Sintered body, powder and method for producing the same

Abstract

To provide at least one of: a raw material for obtaining a zirconia sintered body which is obtained by pressureless sintering and has a high fracture toughness value measured by the SEPB method; a sintered body obtained by the raw material; and a method for producing the same.SOLUTION: A sintered body comprises zirconia which contains a stabilizer and having a monoclinic ratio of 0.5% or more. Such a sintered body is preferably obtained by a production method which is characterized by using a powder comprising a stabilizer and containing zirconia having a monoclinic ratio of over 70%, the monoclinic zirconia having a crystallite diameter of over 23 nm and 80 nm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a sintered body having zirconia as a main phase, a powder serving as a raw material thereof, and a method for producing the same. [Background technology]

[0002] In addition to conventional uses requiring strength, such as grinding media and structural materials, zirconia sintered bodies are being considered for use in decorative applications such as decorative parts for watches, portable electronic devices, automobiles, home appliances, etc. Sintered bodies used for decorative purposes are required to have reduced brittleness, i.e., high fracture toughness.

[0003] Various zirconia sintered bodies have been reported so far with the aim of improving fracture toughness. For example, Patent Document 1 reports a zirconia-alumina composite sintered body obtained by mixing a commercially available 3 mol% yttria-containing zirconia powder produced by the neutralization coprecipitation method with a commercially available alumina powder to prepare a mixed powder, and then microwave sintering the mixed powder. The fracture toughness (K IC ) is 6.02 to 6.90 MPa m 1 / 2 It is stated that:

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

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-226555 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-178610 Summary of the Invention [Problem to be solved by the invention]

[0006] The zirconia sintered bodies disclosed in Patent Documents 1 and 2 require special sintering methods, such as microwave sintering or HIP treatment, to be produced, making them difficult to apply industrially. However, when applying them to decorative parts, it is also necessary to evaluate the brittleness of the sintered body using a highly reliable fracture toughness value. There are multiple standardized methods for measuring fracture toughness, and the values obtained vary greatly depending on the method. The fracture toughness value in Patent Document 1 was measured using a simple method, and the measurement method for the fracture toughness value in Patent Document 2 is unclear, making the disclosed values unreliable.

[0007] An object of the present disclosure is to provide at least one of a raw material for obtaining a zirconia sintered body obtained by atmospheric sintering and having a high fracture toughness value measured by the SEPB method, a sintered body obtained from the raw material, and methods for producing the same. [Means for solving the problem]

[0008] The gist of the present disclosure is as follows. [1] A sintered body comprising zirconia containing a stabilizer, the sintered body having a monoclinic ratio of 0.5% or more. [2] The sintered body according to the above [1], wherein the ratio of the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia is 0 or more. [3] The sintered body according to the above [1] or [2], wherein the stabilizer is one or more selected from the group consisting of yttria, calcia, magnesia and ceria. [4] The sintered body according to any one of [1] to [3] above, wherein the content of the stabilizer is 1.0 mol % or more and less than 2.5 mol %. [5] Fracture toughness measured using the SEPB method specified in JIS R1607 is 6 MPa m 0.5More than 11MPa m 0.5 The sintered body according to any one of the above [1] to [4], which is: [6] The sintered body according to any one of [1] to [5] above, which contains one or more additive components selected from the group consisting of alumina, germania, and silica. [7] The sintered body according to any one of [1] to [6] above, wherein the additive component is alumina. [8] The sintered body according to any one of the above [1] to [7], wherein the zirconia contains monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia. [9] A sintered body according to any one of [1] to [8] above, in which the ratio of the tetragonal crystal ratio after immersion treatment in hot water at 140°C for 6 hours to the tetragonal crystal ratio before immersion treatment in hot water at 140°C for 6 hours is 15% or more.

[10] A method for producing a sintered body according to any one of [1] to [9] above, characterized in that a powder containing a stabilizer, containing zirconia with a monoclinic fraction of more than 70%, and having a crystallite diameter of monoclinic zirconia of more than 23 nm and not more than 80 nm is used.

[11] A powder containing a stabilizer, containing zirconia with a monoclinic crystal ratio of more than 70%, and characterized in that the crystallite diameter of the monoclinic zirconia is more than 23 nm and not more than 80 nm.

[12] The powder according to

[11] above, wherein the zirconia crystal phase comprises monoclinic zirconia and tetragonal zirconia.

[13] The powder according to

[11] or

[12] above, wherein the stabilizer is one or more selected from the group consisting of yttria, calcia, magnesia and ceria.

[14] The powder according to any one of

[11] to

[13] above, wherein the content of the stabilizer is 1.0 mol% or more and less than 2.5 mol%.

[15] The powder according to any one of

[11] to

[14] above, which contains one or more additive components selected from the group consisting of alumina, germania, and silica.

[16] The powder according to

[15] above, wherein the content of the additive component is 0.1% by mass or more and 30% by mass or less.

[17] BET specific surface area is 6m2 / g or more 20m 2 The powder according to any one of

[11] to

[16] above, wherein the average particle size is less than 1 / g.

[18] The powder according to any one of

[11] to

[17] above, having a median diameter of 0.05 μm or more and 0.3 μm or less.

[19] A member comprising the sintered body according to any one of [1] to [9] above. [Effects of the Invention]

[0009] The present disclosure makes it possible to provide at least one of a raw material for obtaining a zirconia sintered body obtained by atmospheric sintering and having a high fracture toughness value measured by the SEPB method, a sintered body obtained from the raw material, and methods for producing the same. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the present disclosure will be described with reference to an example embodiment.

[0011] The terms used in this embodiment are as follows:

[0012] The "monoclinic fraction" and "tetragonal fraction" are the proportions of monoclinic zirconia and tetragonal zirconia in the zirconia crystal phase, respectively. The "monoclinic intensity 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 zirconia crystal phase.

[0013] For powders, the powder X-ray diffraction (hereinafter also referred to as "XRD") pattern of the powder is used, while for sintered bodies, the XRD pattern of the surface of the sintered body after mirror polishing is used, and the monoclinic fraction can be calculated from the following formula (1), the tetragonal fraction from the following formula (2), and the monoclinic intensity ratio from the following formula (3).

[0014] f m ={I m (111)+Im (11-1)} / [I m (111) +I m (11-1)+I t (111)+I c (111)]×100 (1) f t =I t (111) / [I m (111)+I m (11-1) +I t (111)+I c (111)]×100 (2) M (11-1) / (111) ={I m (11-1) / I m (111)} (3 )

[0015] In formulas (1) to (3), f m is the monoclinic ratio (%), f t is the tetragonal crystal ratio (%), M (11-1) / (111) is the monoclinic intensity ratio, I m (111) and I m (11-1) are the area intensities of the XRD peaks corresponding to the (111) and (11-1) planes of monoclinic zirconia, respectively, and I t (111) is the area intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia, and I c (111) is the area intensity of the XRD peak corresponding to the (111) plane of cubic zirconia.

[0016] The conditions for measuring the XRD pattern include the following.

[0017] Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=26°~33°

[0018] In the above-mentioned XRD pattern measurement, preferably, the XRD peaks corresponding to the respective crystal planes of zirconia are measured as peaks having peak tops at the following 2θ angles.

[0019] 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 RD peaks corresponding to the (111) planes of tetragonal zirconia and cubic zirconia were measured in duplicate, and the 2θ angle of the peak top was 2θ=30±0.5°.

[0020] The area intensity of the XRD peak of each crystal plane can be determined by separating each XRD peak using the calculation program "PRO-FIT" according to the method described in H. Toraya, J. Appl. Crystallogr., 19, 440-447 (1986).

[0021] The surface of the sintered body subjected to the above-mentioned XRD measurement after surface polishing was ground using a surface grinder, and then the measurement surface was mirror-polished in the following order: automatic polishing with an abrasive cloth, automatic polishing with a diamond slurry with an average particle size of 3 μm, and automatic polishing with colloidal silica with a particle size of 0.03 μm, resulting in a sintered body with a surface roughness Ra of 0.04 μm or less.

[0022] "Crystalline diameter of monoclinic zirconia" (hereinafter referred to as "D m " is a value calculated from the XRD pattern of the powder using the following formula (4), and is referred to as "tetragonal zirconia crystallite diameter" (hereinafter referred to as "D t ") is a value calculated from the XRD pattern of the powder using the following formula (5).

[0023] D m =κλ / (βcosθ m ) (4) D t =κλ / (βcosθ t ) (5)

[0024] In equations (4) and (5), D m is the crystallite diameter of monoclinic zirconia (nm), D t is the crystallite diameter of tetragonal zirconia (nm), κ is the Scherrer constant (κ = 1), λ is the wavelength of the light source used for XRD measurement (nm), β is the half-width (°) after correcting for mechanical spreading using quartz sand (Wako Pure Chemical Industries, Ltd.) with a particle size of 25 to 90 μm, and θ m is the Bragg angle (°) of the reflection corresponding to the (11-1) plane of monoclinic zirconia in XRD measurement, and θ t is the Bragg angle (°) of the reflection corresponding to the (111) plane of tetragonal zirconia in XRD measurement. When CuKα radiation is used as the light source for XRD measurement, λ is 0.15418 nm.

[0025] The "BET specific surface area" is a value determined by the BET single-point method in accordance with JIS R 1626-1996, using nitrogen (N2) as the adsorbed substance.

[0026] "Particle size by volume distribution" refers to the particle size of a powder obtained by measuring the volume particle size distribution using a laser diffraction method. The particle size obtained by the laser diffraction method is a non-spherical approximation. The conditions for measuring the volume particle size distribution include the following:

[0027] Measurement sample: Powder slurry Refractive index of zirconia: 2.17 Refractive index of solvent (water): 1.333 Measurement time: 30 seconds Pretreatment: ultrasonic dispersion treatment

[0028] The "median size" is the particle size corresponding to a volume ratio of 50% on the cumulative volume particle size distribution curve obtained by measuring the volume particle size distribution using a laser diffraction method.

[0029] The "particle size distribution curve" is a curve showing the particle size distribution of a powder obtained by measuring the volume particle size distribution by laser diffraction method.

[0030] "Fracture toughness" is the fracture toughness value (MPa m) measured by the SEPB method specified in JIS R 1607. 0.5 ) The fracture toughness value is measured using a columnar sintered body sample with a support distance of 30 mm, a width of 4 mm, and a thickness of 3 mm, and the average value of 10 measurements can be used as the fracture toughness value of the sintered body of this embodiment. 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, since the IF method is a simple measurement method, there is a large variation in the measured values from measurement to measurement. Therefore, the absolute values of the fracture toughness value of this embodiment and the fracture toughness value measured by the IF method cannot be compared. Similarly, the absolute values of the fracture toughness values measured by the SEPB method cannot be compared with those measured by a method other than the SEPB method.

[0031] The "bending strength" refers to a value of three-point bending strength determined by a three-point bending test in accordance with JIS R 1601. The bending strength is measured using a columnar sintered body sample having a support distance of 30 mm, a width of 4 mm, and a thickness of 3 mm, and the bending strength of the sintered body of this embodiment may be determined by averaging 10 measurements.

[0032] "Total light transmittance" refers to the total light transmittance for light with a wavelength of 600 nm for a sample 1.0 mm thick, and can be measured using a method conforming to JIS K 7361. Light with a wavelength of 600 nm is used as the incident light, and the transmittance can be calculated as the sum of the diffuse transmittance and linear transmittance for that incident light. A sample with a thickness of 1 mm and a surface roughness (Ra) of 0.02 μm or less on both sides (the measurement surface and the surface opposite the measurement surface) is used as the measurement sample. A common spectrophotometer (e.g., V-650, manufactured by JASCO Corporation) is used to irradiate the sample with light with a wavelength of 600 nm, and the transmitted light is collected using an integrating sphere to measure the transmittance (diffuse transmittance and linear transmittance) of the sample, which can be used as the total light transmittance.

[0033] "In-line transmittance" refers to the total light transmittance for light with a wavelength of 600 nm for a sample thickness of 0.05 mm to 0.2 mm, preferably 0.05 mm to 0.15 mm, particularly 0.09 mm, and can be measured using a method in accordance with JIS K 7361. Light with a wavelength of 600 nm is used as the incident light, and the in-line transmittance for the incident light can be determined. A sample with a thickness of 1 mm and a surface roughness (Ra) of 0.02 μm or less on both sides (the measurement surface and the surface opposite the measurement surface) is used as the measurement sample. The in-line transmittance of the sample can be measured by irradiating the sample with light with a wavelength of 600 nm using a general spectrophotometer (e.g., V-650, manufactured by JASCO Corporation) and collecting the transmitted light using an integrating sphere.

[0034] "Relative density" is the ratio (%) of the measured density to the theoretical density. The measured density of a molded body is the ratio (g / cm) of the volume determined from dimensional measurement to the mass measured by mass measurement. 3 ), and the measured density of a sintered body is the ratio of the volume measured by Archimedes' method to the mass measured by gravimetric measurement (g / cm 3 ), and the theoretical density is the density (g / cm 3 ) calculated from the following equations (6) to (9): 3 )

[0035] 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)

[0036] In equations (6) to (9), ρ0 is the theoretical density, ρ Zis the theoretical density of zirconia, A and C are constants, X is the molar ratio (mol%) of yttria to the total of zirconia (ZrO2) and yttria (Y2O3), and Y A , Y G and Y S are the mass percentages (mass%) of alumina converted into Al2O3, germania converted into GeO2, and silica converted into SiO2 relative to the total of zirconia, yttria, alumina, germania, and silica converted into ZrO2, Y2O3, Al2O3, GeO2, and SiO2, respectively, of the green body or sintered body.

[0037] The sintered body of this embodiment will be described below.

[0038] This embodiment is a sintered body characterized by including zirconia containing a stabilizer and having a monoclinic ratio of 0.5% or more.

[0039] The sintered body of this embodiment is a sintered body containing zirconia containing a stabilizer, and is a sintered body having zirconia containing a stabilizer as a main phase, that is, a so-called zirconia sintered body.

[0040] The stabilizer has a function of stabilizing zirconia, and examples thereof include one or more selected from the group consisting of calcia (CaO), magnesia (MgO), ceria (CeO2), and yttria (Y2O3), with at least one of ceria and yttria being preferred, and yttria being more preferred. In the sintered body of this embodiment, the stabilizer content may be such that zirconia is partially stabilized. 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 1.0 mol% to 2.5 mol%, further 1.1 mol% to 2.2 mol%, or even 1.1 mol% to 2.0 mol%, preferably 1.2 mol% to less than 2.0 mol%, and more preferably 1.2 mol% to 1.8 mol%. A stabilizer content within this range tends to increase the fracture toughness measured by the SEPB method. The yttria content is preferably 1.4 mol% to 2.1 mol%, further preferably 1.5 mol% to 1.8 mol%.

[0041] The stabilizer is preferably dissolved in zirconia, and the sintered body of this embodiment preferably does not contain any undissolved stabilizer, and all of the stabilizer is preferably dissolved in zirconia, and more preferably does not have an XRD peak of the stabilizer in the XRD pattern of the sintered body of this embodiment. In this embodiment, if an XRD peak of the stabilizer can be confirmed as an XRD peak separate from the XRD peak of zirconia, it can be considered that the sintered body contains an undissolved stabilizer.

[0042] 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. By containing the additive component, the grain boundary strength between crystal grains tends to be high even when the content of the zirconia stabilizer is small. When the additive component is contained, the sintered body of this embodiment contains the additive component, with the remainder being zirconia containing a stabilizer. The content of the additive component is the mass ratio of the additive component to the total mass of the zirconia, yttria, and additive component of the sintered body. For example, a sintered body containing alumina as an additive component, with the remainder being zirconia containing yttria, {Al2O3 / (ZrO2+Y2O3+Al2O3)} × 100 [mass %]). The content of the additive component is, for example, 0.05 mass % or more and 30 mass % or less, preferably more than 0.1 mass % and 25 mass % or less, and more preferably 0.2 mass % or more and 20 mass % or less. If the content of the additive component is 0.02 mass % or more and 0.3 mass % or less, the mechanical strength tends to be high and transformation to monoclinic zirconia tends to be less likely to occur.

[0043] The sintered body of this embodiment preferably contains no impurities other than unavoidable impurities, such as hafnia (HfO2).

[0044] The sintered body of this embodiment has a monoclinic fraction of 0.5% or more, preferably 0.5% to 15%, and more preferably 0.8% to 12%. Because fracture toughness tends to be high, the monoclinic fraction 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 high, the monoclinic fraction is preferably 0.5% to 5%, and more preferably 0.8% to 3%.

[0045] The surface of a sintered body immediately after sintering (as-sintered surface; hereinafter also referred to as the "sintered surface") is rough and contains many sources of fracture, such as irregularities. To prevent the sintered body from being broken, the sintered surface is removed by processing such as grinding, and the sintered body is polished to expose a mirror-like surface (polished surface; hereinafter also referred to as the "mirror surface") prior to evaluation or use in various applications. A mirror surface is, for example, a smooth surface with Ra≦0.04 μm. The monoclinic fraction is the value of the mirror surface of a sintered body. In conventional sintered bodies having partially stabilized zirconia as the main phase, after mirror finishing such as processing and polishing, the crystalline phase consists of at least one of tetragonal zirconia and cubic zirconia, and contains substantially no monoclinic zirconia or only a small amount of monoclinic zirconia. Furthermore, sintered bodies with poor mechanical properties may be destroyed during mirror finishing, making them impossible to process into measurement samples, and even sintered bodies from which the monoclinic crystal ratio cannot be measured. In contrast, the sintered body of this embodiment has monoclinic zirconia on its mirror surface that satisfies the above-mentioned monoclinic crystal ratio. Therefore, it is considered that the sintered body of this embodiment is a sintered body that contains monoclinic zirconia throughout the sintered body, or a sintered body that contains tetragonal zirconia that is likely to transform into monoclinic zirconia.

[0046] In the sintered body of the present embodiment, the zirconia contains monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia, and is preferably made of monoclinic zirconia and tetragonal zirconia.

[0047] The monoclinic zirconia contained in the sintered body of this embodiment is monoclinic zirconia having an XRD pattern that corresponds to at least the monoclinic zirconia (111) plane. By including such monoclinic zirconia before the degradation treatment, the sintered body tends to exhibit high fracture toughness and is less susceptible to hydrothermal degradation. When monoclinic zirconia is produced due to degradation of the sintered body, the intensity of the XRD peak in the XRD pattern that corresponds primarily to the monoclinic zirconia (11-1) plane increases. In contrast, the monoclinic zirconia contained in the sintered body of this embodiment preferably has an XRD pattern that corresponds to at least the monoclinic zirconia (111) plane, and the monoclinic intensity ratio is preferably 0 or greater, more preferably 0.3 or greater, even more preferably 0.4 or greater, and even more preferably 0.5 or greater. 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 preferably 1.2 or less, or more preferably 1.0 or less. The monoclinic intensity ratio can be calculated from the formula (3). m In a sintered body in which (111) is zero, i.e., which does not have an XRD peak corresponding to the monoclinic zirconia (111) plane, the monoclinic intensity ratio becomes infinite and the value cannot be determined. In other words, it is preferable that the sintered body of this embodiment does not include a sintered body in which the monoclinic intensity ratio is infinite.

[0048] The average crystal grain size of the zirconia crystal grains in the sintered body of this embodiment varies depending on the sintering temperature, but may be, for example, any one of 0.1 μm to 0.8 μm, 0.15 μm to 0.60 μm, 0.20 μm to 0.55 μm, or 0.25 μm to 0.45 μm.

[0049] The sintered body of this embodiment preferably has a relative density (hereinafter also referred to as "sintered body density") of 98% or more and 100% or less, more preferably 98.4% or more and 100% or less, and even more preferably 99% or more and 100% or less.

[0050] Furthermore, the sintered body of this embodiment is preferably a sintered body obtained by atmospheric sintering (so-called atmospheric sintered body), and more preferably a sintered body obtained by atmospheric sintering in an air atmosphere. Furthermore, it is preferable that the sintered body is in a state in which no sintering treatment other than atmospheric sintering has been performed, and more preferably a state in which no sintering treatment has been performed after atmospheric sintering. Examples of sintering treatment other than atmospheric sintering include one or more selected from the group consisting of pressure sintering, vacuum sintering, and microwave sintering.

[0051] The sintered body of this embodiment has 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 m 0.5 For example, it is preferably 6.2 MPa m 0.5 More preferably, 7 MPa m 0.5 More preferably, 8 MPa m 0.5 A high fracture toughness value is preferable, but for example, 11 MPa m 0.5 Below, and further 10.5 MPa m 0.5 or less, or even 9.5 MPa m 0.5 Below 9 MPa m 0.5 or less, or even 8.5 MPa m 0.5 or less. By having such a fracture toughness value, it is easy to process the sintered body into a sintered body having a thickness of 1 mm or less, or even 0.5 mm or less. As a result, the sintered body of this embodiment may be made into a sintered body having a thickness of, for example, 0.05 mm or more and 0.3 mm or less, or even 0.08 mm or more and 0.25 mm or less.

[0052] The sintered body of this embodiment has a bending strength of, for example, 1000 MPa or more and 1550 MPa or less, further 1100 MPa or more and 1500 MPa or less, preferably 1100 MPa or more and 1460 MPa or less, and more preferably 1200 MPa or more and 1400 MPa or less.

[0053] The sintered body of this embodiment preferably has a total light transmittance of 20% to 50%, more preferably 25% to 45%, and even more preferably 30% to 40%. In particular, when the content of the additive component is more than 0% by mass and 25% by mass or less, more preferably 0.2% by mass to 5% by mass, and even more preferably 0.23% by mass to 3% by mass, the total light transmittance is preferably 20% to 45%, and even more preferably 25% to 40%.

[0054] The sintered body of this embodiment may have a linear transmittance of 1% to 20%, 1% to 15%, or 1% to 10%. The linear transmittance is a value measured on a sintered body having a sample thickness of 0.05 mm to 0.2 mm, preferably 0.05 mm to 0.15 mm, and particularly 0.09 mm. The linear transmittance in this embodiment is a value measured on such a sample thickness and differs from an estimated or calculated value obtained from the linear transmittance measured on a sintered body having a thicker sample thickness, such as a sintered body having a sample thickness of 0.5 mm or more.

[0055] The sintered body of this embodiment particularly preferably has an in-line transmittance of 1% to 10%, 1.5% to 8%, 2% to 7.5%, or 2.5% to 7.3% at a sample thickness of 0.09 mm.

[0056] The tetragonal zirconia contained in the sintered body of this embodiment is preferably resistant to transformation to monoclinic zirconia by hydrothermal treatment (hereinafter also referred to as "hydrothermal deterioration"). 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 (hereinafter also referred to as "residual tetragonal fraction" or "ΔT%") is preferably 15% or more, more preferably 70% or more, and even more preferably 80% or more. If tetragonal zirconia does not transform to monoclinic zirconia by immersion in hot water at 140°C for 6 hours, the residual tetragonal fraction will be 100%, so the residual tetragonal fraction in the sintered body of this embodiment is 100% or less, and even 95% or less.

[0057] The higher the content of the additive component, the more the hydrothermal degradation tends to be suppressed. In the sintered body of this embodiment, when the content of the additive component is 0% by mass, i.e., when no additive component is contained, the residual tetragonal ratio can be, for example, 15% to 100%, preferably 20% to 100%, and more preferably 50% to 80%. When the sintered body of this embodiment contains an additive component and the content of the additive component is more than 0% by mass and less than 5% by mass, the residual tetragonal ratio can be, for example, 65% to 100%, preferably 70% to 90%. When the sintered body of this embodiment contains an additive component and the content of the additive component is more than 5% by mass and less than 30% by mass, the residual tetragonal ratio can be, for example, 70% to 100%, preferably 76% to 95%.

[0058] The shape of the sintered body of this embodiment may be any desired shape, including basic shapes such as cube, rectangular parallelepiped, polygonal, plate, disk, column, cone, sphere, and approximately spherical, as well as shapes of components suitable for various uses.

[0059] Although any method for producing the sintered body of this embodiment may be used, it is preferable to use a powder containing a stabilizer, containing zirconia with a monoclinic fraction of more than 70%, and having a monoclinic zirconia crystallite diameter of more than 23 nm and not more than 80 nm as a raw material. After molding this powder, it can be sintered by a known method. Furthermore, at least one of calcination and processing may be performed before sintering, as necessary.

[0060] The molding may be carried out by a known method, for example, at least one method selected from the group consisting of uniaxial pressing, cold isostatic pressing, slip casting, and injection molding, and is preferably at least one method selected from the group consisting of uniaxial pressing, cold isostatic pressing, and injection molding.

[0061] The calcination may be carried out by heat treating the powder at a temperature lower than the sintering temperature, for example, at a temperature of 800°C or higher and lower than 1200°C in the atmosphere.

[0062] Sintering can be carried out by any known method, such as one or more selected from the group consisting of pressure sintering, vacuum sintering, and atmospheric sintering. Because it is simple and easy to apply industrially, atmospheric sintering is preferred, more preferably atmospheric sintering in the air at 1200°C to 1550°C, preferably 1250°C to 1500°C, and even more preferably atmospheric sintering in the air at 1300°C to 1450°C. It is also preferable not to perform any sintering other than atmospheric sintering.

[0063] The sintered body of this embodiment can be used as a component containing the sintered body in the same applications as known zirconia sintered bodies. The sintered body of this embodiment is suitable for crusher components, precision machine parts, structural materials such as optical connector parts, biomaterials such as dental materials, decorative materials, and exterior materials such as electronic device exterior parts.

[0064] The powder of this embodiment will be described below.

[0065] This embodiment is a powder characterized by containing a stabilizer, including zirconia with a monoclinic fraction exceeding 70%, and the crystallite diameter of the monoclinic zirconia being greater than 23 nm and not greater than 80 nm.

[0066] The powder of this embodiment contains a stabilizer and includes zirconia with a monoclinic fraction exceeding 70%. That is, the powder of this embodiment includes stabilizer-containing zirconia that is primarily composed of monoclinic zirconia. When zirconia powder does not contain a stabilizer, sintering this powder makes it difficult to obtain a sintered body that contains tetragonal zirconia, which is a factor in developing fracture toughness. The powder of this embodiment is a so-called zirconia powder that is primarily composed of zirconia.

[0067] The stabilizer may be one or more selected from the group consisting of calcia (CaO), magnesia (MgO), ceria (CeO2), and yttria (Y2O3), preferably at least one of ceria and yttria, and more preferably yttria. When the stabilizer is yttria, the molar ratio of yttria (yttria content) to the total of zirconia (ZrO2) and yttria (Y2O3) in the powder can be, for example, 1.0 mol% to 2.5 mol%, or even 1.1 mol% to 2.0 mol%, preferably 1.2 mol% to less than 2.0 mol%, and more preferably 1.2 mol% to 1.8 mol%.

[0068] The stabilizer is preferably dissolved in zirconia, and the powder of this embodiment preferably does not contain any undissolved stabilizer.

[0069] Known main crystalline phases of zirconia include monoclinic zirconia, tetragonal zirconia, and cubic zirconia. The zirconia in the powder of this embodiment includes monoclinic zirconia, preferably includes at least one of monoclinic zirconia, tetragonal zirconia, and cubic zirconia, and more preferably includes monoclinic zirconia and tetragonal zirconia.

[0070] The monoclinic ratio of zirconia is more than 70%, preferably 80% or more, and more preferably 85% or more. The monoclinic ratio is 100% or less, and when the zirconia contains at least one of tetragonal zirconia and cubic zirconia, the monoclinic ratio is less than 100%. The tetragonal ratio is 30% or less, more preferably less than 20%, and is preferably 15% or less, and may be 10% or less, or even 7% or less. When the zirconia does not contain tetragonal zirconia, the tetragonal ratio is 0%, and the tetragonal ratio may be 0% or more.

[0071] Monoclinic zirconia crystallite diameter (D mIn another embodiment, the crystal grain size (D m ) may be 30 nm or more and 50 nm or less, further 35 nm or more and 50 nm or less, and may be 35 nm or more and 45 nm or less, further 36 nm or more and 40 nm or less.

[0072] 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. By including the additive component, defects such as cracks are less likely to occur during sintering, even when the content of the zirconia stabilizer is low, and the sintering yield is less likely to decrease. The content of the additive component, expressed as a mass ratio of the additive component to the total mass of the zirconia, yttria, and additive component of the powder, 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.

[0073] The powder of this embodiment preferably does not contain impurities, and for example, the phosphorus (P) content is 0.1 mass % or less and less than 0.1 mass %, respectively. On the other hand, the powder may contain inevitable impurities such as hafnia (HfO2) of zirconia.

[0074] The powder of this embodiment has a BET specific surface area of 6 m 2 / g or more 20m 2 / g. The BET specific surface area is 6m 2 / g or more, sintering can proceed easily at a relatively low temperature. 2 When the BET specific surface area is less than 8 m / g, physical aggregation of the powder tends to be suppressed. 2 / more than 18m2 / g or less, more preferably 10m 2 / g or more 17m 2 / g or less, more preferably 10m 2 / g or more 15m 2 / g or less, and even more preferably 10m 2 / g and over 15m 2 / g or less.

[0075] The powder of this embodiment preferably has a median diameter of 0.05 μm or more and 0.3 μm or less, and more preferably 0.1 μm or more and 0.2 μm or less.

[0076] The powder of this embodiment may have a multimodal volume particle size distribution curve, preferably one with peaks at particle sizes of at least 0.05 μm to 0.2 μm and at more than 0.2 μm to 0.5 μm, and more preferably one with peaks (extreme values) at particle sizes of at least 0.05 μm to 0.2 μm and at more than 0.3 μm to 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. Because the density of the resulting compact tends to be high, the ratio of the peak at particle sizes of 0.3 μm to 0.5 μm in the volume particle size distribution curve (hereinafter also referred to as the "particle size peak ratio") to the peak at particle sizes of 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 0.1 to 0.9, and even more preferably 0.2 to 0.8.

[0077] The powder of this embodiment preferably has high moldability, and when the powder of this embodiment is uniaxially pressed at a pressure of 70±5 MPa and then treated with cold isostatic pressing (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.

[0078] The powder of this embodiment may contain a resin or the like to improve fluidity, or may be a composition (hereinafter also referred to as a "compound") containing the powder of this embodiment and a resin. The resin contained in the compound may be any known resin used in ceramic compositions, such as a thermoplastic resin. Preferred examples of the resin include one or more of the group consisting of acrylic resin, polystyrene, and polyalkyl carbonate, with acrylic resin being preferred.

[0079] The powder content in the compound can be, for example, 50% by mass to 97% by mass, 70% by mass to 95% by mass, or 80% by mass 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 resin can be removed by any method, but examples include heat treatment in air at 200°C to 500°C.

[0080] In addition to resins, the compound may contain additives such as wax. The inclusion of these additives provides additional benefits, such as improved mold releasability. Examples of additives such as wax include polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, polyacetal resin, petroleum wax, synthetic wax, vegetable wax, stearic acid, phthalate ester plasticizer, and adipic acid ester.

[0081] The powder of this embodiment can be used as a precursor for calcined bodies or sintered bodies, and is suitable as a raw material powder for structural materials such as mill members, precision machine parts, and optical connector parts, biomaterials such as dental materials, decorative members, and exterior materials such as electronic device exterior parts.

[0082] When the powder of this embodiment is to be made into a sintered body or the like, the powder may be molded and then calcined or sintered by a known method.

[0083] When the powder of this embodiment is used to form a molded body, molding may be performed by a known method, such as at least one method selected from the group consisting of uniaxial pressing, cold isostatic pressing, slip casting, and injection molding. When a molded body is produced using a resin, such as a compound, the resulting molded body may be heat-treated to remove the resin, as necessary. Heat treatment conditions include, for example, in air at a temperature of 400°C or higher but lower than 800°C.

[0084] The compact may be calcined as needed. The calcination may be performed by heat treatment at a temperature lower than the sintering temperature of the powder, for example, in the air at a temperature of 800° C. or higher but lower than 1200° C. This produces a calcined body.

[0085] Sintering can be performed by any known method, such as one or more selected from the group consisting of pressure sintering, vacuum sintering, and atmospheric sintering. Because it is simple and easy to apply industrially, atmospheric sintering is preferred, with atmospheric sintering in the air at 1200°C to 1550°C, preferably 1250°C to 1500°C, more preferably atmospheric sintering in the air at 1300°C to 1450°C. It is also preferred not to perform any sintering other than atmospheric sintering. The sintering time is optional, but can be, for example, 0.5 hours to 5 hours.

[0086] Next, a method for producing the powder of this embodiment will be described.

[0087] The powder of this embodiment may be produced by any method as long as it has the above-described characteristics. A preferred method for producing the powder of this embodiment includes a step of heat-treating a composition containing a zirconia sol containing zirconia having an average sol particle size of 150 nm to 400 nm and containing monoclinic zirconia, and a stabilizer source, at 950°C to 1250°C to form a calcined powder, and a step of pulverizing the calcined powder.

[0088] A calcined powder, which is a precursor of the powder of this embodiment, is obtained by a process (hereinafter also referred to as the "powder calcination process") in which a composition containing a zirconia sol containing zirconia having an average sol particle size of 150 nm or more and 400 nm or less and containing monoclinic zirconia, and a stabilizer source, is heat-treated at 950°C or more and 1250°C or less to form a calcined powder.

[0089] In the powder calcination process, heat treatment is performed at 950°C to 1250°C, or even 1000°C to 1250°C. Heat treatment at 950°C or higher results in a powder that is easily densified by atmospheric sintering. On the other hand, heat treatment at 1250°C or lower results in a powder that is easily dispersed by pulverization. The heat treatment time varies depending on the heat treatment temperature, but can be, for example, 30 minutes to 2 hours.

[0090] The heat treatment may be carried out in any atmosphere, for example, an oxidizing atmosphere, a reducing atmosphere, an inert atmosphere, or a vacuum atmosphere, preferably an oxidizing atmosphere, and more preferably an air atmosphere.

[0091] The zirconia sol has an average sol particle size of 150 nm to 400 nm, preferably 180 nm to 400 nm, more preferably 185 nm to 300 nm, and may have an average sol particle size of 150 nm to 270 nm, further 150 nm to 200 nm, or 190 nm to 400 nm, or further 200 nm to 300 nm.

[0092] The zirconia sol contains zirconia containing monoclinic zirconia, and is preferably a zirconia sol containing zirconia made of crystalline zirconia (hereinafter also referred to as "crystalline zirconia sol"), and more preferably a zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia.

[0093] Since zirconia sol tends to be easily pulverized, the amount of zirconium element calculated by the following formula (hereinafter also referred to as "adsorbed zirconium amount") 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.

[0094] W Zr =(m / m0)×100 In the above formula, W Zr is the amount of adsorbed zirconium (mass%). m is the mass (mg) of zirconium in the filtrate obtained by ultrafiltration of a slurry in which zirconia sol is dispersed in pure water using an ultrafiltration membrane with a molecular weight cutoff of 500 to 3 million, converted into zirconia (ZrO2). The amount of zirconium in the filtrate can be measured by ICP analysis. m o m and m are the mass (mg) of the zirconia sol before ultrafiltration after heat treatment at 1000°C for 1 hour in an air atmosphere. o The measurements of (a) and (b) can be carried out by preparing the same amount of zirconia sol before ultrafiltration.

[0095] The zirconia sol to be subjected to the powder calcination step may be produced by any method as long as it has the above-mentioned characteristics. Examples of methods for producing the zirconia sol include at least one of a hydrothermal synthesis method and a hydrolysis method. In the hydrothermal synthesis method, a coprecipitate obtained by mixing a zirconium salt with an alkali or the like in the presence of a solvent is heat-treated at 100 to 200°C to obtain the zirconia sol. In the hydrolysis method, a zirconium salt is heated in the presence of a solvent to hydrolyze the zirconium salt, thereby obtaining the zirconia sol. Thus, examples of the zirconia sol include a zirconia sol obtained by a hydrothermal synthesis method or a hydrolysis method, and a zirconia sol obtained by a hydrolysis method is preferred.

[0096] The precursor used in the method for producing a zirconia sol can be a zirconium salt, and examples of the zirconium salt include one or more selected from the group consisting of zirconium oxychloride, zirconyl nitrate, zirconium chloride, and zirconium sulfate. At least one of zirconyl nitrate and zirconium oxychloride is preferred, and zirconium oxychloride is more preferred.

[0097] Hereinafter, the hydrolysis method will be described as an example of a preferred method for producing zirconia sol.

[0098] The hydrolysis conditions may be any conditions under which the hydrolysis of the zirconium salt proceeds sufficiently, and examples thereof include boiling and refluxing the aqueous zirconium salt solution for 130 to 200 hours. When the anion concentration in the aqueous zirconium salt solution is set to 0.2 to 0.6 mol / L, or even 0.3 to 0.6 mol / L, the average sol particle size tends to increase.

[0099] The stabilizer source may be at least one of a stabilizer and a compound that serves as a precursor thereof, and examples thereof include one or more stabilizer precursors selected from the group consisting of oxides, hydroxides, oxyhydroxides, chlorides, acetates, nitrates, and sulfates, with at least one of chlorides and nitrates being preferred. The stabilizer source is preferably at least one of yttria and an yttrium compound that serves as a precursor thereof. Preferred stabilizer sources (hereinafter, stabilizers containing yttria or the like are also referred to as "yttria sources") include at least one selected from the group consisting of yttrium chloride, yttrium nitrate, and yttrium oxide, and further include at least one of yttrium chloride and yttrium oxide. When the stabilizer source is an yttria source, the content of the yttria source in the composition can be, for example, 1.0 mol% or more and 2.5 mol% or less, or even 1.1 mol% or more and 2.0 mol% or less, preferably 1.2 mol% or more and less than 2.0 mol%, and more preferably 1.2 mol% or more and less than 2.0 mol%, and more preferably 1.2 mol% or more and 1.8 mol% or less, as expressed as the molar ratio of the yttria source converted into YO to the sum of the values of zirconium (Zr) and yttrium (Y) in the composition converted into ZrO and YO, respectively.

[0100] The composition to be subjected to the powder calcination step may contain the above-mentioned zirconia sol and a stabilizer source, and all or part of the stabilizer source may be dissolved in the zirconia sol as a solid solution.

[0101] For example, by mixing a zirconium salt and a stabilizer source and hydrolyzing the mixture, or by mixing a zirconium salt, a stabilizer source, and an alkali or the like to form a coprecipitate, at least a portion of the stabilizer source can be easily dissolved in zirconia.

[0102] The composition to be subjected to the powder calcination step may contain one or more additional component sources selected from the group consisting of an alumina source, a germania source, and a silica source. The additional component source is preferably at least one of an alumina source and a germania source, and is preferably an alumina source.

[0103] The alumina source is at least one of alumina and an aluminum compound that serves as a precursor thereof, and examples thereof include one or more selected from the group consisting of alumina, aluminum hydroxide, aluminum nitrate, and aluminum chloride. Alumina is preferred, and at least one of alumina sol and alumina powder is more preferred.

[0104] The germania source is at least one of germania and its precursor germanium compound, and examples thereof include one or more selected from the group consisting of germania, germanium hydroxide, and germanium chloride. Germania is preferred, and at least one of germania sol and germania powder is more preferred.

[0105] The silica source is at least one of silica and a silicon compound that serves as a precursor thereof, and examples thereof include one or more selected from the group consisting of silica and tetraethyl orthosilicate. Silica is preferred, and at least one of silica powder, silica sol, fumed silica, and precipitated silica is more preferred.

[0106] The content of the additive component source is, for example, 0.05% by mass or more and 30% by mass or less, expressed as the total ratio of the mass of Al, Ge, and Si converted into Al2O3, GeO2, and SiO2 relative to the total mass of Zr, Y, and Al, Ge, and Si in the composition converted into ZrO2, Y2O3, and Al2O3, GeO2, and SiO2, respectively, and is 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.

[0107] For example, the content of the alumina source may be 0.05% by mass or more and 30% by mass or less, expressed as the ratio of the mass of the alumina source converted into Al2O3 to the total mass of Zr, Y, and Al in the composition converted into ZrO2, Y2O3, and Al2O3, respectively, and is 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.

[0108] The content of the germania source, expressed as the ratio of the mass of the germania source converted into GeO2 to the total mass of Zr, Y, and Ge in the composition converted into ZrO2, Y2O3, and GeO2, respectively, can be 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 0.2% by mass or more and 20% by mass or less.

[0109] The content of the silica source, expressed as the ratio of the mass of the silica source converted into SiO2 to the total mass of Zr, Y, and Si in the composition converted into ZrO2, Y2O3, and SiO2, respectively, can be from 0.05% by mass to 30% by mass, preferably from more than 0.1% by mass to 25% by mass, and more preferably from 0.2% by mass to 20% by mass.

[0110] The physical properties of the calcined powder are: BET specific surface area 3m 2 / g or more 15m 2 / g or less, and the monoclinic crystallite diameter is 20 nm or more and 60 nm or less.

[0111] In the step of pulverizing the calcined powder (hereinafter also referred to as the "pulverization step"), the calcined powder is pulverized. Zirconia with a low stabilizer content is prone to cracking and chipping during sintering. In contrast, by pulverizing the calcined powder in this embodiment, the yield during sintering tends to be higher, and the resulting sintered body tends to be less susceptible to hydrothermal degradation.

[0112] To obtain a powder of the desired composition, a mixed powder of the calcined powder, the alumina source, and the additive component source may be milled in the milling step instead of the calcined powder. Examples of the additive component source include the additive component sources described above. When the additive component source is mixed in the milling step, the additive component source and the calcined powder are mixed so that the total mass ratio of Al converted to Al2O3, Ge converted to GeO2, and Si converted to 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 0.2% by mass or more and 20% by mass or less, relative to the total mass of Zr, Y, and one or more selected from the group consisting of Al, Ge, and Si converted to ZrO2, Y2O3, Al2O3, GeO2, and SiO2 in the mixed powder.

[0113] The pulverization method may be any method, as long as it is at least one of wet pulverization and dry pulverization, with wet pulverization being preferred. Specific examples of wet pulverization include one or more selected from the group consisting of a ball mill, a vibration mill, and a continuous media stirring mill, with a ball mill being preferred. Pulverization conditions using a ball mill include, for example, mixing the calcined powder with a solvent to form a slurry in which the mass ratio of the calcined powder to the slurry mass is 30% by mass or more and 60% by mass or less, and pulverizing the slurry for 10 hours or more and 100 hours or less using zirconia balls with a diameter of 1 mm or more and 15 mm or less as milling media.

[0114] After wet grinding, the powder may be obtained by drying using any method, for example, in air at 110°C to 130°C.

[0115] In order to improve the workability of the powder, the method for producing a powder according to this embodiment may include a step of granulating the powder (hereinafter also referred to as a "granulation step"). Granulation may be performed by any method, but examples include spray granulation of a slurry in which the powder is mixed 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 diameter of 30 μm or more and 80 μm or less, and preferably 50 μm or more and 60 μm or less, and a bulk density of 1.00 g / cm. 3 More than 1.40g / cm 3 Below that, 1.10 g / cm 3 More than 1.30g / cm 3 The following points can be mentioned. [Example]

[0116] The present disclosure will be described below using examples, but the present disclosure is not limited to these examples. (average sol particle size) The average particle size of the zirconia sol was measured using a dynamic light scattering particle size distribution analyzer (model: UPA-UT151, manufactured by Microtrack-Bell). As a sample pretreatment, the hydrated zirconia sol solution was suspended in pure water and dispersed for 3 minutes using an ultrasonic homogenizer. (monoclinic crystal ratio, tetragonal crystal ratio, D t and D m ) An XRD pattern of the powder sample was obtained using a general X-ray diffractometer (product name: Ultima II V, manufactured by Rigaku Corporation) under the following conditions for XRD measurement.

[0117] Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=26°~33°

[0118] Using the obtained XRD pattern and the calculation program "PRO-FIT", the monoclinic crystal ratio, tetragonal crystal ratio, and D were calculated using equations (1), (2), (4), and (5), respectively. t and D m asked for. (BET specific surface area) The BET specific surface area of the powder sample was measured using a general flow-type automatic specific surface area measuring device (Device name: FlowSorb III2305, manufactured by Shimadzu Corporation) and nitrogen as the adsorption gas according to a method in accordance with JIS R 1626-1996. Prior to the measurement, the powder sample was pretreated by degassing in air at 250°C for 30 minutes. (Particle size distribution measurement) The volume particle size distribution curve of the powder sample was measured using the HRA mode of a Microtrac particle size distribution analyzer (product name: MT3000II, manufactured by Microtrac Bell Co., Ltd.) to determine the median diameter. Prior to the measurement, the powder sample was suspended in pure water and dispersed for 10 minutes using an ultrasonic homogenizer as pretreatment. (Molded object density) The mass of the compact sample was measured with a balance, and the volume was measured with calipers to determine the dimensions. The measured density was calculated from the obtained mass and volume. The theoretical density was calculated using equations (5) to (8), and the relative density (%) was calculated from the value of the measured density (ρ) relative to the theoretical density (ρ0), which was used as the compact density.

[0119] (Monoclinic crystal ratio and monoclinic crystal intensity ratio of sintered body) The sintered samples were subjected to XRD measurement under the same conditions as those for the powder samples. Using the obtained XRD patterns and the calculation program "PRO-FIT," the monoclinic fraction and monoclinic intensity ratio were calculated using equations (1) and (3), respectively.

[0120] For XRD measurements, the sintered samples were polished to a surface roughness (Ra) of 0.04 μm or less by grinding the surface with a surface grinder, followed by automatic polishing with waterproof paper (#800), automatic polishing with diamond slurry with an average particle size of 3 μm, and automatic polishing with colloidal silica with a particle size of 0.03 μm, in that order. An automatic polishing machine (MECATECH 334, manufactured by PRESI) was used for the automatic polishing. (sintered body density) The actual density of the sintered body samples was measured by 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 using equations (5) to (8), and the relative density (%) was calculated from the value of the actual density (ρ) relative to the theoretical density (ρ0), which was used as the sintered body density.

[0121] (Average grain size) The average grain size was determined by the planimetric method using SEM images of sintered samples obtained by field emission scanning electron microscope observation. That is, a circle of known area was drawn on the SEM image, and the number of grains within the circle (Nc) and the number of grains on the circumference of the circle (Ni) were counted.

[0122] The total number of crystal grains (Nc+Ni) was set to 250±50, and the average crystal grain size was calculated using the following formula.

[0123] Average grain size=(Nc+(1 / 2)×Ni) / (A / M 2 ) In the above formula, Nc is the number of crystal particles within the circle, Ni is the number of crystal particles on the circumference of the circle, A is the area of the circle, and M is the magnification of the scanning electron microscope observation (5000x). When the number of crystal particles (Nc + Ni) in one SEM observation image was less than 200, (Nc + Ni) was set to 250 ± 50 using multiple SEM observation images.

[0124] Prior to the measurement, the sintered body samples were pretreated by mirror polishing and thermal etching. For mirror polishing, the surface of the sintered body was ground using a surface grinder, and then polished using diamond abrasive grains with average grain sizes of 9 μm, 6 μm, and 1 μm in a mirror polishing machine.

[0125] (Fracture toughness value) The fracture toughness value of the sintered compact samples was measured in accordance with the SEPB method specified in JIS R 1607. Measurements were carried out using columnar sintered compact samples with a support distance of 30 mm, width of 4 mm, and thickness of 3 mm, and the average value of 10 measurements was taken as the fracture toughness value.

[0126] (bending strength) The bending strength of the sintered body samples was measured by a three-point bending test in accordance with JIS R 1601. The measurement was carried out 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 bending strength was calculated as the average value of 10 measurements. (Total light transmittance) The total light transmittance was measured using a spectrophotometer (device name: V-650, manufactured by JASCO Corporation) according to a method in accordance with JIS K 7361. A disk-shaped sample was used for the measurement. Prior to the measurement, both sides of the sample were polished to a thickness of 1 mm and a surface roughness (Ra) of 0.02 μm or less. Light with wavelengths of 220 to 850 nm was transmitted through the sample and collected using an integrating sphere to measure the transmittance at each wavelength, and the transmittance at a wavelength of 600 nm was taken as the total light transmittance.

[0127] Example 1 An aqueous solution of zirconium oxychloride with a zirconium concentration and a chloride ion concentration of 0.4 mol / L 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 was below the detection limit (0.01% by mass or less).

[0128] After ultrafiltration, yttrium chloride hexahydrate and an aqueous ammonia solution were added to the zirconia sol solution so that the yttria content was 1.6 mol%, to obtain a precipitate. The obtained precipitate was washed with pure water, dried in the air, and then calcined in the air at a calcination temperature of 1025°C for 2 hours to obtain a calcined powder. The BET specific surface area of the obtained calcined powder was 12.5 m 2 / g, and the monoclinic crystallite size was 35 nm.

[0129] The calcined powder was mixed with pure water to form a slurry, which was then ball milled using zirconia balls and dried at 120°C in air to obtain a powder consisting of yttria-containing zirconia with an yttria content of 1.6 mol%, which was designated the powder of this example. In this powder, all of the yttria was dissolved in 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.

[0130] The powder of this example was molded under a pressure of 70 MPa and subjected to CIP treatment under a pressure of 196 MPa to form a compact, which was then sintered under atmospheric pressure at a sintering temperature of 1300°C for 2 hours in the air to obtain a sintered body.

[0131] Example 2 A powder containing 0.25% by mass of alumina in terms of Al2O3, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 0.25% by mass of alumina sol in terms of Al2O3 was subjected to ball milling. The median diameter of the powder in this 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, and the particle size peak ratio was 0.37.

[0132] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1250°C.

[0133] Example 3 A powder containing 0.25% by mass of alumina in terms of Al2O3, the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that the calcination temperature was set to 1130°C and a mixed powder of the calcined powder and 0.25% by mass of alumina sol in terms of Al2O3 was subjected to a ball milling treatment.

[0134] The BET specific surface area of the calcined powder obtained was 6.7m 2 The powder of this example had a median diameter of 0.18 μm, a bimodal volume particle size distribution curve with peaks at particle sizes of 0.14 μm and 0.36 μm, and a particle size peak ratio of 0.85.

[0135] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used.

[0136] Reference example 1 A powder containing 0.25 mass% alumina in terms of Al2O3 and the remainder being 2 mol% yttria-containing zirconia was obtained in the same manner as in Example 1, except that yttrium chloride hexahydrate was added to the ultrafiltered zirconia sol solution so that the yttria content was 2 mol%, and a mixed powder of the calcined powder and 0.25 mass% alumina sol in terms of Al2O3 was ball milled. The median diameter of the powder in this 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, and the particle size peak ratio was 0.33.

[0137] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1500°C.

[0138] Example 5 A powder containing 20% by mass of alumina in terms of Al2O3, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 20% by mass of alumina powder calculated as Al2O3 was subjected to ball milling. The median diameter of the powder in this 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. The crystallite diameter (D t ) was 42 nm.

[0139] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1350°C.

[0140] Example 6 A powder containing 20% by mass of alumina in terms of Al2O3 and the remainder being 1.6 mol% yttria-containing zirconia was obtained in the same manner as in Example 1, except that the calcination temperature was set to 1130°C and a mixed powder of the calcined powder and 20% by mass of alumina powder in terms of Al2O3 was subjected to ball milling. The median diameter of the powder in this 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, and the particle size peak ratio was 0.67.

[0141] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1400°C.

[0142] Reference example 2 A powder containing 5% by mass of alumina in terms of Al2O3 and the remainder being 2 mol% yttria-containing zirconia was obtained in the same manner as in Example 1, except that yttrium chloride hexahydrate was added to the ultrafiltered zirconia sol solution so that the yttria content was 2 mol%, and a mixed powder of the calcined powder and 5% by mass of alumina sol in terms of Al2O3 was ball milled. The median diameter of the powder in this 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, and the particle size peak ratio was 0.41.

[0143] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1500°C.

[0144] Example 8 A powder containing 0.5% by mass of alumina in terms of Al2O3, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 0.5% by mass of alumina sol in terms of Al2O3 was subjected to ball milling. The median diameter of the powder in this 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, and the particle size peak ratio was 0.49.

[0145] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1250°C.

[0146] Example 9 A powder containing 1% by mass of alumina in terms of Al2O3, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 1% by mass of alumina sol in terms of Al2O3 was subjected to ball milling. The median diameter of the powder in this 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, and the particle size peak ratio was 0.49.

[0147] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1250°C.

[0148] Example 10 A powder containing 0.25% by mass of germanium oxide in GeO2 equivalent, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 0.25% by mass of germanium oxide in GeO2 equivalent was subjected to ball milling. The median diameter of the powder in this example was 0.14 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, and the particle size peak ratio was 0.37.

[0149] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1250°C.

[0150] Example 11 A powder containing 0.25% by mass of silica in terms of SiO2, with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder and 0.25% by mass of silica sol in terms of SiO2 was subjected to ball milling. The median diameter of the powder in this 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, and the particle size peak ratio was 0.89.

[0151] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1350°C.

[0152] Example 12 A powder containing 0.25 mass% alumina (calculated as Al2O3) and 0.25 mass% germanium oxide (calculated as GeO2), with the remainder being 1.6 mol% yttria-containing zirconia, was obtained in the same manner as in Example 1, except that a mixed powder of the calcined powder, 0.25 mass% alumina sol (calculated as Al2O3) and 0.25 mass% germanium oxide (calculated as GeO2) was ball milled. The median diameter of the powder in this 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.

[0153] A green body and a sintered body were obtained in the same manner as in Example 1, except that the powder was used and the sintering temperature was set to 1200°C.

[0154] Comparative Example 1 An aqueous solution of zirconium oxychloride with a zirconium concentration of 0.37 mol / L and a chloride ion concentration of 0.74 mol / L, respectively, 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 100 nm. Zr was 9% by mass.

[0155] After ultrafiltration, yttrium chloride hexahydrate and an aqueous ammonia solution were added to the zirconia sol solution so that the yttria content was 2 mol%, to obtain a precipitate. The obtained precipitate was washed with pure water, dried in the air, and then calcined in the air at a calcination temperature of 1000°C for 2 hours to obtain a calcined powder.

[0156] The calcined powder was mixed with pure water to form a slurry, which was then ball milled using zirconia balls and dried at 120°C in the air 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 example.

[0157] The powder of this comparative example was molded under a pressure of 70 MPa and subjected to CIP treatment under a pressure of 196 MPa to form a compact, which was then sintered under atmospheric pressure at a sintering temperature of 1450°C for 2 hours in the air to obtain a sintered body.

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

[0159] A green body and a sintered body were obtained in the same manner as in Comparative Example 1, except that the powder was used.

[0160] Comparative Example 3 A powder containing 5% by mass of alumina in terms of Al2O3 and the remainder being 2 mol% yttria-containing zirconia was obtained in the same manner as in Comparative Example 1, except that a mixed powder of the calcined powder and 5% by mass of alumina powder in terms of Al2O3 was subjected to ball milling.

[0161] A green body and a sintered body were obtained in the same manner as in Comparative Example 1, except that the powder was used.

[0162] Comparative Example 4 A powder consisting of zirconia containing 0.5 mol% yttria was obtained in the same manner as in Example 1, except that yttrium chloride hexahydrate and an aqueous ammonia solution were added to the zirconia sol aqueous solution after ultrafiltration so that the yttria content was 0.9 mol% to obtain a precipitate.

[0163] The powder was molded under a pressure of 70 MPa and then subjected to CIP treatment under a pressure of 196 MPa to produce a compact. The resulting compact was then sintered under atmospheric pressure at a sintering temperature of 1300°C for 2 hours to produce a sintered body. However, the density was low and numerous cracks occurred, making it impossible to evaluate the properties of the sintered body.

[0164] The evaluation results of the powders of these Examples and Comparative Examples are shown in Table 1, and the evaluation results of the sintered bodies are shown in Table 2.

[0165] [Table 1]

[0166] From the above table, it can be seen that the powders of the Examples and Comparative Examples 1 to 3 have the same stabilizer content (yttria content) and additive content, but the powders of Comparative Examples 1 to 3 have the same stabilizer content (yttria content) and additive content. m Furthermore, it can be seen that the D m It can be seen that is small.

[0167] [Table 2]

[0168] From the above table, it can be seen that the compact density was 49% or more, even 50% or more, for the Examples, and less than 49%, even less than 48% for the Comparative Examples, and that the powders of the Examples have high packing properties. On the other hand, the sintered density of the sintered bodies with a stabilizer content of 1.0 mol% or more was similar for both the Examples and the Comparative Examples, but the fracture toughness value of the Examples was 6.5 MPa m 0.5 or more, whereas the fracture toughness value of the comparative example was 6 MPa m 0.5 This indicates that a sintered body with high fracture toughness can be obtained from the powder of this example by atmospheric sintering. The sintered body of Comparative Example 1 does not have an XRD peak corresponding to the (111) plane of monoclinic zirconia, so the monoclinic intensity ratio could not be calculated. Furthermore, the sintered body of Comparative Example 4 contains a large number of defects such as cracks, and the sintered body collapses during processing into a measurement sample, such as mirror polishing, so measurements other than the sintered body density were not possible.

[0169] The fracture toughness of the sintered bodies of Examples 1 and 5 was measured by the IF method specified in JIS R1607. The fracture toughness measured by the IF method was 17.9 MPa m 1 / 5 and 11.1 MPa·m 1 / 5Although the degree of increase in fracture toughness measured by the IF method and the SEPB method differed, the fracture toughness measured by the IF method was higher than that measured by the SEPB method in both cases.

[0170] Example 13 A powder was obtained in the same manner as in Example 1. A sintered body was obtained in the same manner as in Example 1, except that the obtained powder was used and the sintering temperature was set to 1400°C.

[0171] Example 14 A powder was obtained in the same manner as in Example 2. A sintered body was obtained in the same manner as in Example 2, except that the obtained powder was used and the sintering temperature was set to 1350°C.

[0172] Example 15 A powder was obtained in the same manner as in Example 3. A sintered body was obtained in the same manner as in Example 3, except that the obtained powder was used and the sintering temperature was set to 1400°C.

[0173] Example 16 A powder was obtained in the same manner as in Example 5. A sintered body was obtained in the same manner as in Example 5, except that the obtained powder was used and the sintering temperature was set to 1500°C.

[0174] Example 17 A powder was obtained in the same manner as in Example 6. A sintered body was obtained in the same manner as in Example 6, except that the obtained powder was used and the sintering temperature was set to 1500°C.

[0175] Example 18 A powder was obtained in the same manner as in Example 8. A sintered body was obtained in the same manner as in Example 8, except that the obtained powder was used and the sintering temperature was set to 1350°C.

[0176] Example 19 A powder was obtained in the same manner as in Example 9. A sintered body was obtained in the same manner as in Example 9, except that the obtained powder was used and the sintering temperature was set to 1350°C.

[0177] Example 20 A powder was obtained in the same manner as in Example 10. A sintered body was obtained in the same manner as in Example 10, except that the obtained powder was used and the sintering temperature was set to 1350°C.

[0178] Example 21 A powder was obtained in the same manner as in Example 12. A sintered body was obtained in the same manner as in Example 12, except that the obtained powder was used and the sintering temperature was set to 1250°C.

[0179] Example 22 A powder was obtained in the same manner as in Example 12. A sintered body was obtained in the same manner as in Example 12, except that the obtained powder was used and the sintering temperature was set to 1350°C.

[0180] Comparative Example 5 A powder was obtained in the same manner as in Comparative Example 1. A sintered body was obtained in the same manner as in Comparative Example 1, except that the obtained powder was used and the sintering temperature was set to 1500°C.

[0181] [Table 3]

[0182] The sintered body of the example has a fracture toughness of 7 MPa m measured by the SEPB method. 0.5 That was all.

[0183] Measurement example 1 (hydrothermal degradation test) A sintered body was obtained in the same manner as in Example 2, mirror-polished, and then subjected to a hydrothermal degradation test by immersing it in hot water at 140°C. The monoclinic crystal ratio of the sintered body surface was determined after 6 and 10 hours of immersion. As a comparative measurement example, a zirconia sintered body containing 3 mol% yttria was treated and evaluated in the same manner. The results are shown in the table below.

[0184] The sintered body of the comparative example was produced by molding a powder of zirconia containing 3 mol% yttria, obtained in the same manner as in Comparative Example 1, except that yttrium chloride hexahydrate was added to the ultrafiltered zirconia sol solution so that the yttria content was 3 mol%. This powder was then molded using a die press at a pressure of 70 MPa and subjected to CIP treatment at a pressure of 196 MPa, and then pressureless sintering was carried out in air at a sintering temperature of 1500°C for 2 hours. The fracture toughness value of the sintered body of the comparative example was 4.8 MPa m 0.5 It was.

[0185] [Table 4]

[0186] Before the hydrothermal degradation test, the sintered body in both the measurement example and the comparative measurement example had tetragonal zirconia as the main crystalline phase. The hydrothermal degradation test caused the sintered body to deteriorate due to a phase transition from tetragonal zirconia to monoclinic zirconia. Compared to the comparative measurement example, the measurement example had a lower stabilizer content, yet the monoclinic fraction after the hydrothermal degradation test was low, demonstrating that the sintered body was less susceptible to degradation. Furthermore, before the hydrothermal degradation test, the sintered body in the comparative measurement example had a monoclinic fraction of 0% and a tetragonal fraction of 70%, with the remainder being cubic, resulting in a residual tetragonal fraction (△T%) of 4%. It is believed that after the 10-hour hydrothermal degradation test, almost all of the tetragonal zirconia in the sintered body underwent a phase transition to monoclinic zirconia. In contrast, the sintered body in the measurement example before the hydrothermal degradation test had a tetragonal crystal ratio of 94% and a monoclinic crystal ratio of 6%, so the remaining tetragonal crystal ratio (△T%) was 85%. Furthermore, it is thought that even after the 10-hour hydrothermal degradation test, it still contained a large amount of tetragonal zirconia that did not undergo phase transition.

[0187] Measurement example 2 (residual tetragonal crystal ratio) The sintered bodies of Examples 1 and 13 and Comparative Examples 1 and 5 were mirror-polished and then immersed in hot water at 140°C for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the table below.

[0188] [Table 5]

[0189] The residual tetragonal crystal ratio of the sintered bodies of the Examples was 65% or more, and it was found that the transformation from tetragonal zirconia to monoclinic zirconia was less likely to occur than in the Comparative Examples, which had a higher stabilizer content.

[0190] Measurement example 3 (residual tetragonal crystal ratio) The sintered bodies of Examples 2 to 4, 14 and 15 and Comparative Example 2 were mirror-polished and then immersed in hot water at 140° C. for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the table below.

[0191] [Table 6]

[0192] The residual tetragonal ratio of the sintered bodies of the Examples was 65% or more, indicating that the transformation from tetragonal zirconia to monoclinic zirconia was less likely to occur than in the Comparative Examples. Furthermore, Reference Example 1 had the same stabilizer content as Comparative Example 2, and despite the higher sintering temperature, it also showed a higher residual tetragonal ratio.

[0193] Measurement example 4 (residual tetragonal crystal ratio) The sintered bodies of Examples 5 to 12, 16 to 22 and Comparative Example 3 were mirror-polished and then immersed in hot water at 140° C. for 6 hours to determine the residual tetragonal crystal ratio. The results are shown in the table below.

[0194] [Table 7]

[0195] The sintered bodies of the examples have a residual tetragonal ratio of 70% or more, which indicates that the transformation from tetragonal zirconia to monoclinic zirconia is less likely to occur compared to the comparative examples. The sintered body of Example 22 contains a total of 0.5% by mass of alumina and germania as additive components. It can be seen that the sintered body of Example 22 exhibits a residual tetragonal ratio despite being obtained by sintering at a higher temperature than the sintered body of Example 6, which contains 20% by mass of alumina.

[0196] Furthermore, from Examples 1, 3 and 6 (and Examples 5, 18 and 19) in which the sintering temperature and stabilizer content were the same, there was a tendency that the residual tetragonal crystal ratio increased as the content of the added component (alumina) increased.

[0197] Measurement example 5 (total light transmittance) The total light transmittance was measured using the sintered bodies of Examples 2, 8, 9 and 14, and Comparative Example 2. The results are shown in the table below.

[0198] [Table 8]

[0199] Although the sintered bodies of the Examples all contained 0.2 mass% or more of the added components, the total light transmittance was 25% or more and 40% or less. Furthermore, in Examples 2 and 14, the total light transmittance increased with increasing sintering temperature. In contrast, the sintered body of Comparative Example 2 had a total light transmittance of less than 20% despite the higher sintering temperature.

[0200] Furthermore, the sintered body of Example 2 was processed to a thickness of 0.2 mm, and the total light transmittance was measured in the same manner. As a result, the total light transmittance at a thickness of 0.2 mm was 46%. However, when an attempt was made to process the sintered body of Comparative Example 2 in the same manner, the sintered body cracked during processing, and it was not possible to obtain a measurement sample with a thickness of 0.2 mm or less.

[0201] Measurement example 6 (linear transmittance) The sintered bodies of the examples were each processed to a thickness of 0.09 mm. All samples were processed to a thickness of 0.09 mm without cracks or other defects. However, the sintered bodies of the comparative examples could not even be processed to a thickness of 0.2 mm because defects such as cracks and breaks occurred during processing.

[0202] The linear transmittance was measured for sintered bodies with a sample thickness of 0.09 mm. The linear transmittance values for the main examples are shown in the table below.

[0203] [Table 9]

[0204] It can be seen from Examples 2, 3, and 14 that the linear transmittance decreases as the sintering temperature increases. It can also be seen that the sintered body of Example 1, which does not contain alumina, has a high linear transmittance, while the sintered body of Example 8 has a low linear transmittance, compared to Example 3. Furthermore, a comparison of Examples 11, 14, 20, and 21 shows that the linear transmittance varies depending on the type of additive.

[0205] Measurement example 7 (compound evaluation) Compounds were prepared using the powders of Examples 2 and 3. Specifically, the powders were dried at 150°C for at least 1 hour, and then the powders and acrylic resin were added to a kneader (Labo Kneader Mill TDR-3, manufactured by Toshin Co., Ltd.) so that the powder mass relative to the mass of the resulting compound was 85% by mass. The compounds were then kneaded at 160°C to obtain the compounds. The torque (N·m) applied to the kneader was measured 15 minutes after the start of kneading to evaluate the compound's kneadability. The smaller the torque value, the easier the compound was to knead, i.e., the better the compound's kneadability.

[0206] The fluidity was evaluated by measuring the flow rate of the compound sample using a flow tester. A general 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 volumetric velocity (cm ) of the compound injected from the syringe was measured. 3 The fluidity was confirmed by measuring the volume velocity (volume velocity / s). The measurement conditions are as follows. The higher the volume velocity, the easier the compound flows in a molten state, i.e., the better the fluidity of the compound.

[0207] Syringe area: 1cm 2 Die hole diameter: 1mm Die length: 2mm Load: 50kg Measurement temperature: 160℃ Compound density: 3.0g / cm 3 In addition, as a comparative measurement example, the BET specific surface area is 15.0m 2 A zirconia powder containing 3 mol% yttria, with a porosity of 1.1 μm / g and an average particle size (median diameter) of 1.1 μm, was similarly evaluated. The evaluation results of the compound are shown in the table below. The powder of the comparative measurement example had poor kneadability and could not be kneaded at 160°C. Therefore, the kneadability of the comparative measurement example in the table below shows the value when kneaded at 170°C.

[0208] [Table 10]

[0209] Compared to the powder of the Comparative Example, the powder of Example 3, which had a lower BET specific surface area, was excellent in both kneadability and fluidity, with the fluidity being particularly remarkably high. Furthermore, although the powders of Example 2 and Comparative Example had similar BET specific surface areas, the fluidity of the powder of Example 2 was significantly higher than that of the powder of Comparative Example. These results demonstrate that the powders of the Examples also have excellent effects as compositions (compounds) consisting of powder and resin.

Claims

1. A sintered body comprising zirconia containing one or more stabilizers selected from the group consisting of yttria, calcia, magnesia, and ceria, wherein the stabilizer content is 1.0 mol% or more and 1.8 mol% or less, 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 zirconia crystal phase is 0 or more, the monoclinic fraction is 0.5% or more, the relative density is 99% or more and 100% or less, and the average crystal grain size is 0.1 μm or more and 0.8 μm or less.

2. 2. The sintered body according to claim 1, wherein the monoclinic ratio is 5.7% or more.

3. 3. The sintered body according to claim 1, wherein the stabilizer is yttria.

4. 4. The sintered body according to claim 1, wherein the content of the stabilizer is 1.5 mol % or more and 1.8 mol % or less.

5. The fracture toughness measured by the SEPB method specified in JIS R1607 is 6 MPa m ０．５ 11MPa・m or more ０．５ The sintered body according to any one of claims 1 to 4, wherein:

6. 6. The sintered body according to claim 1, further comprising one or more additive components selected from the group consisting of alumina, germania, and silica.

7. 7. The sintered body according to claim 6, wherein the additive component is alumina.

8. The sintered body according to any one of claims 1 to 7, wherein the zirconia contains monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia.

9. 9. The sintered body according to claim 1, wherein the ratio of the tetragonal crystal fraction after immersion treatment in hot water at 140°C for 6 hours to the tetragonal crystal fraction before immersion treatment in hot water at 140°C for 6 hours is 15% or more.

10. A member comprising the sintered body according to any one of claims 1 to 9.

Images