Sintered body and method for manufacturing the same

Abstract

To provide at least one of a zirconia sintered body having high fracture toughness value measured by SEPB method and high mechanical strength, and a manufacturing method thereof.SOLUTION: A sintered body involves a zirconia containing a stabilizer and has a monoclinic crystal ratio of 0.5% or over and a three-point flexure strength of 1450 MPa or over in a JIS R 1601 three-point flexure testing.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a sintered body having zirconia as the main phase and a method for manufacturing the same. [Background technology]

[0002] In addition to conventional applications requiring strength, such as grinding media and structural materials, zirconia sintered bodies are being considered for decorative applications, such as decorative parts for watches, portable electronic devices, automobiles, and home appliances. Sintered bodies used for decorative purposes require reduced brittleness, that is, high fracture toughness.

[0003] Various zirconia sintered bodies have been reported to date for the purpose of improving fracture toughness. For example, Patent Document 1 reports a zirconia-alumina composite sintered body obtained by mixing commercially available 3 mol% yttria-containing zirconia powder, manufactured by neutralization coprecipitation, with commercially available alumina powder, and then microwave sintering the mixed powder. The fracture toughness value (K) of the composite sintered body measured by the IF method is... IC ) is 6.02~6.90 MPa·m 1 / 2 It is stated that this is the case.

[0004] Patent Document 2 reports a zirconia sintered body obtained by hot isostatic pressing (HIP) treatment of zirconia powder containing phosphorus, silicon dioxide, and alumina. The fracture toughness value of this sintered body, measured by the method specified in JIS R 1607, is 6 to 11 MPa·m. 1 / 2 It is stated that this is the case. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-226555 [Patent Document 2] Japanese Patent Application Publication No. 2011-178610 [Overview of the project] [Problems that the invention aims to solve]

[0006] When applying to decorative parts, it is also required to evaluate the brittleness of sintered bodies using highly reliable fracture toughness values. However, even for standardized fracture toughness measurement methods, multiple methods exist, and the values ​​obtained differ significantly depending on the measurement method. The fracture toughness value in Patent Document 1 is measured using a simple method, and the fracture toughness value in Patent Document 2 has an unclear measurement method; in both cases, the disclosed values ​​are unreliable.

[0007] This disclosure aims to provide at least one of the following: a zirconia sintered body having a high fracture toughness value measured by the SEPB method and high mechanical strength; a method for producing the same; and a zirconia sintered body having a higher fracture toughness value compared to conventional yttria-containing zirconia sintered bodies containing 2.0 mol% or less of yttria. [Means for solving the problem]

[0008] The present invention is as described in the claims, and the gist of this disclosure is as follows: [1] A sintered body characterized by containing zirconia containing a stabilizer, having a monoclinic content of 0.5% or more, and having a three-point bending strength exceeding 1450 MPa as determined by a three-point bending test in accordance with JIS R 1601. [2] The sintered body according to [1] above, wherein the total light transmittance for light at a wavelength of 600 nm at a sample thickness of 1.0 mm is 20% or more. [3] The sintered body according to [1] or [2] above, wherein the ratio of the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia is 0 or more. [4] The sintered body according to any one of [1] to [3] above, wherein the stabilizer is one or more selected from the group consisting of yttria, calcia, magnesia, and ceria. [5] The sintered body according to any one of [1] to [4] above, wherein the content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%. [6] The sintered body according to any one of [1] to [4] above, wherein the content of the stabilizer is 1.0 mol% or more and less than 1.9 mol%. [7] The fracture toughness value measured by the SEPB method specified in JIS R1607 is 6 MPa·m 0.5 More than 11MPa m 0.5 A sintered body according to any one of the above [1] to [6]. [8] A sintered body according to any one of [1] to [7] above, wherein the shift value of the tetragonal zirconia (113) plane is 0.15° or greater. [9] A sintered body according to any one of the above [1] to [8], comprising one or more additive components selected from the group consisting of alumina, germania, and silica.

[10] The sintered body according to any one of [1] to [9] above, wherein the additive component is alumina.

[11] The sintered body according to any one of [1] to

[10] above, wherein the zirconia comprises monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia.

[12] The sintered body according to any one of [1] to

[11] above, wherein the ratio of the tetragonal fraction after immersion in hot water at 140°C for 6 hours to the tetragonal fraction before immersion in hot water at 140°C for 6 hours is 15% or more.

[13] A method for producing a sintered body according to any one of [1] to

[12] above, characterized by the steps of: sintering a powder containing a stabilizer, containing zirconia with a monoclinic fraction of more than 70%, and having a crystallite diameter of monoclinic zirconia greater than 23 nm and less than or equal to 80 nm, to obtain a pre-sintered body with a relative density of 99% or less; and pressurizing the pre-sintered body.

[14] The manufacturing method according to

[13] above, wherein the pressurizing treatment is a hot isostatic press treatment.

[15] A component comprising the sintered body described in any one of the above [1] to

[12] . [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide at least one of a zirconia sintered body having a high fracture toughness value measured by the SEPB method and a high mechanical strength, a method for producing the same, and further, a zirconia sintered body having a higher fracture toughness value than a conventional yttria-containing zirconia sintered body containing 2.0 mol% or less of yttria.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, an example of an embodiment of the present disclosure will be described.

[0011] Each term in this embodiment is as follows.

[0012] The "monoclinic ratio" and the "tetragonal ratio" are the ratios of monoclinic zirconia and tetragonal zirconia, respectively, in the crystal phase of zirconia. The "monoclinic strength ratio" is the ratio of the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia in the crystal phase of zirconia.

[0013] For the powder, the powder X-ray diffraction (hereinafter also referred to as "XRD") pattern of the powder is used, while for the sintered body, the XRD pattern of the surface of the sintered body after mirror polishing (hereinafter also referred to as the "mirror sintered body") is used. The monoclinic ratio can be obtained from the following formula (1), the tetragonal ratio can be obtained from the following formula (2), and the monoclinic strength ratio can be obtained from the following formula (3), respectively. f m ={I m (111)+I m (11-1)} / [I m (111) +I​​​​​​​​​​​​​​​​​​t (111)+I c (111)] × 100 (2) M (11-1) / (111) ={I m (11-1) / I m (111)} (3)

[0014] In equations (1) to (3), f m This is the monoclinic fraction (%), f t This is the tetragonality (%), M (11-1) / (111) This is the monoclinic intensity ratio, I m (111) and I m (11-1) represents the area intensity of the XRD peaks corresponding to the (111) plane and (11-1) plane of monoclinic zirconia, respectively. t (111) represents the area intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia, and I c (111) represents the area intensity of the XRD peak corresponding to the (111) plane of cubic zirconia.

[0015] The following conditions can be listed as requirements for measuring XRD patterns. Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ = 26° ~ 33°

[0016] In the XRD pattern measurement described above, preferably, the XRD peaks corresponding to each crystal plane of zirconia are measured as peaks having a peak top at the following 2θ.

[0017] XRD peak corresponding to the (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° XRD peak corresponding to the (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° The XRD peaks corresponding to the (111) plane of tetragonal and cubic zirconia were measured overlappingly, and the 2θ of the peak top was 2θ = 30 ± 0.5°.

[0018] The area intensity of the XRD peaks on each crystal plane can be determined by using the "PRO-FIT" calculation program and separating each XRD peak using the method described in H. Toraya, J. Appl. Crystallogr., 19, 440-447 (1986).

[0019] Furthermore, the "mirror-finish sintered body" used for the XRD measurement described above is a sintered body with a surface roughness Ra of 0.04 μm or less, which is achieved by first grinding the surface after sintering using a surface grinding machine, followed by automatic polishing with abrasive cloth and paper, automatic polishing with a diamond slurry with an average particle size of 3 μm, and automatic polishing with colloidal silica of 0.03 μm.

[0020] "Cryslite size of monoclinic zirconia in powder" (hereinafter referred to as "D m It is also called "the crystallite size of tetragonal zirconia" (hereinafter referred to as "D t It is also called ). ) is a value obtained from the XRD pattern of the powder using the following equation (5). D m =κλ / (βcosθ m ) (4) D t =κλ / (βcosθ t ) (5)

[0021] In equations (4) and (5), D m This is the crystallite size (nm) of monoclinic zirconia, D t θ is the crystallite size (nm) of tetragonal zirconia, κ is the Scherrer constant (κ=1), λ is the wavelength (nm) of the light source used for XRD measurement, β is the full width at half maximum (°) after correcting for mechanical spreading using quartz sand (manufactured by Wako Pure Chemical Industries, Ltd.) with a grain size of 25-90 μm, and θ is the full width at half maximum (°). m θ represents the Black angle (°) of the reflection corresponding to the (11-1) plane of monoclinic zirconia in XRD measurements, and θ tλ is the Black angle (°) of the reflection corresponding to the (111) plane of tetragonal zirconia in XRD measurements. When CuKα radiation is used as the light source for XRD measurements, λ is 0.15418 nm.

[0022] The "BET specific surface area" is a value determined by the BET method at one point, in accordance with JIS R 1626-1996, with nitrogen (N2) as the adsorbent.

[0023] "Particle size based on volume distribution" refers to the particle size of a powder obtained by measuring the volume particle size distribution using laser diffraction. The particle size obtained by laser diffraction is a non-spherical approximate diameter. The following conditions are considered for volume particle size distribution measurement: Sample to be measured: Powder slurry Refractive index of zirconia: 2.17 Refractive index of solvent (water): 1.333 Measurement time: 30 seconds Pretreatment: Ultrasonic dispersion treatment

[0024] "Median diameter" refers to the particle diameter that corresponds to 50% of the volume of the cumulative volume particle size distribution curve obtained by volume particle size distribution measurement using laser diffraction.

[0025] A "particle size distribution curve" is a curve that shows the particle size distribution of a powder obtained by volume particle size distribution measurement using laser diffraction.

[0026] The "fracture toughness value" is the value of fracture toughness (MPa·m) measured by a method conforming to the SEPB method specified in JIS R 1607. 0.5) The fracture toughness value is measured using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements is taken as the fracture toughness value of the sintered body in this embodiment. Note that JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method. The IF method tends to produce larger values ​​than the SEPB method. Furthermore, because the IF method is a simple measurement method, there is a large variation in the measured values ​​from one measurement to the next. Therefore, the fracture toughness value in this embodiment and the fracture toughness value measured by the IF method cannot be compared in absolute terms. Similarly, the fracture toughness value measured by a method other than the SEPB method and the fracture toughness value measured by the SEPB method cannot be compared in absolute terms.

[0027] "Bending strength" refers to the three-point bending strength value obtained by a three-point bending test in accordance with JIS R 1601. The bending strength is measured using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements is used as the bending strength of the sintered body in this embodiment.

[0028] "Total light transmittance" refers to the total light transmittance for 600 nm wavelength light at a sample thickness of 1.0 mm, and can be measured by a method conforming to JIS K 7361. It can be determined by using 600 nm wavelength light as the incident light and summing the diffuse transmittance and linear transmittance for that incident light. A sample with a thickness of 1 mm and a surface roughness (Ra) ≤ 0.04 μm, preferably (Ra) ≤ 0.02 μm on both sides (measurement surface and opposite surface), is used as the measurement sample. Using a general spectrophotometer (e.g., V-650, manufactured by JASCO), 600 nm wavelength light is irradiated onto the sample, and the transmitted light is collected using an integrating sphere to measure the transmittance of the sample (diffuse transmittance and linear transmittance), which can then be taken as the total light transmittance. The following conditions are examples of measurement conditions for total light transmittance. Bandwidth: 5.0nm Data acquisition interval: 0.5nm Scanning speed: 1000 nm / min

[0029] "Relative density" is the ratio (%) of the measured density to the theoretical density. The measured density of a molded body is the ratio (g / cm³) of the volume obtained from dimensional measurements to the mass measured by mass measurement. 3 The measured density of the sintered body is the ratio of the volume measured by the Archimedes method to the mass measured by mass measurement (g / cm³). 3 The theoretical density is calculated from the following equations (6) to (9) (g / cm³). 3 ) A = 0.5080 + 0.06980X / (100 + X) (6) C = 0.5195 - 0.06180X / (100 + X) (7) ρ Z =[124.25(100-X)+225.81X] / [150.5(100+X)A 2 C] (8) ρ0 = 100 / [(Y A / 3.987)+(Y G / 3.637)+(Y S / 2.2) +(100-Y A -Y G -Y S ) / ρ Z ] (9)

[0030] In equations (6) to (9), ρ0 is the theoretical density, ρ Z is the theoretical density of zirconia, A and C are constants, X is the molar percentage (mol%) of the stabilizer (e.g., yttria (Y2O3)) relative to the total of zirconia (ZrO2) and the stabilizer (e.g., yttria (Y2O3)), and Y A , Y G and Y S This is the mass percentage (mass%) of alumina (calculated as Al2O3), germania (calculated as GeO2), and silica (calculated as SiO2) relative to the total amount of zirconia, stabilizer (e.g., yttria), alumina, germania, and silica in the molded or sintered body, calculated as ZrO2, the oxide-calculated stabilizer (e.g., Y2O3), Al2O3, GeO2, and SiO2, respectively.

[0031] The sintered body of this embodiment will be described below.

[0032] This embodiment is a sintered body characterized by containing zirconia containing a stabilizer and having a monoclinic content of 0.5% or more, and more particularly characterized by containing zirconia containing a stabilizer, having a monoclinic content of 0.5% or more, and having a three-point bending strength exceeding 1450 MPa as determined by a three-point bending test in accordance with JIS R 1601.

[0033] The sintered body of this embodiment is a sintered body containing zirconia containing a stabilizer, and is a sintered body whose main phase is zirconia containing a stabilizer, a so-called zirconia sintered body.

[0034] The stabilizer is a component that has the function of stabilizing zirconia, and includes one or more selected from the group consisting of calcia (CaO), magnesia (MgO), ceria (CeO2), and yttria (Y2O3). It is preferably at least one of ceria and yttria, and more preferably yttria. In the sintered body of this embodiment, the content of the stabilizer should be such that the zirconia is partially stabilized. As for the content of the stabilizer, for example, when the stabilizer is yttria, the molar ratio of yttria to the total of zirconia (ZrO2) and yttria (Y2O3) in the sintered body (={Y2O3 / (ZrO2+Y2O3)}×100 [mol%]; hereinafter also referred to as "yttria content") can be exemplified as 1.0 mol% or more and 2.5 mol% or less, more preferably 1.1 mol% or more and 2.2 mol% or less, and more preferably 1.1 mol% or more and 2.0 mol% or less, with a preference of 1.2 mol% or more and less than 2.0 mol%, and a preference of 1.2 mol% or more and 1.8 mol% or less. A stabilizer content within this range tends to result in a higher fracture toughness value measured by the SEPB method. The yttria content is preferably 1.4 mol% or more and 2.1 mol% or less, and more preferably 1.5 mol% or more and 1.8 mol% or less. Furthermore, the yttria content is 1.0 mol% or more, 1.3 mol% or more, or 1.6 mol% or more, and also 2.3 mol% or less, less than 1.9 mol%, 1.8 mol% or less, or 1.7 mol% or less.

[0035] It is preferable that the stabilizer is solid-dissolved in the zirconia, and it is preferable that the sintered body of this embodiment does not contain any unsolid-dissolved stabilizer, that is, that all of the stabilizer is solid-dissolved in the zirconia, and it is even more preferable that the XRD pattern of the sintered body of this embodiment does not have an XRD peak for the stabilizer. In this embodiment, if an XRD peak for the stabilizer can be confirmed as an XRD peak separate from the XRD peak for zirconia, it can be considered that the sintered body of this embodiment contains an unsolid-dissolved stabilizer to the extent that an XRD peak for the stabilizer cannot be confirmed. In other embodiments, the sintered body of this embodiment may contain an unsolid-dissolved stabilizer to the extent that an XRD peak for the stabilizer cannot be confirmed.

[0036] The sintered body of this embodiment may contain one or more additive components selected from the group consisting of alumina (Al2O3), germania (GeO2), and silica (SiO2). The additive component is preferably at least one of alumina and germania, and more preferably alumina. Including an additive component tends to increase the grain boundary strength between crystal grains even when the content of the zirconia stabilizer is low. When an additive component is included, the sintered body of this embodiment becomes a sintered body in which the additive component is included and the remainder is zirconia containing the stabilizer. The content of the additive component (hereinafter also referred to as "additive component content," and if the additive component is alumina, etc., it will also be referred to as "alumina content," etc.) is the mass ratio of the additive component to the total mass of the zirconia, stabilizer such as yttria, and additive component of the sintered body. For example, the alumina content in a sintered zirconia containing alumina as an additive and the remainder being yttria can be determined as {Al2O3 / (ZrO2+Y2O3+Al2O3)}×100 [mass%]). The additive content is preferably between 0.05 mass% and 30 mass%, more preferably between 0.1 mass% and 25 mass%, and more preferably between 0.2 mass% and 20 mass%. If the additive content is between 0.02 mass% and 0.3 mass%, there is a tendency for the mechanical strength to increase and for the transformation to monoclinic zirconia to be less likely to occur. Preferred additive content includes 0 mass% or more, greater than 0 mass%, 0.02 mass% or more, 0.1 mass% or more, or 0.3 mass% or more, and also between 25 mass% or less, 21 mass% or less, 11 mass% or less, 6 mass% or less, 2 mass% or less, or 1 mass% or less.

[0037] The sintered body of this embodiment preferably contains no impurities other than unavoidable impurities. Hafnia (HfO2) can be exemplified as an unavoidable impurity. In the calculation of composition-related values ​​such as theoretical density and the content of stabilizers and additives in this embodiment, the unavoidable impurity hafnia (HfO2) can be treated as zirconia (ZrO2) in the calculations.

[0038] The sintered body of this embodiment has a monoclinic content of 0.5% or more, preferably 0.5% to 15%, and more preferably 0.8% to 12%. Because fracture toughness tends to be higher, the monoclinic content is preferably 1% to 15%, 2% to 14%, 5% to 12%, or 7% to 11%. On the other hand, because bending strength tends to be higher, the monoclinic content is preferably 0.5% to 5%, and more preferably 0.8% to 3%.

[0039] The surface of a sintered body immediately after sintering (as-sintered-surface; hereinafter also referred to as the "as-sintered surface") is rough and contains many sources of fracture such as irregularities. An example of an as-sintered surface is a surface with Ra > 0.04 μm, and from another point of view, it is a surface without polishing marks. To prevent the sintered body from breaking, prior to evaluation and use in various applications, the as-sintered surface is removed by processing such as grinding and then polished. As a result, the sintered body is left with a mirror-like surface (polished-surface; hereinafter also referred to as the "mirror surface"). A mirror surface is a smooth surface, and an example of such a surface is one with Ra ≤ 0.04 μm. The monoclinic coefficient is the value on the mirror surface of the sintered body, that is, the value on the surface of the mirror-finished sintered body. In conventional sintered bodies with partially stabilized zirconia as the main phase, after mirror processing such as processing and polishing, the crystalline phase consists of at least one of tetragonal zirconia and cubic zirconia. Therefore, conventional mirror-finish sintered bodies contain virtually no monoclinic zirconia, or only a small amount of it. On the other hand, sintered bodies with poor mechanical properties may break during mirror finishing, making it impossible to process them into measurement samples, and in some cases, even impossible to measure the monoclinic content. In contrast, the sintered body of this embodiment can be processed into a mirror-finish sintered body, and moreover, the monoclinic content on its mirror surface can be measured. Furthermore, it has monoclinic zirconia on its mirror surface that satisfies the above-mentioned monoclinic content. Therefore, the sintered body of this embodiment is considered to be a sintered body having monoclinic zirconia throughout the entire sintered body, or a sintered body containing tetragonal zirconia that readily undergoes transformation into monoclinic zirconia, and is considered to be different from conventional sintered bodies that have monoclinic zirconia only on the processed surface.

[0040] In the sintered body of this embodiment, the zirconia comprises monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia, and preferably consists of monoclinic zirconia and tetragonal zirconia.

[0041] The monoclinic zirconia contained in the sintered body of this embodiment is monoclinic zirconia having an XRD peak in its XRD pattern that corresponds to at least the monoclinic zirconia (111) plane. Including such monoclinic zirconia in the state before degradation treatment makes the sintered body more likely to exhibit high fracture toughness. In addition, the sintered body tends to be less susceptible to hydrothermal degradation. When monoclinic zirconia is generated due to the degradation of the sintered body, the intensity of the XRD peak mainly corresponding to the monoclinic zirconia (11-1) plane in the XRD pattern becomes stronger. In contrast, the monoclinic zirconia contained in the sintered body of this embodiment preferably has an XRD peak in its XRD pattern that corresponds to at least the monoclinic zirconia (111) plane, and its monoclinic intensity ratio is preferably 0 or more, 0.3 or more, 0.4 or more, or 0.5 or more. The monoclinic intensity ratio is preferably 10 or less, 8 or less, 5 or less, 3 or less, or 1.5 or less, and is more preferably 1.2 or less, and even more preferably 1.0 or less. In this embodiment, the monoclinic intensity ratio can be determined from equation (3). Therefore, I m In sintered bodies where (111) is zero, that is, sintered bodies that do not have an XRD peak corresponding to the monoclinic zirconia (111) plane, the monoclinic intensity ratio becomes infinite, and it is not possible to determine a value. In other words, it is preferable that the sintered bodies of this embodiment do not contain sintered bodies with an infinite monoclinic intensity ratio.

[0042] The average grain size of the zirconia crystal grains in the sintered body of this embodiment varies depending on the sintering temperature, but can be any of the following: 0.1 μm or more and 0.8 μm or less, 0.15 μm or more and 0.60 μm or less, 0.20 μm or more and 0.55 μm or less, or 0.25 μm or more and 0.45 μm or less. In this embodiment, since the sintered body has particularly high bending strength, the average grain size can be any of the following: 0.40 μm or more or 0.50 μm or more, and also 0.65 μm or less or 0.60 μm or less.

[0043] The sintered body of this embodiment has a relative density (hereinafter also referred to as "sintered body density") of 98% or more and 100% or less, more specifically 98.4% or more and 100% or less, more specifically 99% or more and 100% or less, more specifically 99.5% or more and 100% or less, and more specifically 99.7% or more and 100% or less.

[0044] Furthermore, the sintered body of this embodiment is preferably a sintered body obtained by pressure sintering, and more preferably a sintered body obtained by hot hydrostatic pressing (hereinafter also referred to as "HIP") (a so-called HIP-treated body). The HIP-treated body may be a body that has been treated by another sintering method after pressure sintering, for example, atmospheric pressure sintering after pressure sintering, or a body that has been sintered in an oxidizing atmosphere after HIP treatment.

[0045] In this embodiment, the sintered body preferably has a shift value (hereinafter also simply referred to as "shift value") of tetragonal zirconia (113) planes of 0.15° or more, 0.3° or more, or 0.6° or more. Alternatively, the shift value may be 2.0° or less, 1.5° or less, or 1.0° or less.

[0046] The shift value is the difference in 2θ of the tetragonal zirconia (113) plane at tilt angles ψ=0° and ψ=45°, particularly the difference in 2θ of the tetragonal zirconia (113) plane at tilt angles ψ=0° and ψ=45° obtained by powder X-ray diffraction measurement using Crkα rays as the radiation source. In this embodiment, the following conditions can be used as conditions for powder X-ray diffraction measurement to determine the shift value. Radiation source: Crkα radiation (λ=2.29100nm) Acceleration voltage: 30kV Current: 30mA Measurement method: Parallel tilt method Collimator diameter: 4mm Measurement lattice plane: Tetragonal zirconia (113) plane Tilting angle ψ: 0° and 45°

[0047] Such powder X-ray diffraction measurements can be performed using common equipment (e.g., Auto MATE, manufactured by Rigaku Corporation).

[0048] In the above measurements, the peak corresponding to the tetragonal zirconia (113) plane is identified as a peak with its peak top at 2θ = 152 ± 2.0°. The shift value is the 2θ of the peak top corresponding to the tetragonal zirconia (113) plane at a tilt angle ψ = 0° (hereinafter referred to as "2θ"). (0°) It is also called ". ) and the peak top 2θ (hereinafter referred to as "2θ") corresponding to the tetragonal zirconia (113) plane at the tilt angle ψ=45°. (45°) It is also called ". ) and is a value obtained from the difference between the two. Shift value (°) = 2θ (45°) -2θ (0°)

[0049] It is believed that the crystalline state exhibiting such shift values ​​makes it easier for stress to occur between crystal grains compared to conventional sintered bodies. Therefore, it is conceivable that the sintered body of this embodiment has a higher fracture toughness value, and furthermore, in the case of a sintered body containing yttria as a stabilizer, for example, even with a low yttria content of 2.0 mol% or less, less than 1.9 mol%, 1.8 mol% or less, or 1.7 mol% or less, it is possible to obtain a sintered body that is less prone to defects and has a higher fracture toughness value.

[0050] The sintered body of this embodiment has a fracture toughness value (a fracture toughness value measured by a method conforming to the SEPB method specified in JIS R1607) of 6 MPa·m. 0.5 More than 11MPa m0.5 The following are examples, preferably 6.2 MPa·m 0.5 Above, the comfort level is 7 MPa·m. 0.5 More preferably 7.2 MPa·m 0.5 More preferably 8 MPa·m 0.5 The above is particularly preferably 8.5 MPa·m 0.5 That concludes the explanation. A high fracture toughness value is preferable, for example, 11 MPa·m. 0.5 Furthermore, 10.5 MPa·m 0.5 The following, and furthermore, 9.5 MPa·m 0.5 The following, and furthermore, 9 MPa·m 0.5 The following, and furthermore, 8.8 MPa·m 0.5 The following are some examples. Having such fracture toughness values ​​makes it easier to process the sintered body into a sintered body with a thickness of 1 mm or less, and even a sintered body with a thickness of 0.5 mm or less. As a result, the sintered body of this embodiment can be made into a sintered body with a thickness of 0.05 mm to 0.3 mm, and even a sintered body with a thickness of 0.08 mm to 0.25 mm.

[0051] The sintered body of this embodiment has a bending strength exceeding 1450 MPa, moreover 1455 MPa or higher, moreover exceeding 1550 MPa, and moreover 1580 MPa or higher. Preferred bending strengths include those exceeding 1450 MPa and 2300 MPa or lower, and moreover 1500 MPa or higher and 2200 MPa or lower, which is more preferable than 1550 MPa or higher and 2150 MPa or lower.

[0052] It has long been known that it is difficult to improve the fracture toughness of sintered bodies with high bending strength. For example, a sintered body with a bending strength of 1400 MPa or more has a fracture toughness of 7.0 MPa·m 0.5 It is less than or approximately. In contrast, the sintered body of this embodiment is a sintered body that has high mechanical strength while having improved fracture toughness compared to conventional sintered bodies. For this reason, a preferred sintered body of this embodiment has a bending strength exceeding 1450 MPa and 7.0 MPa·m 0.5 More than 7.5MPa m 0.5 Above or above 8.0 MPa·m 0.5The sintered body has the above-mentioned fracture toughness values. Furthermore, the upper limits of the bending strength and fracture toughness values ​​of such a sintered body may also be the same as those mentioned above.

[0053] Therefore, the sintered body of this embodiment contains zirconia containing a stabilizer, has a monoclinic content of 0.5% or more, a three-point bending strength of over 1450 MPa as determined by a three-point bending test in accordance with JIS R 1601, and a fracture toughness value of 7 MPa·m as measured by a method in accordance with the SEPB method specified in JIS R1607. 0.5 More than 11MPa m 0.5 Preferably, the sintered body is characterized by the following:

[0054] The sintered body of this embodiment has a bending strength of over 1450 MPa, 1455 MPa or more, 1490 MPa or more, or 1500 MPa or more, and also has a bending strength of 2300 MPa or less, 2200 MPa or less, 2150 MPa or less, 2100 MPa or less, 2000 MPa or less, or 1990 MPa or less, and a fracture toughness value of 6.0 MPa·m 0.5 More than 6.5MPa m 0.5 More than 7.0MPa m 0.5 Above or above 7.5 MPa·m 0.5 The above is true, and furthermore, 11 MPa·m 0.5 Below, 10.5MPa m 0.5 Below, 10MPa m 0.5 Below, 9.5MPa m 0.5 The following or 9.0 MPa·m 0.5 The following is preferable:

[0055] The sintered body of this embodiment preferably has a total light transmittance of 20% to 50%, more preferably 25% to 45%, and more preferably 30% to 40%. In particular, when the amount of additive components exceeds 0% by mass and is 25% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and more preferably 0.23% by mass or more and 3% by mass or less, the total light transmittance is 25% to 45%, and more preferably 35% to 40%.

[0056] It is preferable that the tetragonal zirconia contained in the sintered body of this embodiment is less susceptible to transformation to monoclinic zirconia due to hydrothermal treatment (hereinafter also referred to as "hydrothermal degradation"). In the sintered body of this embodiment, it is preferable that the ratio of the tetragonal content after immersion in 140°C hot water for 6 hours to the tetragonal content before immersion in 140°C hot water for 6 hours (hereinafter also referred to as "residual tetragonal content" or "△T%") is 15% or more, more preferably 70% or more, and even more preferably 80% or more. If the tetragonal zirconia does not transform to monoclinic zirconia due to immersion in 140°C hot water for 6 hours, the residual tetragonal content becomes 100%. Therefore, the residual tetragonal content of the sintered body of this embodiment is 100% or less, and more preferably 95% or less.

[0057] The higher the content of the additive component, the more likely it is that hydrothermal degradation will be suppressed. In the sintered body of this embodiment, if the content of the additive component is 0% by mass, i.e., if no additive component is present, the residual tetragonal structure can be exemplified as 15% to 100%, preferably 20% to 100%, and more preferably 50% to 80%. If the sintered body of this embodiment contains an additive component, and the content of the additive component exceeds 0% by mass and is less than 5% by mass, the residual tetragonal structure can be exemplified as 65% to 100%, preferably 70% to 90%. If the sintered body of this embodiment contains an additive component, and the content of the additive component is 5% to 30% by mass, the residual tetragonal structure can be exemplified as 70% to 100%, preferably 76% to 95%.

[0058] The shape of the sintered body in this embodiment can be any desired shape, including cubic, rectangular, polygonal, plate-shaped, disc-shaped, columnar, conical, spherical, substantially spherical, and other basic shapes, as well as shapes suitable for various applications.

[0059] The method for manufacturing the sintered body in this embodiment is arbitrary, but examples include a manufacturing method characterized by a step of sintering a powder containing a stabilizer, containing zirconia with a monoclinic content exceeding 70%, and having a monoclinic zirconia crystallite diameter exceeding 23 nm and 80 nm or less, to obtain a pre-sintered body with a relative density of 99% or less, and a pressure sintering step of pressurizing the pre-sintered body, and further a manufacturing method characterized by a pre-sintering step of pre-sintering a molded body of powder containing a stabilizer, containing zirconia with a monoclinic content exceeding 70%, and having a monoclinic zirconia crystallite diameter exceeding 23 nm and 80 nm or less, to obtain a pre-sintered body with a relative density of 99% or less, and a pressure sintering step of pressurizing the pre-sintered body. In addition, in the manufacturing method for the sintered body in this embodiment, calcination and processing may be applied to the molded body or the like before or after pre-sintering as needed.

[0060] The powder to be subjected to pre-sintering is preferably in a molded state, i.e., a molded body (powder compact). The molding can be carried out by known methods, for example, at least one selected from the group consisting of uniaxial press, cold isostatic press, slip casting, and injection molding, and it is preferable that at least one selected from the group consisting of uniaxial press, cold isostatic press, and injection molding is used. This yields a molded body, i.e., a powder compact in which powder particles are physically aggregated.

[0061] When processing a molded body prior to sintering, the molded body may be calcined as needed to obtain a calcined body. In this embodiment, the calcined body is composed of fused particles, which are zirconia particles that have formed neckings with each other. To obtain a calcined body composed of fused particles, calcination can be performed by heat-treating the powder, preferably the molded body, at a temperature below the sintering temperature. For example, heat treatment can be performed in an air atmosphere at 800°C to less than 1200°C, preferably 900°C to less than 1150°C, more preferably 900°C to 1100°C, and even more preferably 950°C to less than 1100°C. This yields a calcined body composed of fused particles. Prior to pre-sintering, the calcined body may be processed into any shape.

[0062] Sintering can be carried out using one or more known methods, such as pressure sintering, vacuum sintering, and atmospheric pressure sintering. For sintering powder, preferably molded bodies, atmospheric pressure sintering is preferred. On the other hand, for sintering pre-sintered bodies, pressure sintering is preferred, preferably at least one of hot pressing and HIP treatment, more preferably HIP treatment.

[0063] For pressure sintering, a pre-sintered body with a relative density of 99% or less, preferably 95% to 99%, and more preferably 97% to less than 99%, is provided. The pre-sintered body can be obtained by any firing method, but it is sufficient to sinter a molded body (or calcined body) at atmospheric pressure. Setting the relative density of the pre-sintered body within this range makes it easier to eliminate pores in the sintered body during pressure sintering. To achieve the relative density of the pre-sintered body within the above range, pre-sintering can be exemplified by atmospheric pressure sintering in an atmospheric atmosphere at 1100°C to 1400°C, preferably between 1100°C and 1400°C, and more preferably between 1150°C and 1400°C. In this embodiment, atmospheric pressure sintering is a method of sintering by heating without applying any external force to the material to be sintered during sintering.

[0064] Pressure sintering can be performed by treating the pre-sintered body with a processing pressure of 50 MPa or higher and a processing temperature of 1200°C or higher. Preferred pressure sintering methods include HIP treatment for 0.5 to 2 hours at a processing pressure of 50 MPa to 500 MPa and a processing temperature of 1200°C to 1550°C under either a reducing atmosphere or an inert atmosphere. A HIP-treated body is obtained by the HIP treatment. The above atmospheres include at least one of nitrogen and argon, and more preferably an argon atmosphere.

[0065] If necessary, pressurized bodies such as HIP-treated bodies may be heat-treated in an oxidizing atmosphere. Examples of heat treatment conditions include an air atmosphere, a temperature of 900°C to 1100°C, and a duration of 0.5 hours to 5 hours.

[0066] The sintered body of this embodiment may be a HIP-treated body, or a HIP-treated body after heat treatment in an oxidizing atmosphere.

[0067] The sintered body of this embodiment can be used as a component in applications known for zirconia sintered bodies. The sintered body of this embodiment is suitable for structural materials such as crusher components, precision machine parts, and optical connector components, biomaterials such as dental materials, decorative components, and exterior materials such as electronic equipment exterior components.

[0068] The powder for the sintered body of this embodiment will be described below.

[0069] The powder for the sintered body of this embodiment (hereinafter also referred to as "the powder of this embodiment") is a powder characterized by containing a stabilizer, containing zirconia with a monoclinic content exceeding 70%, and having a crystallite size of monoclinic zirconia that is greater than 23 nm and less than or equal to 80 nm.

[0070] The powder of this embodiment contains a stabilizer and includes zirconia with a monoclinic content exceeding 70%. That is, the powder of this embodiment contains stabilizer-containing zirconia, which is mainly composed of monoclinic zirconia. If the zirconia powder does not contain a stabilizer, even if it is sintered, it is difficult to obtain a sintered body containing tetragonal zirconia, which is a factor in exhibiting fracture toughness. The powder of this embodiment is a so-called zirconia powder, which is mainly composed of zirconia.

[0071] The stabilizer is one or more selected from the group consisting of calcia (CaO), magnesia (MgO), ceria (CeO2), and yttria (Y2O3), and is preferably at least one of ceria and yttria, and more preferably yttria. When the stabilizer is yttria, the molar ratio of yttria to the total of zirconia (ZrO2) and yttria (Y2O3) in the powder (yttria content) can be exemplified as 1.0 mol% or more and 2.5 mol%, more preferably 1.1 mol% or more and 2.0 mol%, preferably 1.2 mol% or more and less than 2.0 mol%, and more preferably 1.2 mol% or more and 1.8 mol%. In a powder characterized by containing yttria, containing zirconia with a monoclinic content exceeding 70%, and having a crystallite size of monoclinic zirconia exceeding 23 nm and being 80 nm or less, the yttria content is preferably 1.0 mol% or more, 1.1 mol% or more, 1.2 mol% or more and 1.4 mol% or more, and more preferably 2.0 mol% or less, less than 2.0 mol%, 1.8 mol% or less, or 1.7 mol% or less.

[0072] The stabilizer is preferably solid-dissolved in zirconia, the powder of this embodiment preferably does not contain unsolid-dissolved stabilizer, and more preferably the powder does not have an XRD peak of the stabilizer in its XRD pattern.

[0073] The main crystalline phases of zirconia are known to be monoclinic zirconia, tetragonal zirconia, and cubic zirconia. The zirconia in the powder of this embodiment includes monoclinic zirconia, preferably includes monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia, and more preferably includes monoclinic zirconia and tetragonal zirconia.

[0074] The monoclinic ratio of zirconia is preferably greater than 70%, more preferably 80% or higher, and more preferably 85% or higher. If the monoclinic ratio is 100% or less, and the zirconia contains at least one of tetragonal zirconia and cubic zirconia, the monoclinic ratio will be less than 100%. Furthermore, the tetragonal ratio is preferably 30% or less, even less than 20%, and less than 15%, and may be 10% or less, and even 7% or less. If the zirconia does not contain tetragonal zirconia, the tetragonal ratio will be 0%, and may be 0% or higher.

[0075] Crystallite size (D) of monoclinic zirconia m The crystallite size (D) of monoclinic zirconia is greater than 23 nm and less than or equal to 80 nm, more preferably between 30 nm and 60 nm, and even more preferably between 35 nm and 55 nm. In another embodiment, the crystallite size (D) of monoclinic zirconia is greater than or equal to 80 nm, more preferably between 30 nm and 60 nm, and even more preferably between 35 nm and 55 nm. m The wavelength may be between 30nm and 50nm, and more specifically between 35nm and 50nm, and may also be between 35nm and 45nm, and more specifically between 36nm and 40nm.

[0076] The powder of this embodiment may contain one or more additive components selected from the group consisting of alumina (Al2O3), germania (GeO2), and silica (SiO2). The additive component is preferably at least one of alumina and germania, and more preferably alumina. Including an additive component makes it less likely for defects such as cracking to occur during sintering, even when the content of the zirconia stabilizer is low, and the yield during sintering does not decrease. The content of the additive component is such that the mass ratio of the additive component to the total mass of the powder zirconia, stabilizer such as yttria, and additive component is 0.05% by mass or more and 30% by mass or less, preferably more than 0.1% by mass and 25% by mass or less, more preferably 0.2% by mass or more and 20% by mass or less, and even more preferably 0.23% by mass or more and 6% by mass or less.

[0077] The powder of this embodiment preferably contains no impurities. For example, the phosphorus (P) content can be exemplified as 0.1 mass% or less and less than 0.1 mass%, respectively. On the other hand, it may contain inevitable impurities such as hafnium (HfO2) in zirconia.

[0078] The powder of this embodiment has a BET specific surface area of 6 m 2 / g or more and less than 20 m 2 / g. When the BET specific surface area is 6 m 2 / g or more, sintering tends to proceed from a relatively low temperature. Also, when it is less than 20 m 2 / g, physical aggregation of the powder tends to be suppressed. Since these effects are more easily obtained, the BET specific surface area is preferably 8 m 2 / g or more and 18 m 2 / g or less, more preferably 10 m 2 / g or more and 17 m 2 / g or less, still more preferably 10 m 2 / g or more and 15 m 2 / g or less, even more preferably 10 m 2 / g exceeding 15 m 2 / g or less. On the other hand, since sintering in a lower temperature range is likely to be promoted, the BET specific surface area is 14 m 2 / g or more or 16 m 2 / g or more, and preferably 18 m 2 / g or less.

[0079] The powder of this embodiment preferably has a median diameter of 0.05 μm or more and 0.3 μm or less, and preferably 0.1 μm or more and 0.2 μm or less.

[0080] The powder of this embodiment can be exemplified by having a multimodal volume-particle-size distribution curve, and it is preferable that the volume-particle-size distribution curve has peaks at least between 0.05 μm and 0.2 μm and between 0.2 μm and 0.5 μm, and more preferably between 0.05 μm and 0.2 μm and between 0.3 μm and 0.5 μm. Powders with a multimodal volume-particle-size distribution curve, such as a bimodal distribution, tend to have high packing properties during molding. As the density of the resulting molded article tends to be high, the ratio of the peak for particle size 0.3 μm to 0.5 μm (hereinafter also referred to as the "particle-size peak ratio") to the peak for particle size 0.05 μm to 0.2 μm in the volume-particle-size distribution curve is preferably greater than 0 and less than 1, more preferably between 0.1 and 0.9, and even more preferably between 0.2 and 0.8.

[0081] The powder of this embodiment preferably has high moldability. When the powder of this embodiment is uniaxially pressed at a pressure of 70±5 MPa and then treated with a cold isostatic press (hereinafter also referred to as "CIP") at a pressure of 196±5 MPa to form a molded body, the relative density of the molded body (hereinafter also referred to as "molded body density") is preferably 49% or more and 56% or less, and more preferably 50% or more and 54% or less.

[0082] The powder of this embodiment may contain a resin or the like to improve fluidity, and may also be a composition containing the powder of this embodiment and a resin (hereinafter also referred to as "compound"). The resin contained in the compound may be any known resin used in ceramic compositions, for example, a thermoplastic resin. Preferred resins include one or more from the group consisting of acrylic resins, polystyrene, and polyalkyl carbonates, preferably acrylic resins.

[0083] Examples of powder content in a compound, expressed as the mass ratio of powder to the mass of the compound, include 50% to 97% by mass, 70% to 95% by mass, and 80% to 90% by mass. The powder content in the compound can be determined from the mass ratio of the compound after resin removal to the mass of the compound. The method of resin removal is arbitrary, but examples include using an air atmosphere or heat treatment at 200°C to 500°C.

[0084] The compound may contain additives other than resin, such as waxes. The inclusion of these additives provides additional benefits, such as improved release properties from the mold. Examples of waxes and other additives include one or more selected from the group consisting of polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, polyacetal resin, petroleum-based wax, synthetic wax, plant-based wax, stearic acid, phthalate ester plasticizers, and adipic acid esters.

[0085] The powder of this embodiment can be used as a precursor for calcined or sintered bodies, and is suitable as a raw material powder for structural materials such as crusher components, precision machine parts, and optical connector components, biomaterials such as dental materials, decorative components, and exterior materials such as electronic equipment exterior components.

[0086] When the powder of this embodiment is to be used to form a sintered body or the like, the powder can be formed and then calcined or sintered using a known method.

[0087] When the powder of this embodiment is used to form a molded body, the molding can be carried out by known methods, such as at least one selected from the group consisting of uniaxial pressing, cold isostatic pressing, slip casting, and injection molding. If a resin, such as a compound, is used to produce the molded body, the resulting molded body may be heat-treated to remove the resin as needed. Examples of heat treatment conditions include an air atmosphere and a temperature of 400°C to less than 800°C.

[0088] The molded body may be calcined if necessary. Calcination can be performed by heat treatment at a temperature below the sintering temperature of the powder, for example, in an air atmosphere, at a temperature of 800°C to less than 1200°C, preferably 900°C to less than 1150°C, more preferably 900°C to 1100°C, and even more preferably 950°C to less than 1100°C. This causes the powder particles to become fused particles with necking formed by initial sintering, and a calcined body is obtained.

[0089] Sintering can be carried out using one or more known methods selected from the group including pressure sintering, vacuum sintering, and atmospheric pressure sintering, and preferably includes at least pressure sintering. When pressure sintering is performed, the zirconia powder is molded, calcined as necessary, and pre-sintered in an air atmosphere at 1100°C to 1400°C, preferably between 1100°C and 1400°C, more preferably between 1150°C and 1400°C. The resulting pre-sintered body is then subjected to HIP treatment in an argon atmosphere at a processing temperature of 1200°C to 1550°C for 0.5 to 2 hours at a pressure of 50 MPa to 500 MPa. Generally, pressure sintering can forcibly remove closed pores in the sintered body. Therefore, sintering a sintered body obtained by atmospheric pressure sintering (atmospheric pressure sintered body) tends to densify it and improve the mechanical strength of the sintered body. However, even if an atmospheric pressure sintered body is subjected to pressure sintering, the fracture toughness value of the sintered body hardly changes. In contrast, by using the powder of this embodiment as a starting material and pressurizing it, preferably by HIP treatment, a result of 7.0 MPa·m 0.5 Furthermore, 7.0 MPa·m 0.5 It is also possible to obtain a highly tough sintered body that has an even higher fracture toughness value and also possesses a bending strength of 1400 MPa or higher, 1450 MPa or higher, or even greater than 1450 MPa.

[0090] Next, the method for producing the powder of this embodiment will be described.

[0091] The manufacturing method of the powder of this embodiment is arbitrary as long as it has the characteristics described above. A preferred manufacturing method of the powder of this embodiment includes the steps of: heat-treating a composition containing a zirconia sol containing monoclinic zirconia having an average sol particle size of 150 nm to 400 nm and a stabilizer source at 950°C to 1250°C to obtain a calcined powder; and grinding the calcined powder.

[0092] A calcined powder, which is a precursor to the powder of this embodiment, is obtained by a process in which a composition comprising a zirconia sol containing monoclinic zirconia with an average sol particle size of 150 nm to 400 nm and a stabilizer source is heat-treated at 950°C to 1250°C to obtain calcined powder (hereinafter also referred to as the "powder calcination process").

[0093] In the powder calcination process, heat treatment is performed at temperatures between 950°C and 1250°C, and further between 1000°C and 1250°C. Heat treatment at temperatures above 950°C yields powder that is easily densified by atmospheric pressure sintering. On the other hand, heat treatment at temperatures below 1250°C yields powder that is easily dispersed by grinding. The heat treatment time varies depending on the heat treatment temperature, but examples include 30 minutes to 2 hours.

[0094] The atmosphere for the heat treatment is arbitrary and can be selected from the group consisting of an oxidizing atmosphere, a reducing atmosphere, an inert atmosphere, and a vacuum atmosphere. An oxidizing atmosphere is preferred, and an atmospheric atmosphere is more preferred.

[0095] The zirconia sol has an average sol particle size of 150 nm to 400 nm, preferably 180 nm to 400 nm, and more preferably 185 nm to 300 nm. The average sol particle size may also be 150 nm to 270 nm, more preferably 150 nm to 200 nm, or 190 nm to 400 nm, or even more preferably 200 nm to 300 nm.

[0096] The zirconia sol preferably contains zirconia that includes monoclinic zirconia, and more preferably contains zirconia made of crystalline zirconia (hereinafter also referred to as "crystalline zirconia sol"), and more preferably contains crystalline zirconia in which the main phase is monoclinic zirconia.

[0097] Because it tends to be easily pulverized, the amount of zirconium element in the zirconia sol (hereinafter also referred to as "adsorbed zirconium amount"), which can be calculated using the following formula, is preferably 0% by mass or more and 1% by mass or less, more preferably 0% by mass or more and 0.5% by mass or less, and even more preferably 0% by mass or more and 0.01% by mass or less. W Zr = (m / m0) × 100

[0098] In the above formula, W Zr m represents the amount of adsorbed zirconium (mass%). m is the mass (mg) of zirconium in the filtrate, converted to zirconia (ZrO2), obtained by ultrafiltration of a slurry of zirconia sol dispersed in pure water using an ultrafiltration membrane with a molecular weight cutoff of 500 to 3 million. The amount of zirconium in the filtrate can be measured by ICP analysis. o This is the mass (mg) of the zirconia sol before ultrafiltration after heat treatment in an air atmosphere at 1000°C for 1 hour. o The measurements can be performed by preparing equal amounts of zirconia sol before ultrafiltration.

[0099] The zirconia sol subjected to the powder calcination process only needs to have the characteristics described above, and the method of its production is arbitrary. Examples of methods for producing zirconia sol include hydrothermal synthesis and hydrolysis. In the hydrothermal synthesis method, zirconia sol is obtained by heat-treating a coprecipitate obtained by mixing a zirconium salt with an alkali, etc., in the presence of a solvent at 100 to 200°C. In the hydrolysis method, zirconia sol is obtained by hydrolyzing a zirconium salt by heating it in the presence of a solvent. Thus, examples of zirconia sol include zirconia sol obtained by hydrothermal synthesis or hydrolysis, and zirconia sol obtained by hydrolysis is preferred.

[0100] Zirconium salts are used as precursors in the method for producing zirconia sol. Examples of zirconium salts include one or more selected from the group consisting of zirconium oxychloride, zirconyl nitrate, zirconium chloride, and zirconium sulfate, and it is preferable that at least one of zirconyl nitrate and zirconium oxychloride be used, with zirconium oxychloride being more preferable.

[0101] Below, we will explain a preferred method for producing zirconia sol, using hydrolysis as an example.

[0102] The hydrolysis conditions can be any conditions that allow the hydrolysis of the zirconium salt to proceed sufficiently. For example, this can be done by boiling an aqueous solution of zirconium salt under reflux for 130 to 200 hours. When hydrolysis is performed with an anion concentration in the aqueous solution of zirconium salt between 0.2 mol / L and 0.6 mol / L, and further between 0.3 mol / L and 0.6 mol / L, the average sol particle size tends to increase.

[0103] The stabilizer source may be at least one of the stabilizer and its precursor compounds. Examples include one or more selected from the group of oxides, hydroxides, oxyhydroxides, chlorides, acetates, nitrates, and sulfates that are precursors of stabilizers, and it is preferable that it is at least one of chloride and nitrate. The stabilizer source is preferably at least one of yttria and its precursor yttrium compounds. Preferred stabilizer sources (hereinafter, stabilizers including yttria, etc., are also referred to as "yttria sources," etc.) include one or more selected from the group of yttrium chloride, yttrium nitrate, and yttrium oxide, and further, at least one of yttrium chloride and yttrium oxide. When the stabilizer source is an yttria source, the yttria source content of the composition can be exemplified as 1.0 mol% to 2.5 mol%, more preferably 1.1 mol% to 2.0 mol%, with a molar ratio of the yttria source converted to Y2O3 relative to the sum of the zirconium (Zr) and yttrium (Y) content of the composition converted to ZrO2 and Y2O3, respectively. A more preferable ratio is 1.2 mol% to less than 2.0 mol%, and a more preferable ratio is 1.2 mol% to 1.8 mol%.

[0104] The composition used in the powder calcination process may contain the above-mentioned zirconia sol and stabilizer source, and all or part of the stabilizer source may be solid-dissolved in the zirconia sol.

[0105] For example, by mixing a zirconium salt with a stabilizing agent source and hydrolyzing it, or by mixing a zirconium salt, a stabilizing agent source, and an alkali, etc., to form a coprecipitate, at least a portion of the stabilizing agent source becomes more readily soluble in zirconia.

[0106] The composition subjected to the powder calcination process may contain one or more additive sources selected from the group consisting of alumina sources, germania sources, and silica sources. The additive source is preferably at least one of alumina sources and germania sources, and is preferably an alumina source.

[0107] The alumina source is at least one of alumina and aluminum compounds that are precursors thereof, and examples include one or more selected from the group consisting of alumina, aluminum hydroxide, aluminum nitrate, and aluminum chloride. It is preferably alumina, and more preferably at least one of alumina sol and alumina powder.

[0108] The germania source is at least one of germania and germanium compounds that are precursors thereof, and examples include one or more selected from the group of germania, germanium hydroxide, and germanium chloride, preferably germania, and more preferably at least one of germania sol and germania powder.

[0109] The silica source is at least one of silica and silicon compounds that are precursors thereof, and examples include one or more selected from the group of silica and tetraethyl orthosilicate. It is preferably silica, and more preferably at least one of silica powder, silica sol, fumed silica, and precipitated silica.

[0110] The content of the added component source is such that it is 0.05% by mass or more and 30% by mass or less, as a ratio of the total mass of Al, Ge, and Si converted to Al2O3, GeO2, and SiO2, respectively, to the total mass of Zr, Y, Al, Ge, and Si converted to ZrO2, Y2O3, Al2O3, GeO2, and SiO2, respectively. Preferably, it is more than 0.1% by mass and 25% by mass or less, and more preferably 0.2% by mass or more and 20% by mass or less.

[0111] For example, the alumina source content is such that it is 0.05% by mass or more and 30% by mass or less, as a ratio of the mass of the alumina source converted to Al2O3 to the total mass of Zr, Y, and Al in the composition converted to ZrO2, Y2O3, and Al2O3, respectively. Preferably, it is more than 0.1% by mass and 25% by mass or less, and more preferably 0.2% by mass or more and 20% by mass or less.

[0112] Furthermore, the germania source content is defined as the ratio of the mass of the germania source converted to GeO2 to the total mass of Zr, Y, and Ge in the composition converted to ZrO2, Y2O3, and GeO2, respectively, preferably between 0.05% and 30% by mass, more preferably between 0.1% and 25% by mass, and more preferably between 0.2% and 20% by mass.

[0113] Furthermore, the silica source content is such that it is 0.05% by mass or more and 30% by mass or less, as the ratio of the mass of the silica source converted to SiO2 to the total mass of Zr, Y, and Si in the composition converted to ZrO2, Y2O3, and SiO2, respectively, preferably more than 0.1% by mass and 25% by mass or less, and more preferably 0.2% by mass or more and 20% by mass or less.

[0114] The physical properties of the calcined powders are as follows: BET specific surface area is 3m². 2 / g or more 15m 2 Examples include being less than or equal to / g, and having a monoclinic crystallite size of 20 nm to 60 nm.

[0115] In the calcined powder crushing process (hereinafter also referred to as the "crushing process"), the calcined powder is crushed. Zirconia with a low stabilizer content is prone to cracking and chipping during sintering. In contrast, crushing the calcined powder in this embodiment tends to increase the yield during sintering, and furthermore, the resulting sintered body tends to be less susceptible to hydrothermal degradation.

[0116] To obtain a powder with a desired composition, in the grinding step, instead of the calcined powder, a mixed powder of calcined powder, an alumina source, and an additive source may be ground. Examples of additive sources include those described above. When mixing an additive source in the grinding step, the content of the additive source should be such that the sum of the mass ratios of Al converted to Al2O3, Ge converted to GeO2, and Si converted to SiO2, relative to the total mass of Zr, Y, and one or more selected from the group of Al, Ge, and Si in the mixed powder converted to ZrO2, Y2O3, Al2O3, GeO2, and SiO2, is 0.05% by mass or more and 30% by mass or less, preferably more than 0.1% by mass and 25% by mass or less, and more preferably more than 0.2% by mass and 20% by mass or less.

[0117] The grinding method is arbitrary and may be at least one of wet grinding or dry grinding, with wet grinding being preferred. Specific examples of wet grinding include one or more selected from the group consisting of ball mills, vibratory mills, and continuous media stirring mills, with ball mills being preferred. Examples of grinding conditions using a ball mill include mixing calcined powder with a solvent to form a slurry in which the mass ratio of calcined powder to the total slurry mass is 30% by mass or more and 60% by mass or less, and then grinding this slurry using zirconia balls with a diameter of 1 mm or more and 15 mm or less as the grinding medium for 10 hours or more and 100 hours or less.

[0118] After wet grinding, the material can be dried by any method to obtain a powder. Examples of drying conditions include an air atmosphere and a temperature of 110°C to 130°C.

[0119] To improve the handling of the powder, the powder manufacturing method of this embodiment may include a step of granulating the powder (hereinafter also referred to as the "granulation step"). Granulation can be performed by any method, but one example is spray granulation of a slurry obtained by mixing the powder with a solvent. The solvent is at least one of water and alcohol, preferably water. The granulated powder (hereinafter also referred to as "powder granules") has an average granule size of 30 μm to 80 μm, more specifically 40 μm to 60 μm, and more specifically 50 μm to 60 μm, and a bulk density of 1.00 g / cm³. 3 More than 1.40g / cm 3 Furthermore, 1.10 g / cm³ 3 More than 1.30g / cm 3 The following are some examples: [Examples]

[0120] The present disclosure will be described below using examples. However, the present disclosure is not limited to these examples.

[0121] (Average sol particle size) The average particle size of the zirconia sol was measured using a dynamic light scattering particle size distribution analyzer (device name: UPA-UT151, manufactured by Microtrac-Bell). As a sample pretreatment, the hydrated zirconia sol-containing solution was suspended in pure water and dispersed for 3 minutes using an ultrasonic homogenizer.

[0122] (Monoclinicity, tetragonality, D of the powder) t and D m ) A standard X-ray diffractometer (product name: UltimaIIV, manufactured by Rigaku Corporation) was used to obtain the XRD pattern of the powder sample. The conditions for the XRD measurement were as follows: Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ = 26° ~ 33°

[0123] Using the obtained XRD pattern and the calculation program "PRO-FIT", the monoclinic ratio, tetragonal ratio, and D are calculated using equations (1), (2), (4), and (5), respectively. t and D m They sought it.

[0124] (BET specific surface area) The BET specific surface area of ​​powder samples was measured using a general-purpose fluidized bed specific surface area automatic analyzer (device name: FlowSorb III2305, manufactured by Shimadzu Corporation) and nitrogen as the adsorption gas, in accordance with JIS R 1626-1996. Prior to measurement, the powder samples were pre-treated by degassing in an air atmosphere at 250°C for 30 minutes.

[0125] (Particle size distribution measurement) The volume particle size distribution curve of a powder sample was measured using the HRA mode of a Microtrac particle size analyzer (product name: MT3000II, manufactured by Microtrac-Bell), and the median diameter was determined. Prior to measurement, the powder sample was suspended in pure water and dispersed for 10 minutes using an ultrasonic homogenizer as a pretreatment.

[0126] (Molded object density) The mass of the molded sample was measured using a balance, and its volume was measured using calipers to determine its dimensions. The measured density was then calculated from the obtained mass and volume. The theoretical density was calculated using equations (6) to (9), and the relative density (%) was determined from the value of the measured density (ρ) relative to the theoretical density (ρ0), and this was used as the molded body density.

[0127] (Monoclinic fraction and monoclinic intensity ratio of sintered body) The sintered body sample was subjected to XRD measurement under the same conditions as the powder sample. Using the obtained XRD patterns and the "PRO-FIT" calculation program, the monoclinic fraction and monoclinic intensity ratio were determined using equations (1) and (3), respectively.

[0128] For XRD measurements, sintered samples were used that had their surfaces ground using a surface grinder, followed by automatic polishing with waterproof sandpaper (800 grit), automatic polishing with a diamond slurry with an average particle size of 3 μm, and automatic polishing with 0.03 μm colloidal silica, resulting in a mirror-finish surface with a surface roughness (Ra) of ≤0.04 μm. An automatic polishing machine (machine name: MECATECH 334, manufactured by PRESI) was used for the automatic polishing.

[0129] (Sintered body density) The actual density of the sintered body sample was measured using the Archimedes method. Prior to the measurement, the mass of the dried sintered body was measured, and then the sintered body was placed in water and boiled for 1 hour as a pretreatment. The theoretical density was calculated from equations (6) to (9), and the relative density (%) was determined from the value of the measured density (ρ) relative to the theoretical density (ρ0), and this was used as the sintered body density.

[0130] (Average grain size) The average grain size was determined using the planimetric method with SEM (Scanning Electron Microscopy) images of sintered samples obtained by field emission scanning electron microscopy. Specifically, a circle of known area was drawn on the SEM image, and the number of crystal grains within that circle (Nc) and the number of crystal grains on the circumference of that circle (Ni) were measured.

[0131] Assuming a total of 250 ± 50 crystal grains (Nc + Ni), the average grain size was calculated using the following formula. Average grain size=(Nc+(1 / 2)×Ni) / (A / M 2 )

[0132] In the above equation, Nc is the number of crystal grains within the circle, Ni is the number of crystal grains on the circumference of the circle, A is the area of ​​the circle, and M is the magnification of the scanning electron microscope (5000x). If the number of crystal grains (Nc+Ni) in one SEM observation image is less than 200, multiple SEM observation images were used to determine (Nc+Ni) to be 250±50.

[0133] Prior to measurement, the sintered body samples were pre-treated by mirror polishing followed by thermal etching. For mirror polishing, the surface of the sintered body was ground using a surface grinding machine, and then polished using a mirror polishing device with diamond abrasive grains of average particle sizes of 9 μm, 6 μm, and 1 μm in sequence.

[0134] (Shift value) A surface powder X-ray diffractometer (device name: Auto MATE, manufactured by Rigaku Corporation) equipped with Crkβ rays as a radiation source was used to measure the shift values ​​of the tetragonal zirconia (113) plane under the following conditions.

[0135] Radiation source: Crkα radiation (λ=2.29100nm) Acceleration voltage: 30kV Current: 30mA Measurement method: Parallel tilt method Collimator diameter: 4mm Measurement lattice plane: Tetragonal zirconia (113) plane Tilting angle ψ: 0° and 45° The obtained 2θ (0°) and 2θ (45°) The shift value was calculated from the value of [the variable].

[0136] (Fracture toughness value) The fracture toughness of the sintered body specimens was measured according to the SEPB method specified in JIS R1607. The measurement was performed using a columnar sintered body specimen with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm. The average value of 10 measurements was used as the fracture toughness value.

[0137] (Bending strength) The bending strength of the sintered body specimens was measured using a three-point bending test in accordance with JIS R1601. The measurement was performed using a columnar sintered body specimen with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements was used as the bending strength.

[0138] (Total light transmittance) Total light transmittance was measured using a spectrophotometer (model: V-650, manufactured by JASCO Corporation) in accordance with JIS K 7361. A disc-shaped sample was used for the measurement. Prior to the measurement, both sides of the sample were polished to a sample thickness of 1 mm and a surface roughness (Ra) of 0.02 μm or less. Light with wavelengths from 220 to 850 nm was transmitted through the sample and focused with an integrating sphere to measure the transmittance at each wavelength. The transmittance at a wavelength of 600 nm was defined as the total light transmittance.

[0139] The measurement conditions for total light transmittance are as follows: Bandwidth: 5.0nm Data acquisition interval: 0.5nm Scanning speed: 1000 nm / min

[0140] Synthesis Example 1 An aqueous solution of zirconium oxychloride with zirconium concentration and chloride ion concentration of 0.4 mol / L each was hydrolyzed. The aqueous solution after hydrolysis was ultrafiltered using an ultrafiltration membrane (molecular weight cutoff: 6000) to obtain a zirconia sol with an average sol particle size of 250 nm. Zr The levels were below the detection limit (0.01 mass% or less).

[0141] To the zirconia sol aqueous solution after ultrafiltration, yttrium chloride hexahydrate and ammonia aqueous solution were added to obtain a precipitate to a concentration of 1.6 mol% yttria. The obtained precipitate was washed with pure water and dried in an air atmosphere, then calcined in an air atmosphere at a calcination temperature of 1025°C for 2 hours to obtain calcined powder. The BET specific surface area of ​​the obtained calcined powder was 12.5 m². 2 The crystallite size for the monoclinic crystal was 35 nm.

[0142] The calcined powder was mixed with pure water to form a slurry, which was then ball-milled using zirconia balls. This slurry was then dried in an air atmosphere at 120°C to obtain a powder consisting of yttria-containing zirconia with an yttria content of 1.6 mol%, which was used as the powder for this synthesis example. In this synthesis example, the yttria was completely dissolved in the zirconia, and its crystalline phases were monoclinic zirconia and tetragonal zirconia. The median diameter was 0.15 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.33 μm, with a particle-size peak ratio of 0.39.

[0143] Synthesis Example 2 A powder was obtained in the same manner as in Synthesis Example 1, except that a mixed powder of calcined powder and 0.25 mass% of alumina sol (in terms of Al2O3) was ball-milled. The powder contained 0.25 mass% of alumina (in terms of Al2O3), with the remainder being 1.6 mol% yttria-containing zirconia. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.32 μm, with a particle-size peak ratio of 0.37.

[0144] Synthesis Example 3 Except for setting the calcination temperature to 1130°C and performing ball milling on a mixed powder of the calcined powder and 0.25 mass% of alumina sol (in terms of Al2O3), a powder was obtained in the same manner as in Synthesis Example 1, containing 0.25 mass% of alumina (in terms of Al2O3) with the remainder being 1.6 mol% yttria-containing zirconia.

[0145] The BET specific surface area of ​​the obtained calcined powder was 6.7 m². 2 The crystallite size of the monoclinic form was 44 nm. The median diameter of the powder in this synthesis example was 0.18 μm, and the volume-to-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.36 μm, with a particle-size peak ratio of 0.85.

[0146] Synthesis Example 4 Except for adding yttrium chloride hexahydrate to the ultrafiltration-resolved zirconia sol aqueous solution so that the yttria content was 2 mol%, and ball-milling the mixed powder of calcined powder and 0.25 mass% alumina sol (in terms of Al2O3), a powder was obtained that contained 0.25 mass% alumina (in terms of Al2O3) and the remainder being 2 mol% yttria-containing zirconia, using the same method as in Synthesis Example 1. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume particle size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.33 μm, with a particle size peak ratio of 0.33.

[0147] Synthesis Example 5 Except for ball milling a mixed powder of calcined powder and 20% by mass of alumina powder (in terms of Al2O3), a powder containing 20% ​​by mass of alumina (in terms of Al2O3) and the remainder being 1.6 mol% yttria-containing zirconia was obtained using the same method as in Synthesis Example 1. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.35 μm, with a particle-size peak ratio of 0.41. Furthermore, the crystallite size (D) of tetragonal zirconia was also determined. t The wavelength was 42 nm.

[0148] Synthesis Example 6 Except for setting the calcination temperature to 1130°C and performing ball milling on a mixed powder of the calcined powder and 20% by mass of alumina powder (in terms of Al2O3), a powder containing 20% ​​by mass of alumina (in terms of Al2O3) and the remainder being 1.6 mol% yttria-containing zirconia was obtained using the same method as in Synthesis Example 1. The median diameter of the powder in this synthesis example was 0.16 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.35 μm, with a particle-size peak ratio of 0.67.

[0149] Synthesis Example 7 Except for adding yttrium chloride hexahydrate to the ultrafiltration-resolved zirconia sol aqueous solution so that the yttria content was 2 mol%, and ball-milling the mixed powder of calcined powder and 5 mass% alumina sol (in terms of Al2O3), a powder was obtained that contained 5 mass% alumina (in terms of Al2O3) and the remainder being 2 mol% yttria-containing zirconia, using the same method as in Synthesis Example 1. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume particle size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.35 μm, with a particle size peak ratio of 0.41.

[0150] Synthesis Example 8 Except for ball milling a mixed powder of calcined powder and 0.5 mass% of alumina sol (in terms of Al2O3), a powder containing 0.5 mass% of alumina (in terms of Al2O3) and the remainder being 1.6 mol% yttria-containing zirconia was obtained using the same method as in Synthesis Example 1. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.32 μm, with a particle-size peak ratio of 0.49.

[0151] Synthesis Example 9 A powder containing 1% by mass of alumina (based on Al2O3) and the remainder being 1.6 mol% yttria-containing zirconia was obtained using the same method as in Synthesis Example 1, except that a mixed powder of calcined powder and 1% by mass of alumina sol (based on Al2O3) was ball-milled. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume-to-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.34 μm, with a particle size peak ratio of 0.49.

[0152] Synthesis Example 10 A powder was obtained in the same manner as in Synthesis Example 1, except that a mixed powder of calcined powder and germanium oxide equivalent to 0.25 mass% of GeO2 was ball-milled, and the remainder consisted of zirconia containing 0.25 mass% of germanium oxide of GeO2 equivalent. The median diameter of the powder in this synthesis example was 0.14 μm, and the volume-to-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.34 μm, with a particle size peak ratio of 0.37.

[0153] Synthesis Example 11 A powder was obtained in the same manner as in Synthesis Example 1, except that a mixed powder of calcined powder and silica sol equivalent to 0.25% by mass in terms of SiO2 was ball-milled. The powder contained 0.25% by mass in terms of SiO2, with the remainder being 1.6 mol% yttria-containing zirconia. The median diameter of the powder in this synthesis example was 0.18 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.35 μm, with a particle-size peak ratio of 0.89.

[0154] Synthesis Example 12 Except for ball milling a mixed powder of calcined powder and 0.25 mass% alumina sol (in Al2O3 equivalent) and 0.25 mass% germanium oxide (in GeO2 equivalent), a powder was obtained in the same manner as in Synthesis Example 1, containing 0.25 mass% alumina (in Al2O3 equivalent) and 0.25 mass% germanium oxide (in GeO2 equivalent), with the remainder being 1.6 mol% yttria-containing zirconia. The median diameter of the powder in this synthesis example was 0.15 μm, and the volume-particle-size distribution curve was a bimodal distribution with peaks at particle sizes of 0.14 μm and 0.34 μm, with a particle-size peak ratio of 0.37.

[0155] Comparative Synthesis Example 1 Aqueous solutions of zirconium oxychloride with zirconium and chloride ion concentrations of 0.37 mol / L and 0.74 mol / L, respectively, were hydrolyzed. The aqueous solutions after hydrolysis were ultrafiltered using an ultrafiltration membrane (molecular weight cutoff: 6000) to obtain a zirconia sol with an average sol particle size of 100 nm.Zr It was 9% by mass.

[0156] To the zirconia sol aqueous solution after ultrafiltration, yttrium chloride hexahydrate and ammonia aqueous solution were added to obtain a precipitate to a concentration of 2 mol% yttria. The obtained precipitate was washed with pure water and dried in an air atmosphere, then calcined in an air atmosphere at a calcination temperature of 1000°C for 2 hours to obtain a calcined powder.

[0157] The calcined powder was mixed with pure water to form a slurry, which was then ball-milled using zirconia balls. Finally, it was dried in an air atmosphere at 120°C to obtain a powder consisting of yttria-containing zirconia with an yttria content of 2 mol%, which was used as the powder for this comparative synthesis example.

[0158] Comparative Synthesis Example 2 A powder was obtained using the same method as in Comparative Synthesis Example 1, except that a mixed powder of calcined powder and alumina powder equivalent to 0.25% by mass in terms of Al2O3 was ball-milled, and the remainder consisted of 2 mol% yttria-containing zirconia.

[0159] Comparative Synthesis Example 3 A powder was obtained using the same method as in Comparative Synthesis Example 1, except that a mixed powder of calcined powder and 5% by mass of alumina powder (in terms of Al2O3) was ball-milled, with the remainder being 2 mol% yttria-containing zirconia.

[0160] Comparative Synthesis Example 4 A powder consisting of 0.9 mol% yttria-containing zirconia was obtained by the same method as in Synthesis Example 1, except that yttrium chloride hexahydrate and ammonia aqueous solution were added to the zirconia sol aqueous solution after ultrafiltration to obtain a precipitate with a yttria content of 0.9 mol%.

[0161] The evaluation results of the powders from these synthesis examples and comparative synthesis examples are shown in the table below.

[0162] [Table 1]

[0163] From the table above, the powders in the synthesis example and comparative synthesis examples 1 to 3 all have similar stabilizer content (yttria content) and additive content, but comparative synthesis examples 1 to 3 are D m It can be seen that the size is small and the monoclinic fraction is low. Furthermore, comparative synthesis example 4 is D m It can be seen that it is small.

[0164] Example 1 The powder from Synthesis Example 4 was subjected to mold pressing at a pressure of 70 MPa and CIP treatment at a pressure of 196 MPa to form a molded body. The obtained molded body was subjected to atmospheric pressure sintering in an air atmosphere at a sintering temperature of 1200°C for 2 hours to obtain a pre-sintered body. The pre-sintered body was subjected to HIP treatment in an argon atmosphere at a processing pressure of 150 MPa and a processing temperature of 1500°C for 1 hour to obtain a HIP-treated body. This was then fired in an air atmosphere at 1000°C for 1 hour to obtain the sintered body (HIP-treated body) of this embodiment.

[0165] Example 2 Except for using the powder from Synthesis Example 5, setting the sintering temperature for pre-sintering to 1350°C, and setting the HIP treatment temperature to 1500°C, a molded body and a sintered body were obtained in the same manner as in Example 1.

[0166] Example 3 Except for using the powder from Synthesis Example 6, setting the sintering temperature for pre-sintering to 1350°C, and setting the HIP treatment temperature to 1500°C, molded and sintered bodies were obtained in the same manner as in Example 1.

[0167] Example 4 Molded bodies and sintered bodies were obtained in the same manner as in Example 1, except that the powder from Synthesis Example 7 was used and the HIP treatment temperature was set to 1500°C.

[0168] Example 5 Except for using the powder from Synthesis Example 8, setting the sintering temperature for pre-sintering to 1175°C, and setting the HIP treatment temperature to 1250°C, the molded body and sintered body were obtained in the same manner as in Example 1.

[0169] Example 6 Except for using the powder from Synthesis Example 9, setting the sintering temperature for pre-sintering to 1175°C, and setting the HIP treatment temperature to 1250°C, the molded body and sintered body were obtained in the same manner as in Example 1.

[0170] Example 7 Except for using the powder from Synthesis Example 9, setting the sintering temperature for pre-sintering to 1175°C, and setting the HIP treatment temperature to 1350°C, the molded body and sintered body were obtained in the same manner as in Example 1.

[0171] Example 8 Except for using the powder from Synthesis Example 10, setting the sintering temperature for pre-sintering to 1200°C, and setting the HIP treatment temperature to 1250°C, a molded body and a sintered body were obtained in the same manner as in Example 1.

[0172] Example 9 Except for using the powder from Synthesis Example 12, setting the sintering temperature for pre-sintering to 1175°C, and setting the HIP treatment temperature to 1250°C, a molded body and a sintered body were obtained in the same manner as in Example 1.

[0173] Example 10 Molded bodies and sintered bodies were obtained in the same manner as in Example 1, except that the powder from Synthesis Example 2 was used and the HIP treatment temperature was set to 1350°C.

[0174] The evaluation results of the sintered bodies in the examples, along with the relative density of the pre-sintered bodies, are shown in the table below.

[0175] [Table 2]

[0176] From the table above, the bending strength exceeds 1450 MPa, and the fracture toughness value is 6.0 MPa·m. 0.5 It can be confirmed that a sintered body (HIP-treated body) meeting the above criteria can be obtained. Furthermore, a fracture toughness value of 7.0 MPa·m 0.5 Furthermore, the sintered body has a bending strength of 1460 MPa, and a fracture toughness value of 8.0 MPa·m. 0.5 Furthermore, it can be confirmed that a sintered body with a bending strength of 1550 MPa can be obtained.

[0177] Measurement example 1 (total light transmittance) The total light transmittance of the sintered bodies in the examples was measured. The main results are shown in the table below.

[0178] [Table 3]

[0179] The table above shows a tendency for total light transmittance to decrease with increasing amounts of additives. Furthermore, it can be confirmed that when the additive content is between 0.25% by mass and 1.0% by mass, the total light transmittance is 25% or higher, 30% or higher, and even 35% or higher.

[0180] Measurement Example 2 (Shift Value) The shift value of the sintered body of Example 10 was measured. For comparison, the shift value of a sintered body (comparative sintered body) prepared using commercially available 2mol% yttria-containing zirconia powder (product name: TZ-2Y, manufactured by Tosoh Corporation) was also measured. This body was pre-sintered at a sintering temperature of 1450°C, followed by HIP treatment at a processing temperature of 1500°C. The results are shown in the table below.

[0181] [Table 4]

[0182] Compared to a comparative sintered body made using commercially available powder and HIP treatment, the sintered body of Example 10 was found to have higher shift values ​​and fracture toughness values.

[0183] Measurement Example 3 (Evaluation of Machinability) Each of the sintered bodies from the examples was processed to a sample thickness of 0.09 mm. In all cases, processing to a measurement sample thickness of 0.09 mm was successful without the appearance of cracks or other defects.

[0184] As a comparative measurement example, the powder from Comparative Synthesis Example 1 was subjected to mold pressing at a pressure of 70 MPa and CIP treatment at a pressure of 196 MPa. The resulting molded body was then sintered at atmospheric pressure in an air atmosphere at a sintering temperature of 1450°C for 2 hours to obtain a sintered body. When this sintered body was processed in the same manner, it cracked during processing, making it impossible to process it into thin pieces. The thickness of the cracked sintered body fragment was approximately 0.3 mm.

[0185] Measurement Example 4 (Compound Evaluation) Compounds were prepared using the powders from Synthesis Examples 2 and 3, respectively. Specifically, the powders were dried at 150°C for more than one hour, and then the powders and acrylic resin were added to a kneader mill (device name: Labon Kneader Mill TDR-3, manufactured by Toshin Co., Ltd.) so that the mass of the powder was 85% by mass relative to the mass of the resulting compound. The compound was then kneaded at 160°C to obtain the compound. The kneadability of the compound was evaluated by measuring the torque (N·m) applied to the kneader 15 minutes after the start of kneading. A smaller torque value indicates a compound that is easier to knead, i.e., a compound with superior kneadability.

[0186] Fluidity was evaluated by measuring the flow velocity of the compound sample using a flow tester. A general-purpose flow tester (device name: Flow Tester CFT500D, manufactured by Shimadzu Corporation) was used for the measurement, and the compound was filled into a syringe. A load was applied to the compound under the following conditions, and the volume velocity (cm³) of the compound injected from the syringe was measured. 3 Fluidity was confirmed by measuring the volume velocity ( / s). The measurement conditions are shown below. A higher volume velocity indicates a compound that flows more easily in the molten state, i.e., a compound with superior fluidity.

[0187] Syringe area: 1 cm² 2 Die hole diameter: 1 mm Die length: 2mm Load capacity: 50kg Measurement temperature: 160℃ Compound density: 3.0 g / cm³ 3 Additionally, as a comparative measurement example, the BET specific surface area is 15.0 m². 2 A 3 mol% yttria-containing zirconia powder with a particle size / g and average particle diameter (median diameter) of 1.1 μm was evaluated similarly. The evaluation results of the compounds are shown in the table below. Note that the powder in the comparative measurement example had poor kneadability and could not be kneaded at 160°C. Therefore, the kneadability values ​​for the comparative measurement example in the table below represent the values ​​obtained when kneaded at 170°C.

[0188] [Table 5]

[0189] Compared to the powder in the comparative measurement example, the powder of synthesis example 3, which had a lower BET specific surface area, exhibited superior kneadability and fluidity, with particularly high fluidity. Furthermore, despite synthesis example 2 and the comparative measurement example having similar BET specific surface areas, the powder of synthesis example 2 had significantly higher fluidity than the powder in the comparative measurement example. These results indicate that the powders in the synthesis examples also exhibit excellent properties as compositions (compounds) consisting of powder and resin.

Claims

1. The material contains zirconia containing a stabilizer, wherein the stabilizer is yttria, the content of the stabilizer is 1.0 mol% or more and 2.0 mol% or less, the monoclinic fraction is 0.5% or more, and the fracture toughness value measured by a method conforming to the SEPB method specified in JIS R1607 is 6 MPa·m. ０．５ 11MPa・m or more ０．５ A zirconia sintered body that is as follows, and moreover, has a three-point bending strength exceeding 1450 MPa as determined by a three-point bending test in accordance with JIS R 1601.

2. The zirconia sintered body according to claim 1, wherein the total light transmittance for light with a wavelength of 600 nm at a sample thickness of 1.0 mm is 20% or more.

3. A zirconia sintered body according to claim 1 or 2, wherein the ratio of the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia is 0 or more.

4. A zirconia sintered body according to any one of claims 1 to 3, wherein the average crystal grain size is 0.50 μm or more and 0.65 μm or less.

5. A zirconia sintered body according to any one of claims 1 to 4, wherein the relative density is 99.7% or more and 100% or less.

6. The zirconia sintered body according to any one of claims 1 to 4, wherein the content of the stabilizer is 1.0 mol% or more and less than 1.9 mol%.

7. A zirconia sintered body according to any one of claims 1 to 6, wherein the thickness of the sintered body is 0.05 mm or more and 0.3 mm or less.

8. A zirconia sintered body according to any one of claims 1 to 7, wherein the shift value of the tetragonal zirconia (113) plane is 0.15° or more.

9. A zirconia sintered body according to any one of claims 1 to 8, comprising one or more additive components selected from the group consisting of alumina, germania, and silica.

10. The zirconia sintered body according to claim 9, wherein the additive component is alumina.

11. The zirconia sintered body according to any one of claims 1 to 10, wherein the zirconia comprises monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia.

12. A zirconia sintered body according to any one of claims 1 to 11, wherein the ratio of the tetragonal structure after immersion treatment in 140°C hot water for 6 hours to the tetragonal structure before immersion treatment in 140°C hot water for 6 hours is 15% or more.

13. A method for producing a zirconia sintered body according to any one of claims 1 to 12, comprising the steps of: sintering a powder containing a stabilizer, containing zirconia with a monoclinic content exceeding 70%, having a crystallite size of monoclinic zirconia exceeding 23 nm and 80 nm or less, and having a volume particle size distribution curve that is multimodal, to obtain a pre-sintered body with a relative density of 99% or less; and pressurizing the pre-sintered body.

14. The manufacturing method according to claim 13, wherein the pressure sintering is a hot hydrostatic press treatment.

15. A member comprising a zirconia sintered body according to any one of claims 1 to 12.

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