Cordierite sintered body and method for manufacturing the same

Abstract

The present invention pertains to a cordierite sintered body which contains all elements belonging to an element group M1 comprising calcium, magnesium, aluminum, and silicon, and in which, in terms of oxides, the contained amount of the calcium is 0.06-3.40 mass%, the contained amount of the magnesium is 12.9 mass% or more, the contained amount of an element M2 which is a metal element other than the elements belonging to the element group M1 is 1.5 mass% or less, the degree of porosity is 3.0 vol% or less, the 4-point flexural strength is 170 MPa or more, and the Weibull modulus is 9.5 or more.

Description

[Technical Field]

[0001] The present invention relates to a cordierite sintered body and a method for producing the same. [Background technology]

[0002] Conventionally, sintered bodies containing cordierite (cordierite-based sintered bodies) have been used as components exposed to plasma (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-295863 [Overview of the project] [Problems that the invention aims to solve]

[0004] The inventors of this invention have found that conventional cordierite sintered bodies sometimes have insufficient plasma resistance. Furthermore, depending on the application, cordierite sintered bodies may require excellent thermal shock resistance.

[0005] This invention has been made in view of the above points, and aims to provide a cordierite sintered body and a method for manufacturing the same that are excellent in plasma resistance and thermal shock resistance. [Means for solving the problem]

[0006] As a result of diligent research, the inventors of this invention discovered that the above objective can be achieved by adopting the following configuration, and thus completed the present invention.

[0007] In other words, the present invention provides the following [1] to

[11] . [1] A cordierite sintered body containing all elements belonging to element group M1, which consists of calcium, magnesium, aluminum, and silicon, wherein the calcium content is 0.06% by mass or more and 3.40% by mass or less in terms of oxide, the magnesium content is 12.9% by mass or more in terms of oxide, the content of element M2, which is a metallic element other than the elements belonging to element group M1, is 1.5% by mass or less in terms of oxide, the porosity is 3.0% by volume or less, the four-point bending strength is 170 MPa or more, and the Weibull coefficient is 9.5 or more. [2] The cordierite sintered body according to [1] above, wherein the calcium content is 0.09% by mass or more and 1.80% by mass or less in terms of oxide. [3] The cordierite sintered body according to [1] or [2] above, wherein the aluminum content is 39.0% by mass or less in terms of oxide. [4] A cordierite sintered body according to any of [1] to [3] above, wherein the titanium content is 0.5% by mass or less in terms of oxide. [5] A cordierite sintered body according to any of [1] to [4] above, wherein the total content of iron, nickel, chromium, and manganese is 0.6% by mass or less in terms of oxides. [6] A cordierite sintered body according to any of [1] to [5] above, wherein the alkali metal content is 0.30% by mass or less in terms of oxide. [7] A cordierite sintered body according to any of [1] to [6] above, having a thermal conductivity of 4.0 W / (m·K) or higher. [8] The number of foreign particles containing the above element M2 with an equivalent circle diameter of 5 μm or more is 150 particles / cm 2 The cordierite sintered body described in any of the above [1] to [7], which is as follows: [9] A method for producing a cordierite sintered body according to any of [1] to [8] above, comprising: preparing a molded body using raw material powder; heating the molded body; and using a mixed powder containing cordierite powder produced by an electromelting method, mullite powder, and magnesia powder as the raw material powder.

[10] The method for producing a cordierite sintered body according to [9] above, wherein the mixed powder further contains calcium oxide powder.

[11] A method for producing a cordierite sintered body according to [9] or

[10] above, wherein the cordierite powder is magnetically separated before use. [Effects of the Invention]

[0008] According to the present invention, a cordierite sintered body with excellent plasma resistance and thermal shock resistance, and a method for manufacturing the same can be provided. [Modes for carrying out the invention]

[0009] The meanings of the terms used in this invention are as follows: A numerical range represented using "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively.

[0010] [Sintered body] The cordierite sintered body of the present invention contains all elements belonging to element group M1, which consists of calcium, magnesium, aluminum, and silicon, with a calcium content of 0.06% by mass or more and 3.40% by mass or less in terms of oxide, a magnesium content of 12.9% by mass or more in terms of oxide, and a content of element M2, which is a metallic element other than those belonging to element group M1, of 1.5% by mass or less in terms of oxide, a porosity of 3.0% by volume or less, a four-point bending strength of 170 MPa or more, and a Weibull coefficient of 9.5 or more.

[0011] Hereinafter, the cordierite sintered body will also be simply referred to as the "sintered body," and the cordierite sintered body of the present invention will also be referred to as the "present sintered body."

[0012] This sintered body is a sintered body of a metal oxide containing cordierite. Examples of chemical formulas representing cordierite include, but are not limited to, 2MgO·2Al2O3·5SiO2. This sintered body generally contains, in addition to cordierite (2MgO·2Al2O3·5SiO2), a specific amount of calcium (Ca). Further, the sintered body has a higher content of magnesium (Mg) than ordinary cordierite. And this sintered body exhibits specific values for porosity, four-point bending strength, and Weibull modulus. Such a sintered body is excellent in plasma resistance and thermal shock resistance. Hereinafter, this sintered body will be described in more detail.

[0013] 〈Element group M1〉 As described above, this sintered body contains, in addition to cordierite (2MgO·2Al2O3·5SiO2), calcium (Ca). Therefore, this sintered body contains all the elements belonging to the element group M1, which is a group of metal elements composed of calcium (Ca), magnesium (Mg), aluminum (Al), and silicon (Si).

[0014] 《Ca》 Due to the excellent plasma resistance of this sintered body, the content of Ca is 0.06 mass% or more in terms of oxide conversion, preferably 0.09 mass% or more, more preferably 0.12 mass% or more, still more preferably 0.18 mass% or more, particularly preferably 0.24 mass% or more, and most preferably 0.40 mass% or more. For the same reason and to improve the values of four-point bending strength and Weibull modulus, the content of Ca is 3.40 mass% or less, preferably 2.50 mass% or less, more preferably 1.80 mass% or less, still more preferably 1.20 mass% or less, and particularly preferably 0.80 mass% or less. The content of Ca in terms of oxide conversion specifically means the content of CaO. An appropriate amount of Ca is considered to reduce the deterioration rate by plasma and improve the plasma resistance by adhering the grains constituting the sintered body or dissolving in the grains to strengthen the grains themselves.

[0015] 《Mg》 For the reason that this sintered body has excellent plasma resistance, the Mg content is 12.9% by mass or more, preferably 13.2% by mass or more, more preferably 13.5% by mass or more, even more preferably 14.0% by mass or more, even more preferably 14.5% by mass or more, particularly preferably 15.0% by mass or more, and most preferably 15.5% by mass or more. For similar reasons, the Mg content is preferably 17.5% by mass or less, more preferably 17.0% by mass or less, even more preferably 16.5% by mass or less, and particularly preferably 16.0% by mass or less, in terms of oxides. The Mg content, calculated as an oxide, specifically refers to the MgO content.

[0016] 《Al》 In this sintered body, if the amount of Al is too high, the amount of Mg will relatively decrease. Therefore, from the viewpoint of securing the desired amount of Mg, the Al content is preferably 40.0% by mass or less, more preferably 39.0% by mass or less, even more preferably 38.0% by mass or less, particularly preferably 37.5% by mass or less, and most preferably 37.0% by mass or less, in terms of oxide. Furthermore, if the Al content is too high, the Weibull coefficient tends to decrease. For this reason as well, it is preferable that the Al content be within the above range. On the other hand, the lower limit is not particularly limited, and the Al content, in terms of oxide, is, for example, 30.0% by mass or more, preferably 33.0% by mass or more, more preferably 34.0% by mass or more, even more preferably 34.5% by mass or more, even more preferably 35.0% by mass or more, especially preferably 35.5% by mass or more, and most preferably 36.0% by mass or more. The Al content, calculated as an oxide, specifically refers to the Al2O3 content.

[0017] The content of metallic elements (elements belonging to element group M1 and element M2, excluding Si) in the sintered body is measured using inductively coupled plasma mass spectrometry (ICP-MS). Specifically, the sample is immersed in an extract of HF:HNO3 = 4:1 (mass ratio) for two days, and then heated at 80°C for one hour. After that, the sample is removed using tweezers to obtain an extract in which the metal elements have been extracted from the sample. After drying this extract, it is diluted to 10 mL using HNO3 solution and analyzed using an Agilent Technologies instrument (Agient 8800).

[0018] 《Si》 The Si content, in terms of oxide, is preferably 43.0% by mass or more, more preferably 44.0% by mass or more, even more preferably 45.0% by mass or more, even more preferably 46.0% by mass or more, particularly preferably 46.5% by mass or more, and most preferably 47.0% by mass or more. On the other hand, the Si content is preferably 55.0% by mass or less, more preferably 51.0% by mass or less, even more preferably 50.0% by mass or less, particularly preferably 49.0% by mass or less, and most preferably 48.0% by mass or less, in terms of oxide. The Si content, calculated as an oxide, specifically refers to the SiO2 content.

[0019] The Si content in the sintered body is determined as follows: First, a powdery sample is taken from the center of the sintered body by polishing, and the total amount of oxygen Z1 in the sintered body is determined by infrared absorption spectroscopy using an oxygen / hydrogen analyzer (LECO ROH-600). The amount of oxygen Z3 is calculated by subtracting the amount of oxygen Z2, which is bonded to the elements (excluding silicon atoms) in the sintered body in a stoichiometric composition, from the total amount of oxygen Z1 in the sintered body. In other words, the amount of oxygen Z3 = total amount of oxygen Z1 - amount of oxygen Z2. Assuming that the entire amount of oxygen Z3 is used for bonding with silicon atoms, the amount of oxygen Z3 is converted to the amount of SiO2. The SiO2 equivalent obtained in this way is taken as the oxide-equivalent Si content (SiO2 content) in the sintered body.

[0020] <Element M2> This sintered body contains a low amount of metallic elements other than those belonging to the aforementioned element group M1 (i.e., impurities). As a result, this sintered body has excellent plasma resistance and thermal shock resistance. Specifically, the content of element M2, which is a metallic element other than the elements belonging to element group M1, is 1.5% by mass or less in terms of oxide, preferably 1.1% by mass or less, more preferably 0.7% by mass or less, still preferably 0.5% by mass or less, even more preferably 0.3% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.1% by mass or less. The lower limit is preferably zero (0% by mass).

[0021] Examples of element M2 include at least one element selected from the group consisting of titanium (Ti), iron (Fe), nickel (Ni), chromium (Cr), manganese (Mn), and alkali metals.

[0022] 《Ti》 For the reason that this sintered body has superior plasma resistance, the Ti content is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, even more preferably 0.1% by mass or less, particularly preferably 0.05% by mass or less, and most preferably 0.03% by mass or less, in terms of oxide. The Ti content, calculated as an oxide, specifically refers to the TiO2 content.

[0023] 《Fe, Ni, Cr, and Mn》 The total content of Fe, Ni, Cr, and Mn, in terms of oxides, is preferably 0.6% by mass or less, more preferably 0.4% by mass or less, even more preferably 0.3% by mass or less, even more preferably 0.2% by mass or less, particularly preferably 0.1% by mass or less, and most preferably 0.05% by mass or less. In this case, the generation of foreign particles, as described later, is suppressed, resulting in good four-point bending strength and Weibull coefficient, and thus superior thermal shock resistance of the sintered body.

[0024] The Fe content, calculated as an oxide, specifically refers to the Fe2O3 content. The Ni content, when expressed as an oxide, specifically refers to the NiO content. The Cr content, calculated as an oxide, specifically refers to the Cr2O3 content. The Mn content, when expressed as an oxide, specifically refers to the MnO content.

[0025] Alkali metals For the reason that the porosity of the sintered body is lower and the plasma resistance and thermal shock resistance of the sintered body are better, the alkali metal content is preferably 0.30% by mass or less, more preferably 0.20% by mass or less, even more preferably 0.15% by mass or less, particularly preferably 0.12% by mass or less, and most preferably 0.09% by mass or less, in terms of oxide. However, for similar reasons, it is preferable that some alkali metals be included. Specifically, the alkali metal content is preferably 0.01% by mass or more, and more preferably 0.03% by mass or more, in terms of oxides.

[0026] Examples of alkali metals include lithium (Li), sodium (Na), and potassium (K). The Li content, calculated as an oxide, specifically refers to the content of Li2O. The sodium content, calculated as an oxide, specifically refers to the amount of Na2O present. The K content, when expressed as an oxide, specifically refers to the K2O content.

[0027] Other elements Other elements that qualify as element M2 include, for example, copper (Cu), zinc (Zn), zirconium (Zr), gallium (Ga), phosphorus (P), and sulfur (S). Note that although P and S are not metallic elements, they are treated as metallic elements when considered as element M2. The content of other elements, in terms of oxides, is preferably 0.04% by mass or less in total, more preferably 0.04% by mass or less, and even more preferably 0.03% by mass or less. The copper content, when expressed as an oxide, specifically refers to the content of CuO. The Zn content, calculated as an oxide, specifically refers to the ZnO content. The Zr content, calculated as an oxide, specifically refers to the ZrO2 content. The Ga content, when expressed as an oxide, specifically refers to the Ga2O3 content. The P content, when expressed as an oxide, specifically refers to the P2O5 content. The sulfur content, when expressed as an oxide, specifically refers to the SO3 content.

[0028] <Porosity> For the reasons that this sintered body has excellent plasma resistance and thermal shock resistance, the porosity of this sintered body is 3.0 volume% or less, preferably 1.5 volume% or less, more preferably 0.5 volume% or less, even more preferably 0.3 volume% or less, particularly preferably 0.1 volume% or less, and most preferably 0.05 volume% or less. The lower limit is preferably zero (0 volume%).

[0029] In order to achieve the above-mentioned porosity, it is preferable to use the above-mentioned content of each component and to manufacture the sintered body by the method described later (this manufacturing method). In particular, it is preferable to use cordierite powder produced by electrofusion as the raw material powder.

[0030] Porosity is determined in accordance with the method for calculating open porosity described in JIS R 1634:1998 "Method for measuring density and open porosity of sintered fine ceramics".

[0031] <4-point bending strength> Due to its excellent thermal shock resistance, the four-point bending strength of this sintered body is 170 MPa or higher, preferably 180 MPa or higher, more preferably 190 MPa or higher, even more preferably 200 MPa or higher, even more preferably 210 MPa or higher, particularly preferably 220 MPa or higher, and most preferably 230 MPa or higher. There is no particular upper limit, but the four-point bending strength of the sintered body is, for example, 300 MPa or less, and preferably 250 MPa or less.

[0032] The four-point bending strength is measured in accordance with JIS R 1601 (2008) on a sintered body test specimen (flat plate, 50 mm in length, 4 mm in width, and 3 mm in thickness) under conditions of 25°C.

[0033] In order to achieve the four-point bending strength within the above range, it is preferable to use the above-mentioned content for each component and to manufacture the sintered body by the method described later (this manufacturing method). In particular, when the content of Fe, Ni, Cr, and Mn is high, it is difficult to obtain such four-point bending strength.

[0034] <Weibull coefficient> For the reason that this sintered body has excellent thermal shock resistance, the Weibull coefficient of this sintered body is 9.5 or higher, preferably 10.0 or higher, more preferably 10.5 or higher, even more preferably 11 or higher, even more preferably 11.5 or higher, particularly preferably 12 or higher, and most preferably 12.5 or higher. There is no particular upper limit, but the Weibull coefficient of the sintered body is, for example, 14 or less, and preferably 13 or less.

[0035] The Weibull coefficient (the Weibull coefficient for four-point bending strength) is an indicator of the degree of variation in four-point bending strength; a larger value means less variation in four-point bending strength. The Weibull coefficient is determined as follows: First, the four-point bending strength of 30 test specimens is measured using the method described above. Next, the Weibull coefficient is calculated using the data from the 30 measured bending strengths in accordance with JIS R 1625 (2010).

[0036] In order to bring the Weibull coefficient within the above range, it is preferable to use the above-mentioned content for each component and to manufacture the sintered body by the method described later (this manufacturing method). In particular, when the content of Fe, Ni, Cr, and Mn is high, it is difficult to obtain such a Weibull coefficient.

[0037] <Thermal conductivity> For the reason that this sintered body has superior thermal shock resistance, the thermal conductivity of this sintered body is preferably 4.0 W / (m·K) or higher, more preferably 4.2 W / (m·K) or higher, even more preferably 4.4 W / (m·K) or higher, even more preferably 4.6 W / (m·K) or higher, particularly preferably 4.8 W / (m·K) or higher, and most preferably 5.0 W / (m·K) or higher. There is no particular upper limit, but the thermal conductivity of the sintered body is, for example, 6.0 W / (m·K) or less, and preferably 5.5 W / (m·K) or less.

[0038] The thermal conductivity is measured on a sintered body test specimen (12 mm x 12 mm plate, 6.0 mm thick) using a NETZSCH laser flash thermophysical property measurement device, the "Xenon Flash Analyzer LFA 467 HyperFlash," under conditions of 21°C.

[0039] In order to achieve the thermal conductivity within the above range, it is preferable to use the above-mentioned amounts for each component and to manufacture the sintered body by the method described later (this manufacturing method). In this way, it is preferable to obtain a dense sintered body with reduced impurities.

[0040] <Amount of foreign particles (number of foreign particles)> Using a scanning electron microscope (SEM), the sintered body was observed at a magnification of 1,000x, and SEM images of any 50 fields of view were obtained. The obtained SEM images are then analyzed using the EDX (Energy Dispersive X-ray Spectroscopy) instrument attached to the SEM to identify foreign particles containing element M2 (particles composed of element M2). Of the identified foreign particles, the number of foreign particles with an equivalent circle diameter of 5 μm or more (unit: particles / cm²) is then calculated. 2 The number of foreign particles in the sintered body is measured and the average value of 50 fields of view is calculated. The calculated average value is taken as the number of foreign particles in the sintered body. In this specification, the number of such foreign particles may be conveniently referred to as the "amount of foreign phase".

[0041] Since the four-point bending strength and Weibull coefficient of this sintered body are good and its thermal shock resistance is more excellent, the number of foreign particles containing element M2, that is, the number of foreign particles with a circle equivalent diameter of 5 μm or more, is 150 particles / cm 2 The following is preferable, 100 particles / cm 2 The following is more preferable, 50 particles / cm 2 The following is still more preferable, 30 particles / cm 2 The following is even more preferable, 10 particles / cm 2 The following is particularly preferable, 5 particles / cm 2 The following is most preferable. The lower limit is zero (0 particles / cm 2 ).

[0042] In order to make the amount of the second phase within the above range, it is preferable that each component has the above-described content and the sintered body is manufactured by the method (this manufacturing method) described below.

[0043] 〈Shape and Application〉 Examples of the shape of this sintered body include plate shape (for example, disk shape, flat plate shape), spherical shape, and ellipsoidal shape, and it is appropriately selected according to the application. This sintered body is preferably used as a susceptor material for supporting a wafer in a semiconductor manufacturing apparatus, but the application of this sintered body is not limited thereto. '

[0044] [Manufacturing Method of Sintered Body] Next, a method for manufacturing this sintered body (hereinafter, also referred to as "this manufacturing method") will be described. This manufacturing method is generally a method of producing a molded body using raw material powder and heating this molded body. Hereinafter, this manufacturing method will be described in detail.

[0045] 〈Raw Material Powder〉 As the raw material powder, a mixed powder containing cordierite powder, mullite powder, and magnesia powder produced by an electric melting method is used.

[0046] 《Cordierite Powder》 Cordierite (2MgO·2Al2O3·5SiO2) powder is the raw material for Mg, Al, and Si that make up this sintered body. Furthermore, cordierite powder may contain Ca as an impurity, in which case it supplies the Ca that constitutes the sintered body.

[0047] (Electrofused cordierite powder) In this manufacturing method, cordierite powder produced by the electrofusion method (also referred to for convenience as "electrofused cordierite powder") is used. The general method for obtaining electrofused cordierite powder is as follows: First, the raw materials for the electrofused cordierite powder are placed in a crucible. Examples of raw materials for electrofused cordierite powder include magnesia (MgO), alumina (Al2O3), and silica (SiO2). These raw materials may contain impurities such as calcium (Ca). Next, for example, the raw materials in the crucible are melted by generating plasma using carbon electrodes. Afterward, the molten raw material is blown and rapidly cooled. This process yields fused cordierite powder. Fused cordierite powder is an amorphous substance (powder) that contains some crystals. The particles that make up the fused cordierite powder are spherical and uniform in size; in other words, it is homogeneous. Therefore, electrofused cordierite powder is easily sintered in the presence of mullite powder, which is a sintering aid described later. In other words, it has good sinterability. As a result, a dense sintered body can be obtained, and the porosity can be reduced. Furthermore, impurities such as Ti can be reduced by manufacturing it using the electrofusion method. Commercially available electrofused cordierite powder can be used, and a suitable example is ELP-150FINE (manufactured by AGC Ceramics Inc.).

[0048] Mullite powder Mullite is represented by chemical formulas such as 3Al2O3·2SiO2 and 2Al2O3·SiO2. Mullite powder is used as a sintering aid. By using mullite powder as a sintering aid, a dense sintered body can be obtained. Mullite powder is a raw material for the Al and Si components that make up this sintered body.

[0049] Magnesia powder Magnesia (MgO) powder is the raw material for the Mg that makes up this sintered body. As mentioned above, since this sintered body has a higher Mg content than ordinary cordierite, magnesia powder is also used as a raw material powder.

[0050] Calcium oxide powder The raw material powder may further contain calcium oxide (CaO) powder. As mentioned above, this sintered body contains Ca in addition to cordierite. Therefore, if the amount of Ca contained as an impurity in the cordierite powder is insufficient, calcium oxide powder is used as an additional raw material powder.

[0051] 《Magnetic selection》 It is preferable that the powders used as raw materials, especially the electrofused cordierite powder, be magnetically separated before use. This makes it possible to reduce the content of metallic elements M2 (Ti, Fe, etc.), other than the elements belonging to element group M1 (Ca, Mg, Al, and Si), in the final sintered body. As for the magnetic separation method, for example, a method using a wet magnetic filter is preferred. The magnetic separation conditions are not particularly limited and can be adjusted as appropriate, for example, so that the resulting sintered body has a desired content of element M2.

[0052] Preparation of raw material powder The aforementioned powders are magnetically separated as needed and then mixed. This yields a raw material powder, which is a mixture of the individual powders. The mixing method is not particularly limited, and conventionally known methods can be used. The content of each powder in the raw material powder (mixed powder) is adjusted as appropriate so that the content of each component in the final sintered body is in the desired amount. From the viewpoint of improving sinterability during heating, as described later, it is preferable to pulverize the mixed powder to reduce its particle size. Specifically, the average particle size of the pulverized mixed powder is preferably 10 μm or less, and more preferably 2 μm or less. The average particle size is determined by the particle size at 50% of the integrated value in the particle size distribution (D) determined by laser diffraction and scattering. 50 ) (and so on). The grinding method is not particularly limited and can be used with a ball mill, attritor, bead mill, jet mill, etc. When grinding using a wet process, the resulting mixed powder is dried.

[0053] <Preparation of molded body> Next, a molded body is prepared using the raw material powder (mixed powder). That is, it is molded. The molding method is not particularly limited, and general molding methods can be used. For example, molding can be performed using a hydrostatic press with an applied pressure of 100 MPa to 200 MPa. Alternatively, a mixture of mixed powder and an organic binder may be formed into a predetermined shape by press molding, extrusion molding, sheet molding, or the like. The shape obtained by molding is selected appropriately according to the intended use of the resulting sintered body.

[0054] <heating> Next, the resulting molded body is heated. This yields a sintered body. From the viewpoint of improving sinterability, the heating temperature (maximum temperature during heating) is preferably 1400°C or higher, more preferably 1410°C or higher, and even more preferably 1430°C or higher. On the other hand, if the heating temperature is too high, part of the resulting sintered body may melt and break, or a sintered body of the desired dimensions may not be obtained. For this reason, the heating temperature is preferably 1450°C or lower, and more preferably 1440°C or lower. The heating time (holding time at the maximum temperature) is preferably 1 hour or more, more preferably 2 hours or more, and even more preferably 5 hours or more. On the other hand, the heating time is preferably 48 hours or less, more preferably 12 hours or less, and even more preferably 8 hours or less. The atmosphere used during heating (heating atmosphere) is not particularly limited and can include, for example, an atmospheric atmosphere; an inert atmosphere such as a nitrogen or argon atmosphere; a reducing atmosphere such as a hydrogen atmosphere or a mixture of hydrogen and nitrogen; and so on.

[0055] The resulting sintered body is preferably densified. Densification is carried out, for example, using a hot isotropic hydrostatic press. Specifically, for example, a hot isotropic hydrostatic press is used to apply a pressure of 100 MPa to 200 MPa while heating at a temperature of 1000°C to 1350°C. [Examples]

[0056] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below. Examples 1-2, 5-9, 11-12, 14-17, 19-21, and 23-25 ​​are examples, while examples 3-4, 10, 13, 18, and 22 are comparative examples.

[0057] <Examples 1-25> The sintered bodies for each example were obtained as follows.

[0058] 《Raw material powder》 Electrofused cordierite (2MgO·2Al2O3·5SiO2) powder, mullite (3Al2O3·2SiO2) powder as a sintering aid, magnesia (MgO) powder, and calcium oxide (CaO) powder were mixed together. As the electrofused cordierite powder, we used "ELP-150FINE" (average particle size: 14.1 μm) manufactured by AGC Ceramics Inc. For the mullite powder, we used "KM101" (average particle size: 0.8 μm) manufactured by Kyoritsu Material Co., Ltd. Specifically, the powders were mixed so that the content of elements belonging to element group M1 and element M2 in the resulting sintered body would be the values ​​shown in Tables 1 to 3 below, thereby obtaining a mixed powder, which is the raw material powder. At this time, other metal oxide powders, such as titanium dioxide (TiO2) powder, were added as needed.

[0059] Each powder was magnetically separated before mixing. Specifically, a slurry (concentration: 15 vol%) in which each powder was dispersed in water was magnetically separated three times under conditions of 2.8 Tesla using a wet magnetic filter (a "Wet High Magnetic Flux Tester FG type" manufactured by Nippon Magnetic Separation Co., Ltd.). However, in Examples 16-18, magnetic separation was not performed on each powder.

[0060] The raw material powder (mixed powder) was wet-mixed and pulverized using a ball mill with high-purity alumina balls, with ethanol as the dispersion medium. The average particle size (D) of the pulverized raw material powder was determined. 50 The diameter was 2.0 μm.

[0061] 《Fabrication and heating of molded bodies》 The obtained raw material powder (mixed powder) was pressurized at room temperature using a hydrostatic press with a pressure of 180 MPa to produce a molded body. Next, the fabricated molded body was heated in air to obtain a sintered body. The heating temperature was 1430°C and the heating time was 5 hours. Furthermore, the resulting sintered bodies were densified. Specifically, they were heated at 1300°C while applying a pressure of 145 MPa using a hot isotropic hydrostatic press. However, densification was not performed in Examples 24-25.

[0062] <Content of elements belonging to element group M1 and element M2> For each example of sintered body, the oxide content of elements belonging to element group M1 and element M2 was determined using the method described above. The results are shown in Tables 1-3 below.

[0063] <Porosity, etc.> For each example of sintered body, the porosity, amount of different phases, four-point bending strength, Weibull coefficient, and thermal conductivity were determined using the method described above. The results are shown in Tables 1-3 below.

[0064] <Thermal shock resistance test> A test piece measuring 15mm x 5mm x 100mm was cut from the sintered body. The test specimens were heated at 350°C for 60 minutes, and then immersed in water at room temperature. Next, the test specimens were removed from the water, and cracks in the specimens were stained using a dye penetrant (manufactured by Taseto Co., Ltd., penetrant FP-S and developer FD-S), and then visually inspected. Tables 1-3 below indicate the following: "○" if no cracks longer than 3mm were found, "△" if one or two cracks longer than 3mm were found, and "×" if three or more cracks longer than 3mm were found. A rating of "○" or "△" indicates excellent thermal shock resistance.

[0065] <Etching amount> For each example of a sintered body, the amount of etching was determined, and its plasma resistance was evaluated. Specifically, a test piece measuring 10 mm x 5 mm x 4 mm was cut from the sintered body, and the 10 mm x 5 mm surface was polished to a mirror finish. A portion of the mirror-polished surface was masked with Kapton® tape and etched with plasma gas. Subsequently, the amount of etching was determined by measuring the step difference between the etched and unetched areas using a stylus-type surface shape measuring instrument (ULVAC, Inc., Decak150). An EXAM plasma etching system (manufactured by Shinko Seiki Co., Ltd., model: POEM) was used. Etching was performed in RIE mode (reactive ion etching mode) with CF4 gas for 390 minutes at a pressure of 10 Pa and an output of 350 W. The smaller the etching amount (in nm), the better the plasma resistance can be evaluated. Specifically, if the etching amount is 420 nm or less, it was evaluated as having excellent plasma resistance.

[0066] [Table 1]

[0067] [Table 2]

[0068] [Table 3]

[0069] <Summary of Evaluation Results> As shown in Tables 1-3 above, the sintered bodies of Examples 1-2, 5-9, 11-12, 14-17, 19-21, and 23-25 ​​were found to have excellent plasma resistance and thermal shock resistance.

[0070] In contrast, the sintered bodies of Examples 3-4, 10, 13, 18, and 22 had insufficient plasma resistance and thermal shock resistance. Specifically, it was as follows: In Example 3, the MgO content was less than 12.9% by mass, resulting in a large etching amount and insufficient plasma resistance. In Example 4, the CaO content was less than 0.06 mass%, resulting in a large etching amount and insufficient plasma resistance. In Example 10, the MgO content was less than 12.9% by mass, resulting in a large etching amount and insufficient plasma resistance. Furthermore, Example 10 had a CaO content exceeding 3.40 mass%, a four-point bending strength of less than 170 MPa, and a Weibull coefficient of less than 9.5, indicating insufficient thermal shock resistance. Example 13 had a CaO content of less than 0.06 mass%, a large etching amount, and insufficient plasma resistance. Example 18 had a CaO content of less than 0.06 mass%, a large etching amount, and insufficient plasma resistance. Furthermore, Example 18 had a Weibull coefficient of less than 9.5, indicating insufficient thermal shock resistance. Example 22 had a Weibull coefficient of less than 9.5, indicating insufficient thermal shock resistance.

[0071] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2021-035458, filed on March 5, 2021, the contents of which are incorporated herein by reference.

Claims

1. It contains all the elements belonging to element group M1, which consists of calcium, magnesium, aluminum, and silicon. The calcium content is 0.06% by mass or more and 3.40% by mass or less, in terms of oxides. The magnesium content is 12.9% by mass or more, in terms of oxides. The content of element M2, which is a metallic element other than the elements belonging to the aforementioned element group M1, is 1.5% by mass or less in terms of oxides. The total content of iron, nickel, chromium, and manganese is 0.1% by mass or less in terms of oxides. The porosity is 3.0% by volume or less. The four-point bending strength is 170 MPa or higher. The Weibull coefficient is 9.5 or higher. A cordierite sintered body using a mixed powder containing cordierite powder, mullite powder, and magnesia powder, all produced by an electromelting method, as raw material powders.

2. The cordierite sintered body according to claim 1, wherein the calcium content is 0.09% by mass or more and 1.80% by mass or less, in terms of oxide.

3. The cordierite sintered body according to claim 1 or 2, wherein the calcium content is 0.247% by mass or less in terms of oxide.

4. The cordierite sintered body according to any one of claims 1 to 3, wherein the aluminum content is 39.0% by mass or less in terms of oxide.

5. The cordierite sintered body according to any one of claims 1 to 4, wherein the aluminum content is 35.5% by mass or more in terms of oxide.

6. The cordierite sintered body according to any one of claims 1 to 5, wherein the magnesium content is 13.5% by mass or more in terms of oxide.

7. A cordierite sintered body according to any one of claims 1 to 6, wherein the titanium content is 0.5% by mass or less in terms of oxide.

8. A cordierite sintered body according to any one of claims 1 to 7, wherein the alkali metal content is 0.30% by mass or less in terms of oxide.

9. A cordierite sintered body according to any one of claims 1 to 8, wherein the thermal conductivity is 4.0 W / (m·K) or higher.

10. The number of foreign particles containing the element M2, with an equivalent circular diameter of 5 μm or more, is 150 particles / cm². ２ The cordierite sintered body according to any one of claims 1 to 9, which is as follows:

11. The cordierite sintered body according to any one of claims 1 to 10, wherein the mixed powder further contains calcium oxide powder.

12. A method for producing a cordierite sintered body according to any one of claims 1 to 11, A molded body is prepared using the raw material powder. The molded body is heated, A method for producing a cordierite sintered body, wherein the raw material powder used is a mixed powder containing cordierite powder produced by an electromelting method, mullite powder, and magnesia powder.

13. The method for producing a cordierite sintered body according to claim 12, wherein the mixed powder further contains calcium oxide powder.

14. A method for producing a cordierite sintered body according to claim 12 or 13, wherein the cordierite powder is magnetically separated before use.

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