JP2018131362A - Sintered body and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered body having excellent heat impact resistance and conductivity while having corrosion resistance suitable as a constituent material of a semiconductor manufacturing apparatus such as an etching apparatus and a method for producing the same. SOLUTION: The sintered body contains an oxyfluoride and a carbonaceous material. The carbonaceous material is preferably carbon powder and / or carbon fiber. It is also preferable that the carbonaceous material is in the form of particles having an average particle size of 0.1 to 10 μm, or that the carbonaceous material is in the form of fibers having a diameter of 1 to 20 or less and a length of 30 to 500 μm. A sintered body containing 0.1 to 30 volumes of the carbonaceous material. A sintered body having a volume resistance of 1 to 1010 Ω · cm is preferable. [Selection diagram] Fig. 1

Description

  The present invention relates to a sintered body and a method for producing the same.

  In the manufacture of semiconductors, fluorine-based corrosive gas, chlorine-based corrosive gas, and plasma using these are used in processes such as dry etching, plasma etching, and cleaning. Due to these corrosive gases and plasma, the constituent members of the semiconductor manufacturing apparatus are easily corroded, and fine particles peeled off from the surface of the constituent members are likely to adhere to the semiconductor surface and cause product defects. Therefore, ceramics having high corrosion resistance against halogen plasma is used as a bulk material for the constituent members of the semiconductor manufacturing apparatus. As one of such bulk materials, Patent Document 1 proposes yttrium oxyfluoride. The yttrium oxyfluoride described in Patent Document 1 has higher corrosion resistance than the conventionally used quartz and YAG against a highly reactive halogen-based corrosive gas and its plasma.

Patent Document 2 proposes a sintered body of a rare earth element oxyfluoride (hereinafter also referred to as “rare earth oxyfluoride”). This sintered body is composed of yttrium oxyfluoride represented by YOF or Y ₅ O ₄ F ₇ in the composition formula. This sintered body exhibits excellent corrosion resistance against halogen-based plasma, and is useful as a constituent material for semiconductor manufacturing apparatuses such as etching apparatuses.

  On the other hand, in Patent Document 3, a step of mixing a yttrium oxide slurry obtained by dispersing yttrium oxide in a solvent and a fibrous carbon slurry obtained by dispersing fibrous carbon in a solvent to form a mixed slurry; A step of drying or drying and granulating the mixed slurry to obtain a dried product or a granulated product, and the dried product or the granulated product at a temperature of 1460 ° C. or more and less than 1600 ° C. and 1 MPa or more and 20 MPa or less. A sintered body containing carbon fibers in yttrium oxide by a method for producing a sintered body having a step of firing under pressure to form a sintered body containing yttrium oxide and fibrous carbon. It is described that it was obtained.

JP 2000-239067 A Japanese Patent Laid-Open No. 2006-98143 JP2015-59067A

As described above, a constituent material of a semiconductor manufacturing apparatus such as an etching apparatus is required to have high thermal shock resistance in addition to high corrosion resistance against a halogen-based corrosive gas and plasma thereof. However, rare earth oxyfluoride sintered bodies generally have insufficient thermal shock resistance, and there is a risk of cracking depending on temperature changes during use. In addition, yttrium oxyfluoride is an insulator and may be difficult to use in applications where electrical conductivity is required. From this point of view, the rare earth oxyfluoride sintered bodies described in Patent Documents 1 and 2 have insufficient thermal shock resistance and electrical conductivity, and still have room for improvement.
Further, the sintered body containing yttria described in Patent Document 3 does not have sufficient corrosion resistance against plasma. In addition, the technique of incorporating the carbon fiber described in Patent Document 3 into the sintered body has been difficult to adopt for a system containing fluorine such as rare earth oxyfluoride.

  Therefore, the subject of this invention exists in the further improvement of the sintered compact of rare earth oxyfluoride. That is, an object of the present invention is to provide a material having higher thermal shock resistance and conductivity than the conventional one while having corrosion resistance of the sintered body of rare earth oxyfluoride.

  The present invention provides a sintered body containing a rare earth element oxyfluoride and a carbonaceous material.

The present invention is also a method for producing the sintered body,
Treating the carbonaceous material with an oxidizing agent;
A step of preparing a slurry by dispersing a carbonaceous material after treatment with an oxidizing agent, and a rare earth element oxide and a rare earth element fluoride in a dispersion medium;
The manufacturing method of a sintered compact provided with the process of baking the dried material or granulated material of the said slurry.

  ADVANTAGE OF THE INVENTION According to this invention, the sintered compact excellent in the thermal shock resistance and electroconductivity is provided, providing corrosion resistance suitable as a constituent material of semiconductor manufacturing apparatuses, such as an etching apparatus.

FIG. 1 is a scanning electron microscope image of the sintered body taken in Example 1. FIG. 2 is a scanning electron microscope image of the sintered body taken for Example 3.

Hereinafter, the present invention will be described based on preferred embodiments thereof.
The sintered body of the present embodiment is composed of a rare earth oxyfluoride and a carbonaceous material. For reasons described later, a sintered body containing a rare earth oxyfluoride and a carbonaceous material cannot be obtained even if the conventional manufacturing method described in Patent Document 3 relating to an yttrium oxide sintered body is used as it is. The sintered body of the present embodiment is excellent in corrosion resistance, thermal shock resistance and conductivity.
In the sintered body, the carbonaceous material is dispersed in the rare earth oxyfluoride.

  Examples of the carbonaceous material include carbon powder and / or carbon fiber. Carbon powder refers to a particulate carbonaceous material. As used herein, the particle shape includes a scale shape, a spherical shape, a plate shape, and the like. The particulate form preferably means that the aspect ratio (longest diameter / shortest diameter) of the carbon particles is 1.0 or more and 10 or less when the sintered body is observed with a scanning electron microscope.

  Specific examples of the carbon powder include graphite such as flaky graphite, scaly graphite, expanded graphite, expanded graphite, and spherical graphite, carbon beads, ketjen black, and carbon black.

  As the carbon powder, a spherical powder is particularly preferable because it is easy to disperse in the rare earth oxyfluoride and hardly becomes a source of destruction due to stress concentration. The spherical shape preferably refers to those having an aspect ratio (longest diameter / shortest diameter) in the range of 1.0 to 3.0. In particular, the spherical carbon powder preferably has a circular observation image observed with a scanning electron microscope. This circular shape may be not only a perfect circular shape but also an elliptical shape.

  Carbon fiber refers to a fibrous carbonaceous material, and specific examples include PAN-based carbon fiber, pitch-based carbon fiber, graphite fiber, vapor-grown carbon fiber, and carbon nanotube. The carbon fiber preferably refers to a carbon fiber having an aspect ratio (fiber length / fiber diameter) of more than 3.0 and 100 or less when the sintered body is observed with a scanning electron microscope. The carbon fibers are preferably those having the aspect ratio (fiber length / fiber diameter) of 3.5 or more and 20 or less from the viewpoint of ease of dispersion in the rare earth oxyfluoride and ease of fiber loosening, What is 4.0 or more and 10 or less is preferable. Those that are difficult to disperse and those that are not entangled with fibers are not preferred because sintering does not proceed sufficiently and the density of the sintered body is reduced.

  The above aspect ratios are obtained from the average of the aspect ratios of 20 or more carbon particles and / or carbon fibers when the carbon powder and / or carbon fibers are observed with a scanning electron microscope. The observation magnification is not particularly limited as long as the whole image can be observed and can be measured accurately, but is preferably 100 times or more and 2000 times or less.

  In this embodiment, when the carbonaceous material is in the form of particles, the average particle size is 0.1 μm or more, and the carbonaceous material is randomly dispersed even in the rare earth oxyfluoride in which the carbonaceous material is likely to aggregate. From the viewpoint of easily obtaining a sintered body and manufacturing cost. When the carbonaceous material is in the form of particles, the average particle size is preferably 10 μm or less from the viewpoint of uniformly arranging the carbonaceous material inside the fired body. An average particle size exceeding 10 μm is not preferable because it tends to become a fracture source after sintering. From these viewpoints, the average particle size is more preferably 0.2 μm to 8 μm, and more preferably 0.4 μm to 6 μm.

  When the carbonaceous material is fibrous, the diameter thereof is 1 μm or more, and it is easy to obtain a sintered body in which the carbonaceous material is randomly dispersed even in the rare earth oxyfluoride in which the carbonaceous material is likely to aggregate. This is preferable from the viewpoint of manufacturing cost. Further, when the carbonaceous material is fibrous, the diameter is preferably 20 μm or less. If the diameter exceeds 20 μm, it tends to be a source of destruction, which is not preferable. From these viewpoints, the diameter is more preferably 1.1 μm or more and 18 μm or less, and further preferably 1.2 μm or more and 15 μm or less.

  When the carbonaceous material is fibrous, its length is preferably 30 μm or more from the viewpoint of easily increasing conductivity and improving thermal shock resistance by improving thermal conductivity. When the carbonaceous material is fibrous, the length is preferably 500 μm or less from the viewpoint of ease of dispersion and ease of fiber loosening. Those that are difficult to disperse and those that do not loosen the fibers are not preferable because the sintering does not proceed sufficiently and the density of the sintered body becomes low. From these viewpoints, the length is more preferably 35 μm or more and 400 μm or less, and further preferably 40 μm or more and 300 μm or less.

  The particle diameter, diameter, and length of the carbonaceous material described above can be measured by the method described in Examples described later. Preferably, the particle size of the particulate carbonaceous material described above refers to the particle size of a single particle. Similarly, preferably, the diameter and length of the fibrous carbonaceous material described above refer to the diameter and length of a single fiber.

  The amount of the carbonaceous material in the sintered body is preferably 0.1% by volume or more from the viewpoint of reducing the volume resistivity described later to a desired value and increasing the thermal shock resistance. Moreover, it is preferable that the quantity of the carbonaceous material in a sintered compact is 30 volume% or less. If the amount of the carbonaceous material exceeds 30% by volume, the plasma resistance of the rare earth oxyfluoride is impaired, and the strength is not preferable. From these points, the amount of the carbonaceous material in the sintered body is more preferably 1% by volume to 25% by volume, and further preferably 5% by volume to 20% by volume. The amount of carbon is calculated based on the area ratio of the carbonaceous material in the image observed by the scanning electron microscope. Specifically, the amount of carbon is calculated by the method described in the examples described later.

  The fact that the carbonaceous material is randomly dispersed in the sintered body means, for example, that the carbonaceous material in the observation image of a plurality of fields of view by a scanning electron microscope in a cross section obtained by cutting the sintered body at an arbitrary position. It can be calculated from the variation of the area ratio, and preferably, when the area ratio of the carbonaceous material in each field of view is obtained by observing at 100 to 2000 times with a scanning electron microscope, the area ratio of 10 fields or more The variation (maximum value−minimum value) is 10% or less with respect to the average value of the area ratio of the carbonaceous material. Further, in the sintered body, the carbonaceous materials are preferably dispersed without forming an aggregate from the viewpoint of increasing the strength and increasing the density. The fact that the carbonaceous material does not form aggregates means that when the carbonaceous material alone is not in contact with other simplexes when 20 or more carbonaceous materials are observed with a scanning electron microscope at 100 to 2000 magnifications. It means that the ratio of the number is 80% or more.

  The carbonaceous material contained in the sintered body is preferably subjected to surface oxidation treatment, reflecting that it is sufficiently dispersed in the sintered body.

The rare earth oxyfluoride contained in the sintered body of the present embodiment is a compound composed of rare earth elements (Ln), oxygen (O), and fluorine (F). In the composition formula, xLn ₂ O ₃ .yLnF ₃ (Ln represents a rare earth element. X and y are each independently a natural number of 1 or more and excluding LnOF) (hereinafter simply referred to as “xLn ₂ O ₃ · yLnF ₃ )) or a compound represented by a composition formula LnOF (Ln represents a rare earth element) increases the strength of the sintered body To preferred. xLn ₂ O ₃ .yLnF ₃ preferably has an orthorhombic or tetragonal crystal structure, and xLn ₂ O ₃ .yLnF ₃ is identified as this crystal structure in X-ray diffraction. It is suitably included in the category. On the other hand, LnOF preferably has a cubic crystal structure, and includes those identified as this crystal structure in X-ray diffraction.

  LnOF is preferably stabilized with Ca, and LnOF stabilized with Ca has a cubic crystal structure.

Both xLn ₂ O ₃ .yLnF ₃ and Ca-stabilized LnOF are stabilized so as not to cause phase transformation within a wide temperature range. These stable temperature ranges are generally 25 ° C. or more and 1500 ° C. or less.

Expressed by the composition formula xLn ₂ O ₃ · yLnF ₃ (wherein x and y are each independently a natural number of 1 or more), in other words, an attachment in a rare earth oxyfluoride generally expressed by Ln _a O _b F _c This means that the letters a, b, and c satisfy the relationship of a = 2x + y, b = 3x, and c = 3y (x and y are as defined above). Specific examples of “xLn ₂ O ₃ .yLnF ₃ ” include 4Y ₂ O ₃ .7YF ₃ (Y ₅ O ₄ F ₇ ) when Ln is Y, for example. Moreover, when Ln is La, for example, 7La ₂ O ₃ .16LaF ₃ (La ₁₀ O ₇ F ₁₆ ) is exemplified. Moreover, when Ln is Nd, for example, 67Nd ₂ O ₃ .166NdF ₃ (NdO _0.67 F _1.66 ) can be mentioned. When Ln is, for example, Eu, 5Eu ₂ O ₃ · 8EuF ₃ (Eu ₆ O ₅ F ₈ ) is exemplified. Of these rare earth oxyfluorides, Y ₅ O ₄ F _7, NdO _0.67 F _1.66 and Eu ₆ O ₅ F ₈ preferably have an orthorhombic crystal form. Further, La ₁₀ O ₇ F ₁₆ preferably has a tetragonal crystal form.

  Regarding Ca-stabilized LnOF, when LnOF is stabilized by Ca, the cubic state of LnOF in a low-temperature phase of less than 550 ° C. is stabilized as compared to pure LnOF, and around 550 ° C. ( For example, it means that no phase transformation occurs at 400 ° C. or more and 700 ° C. or less. For example, LnOF stabilized by Ca has a cubic crystal phase at 25 ° C. In this embodiment, it is confirmed by the following method that LnOF is stabilized by Ca, for example.

  The sintered body is subjected to powder X-ray diffraction measurement at room temperature, for example, at 25 ° C. in the range of 2θ = 10 ° to 90 °. In the following description, the case where Ln (rare earth element) is Y is taken as an example, but other rare earth elements may be considered in the same manner except that the detected peak angle is slightly shifted. Whether YOF is stabilized by Ca is determined by the presence or absence of a specific peak of cubic crystals. The specific peak is a reflection peak from the (111) plane of cubic YOF observed near 2θ = 28.8 °. Judgment is made based on whether or not this peak is the strongest peak compared to other peaks. This peak overlaps with the peak from the (012) plane of rhombohedral YOF observed near 2θ = 28.7 ° and cannot be separated, but the rhombohedral YOF observed near 2θ = 28.4 ° By looking at the intensity of the reflection peak from the (006) plane, it can be estimated how much rhombohedral YOF exists. That is, the reflection peak of the (111) plane of cubic YOF observed near 2θ = 28.8 ° is the strongest peak, and (006) of rhombohedral YOF observed near 2θ = 28.4 °. ) If the reflection peak intensity from the surface is 15 or less when the strongest peak intensity is 100, it can be said that cubic YOF is the main phase and is stabilized by Ca. The ratio of peak intensity here is measured as the ratio of peak height. Note that the YOF peak position and peak reflection surface index determined by the above X-ray diffraction measurement are based on the description of the ICDD card, and the same applies to LnOF other than Y.

The Ca-stabilized LnOF is preferably a solid solution formed by dissolving Ca in LnOF. For example, this solid solution is expressed by CaF ₂ when subjected to powder X-ray diffraction measurement using a sintered body containing LnOF in a scanning range of 2θ = 10 ° to 90 ° and a source of CuKα1 rays. This can be confirmed by the fact that no peak derived from fluoride is observed. The presence of Ca as an element can be confirmed by fluorescent X-ray analysis or the like. Or, polished surface a scanning electron microscope of the sintered body - can be confirmed by energy dispersive X-ray spectroscopy (SEM-EDS) were observed in the crystal grains Ca concentration is observed high (CaF ₂₎ is not present .

In the Ca-stabilized LnOF, the number of moles of Ca is preferably 1 mol or more and 40 mol or less with respect to 100 mol obtained by adding rare earth element (Ln) and Ca. By containing 1 mol or more of Ca, the phase transition from cubic or tetragonal to rhombohedral is more effectively suppressed, and LnOF is stabilized. On the other hand, when the number of moles of Ca with respect to the number of moles of rare earth element (Ln) is excessively high, the amount of fluoride represented by CaF ₂ that precipitates without dissolving in LnOF increases. Since CaF ₂ has a higher thermal expansion coefficient than LnOF, it may cause cracks in the sintered body. Therefore, in order to reduce the precipitation amount of CaF ₂ , the volume change of LnOF at the time of heating can be prevented by setting the number of moles of Ca with respect to the number of moles of 100 added with rare earth elements (Ln) and Ca is preferably 40 moles or less . From the viewpoint of further enhancing these effects, the ratio of the number of moles of Ca to the number of moles of 100 moles obtained by adding rare earth elements (Ln) and Ca is more preferably 1 mole or more and 35 moles or less, and more preferably 2 moles or more. It is particularly preferably 20 mol or less, and most preferably 3 mol or more and 10 mol or less. The number of moles of rare earth element (Ln) and the number of moles of Ca in LnOF are determined by quantitative analysis of Ca and Ln using analytical methods such as a fluorescent X-ray method, ICP-AES method, ICP-MS method, and atomic absorption method. It is possible to measure by performing.

  In this specification, the rare earth element (Ln) is selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. Is at least one element. In particular, as will be apparent from Examples described later, it is preferable to use yttrium (Y) as the rare earth element because it is possible to further improve the thermal shock resistance and conductivity while maintaining the corrosion resistance.

The sintered body of the present embodiment is represented by xLn ₂ O ₃ .yLnF ₃ (Ln represents a rare earth element. X and y are each independently a natural number of 1 and excluding LnOF), or From the viewpoint of obtaining high strength, it is preferable that an unstabilized LnOF subphase exists at the grain boundary of the crystal grains mainly composed of LnOF stabilized with Ca.

  More specifically, the sintered body of the present embodiment preferably has a main phase and a sub phase observed in its cross-sectional structure. Both the main phase and subphase are composed of rare earth oxyfluoride. In the present specification, the “main phase” is a phase that occupies a region of 50% or more in area ratio when the cross-sectional structure of the sintered body is observed. The “subphase” refers to a phase that occupies a region of less than 50% in area ratio when the cross-sectional structure of the sintered body is observed. The rare earth element in the rare earth oxyfluoride constituting the main phase and the rare earth element in the rare earth oxyfluoride constituting the subphase are not necessarily the same kind, but are preferably the same kind from the viewpoint of ease of production. .

  In the cross-sectional structure of the sintered body of the present embodiment, it is preferable that subphase crystal grains having an average grain size smaller than that of the main phase exist at the grain boundaries of the main phase crystal grains. That is, the subphase is in a state of being precipitated at the grain boundaries of the main phase crystal grains. In the present specification, the “crystal grain” is the maximum unit of a single crystal having the same crystal orientation. At the grain boundaries of the main phase crystal grains, the crystal orientation of the rare earth oxyfluoride is disturbed.

  The above description is about the main phase in the sintered body of the present embodiment, but the subphase in the sintered body of the present embodiment is not stabilized LnOF (Ln represents a rare earth element). It is preferable that it is comprised from these. Unstabilized LnOF (hereinafter also referred to as “unstabilized LnOF”) has a rhombohedral crystal structure. Unstabilized LnOF is a rare earth oxyfluoride having a rhombohedral crystal structure at room temperature (25 ° C.) and a cubic crystal structure at a high temperature exceeding 600 ° C. It is known that unstabilized LnOF exhibits a reversible phase transition between a cubic crystal which is a high-temperature stable phase and a rhombohedral crystal which is a low-temperature stable phase in a temperature range of 550 ° C. to 600 ° C. .

  As described above, the sintered body of the present embodiment has a special structure in which unstabilized subphase crystal grains exist at the grain boundaries between stabilized main phase crystal grains. Preferably it is. According to the sintered body of this embodiment having such a special structure, it is possible to increase the strength while maintaining the corrosion resistance due to the rare earth oxyfluoride.

In the sintered body of the present embodiment, the main phase is composed of xLn ₂ O ₃ .yLnF ₃ or Ca-stabilized LnOF, and the subphase is composed of non-stabilized LnOF. Can be confirmed by, for example, confirming the peak of the rare earth oxyfluoride of each crystal structure. Hereinafter, a case where the rare earth element is Y will be described as an example. The same applies to the case where the rare earth element is another element. Specifically, the inclusion of, for example, orthorhombic yttrium oxyfluoride (Y ₅ O ₄ F ₇ ) in the sintered body of the present embodiment indicates that 2θ = 10 ° to 90 ° by X-ray diffraction measurement. In the range, 2θ = 28.1 °, 32.3 °, and 46. Observed due to the (151), (010), and (202) planes of orthorhombic yttrium oxyfluoride, respectively. It is judged by the presence or absence of a peak at around 9 °.

  On the other hand, the inclusion of cubic yttrium oxyfluoride (YOF) means that (111) plane of cubic rare earth oxyfluoride (YOF) in the range of 2θ = 10 ° to 90 ° by X-ray diffraction measurement, Judgment is based on the presence or absence of peaks in the vicinity of 2θ = 28.8 °, 47.9 °, and 56.9 ° observed due to the (220) plane and the (311) plane, respectively.

  In addition, the inclusion of rhombohedral yttrium oxyfluoride (YOF) indicates that (009) of rhombohedral rare earth oxyfluoride (YOF) in the range of 2θ = 10 ° to 90 ° by X-ray diffraction measurement. Near 2θ = 43.1 °, 43.4 °, 47.4 °, and 47.9 ° observed due to the plane, (107) plane, (018) plane, and (110) plane, respectively. It is judged by the presence or absence of a peak.

On the other hand, the inclusion of orthorhombic europium oxyfluoride (Eu ₆ O ₅ F ₈ ) indicates that orthorhombic europium oxyfluoride is in the range of 2θ = 10 ° to 90 ° by X-ray diffraction measurement. Observed due to the (161) plane, (002) plane, (261) plane, and (0 12 2) plane, 2θ = 27.5 °, 31.7 °, 39.6 °, and 45. It is judged by the presence or absence of a peak around 6 °.
Further, the inclusion of rhombohedral europium oxyfluoride (EuOF) indicates that (012) of rhombohedral europium oxyfluoride (EuOF) in the range of 2θ = 10 ° to 90 ° by X-ray diffraction measurement. ), (018), (110), and (116) planes, respectively, observed near 2θ = 28.1 °, 46.2 °, 46.8 °, and 55.2 °. It is judged by the presence or absence of a peak.

  The X-ray diffraction measurement is performed at room temperature, specifically at 25 ° C. Unless otherwise specified in this specification, the X-ray diffraction measurement of the sintered body is a powder X-ray diffraction measurement. Specifically, the X-ray diffraction measurement can be performed by the method described in Examples described later.

In the sintered body of the present embodiment, when the main phase is xLn ₂ O ₃ .yLnF ₃ , it is a subphase with respect to the intensity of the x-ray diffraction peak of xLn ₂ O ₃ .yLnF ₃ , that is, the strongest peak intensity. The ratio of the intensity of the X-ray diffraction peaks of the (018) plane or (110) plane of unstabilized LnOF is preferably 0.5% or more and 30% or less, and more preferably 1% or more and 25% or less. Most preferably, it is 3% or more and 20% or less. When the ratio between the intensity of the X-ray diffraction peak of the main phase and the intensity of the X-ray diffraction peak of the subphase is within this range, it is possible to further increase the strength while maintaining the corrosion resistance due to the rare earth oxyfluoride. It becomes. Specifically, when the peak intensity ratio is 0.5% or more, the improvement of the intensity is sufficiently achieved. In addition, when the peak intensity ratio is 30% or less, the influence of the phase transition of LnOF, which is a sub-phase, is reduced, cracks are generated in the sintered body, and rapid dimensional changes are caused at high temperatures during use. It is effectively prevented from happening. In this case, it is only necessary that at least one of the intensities of the X-ray diffraction peak of the (018) plane or the (110) plane of the non-stabilized LnOF that is the subphase satisfies the intensity ratio.

When the main phase is, for example, Y ₅ O ₄ F ₇ , the strongest peak is observed at 2θ = 28.1 ° which is the (151) plane. When the main phase is, for example, La ₁₀ O ₇ F ₁₆ , the strongest peak is observed at 2θ = 26.5 ° which is the (001) plane. When the main phase is, for example, NdO _0.67 F _1.66 , the strongest peak is observed at 2θ = 27.1 ° which is the (001) plane. When the main phase is, for example, Eu ₆ O ₅ F ₈ , the strongest peak is observed at 2θ = 27.5 ° which is the (161) plane.

In addition, since the peak position (2θ) of the strongest peak of xLn ₂ O ₃ · yLnF _{3 and} the peak of the (006) plane of unstabilized LnOF are approximately the same, in the X-ray diffraction measurement, The peak of the (006) plane of unstabilized LnOF is superimposed on the peak of xLn ₂ O ₃ .yLnF ₃ , and it is not technically easy to separate the two. Therefore, the above-described peak intensity ratio is defined as the ratio of the peak intensity of the (018) plane or the (110) plane of the unstabilized LnOF when the superimposed peak intensity is 100.

  In the above description, “peak intensity” refers to the height of a diffraction peak observed by X-ray diffraction measurement by cps counting. In the following description, “peak intensity” is used in the same meaning.

  In the sintered body of the present embodiment, when the main phase is Ca-stabilized LnOF, the intensity of the X-ray diffraction peak on the (111) plane of Ca-stabilized LnOF, that is, the non-phase that is a subphase with respect to the strongest peak intensity. The intensity ratio of the X-ray diffraction peak of the (009) plane or (107) plane of the stabilized LnOF is preferably 0.5% or more and 10% or less, more preferably 1% or more and 9% or less, Most preferably, it is 2% or more and 8% or less. When the ratio between the intensity of the X-ray diffraction peak of the main phase and the intensity of the X-ray diffraction peak of the subphase is within this range, it is possible to further increase the strength while maintaining the corrosion resistance due to the rare earth oxyfluoride. It becomes. Specifically, when the peak intensity ratio is 0.5% or more, the improvement of the intensity is sufficiently achieved. Further, when the peak intensity ratio is 10% or less, the influence of the phase transition of LnOF, which is a secondary phase, is reduced, cracks are generated in the sintered body, and rapid dimensional changes at high temperatures during use. It is effectively prevented from happening. In this case, it is only necessary that at least one of the intensities of the X-ray diffraction peaks of the (009) plane or the (107) plane of the unstabilized LnOF that is the subphase satisfies the intensity ratio.

  In addition, since the peak of the (111) plane of Ca-stabilized LnOF and the peak of the (012) plane of non-stabilized LnOF are approximately the same (2θ), in the X-ray diffraction measurement, The peak of (111) plane of Ca-stabilized LnOF is superimposed on the peak of (012) plane of non-stabilized LnOF, and it is technically not easy to separate them. Therefore, the above-described peak intensity ratio is defined as the ratio of the peak intensity of the (009) plane or the (107) plane of the unstabilized LnOF when the superimposed peak intensity is 100.

  From the viewpoint of making the sintered body of this embodiment more dense, the sintered body preferably has a relative density (RD) of 70% or more, more preferably 80% or more, and 90%. More preferably, it is more preferably 95% or more. The higher the relative density, the better. The upper limit is 100%. A sintered body having such a high relative density can be obtained by adjusting temperature conditions, pressure conditions, and the like during firing when the sintered body of the present embodiment is manufactured. The relative density can be measured by Archimedes method based on JIS R1634. Specific measurement methods will be described in detail in Examples.

The sintered body of the present embodiment has enhanced conductivity while maintaining corrosion resistance due to the rare earth oxyfluoride. The volume resistivity of the sintered body is preferably 10 ¹⁰ Ω · cm or less from the viewpoint of use in applications requiring electrical conductivity. Although there is no problem if the conductivity is low, it is preferably 1 Ω · cm or more in view of plasma resistance and cost. From these points, the volume resistivity of the sintered body is more preferably 5 Ω · cm to 5 × 10 ⁹ Ω · cm, further preferably 10 Ω · cm to 3 × 10 ⁹ Ω · cm. The volume resistivity can be determined by the method described in Examples described later.

  The sintered body of the present embodiment has improved thermal shock resistance while maintaining corrosion resistance due to the rare earth oxyfluoride. The thermal shock fracture resistance coefficient R ′ of the sintered body is preferably 0.5 or more from the viewpoint of obtaining good thermal shock resistance. Further, the higher the thermal shock fracture resistance coefficient, the better. However, considering the cost, it is preferably 5 or less. From these points, the thermal shock fracture resistance coefficient R ′ of the sintered body is more preferably 0.6 or more and 4.5 or less, and further preferably 0.7 or more and 4 or less. The thermal shock fracture resistance coefficient R ′ can be obtained by the method described in Examples described later.

  The sintered body of the present embodiment preferably has high strength while maintaining corrosion resistance due to the rare earth oxyfluoride. Therefore, even if the sintered body of the present embodiment is subjected to precision processing such as cutting, for example, cracks and chips are hardly generated, and a product with high dimensional accuracy and small surface roughness can be easily manufactured. . Specifically, the sintered body of the present embodiment has a three-point bending strength of preferably 20 MPa or more and 300 MPa or less, more preferably 30 MPa or more and 200 MPa or less, and most preferably 50 MPa or more and 150 MPa or less. A method for measuring the three-point bending strength will be described in detail in Examples described later. When the three-point bending strength is 50 MPa or more, it is possible to perform highly accurate processing on the sintered body of the present embodiment. The three-point bending strength may exceed 300 MPa, but in that case, it cannot be produced unless an expensive raw material is used or a low-productivity sintering method such as HIP (Hot Isostatic Pressing) is used. From the viewpoint of industrial production, it is reasonable to set the upper limit to 300 MPa. The three-point bending strength can be measured by the method described in Examples described later.

  A sintered body having a volume resistivity, a thermal shock fracture resistance coefficient R ′, and a three-point bending strength within the above ranges can be obtained by the method described in Examples described later.

  Since the sintered body of the present embodiment is dense unlike the sprayed film, it is possible to make the halogen-based corrosive gas barrier property high. Since the sprayed film has a structure in which particles constituting the sprayed material are melted by thermal spraying, the halogen-based corrosive gas may flow into minute gaps between the melted particles. . Compared to this, the sintered body of the present embodiment is dense and has an excellent barrier property against halogen-based corrosive gas. For this reason, when the sintered compact of this embodiment is used for the structural member of a semiconductor device, for example, inflow of the halogen-type corrosive gas into this member can be suppressed, and it is excellent in the corrosion prevention effect. Examples of the member having a high halogen-based corrosive gas barrier property include a vacuum chamber constituent member of an etching apparatus, an etching gas supply port, a focus ring, and a wafer holder.

  The sintered body of the present embodiment may be substantially composed of only the rare earth oxyfluoride and the carbonaceous material, but may contain components other than the rare earth oxyfluoride and the carbonaceous material. That is, inevitable impurities may be included in addition to the oxyfluoride and the carbonaceous material. Specifically, the total amount of the rare earth oxyfluoride and the carbonaceous material in the sintered body is preferably 99 mass. % Or more. Such inevitable impurities include, for example, by-products such as yttrium oxide produced when manufactured by the method described below.

  The rare earth oxyfluoride content in the sintered body of the present embodiment is preferably 70% by mass or more from the viewpoint of further enhancing the plasma resistance effect of the present invention and improving the strength. From the viewpoint of further enhancing these effects, the amount of the rare earth oxyfluoride in the sintered body is more preferably 80% by mass or more, further preferably 85% by mass or more, and 90% by mass or more. Most preferred.

  In the sintered body of the present embodiment, examples of components other than the rare earth oxyfluoride include various sintering aids, binder resins, and carbon. In addition to the rare earth oxyfluoride, the sintered body of the present embodiment includes conventionally used aluminum oxide, yttrium oxide, aluminum yttrium composite oxide, yttrium fluoride, and other rare earth element-containing compounds other than yttrium. Various ceramic materials such as these may be contained.

A preferred method for producing the sintered body of the present invention will be described below.
This manufacturing method includes a step of treating a carbonaceous material with an oxidizing agent,
A step of preparing a slurry by dispersing a carbonaceous material after treatment with an oxidizing agent, and a rare earth element oxide and a rare earth element fluoride in a dispersion medium;
And baking the dried or granulated product of the slurry.

  First, the carbonaceous material is treated with an oxidizing agent. When a carbonaceous material is contained in a sintered body made of a ceramic material, it is usually necessary to prepare a slurry containing raw material powder of ceramic material, water, and a carbonaceous material. As a result of investigation by the present inventors, in the presence of rare earth fluoride powder, which is a raw material of a sintered body made of rare earth oxyfluoride, the carbonaceous material aggregates in the slurry, so that a dense sintered body cannot be obtained. I found out. Furthermore, when a slurry in which a carbonaceous material is dispersed in an organic solvent such as ethanol and a slurry in which a rare earth oxyfluoride is dispersed in water are separately prepared and mixed, the carbonaceous material aggregates and is densely sintered. I couldn't get a tie. As a result of further investigation, when a carbonaceous material is surface-treated with an oxidizing agent, a molded body and a sintered body in which carbon powder and / or carbon fibers are uniformly dispersed in a slurry are obtained even in the presence of rare earth fluoride powder. It turns out that it is obtained.

  Examples of the oxidizing agent include nitric acid, sulfuric acid, perchloric acid, chloric acid, hypochlorous acid, permanganate hydrogen peroxide, and salts thereof, and nitric acid is particularly preferable. By using nitric acid, various functional groups present on the surface of the carbonaceous material can be efficiently oxidized to improve hydrophilicity, and the dispersant acts effectively, and the raw material for the ceramic material in the slurry. There is an effect of uniformly dispersing the powder and the carbonaceous material.

  The treatment with the oxidizing agent is performed by bringing the solution containing the oxidizing agent into contact with the carbonaceous material. A contact method is not specifically limited, For example, the method of mixing an oxidizing agent solution and a carbonaceous material is mentioned. Examples of the solvent for the oxidant solution include water. As for the density | concentration of an oxidizing agent, 0.1M or more and 13M or less are mentioned, for example, and 1M or more and 10M or less are preferable. In the surface treatment, the oxidant solution is preferably heated. For example, the heating temperature is preferably 50 ° C. or higher and 110 ° C. or lower, more preferably 80 ° C. or higher and 105 ° C. or lower. The surface treatment time is, for example, preferably from 0.5 hours to 10 hours, and more preferably from 1 hour to 5 hours.

  The carbonaceous material after the treatment with the oxidizing agent is preferably used after being washed and dried. The drying temperature is preferably 50 ° C. or higher and 100 ° C. or lower.

Next, the surface-treated carbonaceous material obtained above, the rare earth oxide (Ln ₂ O ₃ ) powder, and the rare earth fluoride (LnF ₃ ) powder are mixed to form a slurry. The ratio of the carbonaceous material to the total amount of Ln ₂ O ₃ and LnF ₃ powder is preferably 100 masses in terms of the total amount described above, from the viewpoint of suitably obtaining a sintered body having both corrosion resistance, thermal shock resistance, and conductivity. The amount is preferably 0.05 parts by mass or more and 15 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less with respect to parts.

The mixing ratio of the rare earth oxide (Ln ₂ O ₃ ) and the rare earth fluoride (LnF ₃ ) powder varies depending on the crystal structure of the target rare earth oxyfluoride.
In particular, when manufacturing a sintered body in which Ln is Y, the main phase is Y ₅ O ₄ F ₇ and an unstabilized YOF subphase exists, the ratio described in the following (Method 1) To mix rare earth oxide (Y ₂ O ₃ ) and rare earth fluoride (YF ₃ ).
(Method 1)
In order to produce a rare earth oxyfluoride having a stoichiometric ratio of Y ₅ O ₄ F ₇ , these raw materials are mixed at a stoichiometric ratio of Y ₂ O ₃ : YF ₃ = 47: 53 (mass ratio). _Meanwhile, instead of the compound of the stoichiometric ratio of the Y ₅ O 4 _{F 7,} a Y ₅ O 4 _{F 7} and the main phase, if the unstabilized YOF intended to be a secondary phase, to become a high-strength, more preferably . In this case, it is necessary to add slightly more Y ₂ O ₃ (that is, add slightly less YF ₃ ) than the stoichiometric ratio of Y ₂ O ₃ : YF ₃ = 47: 53. From this viewpoint, the raw materials Y ₂ O ₃ and YF ₃ are represented by a mass ratio of Y ₂ O ₃ : YF ₃ , preferably 48: 52-60: 40, more preferably 49: 51-55: 45. , Most preferably in a ratio of 50:50 to 54:46. When Y ₂ O ₃ : YF ₃ is 48 or less: 52 or more, the strength is not sufficiently improved. In addition, when Y ₂ O ₃ : YF ₃ is 60 or more and 40 or less, the influence of phase transition of YOF which is a subphase is increased, and cracks are generated in the sintered body or at high temperature during use. This is not preferable because it causes a sudden dimensional change.

The explanation in the above method 1 is for the case where Ln (rare earth element) is Y, but the same can be considered when a rare earth element other than Y is used. That is, the mixing ratio of Ln ₂ O ₃ and LnF ₃ is xLn ₂ O ₃ .yLnF ₃ (Ln represents a rare earth element. X and y are each independently a natural number of 1 or more, and excludes LnOF) There than the ratio of the stoichiometric ratio to produce, it may be mixed with these powders as the Ln ₂ O ₃ increases.

The mixed powder in the case of producing a sintered body in which the main phase is Ca-stabilized LnOF and the sub-phase of unstabilized LnOF is present is as follows when Ln (rare earth element) is Y: The composition described in Method 2 is used. The same applies to the case where Ln is another element. In order to produce Ca-stabilized LnOF in the sintered body according to the following method 2, it is industrially advantageous to use calcium fluoride (CaF ₂ ) as a calcium source because it is inexpensive and stable in quality. For this reason, in Method 2, in addition to rare earth oxide (Ln ₂ O ₃ ) and rare earth fluoride (LnF ₃ ) as raw materials for producing the desired sintered body, calcium fluoride (CaF ₂ ) Is used.

(Method 2)
The ratio of the rare earth oxide, rare earth fluoride and calcium fluoride is preferably as follows. The amount of calcium fluoride is preferably 1% by mass or more and 10% by mass or less, and preferably 2% by mass or more and 9% by mass or less with respect to 100% by mass of the total mass of the rare earth oxide, rare earth fluoride and calcium fluoride. More preferably, it is more preferably 3% by mass or more and 8% by mass or less. What is necessary is just to set mass distribution of a rare earth oxide and rare earth fluoride so that it may become the molar ratio of LnOF with respect to the mass which subtracted the calcium fluoride mass from the whole mass. By using 1% by mass or more of calcium fluoride, it is possible to reduce the effect of the phase transition of the non-stabilized LnOF, which is a sub-phase, and cracks are generated in the sintered body. Can be effectively prevented. Moreover, the improvement effect of 3 point | piece bending strength becomes sufficient by using 10 mass% or less of calcium fluoride.

The carbonaceous material after the surface treatment, the rare earth oxide (Ln ₂ O ₃ ) powder, the rare earth fluoride (LnF ₃ ) powder obtained as described above, and the CaF ₂ powder as necessary, the dispersion medium and the necessity Depending on the case, a dispersant, a binder and the like can be added to form a slurry, which can be formed into a dry product or a granulated product, and then molded by a desired method. Water can be used as the slurry dispersion medium. Examples of the method for converting the slurry into a dried product or a granulated product include a spray drying method, a freeze drying method, and a rolling granulation method. Examples of a method for forming a dried product or a granulated product include a method of forming by a uniaxial hydraulic press method using a mold, an isostatic press method (CIP), a hot press method, a sheet forming method, an extrusion forming method, or the like. It is done. When subjected to a hydraulic press method, an isostatic press method (CIP), or a hot press method, the applied pressure is 10 MPa or more and 200 MPa or less, particularly 20 MPa or more and 150 MPa or less, and the heat conductivity and conductivity are in a desired range. It is preferable from the viewpoint of easily obtaining a sintered body. Further, the slurry can be directly formed by a casting method or the like.

  When a molded body is obtained in this manner, the molded body is then fired to obtain a sintered body. As firing conditions, the firing temperature is preferably 900 ° C. or more and 1500 ° C. or less from the viewpoint of obtaining a dense sintered body, more preferably 1000 ° C. or more and 1450 ° C. or less, and most preferably 1100 ° C. or more and 1400 ° C. or less. is there. By setting the firing temperature within this range, it is easy to obtain a sintered body having favorable thermal shock resistance, conductivity, and strength. The firing time is preferably 1 hour to 24 hours, more preferably 2 hours to 18 hours, and most preferably 3 hours to 14 hours, provided that the firing temperature is within this range. By setting the firing time to 1 hour or longer, the reaction sufficiently occurs and the main phase and the subphase are successfully formed. In addition, a sufficiently dense sintered body can be obtained. On the other hand, by setting the firing time to 24 hours or less, remarkable crystal growth is suppressed, and a decrease in strength can be suppressed.

  The firing atmosphere is preferably a vacuum from the viewpoint of densely producing a rare earth oxyfluoride having a target crystal structure. The degree of vacuum, expressed as an absolute pressure, is preferably 500 Pa or less, more preferably 200 Pa or less, and most preferably 100 Pa or less. In this way, the intended sintered body is obtained.

  The sintered body obtained in this manner can be used for constituent members of a semiconductor manufacturing apparatus such as a vacuum chamber of a dry etching apparatus and a sample table, chuck, focus ring, etching gas supply port in the chamber. Moreover, the sintered compact of this invention can be used for the use of the various structural members of a plasma processing apparatus and a chemical plant besides the structural member of a semiconductor manufacturing apparatus.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%” and “part” means “part by mass”.

[Example 1]
100 g of carbon powder was put into 1 liter of a 7M nitric acid aqueous solution and stirred at 100 ° C. for 1 hour with a hot stirrer to perform surface treatment. The treated carbon powder was thoroughly washed with pure water and dried at 60 ° C. The carbon powder used was spherical, and the cumulative volume particle size D50 at an integrated volume of 50% by volume by a laser diffraction / scattering particle size distribution measurement method was 6 μm. Y ₂ O ₃ powder, YF ₃ powder and the surface-treated carbon powder obtained above were mixed at a ratio of 48.5%, 50.5% and 1%, respectively. To 100 parts of the obtained mixture, 20 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. This slurry was granulated with a spray dryer. The obtained granule was put into a mold, and a compact was obtained by uniaxially pressing at a pressure of 100 MPa for 0.5 minutes using a hydraulic press. The obtained molded body was fired at 1400 ° C. for 4 hours in a vacuum to obtain a sintered body. A scanning electron microscope image of the sintered body obtained in Example 1 is shown in FIG. Further, the ratio of the variation of the carbonaceous ratio in the cross-sectional area in the sintered body to the average value was measured and found to be 8%. Moreover, when the ratio of the number of the carbonaceous material simple substance which is not in contact with the other simple substance in a sintered compact was measured by said method, it was 95% or more.

[Example 2]
Surface treatment, washing and drying were performed in the same manner as in Example 1 using 100 g of carbon powder. The carbon powder used was spherical, and the cumulative volume particle size D50 at an integrated volume of 50% by volume by a laser diffraction / scattering particle size distribution measurement method was 0.5 μm. The Y ₂ O ₃ powder, the YF ₃ powder, and the surface-treated carbon powder obtained above were respectively used for 45.9. %, 44.1% and 10%. To 100 parts of the obtained mixture, 50 parts of water, 3 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. A sintered body was obtained from the resulting slurry in the same manner as in Example 1.

Example 3
100 g of pitch-based carbon fibers having a diameter of 10 μm and a length of 50 μm were added to 1 liter of a 5M nitric acid aqueous solution, and the mixture was stirred with a hot stirrer at 100 ° C. for 3 hours for surface treatment. The treated carbon fiber was thoroughly washed with pure water and dried at 60 ° C. Y ₂ O ₃ powder, YF ₃ powder and the surface-treated carbon fiber obtained above were mixed at a ratio of 48.5%, 50.5% and 1%, respectively. To 100 parts of the obtained mixture, 20 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. This slurry was granulated with a spray dryer. The granules were put into a mold and uniaxially pressed at a pressure of 70 MPa for 3 minutes using a hydraulic press to obtain a molded body. The obtained molded body was fired at 1300 ° C. for 6 hours in a vacuum to obtain a sintered body. A scanning electron microscope image of the sintered body obtained in Example 3 is shown in FIG. Further, the ratio of the variation of the carbonaceous ratio in the cross-sectional area in the sintered body to the average value was measured and found to be 9%. Moreover, when the ratio of the number of the carbonaceous material simple substance which is not in contact with the other simple substance in a sintered compact was measured by said method, it was 85% or more.

Example 4
Using pitch-based carbon fibers having a diameter of 3 μm and a length of 40 μm, surface treatment, washing, and drying were performed in the same manner as in Example 3. Y ₂ O ₃ powder, YF ₃ powder and the surface-treated carbon fiber obtained above were mixed at a ratio of 48.5%, 46.5% and 5%, respectively. To 100 parts of the obtained mixture, 25 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. This slurry was granulated with a spray dryer. This granule was put into a carbon mold and fired at 1300 ° C. for 1 hour using a hot press while applying a pressure of 30 MPa in a vacuum to obtain a sintered body.

Example 5
Using pitch-based carbon fibers having a diameter of 10 μm and a length of 50 μm, surface treatment, washing, and drying were performed in the same manner as in Example 3. Y ₂ O ₃ powder, YF ₃ powder, CaF ₂ powder and the surface-treated carbon fiber obtained above were mixed at a ratio of 53.6%, 34.6%, 6.8% and 5%, respectively. To 100 parts of the obtained mixture, 25 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. This slurry was put into a plaster mold, cast and molded, and dried at 100 ° C. to obtain a molded body. The obtained molded body was fired at 1300 ° C. for 4 hours in a vacuum to obtain a sintered body.

Example 6
Using pitch-based carbon fibers having a diameter of 10 μm and a length of 50 μm, surface treatment, washing, and drying were performed in the same manner as in Example 3. Eu ₂ O ₃ powder, EuF ₃ powder and the surface-treated carbon fiber obtained above were mixed at a ratio of 55.4%, 43.6% and 1%, respectively. Other than that was carried out similarly to Example 3, and obtained the sintered compact.

[Comparative Example 1]
Y ₂ O ₃ powder and YF ₃ powder were mixed at a ratio of 51% and 49%, respectively. To 100 parts of the obtained mixture, 20 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a uniform aqueous slurry. This slurry was granulated with a spray dryer. The granules were put into a mold, and a compact was obtained by uniaxially pressurizing at a pressure of 100 MPa for 0.5 minutes using a hydraulic press. The obtained molded body was fired at 1400 ° C. for 4 hours in a vacuum to obtain a sintered body.

[Comparative Example 2]
Carbon powder having an average particle size (D50) of 10 μm was used, and Y ₂ O ₃ powder, YF ₃ powder, and the carbon powder were mixed at a ratio of 48.5%, 50.5%, and 1%, respectively. To 100 parts of the obtained mixture, 20 parts of water, 2 parts of a dispersant and 2 parts of a binder were added to obtain a slurry. Due to the aggregation of the carbon powder, unevenness was observed in the slurry. This slurry was granulated with a spray dryer. The granules were put into a mold, and a compact was obtained by uniaxially pressurizing at a pressure of 100 MPa for 0.5 minutes using a hydraulic press. The obtained molded body was fired in vacuum at 1400 ° C. for 4 hours. However, cracks and deformation occurred on the surface during sintering, and a sintered body could not be obtained.

[Measurement / Evaluation]
About the sintered compact obtained by the Example and the comparative example, the relative density was measured by the method described below. Further, the particle diameter of carbon particles or the diameter of carbon fibers was measured by the method described below. Further, the amount of carbon was measured by the method described below. Further, by the method described below, the main phase and the subphase were identified by X-ray diffraction measurement (hereinafter also referred to as XRD measurement), and the peak intensity ratio was measured. Further, volume resistivity and thermal shock fracture resistance coefficient R ′ were measured by the methods described below.

<Relative density>
Based on JIS R 1634: 1998, the bulk density was measured as follows. The sintered body is put into distilled water and held under reduced pressure by a diaphragm type vacuum pump for 1 hour, and then the weight in water W ₂ [g] is measured. Further, excess water is removed with a compress, and the saturated water weight W ₃ [g] is measured. Then, after sufficiently drying the dryer to put sintered body, measures the dry weight W _{1 [g].} The bulk density ρ _b [g / cm ³ ] is calculated by the following equation.
ρ _b = W ₁ / (W ₃ −W ₂ ) × ρ ₁ (g / cm ³ ) [g / cm ³ ]
In the formula, ρ ₁ [g / cm ³ ] is the density of distilled water. Using the obtained bulk density ρ _b and the theoretical density ρ _c [g / cm ³ ], the relative density (RD) [%] is calculated by the following equation.
RD = ρ _b / ρ _c × 100 [%]
Relative density was calculated.

<Carbon particle size>
The sintered body was mirror-polished and observed with a scanning electron microscope (SEM) to measure the particle size of the carbon particles. A plurality of images were taken at a magnification of 100 to 2000 times that is a magnification capable of measuring the crystal grain size of carbon. The crystal grain size of the carbon particles present in the photographed field of view was approximated by a circle, and the average value of 20 particles was taken as the average particle size.

<Diameter of carbon fiber>
The sintered body was mirror-polished and observed by SEM to measure the diameter and length of the carbon fiber. A plurality of images were taken at a magnification of 100 to 2000 times that is a magnification capable of measuring the diameter and length of carbon. The carbon fibers present in the photographed field of view were approximated by rectangles, the minor axis was the diameter, the major axis was the length, and the average value of 20 was taken as the mean diameter and mean length.

<Carbon amount>
When the carbonaceous material was carbon powder, the area ratio of the carbon particles was calculated from the average particle diameter and number of carbon particles and the area of the visual field. The area ratio was converted to a volume ratio to obtain the amount of carbon. When the carbonaceous material was carbon fiber, the area was calculated as a rectangle using the average diameter and average length, and the area ratio of the carbon fiber was calculated from the number and the area of the field of view. The area ratio was converted to a volume ratio to obtain the amount of carbon.

<XRD measurement>
Part of the sintered body was pulverized using a mortar and pestle to obtain a powder, and XRD measurement was performed on this powder. As a measuring instrument, apparatus name: MiniFlex600, manufacturer: Rigaku was used.
The measurement conditions were: target Cu, radiation source CuKα1 line, tube voltage 40 kV, tube current 15 mA, scanning speed 20 ° / min, scanning range 2θ = 3 ° to 90 °.
In Examples 1 to 4 where Ln is Y, the (151) plane of Y ₅ O ₄ F _{7 as} the main phase and the (006) plane of unstabilized YOF (rhombohedral crystal) as the subphase (both 2θ = When the peak intensity at which 28.2 [deg.] Overlaps is defined as 100, the (018) plane (110) plane (2 [theta] = 47.4 [deg.], 47.degree.) Of unstabilized YOF (rhombohedral crystal) as a subphase. The peak intensity ratio at around 9 ° was determined.
In Example 5 where Ln is Y, the (111) plane of Ca—YOF as the main phase and the (012) plane (2θ = 28.8 °, 28) of the unstabilized YOF (rhombohedral crystal) as the subphase. .About.7 °) where the overlapping peak intensity is 100, the (009) plane or (107) plane (2θ = 43.1 °, 43.4) of unstabilized YOF (rhombohedral crystal) as a subphase. The peak intensity ratio in the vicinity of ° was determined.
In Example 6 where Ln is Eu, the (161) face of Eu ₆ O ₅ F _{8 as} the main phase and the (006) face (2θ = 27.27) of the unstabilized EuOF (rhombohedral crystal) as the subphase. (0 °) or (110) plane (2θ = 46.2 °) of non-stabilized EuOF (rhombohedral crystal) as a sub-phase when the peak intensity at which 5 °, 27.7 °) overlap is 100 The peak intensity ratio at around 46.8 ° was determined.

<Volume resistivity>
The volume resistivity (Ωcm) was measured at room temperature (27 ° C.) and in the atmosphere by a direct current three-terminal method based on JIS C 2141: 1992 using a digital microammeter manufactured by ADC. The volume resistivity (Ωcm) was obtained by conversion from the current value at an applied voltage of 500 V and a holding time of 60 seconds. The sintered body used was processed into φ25 mm × 2 mm.

<3-point bending strength>
By cutting the sintered body and mirror polishing one side, a strip-shaped test piece having a thickness of 3.0 mm, a width of about 4 mm, and a length of about 35 mm is produced. This is placed on a SiC jig and a three-point bending test is performed with a universal material testing machine (1185 type, manufactured by INSTRON). The conditions are a distance between fulcrums of 30 mm, a crosshead speed of 0.5 mm / min, and the number of test pieces is 5. Based on JIS R1601: 2008, the bending strength σ _f [MPa] is calculated using the following formula.
σ _f = (3 × P _f × L) / (2 × w × t ² ) [MPa]
In the formula, _Pf is a load [N] when the test piece is broken, L is a span distance [mm], w is a width [mm] of the test piece, and t is a thickness [mm] of the test piece.

<Coefficient of thermal expansion>
Measured based on JIS R 1618: 2002. Specifically, it was as follows.
A sintered 5 mm × 5 mm × 20 mm test piece was set in a differential thermomechanical analysis (TMA) apparatus of TMA8310 manufactured by Rigaku Corporation. The temperature was raised from 25 ° C. to 1000 ° C. at a rate of 5 ° C./min in the air atmosphere. The load was 5 mN. As a reference, alumina having the same size as the test piece was set in a thermomechanical analysis (TMA) apparatus, and the temperature was similarly raised, and the dimensional difference ΔLa between the alumina and the test piece was measured. As the reference elongation ΔLb during this period, the thermal expansion coefficient was calculated by the following equation.
Thermal expansion coefficient (/ K) = (ΔLa + ΔLb) / (L × Δt) (where L = length of test piece before test, Δt = temperature difference measured for elongation)

<Thermal conductivity>
The sintered body φ12.7 mm × 2 mm test piece was measured by the laser flash method based on JIS R1611: 2010.

<Static modulus>
Specifically, based on JIS R1602: 1995, it was as follows.
The measurement uses an oscilloscope (WJ312A, manufactured by LECROY) and a pulsar receiver (5072PR, manufactured by Olympus NDT). Longitudinal wave vibrator (V110, 5 MHz) and transverse wave vibrator (V156, 5 MHz) are used for the test piece. )), And the longitudinal wave velocity V _l [m / s] and the transverse wave velocity V _t [m / s] are measured from the propagation velocity of the pulse. From the obtained V _l and V _t and the bulk density ρ _b [kg / mm ³ ] of the test piece, the elastic modulus E [GPa] is calculated using the following equation.
_{E = ρ b · (V t} 2 · V l 2 - 4V t 4) / (V l 2 - V t 2) × 10 -9 (GPa)

<Thermal shock fracture resistance coefficient R '>
From each measured value, R ′ was calculated by the following formula. The Poisson's ratio was considered constant for each sample and was excluded from the calculation formula.
R ′ = ((3-point bending strength MPa) × (thermal conductivity W / mK)) / ((static elastic modulus GPa) × (thermal expansion coefficient 10 ⁶ / K))

The larger the value of the thermal shock fracture resistance coefficient R ′, the better the thermal shock resistance. As is clear from the results shown in Table 1, the sintered bodies obtained in each Example have a thermal shock fracture resistance coefficient R ′ of 0.7 or more and a volume resistivity of 3 × 10 ⁹ Ωcm or less, which is excellent. It had high thermal shock resistance and conductivity. On the other hand, Comparative Example 1 containing no carbonaceous material had a thermal shock fracture resistance coefficient R ′ of 0.2 and a volume resistivity of 3 × 10 ¹⁵ and was inferior in thermal shock resistance and conductivity. . Further, in Comparative Example 2, cracks and deformation occurred in appearance during sintering, and a sintered body could not be obtained.

Claims (12)

  A sintered body containing a rare earth element oxyfluoride and a carbonaceous material.   The sintered body according to claim 1, wherein the carbonaceous material is carbon powder and / or carbon fiber.   The sintered body according to claim 1 or 2, wherein the carbonaceous material is in the form of particles having an average particle size of 0.1 µm to 10 µm.   The sintered body according to claim 1 or 2, wherein the carbonaceous material has a fibrous shape with a diameter of 1 µm to 20 µm and a length of 30 µm to 500 µm.   The sintered body according to any one of claims 1 to 4, wherein an amount of the carbonaceous material is 0.1 vol% or more and 30 vol% or less. The sintered body according to any one of claims 1 to 5, having a volume resistivity of 1 Ω · cm to 10 ¹⁰ Ω · cm.   The sintered body according to any one of claims 1 to 6, wherein the oxyfluoride of the rare earth element is represented by LnOF (Ln represents a rare earth element).   The sintered body according to claim 7, wherein the rare earth element oxyfluoride is Ca-stabilized LnOF. The rare earth element oxyfluoride is represented by xLn ₂ O ₃ .yLnF ₃ (Ln represents a rare earth element. X and y are each independently a natural number of 1 or more and excludes LnOF). Item 7. The sintered body according to any one of Items 1 to 6.   The sintered body according to any one of claims 1 to 9, wherein the rare earth element is Y. Rare earth element oxyfluoride is stabilized with xLn ₂ O ₃ .yLnF ₃ (Ln represents a rare earth element. X and y are each independently a natural number of 1 and excluding LnOF) or Ca 11. The sintered body according to claim 1, wherein an unstabilized subphase of LnOF exists at a grain boundary of a crystal grain having LnOF as a main phase. It is a manufacturing method of the sintered compact according to claim 1,
Treating the carbonaceous material with an oxidizing agent;
A step of preparing a slurry by dispersing a carbonaceous material after treatment with an oxidizing agent, and a rare earth element oxide and a rare earth element fluoride in a dispersion medium;
A method for producing a sintered body comprising a step of firing a dried or granulated product of the slurry.