Sintered body and method for manufacturing same

Abstract

Provided is at least one of: a sintered body that, without requiring usage of additive components, exhibits a fracture toughness value exceeding 10 MPa·m1 / 2 as measured by using an SEPB method; and a method for manufacturing the same. The sintered body is an yttrium-stabilized zirconia sintered body having an yttrium content of 2.0 mol% or less in terms of Y2O3 and having an average crystal grain size of 150 to 270 nm, and the ratio of the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia is 0.8 or greater.

Description

Sintered body and method for manufacturing the same

[0001] This disclosure relates to a sintered zirconia body and a method for manufacturing the same.

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

[0003] For example, Patent Document 1 describes a sintered body containing large amounts of multiple additive components other than zirconia, such as phosphorus, silicon dioxide, and alumina, which has a fracture toughness value of 11 MPa·m measured in accordance with JIS R 1607. １／２ This has been disclosed. However, JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method, and Patent Document 1 does not specify which measurement method was used to obtain the value.

[0004] Furthermore, Patent Document 2 describes a material containing germanium oxide and alumina, with a fracture toughness value of 10.3 to 12.8 MPa·m. １／２ A sintered body is disclosed.

[0005] On the other hand, Patent Document 3 describes a sintered zirconia body containing 1% by mass of alumina and 1.6 mol% of yttria as additive components, which has a fracture toughness value of 10.3 MPa·m measured by the SEPB method. １／２ It has been disclosed that...

[0006] Japanese Patent Publication No. 2011-178610, Japanese Patent Publication No. 2023-097434, Japanese Patent Publication No. 2022-008052

[0007] Patent Document 2 states that the fracture toughness value measured by the SEPB method is 10 MPa·m １／２ A sintered body exceeding [a certain value] is disclosed. At the same time, it is disclosed that a sintered body in which the only additive component is germanium oxide has a significantly reduced fracture toughness value (Example 1). Similarly, Patent Document 3 also discloses a fracture toughness value of 10 MPa·m １／２Sintered bodies exceeding [a certain value] contain alumina, but the fracture toughness value of sintered bodies not containing alumina was significantly reduced to 6.5 MPa·m ０．５ (Example 7). Thus, conventional sintered bodies reported as high-toughness zirconia achieved a fracture toughness value measured by the SEPB method exceeding 10 MPa·m by making the inclusion of additive components essential. １／２

[0008] In the present disclosure, an object is to provide at least either a sintered body showing a fracture toughness value measured by the SEPB method exceeding 10 MPa·m without making the use of additive components essential, and a manufacturing method thereof. １／２

[0009] In the present disclosure, the improvement of the fracture toughness value of a sintered body of zirconia due to an action different from the effect of additive components was investigated. As a result, it was found that by controlling the structure of zirconia in the sintered body, the fracture toughness value of zirconia can be further improved, and it was confirmed that a sintered body having such an action cannot be obtained from conventional raw materials used as sintered body raw materials. A sintering mechanism different from the conventional one and raw materials suitable therefor were found, and as a result, it was found that a sintered body in which the fracture toughness value of zirconia can be further improved can be realized regardless of the effect of additive components.

[0010] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows.

[0011] [1] Y ２ O ３ ​​[1] A sintered body of yttrium-stabilized zirconia having a converted yttrium content of 2.0 mol% or less, an average crystal grain size of 150 nm to 270 nm, and a 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 of 0.8 or more. [2] The sintered body according to [1] above, having a relative density of 99.5% or more. [3] The sintered body according to [1] or [2] above, containing at least one of alumina and silica as additive components. [4] The sintered body according to [3] above, having a content of the additive component of 5.0 mass% or less. [5] A fracture toughness value of 10.5 Pa·m as measured by a method conforming to the SEPB method specified in JIS R1607. ０．５ The above is a sintered body according to any one of [1] to [4] above. [6] Contains a yttrium source and monoclinic zirconia, and has a BET specific surface area of ​​80 m². ２ / g or more 200m ２ A method for producing a sintered body according to any one of [1] to [5] above, comprising sintering a molded body of zirconia made from raw material powder having a density of 0 / g or less to obtain a pre-sintered body with a relative density of 93% to 99%, and pressurizing the pre-sintered body. [7] A component comprising the sintered body according to any one of [1] to [5] above.

[0012] This disclosure makes it possible to achieve 10 MPa·m without requiring the use of additive components. １／２ It is possible to provide at least one of the following: a sintered body exhibiting a fracture toughness value measured by the SEPB method exceeding [value], and a method for manufacturing the same.

[0013] The following description illustrates an example of this disclosure. This disclosure includes any combination of the configurations and numerical values ​​disclosed herein, as well as any combination of the upper and lower limits disclosed herein.

[0014] "Relative density" is the ratio (%) of the measured density to the true density. The measured density of a molded body is the ratio of the mass measured by mass measurement to the volume obtained from dimensional measurement (g / cm³). ３The measured density of the sintered body is the ratio of mass to volume measured by mass measurement (g / cm³) as measured by the Archimedes method. ３ The true density is calculated from the following equations (1) to (4) (g / cm³). ３ )

[0015] A=0.5080+0.06980X / (100+X) (1) C=0.5195-0.06180X / (100+X) (2) ρ Ｚ = [124.25(100-X)+225.81X] / [150.5(100+X)A ２ C] (3) ρ ０ = 100 / [(Y Ａ ( / 3.987) + (Y Ｓ / 2.2) + (100 - Y Ａ -Y Ｓ ) / ρ Ｚ ] (4)

[0016] In equations (1) to (4), ρ ０ The true density of the sintered body is ρ Ｚ is the true density of zirconia containing yttrium, A and C are constants, and X is zirconia (ZrO ２ ) and the stabilizing element in terms of oxide (for example, if the stabilizing element is yttrium (Y), then yttria (Y) ２ O ３ The molar ratio (mol%) of the stabilizing element in terms of oxides relative to the total of )), and Y Ａ and Y Ｓ Zirconia, yttrium, aluminum, and silicon are each represented by ZrO ２ Y converted to oxide ２ O ３ Al ２ O ３ and SiO ２ For the converted total, ２ O ３ Converted alumina and SiO ２ This is the converted mass percentage (mass%) of silicon.

[0017] The "monoclinic ratio" is the proportion of monoclinic zirconia in the crystalline phase of zirconia. 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. 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 mirror-polished sintered body (hereinafter also referred to as "mirror-polished sintered body") is used. The monoclinic ratio can be determined from the following formula (5), and the monoclinic intensity ratio from the following formula (6).

[0018] f ｍ = {I ｍ (111) + I ｍ (11-1)} / [I ｍ (111) + I ｍ (11-1) + I ｔ (111)]×100 (5) M （１１－１）／（１１１） = {I ｍ (11-1) / I ｍ (111)} (6)

[0019] In equations (5) and (6), f ｍ This is the monoclinic ratio (%), M （１１－１）／（１１１） This is the monoclinic intensity ratio, I ｍ (111) and I ｍ (11-1) represents the area intensity of the XRD peaks corresponding to the (111) plane and (11-1) plane of monoclinic zirconia, respectively. ｔ (111) represents the area intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia.

[0020] The following conditions can be used for measuring the XRD pattern: Radiation source: CuKα line (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 4° / min Step size: 0.01° Measurement range: 2θ = 26° to 33°

[0021] In the XRD pattern measurement described above, preferably, the XRD peaks corresponding to each crystal plane of zirconia are measured as peaks having a peak top at the following 2θ.

[0022] 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° XRD peak corresponding to the (111) plane of tetragonal zirconia: 2θ = 30 ± 0.5°

[0023] The area intensity of the XRD peaks on each crystal plane can be determined by separating each XRD peak using calculation software (for example, SmartLab Studio II, manufactured by Rigaku Corporation).

[0024] The "mirror-finish sintered body" used for the above-mentioned XRD measurement is a sintered body with a surface roughness Ra of 0.04 μm or less, which is achieved by first grinding the surface after sintering using a surface grinding machine, followed by automatic polishing with abrasive cloth and paper, automatic polishing with a diamond slurry with an average particle size of 3 μm, and automatic polishing with colloidal silica with an average particle size of 0.03 μm.

[0025] "Cryslite size of monoclinic zirconia in powder" (hereinafter referred to as "D ｍ It is also called ). ) is a value obtained from the XRD pattern of the powder using the following formula (7). D ｍ = κλ / (βcosθ) ｍ ) (7)

[0026] In equation (7), D ｍ θ is the crystallite size of monoclinic zirconia (nm), κ is the Scherrer constant (κ = 1), λ is the wavelength of the radiation source used for XRD measurement (nm), β is the full width at half maximum (°) after correcting for mechanical spreading using quartz sand with a grain size of 25-90 μm (e.g., manufactured by Wako Pure Chemical Industries, Ltd.), and θ is the full width at half maximum (°). ｍ This represents the Black angle (°) of the reflection corresponding to the (11-1) plane of monoclinic zirconia in XRD measurements, and θ ｔ This is the Black angle (°) of the reflection corresponding to the (111) plane of tetragonal zirconia in XRD measurements.

[0027] When CuKα radiation is used as the source for XRD measurements, λ is 0.15418 nm.

[0028] The "average grain size" can be determined by the planimetric method using the SEM (Scanning Electron Microscope) image of a sintered sample obtained by field emission scanning electron microscopy. Specifically, a circle with diameter φ is drawn on the SEM image, the number of crystal particles (Nc) within the circle and the number of crystal particles (Ni) on the circumference of the circle are measured, and the value is obtained using equation (8): D = (φ / M) / (Nc + Ni / 2) １／２ (8)

[0029] In the above equation, D is the average grain size, Nc is the number of crystal grains within the circle, Ni is the number of crystal grains on the circumference of the circle, φ is the diameter of the circle, and M is the magnification of the scanning electron microscope observation.

[0030] The average grain size can be determined as the particle size obtained for a number of crystal particles (Nc + Ni) of 750 ± 250. If the number of crystal particles (Nc + Ni) in a single SEM observation image is less than 500, then SEM observation images measured in multiple fields of view should be used to obtain (Nc + Ni) of 500 or more, preferably 750 ± 250, and D should be calculated for each SEM observation image. The average value of the obtained D values ​​should be taken, and this value should be determined as the average grain size.

[0031] "BET specific surface area" is calculated according to JIS R 1626-1996, with the adsorbed substance being nitrogen (N ２ This value is obtained by the BET single-point method. Prior to measurement, the sample should be pretreated by degassing it in an air atmosphere at 250°C for 30 minutes.

[0032] The "fracture toughness value" is the value of fracture toughness (MPa·m) measured by a method conforming to the SEPB method specified in JIS R 1607. ０．５) The measurement is performed using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements can be used as the fracture toughness value in this embodiment. Note that JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method. The IF method tends to produce larger values ​​than the SEPB method. Furthermore, because the IF method is a simple measurement method, there is a large variation in the measured values ​​from one measurement to the next. Therefore, the fracture toughness value in this embodiment and the fracture toughness value measured by the IF method cannot be compared in absolute terms. Similarly, the fracture toughness value measured by a method other than the SEPB method cannot be compared in absolute terms with the fracture toughness value measured by the SEPB method.

[0033] "Bending strength" refers to the value of the three-point bending strength obtained by a three-point bending test in accordance with JIS R 1601. The bending strength is measured using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements should be used as the bending strength of the sintered body sample.

[0034] [Sintered body] The sintered body of this embodiment will be described below.

[0035] This embodiment is Y ２ O ３ This is a sintered body of yttrium-stabilized zirconia in which the converted yttrium content is 2.0 mol% or less, the average crystal grain size is 150 nm to 270 nm, and 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 (i.e., the "monoclinic intensity ratio") is 0.8 or more. As a result, without requiring additive components such as alumina, the fracture toughness value is 10 MPa·m ０．５ A sintered body with a fracture toughness value exceeding that of the specified value, a so-called high-toughness zirconia sintered body, can be obtained.

[0036] One possible reason why the sintered body of this embodiment exhibits high fracture toughness is as follows: In this embodiment, the yttrium content is relatively low and the monoclinic intensity ratio is relatively high, which makes it easier for stress-induced phase transformation from tetragonal to monoclinic (hereinafter also referred to as "stress-induced phase transformation") to occur. As a result, the fracture energy generated by external stress is efficiently absorbed by this stress-induced phase transformation, and it is thought that crack propagation is significantly suppressed. Furthermore, in this embodiment, the problem of reduced fracture toughness caused by the relatively low yttrium content and relatively high monoclinic intensity ratio, namely the ease with which spontaneous phase transformation from tetragonal to monoclinic (hereinafter also referred to as "spontaneous phase transformation") occurs, is suppressed by an appropriate average grain size. In contrast, in sintered bodies with yttrium content (3 mol% to 6 mol%), which is generally considered to have high fracture toughness, stress-induced phase transformation is less likely to occur. This makes crack formation and propagation more likely, so it is thought that there was a limit to the upper limit of the fracture toughness value.

[0037] The sintered body of this embodiment is a sintered body with zirconia as the main phase, a so-called zirconia sintered body, and more particularly, a sintered body with yttrium-stabilized zirconia as the main phase. Therefore, the sintered body of this embodiment may be a sintered body made of yttrium-stabilized zirconia.

[0038] Yttrium-stabilized zirconia is zirconia (ZrO ２ This is zirconia in which the crystalline phase is stabilized by the solid solution of yttrium.

[0039] The sintered body of this embodiment is Y ２ O ３The converted yttrium content (hereinafter also referred to as "yttrium amount") is 2.0 mol% or less. If the yttrium amount exceeds 2.0 mol%, stress-induced phase transformation from tetragonal to monoclinic is less likely to occur, and the fracture toughness value decreases. To easily exhibit a high fracture toughness value, the yttrium amount is preferably 2.0 mol% or less, 1.8 mol% or less, or 1.5 mol% or less. Furthermore, to easily increase mechanical strength, the yttrium amount is preferably 1.0 mol% or more, 1.1 mol% or more, or 1.2 mol% or more. In this embodiment, the yttrium amount of the sintered body can be 1.0 mol% or more and 2.0 mol% or less, 1.1 mol% or more and 1.8 mol% or less, 1.1 mol% or more and 1.5 mol% or less, or 1.2 mol% or more.

[0040] In this embodiment, the amount of yttrium is zirconia (ZrO ２ ) and Y ２ O ３ Y for the total converted yttrium ２ O ３ This is the molar percentage [mol%] of yttrium after conversion.

[0041] In the sintered body of this embodiment, yttrium is solid-dissolved in zirconia. Preferably, the sintered body of this embodiment does not contain undissolved yttrium, that is, all of the yttrium is solid-dissolved in zirconia. However, it may contain undissolved yttrium as long as it is within the range that the effects of the sintered body of this embodiment are achieved.

[0042] In the sintered body of this embodiment, if no XRD peak of a yttrium compound is detected in its XRD peak, it can be considered that it does not contain undissolved yttrium.

[0043] The sintered body of this embodiment exhibits high fracture toughness without the effect of additive components. Therefore, the sintered body of this embodiment does not need to contain additive components (the content of additive components may be 0% by mass). However, it may contain additive components as long as it is within the range that the effects of the sintered body of this embodiment are achieved (the content of additive components may be greater than 0% by mass). This makes it possible to obtain not only the effects of the sintered body of this embodiment itself, but also the effect of improving fracture toughness due to additive components.

[0044] The additive components in this embodiment include one or more selected from alumina and silica, and more particularly alumina.

[0045] In the sintered body of this embodiment, it is preferable that the content of additive components is small. For example, the content of additive components on an oxide basis (hereinafter also referred to as "amount of additive components," and if the additive component is alumina, it is also referred to as "alumina amount," etc.) may be 5.0% by mass or less, 3.0% by mass or less, or 1.5% by mass or less. Furthermore, if the sintered body of this embodiment contains additive components, the amount of additive components may be greater than 0% by mass, 0.1% by mass or more, or 0.3% by mass or more. Examples of the amount of additive components in the sintered body of this embodiment include 0% by mass or more and 5.0% by mass or less, 0% by mass or more and 3.0% by mass or less, or 0% by mass or more and 1.5% by mass or less. Furthermore, the sintered body of this embodiment contains additive components, and the amount of additive components may be greater than 0% by mass and 5.0% by mass or less, 0.1% by mass or more and 3.0% by mass or less, or 0.3% by mass or more and 1.5% by mass or less.

[0046] In this embodiment, the amount of added component is zirconia (ZrO ２ ), Y ２ O ３ This is the mass percentage [mass%] of the oxide-converted additive components to the total of the converted yttrium and oxide-converted additive components. The oxide conversion of each additive component is as follows: alumina is Al ２ O ３ and silica is SiO ２ That is the case.

[0047] The sintered body of this embodiment preferably contains no impurities, and preferably has a content below the detection limit (for example, 0.1% by mass) or less. For example, it can be exemplified that the content of phosphorus (P) as an impurity is 0.1% by mass or less, and further less than 0.1% by mass. Also, it can be exemplified that the content of metal elements other than zirconia, alumina, silica, and yttrium is less than 0.1% by mass. On the other hand, it may contain unavoidable impurities such as hafnia (HfO ２ ). In calculating values related to the composition such as density in this embodiment, hafnia (HfO ２ ), it may be calculated by considering it as zirconia (ZrO ２ ).

[0048] When the sintered body of this embodiment is, for example, a sintered body of yttrium-stabilized zirconia containing alumina and silica, its composition may be determined as follows.

[0049] Content of stabilizing element (yttrium amount) = {Y ２ O ３ / (ZrO ２ + Y ２ O ３ )} × 100 [mol%] Content of alumina (alumina amount) = {Al ２ O ３ / (ZrO ２ + Y ２ O ３ + Al ２ O ３ + SiO ２ )} × 100 [mass%] Content of silica (silica amount) = {SiO ２ / (ZrO ２ + Y ２ O ３ + Al ２ O ３ + SiO ２ )} × 100 [mass%] Content of additive component (additive component amount) = { (Al ２ O ３ + SiO ２ ) / (ZrO ２ + Y ２ O ３ + Al ２ O ３ + SiO２ )}×100 [mass%]

[0050] In the sintered body of this embodiment, the crystalline phase of zirconia includes at least monoclinic zirconia and tetragonal zirconia, preferably consisting of monoclinic zirconia and at least one of tetragonal zirconia and cubic zirconia, and preferably consisting of monoclinic zirconia and tetragonal zirconia. Although zirconia is said to have multiple crystalline phases, in this embodiment, the crystalline phase of zirconia can be considered to consist of three crystalline phases: monoclinic zirconia, tetragonal zirconia, and cubic zirconia.

[0051] In this embodiment, 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 sintered body (hereinafter also referred to as the "monoclinic intensity ratio") is 0.8 or higher, and preferably 1.2 or higher, 1.4 or higher, or 1.5 or higher. Including monoclinic zirconia having such a monoclinic intensity ratio makes it easier for the sintered body to exhibit a high fracture toughness value. Examples of monoclinic intensity ratios in this embodiment include an upper limit of 3.0 or less, 2.0 or less, 1.8 or less, or 1.7 or less, and examples of monoclinic intensity ratios in this embodiment include 0.8 or more and 3.0 or less, 1.2 or more and 2.0 or less, 1.4 or more and 1.8 or less, or 1.5 or more and 1.7 or less.

[0052] In this embodiment, the monoclinic intensity ratio is a value obtained from equation (6) for the XRD pattern obtained by measuring the XRD pattern as described above. Note that in sintered bodies that do not have XRD peaks corresponding to the monoclinic zirconia (111) plane, the monoclinic intensity ratio becomes infinite, and the value cannot be determined. The sintered body of this embodiment contains at least monoclinic zirconia, and in this case, the monoclinic intensity ratio is not infinite.

[0053] The monoclinic content of the sintered body of this embodiment can be any value as long as it satisfies the monoclinic intensity ratio described above. Examples of monoclinic content of the sintered body of this embodiment include 3.0% or more, 5.0% or more, or 6.0% or more, and also 15.0% or less, 10.0% or less, or 9.0% or less. Examples of monoclinic content of the sintered body of this embodiment include 3.0% or more and 15.0% or less, 5.0% or more and 10.0% or less, or 6.0% or more and 9.0% or less.

[0054] In this embodiment, the average grain size of the zirconia crystal grains in the sintered body is 270 nm or less, preferably 260 nm or less, 255 nm or less, or 235 nm or less. If the average grain size exceeds 270 nm, a high fracture toughness value cannot be obtained even if the above-mentioned monoclinic intensity ratio is satisfied. Mechanical strength tends to increase as the average grain size decreases, but the lower limit of the average grain size of the sintered body in this embodiment can be 150 nm or more, 200 nm or more, or 210 nm or more. In this embodiment, the average grain size can be 150 nm or more and 270 nm or less, 200 nm or more and 255 nm or less, or 210 nm or more and 235 nm or less.

[0055] The sintered body of this embodiment is preferably dense because it tends to have high mechanical strength. The sintered body of this embodiment is preferably 99.0% or more, 99.5% or more, or 99.7% or more in relative density, and may also be 100% or less, or 99.9% or less.

[0056] The sintered body of this embodiment is preferably a sintered body obtained by pressure sintering (i.e., a pressure sintered body), and more preferably a sintered body obtained by hot hydrostatic pressing (hereinafter also referred to as "HIP") (a so-called HIP-treated body). The HIP-treated body may be a body that has been treated by another sintering method after pressure sintering, for example, atmospheric pressure sintering after pressure sintering, or a body that has been sintered in an oxidizing atmosphere after HIP treatment.

[0057] The shape of the sintered body in this embodiment can be any desired shape, including cubic, rectangular, polygonal, plate-shaped, disc-shaped, columnar, conical, spherical, approximately spherical, and other basic shapes, as well as any shape suitable for various applications.

[0058] The sintered body of this embodiment has high fracture toughness, and the fracture toughness value measured by the method conforming to the SEPB method specified in JIS R1607 is 10.5 Pa·m. ０．５ Above, 11 Pa・m ０．５ Above or above 12 Pa·m ０．５ The above points are listed above. A high fracture toughness value is preferable, but its upper limit is 15 MPa·m. ０．５ The following or 14 MPa·m ０．５ The following are some examples, and the fracture toughness value of the sintered body in this embodiment is 10.5 Pa·m. ０．５ 15MPa・m or more ０．５ Below, 11 Pa・m ０．５ 15MPa・m or more ０．５ The following, or 12 Pa·m ０．５ 14MPa・m or more ０．５ The following are examples. The bending strength of the sintered body of this embodiment is not particularly limited, but it is preferable that the bending strength determined by a three-point bending test in accordance with JIS R 1601 is 900 MPa or more, 950 MPa or more, or 970 MPa or more, and also preferable that it is 1200 MPa or less, 1150 MPa or less, or 1050 MPa or less. Examples of the bending strength of the sintered body of this embodiment include 900 MPa or more and 1200 MPa or less, 950 MPa or more and 1150 MPa or less, or 970 MPa or more and 1050 MPa or less.

[0059] The sintered body of this embodiment can be used as a component in applications known for zirconia sintered bodies, for example, as one or more selected from the group consisting of structural materials, biomaterials, and exterior materials, and further as one or more selected from the group consisting of crusher components, precision machine components, optical connector components, decorative components, electronic equipment exterior components, and dental components.

[0060] [Method for Manufacturing a Sintered Body] The method for manufacturing the sintered body of this embodiment is arbitrary as long as a sintered body satisfying the above-described configuration can be obtained. A preferred method for manufacturing the sintered body of this embodiment is to include a zirconia source and a yttrium source different from the zirconium source, and also Y ２ O ３The converted yttrium content is 2.0 mol% or less, and the BET specific surface area is 80 m². ２ One example is a manufacturing method (hereinafter also referred to as "the manufacturing method of this embodiment") that includes a pre-sintering step of sintering a molded body of zirconia made from raw material powder having a concentration of 1 / g or more at atmospheric pressure to obtain a pre-sintered body, and a pressure sintering step of pressurizing the pre-sintered body.

[0061] The molding process includes a zirconia source and a yttrium source different from the zirconia source, and also Y ２ O ３ The converted yttrium content is 2.0 mol% or less, and the BET specific surface area is 80 m². ２ A molded zirconia body made from raw material powder with a concentration of 1 / g or more is provided.

[0062] The yttrium source contained in the raw material powder may be at least one of yttrium compounds and their precursors, for example, one or more selected from the group consisting of yttrium chloride, yttrium hydroxide, and yttrium oxide (yttria), with at least one of yttrium hydroxide and yttrium oxide being preferred, and yttrium hydroxide being preferred.

[0063] The zirconia source contained in the raw material powder is zirconia (ZrO ２ It may be at least one of ) and its precursor, but hydrated zirconia powder is preferred. Hydrated zirconia powder is hydrated zirconia (ZrO ２ nH ２ Hydrated zirconia is a powder consisting of particles of size O (where n is a real number), and it is a hydrated form of zirconia. Hydrated zirconia can be removed by heat treatment at temperatures above 900°C.

[0064] The raw material powder contains a zirconia source and a yttrium source different from the zirconia source. Thus, the raw material powder contains a yttrium source and a zirconia source, respectively, and the yttrium source and the zirconia source are different compounds. In other words, the raw material powder contains at least zirconia and its precursors, and a yttrium compound that is not solid-dissolved in the zirconia, etc. By pre-sintering a molded body (compacted powder) obtained by molding such a raw material powder, densification proceeds not only by ion diffusion of zirconium and oxygen, but also by sintering accompanied by a solid-solution reaction of yttrium into zirconia in addition to ion diffusion, i.e., reactive sintering and the densification that results therefrom. This prevents excessive growth of crystal grains in the subsequent pressure sintering, and yields the sintered body of this embodiment having the monoclinic intensity ratio described above.

[0065] The raw material powder may contain yttrium as long as it contains a yttrium source as a compound different from the zirconia source. The raw material powder may, for example, contain a yttrium compound and hydrated yttrium-stabilized zirconia powder, or it may contain a yttrium compound and hydrated zirconia powder. Preferably, the raw material powder contains yttrium hydroxide and hydrated zirconia powder.

[0066] Y of raw material powder ２ O ３ The converted yttrium content (yttrium amount) should be the same as the yttrium amount of the target sintered body, preferably 2.0 mol% or less, 1.8 mol% or less, or 1.5 mol% or less, and preferably 1.0 mol% or more, 1.1 mol% or more, or 1.2 mol% or more. Furthermore, the yttrium amount can be 1.0 mol% or more and 2.0 mol% or less, 1.1 mol% or more and 1.8 mol% or less, 1.1 mol% or more and 1.5 mol% or less, or 1.2 mol% or more and 1.5 mol% or less.

[0067] The raw material powder does not have to contain additives (the content of additives may be 0% by mass), but depending on the composition of the target sintered body, the raw material powder may contain additives (one or more selected from alumina and silica, and more specifically, alumina) (the content of additives may be greater than 0% by mass). Examples of additive amounts in the raw material powder include 5.0% by mass or less, 3.0% by mass or less, or 1.5% by mass or less. Furthermore, if the raw material powder contains additives, examples of additive amounts include greater than 0% by mass, 0.1% by mass or more, or 0.3% by mass or more. Examples of additive amounts in the raw material powder include 0% by mass or more and 5.0% by mass or less, 0% by mass or more and 3.0% by mass or less, or 0% by mass or more and 1.5% by mass or less. Furthermore, if the raw material powder contains additives, examples of additive amounts include greater than 0% by mass and 5.0% by mass or less, 0.1% by mass or more and 3.0% by mass or less, or 0.3% by mass or more and 1.5% by mass or less.

[0068] The BET specific surface area of ​​the raw material powder is 80 m². ２ It is 120m or more per gram. ２ / g or more, 150m ２ / g or more, or 160m ２ It is preferable that the amount is 1 / g or more. The BET specific surface area is 80 m². ２ If the amount is less than / g, the solid solution reaction of yttrium to zirconia during presintering may not proceed sufficiently, or the yttrium may become non-uniform, making it difficult to obtain the sintered body of this embodiment. To improve moldability, the BET specific surface area is 200 m². ２ / g or less or 180m ２ It is sufficient if it is less than / g, 80m ２ / g or more 200m ２ / g or less, 150m ２ / g or more 200m ２ / g or less, or 160m ２ / g or more 180m ２ One example is that it should be less than or equal to / g.

[0069] The raw material powder can have any size of primary particles as long as it has the BET specific surface area described above. Preferably, the average primary particle diameter of the raw material powder is 100 nm or more, 150 nm or more, or 160 nm or more. The average primary particle diameter of the raw material powder can be 300 nm or less, 250 nm or less, or 180 nm or less, and preferably 100 nm to 300 nm, 150 nm to 180 nm, or 160 nm to 180 nm. By controlling the average primary particle diameter of the raw material powder, the average crystal grain size of the resulting sintered body can be controlled; that is, by making the average primary particle diameter of the raw material powder relatively small, the average crystal grain size of the resulting sintered body can be made relatively small.

[0070] The raw material powder has a median diameter (D ５０ The midpoint may be 500 nm or less, 400 nm or less, 300 nm or less, or 200 nm or less, and may also be 50 nm or more, 100 nm or more, 120 nm or more, or 150 nm or more. Furthermore, the median diameter may be 50 nm or more and 500 nm or less, 100 nm or more and 400 nm or less, 120 nm or more and 300 nm or less, or 150 nm or more and 200 nm or less.

[0071] The median diameter is determined by measuring the volume particle size distribution curve of a powder sample using the MT3000II mode of a Microtrac particle size distribution analyzer (product name: MT3000II, manufactured by Microtrac-Bell). The median diameter (D) is defined as the particle size at which the cumulative volume frequency of the smallest particle size reaches 50%. ５０ ) is sufficient. Alternatively, prior to measurement, the powder sample can be suspended in a 0.2% by mass sodium hexametaphosphate aqueous solution and dispersed for 10 minutes using an ultrasonic homogenizer as a pretreatment.

[0072] The raw material powder is monoclinic zirconia with a crystallite size (D ｍIt is preferable that the crystallite size of the monoclinic zirconia is 20 nm or less, 10 nm or less, or 5 nm or less. It is thought that a fine crystallite size of monoclinic zirconia allows for a larger monoclinic intensity ratio in the resulting sintered body, thereby allowing fracture energy to be absorbed more efficiently in the sintered body obtained after pressure sintering, and thus making it easier to improve the fracture toughness value. A smaller crystallite size of monoclinic zirconia is preferable, however D ｍ The wavelength may be 1 nm or more, or 2 nm or more, or 1 nm to 20 nm, or 2 nm to 10 nm.

[0073] The raw material powder may also be in granular form.

[0074] The raw material powder is preferably a powder obtained by the manufacturing method described later.

[0075] The molded body can be any composition (compacted powder) in which the raw material powder, that is, the powder particles constituting the raw material powder, are aggregated to have a certain shape, and can be any molded body manufactured by any molding method that does not cause changes in the composition of the raw material composition, BET specific surface area, average primary particle diameter, etc. The molding method can be one or more selected from the group consisting of uniaxial press molding, cold isostatic press (CIP) molding, slip casting, and injection molding, and more specifically, at least one selected from the group consisting of uniaxial press molding, CIP molding, and injection molding, with uniaxial press molding and CIP molding being preferred.

[0076] When the molding method is uniaxial press forming and CIP forming, it is preferable that the ratio of the uniaxial press forming pressure [MPa] to the CIP forming pressure [MPa] is 0.25 or less, more preferably 0.05 to 0.25, more preferably 0.15 to less than 0.25, and more preferably 0.20 to less than 0.25, and more preferably the CIP forming pressure is 200 MPa or more, and more preferably greater than 250 MPa. The upper limit of the CIP forming pressure can be 1 GPa or less, 500 MPa or less, 350 MPa or less, or 300 MPa or less, and it is preferable that it is 200 MPa to 350 MPa, or greater than 250 MPa and less than or equal to 300 MPa.

[0077] Compared to powders commonly used as raw materials for sintered bodies, the raw material powder has a higher BET specific surface area. Powders with a high BET specific surface area are difficult to mold even if molded at high pressure. However, because the raw material powder contains an undissolved yttrium source, by controlling the relationship between the pressure of uniaxial press molding and the pressure of CIP molding within this range, the raw material powder can be molded into a compact (molded body) despite its high BET specific surface area.

[0078] While the pressure for uniaxial press forming can be any pressure as long as the above-described relationship is satisfied between the pressure for uniaxial press forming and the pressure for CIP forming, it is preferable that the pressure be 50 MPa or higher, more preferably 65 MPa or higher, and also 90 MPa or lower, or 80 MPa or lower, in order to improve handling after uniaxial press forming. Examples include 50 MPa to 90 MPa or 65 MPa to 80 MPa.

[0079] The molded body is subjected to a pre-sintering process. The sintering in the pre-sintering process should be such that a pre-sintered body that can be densified in the subsequent pressure sintering is obtained, and atmospheric pressure sintering is preferred. In this embodiment, "atmospheric pressure sintering" refers to a method of sintering a material (such as a molded body or calcined body) by heating it at a temperature above the temperature at which zirconia sintering progresses (hereinafter also referred to as the "sintering temperature") without applying any external force to the material to be sintered during sintering. Preferred conditions for atmospheric pressure sintering include the following conditions.

[0080] Atmosphere: Oxidizing atmosphere, preferably atmospheric atmosphere. Holding temperature: 1100°C or higher or 1200°C or higher, and 1300°C or lower or 1250°C or lower.

[0081] The pre-sintering time can be appropriately adjusted depending on the size and quantity of the molded body to be pre-sintered, as well as the sintering furnace used. For example, it can be 0.5 hours or more and 24 hours or more, or 1 hour or more and 15 hours or less. To promote densification by pressure sintering, the relative density of the resulting pre-sintered body is preferably 93% or more, 94% or more, or 95% or more, and also preferably 99% or less, 98% or less, or 97% or less. A density of 93% to 99% or 94% to 98% for the pre-sintered body, and moreover, 95% to 97%, tends to result in a higher relative density of the sintered body obtained after pressure sintering.

[0082] In the pressure sintering process, the pre-sintered body is pressure-sintered. This makes it possible to manufacture the sintered body of this embodiment.

[0083] Pressure sintering includes at least one of hot press (HP) treatment and hot isostatic press (HIP) treatment, with HIP treatment being preferred.

[0084] The following conditions can be cited as requirements for pressure sintering.

[0085] Atmosphere: Reducing atmosphere, preferably at least one of nitrogen and argon atmospheres, more preferably argon atmosphere Holding pressure: 50 MPa or more or 100 MPa or more, and 500 MPa or less or 200 MPa or less Holding temperature: 1100°C or more, 1150°C or more or 1230°C or more, and 1350°C or less, 1300°C or less or 1270°C or less

[0086] The holding temperature during pressurized sintering is preferably higher than the holding temperature during pre-sintering, and more preferably 50 ± 10°C higher than the holding temperature during pre-sintering.

[0087] The time for pressurized sintering can be adjusted as appropriate depending on the size and quantity of the pre-sintered body to be subjected to pressurized sintering, as well as the pressurized sintering furnace used. For example, it can be between 0.5 hours and 15 hours, or between 0.5 hours and 5 hours.

[0088] [Method for Manufacturing Raw Material Powder] The raw material powder used in the molding process is a powder for sintered bodies, and is a powder for making molded bodies, a powder for making calcined bodies, or a powder for making sintered bodies, and is a powder that becomes one or more precursors selected from the group consisting of molded bodies, calcined bodies, and sintered bodies. A preferred method for manufacturing the raw material powder is a method (hereinafter also referred to as "this powder manufacturing method") which includes an alcohol treatment step to obtain a powder precursor by treating a composition (hereinafter also referred to as "raw material composition") having an average sol particle size of 150 nm or more and 400 nm or less with alcohol, and containing hydrated zirconia powder and a yttrium source, with alcohol, and a drying step to dry the powder precursor in a reduced pressure atmosphere.

[0089] A powder precursor is obtained by going through an alcohol treatment process. In the raw material composition subjected to the alcohol treatment process, the yttrium source can be any yttrium compound, and can be one or more selected from the group consisting of yttrium chloride, yttrium hydroxide, and yttrium oxide (yttria), with at least one of yttrium chloride and yttrium hydroxide, and more preferably yttrium chloride.

[0090] In the raw material composition used in the alcohol treatment process, the hydrated zirconia powder consists of hydrated zirconia particles.

[0091] The zirconia sol preferably contains zirconia that includes monoclinic zirconia, and more preferably contains zirconia made of crystalline zirconia (hereinafter also referred to as "crystalline zirconia sol"), and more preferably contains crystalline zirconia in which the main phase is monoclinic zirconia.

[0092] The zirconia sol has an average sol particle size of 150 nm to 400 nm, preferably 200 nm to 300 nm. Such a zirconia sol can be produced, for example, by the method disclosed in Patent Document 3.

[0093] Y in the raw material composition ２ O ３The converted yttrium content (yttrium amount) should be the same as the yttrium amount of the target raw material powder, preferably 2.0 mol% or less, 1.8 mol% or less, or 1.5 mol% or less, and preferably 1.0 mol% or more, 1.1 mol% or more, or 1.2 mol% or more. Furthermore, the yttrium amount may be 1.0 mol% or more and 2.0 mol% or less, 1.1 mol% or more and 1.8 mol% or less, 1.1 mol% or more and 1.5 mol% or less, or 1.2 mol% or more and 1.5 mol% or less.

[0094] The raw material composition does not have to contain additives (i.e., the content of additives may be 0% by mass), but depending on the composition of the target raw material powder, the raw material composition may contain additives (one or more selected from alumina and silica, and more specifically, alumina) (the content of additives may be greater than 0% by mass). Examples of additive amounts in the raw material composition include 5.0% by mass or less, 3.0% by mass or less, or 1.5% by mass or less. Furthermore, if the raw material composition contains additives, examples of additive amounts include greater than 0% by mass, 0.1% by mass or more, or 0.3% by mass or more. Examples of additive amounts in the raw material powder include 0% by mass or more and 5.0% by mass or less, 0% by mass or more and 3.0% by mass or less, or 0% by mass or more and 1.5% by mass or less. Furthermore, the raw material composition contains additives, and examples of additive amounts include greater than 0% by mass and 5.0% by mass or less, 0.1% by mass or more and 3.0% by mass or less, or 0.3% by mass or more and 1.5% by mass or less.

[0095] In the alcohol treatment process, the raw material composition is treated with alcohol. In this embodiment, "alcohol treatment" refers to a process in which the raw material composition is brought into contact with a wet atmosphere using alcohol as a solvent. It is believed that by treating the raw material composition with alcohol, the surface of the raw material composition, particularly the zirconia sol contained in the raw material composition, is modified. As a result, the zirconia sol in the raw material composition becomes moderately and slowly aggregated, and after the subsequent drying process, it is believed that a raw material powder with high moldability despite having a high BET specific surface area can be obtained.

[0096] The alcohol can be one or more selected from methanol, ethanol, butanol, and octanol, and is preferably at least one of methanol and ethanol, and more preferably ethanol.

[0097] The method of alcohol treatment is arbitrary as long as it does not apply excessive stress to the raw material composition and ensures sufficient contact between the raw material composition and the alcohol. For example, the alcohol and raw material composition can be mixed to form a slurry and then stirred. In addition to contact between the alcohol and the raw material composition, the alcohol treatment method may also include a method to remove slow aggregation of the raw material composition. Examples of specific treatment methods include at least one of mortar mixing and ball mill mixing, and mortar mixing is acceptable.

[0098] Examples of slurries used in alcohol treatment include slurries in which the mass ratio of the raw material composition to the total slurry mass is 30% by mass or more and 50% by mass or less.

[0099] In the drying process, the powder precursor is dried under reduced pressure. The powder precursor obtained after the drying process has a high BET specific surface area, making it prone to forming strong aggregates during drying. However, drying under reduced pressure suppresses the aggregation of the powder precursor while drying progresses, resulting in a more moldable raw material powder.

[0100] A reduced pressure atmosphere is an atmosphere with lower pressure than the atmospheric atmosphere, and may be 0.1 MPa or less, 500 hPa or less, or 200 hPa or less. To achieve an appropriate drying rate, the reduced pressure atmosphere is preferably 50 hPa or more or 100 hPa or more, and preferred reduced pressure atmospheres include 50 hPa or more and 0.1 MPa or less, or 100 hPa or more and 200 hPa or less.

[0101] The drying temperature should be a temperature at which rapid evaporation of the solvent, ethanol, is unlikely to occur, and is preferably 80°C or lower, 60°C or lower, or 50°C or lower. The drying temperature should be 20°C or higher or 30°C or higher, and may also be 20°C to 60°C or 30°C to 50°C.

[0102] To improve the handling properties of the raw material powder, this powder manufacturing method may include a granulation step in which the raw material powder obtained by the drying step is granulated.

[0103] Granulation can be carried out by any method, but one method is spray granulation of a slurry obtained by mixing powder and a solvent. The solvent is at least one of water and alcohol. The granulated powder (hereinafter also referred to as "powder granules") has an average granule size of 30 μm or more and 80 μm or less.

[0104] The present disclosure will be described below using examples. However, the present disclosure is not limited to these examples.

[0105] (Average sol particle size) The average sol particle size of the zirconia sol was measured using a dynamic light scattering particle size distribution analyzer (instrument name: NANOTRAC WAVE II, manufactured by Microtrac). As a sample pretreatment, the hydrated zirconia sol-containing solution was suspended in pure water, and the suspension was dispersed for 1 minute using an ultrasonic cleaner.

[0106] (Monoclinic fraction of powder and crystallite size of monoclinic zirconia) An XRD pattern of the powder sample was obtained using a general X-ray diffractometer (instrument name: SmartLab, manufactured by Rigaku Corporation). The conditions for the XRD measurement were as follows.

[0107] Radiation source: CuKα line (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 4° / min Step size: 0.02° Measurement range: 2θ = 26° to 33°

[0108] Using calculation software (product name: SmartLab Studio II, manufactured by Rigaku Corporation), the monoclinic coefficient (f) was calculated from the obtained XRD pattern using equations (5) and (6). ｍ ) and the crystallite size (D) of monoclinic zirconia ｍ ) was sought.

[0109] (BET specific surface area) The BET specific surface area of ​​the powder sample was measured using a general fluidized type automatic specific surface area analyzer (device name: TriStar II, manufactured by Micromeritics) in accordance with JIS R 1626-1996. Nitrogen gas was used as the adsorption gas. Prior to measurement, the powder sample was pre-treated by degassing in an air atmosphere at 250°C for 30 minutes.

[0110] (Particle size distribution measurement) The volume particle size distribution curve of the powder sample is measured using the MT3000II mode of the Microtrac particle size analyzer (product name: MT3000II, manufactured by Microtrac-Bell), and the median diameter (D ５０ The following measurements were taken. Prior to the measurements, the powder sample was suspended in a 0.2% by mass aqueous solution of sodium hexametaphosphate and dispersed for 10 minutes using an ultrasonic homogenizer as a pretreatment.

[0111] (Monoclinic fraction and monoclinic intensity ratio of sintered body) The sintered body sample was measured by XRD under the same conditions as the powder sample. Using the obtained XRD pattern and calculation software (software name: SmartLab Studio II, manufactured by Rigaku Corporation), the monoclinic fraction (f) was calculated using equations (5) and (6). ｍ The intensity ratio of the monoclinic crystals was determined.

[0112] For XRD measurements, sintered samples were used in which the surface was ground using a surface grinder, followed by automatic polishing with waterproof sandpaper (800 grit), automatic polishing with a diamond slurry with an average particle size of 3 μm, and automatic polishing with 0.03 μm colloidal silica to achieve a mirror finish, resulting in a surface roughness (Ra) of ≤0.04 μm. An automatic polishing machine (machine name: MECATECH 334, manufactured by PRESI) was used for the automatic polishing.

[0113] (Sintered body density) The actual density of the sintered body sample 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 true density was calculated from the above formulas (1) to (4), and the true density (ρ) ０ The relative density (%) was determined from the measured density (ρ) value relative to the given value, and this was defined as the sintered body density.

[0114] (Average grain size) The average grain size was determined by the planimetric method using the SEM observation image of the sintered body sample obtained by field emission scanning electron microscopy. Specifically, a circle with diameter φ was drawn on the SEM observation image, and the number of crystal particles (Nc) within the circle and the number of crystal particles (Ni) on the circumference of the circle were measured. The total number of crystal particles (Nc + Ni) was set to 750 ± 250, and the average grain size was determined using the above formula (8).

[0115] For each sample, three fields of view were measured at an observation magnification of M = 25,000x. A circle with φ = 8.5 cm was drawn on each SEM observation map, and D was calculated using equation (8). The average value of D from the three fields of view was taken, and this value was defined as the average crystal grain size. The total number of crystal grains (Nc + Ni) in the three SEM observation maps was in the range of 600 to 950.

[0116] Prior to measurement, the sintered body samples were pre-treated by mirror polishing followed by thermal etching. For mirror polishing, the surface of the sintered body was ground using a surface grinding machine, and then polished using a mirror polishing device with diamond abrasive grains of average particle sizes of 9 μm, 6 μm, and 1 μm in sequence.

[0117] (Fracture Toughness Value) The fracture toughness value of the sintered body sample was measured according to the SEPB method specified in JIS R1607. The measurement was performed using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements was taken as the fracture toughness value.

[0118] (Bending Strength) The bending strength of the sintered body sample was measured using a three-point bending test in accordance with JIS R1601. The measurement was performed using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm, and the average value of 10 measurements was taken as the bending strength.

[0119] <Example 1> Yttrium chloride hexahydrate was added to an aqueous solution of hydrated zirconia powder with an average sol particle size of 210 nm so that the yttrium content was 1.3 mol%. While stirring this solution, a 1 mol / L aqueous ammonia solution was added at a rate of 0.8 kg / h to adjust the pH to 9.5 ± 0.5 to obtain a precipitate consisting of hydrated zirconia and yttrium hydroxide. The obtained precipitate was washed with 7 L of 0.1 mol / L aqueous ammonia, then washed with 2 L of pure water, and dried at 120°C in an air atmosphere to obtain a dry powder. Ethanol was added to the obtained dry powder and mixed in a mortar to form a slurry. This slurry was then dried using a rotary evaporator in a reduced pressure atmosphere of 150 hPa at a drying temperature of 40°C to obtain a mixed powder consisting of yttrium hydroxide and hydrated zirconia with a yttrium content of 1.3 mol%, which was used as the powder for this example. Here, the hydrated zirconia had a monoclinic crystal structure.

[0120] The powder of this embodiment was uniaxially press-molded at a pressure of 70 MPa and then subjected to CIP treatment at a pressure of 294 MPa to obtain a molded body (compacted powder). The obtained molded body was subjected to atmospheric pressure sintering in an air atmosphere at a holding temperature of 1200°C for a holding time of 10 hours to obtain a pre-sintered body. The pre-sintered body was subjected to HIP treatment in an argon atmosphere at a processing pressure of 150 MPa, a holding temperature of 1250°C for a holding time of 1 hour to obtain the sintered body (HIP-treated body) of this embodiment.

[0121] <Example 2> In an aqueous solution of hydrated zirconia powder, Al ２ O ３ A mixed powder consisting of alumina sol, yttrium hydroxide, and hydrated zirconia was obtained using the same method as in Example 1, except that 0.5% by mass of alumina sol was added. The alumina content was 0.5% by mass and the yttrium content was 1.3 mol%.

[0122] Except for using the powder in question and setting the pre-sintering holding time to 2 hours, the molded body and sintered body were obtained in the same manner as in Example 1. The evaluation results of the sintered bodies of the examples, along with the relative density of the pre-sintered bodies, are shown in Table 2.

[0123] <Example 3> In the same manner as in Example 1, except that yttrium chloride hexahydrate was added to an aqueous solution of hydrated zirconia sol so that the yttrium content was 1.2 mol%, and alumina sol was added so that the alumina content was 1.4 mass%, a mixed powder consisting of alumina sol, yttrium hydroxide, and hydrated zirconia was obtained, with alumina content of 1.4 mass% and 1.2 mol%.

[0124] A molded body and a sintered body were obtained in the same manner as in Example 1, except that the powder in question was used and the pre-sintering holding time was set to 1 hour.

[0125] <Example 4> A mixed powder consisting of alumina sol, yttrium hydroxide, and hydrated zirconia was obtained in the same manner as in Example 1, except that yttrium hexahydrate was added to an aqueous solution of hydrated zirconia sol so that the yttrium content was 1.1 mol%, and alumina sol was added so that the alumina content was 2.8 mass%. The mixed powder consisted of alumina sol, yttrium hydroxide, and hydrated zirconia, with an alumina content of 2.8 mass% and a yttrium content of 1.1 mol%.

[0126] A molded body and a sintered body were obtained in the same manner as in Example 1, except that the powder in question was used and the pre-sintering holding time was set to 4 hours.

[0127] <Example 5> Add SiO to an aqueous solution of hydrated zirconia sol. ２ The same method as in Example 1 was used, except that 0.03% by mass of silica sol was added. ２ A mixed powder consisting of silica sol, yttrium hydroxide, and hydrated zirconia was obtained, with a silica content of 0.03% by mass and a yttrium content of 1.3 mol% (converted to a different amount).

[0128] A molded body and a sintered body were obtained in the same manner as in Example 1, except that the powder in question was used and the pre-sintering holding time was set to 6 hours.

[0129] <Comparative Example 1> Yttrium chloride hexahydrate and ammonia aqueous solution were added to the aqueous solution of hydrated zirconia powder from Example 1 so that the yttrium content was 1.6 mol%, and a precipitate was obtained. The obtained precipitate was washed with pure water and dried in an air atmosphere, and then calcined in an air atmosphere at a calcination temperature of 1035°C for 2 hours to obtain calcined powder. The calcined powder was mixed with pure water to make a slurry, which was then ball-milled using zirconia balls, and then dried in an air atmosphere at a drying temperature of 120°C to obtain a powder made of yttrium-containing zirconia with a yttrium content of 1.6 mol%, and this was used as the powder for this comparative example.

[0130] The powder of this comparative example was subjected to mold pressing at a pressure of 70 MPa and CIP treatment at a pressure of 196 MPa to form a molded body. The obtained molded body was subjected to atmospheric pressure sintering in an air atmosphere at a holding temperature of 1300°C for 2 hours to obtain the sintered body of this comparative example.

[0131] <Comparative Example 2> In the ball milling process, a powder made of yttria-stabilized zirconia containing alumina was obtained in the same manner as in Comparative Example 1, except that alumina sol was added to the slurry so that the amount of alumina was 0.5% by mass. This powder was then used as the powder for this comparative example.

[0132] Except for using the powder in question and setting the sintering holding temperature to 1250°C, a molded body and a sintered body were obtained in the same manner as in Comparative Example 1.

[0133] The results for the examples and comparative examples are shown in the table below.

[0134]

[0135] The sintered bodies in the examples all consisted of monoclinic zirconia and tetragonal zirconia in their crystalline phases. Furthermore, from Example 1, the sintered bodies of these examples exhibited a fracture toughness value of 10 MPa·m² as measured by the SEPB method, without the effect of the added components. ０．５It was confirmed that the value exceeded [value]. Furthermore, from Examples 1 and 2, it was confirmed that the fracture toughness value was further improved by including alumina. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2024-169328, filed on September 27, 2024, are incorporated herein by reference as the disclosure of the specification.

Claims

1. Y ２ O ３ A sintered body of yttrium-stabilized zirconia having a converted yttrium content of 2.0 mol% or less, an average crystal grain size of 150 nm or more and 270 nm or less, and a 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 of 0.8 or more.

2. The sintered body according to claim 1, wherein the relative density is 99.5% or higher.

3. The sintered body according to claim 1 or 2, comprising at least one of alumina and silica as an additive component.

4. The sintered body according to claim 3, wherein the content of the additive component is 5.0% by mass or less.

5. The fracture toughness value measured by a method conforming to the SEPB method specified in JIS R1607 is 10.5 Pa·m. ０．５ The sintered body according to claim 1 or 2.

6. Contains yttrium source and monoclinic zirconia, and has a BET specific surface area of ​​80 m². ２ / g or more 200m ２ A method for producing a sintered body according to claim 1 or 2, comprising: molding a raw material composition having a density of 1 / g or less to form a zirconia molded body; sintering the zirconia molded body to obtain a pre-sintered body with a relative density of 93% to 99%; and pressurizing the pre-sintered body.

7. A member comprising the sintered body according to claim 1 or 2.

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