WO2018164118A1 - Paste composition, carbide sintered body, method for producing same, and refractory member - Google Patents

Abstract

[Problem] To provide a paste composition which enables the achievement of a carbide sintered body that has high density and high gas shielding performance, while containing less residual sintering assistant in the sintered body even in cases where sintering is carried out at lower temperatures than ever before. [Solution] A paste composition which contains a carbide that has a melting point of 3,000°C or higher and a fluoride of at least one element that is selected from among elements in group 2 or group 3 of the periodic table.

Description

Paste composition, carbide sintered body, method for producing the same, and refractory member

The present invention relates to a paste composition. More specifically, the present invention relates to a paste composition containing a carbide having a melting point of 3000 ° C. or higher, a carbide sintered body, a manufacturing method thereof, and a refractory member.

Silicon carbide (SiC) semiconductors not only have high heat resistance compared to silicon (Si) semiconductors, but also have a wide band gap and a high dielectric breakdown electric field strength. It is attracting attention as a semiconductor material. Since SiC does not melt under normal pressure and sublimes at a temperature of about 2000 ° C., the CZ method and FZ method used for the production of Si single crystal cannot be employed. For this reason, sublimation methods such as an improved Rayleigh method are mainly employed in mass production of SiC single crystals. In recent years, there has been a demand for a large-diameter SiC single crystal wafer, and a method for efficiently obtaining a low-defect, high-quality SiC single crystal has been sought. Manufacturing methods other than the sublimation method ( A solution method, a gas growth method, etc.) are attracting attention.

In any of the above methods, the raw material is supplied to a heat-resistant container (crucible) such as graphite and the raw material is heated from the outside of the container by means of high-frequency heating or the like, and SiC single crystal growth is performed at an ultrahigh temperature of about 2500 ° C. Done in the area. Although graphite is known to be a material having heat resistance of 2500 ° C. or higher, in the SiC single crystal growth method as described above, sublimation gases such as Si ₂ C and SiC ₂ sublimated by high-temperature heating, SiH _The surface of the graphite container is exposed to a reactive gas derived from a source gas such as ₄ . In the presence of such a reactive gas, the heat resistance of graphite is significantly reduced. Therefore, it is conceivable to use a container made of a metal carbide having a melting point much higher than that of graphite instead of the graphite container. However, metal carbides such as tantalum carbide and hafnium carbide are expensive and difficult to process. . Therefore, it is conceivable to coat the surface of a substrate such as graphite with a carbide sintered body. As a coating method, it is conceivable to carbonize the metal after coating the surface of the substrate with a high melting point metal by vapor deposition, etc., but cracking occurs in the carbide coating due to volume expansion when carbonizing the surface layer metal, There is a problem that the carbide coating is easily peeled off from the substrate.

In order to solve the above problems, for example, JP 2009-137789 A (Patent Document 1) discloses that tantalum carbide powder is sintered under a high pressure of 20 MPa or higher under vacuum to sinter high-density tantalum carbide. It has been proposed to obtain a molded body consisting of a body. Japanese Patent Application Laid-Open No. 2010-248060 (Patent Document 2) discloses a paste in which an auxiliary powder made of transition metal or transition metal carbide is added to carbides such as niobium carbide, hafnium carbide, tantalum carbide, and tungsten carbide. It has been proposed to obtain a high temperature resistant member made of a carbide sintered body by molding the paste into a desired shape and sintering it. Furthermore, in the pamphlet of International Publication No. 2013/172286 (Patent Document 3), a ceramic layer obtained by sintering a mixture containing a metal nitride or metal carbide and a sintering aid such as yttrium oxide is provided on the surface of the carbon material. A carbon material-ceramic material joined body obtained by joining the two has been proposed.

JP 2009-137789 A JP 2010-248060 A International Publication 2013/172286 Pamphlet

Since the tantalum carbide sintered body proposed in Patent Document 1 needs to be pressurized at the time of sintering, it is not easy to obtain a compact body having a complicated shape and a high density. It was difficult to form a tantalum carbide sintered film on the surface of the material. In addition, since the paste described in Patent Document 2 and the mixture described in Patent Document 3 contain a sintering aid, a small amount of auxiliary powder is contained in the sintered body when a carbide sintered body is obtained. It tends to remain. For this reason, when the obtained carbide sintered body is used as a container for SiC single crystal growth as described above, the portion where the sintering aid remains in the sintered body is preferentially eroded by the reactive gas, From there, the reactive gas permeates the coating and erodes the graphite, which is the base material, which may deteriorate the high temperature durability of the container. In order to completely remove the residue of the auxiliary powder, it is considered necessary to fire at a temperature (2500 ° C. or higher) higher than the heat resistance of the base graphite.

Therefore, even if the object of the present invention is to sinter at a lower temperature than in the prior art, there is little residual amount of sintering aid in the sintered body, and the sintered carbide body has high density and high gas shielding properties. Is to provide a paste composition.

Another object of the present invention is to provide a carbide sintered body using the paste composition, a method for producing the same, and a refractory member.

By adding a specific fluoride as a sintering aid to a carbide having a high melting point and difficult to sinter, the present inventors can sinter the sintered body even when sintered at a temperature lower than 2450 ° C. It was found that a carbide sintered body with a small amount of residual sintering auxiliary agent, a high density and a high gas shielding property can be obtained. According to this invention, the following paste composition, the manufacturing method of the carbide sintered compact using the same, and a refractory member are provided.

The paste composition according to the present invention includes a carbide having a melting point of 3000 ° C. or higher,
A fluoride of at least one element selected from Group 2 or Group 3 of the Periodic Table;
Is included.

Moreover, the carbide sintered body according to another aspect of the present invention is a carbide sintered body of the paste composition described above,
The area occupancy of the sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
S = D × (1−I / 0.6)
The carbide required condition index S expressed by the following is a sintered carbide body in which S ≧ 0.69.

Further, a fireproof member according to another aspect of the present invention is a fireproof member comprising a base material and a coating covering at least a part of the surface of the base material,
The coating consists of a sintered carbide of the paste composition described above,
The carbide sintered body is:
The area occupancy of the carbide sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
S = D × (1−I / 0.6)
The pure carbide requirement index S expressed by the following is S ≧ 0.69.

Moreover, the fireproof member according to another aspect of the present invention is a fireproof member formed by bonding the first base material and the second base material via a connecting material,
The connecting material comprises a carbide sintered body of the paste composition described above,
The carbide sintered body is:
The area occupancy of the carbide sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
S = D × (1−I / 0.6)
The pure carbide requirement index S expressed by the following is S ≧ 0.69.

According to the present invention, by using a paste composition in which a specific fluoride is added as a sintering aid to a carbide having a high melting point that is difficult to sinter, It is possible to realize a paste composition in which a sintered sintering agent remaining amount in the bonded body is small, and a carbide sintered body having a high density and a high gas shielding property can be obtained.

The electron microscope observation photograph of the section of the carbide sintered compact obtained using paste composition 4 of an example. The analysis image binarized from the electron microscopic observation photograph of FIG. 1 with the closed region occupied by the pore portion as a black portion and the other as a white portion.

<Paste composition>
The paste composition according to the present invention contains a carbide having a melting point of 3000 ° C. or higher and a fluoride of at least one element selected from Group 2 or Group 3 of the periodic table as essential components. Even when the paste composition according to the present invention is sintered at a temperature lower than that of the prior art, a carbide sintering body having a high density and a high gas shielding property is obtained with a small amount of residual sintering aid in the sintered body. can get. The reason for this is not clear, but is considered as follows. That is, a carbide having a high melting point has low sinterability, and a high-density sintered body cannot be obtained unless a sintering aid is used in combination. As the sintering aid, one having a melting point lower than the sintering temperature is selected. That is, when the sintering aid melts during sintering, the carbides are easily sintered and a high-density sintered body is obtained. However, usually a small amount of sintering aid remains in the sintered body. In the present invention, by using a fluoride of an element selected from Group 2 or Group 3 of the periodic table (for example, calcium fluoride), the sintering aid is melted at the initial stage of sintering. Thus, the sinterability of the carbide is enhanced, and the fluoride is sublimated or vaporized as the sintering proceeds, so that the remaining amount of the sintering aid in the obtained sintered body is considered to be reduced.

The carbide used in the present invention is not particularly limited as long as it has a melting point (Tm) of 3000 ° C. or higher, but a known carbide can be suitably used as a metal carbide having a high melting point. For example, titanium carbide (Tm = 3530 ° C.), zirconia carbide (Tm = 3803 ° C.), hafnium carbide (Tm = 3887 ° C.), niobium carbide (Tm = 3800 ° C.), tantalum carbide (Tm = 3880 ° C.), tungsten carbide ( Tm = 3058 ° C.) and the like. Among these, tantalum carbide is preferable from the viewpoint of heat resistance, but two or more kinds may be mixed.

The metal carbide as described above can be obtained by a known method. For example, a metal oxide (titanium, zirconia, hafnium, niobium, tantalum, tungsten, etc.) and carbon are mixed, and the mixture is subjected to a hydrogen reduction atmosphere. Metal carbide can be obtained by heating at Alternatively, a metal carbide is obtained by heat-treating, in a non-oxygen atmosphere, a mixed solution in which an organic substance having a functional group capable of coordinating to the metal (for example, OH group or COOH group) is added as a carbon source to a metal alkoxide. Also good.

The carbide used in the paste composition according to the present invention is preferably in the form of particles. This is because it is necessary to uniformly disperse the carbide in the paste composition. The average particle size of the carbide is preferably in the range of 0.05 to 20.0 μm, more preferably in the range of 0.1 to 10.0 μm. By using carbide particles having an average particle diameter in such a range, the carbide can be uniformly dispersed in the paste composition, and when the paste composition is sintered, a higher-density carbide firing is performed. A ligation can be obtained. The average particle diameter is an average particle diameter (Fischer diameter) measured by an air permeation method using a Fisher sub-sieve sizer model 49 average particle size measuring device manufactured by Fischer, USA. That is, 14.53 g of a carbide (for example, TaC) sample is filled in the sample tube of the above apparatus, air is passed through it under constant pressure, the numerical value on the calculator chart of the manometer water level is read, and the value is determined as the particle size (μm). To do. The average particle diameter of the carbide can be appropriately adjusted depending on the average particle diameter of the raw material (metal oxide) and the pulverization conditions when the obtained carbide is pulverized (pulverized). When the pulverization time is short, the particle size of the material to be pulverized is large, and when the pulverization time is long, the particle size tends to be small and the particle size distribution tends to be narrow.

The paste composition according to the present invention includes fluoride of at least one element selected from Group 2 or Group 3 of the periodic table in addition to the above-described carbide. Fluoride functions as a sintering aid when sintering carbide. That is, the sintering aid is melted at a temperature equal to or lower than the starting temperature when sintering the carbide (about 1400 ° C.), and the sintered body can be densified when the carbide is sintered. On the other hand, this fluoride as described above has a relatively low boiling point and sublimates or vaporizes at the carbide sintering temperature (2200 to 2600 ° C.), so that the amount of fluoride remaining after sintering can be kept low. . It is considered that a carbide sintered body having a high density and a high gas shielding property can be obtained by using such a fluoride as a sintering aid for the carbide sintered body.

Specific examples of the fluoride include beryllium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, lanthanum fluoride, and cerium fluoride. Among these fluorides, magnesium fluoride and calcium fluoride are used because the carbide can be sufficiently connected by melting of the sintering aid before the carbide is solidified and sintered by sublimation or vaporization of the sintering aid. , Barium fluoride, lanthanum fluoride, and cerium fluoride are preferred. In particular, calcium fluoride can be preferably used from the viewpoint of obtaining a high-density, high-gas-shielding carbide sintered body. Calcium fluoride has a melting point of about 1400 ° C. and a boiling point of about 2500 ° C.

The above-mentioned fluoride is also preferably in a particulate form from the viewpoint of being uniformly dispersed in the paste composition. It is preferable to use a fluoride having an average particle size in the range of 0.1 to 10.0 μm, and more preferably in the range of 0.5 to 5.0 μm. The definition of the average particle diameter is the same as described above.

When the content of fluoride with respect to carbide increases, the theoretical density of the carbide sintered body increases and a high-density carbide sintered body is obtained, but the residual amount of fluoride in the carbide sintered body tends to increase. When a carbide sintered body is used in a vessel (crucible) or the like for SiC single crystal growth, the fluoride remaining in the carbide sintered body reacts with the atmospheric gas, and the place where the fluoride was present is a void. May be. Therefore, even if it is a high-density carbide sintered body at the beginning of use, there is a possibility that the gas shielding properties will deteriorate as it is repeatedly used. Therefore, in the present invention, the fluoride content in the paste composition is preferably in a ratio of 0.5 to 7 mol with respect to 100 mol of carbide. By containing fluoride in this range, it is possible to obtain a carbide sintered body with high density and high gas shielding properties, and it is possible to maintain gas shielding properties even when used repeatedly as a container.

The paste composition according to the present invention may contain a binder resin in addition to the above-described carbide and fluoride. By adding a binder resin, the viscosity adjustment of the paste composition is facilitated and the coating properties and handling properties are improved, so that the moldability when sintering the paste composition to form a carbide sintered body is improved. Can do. The binder resin is not particularly limited as long as the above effects can be obtained. For example, polyvinyl alcohol resin, acrylic resin, polyvinyl butyral resin, methyl cellulose resin, ethyl cellulose resin, acetyl cellulose resin, phenol Resin, urea resin, melamine resin, etc. are mentioned. Two or more of these binder resins may be mixed and used. A particularly preferred binder resin is a polyvinyl butyral resin.

Since the binder resin content in the paste composition affects the viscosity of the paste composition, it is used for the paste composition, that is, for coating the substrates, or for bonding the substrates. In general, the range of 0.1 to 2.0 parts by mass with respect to 100 parts by mass of carbide is preferable. When there is too much content of binder resin, distortion will arise in the obtained carbide sintered compact, or carbon precipitate derived from binder resin will occur easily.

The paste composition according to the present invention may contain an additive for improving the dispersibility of carbides and fluorides in addition to the binder resin. For example, a polyethyleneimine polymer dispersant, a polyurethane polymer dispersant, a polyallylamine polymer dispersant and the like can be suitably used. The content of the additive is preferably in the range of 0.03 to 0.20 parts by mass with respect to 100 parts by mass of carbide.

Furthermore, in order to prepare the paste composition, it may contain a solvent in addition to the binder resin and additives. Examples of the solvent include organic solvents such as ethanol, benzyl alcohol, toluene, dimethylacetamide, and methyl ethyl ketone, and these can be used alone or in combination. Since the solvent content affects the viscosity of the paste composition, it can be appropriately adjusted according to the use of the paste composition, but is generally 5.0 to 30.0 parts by mass with respect to 100 parts by mass of the carbide. The range of is preferable.

<Carbide sintered body and manufacturing method thereof>
The carbide sintered body according to the present invention can be obtained by sintering the paste composition described above. For example, first, the paste composition is poured into a container having a desired shape. Thereafter, the paste composition is dried to remove the solvent. Drying of the paste composition may be natural drying, or may be hot air drying or vacuum drying to shorten the drying time. The temperature at which hot air drying is performed is generally 50 to 150 ° C., although it depends on the type of solvent used. When drying in a heated atmosphere, it is preferably performed in an inert atmosphere to prevent oxidation of the paste composition.

Next, the molded body (paste composition) from which the solvent has been removed is sintered to obtain a carbide sintered body. Sintering is performed at a temperature of 2200 to 2600 ° C., preferably at a temperature of 2350 to 2450 ° C. When the fluoride in the paste composition is melted below the temperature at the start of sintering (about 1400 ° C.) and the carbide is sintered, the sintered body is densified and the fluoride at the above sintering temperature. Is vaporized or sublimated, so that a sintered carbide with high density and high gas shielding properties can be obtained.

Although the carbide sintered body according to the present invention has a high density and a very small content of the sintering aid, as a result, a carbide sintered body excellent in gas shielding properties can be realized. That is, in the carbide sintered body obtained by sintering the paste composition according to the present invention, the area occupancy of the sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%), and the cross section When the content of metal elements other than carbides obtained by energy dispersive X-ray spectroscopic analysis at I is I (mol%), the following formula:
S = D × (1−I / 0.6)
It is characterized in that the pure carbide requirement index S represented by: S ≧ 0.69.

Here, the area occupancy D (%) refers to an arbitrary observation region of 15 μm × 25 μm in a cross section of a carbide sintered body, a sintered body portion (matrix region) and a pore portion (non-matrix). It is defined as an area ratio (%) of the sintered body portion. Specifically, in the cross-sectional image of the carbide sintered body, when the closed region occupied by the pore portion is a blackened portion and the other is whitened, the total area of the whitened portion is the observation region. The area occupancy D (%) can be obtained as a ratio of the area. Further, the metal element content I (mol%) is a mapping of the observation region by energy dispersive X-ray spectroscopic analysis, and the metal elements (for example, titanium, zirconia, It is defined as a ratio (mol%) of a metal element (for example, calcium derived from calcium fluoride) other than metal elements such as hafnium, niobium, tantalum, and tungsten. Typical observation conditions for an electron micrograph are, for example, an acceleration voltage of 15 kV, a movable aperture diameter of 30 μm, and an emission current of 260 μA.

The pure carbide requirement index S becomes closer to 1 as the number of voids and pores in the sintered body is smaller, but even if the sintered body is completely free of voids and pores (D = 1), If other metal elements remain in the aggregate, the value can be smaller than 1. In the present invention, if the value of the pure carbide necessary condition index S of the carbide sintered body is less than 0.69, a carbide sintered body having high density and high gas shielding properties cannot be realized. In the present invention, a preferable range of the pure carbide requirement index S is 0.70 ≦ S ≦ 0.90.

<Fireproof member>
The carbide sintered body according to the present invention is formed from a carbide sintered body having a desired shape by forming the paste composition into a desired shape as described above and sintering the paste composition. However, it is also possible to provide a fireproof member provided as a coating on the surface of a base material made of graphite or the like as described below, or used as a connecting material for joining the base materials together.

For example, after applying the above paste composition to the surface of a base material made of graphite or boron nitride to form a coating film, drying the coating film to remove the solvent contained in the paste composition, To form a film made of a sintered carbide. Formation of a coating film is not restricted to application | coating, You may form by immersing a base material in a paste composition. As described above, the coating film is sintered at a temperature of 2200 to 2600 ° C. In this way, when the fluoride in the paste composition melts and the carbide is sintered, the sintered body is densified, and the fluoride is vaporized or sublimated by sintering, so it has excellent high temperature durability. A refractory member having a coating made of a carbide sintered body having a high density and a high gas shielding property can be produced.

The thickness of the coating made of a carbide sintered body is preferably 30 to 500 μm, although it depends on the use of the refractory member. If the film thickness is too thin, the fire resistance and high-temperature durability may be insufficient. On the other hand, if the film thickness is too thick, the film may crack or peel due to the difference in thermal expansion coefficient with the substrate. is there. When forming a film thicker than 500 μm, use a carbide sintered body that has a thermal expansion coefficient close to that of the base material, or use a base material close to the thermal expansion coefficient of the carbide sintered body. Is preferably used.

Further, base materials made of graphite, boron nitride, or the like may be bonded together via a connecting material made of the carbide sintered body of the present invention. For example, preparing a plurality of base materials on a flat plate, applying the paste composition described above to the end portions of the flat plate base material, joining the end portions of the substrate to form a container, etc., and then sintering. Thus, it is possible to manufacture a refractory member in which the end portions of the base material are bonded by the carbide sintered body. Sintering is performed at a temperature of 2200 to 2600 ° C. as described above. Further, the thickness of the connecting material is preferably 30 to 500 μm for the reason described above.

Next, 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.

<Preparation of paste compositions 1-6>
Tantalum carbide (Mitsui Metal Mining Co., Ltd., purity 99.5%) having an average particle size of 0.5 to 1.5 μm was used as a carbide having a melting point of 3000 ° C. or higher. In addition, as fluoride, average particle diameter was measured using calcium fluoride (manufactured by Hakuho Chemical Laboratory Co., Ltd.) having an average particle diameter of 10.0 to 15.0 μm, ethanol as a solvent, and zirconia balls having a diameter of 10 mm. Calcium fluoride ground to a diameter of 1.5 μm was used. Furthermore, vinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd.) was used as a resin binder, polyethyleneimine (manufactured by Wako Pure Chemical Industries, Ltd.) having an average weight molecular weight of 10,000 was used as an additive, and ethanol was used as a solvent.
It mix | blends so that content of fluoride may become the ratio shown in following Table 1 with respect to 100 mol of carbides, a resin binder is 0.5 mass part with respect to 100 mass parts of carbides, and an additive is 0.1 mass part. Then, each component was mixed so that the ratio of the solvent was 8.5 parts by mass, and mixed with a hybrid mixer (ARE-310, manufactured by Shinky Co., Ltd.) for 120 seconds to prepare paste compositions 1 to 4. Further, paste composition 5 was prepared in the same manner as paste composition 2 except that 2 mol% of cobalt was added instead of calcium fluoride. Furthermore, paste composition 6 was prepared in the same manner as paste composition 1 except that calcium fluoride was not added.

<Manufacture of carbide sintered body>
An isotropic graphite substrate (manufactured by Shin Nippon Techno Carbon Co., Ltd.) was prepared as a base material. The paste composition obtained as described above was brushed on the surface of the substrate to form a coating film. The coating amount was adjusted so that the coating thickness after drying was 120 μm. Subsequently, the coating film was dried at a temperature of 50 ° C. to remove the solvent, and then sintered at a temperature of 2400 ° C. in an argon atmosphere to form a carbide sintered body coating on the graphite substrate. The film thickness was 100 μm.

<Evaluation of sintered carbide>
(1) Measurement of area occupancy ratio D An electron microscope observation (XL30-SFEG, manufactured by Japan FI Eye Co., Ltd.) was performed on an arbitrary cross section of the film (carbide sintered body) obtained as described above. In FIG. 1, the electron microscope observation photograph of the cross section of the carbide sintered compact obtained using the paste composition 4 is shown. In the electron microscope observation photograph shown in FIG. 1, an arbitrary observation region of 15 μm × 25 μm is divided into two regions, a sintered body portion (matrix region) and a pore portion (non-matrix region). The area ratio (%) was calculated and used as the area occupation ratio D (%). Moreover, in the electron microscopic observation photograph of FIG. 1, the analysis image binarized by making the closed region which a pore part occupies into a black coating part, and making other than a white coating part is shown in FIG. Using the analysis image of FIG. 2, the area occupation ratio D (%), that is, the ratio of the total area of the white areas other than the pores to the area of the entire observation area of 15 μm × 25 μm was obtained.

(2) Measurement of metal element content I In the observation region of 15 μm × 25 μm where the area occupancy D was measured, mapping was performed by energy dispersive X-ray spectroscopy (manufactured by Oxford Instruments, INCA Xsight), and tantalum The content ratio (mol%) of a metal element other than (Ta) was calculated and used as the metal element content I (mol%). In the case where the content ratio of each metal element was less than the device detection limit (0.15 mol%), the I value was 0 (mol%).

(3) Calculation of pure carbide requirement index S From the values of D and I calculated as described above, the following formula:
S = D × (1−I / 0.6)
Pure carbide requirement index S expressed by The pure carbide requirement index S of each carbide sintered body was as shown in Table 1 below.

As is apparent from the evaluation results in Table 1, the carbide sintered bodies (Examples 1 to 4) obtained using the paste compositions 1 to 4 containing fluoride each have an area occupancy ratio D of 70%. As described above, it can be seen that the sintered body has a high density and a high theoretical density. Moreover, it turns out that the carbide sintered compact (comparative example 1) obtained using the paste composition 5 which uses cobalt as a sintering auxiliary agent is a very high-density sintered compact. On the other hand, the carbide sintered body (Comparative Example 2) obtained using the paste composition 6 containing no sintering aid has an area occupation ratio D of less than 70% and is not a high-density sintered body. Recognize.

Further, among the carbide sintered bodies (Examples 1 to 4) obtained by using the paste composition containing fluoride, Example 4 in which the compounding amount of fluoride is contained as much as 6 mol% with respect to the carbide. Even in this case, it can be seen that almost no fluoride remains in the sintered carbide body (the metal element content is less than the detection limit). On the other hand, since the carbide sintered body of Comparative Example 1 uses cobalt (Co) as a sintering aid, although it is a very high density sintered body, Co remains in the sintered body. I understand that. As a result, the carbide sintered bodies of Examples 1 to 4 had an S value of 0.69 or more, whereas the carbide sintered body of Comparative Example 1 had an S value much lower than these, -0.21. It was.

Claims (11)

1. A carbide having a melting point of 3000 ° C. or higher;
   A fluoride of at least one element selected from Group 2 or Group 3 of the Periodic Table;
   A paste composition comprising:
2. The paste composition according to claim 1, wherein the fluoride is contained at a ratio of 0.5 to 7 mol with respect to 100 mol of the carbide.
3. The paste composition according to claim 1 or 2, wherein the fluoride is calcium fluoride.
4. The paste composition according to any one of claims 1 to 3, wherein the carbide is in the form of particles having an average particle diameter of 0.05 to 20.0 µm.
5. The paste composition according to any one of claims 1 to 4, wherein the fluoride is in the form of particles having an average particle size of 0.1 to 10.0 µm.
6. The paste composition according to any one of claims 1 to 5, further comprising a binder resin.
7. A carbide sintered body of the paste composition according to any one of claims 1 to 6,
   The area occupancy of the sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
   When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
   S = D × (1−I / 0.6)
   The carbide sintered compact whose pure carbide requirement index | exponent S represented by these is S> = 0.69.
8. A fireproof member comprising a base material and a coating covering at least a part of the surface of the base material,
   The coating comprises a carbide sintered body of the paste composition according to any one of claims 1 to 6,
   The carbide sintered body is:
   The area occupancy of the sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
   When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
   S = D × (1−I / 0.6)
   A refractory member having a pure carbide requirement index S represented by: S ≧ 0.69.
9. The fireproof member according to claim 8, wherein the thickness of the coating is 30 to 500 µm.
10. The first base material and the second base material are fire-resistant members formed by bonding via a connecting material,
    The connecting material comprises a carbide sintered body of the paste composition according to any one of claims 1 to 6,
    The carbide sintered body is:
    The area occupancy of the sintered body obtained from the electron microscope observation of the cross section of the carbide sintered body is D (%),
    When the metal element content other than the carbide obtained by energy dispersive X-ray spectroscopy in the cross section is I (mol%), the following formula:
    S = D × (1−I / 0.6)
    A refractory member having a pure carbide requirement index S represented by: S ≧ 0.69.
11. The fireproof member according to claim 10, wherein the thickness of the connecting material is 30 to 500 µm.

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