Zirconia sintered body containing titanium and yttrium in solid solution

Abstract

Provided are at least one of: a transparent zirconia sintered body containing titanium and yttrium in solid solution, which is less likely to break than another transparent zirconia sintered body containing titanium and yttrium in solid solution; a method for producing same; and an application thereof.　This transparent zirconia sintered body containing titanium and yttrium in solid solution contains not less than 3.5 mol% and less than 6.0 mol% of yttrium and contains 6.0-18.5 mol% of titanium and comprises cubic crystal grains that include tetragonal domains.

Description

Titanium and yttrium solid-doped zirconia sintered body

[0001] The present disclosure relates to a sintered body of zirconia in which titanium and yttrium are solid-solved.

[0002] A sintered body made of zirconia in which titanium and yttrium are dissolved and whose crystalline phase is composed solely of cubic crystals is known to have high transparency (Patent Document 1). However, such a sintered body has poor mechanical properties. Therefore, improvements in the mechanical properties of such a transparent sintered body have been studied.

[0003] For example, Patent Document 2 discloses that a sintered body of titanium and yttrium-doped zirconia having a three-point bending strength of 255 MPa and transparency can be obtained by controlling the crystal grain size of a primary sintered body subjected to hot isostatic pressing (hereinafter also referred to as "HIP") treatment. Also, Patent Document 3 discloses that a sintered body of titanium and yttrium-doped zirconia having a three-point bending strength of 300 MPa or more and transparency can be obtained by controlling the degree of reduction of titanium (Ti) in HIP treatment.

[0004] JP 62-091467 A JP 2011-011970 A JP 2011-102227 A

[0005] The sintered bodies disclosed in Patent Documents 2 and 3 exhibit both a high linear transmittance and a high three-point bending strength. Therefore, they are less susceptible to defects than conventional zirconia sintered bodies containing titanium and yttrium as a solid solution, which are transparent. However, these sintered bodies have low resistance to the development of fractures such as cracks, and once a defect occurs, the fracture progresses rapidly.

[0006] An object of the present disclosure is to provide a sintered body of zirconia in which titanium and yttrium are dissolved, which exhibits transparency and in which fracture is less likely to progress than a conventional sintered body of zirconia in which titanium and yttrium are dissolved, and which also exhibits transparency; a method for producing the same; and / or uses of the same.

[0007] In this disclosure, we have investigated a titania-yttria-zirconia sintered body having transparency. As a result, we have found that by controlling the crystal grain structure, transparency does not decrease even in compositions that have traditionally been thought to decrease transparency. Furthermore, we have found that a sintered body having such a composition becomes a titania-yttria-zirconia sintered body with improved resistance to the propagation of fracture.

[0008] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows. [1] A zirconia sintered body in which titanium and yttrium are dissolved, the yttrium content being 3.5 mol% or more and less than 6.0 mol%, and the titanium content being 6.0 mol% or more and 18.5 mol% or less, and the zirconia sintered body being composed of cubic crystal grains containing tetragonal domains. [2] The sintered body according to the above item [1], which contains alumina. [3] The sintered body according to the above item [1] or [2], in which the crystallite diameter calculated from the half-width of a peak having a peak top at 2θ = 74.0 ± 0.3° in the XRD pattern is 1,400 nm or less. [4] The sintered body according to any one of the above items [1] to [3], in which the average crystal grain size is 5 μm or more and 50 μm or less. [5] The sintered body according to any one of the above [1] to [4], wherein the in-line transmittance at a sample thickness of 1±0.1 mm and a measurement wavelength of 600 nm is 45% or more. [6] Fracture toughness value (K ＩＣ ) is 1.5 MPa m ０．５[7] The sintered body according to any one of [1] to [5] above, having a three-point bending strength of 280 MPa or more. [8] A method for producing a sintered body according to any one of [1] to [7] above, comprising: a primary sintering step of atmospherically sintering a molded body containing a zirconia source, a yttrium source, and a titanium source, the yttrium content of which is 3.5 mol% or more and less than 6.0 mol%, and a titanium content of 6.0 mol% or more and 18.5 mol% or less, in an oxidizing atmosphere at 1260°C or more to obtain a primary sintered body; a pressure sintering step of pressure-sintering the primary sintered body in a reducing atmosphere at 1500°C or more to obtain a pressure-treated body; and a heat treatment step of heat-treating the pressure-treated body in an oxidizing atmosphere. [9] The production method according to [8] above, wherein the molded body is obtained by a molding step of molding a raw material powder obtained by a mixing method in which a mixed raw material powder of a zirconia source and a yttrium source is mixed with a titanium source.

[10] The measured density of the primary sintered body is 5.35 g / cm ３ 6.00g / cm or more ３

[11] The manufacturing method according to any one of [8] to

[10] above, wherein the pressure sintering is a hot isostatic pressing treatment.

[12] The manufacturing method according to any one of [8] to

[11] above, wherein the reducing atmosphere is a weakly reducing atmosphere.

[13] The manufacturing method according to any one of [8] to

[12] above, wherein the temperature drop rate from the holding temperature to 1000°C in pressure sintering is 50°C / min or more and 300°C / min or less.

[14] A member comprising the sintered body according to any one of [1] to [7] above.

[0009] According to the present disclosure, it is possible to provide a sintered body of zirconia in which titanium and yttrium are solid-dissolved, which exhibits transparency and is less susceptible to fracture than a conventional sintered body of zirconia in which titanium and yttrium are solid-dissolved, and which also exhibits transparency, a method for producing the same, and / or uses thereof.

[0010] Electron beam diffraction map of the sintered body of Example 1 Electron beam diffraction map of the sintered body of Comparative Example 5 Rietveld analysis results of the sintered body of Example 1

[0011] The sintered body of the present disclosure will be described below by showing an example of an embodiment. The configurations and parameters disclosed herein can be arbitrarily combined, and the upper and lower limits of the values ​​disclosed herein can be arbitrarily combined.

[0012] The "composition" is a substance having a certain composition, and examples thereof include one or more selected from the group consisting of powder, granules, a molded body, a calcined body, and a sintered body.

[0013] The term "powder" refers to a composition that is an aggregate of powder particles and has flowability. The term "zirconia powder" refers to a powder whose main component is zirconia, or a powder that essentially consists of zirconia.

[0014] "Granular powder" refers to a powder made up of granular particles, which are particles (tertiary particles) formed by the slow aggregation of powder particles (particularly, at least one of primary particles and secondary particles) due to physical forces, and may contain organic components.

[0015] A "green body" is a composition having a certain shape composed of powder particles agglomerated by physical force, and in particular, a composition in a state in which the composition has not been subjected to heat treatment after the shape has been imparted (e.g., after molding). A "zirconia green body" is a green body whose main component is zirconia, and is essentially made of zirconia. In this embodiment, the terms "green body" and "green compact" are used interchangeably.

[0016] A "sintered body" is a composition having a certain shape and composed of crystal grains, and is a composition in a state in which it has been heat-treated at a temperature equal to or higher than the sintering temperature. A "zirconia sintered body" is a sintered body containing zirconia as the main component, or even a sintered body essentially consisting of zirconia.

[0017] The "stabilizing element" is an element that has the function of stabilizing the crystalline phase of zirconia by dissolving in zirconia.

[0018] The "powder X-ray diffraction pattern" is an XRD pattern of a composition obtained by powder X-ray diffraction (hereinafter also referred to as "XRD") measurement under the following conditions: Radiation source: CuKα radiation (λ=0.15418 nm) Measurement mode: Continuous scan Scan speed: 1° / min Measurement range: 2θ=20° to 80° Acceleration voltage / current: 40 kV / 40 mA Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm

[0019] The XRD measurement can be performed using a general X-ray diffractometer (for example, Ultima IV, manufactured by RIGAKU Corporation). When the composition is a sintered body, the surface thereof may be polished to a surface roughness Ra≦0.02 μm, and the XRD measurement may be performed on the surface.

[0020] Examples of XRD peaks corresponding to the respective crystal planes of zirconia measured in the above-mentioned XRD measurement include XRD peaks having peak tops at 2θ as follows:

[0021] XRD peak corresponding to monoclinic (111) plane: 2θ = 31 ± 0.5° XRD peak corresponding to monoclinic (11-1) plane: 2θ = 28 ± 0.5° XRD peak corresponding to tetragonal (111) plane: 2θ = 30 ± 0.5° XRD peak corresponding to cubic (111) plane: 2θ = 30 ± 0.5° XRD peak corresponding to tetragonal (400) plane: 2θ = 72.8 ± 0.3° XRD peak corresponding to tetragonal (004) plane: 2θ = 74.8 ± 0.3° XRD peak corresponding to cubic (400) plane: 2θ = 74.0 ± 0.3° The XRD peak corresponding to the tetragonal (111) plane and the XRD peak corresponding to the cubic (111) plane are measured as a single overlapping peak.

[0022] XRD peaks can be detected by profile fitting an XRD pattern after smoothing and background removal (hereinafter also referred to as a "processed XRD pattern") using a split pseudo-Voigt function. Smoothing, background processing, and XRD pattern analysis, such as XRD peak detection, can be performed using a program such as an analysis program attached to the X-ray diffractometer (e.g., Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation) under the following conditions. In this embodiment, the peaks detected by this program are referred to as XRD peaks. The XRD pattern and processed XRD pattern may contain minute peaks (so-called noise) that are not detected in the fitting. Scherrer constant: 1.000 Smoothing method: β-spline smoothing, γ threshold value = 1.50 Background removal method: straight line connecting end points Kα2 ray removal method: intensity ratio = 0.497 Peak search method: peak top method, α cut value = 3.00 Profiling fitting method: divided pseudo-Voigt function

[0023] [Sintered body] This embodiment is a zirconia sintered body containing titanium and yttrium, which has an yttrium content of 3.5 mol% or more and less than 6.0 mol%, and a titanium content of 6.0 mol% or more and 18.5 mol% or less, and is composed of cubic crystal grains including tetragonal domains. This results in a sintered body having transparency comparable to that of conventional zirconia sintered bodies composed of cubic crystal grains, but having higher mechanical strength than these.

[0024] The sintered body of this embodiment is a zirconia sintered body, which is a sintered body having zirconia as the main component (matrix), a so-called zirconia sintered body. Among zirconia sintered bodies, the sintered body of this embodiment is particularly a zirconia sintered body in which titanium and yttrium are solid-solved, a so-called titania-yttria-zirconia sintered body. Furthermore, the sintered body of this embodiment is a transparent sintered body, and further a transparent zirconia sintered body, a so-called transparent zirconia sintered body.

[0025] The fact that titanium and yttrium are dissolved in zirconia, and further that the sintered body of this embodiment does not contain titanium and yttrium that are not dissolved in zirconia (undissolved titanium and yttrium), can be determined by the absence of XRD peaks corresponding to titanium compounds and yttrium compounds in the XRD pattern. Note that the inclusion of undissolved titanium and yttrium to an extent that is not detected in the XRD pattern, or the inclusion of undissolved titanium and yttrium to an extent that does not impair the effects of the sintered body of this embodiment, is permissible. Even in such cases, for convenience, this embodiment considers that it does not contain undissolved titanium and yttrium.

[0026] Yttrium (Y) dissolves in zirconia and functions as a stabilizing element that stabilizes the crystalline phase of zirconia. On the other hand, titanium (Ti) dissolves in zirconia, but is not thought to have the function of stabilizing the crystalline phase of zirconia in the sintered body of this embodiment.

[0027] The sintered body of this embodiment has a yttrium content of 3.5 mol% or more but less than 6.0 mol%. If the yttrium content is less than 3.5 mol%, the sintered body will have low transparency, and even if it has translucency, it will have extremely low transparency. If the yttrium content is 6.0 mol% or more, it will have low resistance to the progression of fracture and will be easily broken. As a result, it will be difficult to apply it to decorative components and other transparent ceramic applications. In order to obtain a sintered body having a fracture toughness value and transparency that can be used in decorative members, etc., the yttrium content is 4.0 mol% or more, 4.2 mol% or more, 4.35 mol% or more, or 4.5 mol% or more, and also 5.8 mol% or less, 5.5 mol% or less, less than 5.5 mol%, 5.2 mol% or less, 5.0 mol% or less, or 4.7 mol% or less. It is preferable that the yttrium content is 4.0 mol% or more and 5.8 mol% or less, 4.0 mol% or more and less than 5.5 mol%, 4.2 mol% or more and 5.5 mol% or less, 4.2 mol% or more and less than 5.5 mol%, 4.2 mol% or more and 5.2 mol% or less, 4.35 mol% or more and 5.2 mol% or less, or 4.5 mol% or more and 5.0 mol% or less.

[0028] The content of yttrium in this embodiment is zirconia (ZrO ２ ) and the amount of substance [mol] of the solid solution element converted to oxide, Y ２ O ３ This is the ratio [mol %] of the converted amount of substance [mol] of yttrium.

[0029] In this embodiment, the solute element is an element that replaces the zirconium (Zr) cation in zirconia and is contained in the zirconia in the form of a cation. Specific solute elements include one or more selected from the group consisting of titanium (Ti), yttrium (Y), erbium (Er), terbium (Tb), calcium (Ca), magnesium (Mg), lanthanum (La), cerium (Ce), gadolinium (Gd), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The solute elements contained in the sintered body of this embodiment are preferably only yttrium and titanium, and preferably do not contain lanthanum.

[0030] The sintered body of this embodiment preferably does not contain undissolved solute elements, but may contain undissolved solute elements within a range that does not impair the effects of the sintered body of this embodiment. In this embodiment, the absence of undissolved solute elements can be confirmed by detecting no XRD peaks corresponding to compounds of the solute elements in the XRD pattern.

[0031] The sintered body of this embodiment has a titanium content of 6.0 mol% or more and 18.5 mol% or less. If the titanium content is less than 6.0 mol%, crystal grains containing tetragonal crystals are likely to be generated, making it difficult to obtain a sintered body composed of crystal grains consisting of cubic crystals. If the titanium content exceeds 18.5 mol%, defects will occur during the production (sintering) of the sintered body, making it impossible to obtain a sintered body. The titanium content is 7.0 mol% or more, 8.0 mol% or more, 9.0 mol% or more, 9.3 mol% or more, 10.0 mol% or more, or 12.0 mol% or more, and can be 17.0 mol% or less, 15.0 mol% or less, or 13.0 mol% or less, and is preferably 7.0 mol% or more and 17.0 mol% or less, 8.0 mol% or more and 15.0 mol% or less, 9.0 mol% or more and 13.0 mol% or less, 9.3 mol% or more and 13.0 mol% or less, or 10.0 mol% or more and 13.0 mol% or less.

[0032] In this embodiment, the titanium content is zirconia (ZrO ２ ) and the amount of substance [mol] of the solid solution element converted to oxide, TiO ２ This is the ratio [mol %] of the converted amount of titanium substance [mol].

[0033] In the sintered body of this embodiment, the titanium and yttrium may have the above-mentioned contents, but the total content of titanium and yttrium may be 9.5 mol% or more, 10.0 mol% or more, 13.0 mol% or more, or 15.0 mol% or more, and may be less than 24.5 mol%, 20.0 mol% or less, 18.0 mol% or less, or 17.0 mol% or less, and further examples include 9.5 mol% or more and less than 24.5 mol%, 10.0 mol% or more and 20.0 mol% or less, 13.0 mol% or more and 20.0 mol% or less, or 15.0 mol% or more and 17.0 mol% or less. The total content of the solute elements in this embodiment may also be a similar amount.

[0034] The sintered body of this embodiment may be a sintered body made of zirconia in which titanium and yttrium are solid-solved. However, it is also possible to use a sintered body made of alumina (Al ２ O ３The inclusion of alumina tends to increase the strength.

[0035] The sintered body of this embodiment does not need to contain alumina (alumina content of 0% by mass), but may contain alumina, as long as the alumina content of the sintered body of this embodiment is 0% by mass or more. The alumina content may be 0.15% by mass or less, 0.08% by mass or less, or less than 0.05% by mass. Furthermore, when alumina is contained, the alumina content may be more than 0% by mass, 0.01% by mass or more, or 0.04% by mass or more. The alumina content of the sintered body of this embodiment may be 0% by mass or more and 0.15% by mass or less, or 0% by mass or more and less than 0.05% by mass, and further preferably more than 0% by mass and 0.15% by mass or less, 0.01% by mass or more and 0.08% by mass or less, or 0.04% by mass or more and 0.08% by mass or less.

[0036] The content of alumina in this embodiment is the ratio of aluminum to the total mass of metal elements of the sintered body converted into oxides (hereinafter also referred to as "metal mass"). ２ O ３ This can be determined from the converted mass percentage [mass %].

[0037] The sintered body of this embodiment is a zirconia sintered body in which titanium and yttrium are dissolved. Since it is a sintered body with a zirconia matrix, its composition contains titanium, yttrium, and, as necessary, alumina in addition to zirconia. That is, the composition of the sintered body of this embodiment is essentially such that the remainder, excluding yttrium, titanium, and aluminum, is zirconia.

[0038] The sintered body of this embodiment preferably does not contain impurities, but may contain impurities as long as the effect is exhibited. Specific examples of impurities include metal elements and alkali metal elements. The sintered body of this embodiment also contains hafnia (HfO), which is an inevitable impurity in zirconia. ２ In this embodiment, when calculating values ​​related to the composition, such as density, hafnia may be regarded as zirconia.

[0039] The composition of the sintered body of this embodiment may be determined as follows, for example, in the case of a sintered body of zirconia containing alumina and in which titanium and yttrium are solid-solved: Metal mass [g] = Al ２ O ３ + TiO ２ +Y ２ O ３ + ZrO ２ Yttrium content [mol%] = {Y ２ O ３ / (ZrO ２ +Y ２ O ３ + TiO ２ )} × 100 Titanium content [mol%] = {TiO ２ / (ZrO ２ +Y ２ O ３ + TiO ２ )} × 100 Content of solid solution element [mol%] = {(Y ２ O ３ + TiO ２ ) / (ZrO ２ +Y ２ O ３ + TiO ２ )} × 100 Aluminum content [mass%] = {Al ２ O ３ / (Al ２ O ３ + TiO ２ +Y ２ O ３ + ZrO ２ ) x 100

[0040] The sintered body of this embodiment is composed of cubic crystal grains, and further composed of cubic crystal grains of zirconia in which yttrium and titanium are solid-solved. Cubic crystal is a crystalline phase having a shape without anisotropy. Since the sintered body of this embodiment is composed of cubic crystal grains, light scattering due to the anisotropy of the crystal structure does not occur, and the sintered body exhibits high transparency. Note that the sintered body of this embodiment may contain alumina crystal grains in addition to the cubic crystal grains (cubic crystal grains of zirconia in which yttrium and titanium are solid-solved).

[0041] In this embodiment, for convenience, the zirconia crystal phase may be considered to consist of three crystal phases: cubic, tetragonal, and monoclinic. Furthermore, if no tetragonal or monoclinic XRD peaks are detected in the XRD pattern of the sintered body, the sintered body may be considered to consist of cubic crystal grains. The sintered body of this embodiment may be considered to consist of cubic zirconia, and the zirconia contained in the sintered body of this embodiment may be considered to consist of cubic crystal grains. Specifically, the sintered body of this embodiment may be confirmed to consist of cubic crystal grains by having a peak with a peak top at 2θ = 74.0 ± 0.3° in the XRD pattern, and not having a peak with a peak top at 2θ = 72.8 ± 0.3° or a peak with a peak top at 2θ = 74.8 ± 0.3°.

[0042] Furthermore, the sintered body of this embodiment preferably has an XRD pattern that is fitted to a cubic model in a Rietveld analysis using as references an XRD pattern of a zirconia crystal structure model (cubic model) consisting of only cubic crystals and an XRD pattern of a zirconia crystal structure model (mixed crystal model) consisting of a mixed phase of cubic crystals and tetragonal crystals, respectively. This confirms that the sintered body of this embodiment does not contain tetragonal crystal grains or monoclinic crystal grains.

[0043] The Lieveld analysis may be performed using an analysis program (for example, Rietan-FP), and the cubic crystal model and the mixed crystal model may use a structural model in which the cubic crystal is a cubic crystal having the space group Fm-3m as the cubic crystal and the tetragonal crystal is a tetragonal crystal having the space group P42nmc as the tetragonal crystal.

[0044] As described above, the sintered body of the present embodiment has a yttrium content of 1000 kJ / cm2, and is generally a mixed-phase zirconia consisting of tetragonal and cubic crystal grains. In contrast, the sintered body of the present embodiment has the above-mentioned yttrium content and is composed of only a cubic crystal phase.

[0045] The sintered body of this embodiment preferably has a moderately high cubic crystallinity, and the crystallite diameter (hereinafter also referred to as "crystallite diameter") calculated from the full width at half maximum (hereinafter also referred to as "FWHM") of the peak having a peak top at 2θ = 74.0 ± 0.3 ° in its XRD pattern is preferably 1400 nm or less, 1050 nm or less, 800 nm or less, or 650 nm or less. The crystallite diameter can be exemplified as 150 nm or more, 300 nm or more, 400 nm or more, or 500 nm or more, and is preferably 300 nm or more to 1400 nm or less, 400 nm or more to 800 nm or less, or 400 nm or more to 650 nm or less.

[0046] The crystallite diameter in this embodiment may be calculated by the following formula.

[0047] D = κλ / β cos θ In the above formula, D is the crystallite diameter (nm), κ is the Scherrer constant (κ = 1.000), λ is the wavelength of the measured X-ray (when CuKα rays are used as the radiation source, λ = 0.1548 nm), β is the half-width (°) of the peak having a peak top at 2θ = 74.0 ± 0.3°, and θ is the Bragg angle.

[0048] The half-width of the peak having a peak top at 2θ=74.0±0.3° may be determined by fitting the processed XRD pattern obtained by the above-mentioned method.

[0049] The crystal grains constituting the sintered body of this embodiment are cubic crystal grains containing tetragonal domains. The inclusion of tetragonal domains increases resistance to fracture propagation, and even if defects such as cracks occur in the sintered body of this embodiment, the expansion of the defects is suppressed. As a result, the fracture toughness value is higher than that of conventional sintered bodies made of cubic crystal grains, making the sintered body less susceptible to fracture.

[0050] The sintered body of this embodiment is mainly composed of zirconia crystal grains (more specifically, zirconia crystal grains in which yttrium and titanium are solid-dissolved). The crystal grains are structures (particles) composed of multiple crystallites. In this embodiment, a domain (crystal domain) is a region in a crystal grain composed of crystallites having the same crystal structure. Furthermore, a tetragonal domain is a region in a cubic crystal grain composed of crystallites having tetragonal crystals. Typically, cubic crystal grains are composed only of crystallites having cubic crystals (cubic domains only). In contrast, the crystal grains that compose the sintered body of this embodiment are cubic crystal grains that include tetragonal domains. Therefore, the crystal grains in the sintered body of this embodiment are crystal grains that include tetragonal domains in addition to cubic domains, and can also be considered as crystal grains composed of cubic domains and tetragonal domains.

[0051] The fact that the sintered body of this embodiment is composed of cubic crystal grains including tetragonal domains can be confirmed by the following method. That is, by detecting the above-mentioned XRD peaks, it can be confirmed that the sintered body is composed of cubic crystal grains. In addition, by obtaining an electron diffraction map of the crystal grains observed by nanodiffraction mapping using a transmission electron microscope (hereinafter also referred to as "TEM") measured under the following conditions, it can be confirmed that the crystal grains include tetragonal domains by observing electron diffraction spots (hereinafter also referred to as "spots") corresponding to the tetragonal crystal planes. Analysis orientation: tetragonal

[100] Acceleration voltage: 200 Kv Observation magnification: 250,000x

[0052] TEM nanodiffraction mapping and electron beam diffraction mapping may be obtained using a general TEM (for example, JEM-F200, manufactured by JEOL Ltd.) and a general electron beam diffraction device (for example, 4D-STEM, manufactured by Gatan).

[0053] Figures 1 and 2 are diffraction patterns of cubic crystal particles having tetragonal domains and cubic crystal particles having no tetragonal domains, respectively. It can be seen that Figure 1 has spots corresponding to tetragonal crystals (the arrows in Figure 1 indicate spots corresponding to the tetragonal (100) plane and its equivalent planes). On the other hand, Figure 2 does not have spots corresponding to tetragonal crystals. The presence of spots corresponding to tetragonal crystals in the diffraction pattern, as in Figure 1, confirms that the crystal particles contain tetragonal domains.

[0054] The average crystal grain size of the sintered body of this embodiment is 5 μm or more, 10 μm or more, or 15 μm or more, and may be 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. Since the smaller the average crystal grain size, the higher the mechanical strength tends to be, the average crystal grain size of the sintered body of this embodiment is preferably 5 μm or more and 50 μm or less, 10 μm or more and 40 μm or less, 10 μm or more and 30 μm or less, or 15 μm or more and 30 μm or less.

[0055] The average crystal grain size is the average diameter of the crystal grains constituting the sintered body, and is a value obtained by a planimetric method from an SEM observation image obtained by observing the surface of the sintered body with a scanning electron microscope (hereinafter also referred to as "SEM"). Specifically, in order to suppress variations in the observed crystal grains due to differences in the SEM observation points, two or more, or even two to four, SEM observation images are used, and the number of crystal grains within a circle (n ｃ ) and the number of crystal grains on the circumference (N ｉ Draw two circles so that the total number of circles is 100±30. The crystal grain size of each circle is determined by the planimetric method for all the circles drawn, and the average value is taken as the average crystal grain size.

[0056] SEM observation for measuring the average crystal grain size can be performed using a general scanning electron microscope (for example, JSM-IT500LA, manufactured by JEOL Ltd.). SEM observation can be performed by appropriately setting the observation magnification so that the number of crystal grains to be image-analyzed (crystal grains whose grain boundaries are observed continuously in the SEM observation image) is 450±50. The conditions for SEM observation can be as follows: Acceleration voltage: 15 kV, Exposure current: 40 nA, Observation magnification: 400x to 10,000x.

[0057] Prior to the measurement, the sintered body sample is subjected to surface grinding using a #200 grinding stone, followed by lapping using diamond abrasives with grain sizes of 3 μm and 1 μm, and then thermally etched in an air atmosphere at a temperature at which the grain boundaries can be confirmed.

[0058] 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 depending on the purpose of various uses, etc.

[0059] The sintered body of this embodiment has transparency, and for example, the linear transmittance (hereinafter also referred to as "It") at a sample thickness of 1±0.1 mm and a measurement wavelength of 600 nm is 45% or more, or even 50% or more. It is one index that indicates transparency, and the higher the It, the higher the transparency. Therefore, the It of the sintered body of this embodiment is preferably 52% or more or 55% or more. While a higher It is preferable, the It of the sintered body of this embodiment can be, for example, 75% or less, 70% or less, 65% or less, or 60% or less. Further examples include 45% to 75%, 50% to 75%, 52% to 70%, 52% to 65%, or 55% to 60%.

[0060] The sintered body of this embodiment preferably has high light transmittance. For example, the total light transmittance (hereinafter also referred to as "Tt") at a sample thickness of 1±0.1 mm and a measurement wavelength of 600 nm is preferably 60% or more. Tt is an index indicating light transmittance, and the higher the Tt, the higher the light transmittance. The sintered body of this embodiment may satisfy the above-mentioned It, and examples of Tt include 65% or more, 70% or more, or 71% or more, and 80% or less, 77% or less, 75% or less, or 73% or less. Examples of Tt of the sintered body of this embodiment include 60% or more and 80% or less, 65% or more and 80% or less, 70% or more and 75% or less, and 71% or more and 75% or less.

[0061] In order to facilitate the production of a transparent member with higher aesthetic appeal, it is preferable that the ratio of It to Tt (hereinafter also referred to as "It / Tt ratio") is high, and the It / Tt ratio of the sintered body of this embodiment is 0.95 or less, 0.90 or less, or 0.85 or less. In order to achieve highly aesthetic transparency, It / Tt is 0.70 or more or 0.75 or less, and examples thereof include 0.70 to 0.95, 0.70 to 0.90, or 0.75 to 0.85.

[0062] In this embodiment, Tt and It are both light transmittances obtained by measurement in accordance with JIS K 7361-1. The ratio of transmitted light (the sum of in-line transmitted light and diffuse transmitted light) to incident light is the total light transmittance [%], and the ratio of in-line transmitted light to incident light is the linear transmittance [%], and the relationship is total light transmittance [%] = linear transmittance [%] + diffuse transmittance [%]. The measurement sample is a disc-shaped sintered body having a sample thickness of 1.0 ± 0.1 mm and a surface roughness Ra ≦ 0.02 μm on both sides, and the measurement device can be a general spectrophotometer (for example, Spectrophotometer V-650, manufactured by JASCO Corporation).

[0063] The sintered body of this embodiment has high transparency and also high resistance to the progression of fracture. The sintered body of this embodiment has a fracture toughness value (K ＩＣ ) is 1.5 MPa m ０．５ Above, 2.0MPa・m ０．５or more or 2.2 MPa m ０．５ It is preferable that the fracture toughness value is high, and the fracture toughness value of the sintered body of this embodiment is 3.0 MPa m ０．５ Below, 2.8MPa・m ０．５ or less or 2.6 MPa m ０．５ For example, it can be 1.5 MPa m ０．５ 3.0MPa・m or more ０．５ Below, 2.0MPa・m ０．５ 3.0MPa・m or more ０．５ or less, or 2.2 MPa m ０．５ 2.8MPa・m or more ０．５ It is preferable that:

[0064] In this embodiment, the "fracture toughness value (K ＩＣ ) 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 may be used as the fracture toughness value of the sintered body of this embodiment. A general strength testing machine (e.g., an Instron Testing Machine Model 5582, manufactured by Instron) may be used for the measurement. JIS R 1607 specifies two methods for measuring fracture toughness: the IF method and the SEPB method. The IF method tends to produce larger values ​​than the SEPB method. Furthermore, since the IF method is a simple measurement method, there is a large variation in the measured values ​​from measurement to measurement. Therefore, the absolute values ​​of the fracture toughness value of this embodiment and the fracture toughness value measured by the IF method cannot be compared. Similarly, the absolute values ​​of the fracture toughness values ​​measured by methods other than the SEPB method cannot be compared with those measured by the SEPB method.

[0065] The sintered body of this embodiment preferably has high strength so that it is less likely to break when processed, and the three-point bending strength of the sintered body of this embodiment is preferably 280 MPa or more, 310 MPa or more, 350 MPa or more, or 420 MPa or more. The strength of the sintered body of this embodiment may be sufficient as long as it is suitable for processing, and examples of the three-point bending strength include 800 MPa or less, 750 MPa or less, 700 MPa or less, or 600 MPa or less, and examples thereof include 280 MPa or more and 800 MPa or less, 310 MPa or more and 700 MPa or less, or 420 MPa or more and 600 MPa or less.

[0066] The "three-point bending strength" in this embodiment is a value measured by a method conforming to JIS R 1601. The measurement sample is a columnar shape with a width of 4 mm, a thickness of 3 mm, and a length of 45 mm, with a support distance of 30 mm, and the measurement is performed by applying a load in the horizontal direction of the measurement sample. A general strength testing machine (for example, a desktop universal precision testing machine AGX-10kNX, manufactured by Shimadzu Corporation) can be used for the measurement.

[0067] The sintered body of this embodiment may be a sintered body (hereinafter also referred to as a "composite sintered body") composed of the sintered body of this embodiment and a sintered body other than the sintered body of this embodiment. The compound sintered body is a sintered body in which the sintered body of this embodiment and a sintered body other than the sintered body of this embodiment are integrated by sintering, thereby resulting in a more aesthetically pleasing member. Here, the "integrated state by sintering" is different from a state in which the sintered body is integrated by the use of an adhesive, a physical structure such as bonding, or other physical action, and means that the sintered body of this embodiment and a sintered body other than the sintered body of this embodiment are integrated by forming an interface.

[0068] The sintered body other than the sintered body of this embodiment contained in the compound sintered body may be any sintered body having different aesthetic properties from the sintered body of this embodiment, but is preferably a zirconia sintered body, and more preferably an opaque zirconia sintered body. Examples of opaque zirconia sintered bodies include zirconia sintered bodies having an It of 0% or more and 5% or less, further 0% or more and 3% or less, or even 0% or more and 1% or less, particularly 0% or more and 0.5% or less. Examples of sintered bodies other than the sintered body of this embodiment contained in the compound sintered body include zirconia sintered bodies exhibiting chromatic or achromatic colors, and examples of achromatic zirconia sintered bodies include white, gray, or black zirconia sintered bodies. On the other hand, examples of chromatic zirconia sintered bodies include zirconia sintered bodies exhibiting red, orange, yellow, green, blue, indigo, or purple, and even black zirconia sintered bodies.

[0069] The sintered body of this embodiment can be used as a transparent ceramic, and can be used, for example, for one or more applications selected from the group consisting of optical components, exterior components, and decorative components. The sintered body of this embodiment may also be used as a component comprising the sintered body. [Method for Manufacturing Sintered Body] The method for manufacturing the sintered body of this embodiment may be any method that can obtain a sintered body satisfying the above-described configuration. A preferred manufacturing method includes a method for manufacturing a sintered body (hereinafter also referred to as the "manufacturing method of this embodiment") that includes a primary sintering step in which a molded body containing a zirconia source, a yttrium source, and a titanium source, and having an yttrium content of 3.5 mol% or more but less than 6.0 mol% and a titanium content of 6.0 mol% or more and 18.5 mol% or less, is pressure-sintered in an oxidizing atmosphere at 1260°C or more to obtain a primary sintered body; a pressure-sintering step in which the primary sintered body is pressure-sintered in a reducing atmosphere at 1500°C or more to obtain a pressure-treated body; and a heat-treatment step in which the pressure-treated body is heat-treated in an oxidizing atmosphere. According to the manufacturing method of this embodiment, it is possible to obtain a zirconia sintered body having a crystal phase consisting solely of cubic crystals, even though the zirconia has a composition that was previously thought to be capable of producing only a zirconia sintered body having a crystal phase consisting of a mixed phase of tetragonal and cubic crystals.

[0070] The manufacturing method of this embodiment includes a primary sintering step of atmospherically sintering a compact containing a zirconia source, an yttrium source, and a titanium source, the compact having an yttrium content of 3.5 mol% or more and less than 6.0 mol% and a titanium content of 6.0 mol% or more and 18.5 mol% or less, to obtain a primary sintered body. This produces a primary sintered body to be subjected to pressure sintering.

[0071] In the primary sintering step, a molded body having an yttrium content of 3.5 mol % or more and less than 6.0 mol % and a titanium content of 6.0 mol % or more and 18.5 mol % or less, and including a zirconia source, an yttrium source, and a titanium source, is provided.

[0072] The zirconia source is zirconia (ZrO ２ ) is sufficient.

[0073] The yttrium source may be any yttrium compound, and may be at least one selected from the group consisting of oxides, hydroxides, oxyhydroxides, and halides containing yttrium. At least one of yttrium chloride and oxide, and further yttrium oxide (yttria; Y ２ O ３ ) and yttrium chloride (YCl ３ ) is preferred, and yttrium oxide is more preferred.

[0074] The molded body may contain yttrium-doped zirconia (yttrium-stabilized zirconia) in addition to or instead of zirconia and a yttrium compound. Furthermore, it is preferable that the molded body contains yttrium-doped zirconia instead of zirconia and a yttrium compound (i.e., the zirconia source and the yttria source are yttrium-doped zirconia). The yttrium-doped zirconia is zirconia stabilized by dissolving yttrium in a solid solution, that is, so-called yttrium-stabilized zirconia.

[0075] The titanium source may be any titanium compound, and may be at least one selected from the group consisting of oxides, hydroxides, oxyhydroxides, and halides containing titanium. Examples of the titanium source include at least one of chlorides and oxides containing titanium, and further titanium oxide (titania; TiO ２ ) and titanium chloride (TiCl ４ ) or further titanium oxide.

[0076] The molded body may contain an alumina source. The alumina source may be at least one of alumina and a precursor thereof, and alumina (Al ２ O ３ ) is preferred.

[0077] The molded body may contain a binder. The inclusion of a binder improves operability (handling) and shape retention. The binder may be any binder that can be used for granulating and molding ceramics, and is preferably an organic binder. Examples of organic binders include one or more selected from the group consisting of polyvinyl alcohol, polyvinyl butyrate, wax, and acrylic resin, preferably at least one of polyvinyl alcohol and an acrylic resin, and more preferably an acrylic resin. In this embodiment, the acrylic resin is a polymer containing at least one of an acrylic acid ester and a methacrylic acid ester. Specific examples of binders include one or more selected from the group consisting of AS-1100, AS-1800, and AS-2000 (all product names, manufactured by Toagosei Co., Ltd.).

[0078] The composition of the molded body is such that the yttrium content is 3.5 mol% or more and less than 6.0 mol%, and the titanium content is 6.0 mol% or more and 18.5 mol% or less, and further, it is sufficient that the molded body contains metal elements in a composition similar to that of the target sintered body, and that the molded body contains metal elements in a composition similar to that of the above-mentioned sintered body.

[0079] When a binder is contained, the content of the binder is, for example, 0.5% by mass or more or 1% by mass or more, and 10% by mass or less or 5% by mass or less. The content of the binder can be calculated as follows.

[0080] {(W２ -W １ ) / W ２}×100 In the above formula, W １ is the mass [g] of the compact after heat treatment in air at 250°C or higher and 400°C or lower, W ２ is the mass [g] of the molded body before the heat treatment. Note that due to differences in calculation methods, the composition of the molded body including the binder does not necessarily have to be 100 mass%.

[0081] The molded body may be produced by any method as long as the molded body is obtained in which the zirconia source, the yttrium source, the titanium source, and, if necessary, the alumina source are uniform. For example, the molded body production method may include a molded body production method including a molding step of molding powder containing the zirconia source, the yttrium source, and the titanium source.

[0082] The molding step may be performed using powders similar to the zirconia source, yttrium source, and titanium source (hereinafter, each referred to as "starting raw materials" and collectively referred to as "raw material powders"). The raw material powders may also contain an alumina source. Furthermore, the manufacturing method of this embodiment includes a pressure sintering step. Since pressure sintering is less affected by the sinterability of the starting materials, the starting materials may be commercially available powders (e.g., reagent-grade powders) or granular powders.

[0083] The starting materials (zirconia source, yttrium source, titanium source, and alumina source) are preferably powders having similar particle sizes, and the average particle sizes thereof are, for example, 0.2 μm or more or 0.4 μm or more and 0.6 μm or less or 0.5 μm or less, and preferably 0.4 μm or more and 0.6 μm or less, or 0.4 μm or more and 0.5 μm or less.

[0084] The average particle size of the raw material powder may be the same as that of the starting raw material, and is preferably 0.4 μm to 0.6 μm, or 0.4 μm to 0.5 μm. Furthermore, in order to obtain a primary sintered body that is likely to produce tetragonal domains during pressure sintering under the conditions described below, the ratio of the standard deviation of particle size [μm] to the average particle size [μm] of the raw material powder (hereinafter also referred to as "particle size standard deviation") is preferably 0.5 or less or 0.3 or less. Since actual powders have a particle size distribution, the particle size standard deviation of the raw material powder can be greater than 0 or 0.01 or more, and is preferably greater than 0 to 0.5, greater than 0 to 0.3, or 0.01 to 0.3.

[0085] The raw material powders may be mixed by at least one of a dry method and a wet method so that the starting materials are homogeneous, and wet mixing is preferred. Specifically, for example, mixing may be performed by at least one of agitation mixing, a ball mill, and a bead mill.

[0086] A preferred method for mixing the starting materials includes mixing a mixed raw material powder of a zirconia source and a yttrium source with a titanium source. The mixed raw material powder may also contain an alumina source. The raw material powder is a precursor of a molded body containing a zirconia source as a main component, an yttrium source, a titanium source, and an alumina source. By mixing the titanium source with zirconia in a state in which the yttrium source and the alumina source have been incorporated, it is believed that titanium is more likely to be dissolved in zirconia in a state in which tetragonal domains are more likely to be formed in the subsequent primary sintering and pressure sintering. A more preferred mixing method includes mixing a slurry containing a mixed raw material powder of a zirconia source and a yttrium source with a slurry containing a titanium source. Mixing slurries with controlled milling particle sizes makes it easier to control the physical properties of the resulting raw material powder, and it is believed that tetragonal domains in the sintered body obtained by the subsequent primary sintering and pressure sintering are more likely to be formed stably.

[0087] The molding method may be any known molding method for ceramic molded bodies (compressed powder bodies) that is suitable for the desired shape of the molded body. Examples of the molding method include one or more selected from the group consisting of uniaxial pressing, injection molding, slip casting, sheet molding, and cold isostatic pressing (hereinafter also referred to as "CIP") treatment, with one or more selected from the group consisting of uniaxial pressing, injection molding, and CIP treatment being preferred, and primary pressing and CIP treatment being more preferred.

[0088] The molded body to be subjected to the primary sintering step is preferably a molded body obtained by a molding step of molding a raw material powder obtained by a mixing method of mixing a mixed raw material powder of a zirconia source and a yttrium source with a titanium source, and more preferably a molded body obtained by a molding step of molding a raw material powder obtained by a mixing method of mixing a slurry containing a mixed raw material powder of a zirconia source and a yttrium source with a slurry containing a titanium source.

[0089] In the primary sintering step, the above-described compact is pressurelessly sintered in an oxidizing atmosphere at 1260°C or higher to obtain a primary sintered body. With the composition of the compact used in the primary sintering step, such primary sintering results in a sintered body without open pores. In this embodiment, pressureless sintering refers to a sintering method in which the object to be sintered (e.g., a compact or calcined body) is heated without applying an external force. With the composition of the compact used in the primary sintering step, if primary sintering is performed at a temperature lower than 1260°C, the sintered body obtained after pressure sintering will have significantly low transparency or no transparency at all. The holding temperature for primary sintering (hereinafter also referred to as the "primary sintering temperature") is preferably 1300°C or higher or 1325°C or higher. The upper limit of the primary sintering temperature can be, for example, 1500°C or lower or 1400°C or lower. Preferred pressureless sintering conditions include the following:

[0090] Sintering atmosphere: oxidizing atmosphere, preferably air atmosphere Primary sintering temperature: 1260°C or higher, 1300°C or higher, or 1325°C or higher, and 1500°C or lower or 1400°C or lower Heating rate: 50°C / hour or higher, or 80°C / hour or higher, and 200°C / hour or lower or 120°C / hour or lower The holding time at the holding temperature may be adjusted appropriately depending on the size of the molded body to be subjected to the primary sintering step and the performance of the primary sintering furnace, and can be, for example, 30 minutes to 15 hours, or even 1 hour to 1.5 hours.

[0091] The primary sintered body obtained by the primary sintering step preferably contains only closed pores and has a relative density of 90% or more. In this embodiment, the relative density varies depending on the composition, but the relative density of the primary sintered body is 90% or more and 98% or less. This is because the measured density of the sintered body in the composition range of this embodiment is 5.35 g / cm. ３ Above, 5.40g / cm ３ Above, 5.60g / cm ３ or more than 5.80 g / cm ３ or more, and 6.00 g / cm ３ Below, 5.90g / cm ３ or less than 5.85 g / cm ３ and 5.35 g / cm ３ 6.00g / cm or more ３ Below, 5.40g / cm ３ 5.9g / cm or more ３ Below, 5.60g / cm ３ 5.85g / cm or more ３ Below, 5.80g / cm ３ 5.85g / cm or more ３ The following is preferred:

[0092] In this embodiment, the "measured density" is the density of the sample volume [cm ３ ] to the mass [g] [g / cm ３The mass is determined by weighing the sample, and the volume is determined by Archimedes' method in accordance with JIS R 1634. The Archimedes' method uses ion-exchanged water as a solvent, and pretreatment may be performed by boiling.

[0093] The average crystal grain size of the primary sintered body may be any size that allows pores to be easily eliminated during pressure sintering, and is preferably 1.0 μm or less, and more preferably 0.8 μm or less. The average crystal grain size of the primary sintered body may be 0.1 μm or more or 0.3 μm or more, and may also be 0.1 μm or more to 1.0 μm or less, or 0.3 μm or more to 0.8 μm or less.

[0094] The manufacturing method of this embodiment includes a pressure sintering step in which a primary sintered body is pressure-sintered in a reducing atmosphere to obtain a pressure-treated body. Pressure sintering eliminates closed pores contained in the primary sintered body through mass transfer. As a result, the primary sintered body is densified to the extent that the sintered body exhibits high transparency after heat treatment. If the primary sintered body is sintered in a reducing atmosphere without pressure, a translucent sintered body may be obtained, but such a sintered body will have no transparency or significantly low transparency.

[0095] Pressure sintering is performed in a reducing atmosphere. By pressure sintering in a reducing atmosphere, titanium contained in the primary sintered body is reduced to trivalent titanium (Ti ３＋ ) and the resulting formation of oxygen vacancies. The formation of oxygen vacancies promotes mass transfer, resulting in the efficient elimination of closed pores and a dense sintered body. Furthermore, a sintered body with high transparency can be obtained by the subsequent heat treatment step. Even if the primary sintered body is sintered under atmospheric pressure, the resulting sintered body may have translucency, but a sintered body with both high translucency and high transparency cannot be obtained.

[0096] The reducing atmosphere is preferably a weakly reducing atmosphere, and more preferably an inert atmosphere in which a reducing member coexists, since this facilitates mass transfer suitable for efficient elimination of closed pores. The inert gas atmosphere may be an argon atmosphere or a nitrogen atmosphere, with an argon atmosphere being preferred. The reducing member may be any member made of a reducing material, with a carbon member being preferred.

[0097] In pressure sintering, the primary sintered body is placed in a container and pressure sintered. At least one of the components constituting the pressure sintering furnace (hereinafter also referred to as "furnace components") and the container in which the primary sintered body is placed (hereinafter also referred to as "sintering container") may be a reducing component, and at least one of the furnace components and the sintering container may be made of carbon, and it is preferable that the furnace components and the sintering container are made of carbon.

[0098] A preferred weakly reducing atmosphere is an argon atmosphere or a nitrogen atmosphere in which one or more selected from the group consisting of the heating element, the heat insulating material, and the sintering vessel are carbon members, and a more preferred weakly reducing atmosphere is an argon atmosphere in which the heating element and the sintering vessel are carbon members.

[0099] The pressure sintering may be at least one of a hot press treatment and a hot isostatic press treatment (HIP treatment), and is preferably HIP treatment.

[0100] The holding temperature in pressure sintering (hereinafter also referred to as "pressure sintering temperature") may be any temperature at which elimination of closed pores can be promoted by mass transfer, and is preferably 1500°C or higher, and more preferably 1525°C or higher or 1550°C or higher. If the pressure sintering temperature is lower than 1500°C, the mechanical strength may be increased, but the sintered body will have significantly lower transparency. As the pressure sintering temperature increases, the transparency tends to increase. Since a general-purpose HIP processing device can be used, the holding temperature may be 1700°C or lower, 1650°C or lower, or 1645°C or lower.

[0101] In order to obtain a sintered body having a higher fracture toughness value, the pressure sintering temperature is preferably 1600°C or less, further less than 1600°C, or even 1575°C or less. If the pressure sintering temperature is within the above-mentioned range, a sintered body having both linear transmittance and fracture toughness value can be obtained. On the other hand, if the pressure sintering temperature is appropriately low within the above-mentioned range, a sintered body having both linear transmittance and fracture toughness value and a higher fracture toughness value can be easily obtained. Therefore, the pressure sintering temperature is preferably 1500°C or more and 1645°C or less, further 1500°C or more and 1600°C or less, or even 1525°C or more and 1575°C or less.

[0102] The pressure in the pressure treatment may be any pressure that can promote the elimination of closed pores by the pressure treatment, and may be 50 MPa or more or 100 MPa or more, and may be 200 MPa or less or 170 MPa or less, such as 50 MPa or more and 200 MPa or less, or 100 MPa or more and 170 MPa or less.

[0103] The treatment time at the pressure sintering temperature may be adjusted appropriately depending on the size of the primary sintered body and the characteristics of the pressure sintering furnace, and may be, for example, from 10 minutes to 10 hours, or from 30 minutes to 5 hours.

[0104] In the pressure sintering, the temperature may be increased to the pressure sintering temperature at a rate of 5°C / min or more or 10°C / min or more. There is no upper limit to the rate of temperature increase, but since a general-purpose pressure sintering furnace can be used, the rate of temperature increase can be, for example, 100°C / min or less or 50°C / min or less.

[0105] Since tetragonal domains are likely to be formed in cubic crystal grains, the temperature drop rate from the pressure sintering temperature to 1000°C is preferably 50°C / min or more or 70°C / min or more. The upper limit of the temperature drop rate may be set appropriately depending on the pressure sintering furnace used, but examples include 300°C / min or less or 150°C / min or less. In this embodiment, the temperature drop rate from the pressure sintering temperature to 1000°C is 50°C / min or more and 300°C / min or less, 70°C / min or more and 150°C / min or less, or 70°C / min or more and 100°C / min or less.

[0106] The manufacturing method of this embodiment includes a heat treatment step of heat treating the treated body in an oxidizing atmosphere. ３＋ ) is oxidized to tetravalent titanium (Ti ４＋ ) oxygen defects are eliminated, and the sintered body of this embodiment having transparency can be obtained.

[0107] The oxidizing atmosphere may be an oxygen atmosphere or an air atmosphere, with the air atmosphere being preferred.

[0108] The holding temperature in the heat treatment (hereinafter also referred to as "heat treatment temperature") may be any temperature at which the oxidation of titanium proceeds efficiently, such as 800°C or higher or 850°C or higher, and may be lower than 1200°C or lower than 1100°C, with 800°C or higher but lower than 1200°C, or 850°C or higher but lower than 1100°C being preferred.

[0109] The holding time at the heat treatment temperature may be adjusted appropriately depending on the size of the object to be treated and the performance of the heat treatment furnace, but may be, for example, 30 minutes to 10 hours, or 45 minutes to 3 hours.

[0110] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0111] (Composition Analysis) The composition of the composition was measured by ICP analysis.

[0112] (XRD Measurement) An XRD pattern of the sintered body was obtained by XRD measurement using an X-ray diffractometer (for example, Ultima IV, manufactured by RIGAKU Corporation) under the following conditions.

[0113] Radiation source: CuKα ray (λ=0.15418 nm) Measurement mode: Continuous scan Scan speed: 1° / min Measurement range: 2θ=20° to 80° Acceleration voltage / current: 40 mA / 40 kV Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm Prior to measurement, the surface of the sintered body was polished to a surface roughness Ra≦0.02 μm to serve as a measurement sample, and XRD measurement was performed on that surface.

[0114] Using an analysis program (product name: Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation), smoothing and background removal were performed, and the XRD pattern (processed XRD pattern) was analyzed by profile fitting using a split pseudo-Voigt function. The smoothing, background removal, and analysis conditions are shown below.

[0115] Scherrer constant: 1.000 Smoothing method: smoothing by β-spline, γ threshold value = 1.50 Background removal method: straight line connecting end points Kα2 ray removal method: intensity ratio = 0.497 Peak search method: peak top method, α cut value = 3.00 Profiling fitting method: divided pseudo-Voigt function Prior to measurement, the surface of the sintered body was polished using sandpaper with a grit size of #400 in accordance with JIS R 6001-2, and then lapped using a diamond abrasive with a grit size of 3 μm.

[0116] The obtained XRD patterns were subjected to Rietveld analysis using an analysis program (Rietan-FP) with a cubic crystal model and a mixed crystal model, in which the cubic crystal was a cubic crystal with space group Fm-3m and the tetragonal crystal was a tetragonal crystal with space group P42nmc.

[0117] (Crystallite diameter) In this embodiment, the crystallite diameter was calculated by the following formula.

[0118] D = κλ / β cos θ In the above formula, D is the crystallite diameter (nm), κ is the Scherrer constant (κ = 1.000), λ is the wavelength of the measured X-ray (when CuKα rays are used as the radiation source, λ = 0.1548 nm), β is the half-width (°) of the peak having a peak top at 2θ = 74.0 ± 0.3°, and θ is the Bragg angle.

[0119] The half-value width of the peak having a peak top at 2θ=74.0±0.3° was determined by analysis under the same conditions as in the above-mentioned XRD measurement.

[0120] (Measured density) The measured density is the density of the sample [cm ３The mass was determined from the mass [g] relative to the volume [g] of the sample. The mass was determined by weighing the sample, and the volume was determined by Archimedes' method in accordance with JIS R 1634. The Archimedes' method used ion-exchanged water as the solvent, and pretreatment was performed by boiling.

[0121] (TEM nanodiffraction) Using a field emission transmission electron microscope (device name: JEM-F200, manufactured by JEOL Ltd.) and an electron beam diffractometer (device name: 4D-STEM, manufactured by Gatan Co., Ltd.), TEM nanodiffraction mapping and a diffraction pattern analyzed from the tetragonal

[100] orientation of the crystal grains observed by TEM nanodiffraction mapping were obtained, and tetragonal spots were confirmed. Acceleration voltage: 200 Kv Observation magnification: 250,000 times

[0122] (Total light transmittance and linear transmittance) Tt and It were measured using a general UV-VIS spectrophotometer (device name: Spectrophotometer V-650, manufactured by JASCO Corporation) under the following conditions. In the obtained spectrum, the total light transmittance and linear transmittance at a wavelength of 600 nm were defined as Tt and It, respectively. The measurement sample used was a disk-shaped sintered body with a sample thickness of 1±0.1 mm and a surface roughness Ra≦0.02 μm on both sides. Measurement method: UV-VIS spectrophotometric measurement Measurement method: Double beam method Light source: D2 / WI Measurement wavelength range: 200 nm to 900 nm Data acquisition interval: 0.5 nm

[0123] (Three-point bending strength) Three-point bending strength was measured according to a method in accordance with JIS R 1601. The measurement sample was a columnar shape with a width of 4 mm, a thickness of 3 mm, and a length of 45 mm, with a support distance of 30 mm, and a load was applied horizontally to the measurement sample. A strength testing machine (device name: desktop universal precision testing machine AGX-10kNX, manufactured by Shimadzu Corporation) was used for the measurement.

[0124] (Fracture toughness value) The fracture toughness value (K) was measured by a method conforming to the SEPB method specified in JIS R 1607. ＩＣ ) [MPa m ０．５The fracture toughness of the sintered body of this embodiment was 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. The average value of 10 measurements was used as the fracture toughness value of the sintered body of this embodiment. A strength testing machine (e.g., Instron Testing Machine Model 5582, manufactured by Instron Corporation) was used for the measurement.

[0125] (Average Crystal Grain Size) The average crystal grain size was determined from an SEM observation image obtained using a scanning electron microscope (device name: JSM-IT500LA, manufactured by JEOL Ltd.) under the following conditions.

[0126] Acceleration voltage: 15 kV, Probe current: 40 nA, Observation magnification: 400x to 10,000x. Prior to measurement, the sintered samples were surface-ground using a #200 grinding stone, then lapped using diamond abrasives with grain sizes of 3 μm and 1 μm, and then thermally etched in air for 1 hour. The thermal etching temperature was 100°C lower than the sintering temperature.

[0127] Three SEM observation images were used, and the number of crystal grains (n ｃ ) and the number of crystal grains on the circumference (N ｉ Two circles were drawn so that the total number of circles was 100±30. The crystal grain size of each of the drawn circles was determined by the planimetric method, and the average value was taken as the average crystal grain size.

[0128] Example 1: A yttrium-stabilized zirconia powder containing alumina (5.5 mol% yttrium and 0.05 mass% aluminum) was mixed with pure water. After mixing, the mixture was wet-pulverized in a ball mill until the average particle size was 0.5 μm and the standard deviation of the particle size was 0.1 μm, resulting in a zirconia slurry with a powder content (solid concentration) of 45 mass%. The standard deviation of the particle size of the resulting powder was 0.2.

[0129] On the other hand, titania powder was mixed with pure water and wet-pulverized in a ball mill until the average particle size was 0.5 μm and the standard deviation of the particle size was 0.1 μm, to obtain a titania slurry with a powder content (solid concentration) of 20 mass %. The standard deviation of the particle size of the obtained powder was 0.2.

[0130] The obtained zirconia slurry and titania slurry were mixed so that the mass ratio of the zirconia powder to the titania powder was 92:8, thereby obtaining a mixed slurry containing yttrium-stabilized zirconia powder containing alumina and titania, with an yttrium content of 4.67 mol%, an aluminum content of 0.046 mass%, and a titania content of 8 mass% (12.29 mol%).

[0131] The resulting mixed slurry was spray-dried at 180° C. to obtain a granular powder of yttrium-stabilized zirconia containing alumina and titania, with an yttrium content of 4.67 mol %, an aluminum content of 0.046 mass %, and a titania content of 8 mass %.

[0132] 3 g of the obtained granular powder was filled into a mold having an inner diameter of 25 mm, and then subjected to uniaxial press molding at a pressure of 98 MPa. After molding, the molded product was subjected to CIP treatment at a pressure of 196 MPa to obtain a disk-shaped molded body having a diameter of 25 mm.

[0133] The obtained compact was subjected to primary sintering under the following conditions to obtain a primary sintered body made of titanium and yttrium-doped zirconia containing alumina, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%. The primary sintered body had an average crystal grain size of 0.6 μm and a measured density of 5.82 g / cm. ３ Primary sintering atmosphere: air atmosphere Heating rate: 100°C / hour Holding temperature: 1350°C Holding time: 2 hours

[0134] The obtained primary sintered body was placed in a carbon container with a lid, and the carbon container was placed in a HIP apparatus equipped with a carbon heating element, and then HIP-treated in a weakly reducing atmosphere under the following conditions to obtain a HIP-treated body.

[0135] Pressure medium: argon gas (purity: 99.9%) Heating rate: 10°C / min Holding temperature: 1550°C Holding pressure: 150 MPa Holding time: 1 hour After holding, the temperature was lowered to 1000°C at a rate of 80°C / min.

[0136] The obtained HIP-treated body was heat-treated in an air atmosphere at 900°C for 1 hour, thereby obtaining a sintered body of this example made of titanium and yttrium-doped zirconia containing alumina, in which the yttrium content was 4.67 mol%, the titanium content was 12.29 mol%, and the alumina content was 0.046 mass%.

[0137] FIG. 1 shows the results of TEM diffraction mapping of the sintered body of this example. In FIG. 1, spots of the tetragonal (100) plane and its equivalent tetragonal crystal plane were confirmed (boxed area in FIG. 1), and it was confirmed that all of them were tetragonal spots of 5 nm or less. Furthermore, the Rietveld analysis results of the XRD pattern of the sintered body of this example shown in FIG. 3 confirmed that the sintered body of this example was 100% cubic. This confirmed that the sintered body of this embodiment was a sintered body composed of cubic crystal grains having tetragonal domains. The sintered body of this example had an average crystal grain size of 18 μm and a crystallite diameter of 448 nm.

[0138] Example 2 A sintered body of this example was obtained by the same method as in Example 1, except that the primary sintering temperature was 1300°C. The sintered body was made of alumina-containing titania and yttrium-doped zirconia, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%. The measured density of the obtained primary sintered body was 5.40 g / cm. ３ The sintered body of this example had a crystallite diameter of 934 nm.

[0139] Example 3 A sintered body of this example was obtained by the same method as in Example 1, except that the holding temperature in the HIP treatment was 1500°C. The sintered body was made of alumina-containing titania and yttrium-doped zirconia, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%. The measured density of the obtained primary sintered body was 5.82 g / cm. ３ The sintered body of this example had a crystallite diameter of 804 nm.

[0140] Example 4 A sintered body of this example was obtained by the same method as in Example 1, except that the holding temperature in the HIP treatment was 1600°C. The sintered body was made of alumina-containing titania and yttrium-doped zirconia, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%. The measured density of the obtained primary sintered body was 5.82 g / cm. ３ The sintered body of this example had an average crystal grain size of 36.0 μm and a crystallite diameter of 678 nm.

[0141] Comparative Example 1 A sintered body of this comparative example was obtained, which was made of titanium and yttrium-doped zirconia containing alumina, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%, by the same method as in Example 1, except that the primary sintered body was treated by atmospheric pressure sintering in an air atmosphere at a heating rate of 600°C / hour, a holding temperature of 1550°C, and a holding time of 1 hour, instead of the HIP treatment.

[0142] The sintered body of this comparative example was a sintered body composed of cubic crystal grains and tetragonal crystal grains, and had low light transmittance and no transparency.

[0143] Comparative Example 2 A sintered body of this comparative example, made of titanium and yttrium-doped zirconia containing alumina, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%, was obtained in the same manner as in Example 1, except that the primary sintering temperature was set to 1250° C. Although the sintered body of this comparative example had translucency, it had a low Tt and was not transparent.

[0144] Comparative Example 3 The sintered body of this comparative example was obtained in the same manner as in Example 1, except that the primary sintered body was subjected to atmospheric sintering (reducing atmospheric sintering) in a 95% argon-5% hydrogen mixed gas atmosphere as the reducing atmosphere, a holding temperature of 1550°C, and a holding time of 1 hour, and that the HIP treatment was not performed. Although the sintered body of this comparative example was obtained by sintering in a reducing atmosphere, it had low light transmittance and was not transparent.

[0145] Comparative Example 4 A sintered body of this comparative example, made of titanium and yttrium-doped zirconia containing alumina, with an yttrium content of 4.67 mol%, a titanium content of 12.29 mol%, and an alumina content of 0.046 mass%, was obtained in the same manner as in Example 1, except that the treatment temperature in the HIP treatment was 1450° C. The sintered body of this comparative example had low translucency and was not transparent.

[0146] Comparative Example 5: A sintered body of yttrium- and titania-stabilized zirconia having an yttrium content of 9.0 mol% and a titanium content of 10 mol% was obtained by the same method as in Example 3 of JP 2011-102227 A. That is, commercially available zirconia powder (product name: TZ-10Y, manufactured by Tosoh Corporation) and titania powder (product name: PT-401M, manufactured by Ishihara Sangyo Kaisha) were weighed out so that the yttrium content was 9.0 mol% and the titania content was 10 mol%, and the mixture was mixed in a ball mill using 10 mm diameter zirconia balls as a grinding medium for 72 hours. The dried powder was used as a raw material powder.

[0147] The raw material powder was molded using a die press at a pressure of 50 MPa, and then further consolidated using a cold isostatic press at a pressure of 200 MPa to obtain a cylindrical molded body with a diameter of 20 mm.

[0148] The compact was subjected to primary sintering in an air atmosphere at 1325°C for 2 hours to form a TiO ２ :Y ２ O ３ : ZrO ２ A primary sintered body having a composition of 0.1:0.09:0.81 (molar ratio) was obtained. The obtained primary sintered body had a relative density of 90% or more, an average grain size of 2 μm or less, and a mixed crystalline phase of cubic and tetragonal crystals.

[0149] The obtained primary sintered body was placed in a carbon container with a lid, and the carbon container was placed in a HIP apparatus equipped with a carbon heating element. After that, a HIP-treated body was obtained by HIP-treating in a weakly reducing atmosphere under the following conditions.

[0150] Pressure medium: argon gas (purity: 99.9%) Holding temperature: 1500°C Holding pressure: 150 MPa Holding time: 1 hour After holding, the temperature was lowered to 1000°C at a rate of 80°C / min.

[0151] The HIP-treated body was then heat-treated in an air atmosphere at 1000°C for 2 hours to obtain a sintered body of this comparative example, which was made of titanium and yttrium-doped zirconia with an yttrium content of 9 mol% and a titanium content of 10 mol%. The sintered body of this comparative example was a cubic zirconia sintered body made of cubic crystal grains, and its crystallite diameter was 1409 nm.

[0152] The results of the examples and comparative examples are shown in the table below. The compositions in the table below are calculated as oxides.

[0153]

[0154] All of the sintered bodies of the examples had high transparency with an It of 50% or more, and had strength of 280 MPa or more. Furthermore, the sintered bodies of the examples had a fracture toughness value of 1.5 MPa m ０．５ More than 2.2 MPa m ０．５ From the above, it was confirmed that the sintered bodies had both high transparency and high resistance to the progression of fracture. Furthermore, all of the sintered bodies of the Examples had a peak with a peak top at 2θ = 74.0 ± 0.3 °, and did not have a peak with a peak top at 2θ = 72.8 ± 0.3 ° or a peak with a peak top at 2θ = 74.8 ± 0.3 °. On the other hand, the sintered bodies of Comparative Examples 3 and 4 had translucency but no transparency, and the sintered body of Comparative Example 5 had a fracture toughness value of 1.4 MPa m ０．５ It was confirmed that, despite the high It and three-point bending strength, the resistance to high fracture propagation was about half that of the examples.

[0155] Example 5 A zirconia slurry and a titania slurry were mixed so that the mass ratio of the zirconia powder to the titania powder was 93:7, and a mixed slurry containing alumina and titania, yttrium-stabilized zirconia powder, was obtained, with the yttrium content being 4.75 mol%, the aluminum content being 0.047 mass%, and the titania content being 7 mass% (10.82 mol%). The same method as in Example 1 was used, except that a sintered body of this example was obtained, which consisted of titanium and yttrium-doped zirconia containing alumina, with the yttrium content being 4.75 mol%, the titanium content being 10.82 mol%, and the alumina content being 0.047 mass%. The measured density of the obtained primary sintered body was 5.84 g / cm. ３ The sintered body of this example had an average crystal grain size of 18 μm and a crystallite size of 693 nm.

[0156] Example 6 A zirconia slurry and a titania slurry were mixed so that the mass ratio of the zirconia powder to the titania powder was 94:6, and a mixed slurry containing alumina and titania, yttrium-stabilized zirconia powder, was obtained, with the yttrium content being 4.83 mol%, the aluminum content being 0.047 mass%, and the titania content being 6 mass% (9.33 mol%). The same method as in Example 1 was used, except that a sintered body of this example was obtained, which consisted of titanium and yttrium-doped zirconia containing alumina, with the yttrium content being 4.83 mol%, the titanium content being 9.33 mol%, and the alumina content being 0.047 mass%. The measured density of the obtained primary sintered body was 5.85 g / cm. ３ The sintered body of this example had an average crystal grain size of 15 μm and a crystallite size of 584 nm.

[0157] Example 7: Alumina-containing yttrium-stabilized zirconia powder containing 5.0 mol% yttrium and 0.05 mass% aluminum was mixed with pure water. After mixing, the mixture was wet-pulverized in a ball mill until the average particle size reached 0.5 μm and the standard deviation of the particle size reached 0.1 μm, yielding a zirconia slurry with a powder content (solid concentration) of 45 mass%. A sintered body of this example was obtained using the same method as in Example 1, except that the obtained zirconia slurry was used. The sintered body consisted of titanium and yttrium-doped zirconia containing alumina, with a yttrium content of 4.35 mol%, titanium content of 12.26 mol%, and alumina content of 0.046 mass%. The measured density of the obtained primary sintered body was 5.84 g / cm. ３ The sintered body of this example had a crystallite diameter of 312 nm.

[0158] Example 8: Alumina-containing yttrium-stabilized zirconia powder containing 6.5 mol% yttrium and 0.05 mass% aluminum was mixed with pure water. After mixing, the mixture was wet-pulverized in a ball mill until the average particle size was 0.5 μm and the standard deviation of the particle size was 0.1 μm, yielding a zirconia slurry with a powder content (solid concentration) of 45 mass%. A sintered body of this example was obtained, consisting of titanium and yttrium-doped zirconia containing alumina, with a yttrium content of 5.65 mol%, titanium content of 12.39 mol%, and alumina content of 0.046 mass%, in the same manner as in Example 1, except that the obtained zirconia slurry was used. The measured density of the obtained primary sintered body was 5.84 g / cm. ３ The sintered body of this example had a crystallite diameter of 1039 nm.

[0159] Example 9 A sintered body of this example was obtained, which was made of titanium and yttrium-doped zirconia containing alumina, with an yttrium content of 4.52 mol%, a titanium content of 15.18 mol%, and an alumina content of 0.045 mass%, in the same manner as in Example 1, except that the zirconia slurry and the titania slurry were mixed so that the mass ratio of the zirconia powder to the titania powder was 90:10. The measured density of the obtained primary sintered body was 5.81 g / cm. ３The sintered body of this example had a crystallite diameter of 940 nm.

[0160] Example 10: Yttrium-stabilized zirconia powder with an yttrium content of 5.5 mol% was mixed with pure water. After mixing, the mixture was wet-pulverized in a ball mill until the average particle size was 0.5 μm and the standard deviation of the particle size was 0.1 μm, yielding a zirconia slurry with a powder content (solid content concentration) of 45 mass%. A sintered body of this example, consisting of titanium and yttrium-doped zirconia with an yttrium content of 4.67 mol% and a titanium content of 12.29 mol%, was obtained in the same manner as in Example 1, except that the obtained zirconia slurry was used. The measured density of the obtained primary sintered body was 5.84 g / cm. ３ The sintered body of this example had a crystallite diameter of 781 nm.

[0161] Comparative Example 6 Alumina-containing yttrium-stabilized zirconia powder, which contained 4.0 mol% yttrium and 0.05% by mass of aluminum, was mixed with pure water and wet-pulverized in a ball mill until the average particle size reached 0.5 μm and the standard deviation of the particle size reached 1.0 μm, to obtain a zirconia slurry with a solid content of 45% by mass.

[0162] The obtained zirconia slurry and titania slurry were mixed so that the mass ratio of zirconia powder to titania powder was 92:8, and a mixed slurry containing alumina and titania, yttrium content was 3.40 mol%, aluminum content was 0.046 mass%, and titania content was 8 mass% (0.23 mol%). The same method as in Example 1 was used except that a mixed slurry containing yttrium-stabilized zirconia powder was obtained. The sintered body of this comparative example was made of titanium and yttrium-doped zirconia containing alumina, with a yttrium content of 3.40 mol%, titanium content of 0.23 mol%, and alumina content of 0.046 mass%. The crystallite diameter of the sintered body of this comparative example was 223 nm.

[0163] Comparative Example 7 A zirconia slurry and a titania slurry were mixed so that the mass ratio of the zirconia powder to the titania powder was 87.5:12.5, and a mixed slurry containing yttrium-stabilized zirconia powder containing alumina and titania, in which the yttrium content was 4.33 mol %, the aluminum content was 0.044 mass %, and the titania content was 12.5 mass % (18.71 mol %), was obtained. Primary sintering, HIP treatment, and heat treatment were performed in the same manner as in Example 1, except that the mixed slurry contained yttrium-stabilized zirconia powder containing alumina and titania.

[0164] However, in this comparative example, cracks occurred during the heat treatment after the HIP treatment, and a sintered body could not be obtained.

[0165] The results are shown in the table below. The compositions in the table are oxide equivalents. In addition, in Comparative Example 7, cracks occurred during the heat treatment and a sintered body could not be obtained, so evaluation of Tt and the like was not possible.

[0166]

[0167] It was confirmed that It decreases with decreasing titanium content, while Tt does not show any particular tendency. It was also confirmed that the fracture toughness value tends to improve with decreasing titanium content. Furthermore, it was confirmed from Examples 1 and 10 that the inclusion of alumina increases bending strength, but does not affect fracture toughness value.

[0168] On the other hand, in the comparative example, it was confirmed that when the titanium content exceeded 18.5 mol %, a sintered body could not be obtained.

[0169] Example 11 In the same manner as in Example 1, a granular powder of yttrium-stabilized zirconia containing alumina and titania was obtained, in which the amount of yttrium was 4.67 mol %, the amount of aluminum was 0.046 mass %, and the amount of titania was 8 mass %.

[0170] Alumina powder, iron oxide powder, cobalt oxide powder, 4 mol% yttria-containing zirconia powder, and titania powder were wet mixed in an ethanol solvent in a ball mill using zirconia balls to obtain a mixed powder containing 2 mass% alumina, 0.4 mass% iron oxide, and 0.3 mass% cobalt oxide, with the remainder being 4 mol% yttria and 4.5 wt% titania-containing zirconia. The mixed powder was dried in air at 110°C and then sieved to obtain a black raw powder.

[0171] A 25 mm diameter, unevenly shaped disk-shaped primary mold was filled with yttrium-stabilized zirconia granules and uniaxially pressed at 25 MPa to obtain a 2 mm thick, 25 mm diameter disk-shaped primary molded body made of yttrium-stabilized zirconia granules. The primary molded body was placed in a 50 mm diameter disk-shaped secondary mold with the convex shape facing upward. Black raw material powder was then filled to cover the entire top surface of the primary molded body. This was then uniaxially pressed at 50 MPa to obtain a secondary molded body consisting of a laminate of the primary molded body and a molded body made of the black raw material powder. The resulting secondary molded body was subjected to CIP at 200 MPa. This resulted in a 3.5 mm thick, 50 mm diameter disk-shaped secondary molded body.

[0172] The obtained secondary compact was subjected to primary sintering, HIP treatment, and heat treatment in the same manner as in Example 1, thereby obtaining a composite sintered body of the present embodiment in which the transparent zirconia sintered body and the black zirconia (opaque zirconia) sintered body were sintered together. The It of the black zirconia sintered body was 0.5% or less.

[0173] Example 12 A composite sintered body of the present embodiment in a state in which a sintered body of transparent zirconia and a sintered body of black zirconia (opaque zirconia) were sintered together was obtained in the same manner as in Example 11, except that a granular powder of yttrium-stabilized zirconia containing alumina and titania, in which the yttrium amount was 4.75 mol%, the aluminum amount was 0.047 mass%, and the titania amount was 7 mass% (10.82 mol%), obtained in the same manner as in Example 5, was used.

[0174] The biaxial bending strength of the obtained composite sintered body was measured in accordance with the biaxial bending strength measurement method specified in ISO / DIS 6872. The results are shown in the table below.

[0175]

[0176] The composite sintered body of this example had a biaxial bending strength exceeding 500 MPa in all cases, which confirmed that the sintered body of this embodiment can be used as a member having high mechanical strength.

[0177] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2023-141827, filed on August 31, 2023, are hereby incorporated by reference as the disclosure of the specification of the present disclosure.

Claims

1. A sintered body of zirconia in which titanium and yttrium are dissolved, the yttrium content being 3.5 mol% or more and less than 6.0 mol%, and the titanium content being 6.0 mol% or more and 18.5 mol% or less, and the zirconia is composed of cubic crystal grains including tetragonal domains.

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

3. The sintered body according to claim 1 or 2, wherein the crystallite size calculated from the half-width of the peak having a peak top at 2θ=74.0±0.3° in the XRD pattern is 1,400 nm or less.

4. The sintered body according to any one of claims 1 to 3, having an average crystal grain size of 5 µm or more and 50 µm or less.

5. A sintered body according to any one of claims 1 to 4, having an in-line transmittance of 45% or more at a sample thickness of 1±0.1 mm and a measurement wavelength of 600 nm.

6. Fracture toughness value (K ＩＣ ) is 1.5MPa m ０．５ The sintered body according to claim 1 .

7. The sintered body according to any one of claims 1 to 6, having a three-point bending strength of 280 MPa or more.

8. A method for producing a sintered body according to any one of claims 1 to 7, comprising: a primary sintering step of sintering a molded body, which contains a zirconia source, a yttrium source, and a titanium source, and has an yttrium content of 3.5 mol% or more and less than 6.0 mol%, and a titanium content of 6.0 mol% or more and 18.5 mol% or less, under atmospheric pressure in an oxidizing atmosphere at 1260°C or more to obtain a primary sintered body; a pressure sintering step of pressure sintering the primary sintered body under a reducing atmosphere at 1500°C or more to obtain a pressure-treated body; and a heat treatment step of heat-treating the pressure-treated body in an oxidizing atmosphere.

9. The method according to claim 8, wherein the molded body is a molded body obtained by a molding step of molding a raw material powder obtained by a mixing method of mixing a mixed raw material powder of a zirconia source and an yttrium source with a titanium source.

10. The measured density of the primary sintered body is 5.35 g / cm ３ 6.00g / cm or more ３ The method according to claim 8 or 9, wherein:

11. The method according to any one of claims 8 to 10, wherein the pressure sintering is a hot isostatic pressing process.

12. The method according to any one of claims 8 to 11, wherein the reducing atmosphere is a weakly reducing atmosphere.

13. The method according to any one of claims 8 to 12, wherein the temperature drop rate from the holding temperature to 1000°C in the pressure sintering is 50°C / min or more and 300°C / min or less.

14. A member comprising a sintered body according to any one of claims 1 to 7.

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