Sintered body with excellent impact resistance

Abstract

To provide at least one of: a sintered body that shows improved impact resistance by generating impact absorption by plastic deformation, against the impact exceeding the fracture resistance of the sintered body, prior to the occurrence of brittle fracture; and a method for producing the same.SOLUTION: A sintered body contains zirconia containing a stabilizer, and has a region in which an impact mark is formed when impact force is applied.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a sintered body having excellent impact resistance, and in particular to a sintered body having excellent impact resistance and made mainly of zirconia. [Background technology]

[0002] Compared to metallic materials, ceramics have high mechanical properties and chemical stability, but are also brittle. Therefore, when subjected to dynamic impacts at room temperature, such as dropping, sintered bodies such as zirconia ceramics are prone to fracture due to the initiation and propagation of cracks, known as brittle fracture. To prevent such brittle fracture, efforts are being made to improve fracture toughness.

[0003] For example, Patent Document 1 discloses a method for forming a zirconia alloy containing 4 mol% yttria with SrAl 12 O 19 It has been reported that the fracture toughness can be improved by dispersing cubic Sr in zirconia. x It has been reported that dispersing NbO3 improves fracture toughness and drop resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-037746 [Patent Document 2] Special Publication No. 2019-501855 Summary of the Invention [Problem to be solved by the invention]

[0005] The improvement in impact resistance in Patent Documents 1 and 2 was the result of improved fracture resistance obtained by improving fracture toughness. In both sintered bodies, when an impact exceeding the fracture resistance occurs, brittle fracture such as the generation of cracks first occurs, and then fracture occurs as this fracture progresses. Thus, the fracture mechanism in both sintered bodies was caused solely by brittle fracture.

[0006] In response to this, the present disclosure aims to provide at least one of a sintered body and a method for manufacturing the same that has improved impact resistance by generating shock absorption through plastic deformation before brittle fracture occurs in response to an impact that exceeds the fracture resistance of the sintered body. [Means for solving the problem]

[0007] The present inventors have investigated how to improve the impact resistance of ceramics, and as a result have found that the improvement in impact resistance can be achieved by a mechanism different from that of improving fracture toughness.

[0008] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows. [1] A sintered body comprising zirconia containing a stabilizer and having a region where an impact mark is formed when an impact force is applied. [2] The sintered body according to the above [1], wherein the impact mark is a recess. [3] The sintered body according to the above [1] or [2], wherein the stabilizer content is 3 mol % or more and 10 mol % or less. [4] The sintered body according to any one of the above [1] to [3], wherein the stabilizer is two or more selected from the group consisting of yttria, calcia, magnesia, and ceria. [5] The sintered body according to any one of [1] to [4] above, wherein the stabilizer is yttria and ceria. [6] The sintered body according to any one of [1] to [5] above, wherein the yttria content is less than 1.5 mol%. [7] The sintered body according to any one of [1] to [6] above, wherein the ceria content is 2 mol % or more and 7.5 mol % or less. [8] The sintered body according to any one of [1] to [7] above, which contains alumina. [9] A sintered body according to any one of [1] to [8] above, having a region in which the ratio of the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal is greater than 0 and less than or equal to 1.0.

[10] The sintered body according to any one of [1] to [9] above, which has a region where the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal relative to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal is more than 1.0 and 10 or less when an impact force is applied.

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

[10] above, having a Vickers hardness of 12 GPa or less.

[12] A member comprising the sintered body according to any one of [1] to

[11] above. [Effects of the Invention]

[0009] The present disclosure makes it possible to provide at least one of a sintered body and a method for manufacturing the same, in which shock absorption by plastic deformation occurs before brittle fracture occurs in response to an impact that exceeds the fracture resistance of the sintered body, thereby improving impact resistance. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic diagram showing the state of a drop ball test using a DuPont drop ball tester [Figure 2] Schematic diagram showing an example of the impact core (formation of a recess) after a ball drop test. [Figure 3] Schematic diagram showing an example of the impact core area of ​​a high-hardness sintered body after a ball drop test [Figure 4] Schematic diagram showing an example of the arrangement of measurement samples in a drop ball test [Figure 5] Schematic diagram showing how to measure the depth of impact marks [Figure 6]Schematic diagram showing an example of the mode of destruction in a ball drop test: (a) state where destruction has occurred, (b) state where destruction has not occurred [Figure 7] Appearance of the sintered body of Example 1 after the drop test [Figure 8] Appearance of impact marks formed on the sintered body of Example 1 after a drop test (magnification: 20x) [Figure 9] Appearance of the sintered body of Comparative Example 3 after drop test (magnification: 20x) DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the sintered body of the present disclosure will be described with reference to an example of an embodiment.

[0012] The sintered body of this embodiment is a sintered body that contains zirconia containing a stabilizer and has a region where an impact mark is formed when an impact force is applied.

[0013] The sintered body of this embodiment contains zirconia containing a stabilizer, and is preferably a so-called zirconia sintered body having zirconia containing a stabilizer as a matrix (main phase). Because it contains a stabilizer, the sintered body of this embodiment can also be considered a partially stabilized zirconia sintered body.

[0014] The sintered body of this embodiment has a region where an impact mark is formed when an impact force is applied. One of the reasons why the impact resistance of the sintered body of this embodiment is improved, i.e., why the impact resistance is improved, is thought to be that the region where the impact mark is formed (hereinafter also referred to as the "plastic deformation region") exhibits the function of absorbing and dispersing the energy transmitted by the applied impact force. As a result, when an impact force is applied, plastic deformation occurs at least prior to the occurrence of brittle fracture, and as a result, the occurrence of brittle fracture is suppressed and impact resistance is improved.

[0015] The sintered body of this embodiment may have a plastic deformation region in at least a portion of the sintered body (i.e., it may be a sintered body having a plastic deformation region), but it may also be composed mainly of a plastic deformation region, or it may be a sintered body composed of a plastic deformation region.

[0016] The term "impact force" refers to a force that transmits energy to a sintered body, particularly a dynamic external force, preferably an external force that exceeds the fracture resistance of the sintered body, more preferably a dynamic external force that exceeds the fracture resistance of the sintered body, and further a dynamic external force that applies elastic energy to the sintered body.

[0017] "When an impact force is applied" means a state in which energy is applied to at least a part of the sintered body, such as when the sintered body falls and hits the ground, or when a dropped object hits the sintered body, and energy is dynamically applied to the sintered body by the sintered body coming into contact with an object.

[0018] The "impact mark" is a mark left by the application of an impact force to a sintered body, preferably a mark formed on the sintered body by the application of an impact force. In other words, the impact mark is a mark left by plastic deformation of the sintered body, that is, a mark of plastic deformation that occurs prior to destruction. Specific examples of the impact mark include a recess or an uneven portion in the impact core (described below), or even a recess or a recess along the direction of application of the impact force.

[0019] In this embodiment, whether or not a sintered body has a plastically deformed region can be confirmed by applying an impact force (e.g., a dynamic external force that accelerates fracture of the sintered body) to the sintered body using any method. Applying an impact force to a sintered body and confirming the formation of impact marks, such as recesses or irregularities, as traces of plastic deformation (particularly traces of deformation prior to fracture), on the sintered body after the impact force is applied can confirm that the sintered body has a plastically deformed region. In the sintered body of this embodiment, the impact marks are formed due to plastic deformation, but may also include defects such as cracks that occur after the impact marks are formed. On the other hand, if, after the application of the impact force, only defects such as cracks are observed (i.e., only defects are observed without the formation of impact marks due to plastic deformation) or if only deformation resulting from fracture, such as Hertzian fracture, is observed (i.e., only deformation formed by the progression of fracture such as an initially generated crack is observed; dashed circle in Figure 9), it can be determined that the sintered body does not have a plastically deformed region.

[0020] A preferred method for confirming the presence of a plastic deformation region is a drop ball test (hereinafter simply referred to as the "drop ball test"), in which a DuPont drop ball tester conforming to JIS K 5600 5-3 is used to drop a 300 g weight from a height of 350 mm at room temperature.

[0021] FIG. 1 is a schematic diagram illustrating a ball drop test using a DuPont ball drop tester. As shown in FIG. 1, a test sample (101) is attached with protective tape (107) to its backside and placed on a cylindrical sample stage (106) of the tester. It is secured to the sample stage by attaching fixing tape (105) to its side. The drop weight consists of a weight (104) and a punch (102), which is placed on the surface of the test sample (101). The drop test is performed by dropping the weight (104) from the punch (102) from a height equivalent to the drop height (350 mm, corresponding to the double-headed arrow in FIG. 1). The punch (102) has a cylindrical shape with a spherical (hemispherical) tip. This allows the test sample to be subjected to the same impact force as if a hard ball of the same size as the spherical surface were dropped from the drop height. By dropping the weight (104) along the guides (103a, 103b) of the DuPont type ball drop tester, a desired impact force can be applied to the measurement sample (101) via the hitting mold (102). If a hitting mold is not used, a hard ball with a mass of 300 g and the same diameter as the spherical part (hemispherical part) of the hitting mold may be dropped onto the measurement sample from a height equivalent to the drop height.

[0022] FIG. 2 is a schematic diagram showing the appearance of the sintered body of this embodiment after a ball drop test. As shown in FIG. 2, it can be confirmed that an impact mark has been formed in the sintered body of this embodiment in the region where the impact force from the falling weight (striker) was applied (hereinafter also referred to as the "impact core") in the ball drop test. The impact mark in FIG. 2 shows a state in which a recess has been formed near the impact core, and it can be visually confirmed that there is a plastic deformation region. Although not shown, defects such as cracks may be present near the recess. In contrast, FIG. 3 is a schematic diagram showing the appearance of a conventional sintered body after a ball drop test. As shown in FIG. 3, the formation of an impact mark at the impact core cannot be confirmed in the conventional sintered body, and only defects such as cracks have occurred.

[0023] The presence or absence of a plastically deformed region may be confirmed by at least one of visual inspection and observation with an optical microscope, preferably visual inspection. The magnification for observation with an optical microscope is, for example, 1 to 100 times, preferably 10 to 30 times.

[0024] Although not shown, a conventional sintered body with high fracture toughness (for example, a fracture toughness value of 7 MPa m as measured by the SEPB method) is also shown. 0.5 In the case of sintered compacts (e.g., sintered compacts exceeding 350 mm), there is no change in appearance before and after the ball drop test, and the impact core cannot be identified. In this case, the ball drop test is performed by increasing the drop height until the impact core can be identified, and the presence or absence of a plastic deformation region can be confirmed by checking the formation of impact marks such as recesses and the occurrence of defects in the impact core that has been identified. However, in the case of the sintered compact of this embodiment, the presence or absence of a plastic deformation region can be confirmed by performing the ball drop test at a ball drop height of 350 mm.

[0025] In this embodiment, the ball drop test can be carried out at room temperature (20 to 30° C.) using a DuPont ball drop tester conforming to JIS K 5600 5-3. The conditions for the ball drop test include the following. Falling weight: (shape) A spherical hard ball with a diameter of 6.35 mm or a cylindrical die with a spherical tip with a diameter of 6.35 mm (mass) 300g Drop height: 350mm Measurement sample: A sintered body in the shape of a plate measuring 40 mm long x 30 mm wide x 2 mm thick, with both surfaces having a surface roughness of Ra≦0.02 μm

[0026] To prevent sample pieces from scattering, the measurement sample is placed on the sample stage of the ball drop tester by fixing one surface of the sample (40mm x 30mm) with double-sided tape. After placement, fixation tape (protective tape) is applied along the length of the main surface opposite the surface on which the sample is fixed, fixing the sample in place (Figure 4). The ball drop test can then be carried out on the fixed sample.

[0027] The depth of the impact mark formed by the ball drop test may be, for example, greater than 0 and less than 3.5, or even greater than 0.5 and less than 3, as the depth of the deepest part of the impact mark (204 in Figure 2) relative to the thickness of the sintered compact (203 in Figure 2). Note that the depth (204) of the impact mark (depression) in Figure 2 is exaggerated.

[0028] In this embodiment, the depth of the impact mark can be measured using a general laser microscope (for example, VK-9500 / VK-9510, manufactured by Keyence Corporation). The observation magnification can be, for example, 10 to 50 times, or even 20 times, and the laser wavelength can be 408 nm.

[0029] FIG. 5 shows a schematic diagram illustrating a method for measuring the depth of an impact mark. A line profile (503A) is taken that passes through the center of the impact mark, and the length (L1) of the deepest point in the Z-axis direction is measured. Similarly, a similar line profile (503B) is taken perpendicular to the line profile, and the length (L2) of the deepest point in the Z-axis direction is measured. The lengths of both deepest points are averaged (=(L1+L2) / 2), and this average length is used as the depth (504) of the impact mark. An example of the measurement condition for measuring the length of the deepest point is 0.5 μm / step. Prior to the measurement, a standard sample (e.g., a patterned Si substrate) with a known pattern length is measured, and the analytical accuracy can be adjusted.

[0030] Such analyses, such as line profile and measurement of the deepest part in the Z-axis direction, can be performed by image analysis using analysis software attached to the laser microscope (for example, software name: VK-H1A9VK ANALYZER Version 3.0.1.0).

[0031] The zirconia contained in the sintered body of this embodiment contains a stabilizer. The stabilizer may contain an element having a function of stabilizing zirconia, and is preferably two or more selected from the group consisting of yttria (YO), calcia (CaO), magnesia (MgO), and ceria (CeO), more preferably contains at least yttria, more preferably contains yttria and one or more selected from the group consisting of calcia, magnesia, and ceria, and even more preferably contains yttria and ceria.

[0032] The stabilizer content is the total ratio (mol%) of stabilizer, calculated as oxide, to the total of zirconia and stabilizer, calculated as oxide. The stabilizer content may be any amount that partially stabilizes zirconia. For example, the stabilizer content in a sintered body made of zirconia containing yttria and ceria (yttria-and-ceria-stabilized zirconia sintered body) can be calculated as {(YO + CeO) / (YO + CeO + ZrO)} × 100 (mol%). The stabilizer content is preferably 3 mol% to 10 mol%, more preferably 4 mol% to 7.5 mol%, even more preferably 4.2 mol% to 6.2 mol%, even more preferably 4.5 mol% to 6.0 mol%, and even more preferably 4.6 mol% to 5.5 mol%.

[0033] When yttria is contained as a stabilizer, the yttria content is preferably less than 1.5 mol%, more preferably 1.3 mol% or less, and even more preferably 1.2 mol% or less. When ceria coexists with yttria, a sintered body can be easily obtained by a simple method such as atmospheric sintering, so the yttria content is more than 0 mol%, preferably 0.5 mol% or more, more preferably 0.6 mol% or more, particularly preferably 0.9 mol% or more, and even more preferably 1.0 mol% or more.

[0034] The sintered body of this embodiment may satisfy the above-mentioned stabilizer content, but when ceria is contained as a stabilizer, the ceria content is optional. Examples of the ceria content include 2 mol% to 7.5 mol%, further 2.5 mol% to 6 mol%, and even 3 mol% to 5 mol%. When calcia is contained as a stabilizer, the calcia content can be 2 mol% to 7.5 mol%, further 2.5 mol% to 6 mol%, and when magnesia is contained as a stabilizer, the magnesia content can be 2 mol% to 7.5 mol%, further 2 mol% to 6 mol%, for example.

[0035] The sintered body of this embodiment preferably contains ceria and yttria as stabilizers, and in this case, the ceria content is preferably 2 mol% or more, 3 mol% or more, or 3.5 mol% or more, and 6 mol% or less, 5.5 mol% or less, or 4.5 mol% or less, and the yttria content is preferably 0.1 mol% or more, 0.5 mol% or more, or 0.9 mol% or more, and less than 1.5 mol%, 1.3 mol% or less, or 1.15 mol% or less.

[0036] The content of each stabilizer is the ratio (mol%) of each stabilizer, calculated as an oxide, to the total of zirconia and the stabilizer, calculated as an oxide. For example, the yttria content in yttria-stabilized zirconia is the ratio (mol%) of yttria to the total of zirconia and yttria, and can be calculated from {(Y2O3 / (Y2O3+ZrO2)) × 100 (mol%). The ceria content in ceria-stabilized zirconia is the ratio (mol%) of ceria to the total of zirconia and ceria, and can be calculated from {(CeO2 / (CeO2+ZrO2)) × 100 (mol%). The yttria content in yttria and ceria-stabilized zirconia sintered bodies can be calculated from {Y2O3 / (Y2O3+CeO2+ZrO2)} × 100 (mol%). In this embodiment, the ceria preferably contains tetravalent cerium, and more preferably does not contain trivalent cerium.

[0037] Since impact marks due to plastic deformation tend to occur more easily, the ratio (molar ratio) of the stabilizing element other than yttrium to yttrium (Y) in the sintered body of this embodiment (hereinafter also referred to as the "S / Y ratio", and when the stabilizer other than yttrium is cerium (Ce) or the like, also referred to as the "Ce / Y ratio", etc.) is preferably 1.2 or more and 5.0 or less, more preferably 1.4 or more and 4.5 or less, even more preferably 1.5 or more and 2.3 or less, and even more preferably 1.6 or more and 2.0 or less.

[0038] The sintered body of this embodiment may contain alumina (Al2O3). This tends to improve mechanical properties, such as static strength. Since the sintered body of this embodiment does not necessarily contain alumina, the alumina content is 0% by mass or more. When alumina is contained, the alumina content is greater than 0% by mass and less than 30% by mass, preferably greater than 0% by mass and less than 20% by mass, and more preferably 0.005% by mass to 10% by mass. The alumina content may be 0% by mass or more, greater than 0% by mass, 0.5% by mass or more, or 1% by mass or more, and may be 20% by mass or less, 17% by mass or less, 12% by mass or less, 10% by mass or less, or 8% by mass or less. The alumina content can be calculated as the mass ratio of aluminum calculated as Al2O3 to the total amount of zirconia, stabilizer calculated as oxide, and aluminum calculated as Al2O3. For example, when zirconia contains yttria and ceria as stabilizers, the alumina content can be calculated as {Al2O3 / (ZrO2+Y2O3+CeO2+Al2O3)}×100 (mass %).

[0039] Alumina (Al2O3) has a large effect on the mechanical properties of the sintered body, but has almost no effect on coloring zirconia. Therefore, in this embodiment, alumina, i.e., aluminum that does not form a complex oxide with a metal element, etc., is not included in the pigment.

[0040] The sintered body of this embodiment preferably contains stabilizer-containing zirconia and is a so-called zirconia sintered body or a partially stabilized zirconia sintered body, which contains stabilizer-containing zirconia as the matrix (main phase). When stabilizer-containing zirconia is used as the matrix (main phase), the mass ratio of stabilizer-containing zirconia in the sintered body (hereinafter also referred to as "zirconia content") is 70 mass% or more, preferably 80 mass% or more, and more preferably more than 90 mass%. When the sintered body has a zirconia content of 100 mass% or less and is composed only of stabilizer-containing zirconia, the mass ratio of zirconia is 100 mass%. The zirconia content can be calculated as the ratio of the total mass of zirconia and stabilizer, calculated as oxide, to the mass of the sintered body, calculated as oxide. For example, when the sintered body contains alumina and the remainder is zirconia containing yttria and ceria as stabilizers, the content of zirconia containing the stabilizer can be calculated as {(ZrO2 + Y2O3 + CeO2) / (ZrO2 + Y2O3 + CeO2 + Al2O3)} × 100 (mass%).

[0041] The sintered body of this embodiment may contain inevitable impurities such as hafnia (HfO2), but preferably contains no components other than stabilizers, zirconia, alumina, and inevitable impurities. In this embodiment, values ​​that are affected by the composition, such as the content and density of each component, can be calculated by regarding hafnia (HfO2) as zirconia (ZrO2).

[0042] The sintered body of this embodiment preferably has a high density, and more preferably has a density equivalent to a relative density of 98% or more. In particular, the density tends to decrease as the alumina content increases. For example, when the alumina content is 0% by mass or more and 10% by mass or less, the lower limit of the measured density is 5.85 g / cm. 3 or more than 5.90g / cm 3 or more, with an upper limit of 6.20 g / cm 3 Below that, 6.10 g / cm 3 Below 6.00 g / cm 3Furthermore, when the alumina content is more than 10 mass% and 20 mass% or less, the measured density is 5.30 g / cm 3 More than 5.85g / cm 3 When the alumina content is more than 20% by mass but less than 30% by mass, the measured density is 5.20 g / cm 3 More than 5.30g / cm 3 The following are some of the reasons for this:

[0043] In this embodiment, the measured density can be determined by Archimedes' method, and is a value determined as the mass determined by mass measurement relative to the volume determined by Archimedes' method.

[0044] The zirconia crystal phase of the sintered body of this embodiment preferably contains at least tetragonal crystals, and may be composed of tetragonal crystals and at least one of cubic crystals and monoclinic crystals.

[0045] The sintered body of the present embodiment has a ratio of the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal (hereinafter referred to as "I (004) / (220) It is preferable that the crystal has a region where the θ is greater than 0 and not greater than 1.0 (hereinafter also referred to as a "randomly oriented region"), and more preferably consists of a randomly oriented region. 220 ") and the tetragonal (004) plane (hereinafter referred to as "T 004 ) are crystal planes that are perpendicular to each other. (004) / (220) The presence of the randomly oriented region is considered to be a sufficient condition for plastic deformation to occur when an impact force is applied. (004) / (220) is preferably 0.1 or more and 0.7 or less, and more preferably 0.2 or more and 0.6 or less.

[0046] When the sintered body of this embodiment absorbs or disperses the energy due to the application of an impact force, a change in the crystal orientation may occur in the plastic deformation region. For example, when an impact force is applied (after the application of the impact force), the crystal orientation in the plastic deformation region may become higher, and further, when an impact force is applied, T 220 The intensity of the powder X-ray diffraction peaks of T 004 The powder X-ray diffraction peak intensity of the powder X-ray diffraction pattern is more than 1.0 and 10 or less (hereinafter also referred to as "highly oriented region"). (004) / (220) is preferably 1.5 or more and 8.0 or less, and more preferably 3.0 or more and 5.0 or less.

[0047] In this embodiment, the powder X-ray diffraction pattern (X-ray diffraction pattern) of the sintered body can be measured using a general X-ray diffractometer for crystallinity analysis (for example, device name: X'pert PRO MPD, manufactured by Spectris).

[0048] The measurement conditions are as follows: Radiation source: CuKα radiation (λ=1.5405Å) Tube voltage: 45kV Tube current: 40mA High-speed detector: X'Celerator + Ni filter Micro-optics: Monocapillary, diameter 0.1 mm Measurement angle: 70~80° Goniometer: Radius 240mm

[0049] In the above measurement, T 004 The diffraction intensity of T is the diffraction intensity (area intensity) of the XRD peak with a peak top at 2θ = 72.5 ± 1°. 220 The diffraction intensities of the above are confirmed as the diffraction intensities (area intensities) of the XRD peaks having a peak top at 2θ=74±1°.

[0050] The shape of the sintered body of this embodiment may be, for example, at least one selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral. Furthermore, any shape may be used as long as it is suitable for various applications and achieves the intended purpose.

[0051] The sintered body of this embodiment preferably has a ball drop strength of 1 J or more, and more preferably 1.5 J or more. The ball drop strength is an index of impact resistance, and the higher this value, the higher the impact resistance. The ball drop strength of the sintered body can be, for example, 10 J or less, 5 J or less, or 4 J or less.

[0052] The ball drop strength in this embodiment is the energy imparted to a sintered body by a falling weight when the sintered body is broken after being dropped from a predetermined ball drop height. The ball drop strength can be calculated using the following formula, and is preferably a value for a sample thickness of 2 mm.

[0053] Falling strength (J) = Mass of falling weight (g) × Falling height (mm) × Gravitational acceleration (m / s 2 ) The acceleration due to gravity is 9.8 m / s 2 Just use

[0054] The ball drop strength can be measured in the same manner as in the above-mentioned ball drop test, except that the ball is dropped from any height as shown below. Drop height: 50~500mm

[0055] Breakage can be determined by the state in which the measurement sample is divided into two or more pieces (FIG. 6(a)). On the other hand, if a crack occurs that does not reach from one end to the other (FIG. 6(b)), it can be considered that no breakage has occurred. If no breakage occurs in the ball drop test at a specific drop height, the drop height can be increased in 50 mm increments up to 500 mm and the test can be repeated until breakage occurs, and visual observation can be performed in the same manner. In this embodiment, for measurement samples that do not break in the ball drop test at a drop height of 500 mm, the ball drop strength can be conveniently determined to be >5J (more than 5J).

[0056] The sintered body of this embodiment preferably exhibits improved impact resistance due to plastic deformation, rather than improved impact resistance due to improved hardness. Because plastic deformation tends to occur easily, the Vickers hardness (Hv) of the sintered body of this embodiment is preferably 12 GPa or less, more preferably 11 GPa or less, and even more preferably 10 GPa or less.

[0057] In this embodiment, the Vickers hardness can be measured by a method in accordance with JIS R1610: 2003. The following conditions can be exemplified as conditions for measuring the Vickers hardness. Measurement sample: (sample thickness) 1.5±0.5mm (Measurement surface roughness) Ra≦0.02μm Measurement load: 10kgf

[0058] Measurements can be performed using a common Vickers tester (e.g., MV-1, manufactured by Matsuzawa) equipped with a diamond square pyramid indenter. The indenter is statically pressed into the surface of the test sample, and the diagonal length of the indentation formed on the surface of the test sample is measured visually. Using the obtained diagonal length, the Vickers hardness can be calculated using the following formula. Hv=F / {d 2 / 2sin(α / 2)}

[0059] In the above formula, Hv is Vickers hardness (GPa), F is the measurement load (10 kgf), d is the diagonal length of the indentation mark (mm), and α is the facing angle of the indenter (136°).

[0060] An example of an index of fracture resistance of the sintered body in this embodiment is fracture toughness. The fracture toughness value is the fracture toughness value (MPa m 0.5) The fracture toughness value is measured using a columnar sintered body sample with a support distance of 30 mm, a width of 4 mm, and a thickness of 3 mm, and the average value of 10 measurements can be used as the fracture toughness value of the sintered body of this embodiment. JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method. The IF method is a simple measurement method, so there is a large variation in the measured values ​​for each measurement. Therefore, the absolute values ​​of the fracture toughness value of this embodiment and the fracture toughness value measured by the IF method cannot be compared.

[0061] The color tone of the sintered body of this embodiment is arbitrary, but it is possible to select a color tone according to CIE1976(L * a * b * ) Lightness in color space L * For example, the lightness L is 80 or more, further 85 or more, and further 90 or more. * The upper limit is 100 or less.

[0062] Lightness L * The lightness L can be measured using a general spectrophotometer (for example, CM-700d, manufactured by Konica Minolta) in accordance with the method of JIS Z8722. * The measurement conditions are as follows: It is preferable to perform the measurement using a black board as the background (so-called black background measurement). Light source: F2 light source Viewing angle: 10° Measurement method: SCI

[0063] The measurement sample is a disk-shaped sintered body with a diameter of 20 mm and a thickness of 2.7 mm, and the surface to be evaluated is mirror-polished (Ra≦0.02 μm) to evaluate the color tone. The effective area for color tone evaluation is 10 mm in diameter.

[0064] The sintered body of this embodiment, particularly a sintered body that does not contain a pigment, has the above-mentioned lightness L * In this case, the saturation a * and b * For example, the saturation a of the sintered body of this embodiment tends to be small.* and b * are -6≦a * ≦-2 and 10≦b * ≦30.

[0065] The sintered body of the present embodiment can be applied to the applications of conventional sintered bodies, particularly zirconia sintered bodies such as structural materials, optical materials, and dental materials, but can also be used as components that require relatively high impact resistance, such as decorative articles, covers for accessories such as watches and housings, and exterior components for portable electronic devices such as mobile phones.

[0066] Further preferred embodiments include the following. (1) A sintered body containing one or more stabilizers selected from the group consisting of calcia, magnesia, and ceria, and yttria, with the remainder being zirconia, wherein the stabilizer content is 2 mol% or more and 7.5 mol% or less, and the yttria content is more than 0 mol% and less than 1.5 mol%, and wherein the sintered body has a region in which the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal is more than 0 and 1.0 or less relative to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal. (2) The sintered body according to (1) above, wherein the stabilizer is ceria. (3) The sintered body according to (1) or (2), wherein the total content of the stabilizer and the yttria is 4 mol % or more and 7.5 mol % or less. (4) The sintered body according to any one of (1) to (3) above, wherein the sintered body comprises a region in which the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal relative to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal is greater than 0 and not greater than 1.0. <Other embodiments> Another embodiment of the present disclosure is a sintered body having a region where an impact mark is formed when an impact force is applied.

[0067] Another embodiment of the present disclosure is a sintered body characterized in that an impact mark is formed when an impact force is applied.

[0068] Another embodiment of the present disclosure is a sintered body characterized in that a recess is formed by a drop ball test in which a DuPont drop ball tester conforming to JIS K 5600 5-3 is used to drop a 300 g weight from a drop height of 350 mm at room temperature.

[0069] Another embodiment of the present disclosure is a sintered body having a region where the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal relative to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal is more than 0 and 1.0 or less, and after an impact force is applied, the sintered body has a region where the intensity of the powder X-ray diffraction peak of the (004) plane of the tetragonal crystal relative to the intensity of the powder X-ray diffraction peak of the (220) plane of the tetragonal crystal is more than 1.0 and 10 or less.

[0070] In these embodiments, the sintered body is preferably a zirconia sintered body, more preferably a partially stabilized zirconia sintered body, even more preferably an yttria- and ceria-stabilized zirconia sintered body, and even more preferably an yttria- and ceria-stabilized zirconia sintered body having an yttria content of 1.0 mol% or more and less than 1.5 mol%.

[0071] The method for producing the sintered body of this embodiment will be described below.

[0072] The sintered body of this embodiment may be produced by any method as long as it satisfies the above requirements. An example of the method for producing the sintered body of this embodiment is a production method including a step of sintering a compact containing two or more stabilizer sources and zirconia.

[0073] The molded body to be subjected to the above step (hereinafter also referred to as "sintering step") is a molded body (green compact) containing two or more stabilizer sources and zirconia.

[0074] The stabilizer source may contain an element that becomes a stabilizer upon sintering, and may be a compound containing one or more elements selected from the group consisting of yttria, calcia, magnesia, and ceria, or precursors thereof, namely, yttrium (Y), calcium (Ca), magnesium (Mg), and cerium (Ce) (hereinafter, a stabilizer source when the stabilizer is yttria will also be referred to as an "yttria source" or the like). The stabilizer source is preferably a compound containing at least one of yttria and ceria, or precursors thereof, namely, yttrium and cerium, and more preferably at least one of a compound containing yttria and yttrium and at least one of a compound containing ceria and cerium.

[0075] The yttria source may be at least one of yttria and its precursor yttrium compound, and may be one or more selected from the group consisting of yttrium chloride, yttria, and yttrium carbonate, with yttria being preferred.

[0076] The ceria source may be at least one of ceria and a cerium compound that serves as a precursor thereof, and may be one or more selected from the group consisting of cerium chloride, ceria, and cerium carbonate, with cerium chloride being preferred.

[0077] The calcia source may be at least one of calcia and a calcium compound that serves as a precursor thereof, and may include one or more selected from the group consisting of calcium chloride, calcia, calcium carbonate, and calcium hydrogen carbonate, with calcia being preferred.

[0078] The magnesia source may be at least one of magnesia and a magnesium compound that serves as a precursor thereof, and examples thereof include one or more selected from the group consisting of magnesium chloride, magnesia, magnesium carbonate, and magnesium hydrogen carbonate, with magnesia being preferred.

[0079] The content of the stabilizer source in the compact may be the same as the content of the stabilizer in the target sintered body.

[0080] When a sintered body containing alumina is produced, the compact may contain an alumina source. The alumina source is at least one of alumina (Al2O3) and a compound containing aluminum (Al) that is a precursor thereof, and includes one or more selected from the group consisting of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, and alumina, and alumina is preferred.

[0081] The content of the alumina source in the compact may be the same as the alumina content in the target sintered body.

[0082] To improve shape stability, the molded body may contain a binder. The binder may be any organic binder used in molding ceramics, and examples thereof include one or more selected from the group consisting of acrylic resin, polyolefin resin, wax, and plasticizer. The binder content may be, for example, 25 to 65% by volume, as the ratio of binder to the volume of the molded body.

[0083] The shape of the molded body may be any shape suitable for the purpose, taking into consideration shrinkage due to sintering, and examples thereof include at least one selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral shapes.

[0084] The molded body can be produced by any method, including mixing zirconia, a stabilizer source, and, if necessary, an alumina source, and molding the mixture. Alternatively, stabilizer-containing zirconia may be used instead of or in addition to the zirconia and stabilizer source.

[0085] When stabilizer-containing zirconia is used as the zirconia, the stabilizer can be incorporated into the zirconia by any method, such as mixing a hydrated zirconia sol with a stabilizer source in an amount equivalent to the desired stabilizer content, followed by drying, calcining, and washing with water.

[0086] Any mixing method may be used, preferably at least one of dry mixing and wet mixing, more preferably wet mixing, and even more preferably wet mixing using a ball mill.

[0087] The molding method may be any known molding method, and is preferably at least one selected from the group consisting of uniaxial pressing, isostatic pressing, injection molding, extrusion molding, rolling granulation, and slip casting, more preferably at least one of uniaxial pressing and isostatic pressing, and even more preferably at least one of cold isostatic pressing and uniaxial pressing (powder press molding).

[0088] In the sintering step, the molded body is sintered to obtain a sintered body. Any sintering method can be used, and examples include known sintering methods such as atmospheric sintering, pressure sintering, and vacuum sintering. Atmospheric sintering is a preferred sintering method, and because it is simple, atmospheric sintering is preferably used alone. This allows the sintered body of this embodiment to be obtained as a so-called atmospheric sintered body. Atmospheric sintering is a method of sintering by simply heating the molded body (or calcined body) without applying an external force during sintering.

[0089] The conditions for atmospheric sintering include a sintering temperature of 1250°C to 1600°C, preferably 1300°C to 1580°C, or 1300°C to 1560°C. The sintering atmosphere may be at least one of an air atmosphere and an oxygen atmosphere, and the air atmosphere is preferred. This allows the ceria to be stabilized by tetravalent cerium (Ce 4+ ) consists of [Example]

[0090] The present embodiment will be specifically described below with reference to examples, but the present embodiment is not limited to these examples. (Confirmation of plastic deformation area) The presence or absence of plastic deformation regions in the sintered samples was confirmed by a ball drop test using a DuPont ball drop tester (H-50, manufactured by Toyo Seiki Co., Ltd.) conforming to JIS K 5600 5-3. The test conditions are as follows: Falling weight: (shape) A spherical hard ball with a diameter of 6.35 mm, i.e., a cylindrical punch with a height of 10 mm and a spherical tip with a diameter of 6.35 mm. (Mass) 300g, that is, a 300g weight made of SUS, rectangular parallelepiped, 80mm wide x 20mm thick x 30mm high Drop height: 350mm Measurement sample: A sintered body in the shape of a plate measuring 40 mm long x 30 mm wide x 2 mm thick, with a surface roughness of Ra ≦ 0.02 μm on both surfaces (40 mm long x 30 mm wide surfaces; main surfaces) To prevent the sample pieces from scattering, the measurement sample was placed on the sample stage of the ball drop tester, with one surface (40 mm long x 30 mm wide) of the measurement sample secured with double-sided tape. After placement, tape was applied along the length of the surface opposite the secured surface of the measurement sample, securing the measurement sample in place. A striking die was placed so that the falling weight would fall near the center of the secured sample, and the ball drop test was conducted.

[0091] (Measurement of falling ball strength) The ball drop strength was measured in the same manner as the ball drop test for confirming the plastic deformation region, except for changing the ball drop height. That is, the condition of the test specimen after dropping the weight was visually confirmed, and the ball drop strength at the ball drop height at which the test specimen was broken was calculated using the following formula. Falling ball strength (J) = Mass of falling weight (g) x Falling height (mm) x Gravitational acceleration (9.8 m / s 2 )

[0092] Breakage was judged to have occurred when the test sample was broken into two or more pieces. Note that a state in which minute fragments such as chipping occurred and the test sample maintained its plate-like shape was not considered to have broken. If no breakage occurred in the ball drop test at a specific drop height, the test was repeated by increasing the drop height in 50 mm increments up to 500 mm until breakage occurred. For test samples that did not break in the 500 mm drop test, the ball drop strength was conveniently determined to be >5J (more than 5J). (impact mark depth) The depth of the impact mark was measured at 20x magnification using a standard laser microscope (VK-9500 / VK-9510, manufactured by Keyence Corporation). A line profile was taken passing through the center of the impact mark, and the length (L1) of the deepest part was measured in the Z-axis direction at 0.5 μm / step. Then, a line profile was taken in the same manner, perpendicular to the line profile, and the length (L2) of the deepest part was measured in the Z-axis direction. The lengths of both deepest parts obtained were averaged (= (L1 + L2) / 2), and the obtained length was used as the depth of the impact mark. (Vickers hardness) The Vickers hardness was measured using a common Vickers tester (device name: MV-1, manufactured by Matsuzawa Co., Ltd.) equipped with a square pyramidal indenter made of diamond.

[0093] The indenter was statically pressed into the surface of the test sample, and the diagonal length of the indentation formed on the surface of the test sample was measured visually. The obtained diagonal length was used to calculate the Vickers hardness (GPa) according to the above formula. (density) The measured density of a sintered sample is the ratio of the volume measured by Archimedes' method to the mass measured by mass measurement (g / cm 3 ) was calculated. (I (004) / (220) ) Crystalline phase of sintered sample, T 004 and T 220 The diffraction intensity was measured using a micro-area XRD (device name: X'pert PRO MPD, manufactured by Spectris). The measurement conditions are as follows. Radiation source: CuKα radiation (λ=1.5405Å) Tube voltage: 45kV Tube current: 40mA High-speed detector: X'Celerator + Ni filter Microscopic optical system: Monocapillary, diameter 0.1 mm Measurement angle: 70~80° Goniometer: Radius 240mm

[0094] Before the test and after the confirmation of the plastic deformation region, micro-area XRD measurements were carried out on the impact core and areas other than the impact core of the measurement sample. (004) / (220) was calculated according to the following formula: I (004) / (220) =(T 004 Diffraction intensity) / (T 220 diffraction intensity)

[0095] (Color measurement) The color tone of the sintered body samples was measured according to JIS Z8722. A general spectrophotometer (device name: CM-700d, manufactured by Konica Minolta) was used for the measurement, and measurements were made against a black background using a black board on the back. The measurement conditions were as follows: Light source: F2 light source Viewing angle: 10° Measurement method: SCI

[0096] The sintered body samples used were disk-shaped samples with a diameter of 20 mm and a thickness of 2.7 mm. One surface of the sintered body sample was mirror-polished (Ra≦0.02 μm), and this surface was used as the evaluation surface for evaluating the color tone. The effective area for color tone evaluation was 10 mm in diameter.

[0097] Example 1 A hydrous zirconia sol was obtained by hydrolysis of an aqueous zirconium oxychloride solution. Yttria and cerium chloride heptahydrate were added and mixed with the hydrous zirconia sol to achieve an yttria concentration of 1.1 mol% and a ceria concentration of 3.4 mol%, respectively. After mixing, the mixture was dried in air and calcined at 1155°C for 2 hours in air to obtain calcined yttria-ceria stabilized zirconia powder. The calcined powder was washed with pure water and dried to obtain zirconia powder consisting of yttria and ceria stabilized zirconia with an yttria content of 1.1 mol% and a ceria content of 3.4 mol%.

[0098] The obtained powder and α-alumina powder containing 5% by mass of alumina were added to pure water to form a slurry, which was then ground and mixed for 18 hours in a ball mill using zirconia balls with a diameter of 10 mm as the grinding medium. The ground and mixed slurry was dried to obtain the zirconia powder of this example, which contained 5% by mass of alumina and the remainder being yttria- and ceria-stabilized zirconia with an yttria content of 1.1 mol% and a ceria content of 3.4 mol%.

[0099] The resulting powder was granulated to form powder granules, which were then packed into a plate-shaped mold measuring 40 mm long x 30 mm wide. A plate-shaped compact (green compact) was obtained by uniaxial pressing at a compacting pressure of 50 MPa and cold isostatic pressing (CIP) at a compacting pressure of 196 MPa. The resulting compact was sintered under the following conditions to obtain the sintered compact of this example, which consisted of yttria-ceria stabilized zirconia containing 5% alumina by mass, with the remainder containing 1.1 mol% yttria and 3.4 mol% ceria. The sintering conditions are shown below. Sintering method: Atmospheric pressure sintering Sintering atmosphere: Air Sintering temperature: 1550℃ Sintering time: 2 hours

[0100] Example 2 The zirconia powder of this example, which consisted of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 3.9 mol%.

[0101] The sintered body of this example, consisting of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0102] Example 3 The zirconia powder of this example, which consisted of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.1 mol% yttria and 5.0 mol% ceria, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 5.0 mol%.

[0103] A sintered body of this example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.1 mol% yttria and 5.0 mol% ceria.

[0104] Example 4 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 0.7 mol% yttria and 5.0 mol% ceria, was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 0.7 mol% and the ceria concentration was 5.0 mol%, respectively.

[0105] The sintered body of this example, consisting of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 0.7 mol% yttria and 5.0 mol% ceria, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0106] Example 5 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.0 mol% yttria and 3.6 mol% ceria, was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 1.0 mol% and the ceria concentration was 3.6 mol%, respectively.

[0107] The sintered body of this example, consisting of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.0 mol% yttria and 3.6 mol% ceria, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0108] Comparative Example 1 The zirconia powder of this comparative example, which contained 5 mass% alumina and the remainder yttria-ceria stabilized zirconia with an yttria content of 1.5 mol% and a ceria content of 3.4 mol%, was obtained in the same manner as in Example 1, except that yttria was added to and mixed with the hydrated zirconia sol so that the yttria concentration was 1.5 mol%.

[0109] A sintered body for this comparative example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 1.5 mol% yttria and 3.4 mol% ceria.

[0110] Comparative Example 2 The zirconia powder of this comparative example was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 2.0 mol% and the ceria concentration was 3.9 mol%. The zirconia powder contained 5 mass% alumina and the remainder was yttria-ceria stabilized zirconia with an yttria content of 2.0 mol% and an ceria content of 3.9 mol%.

[0111] A sintered body for this comparative example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 2.0 mol% yttria and 3.9 mol% ceria.

[0112] Comparative Example 3 The zirconia powder of this comparative example was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 3.0 mol% and the ceria concentration was 3.9 mol%. The zirconia powder contained 5 mass% alumina and the remainder was yttria-ceria stabilized zirconia with an yttria content of 3.0 mol% and an ceria content of 3.9 mol%.

[0113] A sintered body for this comparative example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 5 mass% alumina and the remainder containing 3.0 mol% yttria and 3.9 mol% ceria.

[0114] Comparative Example 4 A zirconia powder of this comparative example was obtained in the same manner as in Example 1, except that yttria was not added to the hydrated zirconia sol. The zirconia powder contained 5% by mass of alumina and the remainder was ceria-stabilized zirconia with a ceria content of 3.4 mol%.

[0115] A sintered body of this comparative example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used, and the sintered body was made of ceria-stabilized zirconia containing 5 mass % alumina and the remainder containing 3.9 mol % ceria.

[0116] Comparative Example 5 A zirconia powder of this comparative example, made of yttria-stabilized zirconia with an yttria content of 3.0 mol%, was obtained in the same manner as in Example 1, except that yttria was added to and mixed with the hydrated zirconia sol so that the yttria concentration was 3.0 mol%, and that cerium chloride heptahydrate and α-alumina powder were not used.

[0117] A sintered body of this comparative example made of yttria-stabilized zirconia with an yttria content of 3.0 mol% was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used and the sintering temperature was set to 1500°C.

[0118] The results of the above examples and comparative examples are shown in the table below.

[0119] [Table 1]

[0120] In the table above, the "Impact Mark Formation" column indicates that impact marks were observed after the ball drop test, but are marked with a "Good" (◯), and those that were not marked with a "Poor" (X). Figure 7 shows the appearance of the sintered body of Example 1 after the ball drop test. From Figure 7, it can be seen that the area where the falling weight made contact during the ball drop test formed an impact mark (depression) without any cracks or other damage, i.e., the impact mark (depression) is a trace of plastic deformation. Figure 8 shows a magnified appearance of the impact mark (magnification: 20x) observed under an optical microscope. The impact mark was a round depression with a diameter of approximately 2.8 mm, and the depth of the impact mark (depression) relative to the thickness of the sintered body was 2.5. Furthermore, all of Examples 1 to 5, which had an yttria content of 0.7 mol% or more but less than 1.5 mol%, were sintered bodies with a tetragonal crystal phase, a zirconia content of 95% by mass, and a relative density equivalent to 98% or more. Impact marks, which are traces of plastic deformation, could be visually confirmed in these sintered bodies, similar to those in Fig. 7. In Examples 1 to 5, no effect of the ceria content on the formation of impact marks was observed, but it was confirmed that all of the sintered bodies of these Examples had a falling ball strength of 1 J or more, regardless of the ceria content.

[0121] FIG. 9 shows the appearance of the sintered body of Comparative Example 3 after the ball drop test, as observed under an optical microscope (magnification: 20x). In Comparative Example 3, it can be observed that no impact marks due to plastic deformation were formed, but cracks due to Hertzian fracture propagated, resulting in the destruction of the sintered body. On the other hand, in sintered bodies with an yttria content of 1.5 mol% or more, no impact marks were observed, and the ball drop strength was 0.4 J or less, confirming that the impact resistance was extremely low. Furthermore, in Comparative Example 4, which did not contain yttria, defects such as cracks occurred during sintering, and a measurable sintered body could not be obtained. Furthermore, it was confirmed from Comparative Example 5 that the sintered body containing only yttria as a stabilizer did not have a plastic deformation region.

[0122] The sintered body of Example 1 had a surface I (004) / (220) and I other than the core of the attack (004) / (220) was 0.55, while the I (004) / (220) The value was 3.43. This shows that the ball drop test caused regions with different crystal orientations to appear in the sintered body.

[0123] The sintered bodies of Examples 1 to 6 all have similar color tones. For example, the sintered body of Example 1 has a color tone of L. * = 92.41, a * =-3.89 and b * = 16.01, and the sintered body of Example 4 has L * =93.21, a * =-3.18 and b * =18.38.

[0124] Example 6 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia with an yttria content of 1.1 mol% and a ceria content of 3.9 mol%, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 3.9 mol%, and that a slurry was prepared without using α-alumina powder.

[0125] The sintered body of this example, consisting of yttria-ceria stabilized zirconia with a yttria content of 1.1 mol% and a ceria content of 3.9 mol%, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0126] Example 7 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 1 mass% alumina, with the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 3.9 mol%, and α-alumina powder was added to form a slurry so that the alumina content was 1 mass%.

[0127] The sintered body of this example, which was made of yttria-ceria stabilized zirconia containing 1 mass% alumina and the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0128] Example 8 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 3 mass% alumina, with the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 3.9 mol%, and α-alumina powder was added to form a slurry so that the alumina content was 3 mass%.

[0129] The sintered body of this example, which was made of yttria-ceria stabilized zirconia containing 3 mass% alumina and the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0130] Example 9 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 7 mass% alumina, with the remainder containing 1.1 mol% yttria and 3.9 mol% ceria, was obtained in the same manner as in Example 1, except that cerium chloride heptahydrate was added to and mixed with the hydrated zirconia sol so that the ceria concentration was 3.9 mol%, and α-alumina powder was added to form a slurry so that the alumina content was 7 mass%.

[0131] A sintered body of this example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 7 mass% alumina and the remainder containing 1.1 mol% yttria and 3.9 mol% ceria.

[0132] Example 10 The zirconia powder of this example, which contained 10 mass% alumina and the remainder was yttria-ceria stabilized zirconia with a yttria content of 1.1 mol% and a ceria content of 3.4 mol%, was obtained in the same manner as in Example 1, except that α-alumina powder was added to form a slurry so that the alumina content was 10 mass%.

[0133] A sintered body of this example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used, which consisted of yttria-ceria stabilized zirconia containing 10 mass% alumina and the remainder containing 1.1 mol% yttria and 3.4 mol% ceria.

[0134] Example 11 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia containing 16.4 mass% alumina and the remainder containing 1.1 mol% yttria and 3.4 mol% ceria, was obtained in the same manner as in Example 1, except that α-alumina powder was added to form a slurry so that the alumina content was 16.4 mass%.

[0135] A sintered body of this example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used. The sintered body was made of yttria-ceria stabilized zirconia containing 16.4 mass% alumina, with the remainder being 1.1 mol% yttria and 3.4 mol% ceria.

[0136] The results of the above examples are shown in the table below.

[0137] [Table 2]

[0138] From the above table, it can be seen that the sintered bodies of these examples have a relative density equivalent to 98% or more, and that impact marks are formed regardless of the presence or absence of alumina content and its content. Furthermore, it can be seen that a plastic deformation region exists when the zirconia content is in the range of 83.6% by mass or more and 100% by mass or less. The depth of the impact core relative to the thickness of the sintered body for the sintered body of Example 6 was 2.6. It can also be seen that the Vickers hardness tends to increase as the alumina content increases.

[0139] The sintered bodies of Examples 6 to 11 all have similar color tones. For example, the sintered body of Example 6 has a color tone similar to that of L * =83.98, a * =-4.69 and b * = 20.00, and the sintered body of Example 9 is L * = 94.38, a * =-3.64 and b * = 14.13, and the sintered body of Example 10 has L * =95.26, a * =-3.45 and b * =14.22.

[0140] Example 12 The sintered body of this example was obtained in the same manner as in Example 6, except that the sintering temperature was 1450°C.

[0141] Example 13 The sintered body of this example was obtained in the same manner as in Example 7, except that the sintering temperature was 1450°C.

[0142] Example 14 The sintered body of this example was obtained in the same manner as in Example 8, except that the sintering temperature was 1450°C.

[0143] Example 15 The sintered body of this example was obtained in the same manner as in Example 2, except that the sintering temperature was 1450°C.

[0144] Example 16 The sintered body of this example was obtained in the same manner as in Example 9, except that the sintering temperature was 1450°C.

[0145] The results of the above examples are shown in the table below.

[0146] [Table 3]

[0147] From Table 2 and the table above, it can be seen that even pressureless sintered bodies obtained at higher sintering temperatures have a relative density equivalent to 98% or more, have a plastic deformation region, and tend to have higher hardness and lower ball drop strength as the sintering temperature decreases.

[0148] The sintered bodies of Examples 12 to 16 all have similar color tones. For example, the sintered body of Example 12 has a color tone similar to that of L. * =83.52, a * =-4.75 and b * =24.35, and the sintered body of Example 15 was L * =94.18, a * =-3.93 and b * =16.79.

[0149] Example 17 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia with an yttria content of 1.2 mol% and a ceria content of 3.6 mol%, was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 1.2 mol% and the ceria concentration was 3.6 mol%, respectively, and that α-alumina powder was not used.

[0150] The sintered body of this example, consisting of yttria-ceria stabilized zirconia with a yttria content of 1.2 mol% and a ceria content of 3.6 mol%, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0151] Example 18 The zirconia powder of this example, consisting of yttria-ceria stabilized zirconia with an yttria content of 1.0 mol% and a ceria content of 4.0 mol%, was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 1.0 mol% and the ceria concentration was 4.0 mol%, respectively, and that α-alumina powder was not used.

[0152] The sintered body of this example, consisting of yttria-ceria stabilized zirconia with a yttria content of 1.0 mol% and a ceria content of 4.0 mol%, was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used.

[0153] Comparative Example 6 The zirconia powder of this comparative example, consisting of yttria-ceria stabilized zirconia with an yttria content of 3.0 mol% and a ceria content of 3.9 mol%, was obtained in the same manner as in Example 1, except that yttria and cerium chloride heptahydrate were added to and mixed with the hydrated zirconia sol so that the yttria concentration was 3.0 mol% and the ceria concentration was 3.9 mol%, respectively, and that α-alumina powder was not used.

[0154] A sintered body for this comparative example was obtained in the same manner as in Example 1, except that the obtained zirconia powder was used, with the remainder being yttria-ceria stabilized zirconia containing 3.0 mol% yttria and 3.9 mol% ceria.

[0155] The results of the examples and comparative examples are shown in the table below.

[0156] [Table 4]

[0157] It can be seen from Examples 17 and 18, as well as from Example 12, that even sintered bodies made of yttria and ceria-stabilized zirconia without containing alumina have a plastic deformation region. On the other hand, the sintered body of Comparative Example 6, although having a lower ceria content than Example 18, does not have a plastic deformation region, and the I of the surface before the drop test (004) / (220) and I other than the core of the attack (004) / (220) is 0.38, and the I of the impact center after the drop ball test (004) / (220) is 0.80, and I (004) / (220) No significant changes were observed. [Explanation of symbols]

[0158] 100: Overview of the drop ball test 101: Sintered body 102: Punch 103a, 103b: Guide 104: Falling Weight 105: Fixing tape 106: Drop ball tester specimen stand 107: Protective tape 200: Sintered body of this embodiment after drop test 201: Sintered body 202: Impact mark (concave) 203: Depth of impact mark (dent) 300: Conventional sintered body after drop test 301: Sintered body 302: Defect (crack) 400: A diagram showing the state of the sintered body placed on the sample stage of the drop tester 401: Sintered body 402: Fixing tape 403: Drop ball tester specimen stand 404: Double-sided tape (protective tape) 500: Diagram showing how to measure impact mark depth 501: Sintered body 502: Impact mark (concave) 503A,B: Line profile 504: Depth of deepest part (L1 or L2) 601: Sintered body in divided state 602: Defect (crack) 702: Impact mark (concave)

Claims

1. A sintered body comprising one or more stabilizers selected from the group consisting of calcia, magnesia, and ceria, and zirconia containing yttria, wherein the yttria content is less than 1.5 mol%, the ratio (molar ratio) of the stabilizer other than yttrium to yttrium is 1.2 or more and 5.0 or less, and further comprising a region where an impact mark is formed when an impact force is applied, wherein the ratio of the powder X-ray diffraction peak intensity of the tetragonal (004) plane to the powder X-ray diffraction peak intensity of the tetragonal (220) plane is more than 0 and 1.0 or less.

2. 2. The sintered body according to claim 1, wherein the impact mark is a recess.

3. 3. The sintered body according to claim 1, wherein the stabilizer content is 3 mol % or more and 10 mol % or less.

4. 4. The sintered body according to claim 1, wherein the stabilizer is two or more selected from the group consisting of yttria, calcia, magnesia, and ceria.

5. 5. The sintered body according to claim 1, wherein the stabilizer is yttria and ceria.

6. 6. The sintered body according to claim 1, wherein the yttria content is less than 1.5 mol%.

7. The sintered body according to claim 1 , wherein the ceria content is 2 mol % or more and 7.5 mol % or less.

8. The sintered body according to claim 1 , which contains alumina.

9. 9. The sintered body according to claim 5, wherein a molar ratio of the stabilizing element other than yttrium to yttrium is 1.2 or more and 5.0 or less.

10. CIE 1976 (L ＊ a ＊ b ＊ ) Lightness L in color space ＊ The sintered body according to claim 1 , wherein the sintered body has a modulus of 80 or more.

11. 11. The sintered body according to claim 1, having a Vickers hardness of 12 GPa or less.

12. A member comprising the sintered body according to any one of claims 1 to 11.

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