JP6415480B2 - Sintered body - Google Patents

Description

  The present invention relates to a sintered body containing an yttrium oxyfluoride.

  Conventionally, as a material used for a window part of a chamber portion of a semiconductor manufacturing apparatus such as an etching apparatus using a halogen plasma or an optical system in a chamber, an aluminum-containing compound is used as a material having both corrosion resistance and translucency with respect to the halogen plasma. Has been used. For example, Non-Patent Document 1 describes that sapphire is mounted on window materials of various semiconductor manufacturing apparatuses such as an etching apparatus, an ashing apparatus, and a diffusion furnace. Further, translucent alumina as described in Patent Document 1 is also used for the above-mentioned use.

  On the other hand, yttrium oxyfluoride has recently been used as a corrosion-resistant material used in semiconductor manufacturing equipment. Patent Document 2 describes a sintered body obtained by sintering yttrium oxyfluoride alone, and Patent Document 3 describes a thermal spray material containing yttrium oxyfluoride.

WO2015 / 102065 pamphlet JP 2000-239067 A JP 2014-009361 A

Shinkosha Co., Ltd., “Sapphire Yorozu Takumi Kobo”, [online], [Search June 7, 2016], Internet <URL: http: // shinkosha. com / scube / use. html>

However, aluminum-containing compounds such as aluminum oxide described in Patent Literature 1 and Non-Patent Literature 1 are concerned about aluminum contamination of semiconductor silicon. From this viewpoint, a light-transmitting material replacing an aluminum-containing compound is required as an optical material or window material used in a semiconductor manufacturing apparatus.
In this regard, yttrium oxyfluoride has higher fluorine plasma resistance than yttrium oxide and has higher chemical stability and corrosion resistance than yttrium fluoride. Recently, it has been used as a constituent material of semiconductor manufacturing equipment. However, until now, no translucent material using yttrium oxyfluoride (YOF) has been known.

  Therefore, the subject of this invention is providing the sintered compact which can eliminate the various fault which the prior art mentioned above has.

The present invention is a sintered body containing a cubic yttrium oxyfluoride,
In the cubic yttrium oxyfluoride, calcium is contained in a ratio of 12.5 mol or more with respect to 100 mol of yttrium mol contained in the sintered body,
And the sintered compact whose relative density is 96% or more is provided.

The present invention is a method for producing the sintered body,
As a first method, a powder of oxyfluorides of yttrium average particle diameter _{D 50} is 5μm or less than 0.02 [mu] m, an average particle diameter _{D 50} of the powder of the calcium compound is 0.05μm or more 10μm or less, yttrium Obtaining a mixture of raw material powders containing a ratio of 13.5 mol or more of calcium in the calcium compound powder to 100 mol of yttrium contained in the oxyfluoride powder;
A step of obtaining the sintered body by sintering the mixture at a temperature of 1300 ° C. to 1500 ° C. under a pressure of 5 MPa to 100 MPa in a vacuum of 10 Pa or less. A method is provided.

The present invention is a method for producing the sintered body,
As a second method, a powder of oxyfluorides of yttrium average particle diameter _{D 50} is 5μm or less than 0.02 [mu] m, an average particle diameter _{D 50} of the powder of the calcium compound is 0.05μm or more 10μm or less, yttrium Obtaining a mixture of raw material powders containing a ratio of 13.5 mol or more of calcium in the calcium compound powder to 100 mol of yttrium contained in the oxyfluoride powder;
Including pressure-molding the mixture to obtain a molded body,
A step of obtaining the sintered body by sintering the molded body at a temperature of 1300 ° C. or more and 1500 ° C. or less under a pressure of 5 MPa or more and 100 MPa or less in a vacuum of 10 Pa or less. A manufacturing method is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the sintered compact which contains the oxyfluoride of yttrium and has translucency can be provided.

2 is a chart showing the results of powder X-ray diffraction measurement of the sintered body obtained in Example 1. FIG. 3 is an image used for measurement of the average crystal grain size of the sintered body obtained in Example 1. FIG. 3 is a graph of refractive index-wavelength measured for the sintered body of Example 1.

The present invention will be described below based on preferred embodiments with reference to the drawings.
The sintered body of the present invention is characterized by containing yttrium oxyfluoride. This yttrium oxyfluoride is a compound composed of yttrium (Y), oxygen (O), and fluorine (F). As a yttrium oxyfluoride in the present invention, from the viewpoint of easily obtaining a translucent effect more reliably,
Formula YO _x F _3-2x
In the formula, a compound in which X is 0.8 <x ≦ 1 is preferably used. Those having X = 1 in the above composition formula are particularly preferable. Yttrium oxyfluoride having a Y: O: F molar ratio of 1: 1: 1 is also described as YOF.

  The inventors of the present invention have intensively studied a configuration for imparting translucency to yttrium oxyfluoride. As a result, when a sintered body containing cubic yttrium oxyfluoride has a specific high density instead of the conventional rhombohedral yttrium oxyfluoride, it is surprising that It has been found that it can have light properties.

  Yttrium oxyfluoride represented by YOF usually has a rhombohedral crystal structure at room temperature, a cubic crystal structure at a high temperature exceeding 600 ° C., and a cubic crystal that is a high-temperature stable phase at 550 ° C. to 600 ° C. It is known that a reversible phase transition is exhibited between a rhombohedral crystal and a low temperature stable phase. Therefore, in general, the crystal structure of yttrium oxyfluoride at room temperature is rhombohedral. The rhombohedral crystal has optical anisotropy and therefore does not show translucency.

  On the other hand, the sintered body of the present invention contains cubic yttrium oxyfluoride in yttrium oxyfluoride. The fact that the sintered body of the present invention contains cubic yttrium oxyfluoride means that it contains cubic yttrium oxyfluoride at room temperature, specifically at 25 ° C. The present inventors speculate that this is one of the reasons why the sintered body of the present invention has translucency. In order to contain the cubic yttrium oxyfluoride in the sintered body of the present invention, as described later, a method of containing calcium in the yttrium oxyfluoride can be mentioned.

  The fact that the sintered body of the present invention contains cubic yttrium oxyfluoride means that the sintered body is subjected to powder X-ray diffraction measurement, and the peak of cubic yttrium oxyfluoride is observed by X-ray diffraction measurement. Can be confirmed. For example, the inclusion of cubic yttrium oxyfluoride indicates that the (111) plane, (220) plane, and (311) plane of cubic yttrium oxyfluoride are in the range of 2θ = 10 to 170 ° by X-ray diffraction measurement. Judgment is made based on the presence or absence of peaks in the vicinity of 2θ = 29 ° to 28 °, 48 ° to 47 °, and 57 ° to 56 °, which are respectively observed. If all the peaks in these three ranges are observed, it is determined that the sintered body of the present invention contains yttrium oxyfluoride which is cubic. Among them, 2θ = 28.81 ° to 28.50 °, 47.94 ° to 47.43 ° observed due to the (111) plane, (220) plane, and (311) plane of cubic YOF, respectively. , 56.90 ° to 56.27 ° are all observed, it is determined that the sintered body of the present invention contains cubic YOF. This X-ray diffraction measurement is performed at room temperature, specifically at 25 ° C. Unless otherwise specified in the present specification, the X-ray diffraction measurement of the sintered body is a powder X-ray diffraction measurement, and the CuKα1 line is used as a radiation source. Specifically, the X-ray diffraction measurement can be performed by the method described in Examples described later.

  Another feature of the sintered body of the present invention is that a specific amount of calcium is contained in cubic yttrium oxyfluoride. As a result, the sintered body of the present invention can have an yttrium oxyfluoride contained in the sintered body exclusively having a cubic structure, and can have good translucency.

  Specifically, as described above, in order to enable good translucency, the sintered body of the present invention contains calcium atoms in cubic yttrium oxyfluoride, and moles of yttrium atoms contained in the sintered body. It is necessary to contain at a ratio of 12.5 mol or more with respect to several hundred mol. Moreover, it is preferable that the sintered compact of this invention contains calcium in the ratio of 25 mol or less with respect to 100 mol of said yttrium moles from a viewpoint of suppressing scattering of transmitted light. From these viewpoints, the content of calcium in the sintered body of the present invention is preferably 13.5 mol or more and 25 mol or less, and 14 mol or more with respect to 100 mol of yttrium contained in the sintered body. More preferably, it is 20 mol or less.

  The number of moles of yttrium (Y) and the number of moles of Ca in the sintered body can be measured by calculating the molar concentration from the results of quantitative analysis of Ca and Y by EDS (energy dispersive X-ray spectroscopy). In the present invention, if the number of moles of Ca with respect to the number of moles of yttrium (Y) in the sintered body determined by EDS or the like is equal to or greater than the specific amount, the cubic yttrium oxyfluoride has a specific amount or more. Judged to contain calcium. EDS or the like is intended to include a measurement method that will be developed in the future as long as the method has a precision equal to or higher than that of EDS with respect to the measurement of the molar ratio of Ca / Y in the sintered body.

  As a form in which calcium is contained in the yttrium oxyfluoride of the present invention, in order that the sintered body of the present invention obtains particularly good translucency, it is preferable that calcium is dissolved in the yttrium oxyfluoride. . The presence of this solid solution is, for example, on the condition that the element Ca is present in the sintered body, the scanning range is 2θ = 10 ° to 170 °, and the sintered body is used for powder X-ray diffraction measurement by the above-mentioned radiation source. Can be confirmed by not observing the peak derived from the compound serving as the Ca source. However, it goes without saying that the present invention allows the peak derived from the compound serving as the Ca source to be observed in the sintered body in the powder X-ray diffraction measurement. The presence of the element Ca in the sintered body can be confirmed by EDS or the like. In the case where a halide is used as a Ca source, as described later, the sintered body of the present invention may be one in which the presence of halogen such as fluorine is confirmed by EDS or the like.

The compound serving as the Ca source here is preferably a compound containing calcium and halogen from the viewpoint of obtaining better translucency, for example, halides such as CaF ₂ , CaCl ₂ , CaBr ₂ , and CaI _2. Is mentioned. Among these, from the viewpoint of obtaining good translucency, a compound containing calcium and fluorine is preferable, and CaF ₂ is particularly preferable. These can be used alone or in combination of two or more.

The sintered body of the present invention is further characterized in that the relative density is 96% or more. As described above, the sintered body of the present invention not only simply contains cubic yttrium oxyfluoride, but also has such a high relative density that it has translucency. From this viewpoint, the relative density of the sintered body is preferably 96% or more, more preferably 99% or more, and particularly preferably 99.1% or more. The higher the relative density of the sintered body is, the better. However, to increase the density, it is necessary to increase the pressure during firing or to fire for a long time. For this reason, it is preferable to set it as 99.5% or less from the surface of manufacturing cost. In order to set the relative density of the sintered body within the above range, in the method for producing a sintered body, which will be described later, the particle size of the raw material powder is adjusted and the sintering step is performed while pressing. The relative density of the present invention is not the ratio of the bulk density to the apparent density measured by the Archimedes method, but the theoretical density of cubic yttrium oxyfluoride and the Ca source, as will be apparent from the examples described later. It is the ratio of the bulk density to the theoretical density of the sintered body calculated from the theoretical density of the compound. Therefore, the relative density of the present invention tends to be lower in numerical value than the ratio of the bulk density to the apparent density measured by the Archimedes method. For example, the theoretical density of the cubic YOF is 5.23 g / cm ^3, the theoretical density of CaF ₂ is 3.18 g / cm ^3.

  The sintered body of the present invention may be composed of only cubic yttrium oxyfluoride and calcium and / or a calcium source contained in the yttrium oxyfluoride. However, the sintered body of the present invention may contain impurities other than these. For example, the sintered body of the present invention may contain other light-transmitting substances such as yttrium oxide, yttrium fluoride, alumina, spinel, and magnesia. Moreover, even if it is a substance which does not have translucency, it is permitted to contain in the range of the small content which does not impair the translucency effect of this invention. For example, the sintered body is observed due to the (111) plane of cubic yttrium oxyfluoride when subjected to X-ray diffraction measurement with a scanning range of 2θ = 10 ° to 170 °. The ratio of the integrated intensity of the X-ray diffraction peak caused by the substance other than the cubic yttrium oxyfluoride and the compound containing calcium and fluorine is 0.20 or less Preferably there is. The impurities here include yttrium oxyfluorides other than cubic crystals, for example, rhombohedral yttrium oxyfluorides.

The fact that the intensity of the X-ray diffraction peak derived from the impurities is in the above-mentioned level means that the sintered body has impurities other than the material that becomes the oxyfluoride and calcium source of cubic yttrium, particularly a material that does not have translucency. Even if it is contained, the amount of the impurity is preferable because it is considered to be sufficiently small to prevent the influence on the light transmitting property more reliably. Note that “other than calcium and fluorine-containing compounds such as CaF ₂ ” means that such a compound, even if it exists in a range exceeding the upper limit of the peak ratio as compared with other impurities, is yttrium. This is because the oxyfluoride has little effect on the translucency.

  From the viewpoint of more reliably increasing the translucency of the sintered body of the present invention, the integrated intensity ratio is particularly preferably 0.15 or less.

  The sintered body of the present invention preferably has a low content of iron, cobalt and nickel from the viewpoint of more reliably increasing the translucency of the sintered body of the present invention. From these viewpoints, the sintered body of the present invention preferably has an iron, cobalt, and nickel content of 500 ppm or less, and more preferably 450 ppm or less. In addition to the iron, cobalt, and nickel, the sintered body of the present invention contains as little as possible the first transition metal element that is scandium, titanium, vanadium, chromium, manganese, copper, and zinc. It is preferable from the viewpoint of more reliably increasing the translucency of the bonded body. From these viewpoints, the content of each of these elements in the sintered body of the present invention is preferably 500 ppm or less, and more preferably 400 ppm or less. From the viewpoint of further enhancing the translucency of the sintered body, the first transition metal element and the second transition metal element other than yttrium (zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium) And third transition metal elements (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hahinium, tantalum, tungsten, rhenium, osnium, iridium, platinum , Gold, mercury), that is, the content of each transition metal element other than yttrium is preferably 500 ppm or less, and more preferably 450 ppm or less. In particular, in the sintered body of the present invention, the total amount of transition metal elements other than yttrium is preferably 1000 ppm or less, more preferably 500 ppm or less, and more preferably 350 ppm or less. The smaller the content of these elements, the better. The content of these elements in the sintered body can be measured by an analytical method such as a fluorescent X-ray method, an ICP-AES method, an ICP-MS method, or an atomic absorption method. In order to set the amount of the transition metal element to this amount, contamination derived from equipment used for manufacturing the sintered body may be reduced by a known method.

  Further, the content of carbon in the sintered body is preferably 1.0% by mass or less with respect to the sintered body from the viewpoint of not reducing the translucent effect of the present invention. The carbon content in the sintered body is preferably 0.3% by mass or less, and more preferably 0.2% by mass or less. The carbon content in the sintered body can be measured by carbon analysis by a combustion method. In order to set the amount of carbon to this amount, the amount of the organic binder used for the production of the sintered body may be reduced as much as possible, and it is more preferable not to use the organic binder.

  Further, the sintered body of the present invention preferably has a diffuse transmittance of 10% or more at d-line (wavelength 587.56 nm), more preferably 12% or more, and more preferably 20% or more. Preferably, it is 30% or more. As a preferable upper limit of the diffuse transmittance, about 70% can be mentioned in consideration of the balance with the manufacturing cost by further improving the diffuse transmittance. The diffuse transmittance of d-line is generally used as a reference in a visible light lens. The diffuse transmittance of d-line is measured by the method described in Examples described later. Examples of a method for setting the diffuse transmittance of d-line to be equal to or higher than the lower limit include a method of adjusting the purity and relative density of the sintered body.

When the sintered body of the present invention is used as a translucent member such as a lens or a viewing window, nF and nC are set to have refractive indexes of F-line (wavelength 486.13 nm) and C-line (wavelength 656.27 nm), respectively. When the refractive index nd at the d-line is in the range of 1.65 <nd <1.69,
In addition, it is preferable that the Abbe number νd calculated by the formula νd = (nd−1) / (nF−nC) is in the range of 25 <νd <60. nd and νd are measured by the method described in Examples described later. Examples of a method for obtaining a sintered body having a refractive index nd and an Abbe number νd within this range include adjusting the amount of the calcium compound in a preferable production method of the present invention described later.

  The sintered body of the present invention is usually a polycrystal, and the average crystal grain size is preferably 0.1 μm or more from the viewpoint of enhancing translucency, more preferably 20 μm or more, and 50 μm or more. More preferably it is. The average crystal grain size is preferably 500 μm or less from the viewpoint of easy production of the sintered body. The average crystal grain size can be measured by the method described in Examples described later. A sintered body having an average crystal grain size within this range can be obtained by adjusting the firing temperature during production of the sintered body.

  The sintered body of the present invention preferably has an open porosity of 0.2% or less from the viewpoint of translucency. In order to make the open porosity not more than the above upper limit, the pressure condition at the time of pressure firing and the particle size of the raw material powder in the preferable method for producing a sintered body described later may be adjusted. The open porosity can be measured by the method described in Examples described later.

Then, the suitable manufacturing method of the sintered compact of this invention is demonstrated.
This manufacturing method includes a powder of a first powder of oxyfluorides of yttrium average particle diameter _{D 50} is 5μm or less than 0.02μm as a method, the calcium compound is the mean particle diameter _{D 50} is 0.05μm or more 10μm or less And a step of obtaining a mixture of raw material powders in a ratio that the number of moles of calcium in the powder of the calcium compound is 13.5 moles or more with respect to the number of moles of yttrium contained in the yttrium oxyfluoride powder,
And obtaining the sintered body by sintering the mixture at a temperature of 1300 ° C. to 1500 ° C. under a pressure of 5 MPa to 100 MPa in a vacuum of 10 Pa or less.

Further, the method, as the second method, a powder of oxyfluorides of yttrium average particle diameter _{D 50} is 5μm or less than 0.02 [mu] m, calcium average particle diameter _{D 50} is 0.05μm or more 10μm or less A raw material powder mixture containing the compound powder at a ratio of 13.5 mol or more of calcium in the calcium compound powder to 100 mol of yttrium contained in the yttrium oxyfluoride powder is obtained. Process,
Including pressure-molding the mixture to obtain a molded body,
And obtaining the sintered body by sintering the molded body at a temperature of 1300 ° C. or higher and 1500 ° C. or lower under a pressure of 5 MPa or higher and 100 MPa or lower in a vacuum of 10 Pa or lower.

  The composition of the yttrium oxyfluoride powder in the raw material powder preferably has a molar ratio similar to the Y: O: F molar ratio of the yttrium oxyfluoride contained in the sintered body. From the point of availability, rhombohedral YOF powder can be mentioned, but even if rhombohedral YOF powder is used as a raw material in this manufacturing method, it is mixed with calcium compound powder and fired to form cubic yttrium. A sintered body containing the oxyfluoride is obtained. Further, not only rhombohedral YOF powder but also yttrium oxide, yttrium fluoride, and yttrium oxyfluoride are mixed as appropriate so that the molar ratio is Y: O: F = 1: 1: 1. Is obtained.

In this manufacturing method, by the powder average particle size D ₅₀ of yttrium oxyfluorides is 5μm or less, is reliably obtain a light-transmitting property in the fully dense sintered body. From this viewpoint, the average particle diameter D ₅₀ of the yttrium oxyfluoride powder is more preferably 3 μm or less, and particularly preferably 1 μm or less. The average particle diameter D ₅₀ of the yttrium oxyfluoride powder is preferably 0.02 μm or more, and more preferably 0.1 μm or more, from the viewpoint of ensuring mixing uniformity with the calcium compound powder.

  As an example and a preferable thing of a calcium compound, the example and preferable thing of the Ca source quoted in description of the said sintered compact can be mentioned.

In this manufacturing method, the average particle diameter D ₅₀ of the powder of the calcium compound is 10μm or less, is reliably obtain a light-transmitting property in the fully dense sintered body. More preferably the average particle diameter D ₅₀ of the powder aspects calcium compounds from is 8μm or less, particularly preferably 3μm or less. The average particle diameter D ₅₀ of the calcium compound powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and more preferably 1 μm from the viewpoint of ensuring uniformity of mixing with the yttrium oxyfluoride powder. It is still more preferable that it is above.

Measurement of Average particle diameter D ₅₀ of the powder of the powder and calcium compound oxyfluorides of yttrium is measured after performing the pre-treatment by sonication. The measurement can be performed by a laser diffraction / scattering particle size distribution measurement method, and specifically, can be measured by a method described later.

  The raw material powder is made of a mixture containing calcium compound powder and yttrium oxyfluoride powder. From the viewpoint of manufacturing a sintered body with high translucency, the amount of calcium in the powder of the calcium compound in the raw material powder is 13.5 mol or more and 14 mol or more with respect to 100 mol of yttrium in the yttrium oxyfluoride. It is more preferable that The number of moles relative to 100 moles of yttrium is more preferably 25 moles or less, and even more preferably 20 moles or less, from the viewpoint of suppressing dispersion of transmitted light. The molar ratio of Ca / Y in the sintered body is usually slightly smaller than the ratio of Ca to Y in the raw material powder due to the volatilization of Ca during production.

  The raw material powder may contain other components other than the calcium compound and yttrium oxyfluoride, but from the viewpoint of enhancing the plasma resistance and translucency of the sintered body, the calcium compound and yttrium in the raw material powder The total content of oxyfluoride is preferably 50% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more. The higher the proportion of the total content in the raw material powder, the better.

  As a method for obtaining a molded body of the mixture as the second method, for example, a die press method, a rubber press (hydrostatic pressure press) method, a sheet molding method, an extrusion molding method, a cast molding method, or the like can be used. For example, it is also preferable that the compact is pressure-sintered after being pressure-molded by uniaxial pressing with a hydraulic press or the like. In this case, the uniaxial pressure is preferably 1 MPa or more and 100 MPa or less, and more preferably 30 MPa or more and 70 MPa or less.

The obtained mixture or molded body is pressure fired under vacuum. The vacuum condition is 10 Pa or less, and more preferably 10 ⁻² Pa or less. The firing temperature is 1300 ° C. or higher and 1600 ° C. or lower. By setting the firing temperature to 1300 ° C. or higher, the driving force necessary for densification can be sufficiently provided. Further, by setting the firing temperature to 1600 ° C. or less, particularly 1500 ° C. or less, decomposition of yttrium oxyfluoride accompanying O and F desorption can be effectively suppressed. In this respect, the firing temperature is preferably 1350 ° C. or higher and 1500 ° C. or lower, and more preferably 1400 ° C. or higher and 1450 ° C. or lower. By performing the firing at a pressure of 5 MPa or more, it is easy to obtain a dense sintered body having high translucency. Further, by performing the pressure at 100 MPa or less, it is possible to suppress the wear of the dies used for firing. From this viewpoint, the firing pressure is preferably 30 MPa or more and 90 MPa or less, and more preferably 50 MPa or more and 70 MPa or less. The firing time at the above temperature is preferably from 1 hour to 6 hours, more preferably from 1.5 hours to 3 hours.

  By the above method, the sintered body of the present invention can be suitably obtained. The bulk sintered body obtained in this way makes use of its translucency and plasma corrosion resistance, a window material for visually confirming the inside of the vacuum chamber in the etching apparatus, a microscope installed in the chamber, etc. It can be suitably used as an optical system material that requires plasma resistance. Further, the sintered body can be used for various plasma processing apparatuses and window materials and engineering members in chemical plant components in addition to the components of semiconductor manufacturing apparatuses.

  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%”.

[Example 1]
YOF powder (rhombohedral crystal, average particle diameter D ₅₀ : 0.8 μm) and CaF ₂ powder (average particle diameter D ₅₀ : 2.5 μm) in an amount of 15 mol with respect to 100 moles of this YOF powder To obtain a mixture. This mixture was filled in a carbon die having an inner diameter of 40 mm and fired at 1400 ° C. for 3 hours while applying a pressure of 70 MPa to the mixture by a hot press method. Thereby, the sintered body of Example 1 was obtained. The average particle diameter is measured by the following method (the same applies hereinafter).
<Measurement method of average particle diameter _{D 50>}
A sample of 0.5 g was placed in a 50 mL glass beaker, and about 30 mL of ethanol was added. A beaker containing the sample and ethanol was set in an ultrasonic homogenizer (SUC-600A manufactured by Suzuki) and subjected to ultrasonic dispersion treatment for 1 minute to obtain a slurry. This slurry was dropped into a laser diffraction particle size measuring device (MT3300EXII manufactured by Nikkiso Co., Ltd.) until the device determined that the concentration was appropriate. In the measurement of D _50, using industrial water for the dispersion medium.

[Examples 2 to 5, Comparative Example 1]
The amount of CaF ₂ powder was changed to the amount shown in Table 1, or the firing temperature was changed to the temperature shown in Table 1. Except for this point, a sintered body was obtained in the same manner as in Example 1.

[Comparative Examples 2 to 5]
Change the amount of CaF ₂ powder to the amount shown in Table 1, or change the YOF powder to one whose average particle diameter D ₅₀ is that shown in Table 1, or / and the firing method or firing temperature as shown in Table 1. In the same manner as in Example 1, a sintered body was obtained. However, about the comparative example 2, what added 1.5% of polyvinyl alcohol with respect to the mixture as an organic binder was baked.
For Comparative Examples 2 and 4 to 5, the mixture obtained in the same manner as in Example 1 was fired after previously forming a molded body having a diameter of 25 mm and a thickness of 5 mm. A compact was produced using a hydraulic press for molding and uniaxially pressing at a pressure of 70 MPa for 1 minute.

<Evaluation of sintered body>
The relative density, crystal structure, molar ratio of Ca and Y, carbon content, diffusion transmittance, average crystal grain size, and transparency of the sintered bodies obtained in the examples and comparative examples were evaluated by the following methods. The results are shown in Table 1. For the sintered bodies of Examples 1 and 2, the amount of transition metal was determined by the following method, and the refractive index nd and Abbe number νd were determined for the sintered body of Example 1 by the following method. Further, the open porosity of the sintered bodies of Example 1 and Comparative Example 5 was determined by the following method.

(Relative density)
The relative density of the bulk density obtained by the Archimedes method of the sintered body of cubic theoretical density of YOF (5.23g / cm ³⁾ and theoretical density of CaF ₂ of (3.12g / cm ³⁾ mixture calculated from Obtained as a ratio to the theoretical density. Specifically, the bulk density was determined by the following formula using Archimedes method using pure water as a medium based on JIS R1634.
Bulk density (g / cm ³ ) = (M1 / (M3−M2)) × ρ where M1 is the dry mass (g) of the sintered body, M2 is the underwater mass (g) of the sintered body, and M3 is a sintered body. The saturated water mass (g) and ρ of the bonded body are the density (g / cm ³ ) of the medium during the test.

(Crystal structure of YOF)
The X-ray diffraction measurement of the sintered body was performed by the following method, and the crystal structure was specified by the above method. FIG. 1 shows a chart obtained by X-ray diffraction of the sintered body of Example 1. In each of the sintered bodies of Examples, peaks were observed in the range of 2θ = 28.81 ° to 28.50 °, 47.94 ° to 47.43 °, and 56.90 ° to 56.27 °, It contained cubic YOF. For the sintered body of Example 1, in the X-ray diffraction caused by substances other than cubic YOF and CaF _{2 with} respect to the integrated intensity of the peak caused by the (111) plane seen near 2θ = 28.5 °. When the ratio of the integrated intensity of the peaks was examined, it was 0.13. Further, when the ratio of the integrated strength was examined for the sintered body of Example 2, it was 0.11.
<XRD measurement method>
Part of the sintered body was pulverized using a mortar and pestle to obtain a powder, and XRD (MiniFlex 600 manufactured by Rigaku Corporation) was measured for this powder. The measurement conditions were: target Cu, source CuKα1 line, tube voltage 40 kV, tube current 15 mA, scanning speed 20 ° / min, scanning range 2θ = 10 ° to 170 °.

(Amount of Ca and Y)
The sintered body was polished with a diamond slurry having a particle size of 1 μm to produce a smooth surface. The prepared sample surface was measured with an EDS apparatus (JED-2300, manufactured by JEOL Ltd.) attached to the SEM apparatus (JEOL JSM6380A), and the amount of Ca and Y in the sintered body was quantitatively analyzed. The number of moles of was investigated. In the measurement, the operating distance was fixed to 10 mm, a tungsten filament was used as an electron beam source, and the acceleration voltage was 15 kV.

(Transition metal content)
Part of the sintered body was pulverized using a mortar and pestle to obtain a powder, and this powder was measured with a fluorescent X-ray analyzer (ZSX-Primus II, X-ray tube 4 kW manufactured by Rigaku Corporation). The total content of transition metals other than yttrium was quantitatively analyzed. The total content of transition metals other than yttrium obtained by the above method was 340 ppm in Example 1, and 190 ppm in Example 2.

(Carbon content)
Part of the sintered body was pulverized using an alumina mortar and pestle to obtain a powder. This powder was measured by a combustion method, and the amount of carbon in the sintered body was quantitatively analyzed. In the samples (Examples 1 to 5 and Comparative Examples 1 and 3 to 5) prepared without using an organic binder, the amount of carbon obtained by the above method was 0.2% or less. On the other hand, in the sample prepared by adding the organic binder (Comparative Example 2), it was 0.6%, and black coloring was observed.

(D-line diffuse transmittance)
A sintered body having a thickness of 1 mm was polished on both sides using a diamond slurry having a particle diameter of 1 μm. About the sintered compact after grinding | polishing, the diffuse transmittance of d line | wire was measured using the spectrophotometer (Hitachi U-4100).

(Refractive index nd and Abbe number νd)
After the cross section of the sintered body was polished with a 1 μm diamond slurry, measurement was performed in a range of 192 nm to 1687 nm at an incident angle of 70 ° using a spectroscopic ellipsometer (M-2000DI manufactured by JA Woollam). The refractive index of F line, d line, and C line was calculated. The refractive index-wavelength graph measured for the sintered body of Example 1 is shown in FIG. The sintered body of Example 1 had an nd of 1.67 and νd of 33.

(Open porosity)
The open porosity is based on JIS R1634, using pure water as a medium, and the open porosity (%) determined by the following formula by the Archimedes method = 100 × (M3-M1) / (M3-M2) where M1 Is the dry mass (g) of the sintered body, M2 is the mass in water (g) of the sintered body, and M3 is the saturated mass (g) of the sintered body. When the open porosity of the sintered body of Example 1 was measured, it was 0.17%, and when the open porosity of the sintered body of Comparative Example 5 was measured, it was 0.3%.

(Average crystal grain size)
After the cross section of the sintered body was polished, it was fired in the air at 1200 ° C. (keep time 20 minutes), and was thermally etched. Next, the etched surface was photographed with a scanning electron microscope (JSM6380A manufactured by JEOL Ltd.) and photographed under the conditions of a magnification of 500 times and an acceleration voltage of 15 kV to obtain an image. In the obtained image, a network-like crystal grain boundary and a crystal grain surrounded by it were observed. The image obtained in Example 1 is shown in FIG. In FIG. 2, the crystal grain boundaries are indicated by arrows. The cord length was measured by the intercept method, and the crystal grain size was calculated. Ten line segments were measured in one visual field, and this measurement was performed in 10 arbitrary different visual fields, and the average value of all crystal grain sizes observed for each visual field was used.

(transparency)
A sintered body molded to a thickness of 1 mm and φ15 mm was placed horizontally. A shading plate with black letters on a white background was installed immediately below it. The lower letters were seen through the sintered body from a position 15 cm above the sintered body, and the transparency, i.e., translucency, was visually evaluated according to the following evaluation criteria. The sintered body was irradiated with light having a brightness of about 5000 lumens from the upper position 200 cm away by a fluorescent lamp.
(Double-circle): The lower character can be seen through well.
○: The characters below are clearly visible.
Δ: The lower letters cannot be seen, but light passes through.
X: Light does not pass and there is no transparency.

From the description of Table 1, the sintered body of the present invention has good translucency by containing calcium in a cubic ratio of yttrium oxyfluoride at a specific ratio or more and setting the relative density to a specific value or more. It turns out that it has.

Claims (12)

A sintered body containing a cubic yttrium oxyfluoride,
In the cubic yttrium oxyfluoride, calcium is contained at a ratio of 12.5 moles or more with respect to 100 moles of yttrium moles contained in the sintered body,
And the sintered compact whose relative density is 96% or more.   The sintered body according to claim 1, wherein the cubic yttrium oxyfluoride is a compound represented by a composition formula YOF.   Diffraction observed due to the (111) plane of cubic yttrium oxyfluoride when the sintered body is subjected to X-ray diffraction measurement with a scanning range of 2θ = 10 ° to 170 °. The ratio of the integrated intensity of diffraction peaks caused by substances other than the compound containing cubic yttrium oxyfluoride and calcium and fluorine to the integrated intensity of the peak is 0.20 or less. The sintered body according to 1.   The sintered body according to any one of claims 1 to 3, wherein the total content of transition metal elements other than yttrium in the sintered body is 1000 ppm or less.   The sintered body according to any one of claims 1 to 4, wherein a content of carbon in the sintered body is 1.0 mass% or less with respect to the sintered body.   The sintered body according to any one of claims 1 to 5, wherein the diffuse transmittance at d line (wavelength: 587.56 nm) is 10% or more. When nF and nC are the refractive indexes of F line (wavelength 486.13 nm) and C line (wavelength 656.27 nm), respectively, the refractive index nd of d line is in the range of 1.65 <nd <1.69,
The sintered body according to any one of claims 1 to 6, wherein an Abbe number νd calculated by the formula νd = (nd-1) / (nF-nC) is in a range of 25 <νd <60.   The sintered body according to any one of claims 1 to 7, which is a polycrystalline body having an average crystal grain size of 0.1 µm or more and 500 µm or less.   The sintered body according to any one of claims 1 to 8, wherein the relative density is 99% or more.   The sintered body according to any one of claims 1 to 9, wherein the open porosity is 0.2% or less. It is a manufacturing method of the sintered compact according to claim 1,
An yttrium oxyfluoride powder having an average particle diameter D ₅₀ of 0.02 μm or more and 5 μm or less and a calcium compound powder having an average particle diameter D ₅₀ of 0.05 μm or more and 10 μm or less are used as an yttrium oxyfluoride powder. A step of obtaining a mixture of raw material powders contained in a proportion that the number of moles of calcium in the powder of the calcium compound is 13.5 moles or more with respect to 100 moles of yttrium contained;
A step of obtaining the sintered body by sintering the mixture at a temperature of 1300 ° C. to 1500 ° C. under a pressure of 5 MPa to 100 MPa in a vacuum of 10 Pa or less. Method. It is a manufacturing method of the sintered compact according to claim 1,
An yttrium oxyfluoride powder having an average particle diameter D ₅₀ of 0.02 μm or more and 5 μm or less and a calcium compound powder having an average particle diameter D ₅₀ of 0.05 μm or more and 10 μm or less are used as an yttrium oxyfluoride powder. A step of obtaining a mixture of raw material powders contained in a proportion that the number of moles of calcium in the powder of the calcium compound is 13.5 moles or more with respect to 100 moles of yttrium contained;
Including pressure-molding the mixture to obtain a molded body,
A step of obtaining the sintered body by sintering the molded body at a temperature of 1300 ° C. or more and 1500 ° C. or less under a pressure of 5 MPa or more and 100 MPa or less in a vacuum of 10 Pa or less. Production method.