Metal carbide sintered body and method for producing same

Abstract

The present invention addresses the problem of providing a metal carbide sintered body in which the occurrence of cracks is suppressed. Also provided is a method for producing a metal carbide sintered compact in which the occurrence of cracks is suppressed. This problem is solved by a metal carbide sintered body of at least one metal selected from the group consisting of Group 4 and Group 5 elements of the periodic table, the average particle diameter of the particles in the first region being 3.5-9.5 [mu] m, and the average particle diameter of the particles in the second region being 3.5-9.5 [mu] m. The ratio of the average particle diameter of the particles in the second region to the average particle diameter of the particles in the first region is from 0.75 to 1.0 (inclusive). Furthermore, this problem is solved by a method for producing a sintered carbide, the method comprising: a step for adding a carbon powder to a mixed powder of a SiO2 powder and a metal carbide of at least one metal selected from the group consisting of Group 4 and Group 5 elements of the periodic table; and a step for sintering the mixture to which the carbon powder has been added, the amount of the carbon powder added being 0.30-3.00 parts by mass (inclusive) per 100 parts by mass of the mixed powder.

Description

Technical Field

[0001] This invention relates to sintered metal carbide bodies. More specifically, it relates to sintered metal carbide bodies with reduced crack formation. Background Technology

[0002] Compared to silicon (Si) semiconductors, silicon carbide (SiC) semiconductors possess the following characteristics: high heat resistance, a wide band gap, and a high dielectric breakdown electric field strength. Therefore, they have attracted attention as semiconductor materials for low-power loss power devices, and are particularly anticipated as a fundamental material for automotive electronic components. SiC does not melt under normal pressure but sublimates at around 2000°C. Therefore, the CZ and FZ methods used in Si single crystal manufacturing cannot be employed in Si single crystal production. Consequently, the modified Rayleigh process and other sublimation methods are primarily used for the mass production of SiC single crystals. Furthermore, in recent years, there has been a demand for larger-sized SiC single crystal wafers, and methods for efficiently obtaining low-defect, high-quality SiC single crystals are being explored. Other manufacturing methods besides sublimation (such as solution methods and vapor phase growth methods) are also receiving considerable attention.

[0003] The methods described above all involve supplying raw materials (powders, gases, etc.) to heat-resistant containers (crucibles, furnace cores, etc.) such as graphite, and heating the raw materials from the outside of the container using methods such as high-frequency heating. SiC single crystal growth is carried out in ultra-high temperature regions above 2000℃. Graphite is known to have heat resistance above 2500℃, but in the SiC single crystal growth method described above, the surface of the graphite container is exposed to sublimation gases such as Si2C and SiC2, which sublimate upon high-temperature heating, as well as reactive gases from raw material gases such as SiH4, H2, and hydrocarbons. In the presence of such reactive gases, graphite sublimates, thus significantly reducing the heat resistance of the container. Therefore, it is necessary to replace graphite containers with containers made of metal carbides (e.g., tantalum carbide, niobium carbide, etc.) with much higher melting points than graphite.

[0004] In addition, SiC semiconductor devices are manufactured by growing SiC epitaxial films on wafers cut from bulk single crystals of SiC using methods such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). In the film deposition apparatus used to manufacture such SiC semiconductor devices, the SiC single crystal wafer, which serves as the substrate, needs to be heated to a high temperature and maintained at that temperature using methods such as high-frequency induction heating. Therefore, it has been proposed to use metal carbide materials with high heat resistance as heat-resistant components in the film deposition apparatus (e.g., Patent Document 1, Patent Document 2).

[0005] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2015-514673 Patent Document 2: Japanese Patent Application Publication No. 2016-4933 Summary of the Invention

[0006] The problem that the invention aims to solve However, these metal carbide sintered bodies are prone to surface cracking. Therefore, it is necessary to remove the cracked surface portions by grinding. As a result, considering the removal process using grinding, large sintered bodies need to be prepared in advance.

[0007] Therefore, the problem to be solved by the present invention is to provide a metal carbide sintered body that eliminates the aforementioned disadvantages, namely, suppresses the formation of cracks. Furthermore, a further problem to be solved by the present invention is to provide a method for manufacturing a metal carbide sintered body in which the formation of cracks is suppressed.

[0008] Methods for solving problems Through in-depth research, the inventors discovered that by making the particle size of the particles constituting the metal carbide sintered body uniform throughout the sintered body—that is, by reducing the variation in the average particle size throughout the sintered body—crack formation can be suppressed. Furthermore, it was found that by adding an excess of carbon to the metal carbide sintered body, the particle size of the particles constituting the obtained metal carbide sintered body can be made uniform throughout the sintered body, thus completing this invention.

[0009] A typical embodiment of the present invention is described below.

[0010] A sintered metal carbide body, wherein the metal carbide body is a sintered metal carbide body of at least one metal selected from the group consisting of elements in Groups IV and V of the periodic table. A cross-sectional photograph is obtained by photographing a plane perpendicular to the parallel projection image of the metal carbide sintered body, passing through the center of the inscribed circle that is inscribed in the parallel projection image and has the largest area, i.e., a continuous cross-section of the metal carbide sintered body. The cross-sectional photograph of the metal carbide sintered body is obtained by taking the direction parallel to the parallel projection image as the transverse direction, having a transverse dimension of 2.0 mm, and including both ends of the surface portion of the metal carbide sintered body within the longitudinal direction of the cross-sectional photograph. Specifically, when multiple continuous cross-sections of the metal carbide sintered body are included in the plane perpendicular to the parallel projection image, the cross-sectional photograph is obtained from the continuous cross-section that maximizes the cross-sectional area of ​​the metal carbide sintered body. When the portion cut out vertically by 260 μm and horizontally by 360 μm from the center of the cross-sectional photograph is designated as the first region, and the portion cut out vertically by 260 μm and horizontally by 360 μm from the surface side of the metal carbide sintered body in the cross-sectional photograph that is closer to the surface side of the metal carbide sintered body than the first region is designated as the second region, and the edge of the surface side of the metal sintered body in the second region is located on the longitudinal and central side of the cross-sectional photograph at a distance of 40 μm from the point on the surface portion of the metal carbide sintered body closest to the center of the cross-sectional photograph, the average particle size of the particles in the first region is 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is 0.75 or more and 1.0 or less.

[0011] In addition, another typical embodiment of the present invention is described below.

[0012] A method for manufacturing a carbide sintered body, comprising: The process of adding carbon powder to a mixed powder of a metal carbide of at least one metal selected from the group consisting of elements of Groups IV and V of the periodic table and SiO2 powder; and The process of sintering the mixture containing carbon powder. The amount of carbon powder added is more than 0.30 parts by mass and less than 3.00 parts by mass relative to 100 parts by mass of the mixed powder.

[0013] Invention Effects The metal carbide sintered body of the present invention (hereinafter sometimes simply referred to as "sintered body") has a uniform particle size overall. More specifically, when the interior of the sintered body is defined as a first region and the vicinity of the surface is defined as a second region, in the metal carbide sintered body of the present invention, the average particle size of the particles in the first region is 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is 0.75 or more and 1.0 or less. As a result, the metal carbide sintered body of the present invention is less prone to surface cracking. Therefore, the removal of the surface portion required by grinding in conventional sintered bodies can be suppressed, thus achieving excellent advantages such as reduced raw material consumption, increased yield, shortened delivery time, and reduced initial defect rate. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating a method for obtaining a cross-sectional photograph of a sintered body according to one embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram showing a cross-sectional photograph of a sintered body illustrating one embodiment of the present invention. However, for ease of illustration, the ratio of the lengths may sometimes differ from the actual lengths.

[0016] Figure 3 The reference figure illustrates a method for determining the average particle size from a cross-sectional photograph of a sintered body according to one embodiment of the present invention using the intercept method. Detailed Implementation

[0017] Metal carbide sintered body The sintered body of the present invention is a metal carbide sintered body composed of at least one metal selected from Groups IV and V of the periodic table, and the particle size of the particles constituting the sintered body is uniform overall. More specifically, in the sintered body of the present invention, the average particle size of the particles in the first region is 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is 0.75 or more and 1.0 or less. In typical metal carbide sintered bodies, the particle size of the particles constituting the sintered body is larger towards the interior of the sintered body and smaller towards the surface of the sintered body.

[0018] The sintered body of the present invention is a carbide sintered body of at least one metal selected from the group consisting of elements in Groups IV and V of the periodic table. Carbides of metals such as titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), and tantalum (Ta), which are elements in Groups IV and V of the periodic table, are known to be metal carbides with high melting points. For example, the melting point (Tm) of titanium carbide is 3530°C, that of zirconium carbide is 3803°C, that of hafnium carbide is 3887°C, that of niobium carbide is 3800°C, and that of tantalum carbide is 3880°C. Therefore, the above-mentioned metal carbide sintered bodies are suitable as raw materials for heat-resistant containers and the like.

[0019] The metal carbides used in the sintered body of the present invention are selected from carbides of at least one metal from the group consisting of elements in Groups IV and V of the periodic table. From the viewpoint of heat resistance, carbides of Ta, Nb, Ti, and Zr are preferred, and carbides of Ta and Nb are particularly preferred. These metal carbides can be used alone or in combination of two or more. It should be noted that metal carbides are a general term for compounds composed of metal elements and carbon. As long as they exist stably, the composition ratio of metal elements to carbon is not limited. For example, tantalum carbide contains TaC and Ta2C, and the sintered body can contain both TaC particles and Ta2C particles. In addition, niobium carbide contains NbC, Nb2C, and Nb6C5, and the sintered body can contain any one or more of NbC particles, Nb2C particles, and Nb6C5 particles. From the viewpoint of preventing crack formation by keeping the lattice constant (described later) constant, niobium carbide is preferably NbC particles, tantalum carbide is preferably TaC particles, titanium carbide is preferably TiC particles, and zirconium carbide is preferably ZrC particles.

[0020] The metal carbides described above can be obtained by known methods, for example, by mixing oxides of metals (titanium, zirconium oxide, hafnium, niobium, tantalum, tungsten, etc.) with carbon and heating the mixture under a hydrogen reducing atmosphere. Alternatively, metal carbides can also be obtained by heat-treating a mixed solution containing an organic compound having functional groups (e.g., OH groups, COOH groups) capable of coordinating with the metal as a carbon source in a non-oxygen atmosphere.

[0021] The metal carbide used to obtain the sintered body of the present invention can be in granular form. When using granular metal carbides, the average particle size of the granular metal carbides is preferably 0.05 μm or more and 20.0 μm or less, and more preferably 0.1 μm or more and 10.0 μm or less. By keeping the average particle size of the granular metal carbides within the above range, a denser sintered body can be obtained. It should be noted that the average particle size of the granular metal carbides refers to the average particle size (Fischer diameter) measured by air permeation using a Fisher sub-sieve particle size analyzer. The average particle size of the carbide can be appropriately adjusted according to the average particle size of the raw material (metal oxide) and the pulverization conditions when pulverizing (crushing) the obtained carbide. In addition, when the pulverization time is short, the particle size of the pulverized material is large, and when the pulverization time is long, the particle size of the pulverized material tends to decrease.

[0022] Here, cross-sectional photographs of the sintered body of the present invention used to define the "first region" and the "second region" are described.

[0023] The cross-sectional photograph in this invention is a photograph taken of a continuous cross-section of the metal carbide sintered body, on a plane perpendicular to the parallel projection diagram, passing through the center of the inscribed circle that is inscribed in the parallel projection diagram and has the largest area. The cross-sectional photograph is obtained by taking the direction parallel to the parallel projection diagram as the transverse direction, having a transverse dimension of 2.0 mm, and including both ends of the surface portion of the metal carbide sintered body in the longitudinal direction of the cross-sectional photograph. When multiple cross-sections of the metal carbide sintered body are included in the plane perpendicular to the parallel projection diagram, the cross-sectional photograph should be taken from the continuous cross-section where the cross-sectional area of ​​the metal carbide sintered body reaches the largest.

[0024] The accompanying drawings illustrate the method for obtaining cross-sectional photographs in this invention. However, the sintered body and the direction of cross-section acquisition in the drawings are illustrative, and the shape of the sintered body and the direction of the cross-section to be acquired are not limited.

[0025] First, consider a parallel projection diagram obtained by projecting the sintered body of the present invention from any direction. For example, in Figure 1In this invention, the surface of the plate-shaped sintered body 101 is placed at rest in a generally horizontal manner, and a parallel projection view 102 is conceived in the vertical direction downwards. The parallel projection view 102 in this invention refers to a view drawn with the line of sight from the observation point to the sintered body 101 being the object parallel, and is conceived as the outline of the sintered body 101 being the object.

[0026] Next, as Figure 1 As shown, imagine an inscribed circle 103 that is internally tangent to parallel projection 102 and has the largest area. Inscribed circle 103 is a circle that is internally tangent to parallel projection 102 and has the largest area, and is tangent to the outer edge of parallel projection 102 at at least two points. Figure 1 In the parallel projection diagram 102 of the plate-shaped sintered body 101, the shape is rectangular. Therefore, the inscribed circle 103 is the circle whose area is maximized when it is tangent to the outer edge of the parallel projection diagram 102 at at least 3 points.

[0027] Next, as Figure 1 As shown, imagine a plane 104 perpendicular to the parallel projection 102 and passing through the center of the inscribed circle 103. The cross-sectional photograph in this invention is a photograph of the cross-section of the sintered body 101 obtained along plane 104. When obtaining the cross-sectional photograph, to facilitate observation of the cross-section of the sintered body, the cross-section of the sintered body is mirror-polished and etched.

[0028] The cross-sectional photographs in this invention use the direction parallel to the above-mentioned parallel projection as the transverse direction (in... Figure 1 and Figure 2 In this context, it is represented by A-A'), and the cross-section of the sintered body is cut out in a manner with a transverse dimension of 2.0 mm, wherein both ends of the surface portion of the aforementioned metal carbide sintered body are included in the longitudinal direction. That is, as shown in the figure. Figure 2 As shown, the top and bottom edges of the cross-sectional photograph are... Figure 1 The parallel projection diagram 102 is parallel, and the lateral length of the cross-sectional photograph corresponds to 2.0 mm of the actual sintered body 101. Furthermore, the longitudinal length of the cross-sectional photograph is determined by the way the uppermost and lowermost parts 201 of the sintered body's surface in the cross-section are accommodated longitudinally. Therefore, as... Figure 2 As shown, the uppermost part 201 of the surface of the sintered body is located at the top edge of the cross-sectional photograph, and the lowermost part 202 of the surface of the sintered body is located at the bottom edge of the cross-sectional photograph.

[0029] Furthermore, in the aforementioned method for obtaining cross-sectional photographs, depending on the three-dimensional shape of the sintered body and the setting of the observation point for the imagined parallel projection, the obtained cross-sections of the sintered body may sometimes be multiple. In this case, in this invention, a cross-sectional photograph is obtained from the continuous cross-section with the largest cross-sectional area among the multiple cross-sections. A continuous cross-section refers to a cross-section of the sintered body that is not interrupted by any part other than the sintered body. By obtaining a cross-sectional photograph from this cross-section, such as... Figure 2 As shown, a cross-sectional photograph can be obtained that allows observation of the entire cross-section of the sintered body.

[0030] In this invention, the first region refers to the portion cut out from the center of the cross-sectional photograph obtained by the above method, with a vertical dimension of 260 μm and a horizontal dimension of 360 μm. That is, in Figure 2 In the image, the first region is the central portion 203 of the cross-sectional photograph. Furthermore, since the cross-sectional photograph is rectangular, its center coincides with the intersection of the two diagonals. Figure 2 The middle part is represented by a black dot.

[0031] In this invention, the second region refers to a portion further cut out from the cross-sectional photograph obtained by the above method, closer to the surface side of the sintered body than the first region, with a longitudinal dimension of 260 μm and a transverse dimension of 360 μm. The edge of the surface side of the sintered body in the second region is located 40 μm away from the point in the cross-sectional photograph closest to the center of the surface portion of the sintered body, along the longitudinal direction and center side of the cross-sectional photograph. That is, in Figure 2 In one example of the cross-sectional photograph of the sintered body shown, the second region is the portion 204 cut out of the cross-sectional photograph, located 40 μm below the point 205 in the surface portion of the sintered body that is closest to the center of the cross-sectional photograph.

[0032] Furthermore, the lengths described in the aforementioned cross-sectional photographs and the definitions of the first and second regions correspond to the actual lengths of the sintered body. For example, in the case of magnified cross-sectional photographs, the range of the first and second regions cut out is also magnified according to the magnification. Additionally, Figure 2 This is to illustrate that the scale, magnification, etc. of the first region, second region, and cross-sectional photographs in this invention are different from those of actual cross-sectional photographs.

[0033] In the sintered body of the present invention, the average particle size of the particles in the first region is 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is 0.75 or more and 1.0 or less.

[0034] The average particle size of the first and second regions can be determined using the intercept method. The intercept method involves drawing straight lines at regular intervals in a grid pattern on a cross-sectional photograph and calculating the particle size based on the length between the intersection points of these lines and the particles. (See reference...) Figure 3 The method for determining particle size based on the intercept method is described.

[0035] (1) Within the first and second regions of the metal carbide sintered body, SEM images with a temporary magnification of 1000x were obtained. Figure 3 ).

[0036] (2) Figure 3 As shown, on the entire obtained SEM image, straight lines were drawn in a grid pattern with one side corresponding to 20 μm of the sintered body. The average particle size was calculated based on the intersections of all the drawn straight lines with the particles. In addition, when counting the intersections of the straight lines with the particles, the number of intersections was recorded as "1" when the straight line was tangent to the outer edge of the particle or intersected with it, and "1.5" when the straight line intersected the three points of the particle.

[0037] (3) At this point, based on the particle size confirmed in the SEM image, the number of intersections between the straight line and the grid is approximately 200. If the number of intersections between the straight line and the particle in the SEM image is insufficient or excessive relative to 200, the magnification of the SEM image is adjusted so that the number of intersections between the straight line and the particle in the SEM image is approximately 200, and the average particle size is recalculated. For example, if the particle size is large, the magnification can be adjusted to about 500 times, and if the particle size is small, the magnification can be adjusted to about 2000 times.

[0038] The average particle size in the first region varies depending on the type of metal carbide described later. Preferably, the average particle size in the first region is 3.5 μm or more and 9.4 μm or less; more preferably, 3.5 μm or more and 9.3 μm or less; even more preferably, 3.5 μm or more and 9.2 μm or less; even more preferably, 3.5 μm or more and 9.1 μm or less; even more preferably, 3.5 μm or more and 9.0 μm or less; even more preferably, 3.5 μm or more and 8.9 μm or less; even more preferably, 3.5 μm or more and 8.8 μm or less; even more preferably, 3.5 μm or more and 8.7 μm or less; and particularly preferably, 3.5 μm or more and 8.6 μm or less. It is generally believed that the average particle size of the particles constituting the sintered body is larger closer to the interior of the sintered body and smaller closer to the surface. This leads to greater deviations in the average particle size and a greater likelihood of crack formation. Therefore, a smaller average particle size in the first region is sometimes preferred.

[0039] The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is preferably 0.76 or higher and 1.0 or lower, more preferably 0.77 or higher and 1.0 or lower, even more preferably 0.78 or higher and 1.0 or lower, even more preferably 0.79 or higher and 1.0 or lower, even more preferably 0.80 or higher and 1.0 or lower, even more preferably 0.81 or higher and 1.0 or lower, even more preferably 0.82 or higher and 1.0 or lower, even more preferably 0.83 or higher and 1.0 or lower, and particularly preferably 0.84 or higher and 1.0 or lower. The closer the ratio of average particle size is to 1.0, the smaller the difference between the average particle size of the particles in the first region and the average particle size of the particles in the second region. As a whole, the particle size is more uniform, thus, it is preferable to be a sintered body in which the generation of cracks is greatly suppressed.

[0040] It should be noted that, while not wishing to be bound by theory, it is believed that in conventional sintered bodies, grain (particle) growth occurs during the sintering process due to the lack of carbon content within the sintered body. Therefore, as mentioned above, in typical metal carbide sintered bodies, the particle size of the particles constituting the sintered body is larger towards the interior and smaller towards the surface. Based on this empirical rule in conventional sintered bodies, the inventors discovered that by controlling grain growth within the sintered body to ensure overall uniformity of particle size, crack formation can be suppressed, thus completing this invention.

[0041] The average particle size of the particles constituting the sintered body of the present invention is similar in both the first and second regions. The average particle size of the particles constituting the sintered body is preferably 1 μm or more and 100 μm or less, more preferably 1 μm or more and 10 μm or less. In the present invention, by forming a compound with the added carbon and metal elements, the degree of grain growth in the central and surface regions is homogenized, thereby preventing stress caused by localized coarsening of the particles. As a result, a sintered body that does not produce cracks and has excellent mechanical strength and corrosion resistance can be produced. It should be noted that the particle size can be calculated by mirror polishing, etching, and then observing the cross-section of the sintered body as described above, followed by image analysis.

[0042] Here, excessive etching at high temperatures and / or for extended periods can promote grain growth of the particles constituting the sintered body. Therefore, in calculating the average grain size of the particles constituting the sintered body of the present invention, it is preferable to minimize the effect of etching. The following conditions can be listed as conditions for such etching.

[0043] (1) The sintered body was heated from room temperature to 2400℃ in 12 hours at 200℃ / hour under an argon atmosphere (0.098MPa).

[0044] (2) After heating, maintain at 2400℃ for 4 hours.

[0045] (3) After maintaining this temperature for 4 hours, allow it to drop naturally from 2400℃ to room temperature.

[0046] In one aspect of the invention, as described above, the metal is preferably selected from the group consisting of Nb, Ta, Ti, and Zr. More preferably, the metal is Nb or Ta. As described above, the metal carbides of these metals have particularly high melting points, and are therefore suitable as raw materials for heat-resistant containers and the like used in ultra-high temperature regions above 2000°C.

[0047] The average particle size of the particles that make up the metal carbide sintered body varies depending on the type of metal.

[0048] In one embodiment of the present invention, the metal may be Nb. In this case, the average particle size of the particles in the first region of the sintered body may be 5.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region may be 0.75 or more and 1.0 or less. The average particle size of the particles in the first region of the sintered body is preferably 5.6 μm or more and 9.4 μm or less, more preferably 5.7 μm or more and 9.3 μm or less, further preferably 5.8 μm or more and 9.2 μm or less, further preferably 5.9 μm or more and 9.1 μm or less, even more preferably 6.0 μm or more and 9.0 μm or less, even more preferably 6.1 μm or more and 8.9 μm or less, even more preferably 6.2 μm or more and 8.8 μm or less, even more preferably 6.3 μm or more and 8.7 μm or less, and particularly preferably 6.4 μm or more and 8.6 μm or less. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is preferably 0.76 or higher and 1.0 or lower, more preferably 0.77 or higher and 1.0 or lower, even more preferably 0.78 or higher and 1.0 or lower, even more preferably 0.79 or higher and 1.0 or lower, even more preferably 0.80 or higher and 1.0 or lower, even more preferably 0.81 or higher and 1.0 or lower, even more preferably 0.82 or higher and 1.0 or lower, even more preferably 0.83 or higher and 1.0 or lower, and particularly preferably 0.84 or higher and 1.0 or lower.

[0049] In one embodiment of the invention, the metal may be Ta. In this case, the average particle size of the particles in the first region of the sintered body may be 3.5 μm or more and 7.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region may be 0.75 or more and 1.0 or less. The average particle size of the particles in the first region of the sintered body is preferably 3.6 μm or more and 7.4 μm or less, more preferably 3.7 μm or more and 7.3 μm or less, further preferably 3.8 μm or more and 7.2 μm or less, further preferably 3.9 μm or more and 7.1 μm or less, even more preferably 4.0 μm or more and 7.0 μm or less, even more preferably 4.1 μm or more and 6.9 μm or less, even more preferably 4.2 μm or more and 6.8 μm or less, even more preferably 4.3 μm or more and 6.7 μm or less, and particularly preferably 4.4 μm or more and 6.6 μm or less. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is preferably 0.76 or higher and 1.0 or lower, more preferably 0.77 or higher and 1.0 or lower, even more preferably 0.78 or higher and 1.0 or lower, even more preferably 0.79 or higher and 1.0 or lower, even more preferably 0.80 or higher and 1.0 or lower, even more preferably 0.81 or higher and 1.0 or lower, even more preferably 0.82 or higher and 1.0 or lower, even more preferably 0.83 or higher and 1.0 or lower, and particularly preferably 0.84 or higher and 1.0 or lower.

[0050] In one embodiment of the invention, the metal may be Ti. In this case, the average particle size of the particles in the first region of the sintered body may be 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region may be 0.75 or more and 1.0 or less. The average particle size of the particles in the first region of the sintered body is preferably 3.6 μm or more and 9.4 μm or less, more preferably 3.7 μm or more and 9.3 μm or less, further preferably 3.8 μm or more and 9.2 μm or less, further preferably 3.9 μm or more and 9.1 μm or less, even more preferably 4.0 μm or more and 9.0 μm or less, even more preferably 4.1 μm or more and 8.9 μm or less, even more preferably 4.2 μm or more and 8.8 μm or less, even more preferably 4.3 μm or more and 8.7 μm or less, and particularly preferably 4.4 μm or more and 8.6 μm or less. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is preferably 0.76 or higher and 1.0 or lower, more preferably 0.77 or higher and 1.0 or lower, even more preferably 0.78 or higher and 1.0 or lower, even more preferably 0.79 or higher and 1.0 or lower, even more preferably 0.80 or higher and 1.0 or lower, even more preferably 0.81 or higher and 1.0 or lower, even more preferably 0.82 or higher and 1.0 or lower, even more preferably 0.83 or higher and 1.0 or lower, and particularly preferably 0.84 or higher and 1.0 or lower.

[0051] In one embodiment of the invention, the metal may be Zr. In this case, the average particle size of the particles in the first region of the sintered body may be 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region may be 0.75 or more and 1.0 or less. The average particle size of the particles in the first region of the sintered body is preferably 3.6 μm or more and 9.4 μm or less, more preferably 3.7 μm or more and 9.3 μm or less, further preferably 3.8 μm or more and 9.2 μm or less, further preferably 3.9 μm or more and 9.1 μm or less, even more preferably 4.0 μm or more and 9.0 μm or less, even more preferably 4.1 μm or more and 8.9 μm or less, even more preferably 4.2 μm or more and 8.8 μm or less, even more preferably 4.3 μm or more and 8.7 μm or less, and particularly preferably 4.4 μm or more and 8.6 μm or less. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is preferably 0.76 or higher and 1.0 or lower, more preferably 0.77 or higher and 1.0 or lower, even more preferably 0.78 or higher and 1.0 or lower, even more preferably 0.79 or higher and 1.0 or lower, even more preferably 0.80 or higher and 1.0 or lower, even more preferably 0.81 or higher and 1.0 or lower, even more preferably 0.82 or higher and 1.0 or lower, even more preferably 0.83 or higher and 1.0 or lower, and particularly preferably 0.84 or higher and 1.0 or lower.

[0052] The average particle size in the first region can be adjusted by adding carbon powder to the mixed powder of metal carbide and SiO2, which serves as the raw material for the sintered body. This is believed to be because by further adding carbon powder to the mixed powder of metal carbide and SiO2, grain growth, which is mainly caused by the lack of carbon, is effectively suppressed.

[0053] The amount of carbon powder added to the mixed powder of metal carbide and SiO2 can vary depending on the shape of the final sintered body, particularly its thickness, and can be 0.30 parts by mass or more and 3.00 parts by mass or less relative to 100 parts by mass of the mixed powder of metal carbide and SiO2. The amount of carbon powder added relative to 100 parts by mass of the mixed powder of metal carbide and SiO2 is preferably 0.50 parts by mass or more and 2.75 parts by mass or less, and more preferably 0.75 parts by mass or more and 2.00 parts by mass or less. By making the amount of carbon powder added 0.30 parts by mass or more relative to 100 parts by mass of the mixed powder of metal carbide and SiO2, a sufficient amount of carbon can be supplied to suppress grain growth, which is mainly caused by a lack of carbon content. Therefore, grain growth inside the sintered body is suppressed, and a sintered body formed entirely of particles with uniform particle size can be obtained, thereby reducing and preventing the generation of cracks in the sintered body. On the other hand, by making the amount of added carbon powder less than 3.00 parts by mass relative to 100 parts by mass of the mixed powder of metal carbide and SiO2, a sintered body with high relative density can be obtained, and thus a sintered body with excellent mechanical strength can be obtained.

[0054] In one aspect of the present invention, the ratio of the lattice constant of the metal carbide in the second region to the lattice constant of the metal carbide in the first region can be 0.9999 or more and 1.0001 or less. By ensuring that the ratio of the lattice constant of the metal carbide in the second region to the lattice constant of the metal carbide in the first region is within the above-mentioned range, the particle size constituting the sintered body as a whole is uniform, and a sintered body in which crack formation is suppressed can be obtained.

[0055] In one aspect of the present invention, the difference between the lattice constant of the metal carbide in the first region and the lattice constant of the metal carbide in the second region can be less than 0.0005 Å. By ensuring that the difference between the lattice constants of the metal carbide in the first region and the metal carbide in the second region is within the aforementioned range, the particle size constituting the sintered body as a whole is uniform, and a sintered body in which crack formation is suppressed can be obtained.

[0056] In one aspect of the present invention, the lattice constants of the metal carbide in the first region and the metal carbide in the second region are 99.98% or more and 100.02% or less relative to the theoretical value of the lattice constant of the metal carbide. That is, the lattice constant of the metal carbide in the first region is 99.98% or more and 100.02% or less relative to the theoretical value of the lattice constant of the metal carbide, and the lattice constant of the metal carbide in the second region is also 99.98% or more and 100.02% or less relative to the theoretical value of the lattice constant of the metal carbide. By ensuring that the lattice constants of the metal carbide in the first region and the metal carbide in the second region are within the above-mentioned ranges, the particle size constituting the sintered body is uniform, resulting in a sintered body in which crack formation is suppressed.

[0057] The lattice constant can be calculated using the WPPF (Whole Powder Pattern Fitting) method, based on the diffraction peaks of the composition from the sintered body obtained by X-ray diffraction.

[0058] In a sintered carbide body of at least one metal selected from the group consisting of elements in Groups 4 and 5 of the periodic table, ideally the ratio of the metal element forming the metal carbide to the carbon element is 1:1. In this specification, the value of the lattice constant in this state is taken as the theoretical value of the lattice constant of the metal carbide.

[0059] Regarding preferred examples of carbides of metallic elements in Groups 4 and 5 of the periodic table, the specific theoretical values ​​of their lattice constants are described below. In the case of Nb, the theoretical lattice constant of niobium carbide (NbC) is 4.4704. In the case of Ta, the theoretical lattice constant of tantalum carbide (TaC) is 4.4564. In the case of Ti, the theoretical lattice constant of titanium carbide (TiC) is 4.32. In the case of Zr, the theoretical lattice constant of zirconium carbide (ZrC) is 4.689.

[0060] The lattice constant of the metal carbide in the second region can be adjusted by the carbon content of the raw material, the type of fixture used to hold the carbide during firing, and the presence or absence of contact with carbon components present in the furnace (e.g., components from furnace components such as heaters and insulation materials).

[0061] The lattice constant of the metal carbides in the first region can be adjusted by the carbon content of the raw material.

[0062] The sintered body of the present invention may contain trace amounts of silicon (Si). SiO2 can be used as the source of Si in the sintered body. For example, a mixed powder of metal carbide and SiO2 is prepared by adding an appropriate amount of SiO2 powder to metal carbide powder, and a sintering slurry containing carbon powder or the like is appropriately shaped and sintered to obtain a sintered body. By controlling the SiO2 content in the mixed powder, the Si content in the sintered body can be adjusted. Although it also depends on the content of other components in the mixed powder and the sintering conditions, the SiO2 content is preferably in the range of 0.01 parts by mass or more and 12 parts by mass or less, more preferably in the range of 0.06 parts by mass or more and 3 parts by mass or less, and particularly preferably in the range of 0.2 parts by mass or more and 0.9 parts by mass or less, relative to 100 parts by mass of the mixed powder of metal carbide and SiO2.

[0063] From the viewpoint of uniformly dispersing SiO2 in a mixed powder of metal carbide and SiO2, SiO2 is preferably supplied in the form of granules with a small average particle size, or in the form of a dispersion liquid formed by dispersing it in a dispersion medium such as water. When SiO2 is in granular form, the average particle size of SiO2 is preferably 0.05 μm or more and 10.0 μm or less, more preferably 0.1 μm or more and 5.0 μm or less, and even more preferably 0.2 μm or more and 0.5 μm or less. Furthermore, when SiO2 is supplied in the form of a dispersion liquid, the average particle size of the SiO2 particles dispersed in the dispersion medium is preferably 0.001 μm or more and 0.5 μm or less, more preferably 0.005 μm or more and 0.1 μm or less. It should be noted that the average particle size of SiO2 refers to the average particle size (Fischer diameter) measured by air permeation using a Fisher sub-sieve particle size analyzer, similar to that of granular metal carbide.

[0064] In obtaining the sintered body of the present invention, a binder resin can be further added to the mixed powder of metal carbide and SiO2. By adding a binder resin, when preparing a sintering slurry containing a mixed powder of metal carbide and SiO2, the viscosity adjustment and processability of the sintering slurry become easier, and the formability of the sintered body obtained by sintering the slurry is improved. There are no particular limitations on the binder resin as long as the effects described above are obtained; examples include: polyvinyl alcohol resin, acrylic resin, polyvinyl butyral resin, methylcellulose resin, ethylcellulose resin, acetylcellulose resin, phenolic resin, urea-formaldehyde resin, melamine resin, etc. Two or more of these binder resins can be used in combination. A preferred binder resin is polyvinyl alcohol resin.

[0065] The amount of binder resin added affects the viscosity of the sintering slurry, and therefore can be appropriately adjusted according to the intended use of the sintered body. For example, when using the sintered body as a heat-resistant component, the amount of binder resin added can vary depending on whether it is used as a substrate for the heat-resistant component or as a cover component for the substrate. The amount of binder resin added, for example, relative to 100 parts by weight of the mixed powder of metal carbide and SiO2, can be 0.01 parts by weight or more and 5.0 parts by weight or less, preferably 0.03 parts by weight or more and 3.0 parts by weight or less, and more preferably 0.05 parts by weight or more and 2.0 parts by weight or less. By setting the amount of binder resin added within this range, deformation of the obtained metal carbide sintered body can be suppressed, and the generation of carbon precipitates originating from the binder resin can be suppressed.

[0066] In order to improve the dispersibility of metal carbide and SiO2 in the mixed powder when preparing sintering slurry, additives can be further added in addition to binder resin. Examples of additives include polyethyleneimine-based polymeric dispersants, polyurethane-based polymeric dispersants, and polyallylamine-based polymeric dispersants. The amount of additive added relative to 100 parts by weight of the mixed powder of metal carbide and SiO2 can be 0.03 parts by weight or more and 2.0 parts by weight or less.

[0067] In addition to binder resin and additives, solvents can also be added to the mixed powder of metal carbide and SiO2. Examples of solvents include organic solvents such as ethanol, benzyl alcohol, toluene, dimethylacetamide, and methyl ethyl ketone, or water. One solvent can be used, or two or more solvents can be used in combination. The amount of solvent added affects the viscosity of the sintering slurry, and therefore can be adjusted appropriately according to the intended use of the sintered body. The amount of solvent added relative to 100 parts by weight of the mixed powder of metal carbide and SiO2 can be 5.0 parts by weight or more and 30.0 parts by weight or less.

[0068] In one aspect of the present invention, even when sintered under normal pressure, the relative density sometimes exceeds 94%. From the viewpoint of mechanical strength, the relative density of the sintered body is preferably 97.5% or higher, and particularly preferably 99% or higher. It should be noted that relative density is defined as the ratio of the sintered body density (bulk density) to the theoretical density, expressed as a percentage, and can be determined according to JIS-R1634. For example, the density of TaC is set to 14.3 g / cm³. 3 The density of NbC was set to 7.76 g / cm³. 3 The density of TiC was set to 4.90 g / cm³. 3 The density of ZrC was set to 6.9 g / cm³. 3 The density of SiO2 was set to 2.65 g / cm³. 3The density calculated using a weighted average is the theoretical density. The closer the bulk density obtained by Archimedes' method is to 100% of the theoretical density, the less voids and defects there are inside the sintered body, indicating a dense structure. In this method, a sintered body with high relative density can be obtained even without sintering under pressure. Therefore, it eliminates the need for pressurized sintering methods such as hot pressing and HIP, which are previously required to obtain sintered bodies with high relative density. Even complex-shaped bodies can be sintered under normal pressure to obtain sintered bodies with high relative density and excellent mechanical strength.

[0069] In the sintered body of the present invention, the purity of the sintered body (the mass ratio of metal carbide to the total mass of the sintered body) is preferably 97.5% or higher. By increasing the purity of the sintered body, the corrosion resistance (resistance to reactive gases) of the heat-resistant component when the sintered body is used as a heat-resistant component in a SiC semiconductor manufacturing apparatus can be improved. It should be noted that a sintered body with a purity of 97.5% or higher can be obtained by adjusting the mixing ratio of the metal carbide and SiO2 powder mixture, or by controlling the sintering temperature. It should also be noted that the mass ratio of metal carbide in the sintered body can be determined by inductively coupled plasma optical emission analysis (ICP), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), etc.

[0070] In one aspect of the present invention, pores may be present in the sintered body. In this case, the open porosity is preferably 1% or less, more preferably 0.5% or less. Furthermore, the closed porosity is preferably 5% or less, more preferably 3% or less. It should be noted that the open porosity (%) can be calculated according to JIS-R1634 using Archimedes' method. The closed porosity (%) is a value (%) obtained by subtracting the ratio of apparent density to theoretical density from 1. It should be noted that apparent density refers to the value measured according to JIS-R1634. Generally speaking, the smaller the open porosity and closed porosity, the higher the mechanical strength of the sintered body.

[0071] Furthermore, the ratio of open porosity to closed porosity is preferably 0 or higher and 0.5 or lower. A smaller open porosity relative to closed porosity means fewer pores on the outer surface of the sintered body that could easily become a source of damage, thus generally improving the mechanical strength of the sintered body. Additionally, by using such a sintered body as a heat-resistant component for SiC semiconductor manufacturing equipment, the surface area in contact with the atmospheric gas is reduced, thereby improving the corrosion resistance of the heat-resistant component.

[0072] Furthermore, even when pores exist in the sintered body, from the viewpoint of corrosion resistance of the heat-resistant component, smaller pores are better, and the average diameter of the pores is preferably 50 μm or less, more preferably 10 μm or less. It should be noted that the average diameter of the pores can be calculated by mirror polishing a section of the sintered body, observing the section under an electron microscope, viewing the image at any magnification, and performing image analysis. Specifically, any observation area of ​​the section can be divided into two regions: the sintered body portion (matrix region) and the pore portion (non-matrix region), and the diameters of the pores existing within a specified range (e.g., a range of 1 mm × 1 mm) of the section can be measured and used as their average value for calculation. Additionally, the maximum diameter of the pores is preferably 100 μm or less, more preferably 50 μm or less.

[0073] Furthermore, from the viewpoint of increasing strength and corrosion resistance, the shape of the pores is preferably approximately circular, and the aspect ratio of the pores is preferably in the range of 1 or more and 2 or less. Here, the aspect ratio of the pores is defined as follows: based on the image analysis of the cross-section of the sintered body observed using an electron microscope, the pores are approximated as ellipsoids, the major and minor axes are measured, and the major axis is divided by the minor axis.

[0074] The flexural strength of the sintered body of the present invention is 150 MPa or more. Preferably, the flexural strength is 200 MPa or more, more preferably 300 MPa or more. It should be noted that the flexural strength refers to the three-point flexural strength at room temperature (25°C) measured according to JIS-R1601. Since the sintered body of the present invention has a flexural strength of 150 MPa or more, the durability of the device can be improved when the sintered body of the present invention is used as a heat-resistant component of a semiconductor manufacturing apparatus.

[0075] The sintered body of the present invention is a sintered body of a metal carbide with a very high melting point, high relative density, and excellent mechanical strength. Therefore, it is suitable for use as a heat-resistant component in an apparatus for manufacturing silicon carbide (SiC) single crystal blocks, and as a heat-resistant component in a film-forming apparatus for manufacturing silicon carbide semiconductor wafers.

[0076] The sintered body of the present invention is less prone to surface cracking, thus suppressing the removal of the required surface portion by grinding, as is common in conventional sintered bodies. Therefore, it offers significant advantages such as reduced raw material consumption, increased yield, shorter delivery time, and lower initial defect rate.

[0077] Method for manufacturing carbide sintered bodies According to one aspect of the present invention, a method for manufacturing a carbide sintered body is provided, comprising: a step of adding carbon powder to a mixed powder of a metal carbide and SiO2 powder of at least one metal selected from the group consisting of elements of Group IV and Group V of the periodic table; and a step of sintering the mixture to which carbon powder has been added, wherein the amount of carbon powder added is 0.30 parts by mass or more and 3.00 parts by mass or less relative to 100 parts by mass of the mixed powder of metal carbide and SiO2.

[0078] Metal carbides selected from at least one metal from Groups 4 and 5 of the periodic table are preferably carbides of Ta, Nb, Ti, and Zr, and particularly preferably carbides of Ta and Nb. These metal carbides can be used alone or in mixtures of two or more. Metal carbides can be obtained by known methods, for example, by mixing an oxide of a metal (titanium, zirconium oxide, hafnium, niobium, tantalum, tungsten, etc.) with carbon and heating the mixture under a hydrogen reducing atmosphere. Alternatively, metal carbides can be obtained by heat-treating a mixed solution containing an organic compound having a functional group (e.g., OH group, COOH group) capable of coordinating with the metal as a carbon source in a non-oxygen atmosphere. Furthermore, commercially available metal carbides can be used.

[0079] The metal carbides used to manufacture the sintered body are preferably in granular form. The average particle size of the granular metal carbides is preferably 0.05 μm or more and 20.0 μm or less, more preferably 0.1 μm or more and 10.0 μm or less. To adjust the granular metal carbides to the aforementioned average particle size, the metal oxides or the metal carbides themselves, which will become the raw materials for the metal carbides, can be pulverized (crushed) beforehand. In this case, there are no particular limitations on the pulverization conditions; the longer the pulverization time, the smaller the particle size of the metal carbides. It should be noted that, as described above, the average particle size of the granular metal carbides refers to the average particle size (Fischer diameter) measured using a Fisher sub-sieve particle size analyzer by air permeation.

[0080] There are no particular limitations on the SiO2 powder used, but its particle size is preferably 0.05 μm or more and 10.0 μm or less, more preferably 0.1 μm or more and 5.0 μm or less, and even more preferably 0.2 μm or more and 0.5 μm or less.

[0081] There are no particular limitations on the method for obtaining a mixed powder of metal carbide and SiO2 by mixing them. For example, a ball mill, kneader, mixer, or high-speed agitator can be used. Regarding the mixing ratio of metal carbide and SiO2 powder, it is preferable to mix SiO2 in the range of 0.01 parts by mass or more and 12 parts by mass or less relative to 100 parts by mass of the mixed powder of metal carbide and SiO2, more preferably in the range of 0.06 parts by mass or more and 3 parts by mass or less, and particularly preferably in the range of 0.2 parts by mass or more and 0.9 parts by mass or less.

[0082] The method for manufacturing the sintered body of the present invention includes a step of adding carbon powder to a mixed powder of metal carbide and SiO2. The carbon powder used is not particularly limited, but its particle size is preferably 5 nm or more and 100 nm or less, more preferably 10 nm or more and 50 nm or less, and particularly preferably about 40 nm. The amount of carbon powder added is 0.30 parts by mass or more and 3.00 parts by mass or less relative to 100 parts by mass of the mixed powder of metal carbide and SiO2. Relative to 100 parts by mass of the mixed powder of metal carbide and SiO2, the amount of carbon powder added is preferably 0.50 parts by mass or more and 2.75 parts by mass or less, more preferably 0.75 parts by mass or more and 2.00 parts by mass or less.

[0083] In the method for manufacturing the sintered body of the present invention, when carbon powder is added to the mixed powder of metal carbide and SiO2, binder resin, dispersant and / or solvent may be further added as other additives.

[0084] As for the adhesive resin, there are no particular limitations as long as the effects described above can be obtained. Examples include: polyvinyl alcohol resin, acrylic resin, polyvinyl butyral resin, methylcellulose resin, ethylcellulose resin, acetylcellulose resin, phenolic resin, urea-formaldehyde resin, melamine resin, etc. Two or more of these adhesive resins can be used in combination. Polyvinyl alcohol resin is preferred as the adhesive resin. The amount of adhesive resin added can be, for example, 0.01 parts by weight or more and 5.0 parts by weight or less relative to 100 parts by weight of the mixed powder of metal carbide and SiO2, preferably 0.03 parts by weight or more and 3.0 parts by weight or less, and more preferably 0.05 parts by weight or more and 2.0 parts by weight or less.

[0085] As a dispersant, for example, polyethyleneimine-based polymeric dispersants, polyurethane-based polymeric dispersants, and polyallylamine-based polymeric dispersants can be used. The amount of dispersant added relative to 100 parts by weight of the mixed powder of metal carbide and SiO2 can be more than 0.03 parts by weight and less than 2.0 parts by weight.

[0086] Examples of solvents include organic solvents such as ethanol, benzyl alcohol, toluene, dimethylacetamide, and methyl ethyl ketone, as well as water. One solvent may be used, or a mixture of two or more may be used. For example, the amount of solvent added may be 5.0 parts by weight or more and 30.0 parts by weight or less relative to 100 parts by weight of the mixed powder of metal carbide and SiO2.

[0087] There are no particular restrictions on the method of adding or mixing carbon powder into the mixed powder of metal carbide and SiO2. For example, it can be listed that the powder is mixed for 1 to 6 hours by means of ball mill, kneader, mixer, high-speed agitator, etc.

[0088] The method for manufacturing a sintered body according to the present invention includes a step of sintering a mixture of metal carbide and SiO2 powders to which carbon powder has been added. A sintered body can be obtained by shaping the mixture with added carbon powder into a desired shape and then sintering it. For example, a sintering slurry can be prepared by mixing the above components, shaping the slurry into a desired shape, and then sintering the resulting molded body to obtain a metal carbide sintered body. Alternatively, the slurry can be granulated using a spray dryer or similar means, the granules can be shaped into a desired shape, and the resulting molded body can be sintered. There are no particular limitations on the molding method used to shape the mixture into the desired shape; conventionally known molding methods such as compression molding, extrusion molding, and casting molding can be employed.

[0089] After obtaining the shaped body as described above, a sintered body of the desired shape can be obtained by sintering the shaped body. Sintering can be performed at a temperature of 2200°C or higher and 2600°C or lower. Sintering is preferably performed at a temperature of 2250°C or higher and 2450°C or lower. Below the initial temperature of sintering (around 1600~1700°C), SiO2 melts and acts as a sintering aid, which can densify the sintered body. Sintering is preferably performed in an inert gas atmosphere such as argon or helium. In addition, sintering can be performed at atmospheric pressure or under pressure.

[0090] Example Next, the embodiments of the present invention will be specifically described with reference to the following examples, but the present invention is not limited to these examples.

[0091] Metal carbides use the following substances.

[0092] • Tantalum carbide (manufactured by Mitsui Metals & Minerals Co., Ltd., 1μm Fisher diameter, 99.9% purity) Niobium carbide (manufactured by Mitsui Metals & Minerals Co., Ltd., 1 μm Fisher diameter, 99.9% purity) The following powders are used for SiO2 powder.

[0093] ·Elkem Silica 971U (manufactured by Elkem Japan Co., Ltd.) Based on the SEM images, the particle size is approximately 0.05~0.5μm.

[0094] The carbon powder uses the following substances.

[0095] • Mitsubishi (registered trademark) Carbon Black MA14 (manufactured by Mitsubishi Chemical Corporation, particle size 40nm) Production of sintered bodies Metal carbide and SiO2 powders were mixed to form a mixed powder of metal carbide and SiO2, as shown in Table 1. Carbon powder was then further added and mixed into this mixed powder. To the mixture, 0.5 parts by mass relative to 100 parts by mass of the mixed powder of metal carbide and SiO2 were added as a dispersant (polyethyleneimine-based polymer dispersion), 0.5 parts by mass relative to 100 parts by mass of the mixed powder of metal carbide and SiO2 were added as a resin binder (polyvinyl alcohol), and 10 parts by mass relative to 100 parts by mass of the mixed powder of metal carbide and SiO2 were added as a solvent (water). The resulting mixture was ball-milled for 4 hours to prepare a slurry for sintering. The obtained slurry for sintering was then cast to produce the thickness and... (The sentence is incomplete in the original text). A 50mm circular plate-shaped molded body.

[0096] The plate-shaped molded body was sintered at 2300℃ under argon atmosphere and atmospheric pressure for 10 hours to obtain a circular plate-shaped sintered body.

[0097] Determination of the average particle size of the particles constituting the sintered body The obtained sintered body is divided approximately at the center of the circular plane passing through the obtained circular plate-shaped sintered body. The cross-section of the divided sintered body is mirror-polished, etched, and then photographed. The photographed cross-section is cropped with a lateral width of 2 mm and a longitudinal width including both ends of the surface portion of the sintered body, thus obtaining a cross-sectional photograph for observation. A cross-sectional photograph of the first region is obtained by cropping an area of ​​approximately 260 μm in length × 360 μm in width from the approximate center of the cross-sectional photograph for observation. A cross-sectional photograph of the second region is obtained by cropping an area of ​​260 μm in length × 360 μm from the upper surface portion of the sintered body in the cross-sectional photograph for observation, with the upper edge of the cropping area being an amount of approximately 40 μm below the point closest to the first region in the upper surface portion of the sintered body in the cross-sectional photograph for observation.

[0098] In addition, the etching conditions are as follows.

[0099] (1) The sintered body was heated from room temperature to 2400℃ in 12 hours at 200℃ / hour in an argon atmosphere (0.098MPa).

[0100] (2) After heating, maintain at 2400℃ for 4 hours.

[0101] (3) After maintaining this temperature for 4 hours, allow it to drop naturally from 2400℃ to room temperature.

[0102] The average particle size of the particles constituting the sintered body was calculated using the intercept method from the cross-sectional photographs of the first and second regions.

[0103] The intercept method is performed as follows.

[0104] (1) Within the first and second regions of the metal carbide sintered body, a SEM image with a magnification temporarily set to 1000 times is obtained.

[0105] (2) In the overall obtained SEM image, draw straight lines in a grid pattern with one side equivalent to 20 μm of the sintered body. Divide the length of all drawn lines by the number of intersections with the particles to calculate the average particle size. It should be noted that when counting the intersections between the lines and the particles, the number of intersections is recorded as "1" when the lines are tangent to the outer edge of the particles or intersect with them, and "1.5" when the lines intersect the three points of the particles.

[0106] (3) At this point, based on the particle size confirmed in the SEM image, the number of intersections between the straight line and the grid is approximately 200. If the number of intersections between the straight line and the particle in the SEM image is insufficient or excessive relative to 200, the magnification of the SEM image is adjusted so that the number of intersections between the straight line and the particle in the SEM image is approximately 200, and the average particle size is recalculated. For example, when the particle size is large, the magnification is adjusted to approximately 500 times, and when the particle size is small, the magnification is adjusted to approximately 2000 times.

[0107] Determination of lattice constant The sintered powder of the object to be measured was spread across the measuring holder, and smoothed using a glass plate to achieve a thickness of 0.5 mm. This process was then used to prepare the X-ray diffraction sample. X-ray diffraction measurements were performed using this sample. The lattice constant was calculated using the WPPF method by analyzing the diffraction peaks from NbC or TaC obtained from the X-ray diffraction measurements. In the analysis of the diffraction peaks, data obtained from standard materials provided by the National Institute of Standards and Technology (NIST), namely silicon powder samples (640c series), were used for correction.

[0108] The conditions for X-ray diffraction measurements and analysis of the measurement data are as follows.

[0109] Device name: SmartLab (9kW): Manufactured by Rigaku Corporation <Device Structure> wavelength Target: Cu Wavelength type: Ka1 ·Kα1:1.54059(Å) • Horizontal polarization rate: 0.500 Diffraction device • Goniometer: SmartLab studio II ver 4.6.358.0 • Accessory base: Z worktable (separate) • Attachment: ASC6 - Reflection • Kα1 focused beam optical system: Johnson type crystal <Measurement Conditions> Optical system properties: focusing method • CBO Select Slit: BB • Parallel slit for incident light: Soller_slit_5.0deg • Entrance slit: 2 / 3deg • Length limiting slit: 10.0mm • Light-receiving slit 1: Open • Parallel slit for receiving light: Soller_slit_5.0deg • Light-receiving slit 2: Open • Attenuator: Open • Detector: D / teX Ultra250 • Scan axis: 2θ / θ • Scanning mode: Continuous • Scan range: 5.0000~150.0000 deg • Step size: 0.0100 degrees • Scanning speed / measurement time: 2.0000 deg / min Data points: 14501 • Tube voltage: 45kV Tube current: 200mA HV: 0.00 • Measurement temperature: 25℃ <Conditions for Data Analysis> • Analysis software: Rigaku PDXL2 ver2.8.4 • Analysis method: WPPF method • Data processing: Automatic configuration file processing (refer to Rigaku PDXL User Manual p.305) Determination of relative density The bulk density of the sintered body was calculated using Archimedes' method according to JIS-R1634. Specifically, the sintered body was placed in distilled water and kept in water for 1 hour under reduced pressure using a diaphragm vacuum pump, and the weight in water W2 (g) was measured. Excess water was then removed with a damp cloth, and the weight in water W3 (g) was measured. Finally, the sintered body was placed in a dryer to dry thoroughly, and the dried weight W1 (g) was measured.

[0110] The bulk density ρb (g / cm³) is calculated using the following formula. 3 ).

[0111] ρb={W1 / (W3-W2)}×ρ1 In the formula, ρ1 (g / cm 3 () represents the density of distilled water.

[0112] The theoretical density ρc (g / cm³) is calculated from the density of metal carbides. 3 Using the obtained bulk density ρb and theoretical density, the relative density [RD](%) is calculated by the following formula.

[0113] RD=(ρb / ρc)×100 Evaluation of crack formation The surface of the sintered body was sprayed with 70% ethanol to visually confirm the presence of cracks. Ethanol evaporates rapidly at crack sites, so cracked areas appear whitish, thus indicating the presence of cracks. However, it can be difficult to judge crack formation during ethanol spraying. Therefore, for sintered bodies that were initially determined not to have developed cracks after ethanol spraying, the surface was rough-ground to a depth of approximately 50-100 μm for further visual confirmation. In this case, cracks appear as streaks, allowing for a more reliable determination of their presence. Based on these two visual tests, cases where no cracks were found were evaluated as "no cracks," and cases where cracks were found in either visual test were evaluated as "cracked."

[0114] Determination of bending strength A rectangular plate-shaped sintered body measuring 4mm × 36mm is cut from the circular plane of the sintered body. For sintered bodies with a thickness of 3mm, the three-point flexural strength is measured directly in its original state according to JIS-R1601:2008. For sintered bodies with a thickness greater than 3mm, the surface and back of the sintered body are ground to the same degree to achieve a thickness of 3mm, and then the three-point flexural strength is measured according to JIS-R1601:2008.

[0115] Calculation of rate of change of weight The weight of a rectangular plate-shaped sintered body (4 mm × 36 mm × 3 mm) used in the above-mentioned flexural strength determination was measured at room temperature (25 °C). Then, carbon sheets were attached to a carbon crucible, and the plate-shaped sintered body was placed in this carbon sheet shape. The temperature was increased to 2400 °C in an Ar atmosphere using a vacuum sintering furnace at a heating rate of 80 °C / hour, and sintered at 2400 °C for 6 hours. After sintering, the plate-shaped sintered body was cooled to room temperature (25 °C), and its weight was measured. The rate of change of weight was calculated using the following formula.

[0116] Weight change rate (%) = ((weight after firing - weight before firing) / weight before firing) × 100 Table 1 shows the types of metal carbides, the mixing ratio of the mixed powder of metal carbide and SiO2, the amount of carbon powder added, the thickness of the sintered body, the average particle size, the lattice constant, the relative density, the presence or absence of cracks, the bending strength and the rate of weight change in the examples and comparative examples.

[0117] Industrial applicability The sintered body of the present invention is less prone to surface cracking, thus suppressing the removal of surface portions required by grinding in conventional sintered bodies. Therefore, it offers significant advantages such as reduced raw material consumption, increased yield, shorter delivery time, and lower initial defect rate. The sintered body of the present invention is a sintered body of a metal carbide with a very high melting point, high relative density, and excellent mechanical strength. Therefore, it is suitable for use as a heat-resistant component in manufacturing apparatus for silicon carbide (SiC) single crystal blocks and in film-forming apparatus for manufacturing silicon carbide semiconductor wafers. Therefore, it has high applicability not only in the ceramics industry, which requires such sintered bodies, but also in various industries such as the semiconductor and electronic component industries.

[0118] Explanation of reference numerals in the attached figures 101 Sintered Body 102 Parallel Projection Diagram 103. The inscribed circle that is internally tangent to the parallel projection and has the largest area. 104 Plane 201 The uppermost part of the surface of the sintered body 202 The lowest part of the surface of the sintered body 203 First District 204 Second Zone 205 The point closest to the center of the cross-sectional photograph in the surface portion of the sintered body.

Claims

1. A sintered metal carbide body of a metal, wherein the metal carbide body is a sintered body of at least one metal selected from the group consisting of elements in Groups IV and V of the periodic table. In the case where a cross-sectional photograph of the metal carbide sintered body is obtained by photographing a plane perpendicular to the parallel projection image, and passing through a plane that is inscribed in the center of the inscribed circle with the largest area in the parallel projection image, i.e., a continuous cross-section of the metal carbide sintered body, and the cross-sectional photograph of the metal carbide sintered body is obtained by taking the direction parallel to the parallel projection image as the transverse direction, having a transverse dimension of 2.0 mm, and including both ends of the surface portion of the metal carbide sintered body within the longitudinal direction of the cross-sectional photograph, wherein, In the case where a cross-sectional photograph is obtained from the continuous cross-section of the metal carbide sintered body that maximizes the cross-sectional area of ​​the metal carbide sintered body when multiple continuous cross-sections are included in a plane perpendicular to the parallel projection, the cross-sectional area of ​​the metal carbide sintered body is maximized. When the portion cut out vertically by 260 μm and horizontally by 360 μm from the center of the cross-sectional photograph is designated as the first region, and the portion cut out vertically by 260 μm and horizontally by 360 μm from the surface side of the metal carbide sintered body in the cross-sectional photograph that is closer to the surface side of the metal carbide sintered body than the first region is designated as the second region, and the edge of the surface side of the metal sintered body in the second region is located on the longitudinal and central side of the cross-sectional photograph at a distance of 40 μm from the point on the surface portion of the metal carbide sintered body closest to the center of the cross-sectional photograph, the average particle size of the particles in the first region is 3.5 μm or more and 9.5 μm or less, and the ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is 0.75 or more and 1.0 or less.

2. The metal carbide sintered body according to claim 1, wherein, The metal is selected from the group consisting of Nb, Ta, Ti and Zr.

3. The metal carbide sintered body according to claim 1, wherein, The metal is Nb. The average particle size in the first region is greater than 5.5 μm and less than 9.5 μm. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is greater than 0.75 and less than 1.

0.

4. The metal carbide sintered body according to claim 1, wherein, The metal is Ta. The average particle size in the first region is greater than 3.5 μm and less than 7.5 μm. The ratio of the average particle size of the particles in the second region to the average particle size of the particles in the first region is greater than 0.75 and less than 1.

0.

5. The metal carbide sintered body according to claim 1, wherein, The ratio of the lattice constant of the metal carbide in the second region to that in the first region is greater than 0.9999 and less than 1.0001.

6. The metal carbide sintered body according to claim 1, wherein, The difference between the lattice constant of the metal carbide in the first region and the lattice constant of the metal carbide in the second region is less than 0.0005 Å.

7. The metal carbide sintered body according to claim 1, wherein, The lattice constants of the metal carbides in the first region and the metal carbides in the second region are greater than 99.98% and less than 100.02% of the theoretical lattice constants of the metal carbides.

8. A method for manufacturing a carbide sintered body, comprising: The process of adding carbon powder to a mixed powder of a metal carbide of at least one metal selected from the group consisting of elements of Groups IV and V of the periodic table and SiO2 powder; and The process of sintering the mixture containing carbon powder. in, The amount of carbon powder added is more than 0.30 parts by weight and less than 3.00 parts by weight relative to 100 parts by weight of the mixed powder.

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