for sintering and a sintering aid containing a metal fluoride. For example, when a laser having a wavelength of 350 to 2500 nm is irradiated onto an oxide ceramic for sintering and a metal fluoride, respectively, the energy absorption rate of the laser is higher for the metal fluoride than for the oxide ceramic, so that when the laser is irradiated onto the precursor molded body 12, the laser irradiated portion of the precursor molded body 12 instantly reaches a temperature at which the oxide ceramic for sintering can be sintered, and a porous sintered portion 16 is formed (see FIG. 1(B)). Thereafter, the non-irradiated portion 15 is removed to isolate the porous sintered portion 16, thereby obtaining a porous sintered body 20 (see FIG. 1(C)). Needless to say, when the entire surface of the precursor compact 12 in FIG. 1(A) is irradiated with a laser, the precursor compact 12 can be converted into a porous sintered body 20.

[0033] The inventors speculate that the mechanisms of formation of the porous sintered portion 16 are different between the first and second inventions, in which the number average particle diameters of the sintering oxide ceramic particles used to prepare the precursor compact 12 are different.

[0034] In the second invention, the sintering ceramic oxide particles contained in the precursor molded body (2) have a number average particle size of 0.1 μm or more and less than 1.2 μm and a large specific surface area, so that they are likely to come into close proximity (including contact) with the sintering aid in the precursor molded body (2), and it is believed that when the precursor molded body (2) is irradiated with a laser, the ceramic oxide particles react with the metal fluoride (or its decomposition product), forming pores while the reaction product undergoes grain growth, resulting in the formation of a porous body. In the second invention, it is preferable to use a pulsed laser.

[0035] On the other hand, in the first invention, the sintering ceramic particles contained in the precursor molded body (1) have a large number average particle diameter but are composed of particles with a narrow particle size distribution, so that the spatial volume of the voids formed by three, four or five adjacent particles in the precursor molded body (1) is larger than that in the precursor molded body (2) containing sintering ceramic oxide particles with a small number average particle diameter, and the variation in the volume of adjacent voids is small. When such a precursor molded body (1) is irradiated with a laser and reaches a sinterable temperature, it is considered that the spatial volume of the voids is not significantly reduced, and adjacent sintering ceramic oxide particles are easily connected to each other while leaving voids, and neck growth is likely to occur.

[0036] According to the method for producing a porous sintered body of the present invention, hole formation and sintering proceed in the depth direction from the surface of the precursor shaped body 12 irradiated with a laser, and depending on the type of sintering oxide ceramics contained in the precursor shaped body 12, the formed porous portion 16 has laser transparency, and as long as the laser attenuation does not increase, hole formation and sintering can proceed deep into the laser irradiated portion of the precursor shaped body 12. Therefore, by appropriately setting the laser irradiation conditions, a porous portion 16 or a porous sintered body 30 can be obtained (see Figs. 1(B) and (C)). EXAMPLES

[0037] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0038] In the following experiments, a fiber laser emitting a laser with a wavelength of 1070 nm was used to irradiate a disk-shaped molded body (outer diameter: 15 mm, thickness: 1.8 mm) consisting of α-alumina particles and yttrium fluoride powder (sintering aid) via a galvanometer mirror.

[0039] Comparative Example 1 "AA-3" (trade name, median particle size: 3.5 μm) and "AA-03" (trade name, median particle size: 0.40 μm) from the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. were mixed in a volume ratio of 7:3, and then this mixed powder was mixed with yttrium fluoride powder in a volume ratio of 95:5. Thereafter, this mixed raw material was subjected to uniaxial pressure molding under a load of 10 MPa to obtain a disk-shaped molded body (precursor molded body). Next, the laser power was increased to 1000W / cm 2 The entire surface of the precursor molded body was irradiated with laser while being scanned at a speed of 100 mm per second with a beam diameter of φ10 mm, to obtain a sintered body (hereinafter referred to as "sintered body (Q1)").

[0040] Figure 2 and its enlarged image, Figure 3, are images of the inside of the broken sintered body (Q1) photographed by an electron microscope. From these images, it was found that the sintered body (Q1) was a sintered body having a dense structure, and was not porous. In addition, since the grain boundary crystal phase was dispersed in the alumina crystal phase in Figure 3, an X-ray diffraction measurement was performed on the sintered body (Q1). From the X-ray diffraction image (not shown), it was found that this grain boundary crystal phase was Y3Al5O 12 (hereinafter referred to as "YAG") pattern.

[0041] Example 1 Except for using "AA-1.5" (product name) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. instead of the mixed powder of Comparative Example 1, the same operations as in Comparative Example 1, i.e., preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P1)"). In the catalogue for this product, the median particle size is stated to be 1.7 μm, but when the image in Fig. 4, which was taken at 2500 times magnification using a scanning electron microscope, was binarized (see Fig. 5), the particle size was measured from Fig. 5, and the number average particle size was calculated, which was 1.43 ± 0.256 μm. In addition, the standard deviation was 17%, indicating that the raw material particles have a narrow particle size distribution.

[0042] Figure 6 and its enlarged image in Figure 7 are images of the inside of the broken sintered body (P1) photographed with an electron microscope. These images show that the sintered body (P1) has many pores and is a porous sintered body.

[0043] Example 2 Except for using "AA-3" (product name) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. instead of the mixed powder of Comparative Example 1, the same operations as in Comparative Example 1, i.e., preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P2)"). In the catalogue for this product, the median particle size is stated to be 3.5 μm, but when the image in Fig. 8, which was taken at 2500 times magnification using a scanning electron microscope, was binarized (see Fig. 9), the particle size was measured from Fig. 9, and the number average particle size was calculated to be 3.12 ± 0.22 μm. In addition, the standard deviation was 7%, indicating that the raw material particles have a narrow particle size distribution.

[0044] Fig. 10 is an image of the inside of the broken sintered body (P2) photographed with an electron microscope. From this image, it was found that the sintered body (P2) had many pores and was a porous sintered body.

[0045] Example 3 Instead of the mixed powder of Comparative Example 1, "AA-3" (product name) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. was used, and a mixed raw material was used in which this single crystal particle was mixed with yttrium fluoride powder in a volume ratio of 90:10. Except for this, the same operations as in Comparative Example 1, i.e., the preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P3)").

[0046] Fig. 11 is an image of the inside of the broken sintered body (P3) photographed with an electron microscope. From this image, it was found that the sintered body (P3) had many pores and was a porous sintered body.

[0047] Example 4 Except for using "AA-18" (product name, median particle size in catalog: 20.3 μm) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. instead of the mixed powder of Comparative Example 1, the same operations as in Comparative Example 1, i.e., preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P4)").

[0048] When the sintered body (P4) was broken and the inside was photographed with an electron microscope, it was found to have many pores and to be a porous sintered body (see Figs. 12 and 13).

[0049] Example 5 Except for using "AA-03" (product name) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. instead of the mixed powder of Comparative Example 1, the same operations as in Comparative Example 1, i.e., preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P5)"). In the catalogue for this product, the median particle size is stated to be 0.40 μm, but when an image (not shown) taken at 20,000 times magnification using a scanning electron microscope was binarized (not shown) to measure the particle size and calculate the number average particle size, it was 0.31±0.13 μm. The standard deviation was 41%, indicating that the raw material particles had a wide particle size distribution.

[0050] The sintered body (P5) was broken and the inside was photographed with an electron microscope, revealing that it had many pores and was a porous sintered body (see Figs. 14 and 15).

[0051] Example 6 Except for using "AA-04" (product name, median particle size in catalog: 0.47 μm) of the "Advanced Alumina" series of α-alumina single crystal particles manufactured by Sumitomo Chemical Co., Ltd. instead of the mixed powder of Comparative Example 1, the same operations as in Comparative Example 1, i.e., preparation of a precursor molded body and laser irradiation, were performed to obtain a sintered body (hereinafter referred to as "sintered body (P6)").

[0052] The sintered body (P6) was broken and the inside was photographed with an electron microscope, revealing that it had many pores and was a porous sintered body (see Figs. 16 and 17). [Industrial Applicability]

[0053] According to the method for producing a porous sintered body of the present invention, a porous sintered body can be efficiently produced by irradiating a laser onto a precursor molded body containing sintering oxide ceramic particles having a specific number average particle size and a sintering aid. Such a porous sintered body can be used for filtration, separation, concentration, etc. in the fields of electronic materials, medicines, foods, etc., or as a catalyst carrier, lightweight jigs, soundproofing materials, etc. [Explanation of symbols]

[0054] 10: Porous sintered body manufacturing equipment 12: Precursor compact containing oxide ceramic particles for sintering and sintering aid 14: Laser light source 15: Non-sintered area (non-laser irradiated area) 16: Porous part (laser irradiated part) 20: Molded body after laser irradiation 30: Porous sintered body

Claims

1. A process of press-molding a mixed powder containing sintering oxide ceramic particles having a number average particle size of 1.2 to 25 μm and a narrow particle size distribution and a sintering aid containing a metal fluoride to produce a precursor molded body; and a step of irradiating the precursor molded body with a laser.

2. A process of press-molding a mixed powder containing sintering oxide ceramic particles having a number average particle size of 0.1 μm or more and less than 1.2 μm and a sintering aid containing a metal fluoride to produce a precursor molded body; and a step of irradiating the precursor molded body with a laser.

3. The wavelength of the laser is 350 to 2500 nm, and the output is 1 to 1000 W / cm ２ 3. The method for producing a porous sintered body according to claim 1 or 2,

4. The metal fluoride is calcium fluoride, barium fluoride, aluminum fluoride, scandium fluoride, yttrium fluoride, lanthanum fluoride, zinc fluoride, cobalt fluoride, lead fluoride, gallium fluoride, indium fluoride, silver fluoride, chromium fluoride, iron fluoride, nickel fluoride, hafnium fluoride, copper fluoride, bismuth fluoride, manganese fluoride, tin fluoride, antimony fluoride, titanium fluoride, The method for producing a porous sintered body according to claim 1 or 2, wherein the fluoride is at least one selected from the group consisting of obium fluoride, tantalum fluoride, cerium fluoride, praseodymium fluoride, neodymium fluoride, promethium fluoride, samarium fluoride, europium fluoride, gadolinium fluoride, terbium fluoride, dysprosium fluoride, holmium fluoride, erbium fluoride, thulium fluoride, ytterbium fluoride and lutetium fluoride.

5. The method for producing a porous sintered body according to claim 1 or 2, wherein the content ratios of the oxide ceramic particles for sintering and the sintering aid constituting the precursor compact are 90 to 97% by volume and 3 to 10% by volume, respectively, when the total of the two is 100% by volume.

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