Sintered body and method for manufacturing the same

Abstract

Without requiring the use of additives, 10 MPa·m 1 / 2 A sintered body of yttrium-stabilized zirconia that provides at least one of the fracture toughness values ​​measured by the SEPB method exceeding a certain threshold, and a method for manufacturing the same, wherein the yttrium content in Y2O3 terms is 2.0 mol% or less, the average grain size is 150 nm or more and 270 nm or less, 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 more.

Description

Technical Field

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

Background Art

[0002] In addition to conventional applications that require strength, such as grinding media and structural materials, the application of zirconia sintered bodies to decorative applications, such as decorative parts for watches, portable electronic devices, automobiles, and home appliances, has been studied. A sintered body applied to a decorative application is required to reduce brittleness, that is, to increase the fracture toughness value.

[0003] For example, Patent Document 1 discloses a sintered body containing a large amount of a plurality of additive components other than zirconia, such as phosphorus, silicon dioxide, and alumina, having a fracture toughness value of 11 MPa·m measured in accordance with JIS R 1607. 1 / 2 However, JIS R 1607 defines two methods for measuring fracture toughness, the IF method and the SEPB method, and it is not specified in Patent Document 1 which measurement method was used to obtain the measured value.

[0004] Further, Patent Document 2 discloses a sintered body containing germanium oxide and alumina and having a fracture toughness value of 10.3 to 12.8 MPa·m. 1 / 2

[0005] On the other hand, Patent Document 3 discloses a sintered body of zirconia containing 1% by mass of alumina as an additive component and 1.6 mol% of yttria, having a fracture toughness value of 10.3 MPa·m measured by the SEPB method. 1 / 2

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] Patent Document 2 states that the fracture toughness value measured by the SEPB method is 10 MPa·m. 1 / 2 The document discloses a sintered body exceeding [a certain value]. At the same time, it is disclosed that a sintered body in which the only additive component is germanium oxide exhibits a significantly reduced fracture toughness (Example 1). Similarly, Patent Document 3 also discloses a fracture toughness value of 10 MPa·m. 1 / 2 Sintered bodies exceeding a certain value contain alumina, but the fracture toughness value of a sintered body without alumina is 6.5 MPa·m 0.5 The toughness was significantly reduced (Example 7). Thus, conventional sintered bodies reported as high-toughness zirconia can be made to 10 MPa·m by making the inclusion of additive components essential. 1 / 2 It achieved fracture toughness values ​​exceeding those measured by the SEPB method.

[0008] This disclosure does not require the use of additives, and achieves 10 MPa·m 1 / 2 The objective is 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. [Means for solving the problem]

[0009] This disclosure investigates the improvement of fracture toughness in zirconia sintered bodies through mechanisms different from those of additive components. As a result, we found the possibility that the fracture toughness of zirconia can be further improved by controlling the structure of zirconia in the sintered body, and confirmed that sintered bodies exhibiting such effects cannot be obtained from conventional raw materials used for sintered bodies. We identified a different sintering mechanism and a suitable raw material for it, and as a result, we found that it is possible to realize a sintered body in which the fracture toughness of zirconia can be further improved, 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] The content of yttrium in terms of Y2O3 is 2.0 mol% or less, the average crystal grain size is 150 nm or more and 270 nm or less, 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 more, A sintered body of yttrium-stabilized zirconia. [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 additive component of alumina and silica. [4] The sintered body according to [3] above, wherein the content of the additive component is 5.0 mass% or less. [5] The fracture toughness value measured by a method according to the SEPB method defined in JIS R1607 is 10.5 Pa·m 0.5 or more, and the sintered body according to any one of [1] to [4] above. [6] Containing a yttrium source and monoclinic zirconia, and sintering a zirconia compact made of raw material powder having a BET specific surface area of 80 m 2 / g or more and 200 m 2 / g or less to obtain a pre-sintered body having a relative density of 93% or more and 99% or less, and Pressurizing and sintering the pre-sintered body A method for producing a sintered body according to any one of [1] to [5] above, including the above steps. [7] A member including the sintered body according to any one of [1] to [5] above.

Advantages of the Invention

[0012] According to the present disclosure, it is possible to provide at least one of a sintered body showing a fracture toughness value measured by the SEPB method exceeding 10 MPa·m 1 / 2 without necessarily using an additive component, and a method for producing the same. [Modes for carrying out the invention]

[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 (g / cm³) of mass measured by mass measurement to the volume obtained from dimensional measurement. 3 The measured density of the sintered body is the ratio of mass to volume measured by the Archimedes method (g / cm³). 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) ρ0 = 100 / [(Y A / 3.987)+(Y S / 2.2)+(100-Y A -Y S ) / ρ Z (4)

[0016] In equations (1) to (4), ρ0 is the true density of the sintered body. ρ Z The true density of zirconia containing yttrium, A and C are constants. X is the molar percentage (mol%) of the stabilizing element in oxide form relative to the total of zirconia (ZrO2) and the stabilizing element in oxide form (for example, yttria (Y2O3) if the stabilizing element is yttrium (Y)), and, Y A and Y S This represents the mass percentage (mass%) of alumina (as converted to Al2O3) and silicon (as converted to SiO2) relative to the total of zirconia, yttrium, aluminum, and silicon as converted to ZrO2, Y2O3 (as converted to oxide), Al2O3, and SiO2, respectively.

[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 (11-1) 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 equation (5), and the monoclinic intensity ratio from the following equation (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) The monoclinic intensity ratio is 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. I t (111) represents the area intensity of the XRD peak corresponding to the (111) plane of tetragonal zirconia.

[0020] The following conditions can be listed as requirements for measuring XRD patterns. Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.01° Measurement range: 2θ = 26° ~ 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 (e.g., 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 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 equation (7). D m =κλ / (βcosθ m ) (7)

[0026] In equation (7), D m This is the crystallite size (nm) of monoclinic zirconia. κ is Scherrer's constant (κ=1), λ is the wavelength (nm) of the radiation source used in the XRD measurement. β is the full width at half maximum (°) after correcting for mechanical spreading using quartz sand with a particle size of 25-90 μm (for example, manufactured by Wako Pure Chemical Industries, Ltd.). θ m This refers to the Black angle (°) of the reflection corresponding to the (11-1) plane of monoclinic zirconia in XRD measurement, and θ t This is the Black angle (°) of the reflection corresponding to the (111) plane of tetragonal zirconia in XRD measurements.

[0027] When using CuKα radiation 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 observation image of a sintered sample obtained by field emission scanning electron microscopy. Specifically, a circle with diameter φ is drawn on the SEM observation image, the number of crystal grains (Nc) within the circle and the number of crystal grains (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 crystal 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 used for scanning electron microscopy observation.

[0030] The average grain size can be determined as the particle size obtained for a crystal grain size of 750 ± 250 (Nc + Ni) particles. If the number of crystal grains (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 a total of 500 or more (Nc + Ni) particles, preferably 750 ± 250, and D should be calculated for each SEM observation image. The average value of the obtained D values ​​should then be taken, and this value should be determined as the average grain size.

[0031] The "BET specific surface area" is a value determined by the single-point BET method using nitrogen (N2) as the adsorbent, in accordance with JIS R 1626-1996. Prior to measurement, the sample should be pre-treated 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 should be taken as the fracture toughness value of this embodiment. Note that JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method. The IF method tends to produce larger values ​​than the SEPB method. Furthermore, because the IF method is a simple measurement method, there is a large variation in the measured values ​​from one measurement to the next. Therefore, the fracture toughness value in this embodiment and the fracture toughness value measured by the IF method cannot be compared in absolute terms. Similarly, the fracture toughness value measured by a method other than the SEPB method and the fracture toughness value measured by the SEPB method cannot be compared in absolute terms.

[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 provides a yttrium-stabilized zirconia sintered body having a yttrium content of 2.0 mol% or less (calculated as Y2O3), 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 (i.e., "monoclinic intensity ratio") of 0.8 or more. As a result, without requiring additives such as alumina, a fracture toughness value of 10 MPa·m is achieved. 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 in which the crystalline phase is stabilized by solid solution of yttrium in zirconia (ZrO2).

[0039] The sintered body of this embodiment has a yttrium content (hereinafter also referred to as "yttrium content") of 2.0 mol% or less, calculated as Y2O3. If the yttrium content exceeds 2.0 mol%, stress-induced phase transformation from tetragonal to monoclinic is less likely to occur, resulting in a lower fracture toughness value. To easily exhibit a high fracture toughness value, the yttrium content 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 content is preferably 1.0 mol% or more, 1.1 mol% or more, or 1.2 mol% or more. The yttrium content of the sintered body of this embodiment 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 the molar ratio [mol%] of yttrium converted to Y2O3 relative to the total amount of zirconia (ZrO2) and yttrium converted to Y2O3.

[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 components is the mass percentage [mass%] of the oxide-equivalent added components to the total of zirconia (ZrO2), yttrium converted to Y2O3, and the oxide-equivalent added components. The oxide equivalents for each added component are Al2O3 for alumina and SiO2 for silica.

[0047] The sintered body of this embodiment is preferably free of impurities, and more preferably below the detection limit (for example, 0.1% by mass). For example, the phosphorus (P) content as an impurity is preferably 0.1% by mass or less, and even less than 0.1% by mass. Also, the content of metallic elements other than zirconia, alumina, silica, and yttrium is preferably less than 0.1% by mass. On the other hand, it may contain unavoidable impurities such as zirconia hafnia (HfO2). In the calculation of composition-related values ​​such as density in this embodiment, hafnia (HfO2) may be treated as zirconia (ZrO2) in the calculation.

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

[0049] Stabilizing element content (yttrium content) ={Y2O3 / (ZrO2+Y2O3)}×100[mol%] Alumina content (amount of alumina) ={Al2O3 / (ZrO2+Y2O3+Al2O3+SiO2)}×100[mass%] Silica content (silica amount) ={SiO2 / (ZrO2+Y2O3+Al2O3+SiO2)}×100[mass%] Content of added ingredients (amount of added ingredients) ={(Al2O3+SiO2) / (ZrO2+Y2O3+Al2O3+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 described above. Note that in sintered bodies that do not have an XRD peak 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] In this embodiment, the monoclinic content of the sintered body can be any value as long as it satisfies the monoclinic intensity ratio described above. Examples of monoclinic content for the sintered body in 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 for the sintered body in this embodiment include 3.0% to 15.0%, 5.0% to 10.0%, or 6.0% to 9.0%.

[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 strength 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 higher, 99.5% or higher, or 99.7% or higher in relative density, and may also be 100% or lower, or 99.9% or lower.

[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 SEPB method specified in JIS R1607 is 10.5 Pa·m. 0.5 Above, 11Pa m 0.5 12 Pa·m or more 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 More than 15MPa m 0.5 Below, 11 Pa m 0.5 More than 15MPa m 0.5 The following, or 12 Pa·m 0.5 More than 14MPa m 0.5 The following are listed: The bending strength of the sintered body in 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 higher, 950 MPa or higher, or 970 MPa or higher, and also preferable that it is 1200 MPa or lower, 1150 MPa or lower, or 1050 MPa or lower. Examples of the bending strength of the sintered body in this embodiment include 900 MPa or higher and 1200 MPa or lower, 950 MPa or higher and 1150 MPa or lower, or 970 MPa or higher and 1050 MPa or lower.

[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 sintered bodies] The manufacturing method for the sintered body of this embodiment is arbitrary as long as a sintered body satisfying the above-described configuration can be obtained. A preferred manufacturing method for the sintered body of this embodiment involves a zirconia source and a yttrium source different from the zirconium source, wherein the yttrium content, calculated as Y2O3, 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 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 the yttrium content, calculated as Y2O3, is 2.0 mol% or less, and the BET specific surface area is 80 m². 2 We provide molded zirconia articles made from raw material powder containing at least / g.

[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 may be at least one of zirconia (ZrO2) and its precursors, but hydrated zirconia powder is preferred. Hydrated zirconia powder is a powder consisting of particles of hydrated zirconia (ZrO2·nH2O; n is a real number), and hydrated zirconia is a hydrate of zirconia. The hydrate is removed from the hydrated zirconia by heat treatment at 900°C or higher.

[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, 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] The yttrium content (yttrium amount) of the raw material powder, calculated as Y2O3, 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 / g or more, 120m 2 / g or more, 150m 2 / g or more, or 160m 2 It is preferable that the BET specific surface area is 80 m² or more. 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 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 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 500nm or less, 400nm or less, 300nm or less, or 200nm or less, and may also be 50nm or more, 100nm or more, 120nm or more, or 150nm or more. Furthermore, the median diameter may be 50nm or more and 500nm or less, 100nm or more and 400nm or less, 120nm or more and 300nm or less, or 150nm or more and 200nm 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 aqueous solution of sodium hexametaphosphate 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 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 pressing (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 forming 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 to be sintered (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 an atmospheric environment Holding temperature: 1100°C or higher or 1200°C or higher, 1300℃ or below or 1250℃ or below

[0081] The pre-sintering time can be adjusted as appropriate 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 between 0.5 hours and 24 hours, or between 1 hour and 15 hours. To promote densification by pressure sintering, the relative density of the resulting pre-sintered body is preferably 93% or higher, 94% or higher, or 95% or higher, and also preferably 99% or lower, 98% or lower, or 97% or lower. A density of 93% to 99% or 94% to 98% for the pre-sintered body is a good example, and a density of 95% to 97% tends to result in a higher relative density for 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: Relaxing atmosphere, Preferably, at least one of a nitrogen atmosphere and an argon atmosphere. Comfortable argon atmosphere Holding pressure: 50 MPa or more or 100 MPa or more, 500 MPa or less or 200 MPa or less Holding temperature: 1100°C or higher, 1150°C or higher, or 1230°C or higher, Below 1350℃, below 1300℃, or below 1270℃

[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 producing raw material powder] The raw material powder used in the molding process is a powder for sintered bodies, and is a powder for producing molded bodies, a powder for producing calcined bodies, or a powder for producing 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 producing it is a method (hereinafter also referred to as "this powder production 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 to 400 nm with alcohol, and comprising 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 manufactured, for example, by the method disclosed in Patent Document 3.

[0093] The yttrium content (yttrium amount) in the raw material composition, calculated as Y2O3, should be the same as the yttrium amount in 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 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.

[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 furthermore, 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 higher or 100 hPa or higher, and preferred reduced-pressure atmospheres include 50 hPa to 0.1 MPa or 100 hPa to 200 hPa.

[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. [Examples]

[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 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) A standard X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation) was used to obtain the XRD pattern of the powder sample. The conditions for the XRD measurement were as follows:

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

[0108] Using calculation software (product name: SmartLab StudioII, manufactured by Rigaku Corporation), the monoclinic fraction (f) is 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 ​​powder samples was measured using a general-purpose fluidized bed specific surface area (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 samples were 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 a powder sample is measured using the MT3000II mode of the Microtrac particle size analyzer (product name: MT3000II, manufactured by Microtrac-Bell). 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 subjected to XRD measurement under the same conditions as the powder sample. Using the obtained XRD patterns and calculation software (software name: SmartLab StudioII, manufactured by Rigaku Corporation), the monoclinic fraction (f) was calculated using equations (5) and (6). m The intensity ratios of the monoclinic crystals were determined.

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

[0113] (Sintered body density) The actual density of the sintered body sample was measured using the Archimedes method. Prior to the measurement, the mass of the dried sintered body was measured, and then the sintered body was placed in water and boiled for 1 hour as a pretreatment. The true density was calculated from the above-mentioned equations (1) to (4), and the relative density (%) was determined from the value of the measured density (ρ) relative to the true density (ρ0), and this was defined as the sintered body density.

[0114] (Average grain size) The average grain size was determined by the planimetric method using SEM (Scanning Electron Microscopy) images of sintered samples obtained by field emission scanning electron microscopy. Specifically, a circle with diameter φ was drawn on the SEM 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 then calculated using the above-mentioned equation (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 image, 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 images 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 of the sintered body specimens was measured according to the SEPB method specified in JIS R1607. The measurement was performed using a columnar sintered body specimen with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm. The average value of 10 measurements was used as the fracture toughness value.

[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 used 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 under a reduced pressure of 150 hPa and 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> A mixed powder consisting of alumina sol, yttrium hydroxide, and hydrated zirconia was obtained in the same manner as in Example 1, except that 0.5% by mass of alumina sol (calculated as Al2O3) was added to an aqueous solution of hydrated zirconia powder. The mixed powder contained 0.5% by mass of alumina and 1.3 mol% of yttrium.

[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> 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 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%.

[0124] Except for using the powder in question and setting the pre-sintering holding time to 1 hour, the molded body and sintered body were obtained in the same manner as in Example 1.

[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 chloride 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] Except for using the powder in question and setting the pre-sintering holding time to 4 hours, molded and sintered bodies were obtained in the same manner as in Example 1.

[0127] <Example 5> A mixed powder consisting of silica sol, yttrium hydroxide, and hydrated zirconia was obtained in the same manner as in Example 1, except that 0.03% by mass of silica sol (in terms of SiO2) was added to an aqueous solution of hydrated zirconia sol. The mixed powder contained 0.03% by mass of silica and 1.3 mol% of yttrium (in terms of SiO2).

[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> In the aqueous solution of hydrated zirconia powder from Example 1, yttrium chloride hexahydrate and aqueous ammonia solution were added to obtain a precipitate so that the yttrium content was 1.6 mol%. The obtained precipitate was washed with pure water and dried in an air atmosphere, then calcined in an air atmosphere at a calcination temperature of 1035°C for 2 hours to obtain calcined powder. The calcined powder was mixed with pure water to form 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 consisting of yttrium-containing zirconia with a yttrium content of 1.6 mol%, which 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 alumina content 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, molded and sintered bodies 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. [Table 1]

[0134] [Table 2]

[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·m as measured by the SEPB method, without the effect of the added components. 0.5 It 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 part of the disclosure of the specification.

Claims

1. Y ２ O ３ The converted yttrium content is 2.0 mol% or less. The average grain size is 150 nm or more and 270 nm or less, The ratio of the area intensity of the XRD peak corresponding to the (11-1) plane of monoclinic zirconia to the area intensity of the XRD peak corresponding to the (111) plane of monoclinic zirconia is 0.8 or greater. Sintered body of yttrium-stabilized zirconia.

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

3. A 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 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. It contains yttrium source and monoclinic zirconia, and has a BET specific surface area of ​​80 m². ２ / g or more 200m ２ To form a zirconia molded body by molding a raw material composition that is less than or equal to / g. The zirconia molded body is sintered to obtain a pre-sintered body with a relative density of 93% to 99%, and Pressurizing the pre-sintered body A method for producing a sintered body according to claim 1 or 2, including the method described above.

7. A member comprising the sintered body described in claim 1 or 2.

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