Powder

Abstract

Provided is at least one of a powder and a method for producing the same, the powder being capable of obtaining a zirconia sintered body which contains manganese as the main coloring element, is black, and has high fracture toughness, and which has small hue fluctuations due to fluctuations in sintering temperature. This powder contains zirconium oxide containing yttrium as a stabilizing element, a manganese compound, and aluminum oxide, and the content of the stabilizing element in terms of oxide is 1.3 mol% or more but less than 2.0 mol% with respect to the total amount of the stabilizing element in terms of oxide. The content of the aluminum oxide is 0.2-1.5% by mass (inclusive) with respect to the total amount of the powder, and the content of the manganese compound is 0.1-0.6% by mass (inclusive) with respect to the total amount of the powder.

Description

Technical Field

[0001] The present invention relates to a powder as a precursor of a sintered body of zirconia that is black, and a method for manufacturing a sintered body using the powder. Background Art

[0002] Sintered bodies of zirconia are widely used in decorative parts, outer packaging parts, semiconductor parts, structural parts, etc. A sintered body of zirconia that is black has a glossy feeling and can give a high-class impression, and thus is used as a highly decorative member. When used as a member, in addition to the decorativeness, it is also required to be less likely to be damaged. Therefore, research is being conducted on a sintered body of zirconia, a so-called high-toughness zirconia sintered body, in which yttrium is contained as a stabilizing element and its content is reduced to improve the fracture toughness.

[0003] As a black high-toughness zirconia sintered body, for example, a powder of zirconia is disclosed, wherein the zirconia is yttrium-stabilized zirconia having a yttrium oxide content of about 2 mol%, and the zirconia contains alumina and a coloring element (see Patent Document 1). Patent Document 1 discloses the use of Fe, Ti, Co, and Cr as coloring elements.

[0004] In addition, Patent Document 2 discloses: a powder of zirconia using a cheaper manganese as a coloring element, including 1.6 mol% of yttrium oxide as a stabilizer, 0.25% by mass of alumina, and 0.05% by mass of MnO2, and a sintered body obtained therefrom. Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2022-34289 Patent Document 2: International Publication No. 2022 / 075346 Summary of the Invention Technical Problem to be Solved by the Invention

[0006] The sintered body of Patent Document 1 requires multiple elements as coloring elements, so the manufacturing cost tends to be high. On the other hand, the sintered body of Patent Document 2 has a light color tone and is not a black sintered body.

[0007] An object of the present disclosure is to provide at least one of a powder and a method for manufacturing the same, which can obtain a sintered body of zirconia that has manganese as a main coloring element, is black, has high fracture toughness, and has little fluctuation in color tone caused by changes in sintering temperature. Technical Solution for Solving the Technical Problem

[0008] The present inventors have studied a high-toughness zirconia sintered body that contains manganese as a main coloring element and is black. As a result, it was confirmed that in a high-toughness zirconia sintered body, if the content of the coloring element is increased, defects such as cracking occur during sintering, and the sintered body itself cannot be obtained. Moreover, it was confirmed that even when a sintered body is obtained, the hue of the sintered body containing manganese as a main coloring element fluctuates in each manufacturing batch. Regarding this fluctuation, it was found that the actual sintering temperature such as temperature unevenness in the sintering furnace, rather than the set temperature of the sintering furnace, has an impact. Based on these insights, the present inventors have found that by including alumina that functions as a white coloring element and controlling the contents of alumina and the manganese compound to a specific relationship, even in a high-toughness zirconia sintered body that contains manganese as a main coloring element and is black, the fluctuation in hue caused by changes in the sintering temperature becomes smaller.

[0009] That is, as described in the disclosure of the patent claim, in addition, the gist of the present disclosure is as follows.

[0010] [1] A powder, characterized in that the powder contains zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina, the content of the stabilizing element in terms of oxide is 1.3 mol% or more and less than 2.0 mol% relative to the total amount of zirconia and the stabilizing element in terms of oxide, the content of the alumina is 0.2 mass% or more and 1.5 mass% or less relative to the total amount of the powder, the content of the manganese compound is 0.1 mass% or more and 0.6 mass% or less relative to the total amount of the powder.

[0011] [2] The powder according to [1], wherein the powder contains zirconia with a monoclinic ratio greater than 70%, and the crystallite diameter of monoclinic zirconia is greater than 23 nm and 80 nm or less, the BET specific surface area of the powder is 25 m 2 / g or less.

[0012] [3] The powder according to [1] or [2], wherein the manganese compound is one or more selected from manganese oxide, manganese dioxide, manganese sesquioxide, and manganese tetroxide.

[0013] [4] The powder according to any one of [1] to [3], wherein the alumina is at least one of a sol of alumina and a powder of alumina.

[0014] [5] The powder according to any one of [1] to [4], wherein the mass ratio of the alumina in terms of Al2O3 to the manganese compound in terms of Mn3O4 is 0.1 or more.

[0015] [6] The powder according to any one of [1] to [5], wherein the crystal phase of zirconia includes monoclinic zirconia and tetragonal zirconia.

[0016] [7] The powder according to [6], wherein the ratio of the microcrystalline diameter of monoclinic zirconia to the microcrystalline diameter of tetragonal zirconia is 0.7 or more and 1.2 or less.

[0017] [8] The powder according to any one of [1] to [7], wherein the median particle size of the powder is 0.1 μm or more and 1.0 μm or less.

[0018] [9] The powder according to any one of [1] to [8], wherein the volume particle size distribution curve of the powder is a multimodal distribution.

[0019]

[10] The powder according to any one of [1] to [9], wherein after filling 3 ± 0.3 g of the powder into a mold with a diameter of 25 mm and repeatedly performing uniaxial pressing at a pressure of 70 ± 5 MPa and CIP treatment at a pressure of 196 ± 5 MPa to form 5 compacts, the holding time at the sintering temperature in an atmospheric atmosphere with a heating rate of 100 °C / hour is set to 2 hours, and when performing normal pressure sintering on 1 compact at each of the sintering temperatures of 1200 °C, 1250 °C, 1300 °C, 1350 °C, and 1400 °C, the difference between the maximum value and the minimum value of the brightness L * of the 5 sintered compacts obtained is 1.4 or less.

[0020]

[11] A method for manufacturing a sintered compact, which includes a step of performing normal pressure sintering on a compact containing the powder according to any one of [1] to

[10] at a temperature of 1200 °C or more and 1400 °C or less. Advantages of the Invention

[0021] According to the present disclosure, it is possible to provide at least one of a powder and a method for manufacturing the same, the powder capable of obtaining a sintered compact of zirconia that has manganese as a main coloring element, is black, and has high fracture toughness, and the sintered compact has little fluctuation in hue caused by changes in the sintering temperature. Detailed Embodiments

[0022] Hereinafter, an example of an embodiment of the present disclosure will be described. In addition, in the present disclosure, any combination of the respective structures and parameters disclosed in this specification is included. Further, a range of any combination of the upper and lower limits of the values disclosed in this specification is also included in the present disclosure. The main terms in this embodiment are as follows. The "monoclinic ratio" and the "tetragonal ratio" are the ratios of monoclinic zirconia and tetragonal zirconia, respectively, in the crystal phase of zirconia. In addition, 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 crystal phase of zirconia.

[0023] Regarding the powder, a powder X-ray diffraction (hereinafter also referred to as "XRD") pattern of the powder is used. On the other hand, regarding the sintered body, an XRD pattern of the surface of the sintered body after mirror polishing is used. The monoclinic ratio can be obtained by the following formula (1), the tetragonal ratio can be obtained by the following formula (2), and the monoclinic intensity ratio can be obtained by the following formula (3), respectively.

[0024] f m ={I m (111)+I m (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)

[0025] In formulas (1) to (3), f m is the monoclinic ratio (%), f t is the tetragonal 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) plane and the (11-1) plane of monoclinic zirconia, respectively, I t (111) is the area intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia, and Ic (111) is the area intensity of the XRD peak corresponding to the (111) plane of cubic zirconia. Therefore, the monoclinic ratio and tetragonal ratio are obtained as area intensity ratios (%).

[0026] The conditions for the measurement of the XRD pattern may be the following conditions. X-ray source: CuKα ray (λ = 0.15418 nm) Measurement mode: continuous scan Scanning speed: 4° / min Step size: 0.02° Measurement range: 2θ = 26° to 33°

[0027] In the above XRD pattern measurement, the XRD peaks corresponding to the respective crystal planes of zirconia are measured as peaks having a peak top at the following 2θ. XRD peak corresponding to the (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° XRD peak corresponding to the (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° The XRD peaks corresponding to the (111) planes of tetragonal zirconia and cubic zirconia are repeated and measured, and the 2θ of the peak top thereof is 2θ = 30 ± 0.5°. Therefore, the area intensity corresponding to "I t (111)+I c (111)" in formulas (1) and (2) is obtained as one value.

[0028] Regarding the area intensity of the XRD peak of each crystal plane, it may be obtained by calculating the area intensity of each diffraction peak (XRD peak) using "smartlab-Studio2 (manufactured by Rigaku Corporation)" in the calculation program.

[0029] In the XRD measurement of the sintered body, the sintered body to be subjected to the XRD measurement may be a sintered body after surface grinding, which is a sintered body that has been subjected to mirror polishing treatment of the measurement surface in the order of automatic grinding using sandpaper, automatic grinding using diamond slurry with an average particle size of 3 μm, and automatic grinding using colloidal silica of 0.03 μm after cutting the sintered surface using a surface grinder.

[0030] The "crystallite diameter of monoclinic zirconia" (hereinafter also referred to as "D m ") is a value obtained using the following formula (4) based on the XRD pattern of the powder, and the "crystallite diameter of tetragonal zirconia" (hereinafter also referred to as "D t ") is a value obtained using the XRD pattern of the powder by the following formula (5).

[0031] D m= κλ / (βcosθ m )(4) D t = κλ / (βcosθ t )(5) In formulas (4) and (5), D m is the crystallite diameter (nm) of monoclinic zirconia, D t is the crystallite diameter (nm) of tetragonal zirconia, κ is the Scherrer constant (κ = 0.940), λ is the wavelength (0.15418 nm) of the light source used in the XRD measurement, β is the full width at half maximum (rad), θ m is the Bragg angle (rad) corresponding to the reflection of the (11-1) plane of monoclinic zirconia in the XRD measurement, and θ t is the Bragg angle (rad) corresponding to the reflection of the (111) plane of tetragonal zirconia in the XRD measurement.

[0032] The "BET specific surface area" is a value obtained by the multi-point BET method with the adsorbate being nitrogen (N2) in accordance with JIS R 1626-1996.

[0033] The "median particle size" (hereinafter also referred to as "D50") refers to the particle size corresponding to a volume ratio of 50% in the cumulative volume particle size distribution curve obtained by measuring the volume particle size distribution based on the laser diffraction method.

[0034] The "particle size distribution curve" is a curve showing the particle size distribution of the powder obtained by measuring the volume particle size distribution based on the laser diffraction method.

[0035] The "fracture toughness value" is the value of the fracture toughness measured by the method of the SEPB method specified in JIS R 1607 (MPa·m 0.5 ). The measurement of the fracture toughness value is carried out using a columnar sintered body specimen with a distance between supports of 16 mm, a width of 4 mm, and a thickness of 3 mm. It is sufficient to take the average value of 10 measurements as the fracture toughness value of the sintered body. In addition, in JIS R1607, two fracture toughness measurement methods, the IF method and the SEPB method, are specified. Compared with the SEPB method, the values measured by the IF method tend to be larger. Moreover, since the IF method is a simple measurement method, the fluctuations in the measured values for each measurement are large. Therefore, the fracture toughness value in this embodiment cannot be compared in terms of the absolute value with the fracture toughness value measured by the IF method. Similarly, the fracture toughness value measured by a method other than the SEPB method and the fracture toughness value measured by the SEPB method cannot be compared in terms of their absolute values.

[0036] "Flexural strength" refers to the value of the three-point flexural strength obtained through the three-point bending test in accordance with JIS R 1601. The flexural strength is measured using a columnar sintered body specimen with a distance between supports of 30 mm, a width of 4 mm, and a thickness of 3 mm. The average value of 10 measurements can be used as the flexural strength of the sintered body.

[0037] "Relative density" refers to the ratio (%) of the measured density to the true density. The measured density of the green body is the ratio of the mass measured by mass determination to the volume calculated from the size measurement (g / cm 3 ). The measured density of the sintered body is the ratio of the mass measured by mass determination to the volume measured by the Archimedes method (g / cm 3 ). The true density is the density (g / cm 3 ) calculated from the following equations (6) to (9). 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 M / 4.860) + (100 - Y A - Y M ) / ρ Z (9)

[0038] In equations (6) to (9), ρ0 is the true density, ρ Z is the true density of zirconia, A and C are constants, X is the molar ratio (mol%) of yttrium in terms of oxide relative to the total of zirconia (ZrO2) and yttrium in terms of oxide after conversion, and in addition, Y A and Y M are the mass ratios (mass%) of alumina in terms of Al2O3 and manganese in terms of Mn3O4 relative to the total after converting zirconia, yttrium, alumina, and manganese to ZrO2, Y2O3, Al2O3, and Mn3O4 respectively in the green body or sintered body.

[0039] In addition, when the green body or sintered body contains a colorant for color adjustment (described later), the true density can be calculated using equation (9') instead of equation (9). ρ0 = 100 / [(Y A / 3.987) + (Y M / 4.860) + (YN1 / M N1 )…+(Y Nn / M Nn )+(100-Y A -Y M -Y N1 … -Y Nn ) / ρ Z ] (9')

[0040] In formula (9'), Y N1 , …, Y Nn is the mass ratio (mass %) of each toner colorant in terms of oxide relative to the total amount of powder (described later), M N1 , …, M Nn It is the amount of substance (g / mol) of each toner colorant after conversion into oxide, and n is an integer.

[0041] The "hue" refers to the color tone measured by the method based on JIS Z 8781-5 corresponding to ISO 11664-4. * a * b * The color tone is numerically expressed in the color system, which is the same as the brightness L. * , Hue a * and b * Determine the L of 1 point * a * b * The hue corresponding to the coordinates. "Hue fluctuation" refers to L * a * b * Brightness L in the color system * The color hue fluctuation and color tone may be measured under the following conditions using a general spectrophotometer (for example, CM-700d, manufactured by Konica Minolta Inc.). Light source: F2 light source Viewing angle: 10° Measurement method: SCI Background: Black background Test sample: (sample thickness) 1.3 ± 0.1 mm

[0042] [powder] The powder of this embodiment is a powder mainly containing zirconia (a powder with zirconia as the main component, so-called zirconia powder), not limited to a powder containing only zirconia, but a powder containing components other than zirconia, especially a powder containing zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina. Preferably, the powder of this embodiment may essentially be a powder containing zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina, and may be a powder containing a manganese compound and alumina and containing yttrium-containing zirconia.

[0043] Zirconia containing yttrium as a stabilizing element is yttrium-stabilized zirconia, that is, yttria-stabilized zirconia. Yttrium is contained in zirconia as a stabilizing element. Thereby, the crystal phase of zirconia is stabilized.

[0044] The content of yttrium in the powder (hereinafter also referred to as "yttrium amount") only needs to be the content at which zirconia is partially stabilized. The yttrium amount is calculated by the ratio (mol%) of yttrium in terms of Y2O3 to the total amount of yttrium in terms of Y2O3 and zirconia (ZrO2) in terms of Y2O3 (={Y2O3 / (ZrO2 + Y2O3)}×100 [mol%]).

[0045] The fracture toughness value measured by the SEPB method is likely to be high. Therefore, the yttrium amount of the powder of this embodiment is preferably 1.3 mol% or more and less than 2.0 mol%. For example, it can be cited as: 1.3 mol% or more, 1.4 mol% or more, 1.5 mol% or more, or 1.6 mol% or more, and less than 2.0 mol%, 1.9 mol% or less, 1.8 mol% or less, 1.7 mol% or less, or 1.6 mol% or less. The yttrium amount can be, for example, 1.3 mol% or more and less than 2.0 mol%, 1.3 mol% or more and 1.9 mol% or less, 1.3 mol% or more and 1.8 mol% or less, 1.3 mol% or more and 1.7 mol% or less, 1.3 mol% or more and 1.6 mol% or less, 1.4 mol% or more and less than 2.0 mol%, 1.4 mol% or more and 1.9 mol% or less, 1.4 mol% or more and 1.8 mol% or less, 1.4 mol% or more and 1.7 mol% or less, 1.4 mol% or more and 1.6 mol% or less, 1.5 mol% or more and less than 2.0 mol%, 1.5 mol% or more and 1.9 mol% or less, 1.5 mol% or more and 1.8 mol% or less, 1.5 mol% or more and 1.7 mol% or less, 1.5 mol% or more and 1.6 mol% or less, 1.6 mol% or more and less than 2.0 mol%, 1.6 mol% or more and 1.9 mol% or less, 1.6 mol% or more and 1.8 mol% or less, or 1.6 mol% or more and 1.7 mol% or less.

[0046] Yttrium is preferably dissolved in zirconia, and the powder of this embodiment preferably does not contain undissolved yttrium. In this embodiment, it can be regarded as not containing undissolved yttrium (that is, all yttrium is dissolved in zirconia) by virtue of the fact that no XRD peak from yttrium compounds is detected in its XRD pattern.

[0047] The powder of this embodiment preferably does not contain stabilizing elements other than yttrium, but other stabilizing elements may also be contained as long as the effects of the powder of this embodiment are not impaired. As other stabilizing elements, at least one of calcium (Ca) and magnesium (Mg) can be cited.

[0048] As the main crystal phases of zirconia, monoclinic zirconia, tetragonal zirconia, and cubic zirconia are known, and the crystal phase of zirconia in this embodiment can be regarded as containing at least any one of these three crystal phases. The zirconia in the powder of this embodiment preferably contains monoclinic zirconia, more preferably contains monoclinic zirconia and at least any one of tetragonal zirconia and cubic zirconia, and further preferably contains monoclinic zirconia and tetragonal zirconia. Moreover, at the amount of yttrium in the powder of this embodiment, it can be cited that its crystal phase is composed of monoclinic zirconia and tetragonal zirconia.

[0049] The monoclinic ratio is preferably more than 70%, further preferably 80% or more, and still further preferably 85% or more. The monoclinic ratio is 100% or less. When zirconia contains at least any one of tetragonal zirconia and cubic zirconia, the monoclinic ratio is less than 100%, and can be 99% or less or 90% or less. The monoclinic ratio can be exemplified as greater than 70% and 100% or less, 80% or more and 100% or less, or 85% or more and 95% or less. On the other hand, it can be 90% or more and 100% or less, 95% or more and less than 100%, or 95% or more and 99% or less.

[0050] The tetragonal ratio is 30% or less, less than 30%, less than 20% or 15% or less. In addition, it can also be 10% or less or 7% or less. When zirconia does not contain tetragonal zirconia, the tetragonal ratio is 0%, but the tetragonal ratio can also be 0% or more, greater than 0% or 10% or more. For example, the tetragonal ratio can be 0% or more and less than 15%, 0% or more and less than 20%, 0% or more and less than 30%, greater than 0% and less than 15%, greater than 0% and less than 20%, 10% or more and less than 30%, or 10% or more and 15% or less.

[0051] Regarding the powder of this embodiment, the crystal phase of zirconia in the powder of this embodiment preferably consists of monoclinic zirconia and tetragonal zirconia. At this time, the sum of the monoclinic ratio and the tetragonal ratio is 100%.

[0052] In the composition range of the powder of the present embodiment, the crystal phase of zirconia can be confirmed by the XRD peak corresponding to the XRD peak of zirconia in the crystal phase confirmed by the XRD pattern of the powder of the present example.

[0053] The crystallite diameter (D m ) of monoclinic zirconia is greater than 23 nm, 30 nm or more, 31 nm or more, 32 nm or more, or 34 nm or more. Additionally, it is preferably 80 nm or less, 60 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, or 35 nm or less. Examples include: greater than 23 nm and 80 nm or less, 30 nm or more and 60 nm or less, 30 nm or more and 50 nm or less, 31 nm or more and 50 nm or less, 31 nm or more and 45 nm or less, 32 nm or more and 45 nm or less, 32 nm or more and 45 nm or less, or 34 nm or more and 40 nm or less. If the monoclinic ratio becomes below a certain value, D m may decrease. Therefore, D m is greater than 23 nm, 31 nm or more, or 32 nm or more. Additionally, it can also be 40 nm or less or 35 nm or less. Moreover, D m can be greater than 23 nm and 40 nm or less, 31 nm or more and 35 nm or less, or 32 nm or more and 35 nm or less. It is possible to exemplify having such a D m and a monoclinic ratio greater than 70% and 95% or less.

[0054] The crystallite diameter (D t ) of tetragonal zirconia is 30 nm or more, 35 nm or more, or 37 nm or more. Additionally, it is preferably 85 nm or less, 50 nm or less, 40 nm or less, or 38 nm or less. Examples include: 30 nm or more and 85 nm or less, 35 nm or more and 40 nm or less, or 37 nm or more and 40 nm or less. Different from D m , the influence of the monoclinic ratio on D t is small.

[0055] The ratio of Dm to Dt in the powder of this embodiment (hereinafter also referred to as "Dm / Dt") [nm / nm] can be: 0.7 or more and 1.2 or less, 0.8 or more and 1.0 or less, or 0.8 or more and 0.9 or less. In the case where the monoclinic ratio of the powder of this embodiment is below a certain value, it can be cited that there is no correlation between the monoclinic ratio and Dm / Dt, and Dt is greater than Dm. On the other hand, when the monoclinic ratio is above a certain value, as the monoclinic ratio increases, Dm / Dt tends to increase. Therefore, for example, when the monoclinic ratio is greater than 70% and 95% or less, Dm / Dt is 0.8 or more and 0.9 or less. In contrast, it can be cited that when the monoclinic ratio is greater than 95% and 100% or less, Dm / Dt is greater than 0.9 and 1.2 or less, and Dt can also be less than Dm.

[0056] The BET specific surface area of the powder of this embodiment is preferably 25 m 2 / g or less, less than 20 m 2 / g, 18 m 2 / g or less, or 17 m 2 / g or less. Additionally, it is preferably 6 m 2 / g or more, 8 m 2 / g or more, 10 m 2 / g or more, 12 m 2 / g or more, greater than 13 m 2 / g, 15 m 2 / g or more, or 16 m 2 / g or more. By making the BET specific surface area 6 m 2 / g or more, sintering can be easily carried out at a relatively low temperature. Additionally, by being 25 m 2 / g or less, there is a tendency to suppress physical aggregation of the powder. The BET specific surface area can be, for example: 6 m 2 / g or more and less than 20 m 2 / g, 8 m 2 / or more and 18 m 2 / g or less, 10 m 2 / g or more and 17 m 2 / g or less, 12 m 2 / g or more and 17 m 2 / g or less, greater than 13 m 2 / g and 17 m 2 / g or less, or 15 m 2 / g or more and 17 m 2 / g or less. On the other hand, it can also be 6 m 2 / g or more and 17 m 2 / g or less, 8 m 2 / g or more and 15 m 2 / g or less, or 8 m2 Above / g and 13m 2 Below.

[0057] The powder of this embodiment preferably contains zirconia with a monoclinic ratio greater than 70%, D m Is greater than 23 nm and 80 nm or less, and the BET specific surface area is 25 m 2 / g or less, more preferably contains zirconia with a monoclinic ratio of 85% or more and 95% or less, D m Is 30 nm or more and 50 nm or less, and the BET specific surface area is greater than 13 m 2 / g and 18 m 2 / g or less.

[0058] The powder of this embodiment contains a manganese compound as a black coloring element (hereinafter also referred to as "black colorant"). The manganese compound is preferably a powder of a manganese compound. The manganese compound may be any compound containing manganese (Mn), preferably a manganese oxide, and examples thereof include one or more selected from manganese oxide (MnO), manganese dioxide (MnO2), manganese sesquioxide (Mn2O3), and manganese tetraoxide (Mn3O4). As a preferred manganese compound, one or more selected from manganese oxide, manganese sesquioxide, and manganese tetraoxide can be cited, and further manganese tetraoxide can be cited. The content of the manganese compound in the powder of this embodiment (hereinafter also referred to as "manganese amount") is preferably 0.1% by mass or more and 0.6% by mass or less in terms of the mass ratio of the manganese compound converted to Mn3O4 to the total amount of the powder. If the manganese amount is less than 0.1% by mass, the fluctuation of the hue of the sintered body caused by the difference in the sintering temperature, particularly the fluctuation of the brightness L * Becomes larger. In addition, if the manganese amount is greater than 0.6% by mass, the brightness L *The fluctuations become larger. If the manganese content is further increased, defects such as cracking are likely to occur during sintering. The manganese content is, for example, 0.1% by mass or more, 0.2% by mass or more, 0.3% by mass or more, 0.4% by mass or more, or 0.5% by mass or more, and further, 0.6% by mass or less, 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, or 0.2% by mass or less. Examples of the manganese content include: 0.1% by mass or more and 0.2% by mass or less, 0.1% by mass or more and 0.3% by mass or less, 0.1% by mass or more and 0.4% by mass or less, 0.1% by mass or more and 0.5% by mass or less, 0.1% by mass or more and 0.6% by mass or less, 0.2% by mass or more and 0.3% by mass or less, 0.2% by mass or more and 0.4% by mass or less, 0.2% by mass or more and 0.5% by mass or less, 0.2% by mass or more and 0.6% by mass or less, 0.3% by mass or more and 0.4% by mass or less, 0.3% by mass or more and 0.5% by mass or less, 0.3% by mass or more and 0.6% by mass or less, 0.4% by mass or more and 0.5% by mass or less, 0.4% by mass or more and 0.6% by mass or less, or 0.5% by mass or more and 0.6% by mass or less.

[0059] In the powder of the present embodiment, only a manganese compound may be included as the black colorant. On the other hand, within the range that does not impair the effects of the powder of the present embodiment, in addition to the manganese compound, a black colorant other than the manganese compound may also be contained. Thereby, fine adjustment of the hue can be performed. Examples of the black colorant other than the manganese oxide include compounds of one or more selected from cobalt (Co), chromium (Cr), iron (Fe), titanium (Ti), nickel (Ni), and vanadium (V), and further, at least any one of cobalt and iron. In addition, the content of these elements (hereinafter also referred to as "toning colorants") is preferably less than the manganese content. As the mass ratio of the toning colorant in terms of oxide to the total amount of the powder, 0% by mass or more or more than 0% by mass can be exemplified, and further, 0.3% by mass or less or 0.2% by mass or less can be exemplified. In addition, 0% by mass or more and 0.3% by mass or less, more than 0% by mass and 0.3% by mass or less, or more than 0% by mass and 0.2% by mass or less can be exemplified.

[0060] In the powder of the present embodiment, the "total amount of the powder" refers to the total amount of the rare earth elements and metal elements contained in the powder in terms of oxide. In addition, for the conversion of each element into an oxide, examples include: cobalt (Co) is Co3O4, chromium (Cr) is Cr2O3, iron (Fe) is Fe2O3, titanium (Ti) is TiO2, nickel (Ni) is NiO, vanadium (V) is V2O5, and aluminum (Al) is Al2O3.

[0061] The powder of this embodiment contains alumina (Al2O3). The alumina is preferably at least one of a sol of alumina and a powder of alumina, and more preferably a powder of alumina. It is considered that by coexisting a manganese compound with alumina in a content within the following range, even if the sintering temperature varies, the hue of the sintered body is less likely to fluctuate.

[0062] The content of alumina in the powder of this embodiment (hereinafter also referred to as "alumina amount") is 0.2% by mass or more and 1.5% by mass or less in terms of the mass ratio of aluminum in terms of Al2O3 to the total amount of the powder. If the alumina amount is less than 0.2% by mass or alumina is not contained, the fluctuation of the hue caused by the variation of the sintering temperature, especially the luminance L * becomes larger. The alumina amount is 0.2% by mass or more, 0.25% by mass or more, 0.5% by mass or more, 0.75% by mass or more, 1.0% by mass or more, or 1.2% by mass or more, and further, 1.5% by mass or less, 1.25% by mass or less, 1.0% by mass or less, 0.75% by mass or less, or 0.5% by mass or less. Examples of the alumina amount include: 0.2% by mass or more and 1.5% by mass or less, 0.2% by mass or more and 1.25% by mass or less, 0.2% by mass or more and 1.0% by mass or less, 0.2% by mass or more and 0.75% by mass or less, 0.2% by mass or more and 0.5% by mass or less, 0.25% by mass or more and 1.5% by mass or less, 0.25% by mass or more and 1.25% by mass or less, 0.25% by mass or more and 1.0% by mass or less, 0.25% by mass or more and 0.75% by mass or less, 0.25% by mass or more and 0.5% by mass or less, 0.5% by mass or more and 1.5% by mass or less, 0.5% by mass or more and 1.25% by mass or less, 0.5% by mass or more and 1.0% by mass or less, 0.5% by mass or more and 0.75% by mass or less, 0.75% by mass or more and 1.5% by mass or less, 0.75% by mass or more and 1.25% by mass or less, 0.75% by mass or more and 1.0% by mass or less, 1.0% by mass or more and 1.5% by mass or less, 1.0% by mass or more and 1.25% by mass or less, or 1.2% by mass or more and 1.5% by mass or less.

[0063] In yttrium-containing zirconia (high-toughness zirconia) with a yttrium amount less than 2 mol%, it is considered that by limiting the manganese compound and the alumina amount to specific ranges respectively, even in the case of containing a certain amount or more of coloring elements, a sintered body can be obtained without defects, and the fluctuation of the hue of the sintered body caused by the variation of the sintering temperature during sintering can be suppressed. As one of the reasons, it can be cited that in a black zirconia sintered body, among the hues visually recognized, compared with the influence of the hue angles a * and b * , the luminance L *The influence is greater. Moreover, it is speculated that by coexisting manganese compounds with alumina in high-toughness zirconia, the reaction between manganese compounds and alumina is induced, the valence of manganese is stabilized, the hue of the sintered body is stabilized, and fluctuations in hue are particularly suppressed.

[0064] The brightness L of the sintered body obtained when sintering is performed at a sintering temperature of 1200°C to 1400°C * is not likely to fluctuate. Therefore, the mass ratio of alumina in terms of Al2O3 to manganese compounds in terms of Mn3O4 of the powder of the present embodiment (hereinafter also referred to as "Al / Mn ratio") is 0.1 or more, 0.4 or more, or 0.7 or more. Additionally, it is preferably 5.0 or less, 3.0 or less, 2.5 or less, or 1.5 or less. Examples of the Al / Mn ratio of the powder of the present embodiment include 0.1 or more and 5.0 or less, 0.4 or more and 3.0 or less, 0.4 or more and 1.5 or less.

[0065] The powder of the present embodiment may contain a binder for improving fluidity. In this case, the powder of the present embodiment can be regarded as a powder composition containing powder and a binder. The binder contained in this powder composition can be a known binder for ceramic compositions, and examples thereof include thermoplastic resins. As a preferred binder, any one or more of acrylic resins, polystyrene, and polycarbonate alkyl esters can be exemplified, and further, acrylic resins (for example, one or more selected from AS-1100, AS-1800, and AS-2000, all manufactured by Toagosei Co., Ltd., etc.) can be exemplified.

[0066] In addition to the binder, the powder composition may contain components such as wax as additives. By containing these components, additional effects such as good mold release from a self-forming mold (die) can be obtained. Examples of components such as wax include one or more selected from polyethylene, polypropylene, polyacrylonitrile, acrylonitrile-styrene copolymer, ethylene-vinyl acetate copolymer, styrene-butadiene copolymer, polyacetal resin, petroleum-based wax, synthetic wax, plant-based wax, stearic acid, phthalate-based plasticizer, and adipate.

[0067] When the powder of the present embodiment contains a binder, wax, etc. (hereinafter also referred to as "binder, etc."), examples of the mass ratio of the powder mass to the mass of the powder composition (= the total of the powder and the binder, etc.) include 50% by mass or more and 97% by mass or less, 70% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less. The content of the powder in the powder composition can be obtained from the mass ratio of the powder composition after removing the binder, etc. to the mass of the powder composition. The method for removing the binder, etc. is arbitrary, and examples thereof include heat treatment in an air atmosphere at 200°C or more and 500°C or less.

[0068] The powder of this embodiment preferably contains no impurities. On the other hand, inevitable impurities such as hafnium dioxide (HfO2) of zirconia may also be included. In addition, in the calculation of values such as content and density derived from the composition, hafnium dioxide can be regarded as zirconia.

[0069] When the powder of this embodiment is a powder of yttria-stabilized zirconia containing alumina, a manganese compound, and a binder, its composition can be obtained as follows. Total amount of powder: Al2O3 + Mn3O4 + Y2O3 + ZrO2 [g] Amount of alumina: {Al2O3 / (Al2O3 + Mn3O4 + Y2O3 + ZrO2)} × 100 [mass%] Amount of manganese: {Mn3O4 / (Al2O3 + Mn3O4 + Y2O3 + ZrO2)} × 100 [mass%] Amount of zirconia (yttria-stabilized zirconia): {(Y2O3 + ZrO2) / (Al2O3 + Mn3O4 + Y2O3 + ZrO2)} × 100 [mass%] Amount of stabilizing element (amount of yttrium): {Y2O3 / (Y2O3 + ZrO2)} × 100 [mol%] The content of the binder can be obtained by {(W2 - W1) / W2} × 100 [mass%] (where W1 is the mass of the powder after heat treatment in an air atmosphere at 200 °C or higher and 500 °C or lower for 2 hours, and W2 is the mass of the powder before this treatment). In addition, due to differences in the calculation method, when the binder is included, the composition of the powder of this embodiment (the sum of the total amount of the powder and the mass of the binder) may sometimes be outside 100 mass%.

[0070] The median particle size (D50) of the powder of this embodiment can be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, or 0.4 μm or more, and additionally 1.0 μm or less, 0.7 μm or less, 0.55 μm or less, 0.5 μm or less, or 0.45 μm or less. Examples of D50 can be: 0.1 μm or more and 1.0 μm or less, 0.1 μm or more and 0.7 μm or less, 0.2 μm or more and 0.55 μm or less, 0.2 μm or more and 0.5 μm or less, 0.2 μm or more and 0.45 μm or less, 0.3 μm or more and 0.45 μm or less, 0.4 μm or more and 0.55 μm or less, or 0.4 μm or more and 0.5 μm or less.

[0071] The powder of the present embodiment may be exemplified by a volume particle size distribution curve that is multimodal, preferably bimodal, and more preferably a volume particle size distribution curve having peaks at least in the particle size range of 0.05 μm or more and 0.2 μm or less and in the particle size range of more than 0.2 μm and 0.5 μm or less, and further having peaks (extrema) in the particle size range of 0.05 μm or more and 0.2 μm or less and in the particle size range of 0.3 μm or more and 0.5 μm or less.

[0072] The powder of the present embodiment preferably has high formability. When the powder is uniaxially press-molded at a pressure of 70 ± 5 MPa and then processed by cold isostatic pressing (hereinafter also referred to as "CIP") at a pressure of 196 ± 5 MPa to form a compact, the relative density of the compact (hereinafter also referred to as "compact density") is preferably 49% or more and 56% or less, or 50% or more and 54% or less.

[0073] The powder of the present embodiment preferably has little fluctuation in the hue of the sintered body obtained by sintering it. For example, 3 ± 0.3 g of the powder of the present embodiment is filled into a mold with a diameter of 25 mm, and after repeatedly performing uniaxial press molding at a pressure of 70 ± 5 MPa and CIP treatment at a pressure of 196 ± 5 MPa to form 5 compacts (powder compacts), when the atmospheric atmosphere, the heating rate is 100 °C / hour, and the holding time at the sintering temperature is set to 2 hours, and when normal pressure sintering is performed on 1 compact at each of the sintering temperatures of 1200 °C, 1250 °C, 1300 °C, 1350 °C, and 1400 °C, the difference between the maximum value and the minimum value of the brightness L * (hereinafter also referred to as "L * fluctuation") is preferably 1.4 or less, 1.0 or less, 0.8 or less, or 0.5 or less. It is preferred that the L * fluctuation is small, but values of 0 or more, greater than 0, or 0.2 or more can be cited, and examples include 0 or more and 1.4 or less, greater than 0 and 0.8 or less, or 0.2 or more and 0.5 or less.

[0074] When sintered compacts are formed under the same conditions, the difference between the maximum value and the minimum value of the chroma C * (hereinafter also referred to as "C * fluctuation") is preferably 0.40 or less, 0.35 or less, or 0.33 or less. In a sintered body of zirconia that is painted black, the influence of the C * fluctuation on the hue visually recognized is smaller than that of the L * fluctuation. However, from the viewpoint of quality stability, it is preferred that the C * fluctuation is small, and values of 0 or more, 0.15 or more, or 0.25 or more can be cited, and examples include 0 or more and 0.40 or less, 0.15 or more and 0.35 or less, or 0.25 or more and 0.33 or less.

[0075] The powder of the present embodiment can be used as a precursor for a pre-sintered body or a sintered body of zirconia, and is suitable as a raw material powder for structural materials such as components for crushers, precision mechanical parts, and optical connector parts, biocompatible materials such as dental materials, decorative components, and packaging materials such as outer packaging components for electronic devices.

[0076] [Manufacturing method of powder] As long as the powder of the present embodiment has the above-described configuration, its manufacturing method is not particularly limited. As a preferred manufacturing method, a method for manufacturing a powder in which a yttrium-containing zirconia powder containing yttrium in an amount of 1.3 mol% or more and less than 2.0 mol% in terms of Y2O3 relative to the total amount of zirconia and yttrium in terms of Y2O3, an alumina source, and a manganese compound source are mixed can be cited. This manufacturing method includes a step of mixing such that the content of alumina is 0.2 mass% or more and 1.5 mass% or less relative to the total amount of the powder, and the content of the manganese compound is 0.1 mass% or more and 0.6 mass% or less relative to the total amount of the powder.

[0077] The yttrium-containing zirconia powder, alumina source, and manganese compound source used in the above step (hereinafter also referred to as the "mixing step") may be the same as the yttrium-containing zirconia, manganese compound, and alumina contained in the powder of the present embodiment, respectively.

[0078] Regarding the mixing step, a yttrium-containing zirconia powder containing yttrium in an amount of 1.3 mol% or more and less than 2.0 mol% in terms of Y2O3 relative to the total amount of zirconia and yttrium in terms of Y2O3 is used.

[0079] The BET specific surface area of the yttrium-containing zirconia powder is preferably 6 m 2 / g or more, 8 m 2 / g or more, or 10 m 2 / g or more. Additionally, it is preferably 25 m 2 / g or less, 20 m 2 / g or less, 18 m 2 / g or less, 17 m 2 / g or less, or 15 m 2 / g or less. As a range of the BET specific surface area of the yttrium-containing zirconia powder, examples include 6 m 2 / g or more and 25 m 2 / g or less, 8 m 2 / g or more and 18 m 2 / g or less, 10 m 2 / g or more and 17 m 2 / g or less, 12 m 2 / g or more and 17 m 2 / g or less, or more than 13 m 2 / g and 17 m2 below / g. Additionally, it can also be 6 m 2 above / g and 18 m 2 below / g, 6 m 2 above / g and 15 m 2 below / g, or 6 m 2 above / g and 13 m 2 below / g. The BET specific surface area of the yttrium-containing zirconia powder is affected by the heat treatment temperature (presintering temperature) during its production, and there is a tendency for the BET specific surface area to decrease as the heat treatment temperature increases.

[0080] The average particle diameter (D50) of the yttrium-containing zirconia powder supplied to the mixing process is preferably 0.1 μm or more and 1.0 μm or less, more preferably 0.1 μm or more and 0.7 μm or less, 0.2 μm or more and 0.5 μm or less, 0.2 μm or more and 0.45 μm or less, or 0.3 μm or more and 0.45 μm or less.

[0081] The crystallite diameter of the monoclinic phase of the yttrium-containing zirconia powder is preferably greater than 23 nm and 80 nm or less, 30 nm or more and 60 nm or less, 30 nm or more and 50 nm or less, 31 nm or more and 50 nm or less, or 32 nm or more and 45 nm or less.

[0082] The yttrium-containing zirconia powder can be a powder obtained by any production method. For example, it is preferably a zirconia powder obtained by one or more methods selected from the hydrolysis method, hydrothermal synthesis method, and coprecipitation method, and more preferably a zirconia powder obtained by the hydrolysis method. As a particularly preferred zirconia powder, there can be mentioned a zirconia powder obtained by hydrolyzing a zirconia sol having an average sol particle diameter of 150 nm or more and 400 nm or less, preferably 180 nm or more and 400 nm or less, and more preferably 185 nm or more and 300 nm or less.

[0083] The manganese compound source is preferably at least one of manganese oxides and manganese compounds as its precursors, and examples thereof include one or more selected from manganese oxide, manganese dioxide, manganese sesquioxide, manganese tetraoxide, manganese hydroxide, basic manganese oxide, manganese chloride, and manganese acetate. It is preferably one or more selected from manganese oxide, manganese sesquioxide, and manganese tetraoxide, and more preferably manganese tetraoxide. The manganese compound source is preferably a powder of a manganese compound.

[0084] The content of the manganese compound source can be expressed as the proportion (mass %) of the manganese compound source converted to Mn3O4 relative to the total mass of the yttrium-containing zirconia powder, the manganese compound source converted to Mn3O4, and the alumina source converted to Al2O3 after mixing. The content of the manganese compound source is preferably 0.1 mass % or more and 0.6 mass % or less, 0.2 mass % or more and 0.5 mass % or less, or 0.3 mass % or more and 0.5 mass % or less.

[0085] The alumina source is at least one of alumina and an aluminum compound as its precursor, and examples thereof include one or more selected from alumina, aluminum hydroxide, aluminum nitrate, and aluminum chloride. Preferably, it is alumina, and more preferably at least one of an alumina sol and alumina powder. The alumina source is preferably at least one of a sol and a powder of an aluminum compound, further preferably a sol of an aluminum compound, and more preferably an alumina sol. The alumina sol has a smaller particle size and a larger specific surface area than alumina powder. Therefore, when the alumina source is an alumina sol, as the content of the alumina source increases, the BET specific surface area of the obtained powder tends to increase.

[0086] The content of the alumina source can be expressed as the proportion (mass %) of the alumina source relative to the total mass of the yttrium-containing zirconia powder, the manganese compound source converted to Mn3O4, and the alumina source converted to Al2O3 after mixing. For example, the content of the alumina source is preferably 0.2 mass % or more and 1.5 mass % or less, 0.2 mass % or more and 1.25 mass % or less, or 0.25 mass % or more and 1.0 mass % or less.

[0087] In the mixing step, the zirconia powder containing yttrium oxide, the manganese compound source, and the alumina source are mixed in such a manner that the composition is the same as that of the target powder. The mixing method in the mixing process can be at least any one of wet mixing and dry mixing, preferably wet mixing. As a specific wet mixing, one or more selected from ball milling, vibration milling, and continuous medium stirring milling can be exemplified, preferably a ball mill. As the mixing conditions based on the ball mill, for example, yttria-stabilized zirconia powder, an alumina source, and a manganese compound source are mixed with a solvent to prepare a slurry in which the mass ratio of these powders to the mass of the slurry is 30% by mass or more and 60% by mass or less. For this slurry, zirconia balls with a diameter of 1 mm or more and 15 mm or less are used as the grinding medium for grinding and mixing treatment. Yttria-stabilized zirconia with a low yttrium content is prone to cracking, chipping, etc. during sintering. In contrast, by performing the mixing based on the above-mentioned grinding and mixing treatment, the yield during sintering is likely to be high, and furthermore, the obtained sintered body tends to be less prone to hydrothermal deterioration. The treatment time can be appropriately changed according to the amount of powder to be ground and the grinding conditions. The longer the grinding and mixing time, the more the BET specific surface area tends to increase to reach equilibrium, and in addition, the average particle size tends to decrease to reach equilibrium. As the mixing time, 1 hour or more and 100 hours or less, or 10 hours or more and 50 hours or less can be exemplified. In addition, it can be 1 hour or more and 10 hours or less, or 1 hour or more and 5 hours or less.

[0088] The mixed powder can be dried by any method as needed. As the drying conditions, an air atmosphere, drying at 110°C or more and 130°C or less can be exemplified. In order to improve the handleability (processability) of the powder, the powder manufacturing method of the present embodiment may also include a step of granulating the powder (hereinafter, also referred to as "granulation step"). Granulation is a process of making powder particles aggregate to form aggregated particles. Granulation can be performed by any method, and spray granulation of a slurry obtained by mixing powder and a solvent can be exemplified. The solvent is at least one of water and alcohol, preferably water. The granulated powder (hereinafter also referred to as "powder granule") can be exemplified as having an average particle diameter of 30 μm or more and 90 μm or less, further 40 μm or more and 60 μm or less; and a bulk density of 1.00 g / cm 3 or more and 1.40 g / cm 3 or less, further 1.10 g / cm 3 or more and 1.30 g / cm 3 or less.

[0089] [Method for manufacturing a sintered body] After the powder of the present embodiment is formed, it is pre-fired or sintered by a known method to obtain a pre-fired body or a sintered body. For example, a sintered body can be manufactured by the following manufacturing methods: a manufacturing method of a sintered body having a step of performing atmospheric pressure sintering on the powder of the present embodiment at a temperature of 1200 °C or higher and 1400 °C or lower; a manufacturing method of a sintered body having a sintering step of sintering a formed body containing the powder of the present embodiment; a manufacturing method of a sintered body having a forming step of forming the powder of the present embodiment to obtain a formed body and a sintering step of sintering the formed body. In addition, as a preferred manufacturing method of the sintered body, a manufacturing method of a sintered body having a sintering step of performing atmospheric pressure sintering on a formed body containing the powder of the present embodiment at a temperature of 1200 °C or higher and 1400 °C or lower can be cited. Before sintering, a pre-firing step of pre-firing the formed body to obtain a pre-fired body may be provided. In this case, for the sintering step, the pre-fired body may be used instead of the formed body (hereinafter, the formed body or the pre-fired body is also referred to as "formed body etc.").

[0090] <Forming step> When the powder of the present embodiment is formed into a formed body, the forming can be performed by a known method, for example, one or more selected from uniaxial pressing, cold isostatic pressing, slip casting, and injection molding. When the powder composition or the like is formed using a resin, the obtained formed body can be heat-treated as needed to remove the resin. As the heat treatment conditions, an air atmosphere, 400 °C or higher and lower than 800 °C can be exemplified. In the present embodiment, the formed body is a composition having a certain shape composed of powder particles aggregated by physical force, particularly a composition in a state where heat treatment is not performed after the shape is given (for example, after forming). In addition, the formed body can be used interchangeably with the powder compact.

[0091] The main components in the formed body obtained through the forming step, that is, zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina do not change before and after forming and are the same composition as the powder of the present embodiment. Therefore, the obtained formed body is a formed body containing zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina, and examples of the formed body include: the content of the stabilizing element in terms of oxide is 1.3 mol% or more and less than 2.0 mol% relative to the total amount of zirconia and the stabilizing element in terms of oxide, the content of the alumina is 0.2 mass% or more and 1.5 mass% or less relative to the total amount of the formed body, and the content of the manganese compound is 0.1 mass% or more and 0.6 mass% or less relative to the total amount of the formed body.

[0092] <Pre-firing step> The formed body can also be pre-sintered as needed. The pre-sintering only needs to be performed by heat-treating at a temperature lower than the temperature at which densification caused by sintering of the powder occurs. As a pre-sintering process, for example, a pre-sintering method having a heat-treating process of heat-treating a formed body containing the powder of the present embodiment at 800°C or higher and lower than 1200°C in an air atmosphere can be cited. Thus, a pre-sintered body is obtained. In the present embodiment, the pre-sintered body is a composition having a certain shape composed of molten particles, and is a composition in a state where heat treatment has been performed at a temperature lower than the sintering temperature.

[0093] The main components of the pre-sintered body obtained through the pre-sintering process, that is, zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina, do not change before and after pre-sintering, and have the same composition as the powder and formed body of the present embodiment. Therefore, the obtained pre-sintered body is a formed body containing zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina. Examples of the pre-sintered body include: the content of the stabilizing element in terms of oxide is 1.3 mol% or more and less than 2.0 mol% relative to the total amount of zirconia and the stabilizing element in terms of oxide, the content of the alumina is 0.2 mass% or more and 1.5 mass% or less relative to the total amount of the pre-sintered body, and the content of the manganese compound is 0.1 mass% or more and 0.6 mass% or less relative to the total amount of the pre-sintered body.

[0094] <Sintering process> In the sintering process, sintering the formed body or the like is sufficient. Sintering can employ a known method, such as one or more selected from pressure sintering, vacuum sintering, and atmospheric pressure sintering. Sintering is preferably atmospheric pressure sintering. The sintering atmosphere is preferably an oxidizing atmosphere, more preferably an air atmosphere. As a preferred sintering method, for example, atmospheric pressure sintering is performed at a temperature of 1200°C or higher and 1550°C or lower, preferably 1200°C or higher and 1500°C or lower, more preferably 1200°C or higher and 1400°C or lower in an air atmosphere. In addition, in the sintering process, it is preferably not to perform sintering other than atmospheric pressure sintering, and preferably not to have a pressure sintering process. The sintering time can be appropriately set according to the amount, size, characteristics of the sintering furnace, etc. of the formed body or the like supplied for sintering. For example, it can be carried out for 0.5 hours or more and 5 hours or less, or 1 hour or more and 4 hours or less. In addition, "atmospheric pressure sintering" in the present embodiment means a method of sintering the object to be sintered (formed body or the like) by heating at a temperature above the temperature at which densification based on sintering occurs without applying an external force to the object to be sintered during sintering.

[0095] As the sintering conditions in the sintering process, the following conditions can be cited. Sintering method: Atmospheric pressure sintering Sintering temperature: 1200°C or higher and 1400°C or lower Sintering time: more than 1 hour and less than 5 hours Heating rate: 80°C / hour or more and 120°C / hour or less Sintering atmosphere: oxidation atmosphere, preferably atmospheric atmosphere

[0096] Furthermore, the following conditions can be cited. Sintering method: atmospheric pressure sintering Sintering temperature: 1200°C, 1250°C, 1300°C, 1350°C or 1400°C Sintering time: 2 hours Heating rate: 100°C / hour Sintering atmosphere: atmospheric atmosphere

[0097] [Sintered body] The sintered body of the present embodiment is a sintered body of yttrium-containing zirconia containing manganese and alumina and having a yttrium content of less than 2 mol%, and further is a zirconia sintered body mainly composed of yttrium-containing zirconia containing manganese and alumina and having a yttrium content of less than 2 mol%. In addition, the sintered body of the present embodiment is a sintered body having a black color, a so-called black sintered body (black zirconia sintered body).

[0098] In the sintered body of the present embodiment, yttrium is preferably dissolved in zirconia, and more preferably does not contain undissolved yttrium, and all yttrium is dissolved in zirconia. In the present embodiment, the case where XRD peaks of yttrium and its compounds cannot be confirmed can be regarded as not containing undissolved yttrium.

[0099] The monoclinic ratio of the sintered body of the present embodiment is preferably 0.5% or more, 0.5% or more, 1% or more, 2% or more, 5% or more or 7% or more, and preferably 15% or less, 14% or less, 12% or less, 11% or less or 10% or less. More preferably, it is 0.5% or more and 15% or less, or 0.8% or more and 12% or less. When the monoclinic ratio is 1% or more and 15% or less, 2% or more and 14% or less, 5% or more and 12% or less, or 7% or more and 11% or less, there is a tendency for the fracture toughness to increase, and thus it is preferred. On the other hand, when the monoclinic ratio is 0.5% or more and 11% or less, or 0.8% or more and 10% or less, there is a tendency for the flexural strength to increase, and thus it is preferred.

[0100] The surface of the sintered body just after sintering (as-sintered-surface; hereinafter also referred to as "sintered skin surface") is rough and contains many sources of damage such as irregularities. In order to prevent the sintered body from being damaged, it is preferable to remove the sintered skin surface of the sintered body by machining such as grinding before evaluation and various uses, and perform polishing to form a state in which a mirror-like surface (polished-surface; hereinafter also referred to as "mirror surface") is exposed. The mirror surface is a smooth surface, and a surface with Ra≤0.04μm can be exemplified. The monoclinic ratio is the value of the mirror surface of the sintered body. The sintered body of the present embodiment preferably has monoclinic zirconia in which the mirror surface satisfies the above monoclinic ratio. It is considered that, thereby, the sintered body of the present embodiment can be a sintered body having monoclinic zirconia in the whole sintered body, or a sintered body containing tetragonal zirconia that easily transforms into monoclinic zirconia.

[0101] In the sintered body of the present embodiment, the zirconia contains at least one of monoclinic zirconia, tetragonal zirconia, and cubic zirconia, and preferably contains monoclinic zirconia and tetragonal zirconia.

[0102] The monoclinic zirconia contained in the sintered body of the present embodiment is preferably monoclinic zirconia having at least an XRD peak corresponding to the (111) plane of monoclinic zirconia in its XRD pattern. By containing such monoclinic zirconia in the state before the deterioration treatment, the sintered body easily exhibits a high fracture toughness value, and there is also a tendency that hydrothermal deterioration hardly occurs. When monoclinic zirconia is generated due to the deterioration of the sintered body, the intensity of the XRD peak corresponding mainly to the (11-1) plane of monoclinic zirconia in the XRD pattern becomes stronger. In contrast, the monoclinic zirconia contained in the sintered body of the present embodiment preferably has at least an XRD peak corresponding to the (111) plane of monoclinic zirconia in its XRD pattern. The monoclinic intensity ratio of the sintered body of the present embodiment is preferably 0 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 1.0 or more. The monoclinic intensity ratio can be 10 or less, 8 or less, 5 or less, 3 or less, 1.5 or less, 1.2 or less, or 1.0 or less. In addition, 0 or more and 10 or less, 0.5 or more and 3 or less, or 1.0 or more and 1.5 or less can be exemplified. The monoclinic intensity ratio is obtained by formula (3). Therefore, in I m (111) is zero, that is, in a sintered body that does not have an XRD peak corresponding to the (111) plane of monoclinic zirconia, the monoclinic intensity ratio is infinite and a value cannot be obtained. That is, the sintered body of the present embodiment preferably does not contain a sintered body with an infinite monoclinic intensity ratio.

[0103] The relative density of the sintered body of the present embodiment (hereinafter also referred to as "sintered body density") can be exemplified as 98% or more, 98.4% or more, or 99% or more, preferably 98% or more and 100% or less, 98.4% or more and 100% or less, or 99% or more and 100% or less.

[0104] Furthermore, the sintered body of the present embodiment is preferably a sintered body in a state obtained by atmospheric pressure sintering (so-called atmospheric pressure sintered body), more preferably a sintered body in a state obtained by atmospheric pressure sintering in an air atmosphere. In addition, it is preferably in a state where no sintering treatment other than atmospheric pressure sintering is performed, and more preferably in a state where no sintering treatment is performed after atmospheric pressure sintering. As the sintering treatment other than atmospheric pressure sintering, one or more selected from pressure sintering, vacuum sintering, and microwave sintering can be exemplified.

[0105] The fracture toughness value of the sintered body of the present embodiment (the fracture toughness value measured by the method according to the SEPB method specified in JIS R 1607) can be exemplified as 6 MPa·m 0.5 or more and 12 MPa·m 0.5 or less, 6.2 MPa·m 0.5 or more, 7 MPa·m 0.5 or more, 7.7 MPa·m 0.5 or more, or 8 MPa·m 0.5 or more. The fracture toughness value is preferably high, but for example, it can be: 12 MPa·m 0.5 or less, 11.5 MPa·m 0.5 or less, 10.5 MPa·m 0.5 or less, 10.0 MPa·m 0.5 or less, or 9.5 MPa·m 0.5 or less. These upper limit values and lower limit values can be arbitrarily combined. For example, it can be: 6 MPa·m 0.5 or more and 12 MPa·m 0.5 or less, 6 MPa·m 0.5 or more and 11.5 MPa·m 0.5 or less, 6.2 MPa·m 0.5 or more and 12 MPa·m 0.5 or less, 6.2 MPa·m 0.5 or more and 11.5 MPa·m 0.5 or less, 7 MPa·m 0.5 or more and 12 MPa·m 0.5 or less, 7 MPa·m 0.5 or more and 11.5 MPa·m 0.5 or less, 8 MPa·m 0.5 or more and 12 MPa·m 0.5 or less, 7.7 MPa·m 0.512 MPa·m or more 0.5 7.7 MPa·m or less, or 0.5 11.5 MPa·m or more and 0.5 11.5 MPa·m or less. With such a fracture toughness value, it is easily processed into a sintered body having a thickness of 1 mm or less, further 0.5 mm or less. Thus, the sintered body of the present embodiment may sometimes be a sintered body having a thickness of 0.05 mm or more and 0.3 mm or less, further 0.08 mm or more and 0.25 mm or less.

[0106] The flexural strength of the sintered body of the present embodiment is preferably 900 MPa or more, 1000 MPa or more, 1100 MPa or more, or 1200 MPa or more, and preferably 1550 MPa or less, 1500 MPa or less, 1460 MPa or less, or 1400 MPa or less. In addition, as the flexural strength, examples include 900 MPa or more and 1550 MPa or less, 1000 MPa or more and 1500 MPa or less, 1000 MPa or more and 1500 MPa or less, 1100 MPa or more and 1460 MPa or less, or 1200 MPa or more and 1400 MPa or less.

[0107] It is preferable that the tetragonal zirconia contained in the sintered body of the present embodiment is less likely to be converted into monoclinic zirconia due to hydrothermal treatment (hereinafter also referred to as "hydrothermal deterioration"). The ratio of the tetragonal ratio after immersion treatment in hot water at 134 °C for 5 hours to the tetragonal ratio before immersion treatment in hot water at 134 °C for 5 hours (hereinafter also referred to as "residual tetragonal ratio" or "ΔT%") is preferably 15% or more, 70% or more, or 80% or more. When the tetragonal zirconia does not convert into monoclinic zirconia by immersion treatment in hot water at 134 °C for 5 hours, the residual tetragonal ratio is 100%. Therefore, the residual tetragonal ratio of the sintered body of the present embodiment is 100% or less, and examples include 95% or less or 90% or less. In addition, examples include 15% or more and 95% or less, 80% or more and 90% or less.

[0108] There is a tendency that the more the amount of manganese or alumina, the more the hydrothermal deterioration is suppressed. Since the sintered body of the present embodiment contains manganese and alumina, the residual tetragonal ratio can be exemplified as 15% or more and 100% or less, 20% or more and 100% or less, 50% or more and 100% or less, 65% or more and 100% or less, 70% or more and 95% or less, or 80% or more and 95% or less.

[0109] The sintered body of the present embodiment is black. When the hue is expressed in the L * a * b * color system, the brightness L* Preferably 40 or more and 50 or less, 42 or more and 48 or less, or 44 or more and 48 or less. In addition, hue a * is preferably -1.5 or more and 1.5 or less, more preferably -1.0 or more and 1.5 or less, and further preferably 0 or more and 1.0 or less, and hue b * is preferably -1.5 or more and 1.5 or less, more preferably -1.5 or more and 1.0 or less, and further preferably -1.0 or more and 0.5 or less.

[0110] The fluctuation of the hue caused by the change in the sintering temperature is represented by the difference between the maximum value and the minimum value of L * (L * fluctuation), and is preferably 1.4 or less, 1.0 or less, 0.8 or less, or 0.5 or less. It is preferred that the L * fluctuation is small, but 0 or more, greater than 0, or 0.2 or more can be cited, and 0 or more and 1.4 or less, greater than 0 and 0.8 or less, or 0.2 or more and 0.5 or less can be exemplified.

[0111] Chroma C * can be obtained by the following formula. C * = {(a * ) 2 + (b * ) 2} 0.5

[0112] The chroma C of the sintered body of the present embodiment * is more preferably 0 or more and 1.5 or less, 0 or more and 1.2 or less, or 0 or more and 1.0 or less. The fluctuation of the chroma caused by the change in the sintering temperature is represented by the difference between the maximum value and the minimum value of C * (C * fluctuation), and is preferably 0.4 or less, 0.35 or less, or 0.33 or less. The C * fluctuation of the black sintered body has a smaller influence on the visually recognized hue compared to the L * fluctuation. However, it is preferred that the C * fluctuation is small, and 0 or more or 0.2 or more can be exemplified.

[0113] In addition, the C * fluctuation and the L * fluctuation are respectively the fluctuations when the sintering temperature difference is ±200 °C. Examples

[0114] Hereinafter, the present disclosure will be described in more detail based on examples, but these examples do not make any limiting interpretation of the present disclosure. (Monoclinic ratio, tetragonal ratio, D t and Dm ) Using a conventional X-ray diffractometer (trade name: Ultima IV, manufactured by Rigaku Corporation), the XRD pattern of the powder sample was obtained. The conditions for XRD measurement are as follows. X-ray source: CuKα ray (λ = 0.15418 nm) Measurement mode: continuous scan Scanning speed: 4° / min Step size: 0.02° Measurement range: 2θ = 26° to 33° Using the obtained XRD pattern, the monoclinic ratio, tetragonal ratio, D t and D m .

[0115] (BET specific surface area) Using a conventional automatic specific surface area measuring device (device name: Trister 3300II, manufactured by Shimadzu Corporation) and nitrogen as the adsorption gas, the BET specific surface area of the powder sample was measured by the multi-point method based on JIS R 1626-1996. Before the measurement, the powder sample was degassed at 250 °C for 30 minutes as a pretreatment.

[0116] (Particle size distribution measurement) The volume particle size distribution curve of the powder sample was obtained by the HRA mode of a Microtrac particle size distribution meter (trade name: MT3000EXII, manufactured by MicrotracBEL Corporation), and the median particle size (D50) was measured therefrom. Before the measurement, the powder sample was suspended in pure water and dispersed for 3 minutes using an ultrasonic homogenizer as a pretreatment. The measurement conditions are as follows. Light source: semiconductor laser (wavelength: 780 nm) Voltage: 3 mW Refractive index of zirconia: 2.17 Refractive index of the solvent (water): 1.33

[0117] (Sintered body density) The measured density of the sintered body sample was measured by the Archimedes method. Before the measurement, after measuring the mass of the dried sintered body, the sintered body was placed in water and boiled for 1 hour as a pretreatment. The true density was obtained from the above formulas (6) to (9), and the relative density (%) was obtained from the value of the measured density (ρ) relative to the true density (ρ0) as the sintered body density.

[0118] (Fracture toughness value) The fracture toughness value of the sintered body specimen was measured by the method based on the SEPB method specified in JIS R1607. (Flexural strength) The flexural strength of the sintered body specimen was measured by a three-point bending test based on JIS R1601. The measurement was carried out using a columnar sintered body specimen with a distance between supports of 30 mm, a width of 4 mm, and a thickness of 3 mm, and the average value of 10 measurements was taken as the flexural strength.

[0119] (Color tone) The color tone of the sintered body specimen was measured using a spectrophotometer (device name: CM-700d, manufactured by Konica Minolta) under the following conditions. Light source: F2 light source Viewing angle: 10° Measurement method: SCI Background: Black background Measurement specimen: (specimen thickness) 1.3 ± 0.1 mm In addition, the fluctuation of the color tone was represented by the difference between the maximum value and the minimum value of the L * value of the sintered body at each sintering temperature (L * fluctuation). Chroma C * Based on the hue a * and the hue b * obtained by the above measurement, it was calculated by the following formula. C * = {(a * ) 2 + (b * ) 2} 0.5 The fluctuation of the chroma was represented by the difference between the maximum value and the minimum value of the C * value of the sintered body at each sintering temperature (C * fluctuation).

[0120] Example 1 In an aqueous solution of zirconium hydroxide sol, yttrium chloride hexahydrate and aqueous ammonia solution were added so that the yttrium content became 1.6 mol%, and a precipitate was obtained. After the obtained precipitate was washed with pure water and dried in an air atmosphere, it was pre-fired at 1000 °C for 2 hours in an air atmosphere to prepare yttrium-containing zirconia powder with a yttrium content of 1.6 mol%. The BET specific surface area of the obtained powder was 13.5 m 2 / g.

[0121] After mixing the obtained powder with pure water to form a slurry, alumina sol and Mn3O4 powder (Brownox (registered trademark), manufactured by Tosoh Corporation) were added such that, relative to the total amount (100% by mass) of yttria-stabilized zirconia powder, alumina sol, and Mn3O4 powder, alumina was 0.25% by mass and manganese in terms of Mn3O4 was 0.44% by mass to obtain a mixed slurry. The mixed slurry (powder content: 200 g) was treated by ball milling using zirconia balls with a diameter of 2 mm and then dried in an air atmosphere at 120 °C to obtain a powder with an alumina content of 0 . 25% by mass, a manganese content of 0.44% by mass, containing alumina and manganese tetroxide, and a yttria-stabilized zirconia powder with a yttrium content of 1 . 6 mol%. This powder was used as the powder for this example. Regarding the powder of the example, all of the yttrium was solid-solved in zirconia, the crystal phase of zirconia was composed of monoclinic zirconia and tetragonal zirconia, the monoclinic ratio was 89.3%, and the tetragonal ratio was 10.7%. In addition, the crystallite diameter (Dm) of the monoclinic zirconia in the powder of this example was 32.7 nm, the crystallite diameter (Dt) of the tetragonal zirconia was 37.1 nm, Dm / Dt was 0.88 [nm / nm], D50 was 0.44 μm, and the BET specific surface area was 15.6 m 2 / g.

[0122] In addition, the particle size distribution of the powder of this example was a bimodal particle size distribution having peaks at a particle size of 0.15 μm and a particle size of 0.45 μm. (Forming process) 3 g of the powder of this example was filled into a mold with a diameter of 25 mm, uniaxially pressed at a pressure of 70 MPa, and then subjected to CIP treatment at a pressure of 196 MPa to obtain a formed body (powder compact). (Sintering process) The obtained formed bodies were sintered under the following conditions respectively to obtain sintered bodies. Sintering method: atmospheric pressure sintering Sintering temperature: 1200 °C, 1250 °C, 1300 °C, 1350 °C, or 1400 °C Sintering time: 2 hours Heating rate: 100 °C / hour Sintering atmosphere: air atmosphere

[0123] Example 2 Except that the addition amount of alumina sol was set to 0 .Except for 5% by mass, powders and sintered bodies were obtained in the same manner as in Example 1. Regarding the powder of this example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. The monoclinic ratio was 86.4%, and the tetragonal ratio was 13.6%. In addition, the crystallite diameter (Dm) of monoclinic zirconia in the powder was 33.5 nm, the crystallite diameter (Dt) of tetragonal zirconia was 37.5 nm, Dm / Dt was 0.89 [nm / nm], D50 was 0.43 μm, and the BET specific surface area was 16.1 m 2 / g.

[0124] In addition, the particle size distribution of the powder of this example was a bimodal particle size distribution with peaks at a particle size of 0.15 μm and a particle size of 0.45 μm.

[0125] Example 3 Except for setting the addition amount of alumina sol to 0 . 75% by mass, powders and sintered bodies were obtained in the same manner as in Example 1. Regarding the powder of the example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. The monoclinic ratio was 87.0%, and the tetragonal ratio was 13.0%. In addition, the crystallite diameter (Dm) of monoclinic zirconia in the powder was 31.2 nm, the crystallite diameter (Dt) of tetragonal zirconia was 36.2 nm, Dm / Dt was 0.86 [nm / nm], D50 was 0.35 μm, and the BET specific surface area was 16.7 m 2 / g.

[0126] Example 4 Except for setting the addition amount of alumina sol to 1.25% by mass, powders and sintered bodies were obtained in the same manner as in Example 1. Regarding the powder of the example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. The monoclinic ratio was 87.0%, and the tetragonal ratio was 13.0%. In addition, the crystallite diameter (Dm) of monoclinic zirconia in the powder was 31.2 nm, the crystallite diameter (Dt) of tetragonal zirconia was 36.2 nm, Dm / Dt was 0.86 [nm / nm], D50 was 0.36 μm, and the BET specific surface area was 16.9 m 2 / g.

[0127] Example 5 Yttrium chloride hexahydrate was added to the aqueous solution of zirconium hydroxide sol so that the yttrium content became 1.9 mol%, the addition amount of Mn3O4 powder was set to 0.55 mass%, and the addition amount of alumina sol was set to 0.5 mass%. Except for this, powders and sintered bodies were obtained by the same method as in Example 1. Regarding the powder of this example, all yttrium was solid-dissolved in zirconia, its crystal phase was monoclinic zirconia and tetragonal zirconia, the monoclinic ratio was 88.8%, and the tetragonal ratio was 11.2%. In addition, the microcrystalline diameter (Dm) of monoclinic zirconia in the powder was 32.2 nm, the microcrystalline diameter (Dt) of tetragonal zirconia was 36.8 nm, Dm / Dt was 0.88 [nm / nm], D50 was 0.36 μm, and the BET specific surface area was 15.8 m 2 / g.

[0128] Example 6 Except for setting the pre-sintering temperature to 1100 °C, yttrium-containing zirconia powder with a yttrium content of 1.6 mol% was obtained by the same method as in Example 1. The BET specific surface area of the obtained powder was 8.0 m 2 / g.

[0129] Except for using the obtained yttrium-containing zirconia powder, powders and sintered bodies were obtained by the same method as in Example 1. Regarding the powder of this example, all yttrium was solid-dissolved in zirconia, its crystal phase was monoclinic zirconia and tetragonal zirconia, the monoclinic ratio was 97.3%, and the tetragonal ratio was 2.7%. In addition, the microcrystalline diameter (Dm) of monoclinic zirconia in the powder was 37.4 nm, D50 was 0.51 μm, and the BET specific surface area was 10.5 m 2 / g.

[0130] Example 7 Except for setting the pre-sintering temperature to 1100 °C, yttrium-containing zirconia powder with a yttrium content of 1.6 mol% was obtained by the same method as in Example 1. The BET specific surface area of the obtained powder was 8.0 m 2 / g.

[0131] Using the obtained yttrium-containing zirconia powder and adding alumina sol so that the alumina amount became 0.55 mass%, except for this, powders and sintered bodies were obtained by the same method as in Example 1. Regarding the powder of this example, all yttrium was solid-dissolved in zirconia, its crystal phase was monoclinic zirconia and tetragonal zirconia, the monoclinic ratio was 96.9%, and the tetragonal ratio was 3.1%. In addition, the microcrystalline diameter (Dm) of monoclinic zirconia in the powder was 37.3 nm, the microcrystalline diameter (Dt) of tetragonal zirconia was 37.5 nm, Dm / Dt was 0.99 [nm / nm], D50 was 0.50 μm, and the BET specific surface area was 11.2 m 2 / g.

[0132] Comparative Example 1 Powders and sintered compacts were obtained in the same manner as in Example 3, except that the addition amount of Mn3O4 powder was set to 0.66% by mass. Regarding the powder of this example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. In addition, the microcrystalline diameter (Dm) of the monoclinic zirconia in the powder was 31.2 nm, D50 was 0.35 μm, and the BET specific surface area was 16.8 m 2 / g.

[0133] Comparative Example 2 Powders and sintered compacts were obtained in the same manner as in Example 1, except that the addition amount of Mn3O4 powder was set to 0.88% by mass. Regarding the powder of this example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. In addition, the BET specific surface area was 16.8 m 2 / g.

[0134] Comparative Example 3 Yttrium-containing zirconia powder with a yttrium content of 1.6 mol% was obtained in the same manner as in Example 1, except that the pre-firing temperature was set to 980°C. The BET specific surface area of the obtained powder was 14.1 m 2 / g.

[0135] Powders and sintered compacts were obtained in the same manner as in Example 1, except that the obtained yttrium-containing zirconia powder was used and alumina sol was not added. Regarding the powder of this example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. In addition, the BET specific surface area was 17.7 m 2 / g.

[0136] Comparative Example 4 Yttrium-containing zirconia powder with a yttrium content of 1.6 mol% was obtained in the same manner as in Example 1, except that the pre-firing temperature was set to 980°C. The BET specific surface area of the obtained powder was 14.1 m 2 / g.

[0137] Powders and sintered compacts were obtained in the same manner as in Example 1, except that the obtained yttrium-containing zirconia powder was used and the addition amount of alumina sol was set to 0.05% by mass. Regarding the powder of this example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. In addition, the BET specific surface area was 17.8 m 2 / g.

[0138] Comparative Example 5 Except that the addition amount of Mn3O4 powder was set to 0.044% by mass, powders and sintered compacts were obtained by the same method as in Example 1. Regarding the powder of this comparative example, yttrium was completely dissolved in zirconia, and its crystal phases were monoclinic zirconia and tetragonal zirconia. In addition, the BET specific surface area was 16.5 m 2 / g.

[0139] The evaluation results of the powders of the examples and comparative examples are shown in Table 1, the evaluation results of the sintered compacts of the examples are shown in Table 2, and the evaluation results of the sintered compacts of the comparative examples are shown in Table 3. In addition, "L * fluctuation" in Tables 2 and 3 is the difference between the maximum value and the minimum value of the luminance L * , and "C * fluctuation" is the difference between the maximum value and the minimum value of the chroma C * .

[0140] [Table 1]

[0141] The Al / Mn ratio of the powder of the example was 0.5 or more and 3 or less, and the BET specific surface area was 10 m 2 / g or more and 17 m 2 / g or less. From Examples 1 to 4, it was confirmed that: as the content of the alumina sol increased, the BET specific surface area tended to increase. Similarly, in Examples 6 and 7, it was also confirmed that: if the alumina sol increased, the BET specific surface area became higher.

[0142] [Table 2]

[0143] [Table 3]

[0144] As shown in Examples 1 to 4, the value of the L * fluctuation of the sintered compact of the example was small, and the fluctuation of the hue was small. In contrast, the following results were obtained: the L * fluctuation of the sintered compact of Comparative Example 1 with a Mn3O4 content of 0.66% by mass was as large as 1.60; regarding the sintered compact of Comparative Example 2 with a Mn3O4 content of 0.88% by mass, the sintered compact cracked. In addition, the L * fluctuation of the sintered compact of Comparative Example 5 with a Mn3O4 content of 0.044% by mass was 9.86, and the fluctuation of the hue was extremely large. On the other hand, the L * fluctuation of the sintered compact of Comparative Example 3 with a Mn3O4 content of 0.44% by mass and no Al2O3 was 1.41, and in addition, the L *The fluctuation is 1.45, and the fluctuations of the hues are relatively large.

[0145] In addition, regarding the monoclinic intensity ratio, for Example 1, it is 1.08 (sintering temperature 1250°C), 2.13 (sintering temperature 1300°C), and 1.71 (sintering temperature 1350°C), and for Example 2, it is 1.20 (sintering temperature 1250°C), 1.14 (sintering temperature 1300°C), and 1.86 (sintering temperature 1350°C).

[0146] Furthermore, the mechanical properties of the examples and comparative examples were evaluated. The results are shown in Tables 4 and 5.

[0147] [Table 4]

[0148] It can be confirmed from Table 4 that: the fracture toughness value of the sintered body obtained by sintering the powder of this example at a relatively low sintering temperature of 1250°C is 8.5 MPa / m 0.5 As described above, even though it contains coloring elements and appears black, it also shows a relatively high fracture toughness value.

[0149] [Table 5]

[0150] It can be confirmed from Tables 4 and 5 that: if the sintering temperature is increased, there is a tendency for the fracture toughness value to become higher. Even when the sintering temperature is 1300°C, a fracture toughness value of 7.5 MPa / m 0.5 can be obtained, and further it is 9.0 MPa / m 0.5 for the high-toughness zirconia as described above. In addition, it can be confirmed from Table 5 that: even when the sintering temperature is set higher, the fracture toughness value is 7.5 MPa / m 0.5 and further it is 9.0 MPa / m 0.5 as described above, and the flexural strength is 1000 MPa or more. A high-toughness zirconia sintered body with both a relatively high flexural strength and a relatively high fracture toughness value can be obtained from the powder of this example.

[0151] Furthermore, the sintered body obtained in Example 1 was immersed in hot water at 134°C for 5 hours, and the retained tetragonal phase ratio was determined. The results are shown in Table 6.

[0152] [Table 6]

[0153] It can be confirmed that: as the sintering temperature decreases, there is a tendency for the retained tetragonal phase ratio to become higher. In addition, the retained tetragonal phase ratio of the sintered body of Example 2 with a sintering temperature of 1350°C is 86.3%, which is higher than that of the sintered body of Example 1 sintered at the same temperature.

[0154] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2022-192258, filed on November 30, 2022, are incorporated herein by reference and made a part of this disclosure specification.

Claims

1. A powder, characterized in that, the powder contains zirconia containing yttrium as a stabilizing element, a manganese compound, and alumina, the content of the stabilizing element in terms of oxide is 1.3 mol% or more and less than 2.0 mol% relative to the total amount of zirconia and the stabilizing element in terms of oxide, the content of the alumina is 0.2% by mass or more and 1.5% by mass or less relative to the total amount of the powder, the content of the manganese compound is 0.1% by mass or more and 0.6% by mass or less relative to the total amount of the powder.

2. The powder according to claim 1, wherein, the powder contains zirconia with a monoclinic ratio greater than 70%, the crystallite diameter of monoclinic zirconia is greater than 23 nm and 80 nm or less, The BET specific surface area of the powder is 25 m 2 / g or less.

3. The powder according to claim 1 or 2, wherein, the manganese compound is one or more selected from manganese oxide, manganese dioxide, manganese sesquioxide, and manganese tetroxide.

4. The powder according to any one of claims 1 to 3, wherein, the alumina is at least one of a sol of alumina and a powder of alumina.

5. The powder according to any one of claims 1 to 4, wherein The mass ratio of the alumina in terms of Al2O3 to the manganese compound in terms of Mn3O4 is 0.1 or more.

6. The powder according to any one of claims 1 to 5, wherein, The crystal phase of zirconia includes monoclinic zirconia and tetragonal zirconia.

7. The powder according to claim 6, wherein The ratio of the crystallite diameter of monoclinic zirconia to the crystallite diameter of tetragonal zirconia is 0.7 or more and 1.2 or less.

8. The powder according to any one of claims 1 to 7, wherein, The median particle size of the powder is 0.1 μm or more and 1.0 μm or less.

9. The powder according to any one of claims 1 to 8, wherein, The volume particle size distribution curve of the powder is a multimodal distribution.

10. The powder according to any one of claims 1 to 9, wherein, After filling 3 ± 0.3 g of the said powder into a mold with a diameter of 25 mm, and repeatedly performing uniaxial pressing at a pressure of 70 ± 5 MPa and CIP treatment at a pressure of 196 ± 5 MPa to produce 5 compacts, when the atmospheric atmosphere, heating rate is 100 °C / hour, and the holding time at the sintering temperature is set to 2 hours, and normal pressure sintering is carried out on 1 compact at each of the sintering temperatures of 1200 °C, 1250 °C, 1300 °C, 1350 °C, and 1400 °C, the difference between the maximum value and the minimum value of the brightness L * of the 5 sintered compacts obtained is 1.4 or less.

11. A method for manufacturing a sintered body, characterized in that, There is a step of subjecting a compact containing the powder according to any one of claims 1 to 10 to atmospheric pressure sintering at a temperature of 1200 °C or higher and 1400 °C or lower.

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