Zirconia sintered body and method for producing the same

Abstract

The present invention provides: a zirconia sintered body that has both of high light permeability and high strength enough to be suitably used for a front tooth and a canine tooth (particularly a central incisor and a lateral incisor); and a method for producing the zirconia sintered body. The present invention relates to a zirconia sintered body comprising zirconia and a stabilizing agent capable of inhibiting the occurrence of phase transition of zirconia, in which crystal grains of the zirconia sintered body contain grains each having a grain diameter of 0.45 μm or more and less than 1 μm in a number-based grain diameter distribution at a proportion of 20 to 50%, and the grain diameter is a diameter that passes through the center of gravity of a grain.

Description

[Technical Field]

[0001] The present invention relates to a zirconia sintered body and a method for producing the same. More specifically, the present invention relates to a zirconia sintered body that combines high translucency and high strength and can be suitably used for anterior teeth and canines (particularly central incisors and lateral central incisors), and a method for producing the same. [Background technology]

[0002] Ceramic sintering is generally a mass transfer phenomenon in which the free energy of the system decreases. When ceramic powder is solid-phase sintered, the primary particles contained in the powder undergo grain growth, reducing their surface area and interface over the firing time, depending on their particle size and the firing temperature. It is known that grain growth is more likely to occur when the particle size of the powder is small and the difference between it and the particle size of the target particle is large.

[0003] It is also known that a ceramic sintered body generally tends to have higher strength and toughness as the grain size of the sintered body increases, resulting in a larger grain boundary area. Furthermore, it is also known that a ceramic sintered body tends to have higher translucency as the sintered body contains more particles with a grain size sufficiently larger than the wavelength of visible light, thereby suppressing light scattering by the particles. Therefore, to achieve both strength and translucency in ceramics, it is necessary for the sintered body to contain both small grains and sufficiently large grains.

[0004] As a ceramic, for example, zirconia has high strength and high toughness, so zirconia sintered bodies in which a small amount of yttria (yttrium oxide; Y2O3) is dissolved as a stabilizer (hereinafter, sometimes referred to as "partially stabilized zirconia sintered bodies") are used.

[0005] When a partially stabilized zirconia sintered body is used as a dental material, not only are high strength and high toughness required as mechanical properties, but also optical properties such as translucency and color tone are required from the viewpoint of aesthetics specific to dental applications. To date, studies have been conducted on partially stabilized zirconia sintered bodies that have high strength and toughness and aesthetics aimed at imitating natural teeth.

[0006] Patent Documents 1 and 2 are examples. Patent Document 1 discloses a zirconia sintered body in which the cross-sectional area of ​​each zirconia particle in a cross-sectional photograph of the zirconia sintered body is calculated, and the equivalent particle size of each zirconia particle assuming that each zirconia particle is circular is calculated from the cross-sectional area. The zirconia particle sizes are classified into three classes: less than 0.4 μm, 0.4 μm to less than 0.76 μm, and 0.76 μm or more. The cross-sectional area proportion of zirconia particles with an equivalent particle size of less than 0.4 μm is 4% to 35%, the cross-sectional area proportion of zirconia particles with an equivalent particle size of 0.4 μm to less than 0.76 μm is 24% to 57%, and the cross-sectional area proportion of zirconia particles with an equivalent particle size of 0.76 μm or more is 16% to 62%. Furthermore, the zirconia sintered body is disclosed to have high bending strength and fracture toughness and moderate transparency, and in Example 1, a transmittance of 30% is disclosed.

[0007] Furthermore, Patent Document 2 discloses a translucent zirconia sintered body that contains more than 4.0 mol % and not more than 6.5 mol % yttria and less than 0.1 wt % alumina, has a relative density of 99.82% or more, a total light transmittance at a thickness of 1.0 mm for light with a wavelength of 600 nm of 37% or more and less than 40%, and has a bending strength of 500 MPa or more. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2014 / 142080 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-143178 Summary of the Invention [Problem to be solved by the invention]

[0009] The inventors have confirmed that the zirconia sintered body of Patent Document 1 has a moderate transparency, but the translucency required for anterior teeth and canines (particularly central incisors and lateral central incisors) is gradually increasing, and higher translucency (for example, a transmittance of about 40% or more required for central incisors, etc.) is becoming necessary. Therefore, in order to manufacture dental products for anterior teeth and canines that satisfy such requirements, there is room for further improvement in the translucency of the zirconia sintered body.

[0010] Furthermore, the inventors have confirmed that the zirconia sintered body of Patent Document 2 has low biaxial bending strength, and there is room for further improvement in strength.

[0011] An object of the present invention is to provide a zirconia sintered body that combines high translucency and high strength and that can be suitably used for anterior teeth and canines (particularly central incisors and lateral central incisors), and a method for producing the same. [Means for solving the problem]

[0012] As a result of intensive research to solve the above problems, the present inventors have found that high translucency and high strength can be achieved simultaneously by including 20 to 50% of crystal particles of a zirconia sintered body having a particle size of 0.45 μm or more and less than 1 μm in the particle size distribution on a number basis. Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0013] That is, the present invention includes the following inventions. [1] A zirconia sintered body containing zirconia and a stabilizer capable of suppressing the phase transition of zirconia, The crystal particles of the zirconia sintered body contain particles having a particle diameter of 0.45 μm or more and less than 1 μm in a number-based particle diameter distribution at a rate of 20 to 50%, The zirconia sintered body, wherein the particle diameter is a diameter passing through the center of gravity of the particle. [2] The zirconia sintered body according to [1], wherein the crystal particles of the zirconia sintered body contain particles having a particle size of less than 0.45 μm in a ratio of 20 to 70% in a particle size distribution based on the number of particles. [3] The zirconia sintered body according to [1] or [2], wherein the crystal particles of the zirconia sintered body contain particles having a particle diameter of 1 μm or more in a ratio of 6 to 35% in a particle diameter distribution based on the number of particles. [4] The zirconia sintered body according to any one of [1] to [3], wherein in the crystal system of the zirconia, the proportion of the tetragonal system to the total of the tetragonal system and the cubic system, calculated by the following formula (1), is 0 to 70%. f t / (t+c) =100×I t / (I t +I c ) (1) (In the formula, f t / (t+c) represents the ratio of tetragonal to (tetragonal + cubic) in the zirconia sintered body measured by X-ray diffraction, and I t represents the height of the peak near 2θ = 30.2° (peak based on the tetragonal crystal system), and I c represents the height of the peak near 2θ = 30.1° (peak based on the cubic crystal system). [5] The zirconia sintered body according to [4], wherein the ratio of the tetragonal system to the total of the tetragonal system and the cubic system is 40 to 65%. [6] The zirconia sintered body according to any one of [1] to [5], which has a biaxial bending strength of 550 MPa or more as measured in accordance with JIS T 6526:2012. [7] The zirconia sintered body according to any one of [1] to [6], wherein the stabilizer is yttria. [8] The zirconia sintered body according to [7], wherein the yttria content is 3.0 to 7.5 mol % based on the total moles of zirconia and yttria. [9] A method for producing a zirconia sintered body containing zirconia and a stabilizer capable of suppressing the phase transition of zirconia, A raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia is used, The stabilizer powder includes a powder having at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more in a volume-based particle size distribution. The method for producing a zirconia sintered body according to any one of [1] to [8].

[10] The method for producing a zirconia sintered body according to [9], wherein in the volume-based particle size distribution of the stabilizer powder, the ratio (A):(B) of the frequency of peak tops in the particle size range of 0.05 to 0.40 μm to the frequency (B) of peak tops in the particle size range of 0.5 μm or more is 40:60 to 85:15.

[11] The method for producing a zirconia sintered body according to [9] or

[10] , wherein the stabilizer is yttria.

[12] The method for producing a zirconia sintered body according to

[11] , wherein the yttria content is 3.0 to 7.5 mol % based on the total moles of zirconia and yttria.

[13] The method for producing a zirconia sintered body according to any one of [9] to

[12] , wherein the raw material powder is molded to produce a zirconia molded body.

[14] The method for producing a zirconia sintered body according to

[13] , wherein the zirconia compact is calcined to produce a zirconia calcined body.

[15] The method for producing a zirconia sintered body according to

[13] or

[14] , which comprises firing the zirconia molded body or the zirconia calcined body.

[16] A method for producing a zirconia calcined body containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, comprising: A raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia is used, The stabilizer powder includes a powder having at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more in a volume-based particle size distribution. Method for producing zirconia calcined body.

[17] The method for producing a zirconia calcined body according to

[16] , wherein the raw material powder is molded to produce a zirconia molded body.

[18] The method for producing a calcined zirconia body according to

[17] , further comprising calcining the zirconia compact.

[19] A method for producing a zirconia-containing composition containing zirconia and a stabilizer capable of suppressing the phase transition of zirconia, comprising: The zirconia raw material is pulverized to produce zirconia powder, The raw material of the stabilizer is pulverized to prepare a stabilizer powder; The zirconia powder and the stabilizer powder are mixed to prepare a zirconia composition as a raw material powder, The stabilizer powder includes a powder having at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more in a volume-based particle size distribution. A method for producing a zirconia-containing composition.

[20] The method for producing a zirconia-containing composition according to

[19] , wherein the grinding time of the raw material of the stabilizer is 30 hours or less.

[21] The method for producing a zirconia-containing composition according to

[19] or

[20] , wherein the zirconia raw material is ground for 20 hours or more.

[22] The method for producing a zirconia-containing composition according to any one of

[19] to

[21] , wherein the stabilizer is yttria. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a zirconia sintered body that combines high translucency and high strength and that can be suitably used for anterior teeth and canines (particularly central incisors and lateral central incisors), and a method for producing the same. Furthermore, according to the production method of the present invention, it is possible to provide a zirconia sintered body that combines high translucency and high strength even when fired for a short period of time. [Brief explanation of the drawings]

[0015] [Figure 1]FIG. 1 shows the particle size distribution (volume basis) of the yttria powder used as the raw material powder in Examples 1 to 14. [Figure 2] FIG. 2 shows an image of the zirconia sintered body according to Example 5 observed by an electron microscope. [Figure 3] FIG. 3 shows an image of the zirconia sintered body according to Comparative Example 1 observed by an electron microscope. [Figure 4] FIG. 4 shows an image of the zirconia sintered body according to Comparative Example 4 observed by an electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention provides a zirconia sintered body containing zirconia and a stabilizer capable of suppressing the phase transition of zirconia, wherein the crystal particles of the zirconia sintered body contain particles having a particle diameter of 0.45 μm or more and less than 1 μm in a number-based particle diameter distribution at a ratio of 20 to 50%. The particle diameter refers to the diameter passing through the center of gravity of the particle. The method for measuring the number-based particle diameter distribution is as described in the Examples below. The measurement site is not particularly limited, and may be the surface of the zirconia sintered body or a cross section of the zirconia sintered body.

[0017] In this specification, the upper and lower limits of the numerical ranges (contents of each component, values ​​calculated from each component, and each physical property, etc.) can be combined as appropriate.

[0018] In the present invention, the particle size distribution is calculated by the number standard. For example, in Patent Document 1, particle size distribution is examined by the area standard, in which the total area is calculated and the area percentage is selected, as shown in Table 2. However, according to the study by the present inventors, it has been found that particles with a particle size of 0.45 μm or more and less than 1 μm (hereinafter also referred to as "medium particles"), when examined by the number standard, act to reduce translucency and strength depending on the proportion, due to the influence of the stabilizer. Since Patent Document 1 calculates by area percentage, the area percentage changes significantly even if just one particle with a large particle size is added. In contrast, in the present invention, the particle number percentage is evaluated, so the translucency and strength resulting from the abundance ratio of particles of each size can be more efficiently improved.

[0019] In the zirconia sintered body of the present invention, the crystal grains contain particles having a particle diameter of 0.45 μm or more and less than 1 μm at a ratio of 20 to 50% in the particle diameter distribution on a number basis. By setting the ratio of medium particles to a predetermined ratio in the particle diameter distribution on a number basis, it is possible to further increase the translucency mainly attributable to particles having a particle diameter of 1 μm or more and to increase the strength mainly attributable to particles having a particle diameter of less than 0.45 μm.

[0020] From the viewpoint of the translucency and strength of the zirconia sintered body, the proportion of medium particles is preferably 21% or more, more preferably 22% or more, even more preferably 23% or more, and particularly preferably 24% or more. Furthermore, from the viewpoint of the translucency and strength of the zirconia sintered body, the proportion of medium particles is preferably 49% or less, more preferably 40% or less, even more preferably 36% or less, and particularly preferably 30% or less. The preferred range of the proportion of medium particles can be appropriately combined from the above upper and lower limits, and may be, for example, 21 to 49%, 22 to 40%, or 23 to 36%.

[0021] If the proportion of medium particles in the particle size distribution exceeds 50%, the strength and translucency of the zirconia sintered body will decrease, which is undesirable. Also, if the proportion of medium particles in the particle size distribution is less than 20%, the refractive index difference between particles with a particle size of less than 0.45 μm (hereinafter also referred to as "small particles") and particles with a particle size of 1 μm or more (hereinafter also referred to as "large particles") will be large, which may cause light scattering and significantly reduce the overall translucency, which is undesirable. By having a specified proportion of medium particles, the refractive index difference is buffered and light scattering when light passes from the small particles to the large particles is suppressed.

[0022] In the zirconia sintered body of the present invention, the crystal particles preferably contain particles with a particle size of less than 0.45 μm in a ratio of 20 to 70% in the particle size distribution based on the number of particles. From the viewpoint of further improving the strength of the zirconia sintered body, the ratio of small particles is more preferably 22% or more, even more preferably 30% or more, and particularly preferably 35% or more. From the viewpoint of further improving the strength of the zirconia sintered body, the ratio of small particles is more preferably 69% or less, even more preferably 68.5% or less, and particularly preferably 68% or less.

[0023] In the zirconia sintered body of the present invention, the crystal particles preferably contain particles with a particle size of 1 μm or more at a ratio of 6 to 35% in the particle size distribution based on the number of particles. From the viewpoint of further improving the translucency of the zirconia sintered body, the ratio of large particles is more preferably 6.5% or more, even more preferably 7% or more, and particularly preferably 8% or more. From the viewpoint of further improving the translucency of the zirconia sintered body, the ratio of large particles is more preferably 33% or less, even more preferably 30% or less, and particularly preferably 20% or less.

[0024] Furthermore, in the zirconia sintered body of the present invention, in order to achieve superior translucency and strength, the blending balance of each particle may be adjusted in addition to the proportions of the medium, small, and large particles. In order to achieve superior translucency and strength, the zirconia sintered body of the present invention preferably has the largest proportion of small particles among the three particle types in the particle size distribution (%) based on number, and more preferably the proportion of small particles is 1.5 times or more the proportion of medium particles. In order to achieve superior translucency and strength, the zirconia sintered body of the present invention preferably has the smallest proportion of large particles, and more preferably the proportion of large particles is 0.8 times or less the proportion of medium particles.

[0025] The main crystal system of the zirconia sintered body of the present invention may be either a tetragonal system or a cubic system, but from the viewpoint of the translucency and strength of the zirconia sintered body, it is preferable that the tetragonal system and the cubic system are mixed in a certain ratio. The main crystal system means the crystal system that has the highest proportion compared to the total amount of all crystal systems (monoclinic system, tetragonal system, and cubic system) in the zirconia.

[0026] In the zirconia sintered body, the ratio of tetragonal to (tetragonal + cubic) (hereinafter also referred to as "the ratio of tetragonal to the total of tetragonal and cubic") is preferably less than 80%, and from the viewpoint of superior translucency and strength of the zirconia sintered body, it is more preferably 70% or less, even more preferably 65% ​​or less, and particularly preferably 50% or less. Furthermore, it is preferably 0% or more, and from the viewpoint of superior strength of the zirconia sintered body, it is more preferably 30% or more, and from the viewpoint of superior translucency and strength of the zirconia sintered body, it is more preferably 40% or more, and particularly preferably 41% or more. The preferred range of the ratio of tetragonal to the total of tetragonal and cubic can be appropriately combined from the above upper and lower limits, and may be, for example, 40% or more and 65% or less, or 41% or more and 50% or less.

[0027] In the zirconia sintered body of the present invention, the ratio of the tetragonal system to the total of the tetragonal system and the cubic system in the crystal system of the zirconia is calculated by the following formula (1). f t / (t+c) =100×I t / (I t +I c ) (1) (In the formula, f t / (t+c) represents the ratio of tetragonal to (tetragonal + cubic) in the zirconia sintered body measured by X-ray diffraction, and I t represents the height of the peak near 2θ = 30.2° (peak based on the tetragonal crystal system), and I c represents the height of the peak near 2θ = 30.1° (peak based on the cubic crystal system).

[0028] The proportion of the tetragonal system to the total of the tetragonal system and the cubic system can be calculated by X-ray diffraction (XRD) measurement and using the measurement results, using formula (1).

[0029] The biaxial bending strength of the zirconia sintered body of the present invention is preferably 550 MPa or more, more preferably 600 MPa or more, even more preferably 650 MPa or more, and particularly preferably 700 MPa or more. The biaxial bending strength can be measured in accordance with JIS T 6526:2012. Specifically, it can be measured by the method described in the Examples below.

[0030] The translucency (ΔL * From the viewpoint of producing a prosthesis having a color tone close to that of natural teeth, particularly anterior teeth and canines (e.g., central incisors and lateral central incisors), the value of (WB)) is preferably 13 or more, and from the viewpoint of facilitating the production of a prosthesis having a color tone close to that of anterior teeth in particular, the value of (WB)) is more preferably 14, and even more preferably 15. Translucency (ΔL * (WB)) is the brightness (L) of a white background measured using a spectrophotometer (product name "Crystal Eye") manufactured by Olympus Corporation, with a 7-band LED light source. W *) and the lightness (L) when the chromaticity is measured against a black background using the same sample, the same measuring device, the same measuring mode, and the same light source. B * ) and measure the difference between them (ΔL * =(L W * )-(L B * The measurement conditions, such as the size of the test piece, are as described in the Examples below.

[0031] A stabilizer capable of suppressing the phase transition of zirconia (hereinafter simply referred to as "stabilizer") is preferably one capable of forming partially stabilized zirconia. Examples of such stabilizers include calcium oxide (CaO), magnesium oxide (MgO), yttria (yttrium oxide; Y2O3), cerium oxide (CeO2), scandium oxide (Sc2O3), niobium oxide (Nb2O5), lanthanum oxide (La2O3), erbium oxide (Er2O3), and praseodymium oxide (Pr6O 11 Examples of the stabilizer include oxides such as yttria, ...

[0032] The content of the stabilizer in the zirconia sintered body of the present invention can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, fluorescent X-ray analysis, or the like.

[0033] In the zirconia sintered body of the present invention, the content of the stabilizer is preferably 0.1 to 18 mol %, more preferably 1 to 15 mol %, and even more preferably 1.5 to 10 mol %, based on the total moles of zirconia and stabilizer.

[0034] In the zirconia sintered body of the present invention, when the stabilizer is yttria, the content of yttria, relative to the total moles of zirconia and yttria, is preferably 3.0 mol% or more, more preferably 4.5 mol% or more, from the viewpoint of translucency and strength of the zirconia sintered body, and even more preferably 5.0 mol% or more, from the viewpoint of better translucency and strength of the zirconia sintered body. Furthermore, the yttria content is preferably 7.5 mol% or less, more preferably 7.0 mol% or less, and even more preferably 6.5 mol% or less, based on the total moles of zirconia and yttria, from the viewpoint of the translucency and strength of the zirconia sintered body. The preferred range of the yttria content can be an appropriate combination of the upper and lower limits, and may be, for example, 3.0 mol% or more and 7.5 mol% or less, or 4.5 mol% or more and 6.5 mol% or less. In one embodiment, the yttria content may be 4.0 mol% or more.

[0035] Another embodiment of the present invention is a method for producing a zirconia sintered body, which uses a raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia, and the stabilizer powder contains a powder having, in a volume-based particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more.

[0036] The volumetric particle size distribution can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer manufactured by Horiba, Ltd. (product name "Partica LA-950") by irradiating a slurry diluted with water with ultrasound for 30 minutes, and then measuring the volumetric particle size distribution while applying ultrasound.

[0037] The type and content of the stabilizer capable of suppressing the phase transition of zirconia in the method for producing a zirconia sintered body are the same as those described for the zirconia sintered body.

[0038] Since the desired ratio of medium, large, and small particles can be obtained in the zirconia sintered body after firing, the stabilizer powder contains a powder having a volumetric particle size distribution with at least one peak top in the particle size range of 0.05 to 0.40 μm and at least one peak top in the particle size range of 0.5 μm or more. For example, a particle size distribution such as that shown in the results of the Examples described later (FIG. 1) is preferred. In a preferred embodiment, from the viewpoint of easily obtaining the desired ratio of medium particles, large particles, and small particles in the zirconia sintered body after firing, a method for producing a zirconia sintered body is mentioned, in which a raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia is used, and the stabilizer powder contains a powder having, in a volume-based particle size distribution, one peak top in a particle size range of 0.05 to 0.40 μm and one peak top in a particle size range of 0.5 μm or more.

[0039] In the particle size distribution of the stabilizer powder, the ratio (A):(B) of the frequency of peak tops in the particle size range of 0.05 to 0.40 μm to the frequency of peak tops in the particle size range of 0.5 μm or more is preferably 40:60 to 85:15, more preferably 45:55 to 82:18, and even more preferably 50:50 to 80:20, in order to obtain the desired ratios of medium, large, and small particles. The ratio (A):(B) is calculated using the following two formulas. Ratio (A) = Peak top frequency (A) / (Peak top frequency (A) + Peak top frequency (B)) × 100 Ratio (B) = Peak top frequency (B) / (Peak top frequency (A) + Peak top frequency (B)) × 100 (In the formula, the peak top frequency (A) represents the frequency (%) of the peak top in the particle size range of 0.05 to 0.40 μm, and the peak top frequency (B) represents the frequency (%) of the peak top in the particle size range of 0.5 μm or more.) The frequency of the peak top (A) and the frequency of the peak top (B) can be confirmed as the height of the peak in FIG. 1, for example. In any of the above-described embodiments, the particle size may be in the range of 0.1 to 0.40 μm. For example, another preferred embodiment includes a method for producing a zirconia sintered body, which uses a raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia, and the stabilizer powder contains a powder having, in a volumetric particle size distribution, at least one peak top in a particle size range of 0.1 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more.

[0040] The method for producing the zirconia sintered body preferably includes a step of forming a zirconia molded body by molding a raw material powder. The molding method is not particularly limited, and the zirconia molded body can be formed into a desired shape (block, disk, etc.) using a known method (for example, press molding, etc.).

[0041] From the viewpoint of ease of handling, the zirconia molded body preferably has a biaxial bending strength in the range of 2 to 10 MPa, more preferably in the range of 5 to 8 MPa. The biaxial bending strength of the zirconia molded body can be measured in accordance with JIS T 6526:2012.

[0042] The method for producing the zirconia sintered body preferably includes a step of calcining a zirconia compact to produce a zirconia calcined body.

[0043] In this specification, the term "calcined zirconia body" refers to a semi-sintered body in which zirconia particles (powder) are necked (adhered together) and formed into a block in an incompletely sintered state.

[0044] The density of the zirconia calcined body of the present invention is 2.75 g / cm from the viewpoint of enhancing the translucency and strength of the zirconia sintered body. 3 More than 2.85 g / cm is preferable. 3 More preferably, 2.95 g / cm 3 The above is even more preferable.

[0045] The flexural strength of the zirconia calcined body of the present invention is preferably 15 MPa or more to ensure strength that allows machining, and is preferably 70 MPa or less, more preferably 60 MPa or less, to facilitate machining.

[0046] The bending strength can be measured in accordance with ISO 6872:2015 (Dentistry - Ceramic materials), except for the size of the test specimen, which is 5 mm x 10 mm x 50 mm. The test specimen's face and C-face (the surface where the corners of the test specimen are chamfered at a 45° angle) are sanded longitudinally with 600-grit sandpaper. The test specimen is positioned so that the widest surface faces vertically (the load direction). In the three-point bending test, the span between supports is 30 mm, and the crosshead speed is 0.5 mm / min.

[0047] The zirconia calcined body of the present invention may contain additives other than zirconia and stabilizers, as long as the effects of the present invention are achieved. Examples of such additives include colorants (including pigments, composite pigments, and fluorescent agents), binders, dispersants, antifoaming agents, plasticizers, alumina (Al2O3), titanium oxide (TiO2), and silica (SiO2). One type of additive may be used alone, or two or more types may be used in combination.

[0048] Examples of pigments include oxides of at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb, and Er (specifically, NiO, Cr2O3, etc.). Examples of composite pigments include composite oxides such as (Zr,V)O2, Fe(Fe,Cr)2O4, (Ni,Co,Fe)(Fe,Cr)2O4·ZrSiO4, and (Co,Zn)Al2O4. Examples of fluorescent agents include Y2SiO5:Ce, Y2SiO5:Tb, (Y,Gd,Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, and BaMgAl 10 O 17:Eu, etc.

[0049] Examples of the binder include organic binders, such as acrylic binders, paraffin binders, fatty acid binders, and polyvinyl alcohol binders. Examples of dispersants include ammonium polycarboxylate (e.g., triammonium citrate), ammonium polyacrylate, acrylic copolymer resin, acrylic acid ester copolymer, polyacrylic acid, bentonite, carboxymethyl cellulose, anionic surfactants (e.g., polyoxyethylene alkyl ether phosphate esters such as polyoxyethylene lauryl ether phosphate esters), nonionic surfactants, olein glyceride, amine salt surfactants, oligosaccharide alcohols, and stearic acid. Examples of the antifoaming agent include alcohol, polyether, silicone, and wax. Examples of the plasticizer include polyethylene glycol, glycerin, propylene glycol, and dibutyl phthalate.

[0050] The calcination temperature is preferably, for example, 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher, in order to ensure blocking. Furthermore, the calcination temperature is, for example, preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1100°C or lower, in order to improve dimensional accuracy. A calcination temperature of 800°C to 1200°C is preferred for producing a zirconia calcined body. At such a calcination temperature, it is believed that the stabilizer will not dissolve in solid solution. There are no particular limitations on the calcination temperature, and a known calcination furnace can be used.

[0051] The zirconia calcined body of the present invention can be machined to produce a machined body. The cutting method is not limited to a specific method, and a suitable method can be selected as appropriate depending on the purpose. For example, if the zirconia calcined body is in the shape of a disk, the disk can be machined using a CAD / CAM system to produce a machined body into the shape of a dental product (e.g., a crown-shaped prosthesis). Examples of dental products include copings, frameworks, crowns, crown bridges, abutments, implants, implant screws, implant fixtures, implant bridges, implant bars, brackets, denture bases, inlays, onlays, orthodontic wires, and laminate veneers.

[0052] The method for producing the zirconia sintered body preferably includes a step of firing a zirconia molded body or a zirconia calcined body. The zirconia sintered body can be produced by firing the zirconia molded body or the zirconia calcined body at a temperature at which the zirconia particles are sintered (sintering step).

[0053] The firing temperature (maximum firing temperature) can be appropriately changed depending on the components of the zirconia molded body or the zirconia calcined body, and is not particularly limited, but is preferably 1350°C or higher, more preferably 1450°C or higher, and even more preferably 1500°C or higher. The upper limit of the firing temperature is not particularly limited, but is, for example, preferably 1700°C or lower, more preferably 1650°C or lower, and even more preferably 1600°C or lower. There are no particular limitations on the firing, and any known firing furnace can be used.

[0054] In the sintering step, the holding time at the sinterable temperature (maximum firing temperature) is preferably 120 minutes or less, more preferably 90 minutes or less, even more preferably 75 minutes or less, even more preferably 60 minutes or less, particularly preferably 45 minutes or less, and most preferably 30 minutes or less. Furthermore, for shorter firing times, the holding time can be 25 minutes or less, 20 minutes or less, or 15 minutes or less. Furthermore, the holding time is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. According to the present invention, even with such a short firing time, it is possible to suppress a decrease in the translucency of the produced zirconia sintered body and maintain high strength. Furthermore, shortening the firing time can improve production efficiency and reduce energy costs.

[0055] The temperature increase rate and temperature decrease rate in the sintering step are preferably set so as to shorten the time required for the sintering step, but are not particularly limited.

[0056] Another embodiment of the present invention is a method for producing a calcined zirconia body containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, the method using a raw material powder containing zirconia powder and a stabilizer powder capable of suppressing a phase transition of zirconia, the stabilizer powder containing a powder having, in a volumetric particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more.

[0057] The type and content of the stabilizer capable of suppressing the phase transition of zirconia in the method for producing a calcined zirconia body are the same as those described for the zirconia sintered body. The peak tops of the stabilizer powder and the ratio (A):(B) of the frequency (A) of the peak tops in the particle size range of 0.05 to 0.40 μm and the frequency (B) of the peak tops in the particle size range of 0.5 μm or more are the same as those in the method for producing a zirconia sintered body.

[0058] The method for producing the calcined zirconia body preferably includes a step of forming a zirconia compact by molding the raw material powder. The molding method is not particularly limited, and the zirconia compact can be formed into a desired shape (block, disk, etc.) using a known method (e.g., press molding, etc.).

[0059] The method for producing the zirconia calcined body preferably includes a step of calcining a zirconia compact to produce the zirconia calcined body.

[0060] The calcination temperature and the firing furnace for the calcination in the method for producing a zirconia calcined body are the same as those in the method for producing a zirconia sintered body.

[0061] Furthermore, another embodiment of the present invention is a method for producing a zirconia-containing composition containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, the method including pulverizing a raw material for the zirconia to produce a zirconia powder, pulverizing a raw material for the stabilizer to produce a stabilizer powder, and mixing the zirconia powder and the stabilizer powder to produce a zirconia composition as a raw material powder, wherein the stabilizer powder contains a powder having, in a volume-based particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more.

[0062] The type and content of the stabilizer capable of suppressing the phase transition of zirconia in the method for producing the zirconia-containing composition are the same as those described for the zirconia sintered body.

[0063] An example in which the stabilizer is yttria will be described below.

[0064] The yttria raw material is pulverized by a known method (for example, a ball mill), and the pulverization time of the yttria raw material is preferably 30 hours or less, more preferably 20 hours or less, even more preferably 15 hours or less, and particularly preferably 10 hours or less. The yttria raw material is preferably ground for 1 hour or more, more preferably 2 hours or more, and even more preferably 5 hours or more. By such a grinding process, the stabilizer powder obtained contains a powder having at least one peak top in the particle size range of 0.05 to 0.40 μm and at least one peak top in the particle size range of 0.5 μm or more in a volumetric particle size distribution. The grinding time can be adjusted appropriately so as to obtain yttria powder having the desired peak top. By including the stabilizer powder in the zirconia-containing composition, the desired ratio of medium particles, large particles, and small particles can be obtained in the zirconia sintered body after firing.

[0065] In addition to the yttria raw material, a zirconia raw material is pulverized to prepare zirconia powder. The reason for separately grinding the yttria raw material and the zirconia raw material is that, in order to obtain yttria powder having a desired peak top from the yttria raw material, it is preferable to use raw material particles of different sizes for the yttria raw material and zirconia raw material, and to distinguish between the grinding conditions, such as by dividing the grinding time.

[0066] The average particle size (average primary particle size) of the yttria raw material for obtaining yttria powder with the desired particle size distribution after milling is preferably 1.0 μm or more, more preferably 2.0 μm or more, because the use of a raw material powder containing a mixture of yttria powder and zirconia powder results in the desired ratio of medium, large, and small particles in the zirconia sintered body after sintering. Furthermore, the average particle size of the yttria raw material is preferably less than 10 μm, more preferably 8 μm or less, because the use of a raw material powder containing a mixture of yttria powder and zirconia powder results in the desired ratio of medium, large, and small particles in the zirconia sintered body after sintering. The average particle size can be measured by volume using, for example, a laser diffraction / scattering particle size distribution analyzer (product name "Partica LA-950") manufactured by Horiba, Ltd., by irradiating a water-diluted slurry with ultrasonic waves for 30 minutes and then applying ultrasonic waves.

[0067] Furthermore, the average particle size (average primary particle size) of the zirconia raw material used to obtain zirconia powder after milling is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, because the desired ratio of medium, large, and small particles can be obtained in the zirconia sintered body after sintering by using a raw material powder that is a mixture of yttria powder and zirconia powder. Furthermore, the average particle size of the zirconia raw material is preferably less than 1 μm, more preferably 0.6 μm or less, and even more preferably 0.4 μm or less. The average particle size of the zirconia raw material can be measured in the same manner as the average particle size of the yttria raw material.

[0068] The zirconia raw material preferably contains a monoclinic system, since it maintains strength and has excellent translucency even when fired for a short time. mis preferably 60% or more of the total amount of monoclinic, tetragonal, and cubic crystals, and from the viewpoint of superior light transmittance even when fired for a short time, is more preferably 70% or more, even more preferably 80% or more, still more preferably 90% or more, and particularly preferably 95% or more.

[0069] Monoclinic fraction f m is calculated using the following formula (2): f m = I m / (I m +I t +I c )×100 (2) (In the formula, f m represents the percentage of monoclinic crystals in the zirconia raw material, and in XRD measurement, I m represents the monoclinic peak intensity around 2θ = 28°, and I t represents the peak intensity of the tetragonal system around 2θ = 30.2°, and I c represents the peak intensity of the cubic crystal system around 2θ=30.1°.)

[0070] Monoclinic fraction of zirconia raw material f m By setting the above ratio, the obtained zirconia molded body and zirconia calcined body also have the same monoclinic ratio f m is obtained.

[0071] The zirconia-containing composition of the present invention may contain additives other than zirconia and stabilizers, as long as the effects of the present invention are achieved. Examples of such additives include colorants (including pigments, composite pigments, and fluorescent agents), binders, dispersants, antifoaming agents, alumina (Al2O3), titanium oxide (TiO2), and silica (SiO2). One type of additive may be used alone, or two or more types may be used in combination.

[0072] The zirconia-containing composition of the present invention may be in a dry state, or may contain or be contained in a liquid. For example, the zirconia-containing composition may be in the form of a powder, paste, slurry, or the like.

[0073] The present invention includes embodiments in which the above-described configurations are combined in various ways within the scope of the technical concept of the present invention, as long as the effects of the present invention are achieved. [Example]

[0074] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way, and many modifications within the technical scope of the present invention are possible by those skilled in the art.

[0075] [Raw materials] The following raw materials 1, 2, and 3 were used as the raw material for zirconia and the raw material for yttria. As raw material 1, zirconia powder was used, which was 99% or more of a monoclinic system, had an average primary particle size of 100 nm, and secondary particles with an average particle size of 11 μm. As raw material 2, yttria powder with an average particle size of approximately 3200 nm was used. As raw material 3, zirconia powder "Zpex Smile (registered trademark)" manufactured by Tosoh Corporation was used.

[0076] [Examples 1 to 14] <Preparation of zirconia slurry> A zirconia raw material (raw material 1) was added to water. This and zirconia beads were placed in a rotating container, and the raw material was pulverized (disintegrated) by ball milling until the particles contained in the slurry had the desired average particle size (approximately 100 nm). The particle size was measured by volume using a laser diffraction / scattering particle size distribution analyzer (product name "Partica LA-950") manufactured by Horiba, Ltd., after irradiating the water-diluted slurry with ultrasonic waves for 30 minutes. The desired zirconia slurry was obtained after approximately 20 hours of ball milling.

[0077] <Preparation of yttria slurry> Next, the yttria raw material (raw material 2) was added to water. This raw material and zirconia beads were placed in a rotating container and milled in a ball mill until the particles contained in the slurry had the desired particle size (peak top frequency (A) in the range of 0.05 to 0.40 μm and peak top frequency (B) in the range of 0.50 μm or more, with a ratio (A):(B) of 50:50 to 79:21). The particle size was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (product name "Partica LA-950") manufactured by Horiba, Ltd., after irradiating the water-diluted slurry with ultrasonic waves for 30 minutes. The desired yttria slurry was obtained after approximately 6 to 20 hours of ball milling.

[0078] Next, the resulting zirconia slurry and the resulting yttria slurry were mixed, an organic binder was added, and the mixture was stirred with a rotor blade. The stirred slurry was dried and granulated using a spray dryer to obtain a powder. The average particle size of the powder was 40 μm. This powder was poured into a cylindrical mold and uniaxially pressed at a pressure of 33 MPa, followed by a CIP process at 170 MPa to obtain a green body. The green body was placed in an electric furnace, heated from room temperature at a rate of 10°C / min, and then held at 500°C for 2 hours to degrease the organic components. The green body was then held at 1000°C for 2 hours and slowly cooled at a rate of -0.4°C / min to obtain a zirconia calcined body. The resulting zirconia calcined body was heated at a rate of 10°C / min to the firing temperature (maximum firing temperature) listed in Table 1 and held for the time listed in Table 1 to obtain a zirconia sintered body.

[0079] [Comparative Examples 1 to 3] A zirconia raw material (raw material 1) and an yttria raw material (raw material 2) were added to water. These and zirconia beads were placed in a rotating container and pulverized in a ball mill. The ball milling time was adjusted to produce a large-particle powder with a large average particle size (average particle size 0.4 μm) and a small-particle powder with a small average particle size (0.08 μm). The particle size was measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer (product name "Partica LA-950") manufactured by Horiba, Ltd., by irradiating the slurry diluted with water with ultrasound for 30 minutes and then applying ultrasound.

[0080] Next, the large particle size powder and the small particle size powder were mixed. The mixing ratio of the large particle size powder to the small particle size powder was 1:2 to 2:1. Titanium oxide, aluminum oxide, and an organic binder were added to the resulting slurry and stirred with a rotor blade. The stirred slurry was dried and granulated using a spray dryer to obtain a powder. The average particle size of the powder was 40 μm. This powder was poured into a cylindrical mold and uniaxially pressed at a pressure of 33 MPa, followed by CIP treatment at 170 MPa to obtain a green body. The green body was placed in an electric furnace, heated from room temperature at a rate of 10°C / min, and held at 500°C for 2 hours to degrease the organic components. It was then held at 1000°C for 2 hours and slowly cooled at a rate of -0.4°C / min to obtain a zirconia calcined body. The resulting zirconia calcined body was heated at a rate of 10°C / min to the firing temperature (maximum firing temperature) listed in Table 1 and held for the time listed in Table 1 to obtain a zirconia sintered body.

[0081] Comparative Example 4 Zirconia powder "Zpex Smile (registered trademark)" (raw material 3) manufactured by Tosoh Corporation was poured into a cylindrical mold and uniaxially pressed at a pressure of 33 MPa, followed by further CIP treatment at 170 MPa to obtain a compact. The compact was placed in an electric furnace, heated from room temperature at a rate of 10°C / min, and held at 500°C for 2 hours to degrease organic components. The compact was then held at 1000°C for 2 hours and slowly cooled at -0.4°C / min to obtain a zirconia calcined body. The obtained zirconia calcined body was heated at a rate of 10°C / min to the firing temperature (maximum firing temperature) listed in Table 1 and held for the time listed in Table 1 to obtain a zirconia sintered body.

[0082] The properties of the zirconia sintered bodies produced in each of the Examples and Comparative Examples were measured by the following methods.

[0083] <Method for measuring particle size number ratio> For the sintered bodies obtained in each of the Examples and Comparative Examples, images (SEM images) of the surfaces were obtained using a scanning electron microscope (product name "VE-9800", manufactured by Keyence Corporation). The grain boundaries of each crystal grain were noted on the obtained image, and the crystal grain size was then calculated by image analysis. To measure particle size, image analysis software (product name "Image-Pro Plus ver. 7.0.1", manufactured by Hakuto Co., Ltd.) was used to binarize the captured SEM image, adjust the brightness range so that the grain boundaries were clearly visible, and recognize the particles from the field of view (area). The particle diameter obtained with Image-Pro Plus is the diameter passing through the center of gravity of the particle, and is calculated by measuring the length of the line segment connecting the outlines passing through the center of gravity, determined from the outline of the particle, at 2-degree intervals around the center of gravity, and averaging the measured values ​​(180 particles). Particles that do not overlap the edges of the image were measured. "Particles that do not overlap the edges of the image" refers to particles excluding those whose outlines do not fit completely within the screen of the SEM photograph (particles whose outlines end at the top, bottom, left, and right boundary lines). The grain size of all grains not bordering the image edge was selected in Image-Pro Plus with the option to exclude all border grains. For one sample of each example and comparative example, the particle diameter of each particle in three visual fields was obtained. Fig. 2 shows an SEM image of the zirconia sintered body of Example 5. Fig. 3 shows an SEM image of the zirconia sintered body of Comparative Example 1, and Fig. 4 shows an SEM image of the zirconia sintered body of Comparative Example 4.

[0084] The particle size data of each particle obtained for each example and comparative example was classified into three classes: less than 0.45 μm, 0.45 μm or more but less than 1.0 μm, and 1.0 μm or more. When the total number of data for each class was set as 100%, the proportion of the number of data for each particle size range was calculated.

[0085] <Method for measuring the light transmittance of sintered bodies> The obtained zirconia sintered body was polished into a flat plate sample with a thickness of 1.20 mm. The chromaticity of the sample was measured using a spectrophotometer (product name "Crystal Eye") manufactured by Olympus Corporation in a measurement mode with a 7-band LED light source against a white background. W * ) and the lightness (L) when the chromaticity is measured on a black background using the same sample, the same measuring device, the same measuring mode, and the same light source. B* ) and measure the difference between them (ΔL * =(L W * )-(L B * )) to translucency (ΔL * (WB)) (n=3).

[0086] The average values ​​of the measurements are shown in Table 1. Translucency ΔL * (WB) was evaluated as "Good" if it was 15 or more, "Good" if it was 13 or more but less than 15, and "Poor" if it was less than 13. From the viewpoint of producing prostheses with a color tone close to that of natural teeth (especially anterior teeth and canines), ΔL * (WB) is preferably 13 or more, more preferably 14 or more, and even more preferably 15 or more.

[0087] <Method for measuring biaxial bending strength of sintered body> The resulting zirconia sintered body was cut into a sample with a diameter of 15 mm and a thickness of 1.2 mm. The biaxial bending strength of the resulting sintered body sample was measured (n=5) at a crosshead speed of 1.0 mm / min using a Shimadzu Corporation universal precision testing machine Autograph (product name "AG-I 100kN") in accordance with JIS T 6526:2012. The biaxial bending strength was evaluated as "good" for a value of 550 MPa or more and "bad" for a value of less than 550 MPa.

[0088] <Method for measuring the tetragonal / cubic crystal system ratio> The surface of the zirconia sintered body was mirror-finished, and X-ray diffraction (XRD) measurement was performed, and the refractive index was calculated using the following formula. f t / (t+c) =100×I t / (I t +I c ) (1) where f t / (t+c) represents the ratio of tetragonal to (tetragonal + cubic) in the zirconia sintered body, and I t represents the height of the peak near 2θ = 30.2° (peak based on the tetragonal crystal system), and I crepresents the height of the peak near 2θ=30.1° (peak based on the cubic crystal system).

[0089] [Table 1]

[0090] From the above results, it was confirmed that the zirconia sintered body of the present invention can achieve both high translucency and high strength, making it suitable for use in anterior teeth and canines (particularly central incisors and lateral central incisors). Furthermore, despite being fired for a short time, it exhibited excellent translucency and higher strength than normal firing (firing at the maximum firing temperature for 120 minutes), confirming that it achieved both high translucency and strength even in a short firing time.

[0091] In contrast, in Comparative Examples 1 to 3, the proportion of medium particles as in the Examples was not obtained. Therefore, in Comparative Examples 1 to 3, the proportion of medium particles as in the Examples was not obtained, and high translucency was not obtained. Furthermore, in Comparative Example 4 corresponding to Patent Document 2, the yttria raw material was not separated as a raw material, so yttria was dissolved in zirconia, and the proportion of medium particles as in the Examples was not obtained, and high strength was not obtained.

[0092] As shown in Table 2 below, the above Comparative Examples 1 to 3 correspond to Examples 24, 26, and 1 of Patent Document 1 (WO 2014 / 142080), respectively.

[0093] [Table 2] [Industrial Applicability]

[0094] The zirconia sintered body of the present invention can be suitably used for dental purposes. In particular, the zirconia sintered body of the present invention is useful as a dental prosthesis for anterior teeth and canines (particularly central incisors and lateral central incisors).

Claims

1. A zirconia sintered body containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, The crystal particles of the zirconia sintered body contain particles having a particle diameter of 0.45 μm or more and less than 1 μm in a number-based particle diameter distribution at a rate of 20 to 50%, Contains particles with a particle size of less than 0.45 μm at a ratio of 20 to 70%; Contains particles with a particle diameter of 1 μm or more at a ratio of 6 to 35%. The zirconia sintered body, wherein the particle diameter is a diameter passing through the center of gravity of the particle.

2. The zirconia sintered body according to claim 1, wherein the crystal grains of the zirconia sintered body contain particles having a particle diameter of less than 0.45 μm in a number-based particle diameter distribution at a ratio of 22.7 to 67.1%.

3. The zirconia sintered body according to claim 1, wherein the crystal grains of the zirconia sintered body contain particles having a particle diameter of 1 μm or more in a number-based particle diameter distribution at a ratio of 7.9 to 31.7%.

4. 2. The zirconia sintered body according to claim 1, wherein, in the zirconia crystal system, the ratio of the tetragonal system to the total of the tetragonal system and the cubic system, calculated by the following formula (1), is 0 to 70%. f t / (t+c) =100×I t / (I t +I c ) (1) (In the formula, f t / (t+c) represents the ratio of tetragonal to (tetragonal + cubic) in the zirconia sintered body measured by X-ray diffraction, and I t represents the height of the peak near 2θ = 30.2° (peak based on the tetragonal system), and I c represents the height of the peak near 2θ = 30.1° (peak based on the cubic crystal system).

5. The zirconia sintered body according to claim 4, wherein the ratio of the tetragonal system to the total of the tetragonal system and the cubic system is 40 to 65%.

6. The zirconia sintered body according to claim 1, having a biaxial bending strength measured in accordance with JIS T 6526: 2012 of 550 MPa or more.

7. The zirconia sintered body according to claim 1 , wherein the stabilizer is yttria.

8. The zirconia sintered body according to claim 7, wherein the content of yttria is 3.0 to 7.5 mol% with respect to the total moles of zirconia and yttria.

9. A method for producing a zirconia sintered body containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, A raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia is used, The average particle size of the zirconia raw material powder for obtaining the zirconia powder is 0.01 μm or more and less than 1 μm, The zirconia powder has a monoclinic fraction f m calculated by the following formula (2) of 60% or more, f m = I m / (I m + I t + I c ) × 100 (2) (In the formula, f m represents the proportion (%) of monoclinic crystals in the raw zirconia material, and in XRD measurement, I m represents the monoclinic crystal peak intensity around 2θ=28°, I t represents the tetragonal crystal peak intensity around 2θ=30.2°, and I c represents the cubic crystal peak intensity around 2θ=30.1°.) the stabilizer powder comprises a powder having, in a volume-based particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more; In the volume-based particle size distribution of the stabilizer powder, the ratio (A):(B) of the frequency of peak tops in a particle size range of 0.05 to 0.40 μm to the frequency (B) of peak tops in a particle size range of 0.5 μm or more is 45:55 to 82:18, The ratio (A):(B) is expressed by the following two formulas: Ratio (A) = Peak top frequency (A) / (Peak top frequency (A) + Peak top frequency (B)) × 100 Ratio (B) = Peak top frequency (B) / (Peak top frequency (A) + Peak top frequency (B)) × 100 (In the formula, the peak top frequency (A) represents the frequency (%) of the peak top in the particle size range of 0.05 to 0.40 μm, and the peak top frequency (B) represents the frequency (%) of the peak top in the particle size range of 0.5 μm or more.) The method for producing a zirconia sintered body according to any one of claims 1 to 8, calculated from the above formula.

10. 10. The method for producing a zirconia sintered body according to claim 9, wherein the ratio (A):(B) of the frequency of the peak top in the particle diameter range of 0.05 to 0.40 μm in the volume-based particle diameter distribution of the stabilizer powder to the frequency of the peak top in the particle diameter range of 0.5 μm or more is 50:50 to 80:

20.

11. The method for producing a zirconia sintered body according to claim 9, wherein the stabilizer is yttria.

12. The method for producing a zirconia sintered body according to claim 11, wherein the content of yttria is 3.0 to 7.5 mol% with respect to the total moles of zirconia and yttria.

13. The method for producing a zirconia sintered body according to claim 9, wherein the raw material powder is molded to produce a zirconia molded body.

14. The method for producing a zirconia sintered body according to claim 13, wherein the zirconia compact is calcined to produce a zirconia calcined body.

15. A method for producing a zirconia sintered body as described in claim 13, further comprising sintering the produced zirconia molded body.

16. A method for producing a zirconia calcined body containing zirconia and a stabilizer capable of suppressing a phase transition of zirconia, comprising: A raw material powder containing zirconia powder and a stabilizer powder capable of suppressing the phase transition of zirconia is used, The average particle size of the zirconia raw material powder for obtaining the zirconia powder is 0.01 μm or more and less than 1 μm, The zirconia powder has a monoclinic fraction f m calculated by the following formula (2) of 60% or more, f m = I m / (I m + I t + I c ) × 100 (2) (In the formula, f m represents the proportion (%) of monoclinic crystals in the raw zirconia material, and in XRD measurement, I m represents the monoclinic crystal peak intensity around 2θ=28°, I t represents the tetragonal crystal peak intensity around 2θ=30.2°, and I c represents the cubic crystal peak intensity around 2θ=30.1°.) the stabilizer powder comprises a powder having, in a volume-based particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more; In the volume-based particle size distribution of the stabilizer powder, the ratio (A):(B) of the frequency of peak tops in a particle size range of 0.05 to 0.40 μm to the frequency (B) of peak tops in a particle size range of 0.5 μm or more is 45:55 to 82:18, The ratio (A):(B) is expressed by the following two formulas: Ratio (A) = Peak top frequency (A) / (Peak top frequency (A) + Peak top frequency (B)) × 100 Ratio (B) = Peak top frequency (B) / (Peak top frequency (A) + Peak top frequency (B)) × 100 (In the formula, the peak top frequency (A) represents the frequency (%) of the peak top in the particle size range of 0.05 to 0.40 μm, and the peak top frequency (B) represents the frequency (%) of the peak top in the particle size range of 0.5 μm or more.) A method for producing a zirconia calcined body, wherein the calcined zirconia body is calculated from the above formula.

17. The method for producing a zirconia calcined body according to claim 16, wherein the raw material powder is molded to produce a zirconia molded body.

18. The method for producing a zirconia calcined body according to claim 17, further comprising calcining the zirconia compact.

19. A method for producing a zirconia-containing composition comprising zirconia and a stabilizer capable of suppressing a phase transition of zirconia, the method comprising: The zirconia raw material is pulverized to produce zirconia powder, The raw material of the stabilizer is pulverized to prepare a stabilizer powder; The zirconia powder and the stabilizer powder are mixed to prepare a zirconia composition as a raw material powder, The average particle size of the zirconia raw material powder for obtaining the zirconia powder is 0.01 μm or more and less than 1 μm, The zirconia powder has a monoclinic fraction f m calculated by the following formula (2) of 60% or more, f m = I m / (I m + I t + I c ) × 100 (2) (In the formula, f m represents the proportion (%) of monoclinic crystals in the raw zirconia material, and in XRD measurement, I m represents the monoclinic crystal peak intensity around 2θ=28°, I t represents the tetragonal crystal peak intensity around 2θ=30.2°, and I c represents the cubic crystal peak intensity around 2θ=30.1°.) the stabilizer powder comprises a powder having, in a volume-based particle size distribution, at least one peak top in a particle size range of 0.05 to 0.40 μm and at least one peak top in a particle size range of 0.5 μm or more; In the volume-based particle size distribution of the stabilizer powder, the ratio (A):(B) of the frequency of peak tops in a particle size range of 0.05 to 0.40 μm to the frequency (B) of peak tops in a particle size range of 0.5 μm or more is 45:55 to 82:18, The ratio (A):(B) is expressed by the following two formulas: Ratio (A) = Peak top frequency (A) / (Peak top frequency (A) + Peak top frequency (B)) × 100 Ratio (B) = Peak top frequency (B) / (Peak top frequency (A) + Peak top frequency (B)) × 100 (In the formula, the peak top frequency (A) represents the frequency (%) of the peak top in the particle size range of 0.05 to 0.40 μm, and the peak top frequency (B) represents the frequency (%) of the peak top in the particle size range of 0.5 μm or more.) A method for producing a zirconia-containing composition, wherein the zirconia-containing composition is calculated from the above formula.

20. The method for producing a zirconia-containing composition according to claim 19, wherein the raw material of the stabilizer is milled for 30 hours or less.

21. The method for producing a zirconia-containing composition according to claim 19 or 20, wherein the zirconia raw material is milled for 20 hours or more.

22. 21. The method for producing a zirconia-containing composition according to claim 19 or 20, wherein the stabilizer is yttria.

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