Zirconia powder

Abstract

Provided are at least one among: zirconia powder with which it is possible to produce, by means of an industrial production method, a zirconia sintered body having translucency and transparency suitable for a dental prosthetic material for an anterior tooth incisal edge; a method for producing the zirconia powder; and a use thereof.　The zirconia powder is characterized by containing a stabilizing element, wherein the content of the stabilizing element in terms of oxide is 5.6 mol% to 7.0 mol% (exclusive of 7.0 mol%), the BET specific surface area is 9.0 m2 / g to 16.0 m2 / g, the crystal phase includes a monoclinic phase, and the monoclinic phase content is 2.5% to 20.0%.

Description

Zirconia powder

[0001] This disclosure relates to zirconia powder.

[0002] Because they possess aesthetics close to those of natural teeth, zirconia sintered bodies are used as various dental prosthetic materials such as inlays, onlays, crowns, and bridges. When used as dental prosthetic materials, zirconia sintered bodies and their precursors are selected according to their intended use, such as for molars or incisors. In recent years, with the further expansion of applications, the required characteristics of zirconia sintered bodies have become more subdivided. One of these subdivided required characteristics is for "anterior tooth incisal applications." For this application, zirconia sintered bodies with high translucency as well as appropriate transparency are required (for example, Patent Documents 1 and 2).

[0003] Incidentally, dental prosthetic materials made from zirconia sintered bodies are usually manufactured by first forming a molded body (compacted powder) from powder, then calcining it to produce a calcined body (semi-sintered body, pre-sintered body), and finally processing and sintering it. Conventionally, atmospheric pressure sintering in an air atmosphere, where the material is held at the holding temperature for one hour or more, has been applied. However, in recent years, in order to meet the demands of chairside treatment, research has been conducted on the production of zirconia sintered bodies for dental prosthetic materials and suitable precursors by applying a sintering method (so-called high-speed sintering) that completes sintering in several tens of minutes to several hours, or even less than one hour (for example, Patent Documents 3 and 4).

[0004] U.S. Patent Publication 2020 / 0062653, U.S. Patent Publication 2022 / 0153649, U.S. Patent Publication 2021 / 0101838, U.S. Patent Publication 2024 / 0376012

[0005] While high-speed sintering is being investigated, atmospheric pressure sintering in an air atmosphere, where the material is held at the holding temperature for more than one hour (hereinafter also referred to as "standard sintering"), remains the dominant sintering method for the production of zirconia sintered bodies for dental prosthetics. Furthermore, in the industrial production of zirconia sintered bodies for dental prosthetics, standard sintering with a rapid heating rate (e.g., 5°C / min or more) (hereinafter also referred to as "industrial sintering") is used, taking productivity into consideration. Moreover, calcined zirconia bodies used in industrial sintering are mainly produced by calcining molded bodies obtained by dry molding (specifically, press molding, and, if necessary, cold isostatic pressing (hereinafter also referred to as "CIP")) of zirconia powder. Therefore, there remains a high demand for precursors that can be used in the production of zirconia sintered bodies for dental prosthetics by industrial sintering, using calcined bodies obtained by industrial manufacturing methods, i.e., dry molding and calcining of zirconia powder.

[0006] On the other hand, Patent Document 1 describes how a zirconia sintered body with high translucency was produced by wet molding (casting) in which a slurry is injected and solidified, followed by calcination and sintering of the molded body. However, when the powder from Patent Document 1 was dry-molded, the moldability was poor, and it was difficult to obtain a zirconia sintered body with translucency and transparency suitable as a dental prosthesis for the incisal edges of anterior teeth.

[0007] Furthermore, Patent Document 2 discloses that a zirconia sintered body for dental prostheses is manufactured by press molding, calcining, and sintering a powder obtained by drying a non-aqueous solvent slurry, which is a non-aqueous solvent slurry obtained by substituting and concentrating an aqueous solvent slurry with a non-aqueous solvent. However, non-aqueous solvent slurry requires not only a large amount of non-aqueous solvent but also multiple solvent concentrations. As a result, the manufacturing cost is significantly higher compared to the use of aqueous solvent slurry, making non-aqueous solvent slurry unsuitable for industrial production. In addition, the powder in Patent Document 2 consists of fine powder particles, and when dried without substitution with a non-aqueous solvent, significant powder aggregation occurs, making it impossible to obtain a zirconia sintered body with the translucency and transparency suitable for use as a dental prosthesis for the incisal edges of anterior teeth.

[0008] This disclosure aims to provide a zirconia powder that can be manufactured by an industrial method to produce a translucent and transparent zirconia sintered body suitable for dental prosthetic materials for the incisal edges of anterior teeth, a method for manufacturing the same, and at least one of the applications thereof.

[0009] This disclosure describes an industrial manufacturing method for a zirconia sintered body (hereinafter also referred to as "instrumental sintered body") having translucency and transparency suitable for dental prosthetic materials for the incisal edges of anterior teeth, as well as the zirconia powder used for this purpose. As a result, it was confirmed that even when conventional zirconia powder is prepared by known methods, an incisal sintered body cannot be obtained through industrial manufacturing. Further investigation revealed that by using zirconia powder composed of powder particles with a controlled crystalline phase as a precursor, an incisal sintered body can be obtained even when manufacturing a zirconia sintered body for dental prosthetic materials using dry molding and industrial sintering.

[0010] In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows: [1] Contains a stabilizing element, the content of the stabilizing element in terms of oxide is 5.6 mol% or more and less than 7.0 mol%, and the BET specific surface area is 9.0 m ２ / g or more 16.0m ２[1] Zirconia powder characterized by having a concentration of 2.5% or less per gram, containing monoclinic crystals in its crystalline phase, and having a monoclinic phase ratio of 2.5% or more and 20.0% or less. [2] The zirconia powder according to [1], wherein the stabilizing element is one or more selected from the group consisting of yttrium (Y), calcium (Ca), magnesium (Mg), niobium (Nb), europium (Eu), gadolinium (Gd), ytterbium (Yb), praseodymium (Pr), lanthanum (La), scandium (Sc), erbium (Er), and terbium (Tb). [3] The zirconia powder according to [1] or [2], wherein the aluminum content is 200 ppm by mass or less. [4] The zirconia powder according to any one of [1] to [3], comprising zirconia powder particles with different amounts of stabilizing elements. [5] A zirconia powder according to any one of [1] to [3] above, comprising: zirconia powder particles containing at least one of tetragonal and cubic crystals, with a proportion of monoclinic zirconia of 2% or less; and zirconia powder particles containing at least one of tetragonal and cubic crystals in the crystalline phase, with a proportion of monoclinic zirconia exceeding 2%. [6] A zirconia powder according to any one of [1] to [5] above, wherein the crystallite diameter of monoclinic zirconia is 1.00 or less relative to the crystallite diameter of tetragonal zirconia and cubic zirconia. [7] A zirconia powder according to any one of [1] to [6] above, wherein the ratio of D90 [μm] to D10 [μm] is 1.5 or more. [8] Zirconia powder according to any one of [1] to [7] above, wherein the shrinkage rate after filling 4 g of the powder into a cylindrical mold with a diameter of 25 mm, press molding at a molding pressure of 98 MPa, and cold isostatic pressing (CIP) at a pressure of 196 MPa is 2.00% or more and 3.00% or less.[9] Zirconia powder according to any one of [1] to [8] above, wherein 3 g of the powder is filled into a cylindrical mold with a diameter of 25 mm, then press-formed at a molding pressure of 49 MPa and subjected to CIP treatment at a pressure of 196 MPa, then calcined in an air atmosphere, calcination temperature of 1000°C, heating rate of 50°C / hour, and holding time of 1 hour, and then sintered at atmospheric pressure with a heating rate of 10°C / min, holding temperature of 1500°C, and holding time of 2 hours, the total light transmittance is 50% or more.

[10] Contains stabilizing elements, the content of stabilizing elements in terms of oxides is 3.5 mol% or less, and the BET specific surface area is 9.0 m². ２ / g or more 16.0m ２ A first zirconia powder having a concentration of less than or equal to 1 / g and a monoclinic phase ratio of more than 2%, and a stabilizing element containing a stabilizing element whose oxide content is 5.8 mol% or more, a monoclinic phase ratio of 2% or less, and a difference of 7.5 m² from the BET specific surface area of ​​the first zirconia powder. ２A method for producing zirconia powder, comprising the step of mixing a second zirconia powder having a BET specific surface area of ​​1 / g or less with .

[11] The method for producing zirconia powder according to

[10] above, wherein the first zirconia powder is a zirconia powder obtained by a production method comprising a powder calcination step of heat-treating a composition containing zirconia sol and a stabilizing element source, wherein the content of stabilizing elements on an oxide basis is 3.5 mol% or less, at a holding temperature of 1190°C or less to obtain calcined powder, and a powder grinding step of grinding the calcined powder for 7.0 hours or less.

[12] The method for producing zirconia powder according to

[10] or

[11] above, wherein the second zirconia powder is a zirconia powder obtained by a production method comprising a powder calcination step of heat-treating a composition containing zirconia sol and a stabilizing element source, wherein the content of stabilizing elements on an oxide basis is 5.8 mol% or more, at a holding temperature of 1150°C or less for 3 hours or more to obtain calcined powder, and a powder grinding step of grinding the calcined powder for 7.0 hours or less.

[13] A method for producing a zirconia molded article using the zirconia powder described in any one of [1] to [9] above.

[14] A method for producing a zirconia calcined body using the zirconia powder described in any one of [1] to [9] above.

[15] The method for producing the zirconia calcined body according to

[14] above, wherein the zirconia calcined body contains a stabilizing element, the amount of the stabilizing element in terms of oxide is 5.6 mol% or more and less than 7.0 mol%, and the shrinkage rate when heated to a holding temperature of 1500°C in an air atmosphere at a heating rate of 600°C / hour and held at the holding temperature for 2 hours is 15% or more and 25% or less.

[16] A method for producing a zirconia sintered body using the zirconia powder described in any one of [1] to [9] above.

[17] The manufacturing method according to

[16] above, wherein the zirconia sintered body contains a stabilizing element, the content of the stabilizing element in terms of oxide is 5.6 mol% or more and less than 7.0 mol%, the total light transmittance to a D65 light source is 50% or more with a sample thickness of 1 ± 0.1 mm, and the ratio of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light at wavelengths of 400 nm to 700 nm is 1.5% or more with a sample thickness of 1 ± 0.1 mm.

[18] A calcined zirconia body containing a stabilizing element, wherein the stabilizing element content on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, and when heated in an air atmosphere at a heating rate of 600°C / hour to a holding temperature of 1500°C, the shrinkage rate when held at the holding temperature for 2 hours is 15% or more and 25% or less.

[19] A sintered zirconia body containing a stabilizing element, wherein the stabilizing element content on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the sample thickness is 1 ± 0.1 mm, the total light transmittance to a D65 light source is 50% or more, and the ratio of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light at wavelengths of 400 nm to 700 nm is 1.5% or more.

[20] A method for manufacturing a sintered zirconia body, comprising the step of sintering the calcined zirconia body described in

[18] under the following sintering conditions.

[0011] <Sintering Conditions> Sintering Method: Atmospheric pressure sintering atmosphere: Air atmosphere Holding temperature: 1500°C or higher and 1650°C or lower Holding time: 5 minutes or more and less than 1 hour Heating rate: (Heating rate from room temperature to 1100°C) 150°C / min or higher and 300°C / min or lower (Heating rate from 1100°C to holding temperature) 1°C / min or higher and 20°C / min or lower

[0012] This disclosure provides at least one of the following: a zirconia powder that can be manufactured by an industrial method to produce a translucent and transparent zirconia sintered body suitable for dental prosthetic materials for the incisal edges of anterior teeth; a method for manufacturing the same; and applications thereof.

[0013] This disclosure will be described in detail with reference to one embodiment. However, this disclosure is not limited to the following embodiment. Furthermore, this disclosure includes any combination of each configuration and parameter disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein. The terms used in this embodiment are as follows.

[0014] "Composition" refers to a substance having a certain composition, and examples include one or more selected from the group consisting of powder, molded body, calcined body, and sintered body. "Zirconia composition" refers to a composition mainly composed of zirconia, and more specifically, a composition consisting of zirconia. A zirconia composition may also contain components other than zirconia. In this embodiment, it is preferable that the zirconia composition is a composition that can serve as a precursor for a calcined body.

[0015] "Powder" refers to a composition that is an aggregate of powder particles and also possesses fluidity. "Zirconia powder" refers to a powder whose main component is zirconia, and is essentially a powder made of zirconia. Furthermore, "powder composition" refers to a composition composed of powders with different characteristics, and in particular, a composition composed of powders with different compositions.

[0016] "Granular powder" refers to a composition that is an aggregate of powder particles (granular particles) and is fluid, and in particular, a composition in which the powder particles are slowly aggregated. Granular powder is also used interchangeably with "granulated powder." "Zirconia granular powder" refers to a granular powder whose main component is zirconia, and is essentially a granular powder made of zirconia.

[0017] A "molded body" is a composition having a certain shape, composed of powder particles aggregated by physical force, and in particular, a composition that has not undergone heat treatment after the shape has been imparted (e.g., after molding). A "zirconia molded body" is a molded body whose main component is zirconia, and is essentially a molded body made of zirconia. Furthermore, molded bodies are used interchangeably with "compacted bodies".

[0018] A "calcined body" is a composition having a certain shape and composed of fused particles, and is a composition that has been heat-treated at a temperature below the sintering temperature. Furthermore, calcined bodies are used interchangeably with "semi-sintered bodies" or "pre-sintered bodies." A "zirconia calcined body" is a calcined body whose main component is zirconia, and is essentially a calcined body made of zirconia.

[0019] A "sintered body" is a composition having a certain shape and composed of crystalline particles, and is a composition that has been heat-treated at a temperature above the sintering temperature. A "zirconia sintered body" is a sintered body whose main component is zirconia, and is essentially a sintered body made of zirconia.

[0020] The "main component" is the component that constitutes the main phase (matrix, base material, parent phase) in the composition of the composition, and preferably has a mass percentage of 75% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 99% by mass or more, and is a component that is 100% by mass or less or less by mass.

[0021] A "stabilizing element" is an element that stabilizes the crystalline phase of zirconia by being dissolved in it.

[0022] "BET specific surface area" is the specific surface area [m²] measured by the BET multi-point method (5 points) using nitrogen as the adsorbent gas, in accordance with JIS R 1626. ２ This is the BET specific surface area measured under the following conditions: [ / g].

[0023] Adsorption medium: N ２ Adsorption temperature: -196°C Pretreatment conditions: Air atmosphere, degassing treatment at 250°C for 1 hour or more The BET specific surface area can be measured using a general specific surface area measuring device (e.g., Tristar II 3020, manufactured by Shimadzu Corporation). Note that "air atmosphere" mainly consists of nitrogen and oxygen, and is a nitrogen atmosphere with an oxygen concentration of 18 to 23 volume percent, and may contain moisture and other trace components.

[0024] The "average particle size" is the D50 in the volume particle size distribution of the powder measured by the wet method, and can be measured using a general-purpose instrument (e.g., MT3300EXII, manufactured by Microtrac-Bell). The sample to be measured should be a slurry made by dispersing powder, from which slow aggregation has been removed by dispersion treatment such as ultrasonic treatment, in pure water. When measuring the volume particle size distribution by the wet method, it is preferable to measure the slurry at a pH of 4.5 ± 1.5.

[0025] "Average granule size" is the D50 in the volume particle size distribution of granular powder measured by the dry method, and can be measured using a general instrument (e.g., MT3100II, Microtrac-Bell). The sample to be measured should be the granular powder in a slowly aggregated state, without any dispersion treatment such as sonication.

[0026] The "crystalline phase" is the crystalline structure of the composition as confirmed by the XRD pattern obtained by powder X-ray diffraction (hereinafter also referred to as "XRD") measurement. In this embodiment, the crystalline phase of zirconia can be considered to consist of one or more selected from the group of monoclinic, tetragonal, and cubic crystals. The "powder X-ray diffraction pattern (XRD pattern)" is an XRD pattern obtained by smoothing and removing background from the XRD profile of the composition obtained by XRD measurement under the following conditions using an analysis program attached to the X-ray diffractometer (for example, integrated powder X-ray analysis software PDXL Ver. 2.2, manufactured by RIGAKU Corporation).

[0027] Source: CuKα rays (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ = 26° to 33° 2θ = 72° to 76° Acceleration voltage / current: 40mA / 40kV Divergence longitudinal limiting slit: 10 mm Divergence / incident slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm XRD measurements can be performed using a general X-ray diffractometer (e.g., Ultima IV, manufactured by RIGAKU). For XRD measurement of a calcined body, the surface should be polished using sandpaper with a grit size of #400 in accordance with JIS R 6001-2, and then lapped with a diamond abrasive with a grit size of 3 μm. The calcined body should be used as the measurement sample, and the surface after lapping should be measured by XRD. For XRD measurement of a sintered body, the sintered body should be polished to a surface roughness Ra ≤ 0.02 μm, and the surface after polishing should be measured by XRD.

[0028] The "XRD peak" is a peak having a peak top at a diffraction angle 2θ detected in the XRD pattern obtained by the above-mentioned XRD measurement. The XRD peak may be detected using 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). In the present embodiment, "having no XRD peak" means that the peak is not detected as an XRD peak in the XRD pattern obtained by the above-mentioned XRD measurement.

[0029] Further, the XRD peak corresponding to each crystal plane of zirconia is an XRD peak having a peak top at the following 2θ.

[0030] 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° The XRD peak corresponding to the tetragonal (111) plane and the XRD peak corresponding to the cubic (111) plane are measured as one overlapping peak.

[0031] "Monoclinic phase ratio (M phase ratio)" refers to the proportion of monoclinic phase in the crystal phase of zirconia, and is calculated from the following formula (1) as the ratio of the area intensity of the monoclinic XRD peak to the total area intensity of the XRD peaks of tetragonal (T phase), cubic (C phase) and monoclinic (M phase) zirconia in the XRD pattern obtained by the above-mentioned XRD measurement (area ratio: area %).

[0032] f Ｍ = { [I ｍ (111) + I ｍ (11-1) ] / [ I ｍ (111) + I ｍ (11-1) + I ｔ (111) + I ｃ (111) ]} × 100 (1) In the above formula, f Ｍ is the monoclinic phase ratio [%], I ｔ(111) is the area intensity of the tetragonal (111) plane, I ｃ (111) is the area intensity of the cubic (111) plane, I ｍ (111) is the area intensity of the monoclinic (111) plane, I ｍ (11-1) is the area intensity of the monoclinic (11-1) plane, and I ｔ (111) + I ｃ (111) corresponds to the area intensity of the XRD peak (hereinafter also referred to as the "main XRD peak") having its peak top at 2θ = 30 ± 0.5°.

[0033] The area intensity of each XRD peak is a value obtained by analyzing the XRD pattern using the analysis program attached to the X-ray diffractometer (for example, the integrated powder X-ray analysis software PDXL Ver. 2.2, manufactured by RIGAKU Corporation).

[0034] The "tetragonal and cubic phase ratio (T+C phase ratio)" is the total proportion of tetragonal and cubic phases in the crystalline phase of zirconia, and is determined by the following formula (2), from the ratio of the area intensity of the tetragonal and cubic XRD peaks to the total area intensity of the tetragonal, cubic, and monoclinic XRD peaks in the XRD pattern obtained in the above-mentioned XRD measurement.

[0035] f Ｔ＋Ｃ = 100 - f Ｍ (2) In the above equation, f Ｔ＋Ｃ The tetragonal and cubic phase ratios [%], and f Ｍ This is the monoclinic phase fraction [%].

[0036] The "crystallite size of tetragonal and cubic crystals" and the "crystallite size of monoclinic crystals" are crystallite sizes obtained from the main XRD peak and the XRD peak corresponding to the monoclinic (11-1) plane (hereinafter also referred to as the "monoclinic XRD peak") obtained by the above-mentioned XRD measurement, and are values ​​calculated from the following equations (3) and (4).

[0037] D Ｔ＋Ｃ =κλ / βcosθ (3) D Ｍ =κλ / βcosθ (4) In the above equation, D Ｔ＋Ｃ The crystallite size [Å] is for tetragonal and cubic crystals, DＭ θ is the crystallite size of the monoclinic crystal [Å], κ is the Scherer constant (κ = 1), λ is the wavelength of the measured X-ray (0.15418 nm), β is the full width at half maximum [°] of the main XRD peak or monoclinic XRD peak, and θ is the Bragg angle of the main XRD peak or monoclinic XRD peak.

[0038] "Measured density" is calculated using the sample volume [cm³]. ３ The value [g / cm] can be obtained from the mass [g] of []. ３ ] The mass should be the mass obtained by weighing the sample. For the molded body and calcined body, the volume should be the volume determined by shape measurement, and for the sintered body, the volume should be the volume determined by the Archimedes method in accordance with JIS R 1634. The Archimedes method uses deionized water as the solvent, and the pretreatment should be carried out by boiling with deionized water as the solvent. In this embodiment, the measured density of the molded body is referred to as "molded body density," the measured density of the calcined body as "calcined body density," and the measured density of the sintered body as "sintered body density."

[0039] "Total light transmittance" is the ratio [%] of transmitted light (sum of linearly transmitted light and diffusely transmitted light) to incident light, measured in accordance with JIS K 7361-1 for a sample with a thickness of 1.0 ± 0.1 mm. The relationship between incident light and transmitted light is as follows:

[0040] The incident light = (linear transmitted light + diffuse transmitted light) + reflected light. The sample to be measured is a disc-shaped sintered body with a sample thickness of 1.0 ± 0.1 mm and a surface roughness Ra ≤ 0.02 μm on both sides. The measuring device should be a haze meter equipped with a D65 light source (for example, haze meter NDH4000, manufactured by Nippon Denshoku Co., Ltd.).

[0041] In this embodiment, the total light transmittance value measured for a sample with a thickness of 1.0 ± 0.1 mm is used, and the converted value of the total light transmittance for thicknesses other than 1.0 ± 0.1 mm can be estimated using the following equation (5) according to the Lambert-Beer law.

[0042] log(TT) ２ ) = D × log(TT １) (5) In the above formula, D is the sample thickness [mm], TT １ This is the total light transmittance at a sample thickness of 1.0 ± 0.1 mm, and TT ２ This is the total light transmittance at sample thickness D.

[0043] The "linear transmitted light / total transmitted light ratio" (hereinafter also referred to as the "PT / TT ratio") is the ratio [%] of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light (integrated value of transmitted light) of a measurement sample with a sample thickness of 1.0 ± 0.1 mm at measurement wavelengths of 400 nm to 700 nm.

[0044] For calculating the PT / TT ratio, the transmitted light (linear and diffuse transmitted light) should be measured using a disc-shaped sintered body with a sample thickness of 1.0 ± 0.1 mm and a surface roughness Ra ≤ 0.02 μm on both sides. The transmitted light should be measured at a wavelength of 400 nm to 700 nm. A general UV-VIS spectrophotometer equipped with a halogen lamp as the light source (e.g., V-650, manufactured by JASCO Corporation) can be used as the measuring device.

[0045] The integrated value of transmitted light and the integrated value of linear transmitted light in the measurement of the PT / TT ratio can be estimated using equation (5) as the integrated value of transmitted light and the converted value of linear transmitted light at sample thicknesses other than 1.0 ± 0.1 mm.

[0046] "Three-point bending strength" is one of the indicators of mechanical strength, and is measured in accordance with JIS R 1601. The value is measured on a columnar sample with a width of 4 mm and a thickness of 3 mm, with a distance of 30 mm between branches. In this embodiment, the average value of 10 measurements can be used as the value of the three-point bending strength.

[0047] Vickers hardness is one of the indicators of hardness, and can be measured using a typical Vickers tester equipped with a diamond square pyramidal indenter (for example, device name: Q30A, manufactured by QATM). The measurement is performed by statically pressing the indenter into the surface of the sample and visually measuring the diagonal length of the indentation formed on the surface of the sample. Using the obtained diagonal length, the Vickers hardness can be calculated from the following formula.

[0048] Hv = F / {d ２ In the above equation, Hv is the Vickers hardness [HV], F is the measured load [kgf], d is the diagonal length of the indentation [mm], and α is the face angle of the indenter [136°].

[0049] The following conditions can be used to measure Vickers hardness.

[0050] Measurement sample: Disc-shaped with a thickness of 3.0 ± 0.5 mm. Measurement load: 5 kgf. Prior to measurement, the measurement surface of the measurement sample should be polished with #800 waterproof abrasive paper to remove irregularities exceeding 0.1 mm as pretreatment.

[0051] "Atmospheric pressure sintering" is a process in which a sintered object (such as a molded body or calcined body) is heated at a temperature above the temperature at which zirconia densification progresses, without applying any external force to the object during sintering. [Zirconia powder] This embodiment contains stabilizing elements, with a stabilizing element content of 5.6 mol% or more and less than 7.0 mol% in terms of oxides, and a BET specific surface area of ​​9.0 m². ２ / g or more 16.0m ２ This invention relates to zirconia powder (hereinafter also referred to as "the powder of this embodiment") characterized by having a weight of 1 / g or less, containing monoclinic crystals in its crystalline phase, and having a monoclinic phase ratio of 2.5% to 20.0%. Even when the powder of this embodiment is applied to an industrial manufacturing method, that is, a method for manufacturing a zirconia sintered body by calcining a molded body made by dry molding of zirconia powder, applying a rapid heating rate (for example, 5°C / min or more), and holding it at a holding temperature for 1 hour or more under atmospheric pressure, a sintered body for cut ends can be obtained.

[0052] This embodiment relates to zirconia powder, and zirconia (ZrO ２The powder is mainly composed of zirconium dioxide. The powder of this embodiment is a zirconia powder containing stabilizing elements, that is, a zirconia powder containing stabilizing elements, and can also be considered as a zirconia powder with solid-solution stabilizing elements. It is preferable that the stabilizing elements are solid-solution in the zirconia, and it is preferable that the powder of this embodiment contains all of the stabilizing elements solid-solution in the zirconia, that is, it does not contain any unsolid-solution stabilizing elements. In this embodiment, the absence of unsolid-solution stabilizing elements can be confirmed by the fact that no XRD peaks corresponding to compounds of stabilizing elements are detected in the above-mentioned XRD measurement. On the other hand, it is permissible for the powder of this embodiment to contain unsolid-solution stabilizing elements as long as it is within the range that the effects of the powder of this embodiment are achieved.

[0053] The stabilizing element is preferably one or more selected from the group consisting of yttrium (Y), calcium (Ca), magnesium (Mg), niobium (Nb), europium (Eu), gadolinium (Gd), ytterbium (Yb), praseodymium (Pr), lanthanum (La), scandium (Sc), erbium (Er), and terbium (Tb), and more preferably one or more selected from the group consisting of yttrium, calcium, magnesium, niobium, gadolinium, ytterbium, praseodymium, lanthanum, scandium, erbium, and terbium, and more preferably one or more selected from the group consisting of yttrium, calcium, magnesium, erbium, and terbium, and more preferably at least one of yttrium and erbium, and more preferably yttrium.

[0054] The content of stabilizing elements in the powder of this embodiment, calculated on an oxide basis (hereinafter also referred to as "stabilizing element amount," and if the stabilizing element is yttrium, etc., it will also be referred to as "yttrium amount," etc.), is 5.6 mol% or more and less than 7.0 mol%. A stabilizing element amount of 5.6 mol% or more allows for the production of zirconia sintered bodies with aesthetic properties suitable for use as sintered bodies for cut ends, even when industrial manufacturing is applied, particularly zirconia sintered bodies with high transparency. On the other hand, if the stabilizing element amount is 7.0 mol% or more, sintered bodies for cut ends cannot be obtained through industrial sintering.

[0055] Within the above-mentioned range of stabilizing element amounts, the transparency of the resulting zirconia sintered body tends to increase as the amount of stabilizing element increases; therefore, it is preferable that the amount of stabilizing element be 5.8 mol% or more, 5.9 mol% or more, or 6.0 mol% or more. On the other hand, it is preferable that the amount of stabilizing element be 6.9 mol% or less, 6.6 mol% or less, 6.4 mol% or less, or 6.3 mol% or less, as this makes it easier for the resulting zirconia sintered body to possess both translucency and transparency suitable for dental prosthetic materials for the incisal edges of anterior teeth. Examples of stabilizing element amounts in the powder of this embodiment include 5.8 mol% or more and 6.9 mol% or less, 5.9 mol% or more and 6.6 mol% or less, 6.0 mol% or more and 6.4 mol% or less, or 6.0 mol% or more and 6.3 mol% or less.

[0056] The amount of stabilizing element is ZrO ２ It is calculated from the ratio [mol%] of the stabilizing elements in oxide form to the total of the converted zirconium (Zr) and the stabilizing elements in oxide form.

[0057] The powder of this embodiment is preferably a powder made of zirconia containing stabilizing elements, and preferably does not contain elements that affect the sintering behavior of zirconia (hereinafter also referred to as "auxiliary elements") (i.e., the content of auxiliary elements is 0 ppm by mass). Examples of auxiliary elements include one or more selected from the group consisting of aluminum (Al), silicon (Si), and germanium (Ge), and more specifically, at least one of aluminum and silicon, or aluminum.

[0058] In the powder of this embodiment having the above-mentioned amount of stabilizing elements, the presence of a large amount of auxiliary elements tends to promote localized sintering and inhibit porosity elimination. As a result, even if a sintered body for the cut end can be obtained with standard sintering, it becomes difficult to obtain a sintered body for the cut end with industrial sintering. On the other hand, the inclusion of auxiliary elements within a range that does not inhibit porosity elimination in industrial sintering is acceptable. For example, the amount of auxiliary elements in the powder of this embodiment, calculated on an oxide basis (hereinafter also referred to as "amount of auxiliary elements," and if the auxiliary element is aluminum, etc., also referred to as "aluminum amount," etc.), can be 200 ppm by mass or less, 100 ppm by mass or less, 50 ppm by mass or less, 10 ppm by mass or less, or 1 ppm by mass or less. When the powder of this embodiment contains auxiliary elements, the amount of auxiliary elements can be exemplified as greater than 0 ppm by mass or 1 ppm by mass or more. The amount of auxiliary elements in the powder of this embodiment may be, for example, 0 ppm to 200 ppm by mass, 0 ppm to 100 ppm by mass, 0 ppm to 10 ppm by mass, more than 0 ppm to 200 ppm by mass, more than 0 ppm to 100 ppm by mass, or 1 ppm to 10 ppm by mass.

[0059] The form in which the auxiliary element is contained in the powder of this embodiment is arbitrary, and may include one or more selected from the group of halides, hydroxides, oxyhydroxides, and oxides, and more specifically, oxides. As an oxide of the auxiliary element, alumina (Al ２ O ３ ), silica (SiO ２ ), Germania (Ge ２ O ３ ) can be used as an example.

[0060] Because it has a significant impact on the sintering behavior, it is preferable that the powder of this embodiment does not contain aluminum (Al). It is preferable that the amount of aluminum in the powder of this embodiment is 0 ppm by mass, but even if aluminum is included, it may be 200 ppm by mass or less, 100 ppm by mass or less, 50 ppm by mass or less, or 10 ppm by mass or less, or 0 ppm or more, greater than 0 ppm by mass, or 1 ppm or more by mass. The amount of aluminum in the powder of this embodiment may be, for example, 0 ppm or more and 200 ppm by mass or less, 0 ppm or more and 10 ppm by mass or less, or greater than 0 ppm by mass and 200 ppm by mass or less, greater than 0 ppm by mass and 100 ppm by mass or less, or 1 ppm or more by mass and 10 ppm by mass or less, but it is preferable that it is 1 ppm by mass or less. In other words, the powder of this embodiment does not contain aluminum, or contains aluminum, with the amount of aluminum being 200 ppm by mass or less.

[0061] The amount of additive elements is determined from the mass ratio [mass%] of the additive elements, converted to oxides, to the total mass of the metal elements, converted to oxides (hereinafter also referred to as "amount of metal elements"). In this embodiment, the amount of metal elements is the total mass of the metal elements (including rare earth elements) contained in the composition, converted to oxides.

[0062] The powder of this embodiment does not have to contain coloring elements, but it may contain coloring elements as long as it is within a range that provides the desired effect. The coloring elements are elements that have the function of coloring the zirconia sintered body, and examples include at least one of the transition metal elements other than zirconium and hafnium, and lanthanide rare earth elements (lanthanide elements). Specific examples of coloring elements include one or more selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), neodymium (Nd), europium (Eu), gadolinium (Gd), ytterbium (Yb), praseodymium (Pr), erbium (Er), and terbium (Tb), one or more selected from the group consisting of iron, cobalt, nickel, manganese, neodymium, and europium, one or more selected from the group consisting of iron, cobalt, manganese, and neodymium, and one or more selected from the group consisting of iron and cobalt. The coloring element may be an element that functions as both a stabilizing element and a coloring element. Examples of such coloring elements include one or more selected from the groups europium, gadolinium, ytterbium, praseodymium, erbium, and terbium. The coloring element may also be an element that does not function as a stabilizing element. Examples of such coloring elements include transition metal elements other than zirconium and hafnium, as well as one or more selected from the groups iron, cobalt, nickel, and manganese, and further, one or more selected from the groups iron, cobalt, and manganese. In this embodiment, yttrium and scandium, which function as stabilizing elements, are not treated as transition metal elements for convenience.

[0063] The coloring element content of the powder in this embodiment (hereinafter also referred to as "coloring element amount") is 0.25% by mass or less or 0.15% by mass or less, and may be 0% by mass or more, greater than 0% by mass or 0.01% by mass or more (100 ppm by mass or more), with examples including 0% by mass or more and 0.25% by mass or less, or greater than 0% by mass and 0.15% by mass or less. In other words, the powder in this embodiment does not contain coloring elements, or contains coloring elements, with the amount of coloring elements being 0.25% by mass or less.

[0064] The amount of coloring element is determined from the mass percentage [mass%] of the coloring element, converted to oxide form, relative to the amount of metallic element.

[0065] As an oxide equivalent for metallic elements, yttrium is Y ２ O ３ Calcium is CaO, magnesium is MgO, and scandium is Sc ２ O ３ Terbium is Tb ４ O ７ Erbium is Er ２ O ３ Aluminum is Al ２ O ３ , silicon is SiO ２ Germanium is Ge ２ O ３ Iron is Fe ２ O ３ Cobalt is Co ３ O ４ Nickel is NiO, manganese is Mn ３ O ４ , Lantern is La ２ O ３ Niobium is Nb ２ O ５ PraseoGym is promoting ２ O ３ Neodymium is Nd ２ O ３ Europium is EU ２ O ３ Gadolinium is Gd ２ O ３ And Ytterbium is Yb ２ O ３ This can be illustrated by the following example.

[0066] The powder of this embodiment is hafnia (HfO ２ It is permissible for the product to contain unavoidable impurities such as ). In this embodiment, when calculating values ​​derived from the composition, such as density, hafnium (Hf) may be treated as zirconium and these values ​​may be calculated accordingly.

[0067] In this embodiment, for example, the composition of zirconia powder containing aluminum as an auxiliary element, yttrium and erbium as stabilizing elements, and iron (and erbium) as a coloring element can be obtained as follows. Note that erbium functions as both a stabilizing element and a coloring element.

[0068] Yttrium content = {Y ２ O ３ / (ZrO ２ +Y ２ O ３ +Er ２ O ３ )} × 100 [mol%] Erbium content (erbium content as a stabilizing element) = {Er ２ O ３ / (ZrO ２ +Y ２ O ３ +Er ２ O ３ )} × 100 [mol%] Stabilizing element content = {(Y ２ O ３ +Er ２ O ３ ) / (ZrO ２ +Y ２ O ３ +Er ２ O ３ )} × 100 [mol%] Aluminum content (auxiliary element content) = {Al ２ O ３ / (ZrO ２ +Y ２ O ３ +Er ２ O ３ +Al ２ O ３ +Fe ２ O ３ )} × 1000000 [mass ppm] Iron content = {Fe ２ O ３ / (ZrO ２ +Y ２ O ３ +Er ２ O ３ +Al ２ O ３ +Fe ２ O ３)} × 100 [mass%] Erbium content (amount of erbium as a coloring element) = {Er ２ O ３ / (ZrO ２ +Y ２ O ３ +Er ２ O ３ +Al ２ O ３ +Fe ２ O ３ )}×100 [mass%] Coloring element amount = {(Fe ２ O ３ +Er ２ O ３ ) / (ZrO ２ +Y ２ O ３ +Er ２ O ３ +Al ２ O ３ +Fe ２ O ３ )}×100 [mass%] Metal element amount = ZrO ２ +Y ２ O ３ +Er ２ O ３ +Al ２ O ３ +Fe ２ O ３ The powder of this embodiment may contain a binder. Including a binder improves handling and shape retention during molding. The binder can be any binder that can be used for granulation and molding of 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 acrylic resin, and more preferably an acrylic resin. In this embodiment, the acrylic resin is a polymer containing at least one of acrylic acid ester and 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.) and KS910 (product name, manufactured by Nippon Kayaku Co., Ltd.).

[0069] The binder content may be 0.5% by mass or more, or 1.0% by mass or more, and may also be 10.0% by mass or less, or 5.0% by mass or less, and further, it may be 0.5% by mass or more and 10.0% by mass or less, or 1.0% by mass or more and 5.0% by mass or less.

[0070] The binder content in the powder of this embodiment can be determined from the following formula (6).

[0071] {(W １ -W ２ ) / W １} × 100 (6) In the above equation, W １ This is the mass [g] of the zirconia composition before heat treatment in an air atmosphere at a temperature between 250°C and 400°C, and W ２ This is the mass [g] of the zirconia composition after heat treatment in an air atmosphere at 250°C to 400°C. Note that, due to differences in calculation methods, the total content of the powder including the binder (= amount of metal element + amount of binder) does not have to be 100% by mass, and may exceed 100% by mass.

[0072] The powder of this embodiment contains monoclinic crystals in its crystalline phase, and also has a monoclinic phase ratio (f ＭThe monoclinic phase ratio is 2.5% or more and 20.0% or less, preferably 3.0% or more, 3.4% or more, 4.0% or more, or 5.0% or more, and preferably 15.0% or less, 12.0% or less, or 10.0% or less, and examples include 3.0% or more and 20.0% or less, 3.4% or more and 15.0% or less, 4.0% or more and 12.0% or less, or 5.0% or more and 10.0% or less. If the monoclinic phase ratio is less than 2.5%, a stable sintered body for the cut end cannot be obtained in industrial manufacturing, and the transparency of the sintered body obtained by industrial manufacturing tends to be low. Also, if the monoclinic phase ratio exceeds 20.0%, the transparency of the zirconia sintered body obtained by industrial manufacturing will be low, or the light transmittance will be high but the transparency will be low. One reason why a sintered body for cutting edges can be obtained even in industrial manufacturing is that the powder of this embodiment possesses the above-mentioned stabilizing element content, monoclinic phase ratio, and BET specific surface area. Specifically, in the initial stages of sintering, a phase transformation accompanied by volume shrinkage causes the monoclinic phase to become tetragonal, and a network of pores is formed between the powder particles. When the powder as a whole satisfies the above-mentioned monoclinic phase ratio, sintering shrinkage occurs in the initial stages of sintering of the monoclinic phase, which suppresses the densification associated with the rapid sintering shrinkage of the subsequent tetragonal and cubic phases. As a result, pore trapping (closed pore formation) becomes less likely to occur, and it is thought that the sintered material can be densified even in industrial manufacturing without the need for forced pore removal such as pressure sintering or vacuum sintering, promotion of pore removal by oxygen replacement such as a high-oxygen concentration atmosphere, or pore removal by gentle heating that takes a long time.

[0073] In the powder of this embodiment, the zirconia crystal phase consists of one or more selected from the group of monoclinic, tetragonal, and cubic crystals, and therefore the monoclinic phase ratio and the T+C phase ratio have the relationship shown in formula (2) above. For this reason, the crystalline phase of the powder of this embodiment is characterized by the main phase being at least one of tetragonal and cubic crystals, and the T+C phase ratio in the monoclinic phase ratio is greater than 76.5% and less than 97.0%, corresponding to less than 96.6%, less than 96.0%, or less than 95.0%, and also to greater than 80.0%, greater than 88.0%, or greater than 90.0%, and further to greater than 80.0% and less than 96.6%, greater than 88.0% and less than 96.0%, or greater than 90.0% and less than 95.0%.

[0074] The BET specific surface area of ​​the powder in this embodiment is 9.0 m². ２ / g or more 16.0m ２ It is less than or equal to / g. In zirconia powder having the above-mentioned amount of stabilizing elements and monoclinic phase ratio, the BET specific surface area is 9.0 m². ２ By having a BET specific surface area of ​​16.0 m² or more, a zirconia sintered body suitable for cut edge applications can be obtained even through industrial sintering. ２ When the value exceeds 1 / g, the transparency of sintered bodies obtained by industrial sintering tends to decrease. The BET specific surface area is 9.5 m². ２ / g or more, 10.0m ２ / g or more or 10.5m ２ It is preferable that the BET specific surface area be 16.0 m² or more. This makes it easier to obtain a zirconia sintered body with translucency suitable for sintered bodies used for cut ends. ２ It is less than / g and 15.0m ２ / g or less, 13.0m ２ / g or less or 12.0m ２ It is preferable that the amount is less than or equal to / g. The BET specific surface area of ​​the powder in this embodiment is 9.5 m². ２ / g or more 15.0m ２ / g or less, 10.0m ２ / g or more 13.0m ２ / g or less, or 10.5m ２ / g or more 12.0m ２ One example is that it should be less than or equal to / g.

[0075] The crystallite size (D) of the monoclinic powder in this embodiment Ｍ The crystallite size is 280 Å or more or 290 Å or more, and can also be 325 Å or less, 310 Å or less, or 300 Å or less. The crystallite size of the monoclinic zirconia powder in this embodiment can be exemplified as 280 Å or more and 320 Å or less, or 290 Å or more and 300 Å or less.

[0076] The crystallite size (D) of the tetragonal and cubic zirconia powders of this embodiment. Ｔ＋ＣThe crystallite size of the tetragonal zirconia and cubic zirconia in this embodiment can be exemplified as 325 Å or more, 330 Å or more, 335 Å or more, or 340 Å or more, and also 450 Å or less, 400 Å or less, 398 Å or less, or 380 Å or less.

[0077] The crystallite size (D) of tetragonal zirconia and cubic zirconia in the powder of this embodiment. Ｔ＋Ｃ The crystallite size (D) of monoclinic zirconia relative to ) Ｍ） The crystallite size ratio (hereinafter also referred to as the "crystallite size ratio") is 1.00 or less, 0.95 or less, or 0.90 or less, and can also be 0.70 or more, 0.75 or more, or 0.80 or more. Examples of crystallite size ratios include 0.70 or more and 1.00 or less, 0.75 or more and 0.95 or less, or 0.80 or more and 0.90 or less.

[0078] The average particle size of the powder in this embodiment is preferably 0.30 μm or more, 0.35 μm or more, or 0.40 μm or more, and also preferably 0.60 μm or less, 0.55 μm or less, or 0.50 μm or less. For example, it may be 0.30 μm or more and 0.60 μm or less, 0.35 μm or more and 0.55 μm or less, or 0.40 μm or more and 0.50 μm or less. Having such an average particle size makes it less likely for defects caused by the aggregation of powder particles to occur even when molded by dry molding.

[0079] The powder of this embodiment only needs to have an appropriate particle size distribution, and the ratio of D90 [μm] to D10 [μm] (hereinafter also referred to as "D90 / D10") is 1.5 or more or 1.6 or more, and 2.0 or less or 1.8 or less, and is 1.5 to 2.0 or 1.6 to 1.8.

[0080] To improve operability (handling), the powder in this embodiment may be a granular powder. For example, the granular powder may have a particle size of 30 μm or more and 80 μm or less. Granulation can be achieved by any method that results in a state of slow aggregation of zirconia powder, and examples of granulation methods include spray granulation.

[0081] The powder of this embodiment is preferably highly moldable in dry molding. For example, after filling 4 g of the powder of this embodiment into a cylindrical mold with a diameter of 25 mm, press molding is performed at a molding pressure of 98 MPa and cold isostatic pressing (hereinafter also referred to as "CIP") at a pressure of 196 MPa, the shrinkage rate (hereinafter also referred to as "molding shrinkage rate") is 2.00% or more and 3.00% or less. Preferably, the molding shrinkage rate is 2.20% or more or 2.30% or more, and also preferably 2.80% or less, 2.50% or less, or 2.45% or less.

[0082] The molding shrinkage rate in this embodiment can be determined from formula (7).

[0083] Molding shrinkage rate [%] = {(D1 - D2) / D1} × 100 (7) In the above formula, D1 is the diameter of the mold (25 mm), and D2 is the diameter of the molded body after CIP treatment [mm]. The diameter of the molded body can be determined by measuring 3 ± 1 points with a caliper and taking the average value of the obtained values.

[0084] Even when the powder of this embodiment is subjected to an industrial manufacturing process, a zirconia sintered body with high light transmittance can be obtained. When 3 g of the powder of this embodiment is filled into a cylindrical mold with a diameter of 25 mm, press-molded at a molding pressure of 49 MPa and subjected to CIP treatment at a pressure of 196 MPa, calcined in an air atmosphere, calcined at a calcination temperature of 1000°C, heated at a heating rate of 50°C / hour, and held for 1 hour, and then sintered at atmospheric pressure at a heating rate of 10°C / min, held at a holding temperature of 1500°C, and held for 2 hours, it is preferable that the total light transmittance is 50% or more, 51% or more, 53% or more, or 55% or more, and also 62% or less, 60% or less, 59% or less, or 58% or less, and furthermore, 50% or more and 62% or less, 53% or more and 59% or less, or 55% or more and 58% or less.

[0085] Furthermore, even when applied to industrial manufacturing, the powder of this embodiment can stably and repeatedly produce zirconia sintered bodies with high total light transmittance, and even sintered bodies for cut ends. This results in a zirconia powder suitable for industrial production.

[0086] For example, in this embodiment, when 3 g of the powder is filled into a cylindrical mold with a diameter of 25 mm, then press-molded at a molding pressure of 49 MPa and subjected to CIP treatment at a pressure of 196 MPa, and then heated in an air atmosphere at a heating rate of 600 °C / hour to a holding temperature of 1500 °C, and held at that holding temperature for 2 hours, the standard deviation of the total light transmittance (the standard deviation of the total light transmittance of the three zirconia sintered bodies) when these three processes are performed is 1.5% or less, 1.2% or less, or 0.5% or less, and also 0% or more, 0.01% or more, or 0.05% or more, and further exemplifies 0% to 1.5%, 0.01% to 1.2%, or 0.05% to 0.5%.

[0087] The powder of this embodiment possesses both the above-mentioned amount of stabilizing elements and monoclinic phase ratio. Generally, the amount of stabilizing elements affects the crystalline phase of zirconia, and the proportion of monoclinic zirconia tends to decrease as the amount of stabilizing elements increases. For example, the proportion of monoclinic zirconia in zirconia with a stabilizing element amount of 6 mol% or less is about 0% to 2%, and the proportion of monoclinic zirconia in zirconia with a stabilizing element amount exceeding that is 0% to 1%. Thus, zirconia having the above-mentioned amount of stabilizing elements usually consists of zirconia whose crystalline phase is at least one of tetragonal and cubic, and substantially does not contain monoclinic crystals in its crystalline phase. Therefore, the monoclinic phase ratio of zirconia powder composed of zirconia powder particles having the above-mentioned amount of stabilizing elements is 2% or less, and even 0%.

[0088] In contrast, the powder of this embodiment is a zirconia powder that has the above-mentioned amount of stabilizing elements, contains monoclinic crystals in its crystalline phase, and also has the above-mentioned monoclinic phase ratio. Therefore, the powder of this embodiment can also be considered as a zirconia powder composed of zirconia powder particles with different amounts of stabilizing elements, or it may be a zirconia powder having the above-mentioned amount of stabilizing elements and composed of powder particles with different amounts of stabilizing elements. Furthermore, the powder of this embodiment may be a zirconia powder composed of zirconia powder particles (hereinafter also referred to as "TC particles") which contain at least one of tetragonal and cubic crystals and have a monoclinic zirconia content of 2% or less, and zirconia powder particles (hereinafter also referred to as "M particles") which contain at least one of tetragonal and cubic crystals in their crystalline phase and have a monoclinic zirconia content of more than 2%. Moreover, the powder may be a mixed powder of a zirconia powder having the above-mentioned amount of stabilizing elements, consisting of zirconia powder particles which contain at least one of tetragonal and cubic crystals in their crystalline phase and have a monoclinic zirconia content of 2% or less, and zirconia powder particles which contain at least one of tetragonal and cubic crystals in their crystalline phase and have a monoclinic zirconia content of more than 2%.

[0089] TC particles are zirconia powder particles that contain at least one of tetragonal and cubic crystals, with a monoclinic zirconia content of 2% or less. Furthermore, they may be one or more selected from the group consisting of zirconia powder particles that do not contain monoclinic crystals in their crystalline phase, zirconia powder particles whose crystalline phase is tetragonal, zirconia powder particles whose crystalline phase is cubic, and zirconia powder particles whose crystalline phase is tetragonal and cubic. In other words, they may be zirconia powder particles whose crystalline phase is tetragonal and cubic. Since TC particles substantially consist of at least one of tetragonal and cubic crystals, it is preferable that the monoclinic phase ratio is 0% (i.e., zirconia powder particles whose crystalline phase consists of at least one of tetragonal and cubic crystals). However, they may contain monoclinic crystals to the extent that they do not cause volume shrinkage during sintering, and TC particles may be zirconia powder particles whose crystalline phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals.

[0090] The proportion of monoclinic zirconia in the TC particles can be 0% or more, or greater than 0%, and can also be 2% or less, 1% or less, 0.5% or less, or 0.1% or less. Furthermore, examples include 0% to 2%, 0% to 1%, 0% to 0.1%, or greater than 0% and 0.1% or less.

[0091] The amount of stabilizing elements in TC particles can be 5.8 mol% or more, 6.0 mol% or more, or 6.3 mol% or more, and can also be 8.0 mol% or less, 7.5 mol% or less, or 6.8 mol% or less. The amount of stabilizing elements in TC particles can be 5.8 mol% or more and 8.0 mol% or less, 6.0 mol% or more and 7.5 mol% or less, or 6.3 mol% or more and 6.8 mol% or less.

[0092] The M particles are zirconia powder particles that contain at least one of tetragonal and cubic crystal phases, with a proportion of monoclinic zirconia exceeding 2%, and furthermore, contain monoclinic crystal phases. These particles may be zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals, furthermore, zirconia powder particles whose crystal phase consists of tetragonal and monoclinic crystals, furthermore, zirconia powder particles whose crystal phase consists of cubic and monoclinic crystals, and zirconia powder particles whose crystal phase consists of tetragonal, cubic and monoclinic crystals. In addition, the M particles may be zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals. The proportion of monoclinic zirconia in the M particles is preferably greater than 2.0%, 5.0% or more, 30.0% or more, 35.0% or more, 40.0% or more, or 43.0% or more, and preferably 65.0% or less, 57.0% or less, or 53.0% or less. Examples include greater than 2.0% and 65.0% or less, 5.0% or more and 65.0% or less, 40.0% or more and 57.0% or less, or 43.0% or more and 53.0% or less.

[0093] The amount of stabilizing elements in the M particles is 3.5 mol% or less, preferably 3.0 mol% or less, 2.8 mol% or less, or 2.6 mol% or less. The M particles only need to contain stabilizing elements, and examples include the amount of stabilizing elements being 1.0 mol% or more, 1.5 mol% or more, or 2.0 mol% or more, and furthermore, 1.0 mol% or more and 3.5 mol% or less, 1.5 mol% or more and 3.0 mol% or less, or 2.0 mol% or more and 2.6 mol% or less.

[0094] It is preferable that TC particles have a higher amount of stabilizing elements than M particles. This facilitates pore removal during industrial sintering, so it is preferable that the difference in the amount of stabilizing elements between M particles and TC particles (hereinafter also referred to as the "difference in the amount of stabilizing elements," and in the case of yttrium, etc., also referred to as the "difference in the amount of yttrium") be 6.0 mol% or less, 5.5 mol% or less, or 5.0 mol% or less. Examples of differences in the amount of stabilizing elements include 3.1 mol% to 3.6 mol% or more, or 4.1 mol% or more. For example, examples include 3.1 mol% to 6.0 mol%, 3.6 mol% to 5.5 mol%, or 4.1 mol% to 5.0 mol%. Having such a difference in the amount of stabilizing elements facilitates pore removal during sintering in industrial sintering.

[0095] The powder of this embodiment may contain zirconia powder particles having a stabilizing element content of more than 3.5 mol% and less than 5.8 mol%, provided that this does not affect its effect.

[0096] The presence of TC particles and M particles in the powder of this embodiment can be confirmed by micro-Raman spectroscopy. Specifically, micro-Raman spectroscopy was performed, and the reading was 148 ± 5 cm⁻¹. －１ , 264±5cm －１ , 333±5cm －１ , 383±5cm －１ , 474±5cm －１ , and 641±5cm －１ The presence of a peak with a peak top indicates the presence of TC particles, and the measurement is 181±5 cm. －１ , 192±5cm －１ , 224±5cm －１, 319±5cm －１ , 477±5cm －１ , 618±5cm －１ , and 637±5cm －１ The presence of M particles can be confirmed by the presence of a peak with a peak top. Micro-Raman spectroscopy can be performed using a general-purpose micro-Raman spectrometer (instrument name: NRS-5100, manufactured by JASCO Corporation) under the following conditions: Instrument: JASCO NRS-5100 Laser wavelength: 532 nm Measurement wavenumber range: 100 to 3400 cm ―１ Measurement magnification: 20x

[0097] The amount of stabilizing elements in TC particles and M particles can be measured by STEM-EDS using general equipment (e.g., TEM: JEM-2100F, JEOL Ltd.; EDS: JED-2300T, JEOL Ltd.). That is, in the TEM observation diagram, powder particles that are observed without overlapping are irradiated with an electron beam to obtain the EDS spectrum of each zirconia powder particle. From the obtained EDS spectrum, the amount of stabilizing elements in each powder particle can be calculated from the peak intensity of the stabilizing element relative to the sum of the peak intensity of the stabilizing element and the peak intensity of zirconium (= [(stabilizing element in oxide equivalent) / {(stabilizing element in oxide equivalent) + ZrO ２ The measurement should be performed on}] × 100:mol%). STEM-EDS measurement should be performed on 30 or more, preferably 50 ± 5, zirconia powder particles randomly selected.

[0098] The characteristics of the TC particles and M particles, other than the monoclinic phase ratio and the amount of stabilizing elements, may be the same as those of the powder of this embodiment described above.

[0099] The powder of this embodiment may be a zirconia powder composition, a zirconia powder composition composed of zirconia powder particles with different amounts of stabilizing elements, or a zirconia powder composition composed of zirconia powder particles with different activity levels. Furthermore, the powder of this embodiment may be a zirconia powder composed of zirconia powder particles that contain at least one of tetragonal and cubic crystal phases and have a monoclinic zirconia content of 2% or less, or zirconia powder particles that contain at least one of tetragonal and cubic crystal phases and have a monoclinic zirconia content of more than 2%. Furthermore, the zirconia powder composition may consist of a powder comprising a first zirconia powder particle having a monoclinic phase zirconia content of 65% or less, and a second zirconia powder particle having a monoclinic phase zirconia content of 2% or less, or a zirconia powder composition consisting of a first zirconia powder particle having a monoclinic phase zirconia content of 65% or less, and a second zirconia powder particle having a monoclinic phase zirconia content of 2% or less. Furthermore, the zirconia powder composition may consist of a powder comprising: first zirconia powder particles containing stabilizing elements, with a content of stabilizing elements on an oxide basis of 3.5 mol% or less, and a monoclinic phase zirconia ratio of 65% or less; and second zirconia powder particles containing stabilizing elements, with a content of stabilizing elements on an oxide basis of 5.8 mol% or more, and a monoclinic phase zirconia ratio of 2% or less; or a zirconia powder composition consisting of first zirconia powder particles containing stabilizing elements, with a content of stabilizing elements on an oxide basis of 3.5 mol% or less, and a monoclinic phase ratio of 65% or less; and second zirconia powder particles containing stabilizing elements, with a content of stabilizing elements on an oxide basis of 5.8 mol% or more, and a monoclinic phase zirconia ratio of 2% or less. Furthermore, the powder of this embodiment may be a mixed powder of zirconia powder composed of first zirconia powder particles and zirconia powder composed of second zirconia powder particles.

[0100] In a zirconia powder composition composed of zirconia powder particles with different amounts of stabilizing elements, the amounts of stabilizing elements in all zirconia powder particles constituting the zirconia powder do not necessarily have to be different from each other.

[0101] Furthermore, if the method for producing the powder composition is known, the amount of stabilizing elements in the zirconia powder used as the starting material may be considered as the amount of stabilizing elements in the zirconia powder contained in the powder composition.

[0102] The powder of this embodiment can be used for known applications of zirconia powder and can be used as one or more precursors selected from the group consisting of molded bodies, calcined bodies, and sintered bodies. Furthermore, the powder of this embodiment can be used as one or more precursors selected from the group consisting of various catalysts or additives, structural materials, optical materials, decorative materials, dental materials, electrode materials, and solid electrolyte materials, and is suitable as a precursor for dental prostheses, and even more so as a precursor for dental prostheses for the incisal edges of anterior teeth. Moreover, it is suitable as a precursor for the manufacture of sintered bodies for incisal edges by industrial sintering, and even more so as a precursor for the manufacture of sintered bodies for incisal edges by industrial manufacturing. [Method for manufacturing zirconia powder] The method for manufacturing the powder of this embodiment is arbitrary as long as it is a manufacturing method that can produce zirconia powder that satisfies the above-described configuration. A preferred manufacturing method for zirconia powder includes a step of mixing: a first zirconia powder composed of zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals, and in which case the proportion of monoclinic zirconia is greater than 2%; and a second zirconia powder composed of zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals, and in which case the proportion of monoclinic zirconia is 2% or less; or a first zirconia powder composed of zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals; and a second zirconia powder composed of zirconia powder particles whose crystal phase consists of at least one of tetragonal and cubic crystals.

[0103] A more preferred manufacturing method involves a material containing stabilizing elements, wherein the content of stabilizing elements in terms of oxides is 3.5 mol% or less, and the BET specific surface area is 9.0 m². ２ / g or more 16.0m ２ A first zirconia powder having a concentration of less than or equal to 1 / g and a monoclinic phase fraction of more than 2%, and a stabilizing element containing a stabilizing element whose oxide content is 5.8 mol% or more, a monoclinic phase fraction of 2% or less, and a difference of 7.5 m² from the BET specific surface area of ​​the first zirconia powder. ２ Preferably, the method for producing zirconia powder is a step of mixing a second zirconia powder having a BET specific surface area of ​​0.5 / g or less with 1 (hereinafter also referred to as the "mixing step").

[0104] The first zirconia powder (hereinafter also referred to as "first powder") used in the mixing process contains stabilizing elements, and the content of stabilizing elements in terms of oxides (amount of stabilizing elements) is 3.5 mol% or less, preferably 3.0 mol% or less, 2.8 mol% or less, or 2.6 mol% or less. With such an amount of stabilizing elements, the crystalline phase consists of at least one of tetragonal and cubic crystals and monoclinic crystals, and the monoclinic crystals are included in the zirconia crystalline phase to the extent that the monoclinic phase ratio of the first powder is as described later. The first powder only needs to contain stabilizing elements, but examples of the amount of stabilizing elements include 1.0 mol% or more, 1.5 mol% or more, or 2.0 mol% or more, and furthermore, 1.0 mol% or more and 3.5 mol% or less, 1.5 mol% or more and 3.0 mol% or less, or 2.0 mol% or more and 2.6 mol% or less.

[0105] The monoclinic phase ratio of the first powder is more than 2.0%, preferably 5.0% or more, 30.0% or more, 35.0% or more, 40.0% or more, or 43.0% or more, and preferably 65.0% or less, preferably 57.0% or less, or 53.0% or less. Having such a monoclinic phase ratio in the first powder can suppress volume shrinkage caused by the second zirconia powder during sintering. Examples of monoclinic phase ratios for the first powder include more than 2.0% and 65.0% or less, 5.0% or more and 65.0% or less, 40.0% or more and 57.0% or less, or 43.0% or more and 53.0% or less.

[0106] The first powder has the monoclinic phase ratio described above, and also has a BET specific surface area of ​​9.0 m². ２ / g or more 16.0m ２ It is less than / g. The BET specific surface area of ​​the first powder is 9.0 m². ２ / g or more, 10.0m ２ / g or more, 10.5m ２ / g or more, 11.0m ２ / g or more or 11.5m ２ It is preferable that the amount is 16.0 m or more. ２ / g or less, 14.0m ２ / g or less or 13.0m ２ It is preferable that the amount be less than or equal to 9.0 m ２ / g or more 16.0m ２ / g or less, 11.0m ２ / g or more 14.0m ２ / g or less, or 11.5m ２ / g or more 13.0m ２ One example is that it should be less than or equal to / g.

[0107] The second zirconia powder used in the mixing process (hereinafter also referred to as "second powder," and together with the first powder, also referred to as "raw material powder") contains stabilizing elements, and the content of stabilizing elements in terms of oxides (amount of stabilizing elements) is preferably 5.8 mol% or more, and more preferably 6.0 mol% or more or 6.3 mol% or more. Having such an amount of stabilizing elements makes it less likely for monoclinic zirconia to be included in the crystalline phase of the zirconia powder particles contained in the second powder, resulting in a proportion of monoclinic zirconia of 2% or less, further 1% or less, further 0.5% or less, and further 0% of monoclinic zirconia, i.e., the crystalline phase consists of at least one of tetragonal and cubic crystals. The amount of stabilizing elements in the second powder is preferably 8.0 mol% or less, 7.5 mol% or less, or 6.8 mol% or less, and can be 5.8 mol% to 8.0 mol%, 6.0 mol% to 7.5 mol%, or 6.3 mol% to 6.8 mol%.

[0108] The second powder may consist of a crystalline phase of at least one of tetragonal and cubic crystals and a monoclinic crystal, but it is preferable that the crystalline phase does not contain monoclinic zirconia, and it is preferable that the monoclinic phase ratio is 0%. The monoclinic phase ratio of the second powder should be 0% or more, and examples include greater than 0% or 0.1% or more, as well as 2% or less, 1% or less, or 0.5% or less. The monoclinic phase ratio of the second powder may be 0% or more and 1% or less, or 0% or more and 0.5% or less.

[0109] The second powder has a BET specific surface area difference of 7.5 m² compared to the first powder. ２ It has a BET specific surface area of ​​0 / g or less. The BET specific surface areas of the first powder and the second powder are the same (the difference from the BET specific surface area of ​​one powder is 0 m²). ２ It is also acceptable if the values ​​are different (the difference from the BET specific surface area of ​​one powder is 0 m²). ２ (More than / g) is preferable.

[0110] The difference between the BET specific surface area of ​​the second powder and the BET specific surface area of ​​the first powder is 5.0 m². ２ / g or less, 4.5m ２ / g or less or 3.5m ２ It is preferable that it be less than or equal to / g, and also 0m ２ / g or more, 0m ２ / g over 0.3m ２ / g or more, 1.0m ２ / g or more or 2.0m ２ It is preferable that the amount is 1 / g or more. The difference in BET specific surface area of ​​the second powder from that of the first powder is 0 m². ２ / g or more 7.5m ２ / g or less, 0m ２ / g or more 5.0m ２ / g or less, or 0m ２ / g or more 3.5m ２ One characteristic is that the BET specific surface area is less than or equal to 1 / g. Furthermore, if the BET specific surface areas of the first and second powders are different, the difference between the BET specific surface area of ​​the second powder and that of the first powder must be 0 m². ２ / g over 7.5m ２ / g or less, 0.3m ２ / g or more 7.0m ２ / g or less, 1.0m ２ / g or more 5.0m ２ / g or less, or 2.0m ２ / g or more 3.5m ２ One characteristic is that the BET specific surface area is less than or equal to / g.

[0111] Furthermore, it is preferable that the BET specific surface area of ​​the second powder is smaller than that of the first powder. This facilitates efficient pore removal from the early to late stages of sintering, making it easier to obtain a zirconia sintered body with higher transparency. For example, the BET specific surface area of ​​the second powder can be 9.0 m². ２ / g or more, 10.0m ２ / g or more or 11.5m ２ It must be 17.0 m or more. ２ / g or less, 14.0m ２ / g or less or 13.0m ２ One example is that it is less than / g, and 9.0m ２ / g or more 17.0m ２ / g or less, 10.0m ２ / g or more 14.0m ２ / g or less, or 11.5m ２ / g or more 13.0m ２ One example is that it should be less than or equal to / g.

[0112] Examples of the amounts of auxiliary elements in the raw material powder include 200 ppm by mass or less, 100 ppm by mass or less, 50 ppm by mass or less, or 10 ppm by mass or less, respectively. When the powder of this embodiment contains auxiliary elements, examples of the amounts of auxiliary elements include greater than 0 ppm by mass or 1 ppm by mass or more. Examples of the amounts of auxiliary elements in the raw material powder include 0 ppm by mass or more and 200 ppm by mass or less, 0 ppm by mass or more and 100 ppm by mass or less, or 0 ppm by mass or more and 10 ppm by mass or less, and furthermore, greater than 0 ppm by mass and 200 ppm by mass or less, greater than 0 ppm by mass and 100 ppm by mass or less, or 1 ppm by mass or more and 10 ppm by mass or less.

[0113] The average particle size of the raw material powder is preferably about the same as that of the powder in this embodiment, and may be 0.30 μm or more, 0.35 μm or more, or 0.40 μm or more, or 0.60 μm or less, 0.55 μm or less, or 0.50 μm or less. For example, it may be 0.30 μm or more and 0.60 μm or less, 0.35 μm or more and 0.55 μm or less, or 0.40 μm or more and 0.50 μm or less.

[0114] The raw material powders preferably have a particle size distribution similar to that of the powders in this embodiment, and the ratio of D90 [μm] to D10 [μm] (D90 / D10) is 1.5 or more or 1.6 or more, and also 2.0 or less or 1.8 or less, and also 1.5 to 2.0 or 1.6 to 1.8.

[0115] In the mixing process, the raw material powders are mixed. The mixing method can be any method that allows the raw material powders to be mixed uniformly, and at least one of dry mixing or wet mixing can be exemplified, with wet mixing being preferable and mixing in an aqueous solvent being more preferable. A mixing method is preferred in which a slurry containing the first powder and a slurry containing the second powder are mixed, as this makes it easier for the raw material powders to be mixed uniformly.

[0116] The mixing ratio of the raw material powders can be adjusted as appropriate depending on the amount of stabilizing elements in the target powder. Examples of mass ratios of the first powder to the second powder include 1% by mass:99% by mass to 99% by mass:1% by mass, 20% by mass:80% by mass to 80% by mass:20% by mass, or 35% by mass:65% by mass to 65% by mass:35% by mass, or 45% by mass:55% by mass to 55% by mass:45% by mass.

[0117] In order to fine-tune the amount of stabilizing elements in the resulting powder, three or more types of zirconia powders with different amounts of stabilizing elements, or four or more types, or six or fewer types, or five or fewer types may be mixed during the mixing process.

[0118] In the mixing step, an auxiliary element source and a coloring element source may be further mixed. The auxiliary element source is a compound containing an auxiliary element, and may be at least one of the oxides and precursors of the auxiliary element, or an oxide of the auxiliary element. The coloring element source is a compound containing a coloring element, and may be at least one of the oxides and precursors of the coloring element, or an oxide of the coloring element. The amount of the auxiliary element source and the coloring element source mixed should be such that the desired color tone of the zirconia sintered body is achieved, and may be the same amount as the amount of the auxiliary element and coloring element described above.

[0119] In the mixing process, in addition to mixing at least one of the auxiliary element source and the coloring element source (hereinafter also referred to as "auxiliary element source, etc."), or instead of mixing the auxiliary element source, etc., zirconia containing at least one of the auxiliary element and the coloring element may be provided.

[0120] The manufacturing method of this embodiment may include a drying step after the mixing step in which the zirconia powder is dried. The drying method can be any method that can remove components that are physically adsorbed onto the zirconia powder, such as moisture, and examples include exposure to air and a temperature of 80°C to 120°C. The drying time can be appropriately adjusted depending on the amount of zirconia powder to be dried and the characteristics of the dryer, but examples include 30 minutes to 5 hours.

[0121] The manufacturing method of this embodiment may include a granulation step after the mixing step (or drying step) in which the zirconia powder is granulated. The granulation can be any method that results in a powder in which the powder particles are slowly aggregated, and spray granulation is an example. In the granulation step, a mixture of the powder of this embodiment and a binder may be granulated. The inclusion of a binder improves the shape retention of the molded article obtained by molding the granular powder. The binder included in the granular powder can be a known one used for molding ceramics, and an organic binder is preferred. Examples of organic binders include the organic binders mentioned above.

[0122] [Method for producing raw material powder] The first method for producing the powder may be any method for producing zirconia powder that yields powder composed of M particles, but a preferred method is a method for producing zirconia powder that includes a powder calcination step, in which a composition (hereinafter also referred to as "sol composition") containing zirconia sol and a stabilizing element source, wherein the content of the stabilizing element in terms of oxide is 3.5 mol% or less, is heat-treated at a holding temperature of 1190°C or less to obtain calcined powder, and a powder grinding step, in which the calcined powder is ground for 7.0 hours or less.

[0123] Zirconia sol is a sol in which zirconium dioxide is hydrated and crosslinked, and is preferably a zirconia sol obtained by at least one of a hydrothermal synthesis method and a hydrolysis method, and more preferably a zirconia sol obtained by a hydrolysis method. Zirconia sol can be produced by known methods, for example, a zirconia sol produced by the production method disclosed in Japanese Patent Application Publication No. 2021-088501.

[0124] The stabilizing element source can be any compound containing a stabilizing element, and may include one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, nitrates, and acetates of the stabilizing element, one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, and chlorides of the stabilizing element, or one or more selected from the group consisting of oxides, hydroxides, and chlorides of the stabilizing element. For example, as a yttrium source, yttrium oxide (yttria; Y) ２ O ３ ), yttrium hydroxide (Y(OH) ３ ) and yttrium chloride (YCl ３ One or more selected from the group, at least one of yttrium oxide and yttrium chloride, or yttrium oxide.

[0125] The sol composition may contain zirconia sol and a stabilizing element source, and examples include a composition comprising zirconia sol, a stabilizing element source, and a solvent, as well as an aqueous solution containing zirconia sol and a stabilizing element source.

[0126] The type and amount of stabilizing elements in the sol composition may be the same as those in the first powder described above. Examples of stabilizing element amounts include 3.5 mol% or less, 3.0 mol% or less, 2.8 mol% or less, or 2.6 mol% or less, as well as 1.0 mol% or more, 1.5 mol% or more, or 2.0 mol% or more. Furthermore, examples include 1.0 mol% to 3.5 mol%, 1.5 mol% to 3.0 mol%, or 2.0 mol% to 2.6 mol%.

[0127] The powder calcination process involves obtaining calcined powder by calcining the sol composition. Preferably, the calcined powder is obtained by drying the sol composition to obtain dried powder, and then heat-treating the dried powder.

[0128] Drying in the powder calcination process can be carried out by any method that removes residual moisture from the sol composition, and examples include drying in an air atmosphere or by heat treatment at 160°C to 200°C.

[0129] In the powder calcination and powder grinding processes, the calcined powder obtained by heat-treating the sol composition at a holding temperature of 1190°C or lower is ground for 7.0 hours or less. This heat treatment and grinding process yields a first powder that can undergo a volume change suitable for pore removal in industrial sintering. One possible reason why the first powder obtained by this manufacturing method can undergo a volume change suitable for pore removal in industrial sintering is as follows: Conventionally, the conditions for heat treatment (powder calcination) and grinding were set to control the BET specific surface area of ​​the obtained powder. However, it is presumed that even if the BET specific surface area is the same, the surface characteristics of the powder particles will differ depending on the heat treatment and grinding conditions. Furthermore, it is presumed that by performing heat treatment at the holding temperature and grinding for the grinding time described above, a surface state and crystalline phase can be obtained that can appropriately delay the sintering shrinkage in the presence of the second powder. Conversely, excessive grinding, such as grinding for a long time, can increase the activity of the powder particle surface too much. As a result, pore removal becomes difficult during sintering in the presence of the second powder.

[0130] The heat treatment holding temperature (powder calcination temperature) is 1190°C or lower, preferably 1150°C or lower, 1130°C or lower, 1100°C or lower, or 1050°C or lower, and preferably 950°C or higher, 1000°C or higher, or 1020°C or higher, and examples include 950°C or higher and 1190°C or lower, 1000°C or higher and 1150°C or lower, or 1020°C or higher and 1050°C or lower. By setting the powder calcination temperature to 1190°C or lower, the surface of the resulting powder particles reaches an appropriate active state.

[0131] The atmosphere for heat treatment is an atmospheric atmosphere, preferably a circulating atmospheric atmosphere.

[0132] The holding time at the holding temperature (hereinafter also referred to as the "powder calcination time") is preferably 3.0 hours or more or 5.0 hours or more, and may be 10.0 hours or less or 8.0 hours or less. It is believed that a powder calcination time of 3.0 hours or more results in the surface of the resulting calcined powder having an appropriate level of activity, and that by grinding according to the grinding time described later, zirconia powder composed of M particles can be obtained.

[0133] In the powder grinding process, the calcined powder is ground. Grinding yields zirconia powder particles with a moderately active surface.

[0134] The grinding process is preferably wet grinding, ball mill grinding, and more preferably ball mill grinding using zirconia balls with a diameter of 0.1 mm to 5 mm as the grinding medium.

[0135] The grinding time is 7.0 hours or less, preferably 6.5 hours or less, or 6.2 hours or less. Grinding for more than 7.0 hours results in a higher monoclinic phase fraction, but the surface activity of the powder particles after grinding tends to become excessively high. Even if the powder obtained in this way is subjected to industrial sintering, a zirconia sintered body with a total light transmittance of 50% or more cannot be obtained. The grinding time may be 1.0 hour or more, 3.0 hours or more, or 5.0 hours or more, and examples include 1.0 hour to 7.0 hours, 3.0 hours to 6.5 hours, or 5.0 hours to 6.2 hours.

[0136] The second method for producing the powder may be any method for producing zirconia powder that yields a powder composed of TC particles, but a preferred method is a powder calcination step which includes a powder calcination step in which a composition containing zirconia sol and a stabilizing element source, having a stabilizing element content of 5.8 mol% or more in terms of oxides, is heat-treated at a holding temperature of 1150°C or lower for 3 hours or more to obtain calcined powder, and a powder grinding step in which the calcined powder is ground for 7.0 hours or less.

[0137] The second powder can be manufactured using the same method as the first powder, except that the holding temperature (powder calcination temperature) and holding time (powder calcination time) during heat treatment are as shown below, and the amount of stabilizing elements in the aqueous solution containing zirconia sol and stabilizing element source is the same as the amount of stabilizing elements in the second powder described above.

[0138] The heat treatment holding temperature (powder calcination temperature) is 1150°C or lower, preferably 1130°C or lower, 1100°C or lower, or 1050°C or lower, and preferably 950°C or higher, 1000°C or higher, or 1020°C or higher, and includes temperatures of 950°C or higher and 1150°C or lower, 1000°C or higher and 1130°C or lower, or 1020°C or higher and 1050°C or lower.

[0139] The holding time at the holding temperature in the powder calcination process (powder calcination time) is 3.0 hours or more, preferably 5.0 hours or more, and can also be 10.0 hours or less, or 8.0 hours or less. The longer the powder calcination time, the more the monoclinic phase ratio tends to decrease. When this is 3.0 hours or more, the monoclinic phase is substantially eliminated from the crystalline phase, and the surface activity of the zirconia powder particles is appropriately suppressed. The grinding time is 7.0 hours or less, preferably 6.5 hours or less, or 6.2 hours or less. In grinding that exceeds 7.0 hours, the surface activity of the powder particles after grinding tends to become excessively high. Even if the powder obtained in this way is subjected to industrial sintering, a zirconia sintered body with a total light transmittance of 50% or more cannot be obtained. The grinding time may be 1.0 hour or more, 3.0 hours or more, or 5.0 hours or more, and can be 1.0 hour or more and 7.0 hours or less, 3.0 hours or more and 6.5 hours or less, or 5.0 hours or more and 6.2 hours or less.

[0140] [Method for Manufacturing Zirconia Molded Bodies] The powder of this embodiment can be used as a precursor for a molded body, and a zirconia molded body can be obtained by molding it. Preferred methods for manufacturing zirconia molded bodies using the powder of this embodiment include a molding step of obtaining a molded body by dry molding the powder of this embodiment, and a further method for manufacturing zirconia molded bodies includes a molding step of obtaining a molded body by dry molding zirconia powder that contains stabilizing elements, the content of stabilizing elements in terms of oxides is 5.6 mol% or more and less than 7.0 mol%, the crystalline phase contains monoclinic crystals, and the monoclinic phase ratio is 2.5% or more and 20.0% or less. The molding method can be any method that can obtain a molded body of the desired shape, and can be molded by one or more known ceramic molding methods, such as press molding, cold isostatic pressing, slip casting, and injection molding. However, in order to make the molding method suitable for the industrial manufacturing method of zirconia calcined bodies for dental prostheses, the molding method in the molding step is preferably dry molding, and more preferably press molding. The pressure used for press forming is 15 MPa or higher, or 30 MPa or higher, and also 150 MPa or lower, or 100 MPa or lower. For example, it can be between 15 MPa and 150 MPa, or between 30 MPa and 100 MPa. The higher the pressure used in forming, the higher the density of the molded product tends to be.

[0141] It is more preferable to perform cold isostatic pressing (CIP) treatment after press forming. The pressure for CIP treatment is 90 MPa or more or 150 MPa or more, and also 400 MPa or less or 300 MPa or less, for example, 90 MPa to 400 MPa or 150 MPa to 300 MPa.

[0142] The zirconia molded body obtained from the powder of this embodiment (hereinafter also referred to as "this molded body") is a zirconia molded body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%. For example, it is a zirconia molded body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the crystalline phase contains monoclinic crystals, and the monoclinic phase ratio is 2.5% or more and 20.0% or less. Furthermore, it is a zirconia molded body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the crystalline phase contains monoclinic crystals, the monoclinic phase ratio is 2.5% or more and 20.0% or less, and the BET specific surface area is 9.0 m². ２ / g or more 16.0m ２ Examples include zirconia molded articles with a content of less than / g.

[0143] The physical properties of this molded body, such as the type of stabilizing element, the amount of stabilizing element, the monoclinic phase ratio, and the BET specific surface area, may be the same as those of the powder in this embodiment.

[0144] The density of this molded body is 2.80 g / cm³. ３ Above, 2.95g / cm ３ or more, or 3.00 g / cm³ ３ The above is true, and also 3.50 g / cm³. ３ Below, 3.40g / cm ３ Below, 3.30g / cm ３ Below, 3.20g / cm ３ The following or 3.15 g / cm³ ３ The following are some examples:

[0145] The shape of the molded body can be at least one selected from the group consisting of cubic, rectangular, polyhedral, columnar, cylindrical, disc-shaped, and approximately spherical shapes. Furthermore, taking into account thermal shrinkage due to sintering, the shape can be similar to the intended calcined or sintered body, such as the shape of a dental prosthesis.

[0146] The molded article exhibits a shrinkage rate (hereinafter also referred to as "calcination shrinkage rate") of 0.10% or more, 0.30% or more, or 0.40% or more when heat-treated in an air atmosphere at a heating rate of 50°C / hour, a holding temperature of 1000°C, and a holding time of 1 hour, and may also exhibit a shrinkage rate of 1.00% or less, 0.90% or less, or 0.80% or less. Examples include 0.10% to 1.00%, 0.20% to 0.90%, or 0.40% to 0.80%.

[0147] The calcination shrinkage rate can be calculated using the following formula: Calcination shrinkage rate [%] = {(D3 - D4) / D3} × 100 In the above formula, D3 is the diameter of the molded body before calcination [mm], and D4 is the diameter of the molded body after calcination [mm]. The diameters of the molded body and calcined body can be determined by measuring 3 ± 1 points with a caliper and taking the average value of the obtained values. This molded body can be used as a precursor for a zirconia sintered body suitable for dental prosthetic materials for the incisal ends of anterior teeth. Whether it is subjected to industrial sintering, or calcined and then subjected to industrial sintering, a zirconia sintered body with translucency and transparency suitable for dental prosthetic materials for the incisal ends of anterior teeth can be obtained.

[0148] [Method for producing a calcined zirconia body] At least one of the powder and the molded body of this embodiment, and furthermore the molded body, can be used as a precursor for a calcined body, and by calcining these, a calcined zirconia body can be produced. A preferred method for producing a zirconia calcined body includes a molding step of dry molding a zirconia powder containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the crystalline phase contains monoclinic crystals, and the monoclinic phase ratio is 2.5% or more and 20.0% or less, in order to obtain a molded body, and a calcination step of calcining the molded body to obtain a calcined body, or a calcination step of calcining a zirconia molded body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the crystalline phase contains monoclinic crystals, and the monoclinic phase ratio is 2.5% or more and 20.0% or less, in order to obtain a calcined body.

[0149] This manufacturing method makes it possible to obtain calcined zirconia that can serve as a precursor suitable for sintered bodies used for cut ends, even when applied to industrial sintering.

[0150] Calcination can be any heat treatment performed at a temperature below the temperature at which zirconia densification progresses, and is preferably performed in an atmospheric environment. Preferred calcination conditions include the following: Calcination atmosphere: Oxidizing atmosphere, preferably atmospheric atmosphere Holding temperature (calcination temperature): 900°C or higher, 950°C or higher, or 1000°C or higher, and 1150°C or lower, or 1100°C or lower Holding time (calcination time: holding time at calcination temperature): 0.5 hours or higher, or 1 hour or higher, and 5 hours or lower, or 3 hours or lower

[0151] If the molded article contains a binder, the process may include a step to remove the binder, a so-called degreasing step, prior to the calcination step. The method for removing the binder is arbitrary, but examples include heat treatment in an air atmosphere at 400°C or higher but less than 900°C.

[0152] The calcined body obtained from the powder or molded body of this embodiment (hereinafter also referred to as "this calcined body") is a zirconia calcined body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%. For example, a zirconia calcined body containing stabilizing elements, wherein the content of stabilizing elements on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, and which has a shrinkage rate of 1500°C or more when heated in an air atmosphere at a heating rate of 600°C / hour to a holding temperature of 1500°C and held at the holding temperature for 2 hours, is an example of such a zirconia calcined body.

[0153] The type and content of the stabilizing elements in this calcined body may be the same as those in the powder of this embodiment.

[0154] The shape of the calcined body can be at least one selected from the group consisting of cubic, rectangular, polyhedral, columnar, cylindrical, disc-shaped, and approximately spherical shapes. Furthermore, taking into account thermal shrinkage due to sintering, the shape can be similar to that of the intended sintered body, such as a dental prosthesis.

[0155] The calcined body is preferably heated in an atmospheric environment at a heating rate of 600°C / hour to a holding temperature of 1500°C, and held at that temperature for 2 hours. The shrinkage rate (hereinafter also referred to as "sintering shrinkage rate") is preferably 15% or more, 17% or more, or 18% or more, and preferably 25% or less, 20% or less, or 19% or less. Examples of the sintering shrinkage rate of the calcined body include 15% to 25%, 17% to 20%, or 17% to 19%.

[0156] The sintering shrinkage rate can be calculated using the following formula: Sintering shrinkage rate [%] = {(D5 - D6) / D5} × 100 In the above formula, D5 is the diameter of the calcined body before sintering [mm], and D6 is the diameter of the calcined body after sintering [mm]. The diameter of the calcined body can be determined by measuring 3 ± 1 points with a caliper and taking the average of the obtained values.

[0157] The calcined body is preferably hard enough to prevent chipping during processing prior to sintering, and its Vickers hardness can be 70 HV or less, 60 HV or less, 55 HV or less, 50 HV or less, or 45 HV or less, or 35 HV or more, or 40 HV or more. Examples of Vickers hardness for the calcined body include 35 HV to 70 HV, 35 HV to 60 HV, 35 HV to 55 HV, 40 HV to 50 HV, or 45 HV to 50 HV. The calcined body yields a zirconia sintered body with high light transmittance. When sintered at atmospheric pressure with a heating rate of 10°C / min, a holding temperature of 1500°C, and a holding time of 2 hours, the total light transmittance is preferably 50% or more, 51% or more, 53% or more, or 55% or more, and also preferably 62% or less, 60% or less, 59% or less, or 58% or less, and more preferably 50% or more and 62% or less, 53% or more and 59% or less, or 55% or more and 58% or less.

[0158] [Method for Manufacturing Zirconia Sintered Body] One or more selected from the group consisting of the powder of this embodiment, the molded body, and the calcined body, and furthermore, the calcined body can be used as a precursor for the sintered body. By sintering these, a zirconia sintered body having aesthetic properties suitable for use as a sintered body for cut ends can be obtained. With the powder of this embodiment, a sintered body for cut ends can be manufactured even if the sintering is standard sintering or even industrial sintering. Therefore, the method for manufacturing the zirconia sintered body is preferably a manufacturing method that includes a sintering step by industrial sintering, and more preferably, it contains stabilizing elements, the content of stabilizing elements in terms of oxide is 5.6 mol% or more and less than 7.0 mol%, and the BET specific surface area is 9.0 m². ２ / g or more 16.0m ２ A method for producing a zirconia sintered body, comprising: a molding step of dry molding zirconia powder having a weight of 1 / g or less, having a monoclinic crystal phase, and a monoclinic phase ratio of 2.5% to 20.0% or less to obtain a molded body; a calcination step of calcining the molded body to obtain a calcined body; and a sintering step of heating the calcined body in an air atmosphere at a heating rate of 10°C / min or more to a holding temperature of 1200°C to 1600°C or less, and holding it at the holding temperature for 1 hour or more to sinter it; containing stabilizing elements, with a content of stabilizing elements in terms of oxides of 5.6 mol% or more and less than 7.0 mol%, and a BET specific surface area of ​​9.0 m² ２ / g or more 16.0m ２A method for producing a zirconia sintered body, comprising: a calcination step of calcining a molded body containing zirconia powder having a concentration of 1 / g or less, having a monoclinic crystal phase, and having a monoclinic phase ratio of 2.5% to 20.0%, to obtain a calcined body; and a sintering step of heating the calcined body in an air atmosphere at a heating rate of 10°C / min or more to a holding temperature of 1200°C to 1600°C, and holding it at the holding temperature for 1 hour or more to sinter it; or, One example is a method for producing a zirconia sintered body, which includes a sintering step of heating a calcined zirconia body containing stabilizing elements, wherein the content of stabilizing elements in terms of oxides is 5.6 mol% or more and less than 7.0 mol%, and which is heated in an air atmosphere at a heating rate of 600°C / hour to a holding temperature of 1500°C, and which has a shrinkage rate of 15% or more and 25% or less when held at the holding temperature for 2 hours, and then heating it in an air atmosphere at a heating rate of 10°C / min or more to a holding temperature of 1200°C or more and 1600°C or less, and holding it at the holding temperature for 1 hour or more.

[0159] According to this embodiment, even when applied to such industrial sintering and industrial manufacturing, a zirconia sintered body suitable for cut end sintered bodies can be obtained.

[0160] The calcined body used in the sintering process can be any calcined body, and can be shaped into any desired form by processing with CAD / CAM, which makes it easier to obtain zirconia sintered bodies of any desired shape.

[0161] In the sintering process, one or more sintering methods selected from the group of known ceramic sintering methods, such as atmospheric pressure sintering, pressure sintering, and vacuum sintering, can be applied. However, the powder of this embodiment can be made into a sintered body suitable for incisal ends even without applying sintering methods that promote pore removal, such as atmospheric pressure sintering in an oxidizing atmosphere with an oxygen concentration of more than 50%, or vacuum atmosphere and pressure sintering. Since it is widely applied in the manufacture of dental prosthetic materials, the sintering method is preferably atmospheric pressure sintering, more preferably atmospheric pressure sintering only, that is, a sintering method that does not use pressure sintering or vacuum sintering, and especially preferably standard sintering, and even more preferably industrial sintering. By sintering only at atmospheric pressure, a zirconia sintered body can be obtained as an atmospheric pressure sintered body.

[0162] In this embodiment, sintering is particularly preferably atmospheric pressure sintering in an atmospheric environment, as it is suitable for the pore removal mechanism in the sintering of the powder. Furthermore, the sintering is characterized by a holding time (sintering time) at the holding temperature (sintering temperature) of 7 hours or less, preferably 5 hours or less, and more preferably 3 hours or less. In addition, sintering may be performed by raising the temperature to the sintering temperature at different heating rates.

[0163] The following conditions are examples of preferred sintering conditions: Sintering method: atmospheric pressure sintering Sintering atmosphere: oxidizing atmosphere with an oxygen concentration of 45% or less, and also atmospheric atmosphere Holding temperature: 1200°C or higher, 1500°C or higher, or 1550°C or higher, and 1650°C or lower, 1620°C or lower, or 1600°C or lower Holding time: 1 hour or higher, or 2 hours or higher, 5 hours or lower, or 4 hours or lower Heating rate: 5°C / min or higher, or 10°C / min or higher, and 25°C / min or lower, or 15°C / min or lower

[0164] One or more selected from the group consisting of the powder, the molded body, and the calcined body of this embodiment, and furthermore, the calcined body can be made into a sintered body suitable for a cut edge not only by industrial manufacturing methods but also by high-speed sintering. As a high-speed sintering suitable for one or more selected from the group consisting of the powder, the molded body, and the calcined body of this embodiment, for example, a method for manufacturing a zirconia sintered body can be mentioned, which includes a step of sintering one or more selected from the group consisting of the powder, the molded body, and the calcined body of this embodiment, and furthermore, at least one of the powder and the calcined body of this embodiment, and furthermore, the calcined body, under the following sintering conditions. <Sintering Conditions> Sintering Method: Atmospheric pressure sintering atmosphere: Air atmosphere Holding temperature: 1500°C or higher or 1550°C or higher, and 1650°C or lower or 1620°C or lower Holding time: 5 minutes or more, 8 minutes or more, or 15 minutes or more, and less than 1 hour or 45 minutes or lower Heating rate: (Heating rate from room temperature to 1100°C) 150°C / min or higher or 200°C / min or higher, and 300°C / min or lower or 280°C / min or lower (Heating rate from 1100°C to holding temperature) 1°C / min or higher, 3°C / min or higher, or 8°C / min or higher, and 20°C / min or lower or 15°C / min or lower

[0165] The method for manufacturing a zirconia sintered body in this embodiment may include a processing step of processing a calcined zirconia body prior to sintering. This allows for the production of a sintered body of any shape. The processing can be any known processing method, such as CAD / CAM processing.

[0166] Examples of zirconia sintered bodies obtained from the powder, molded body, or calcined body of this embodiment (hereinafter also referred to as "this sintered body") include, for example, a zirconia sintered body containing a stabilizing element, wherein the content of the stabilizing element on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, and further, a zirconia sintered body containing a stabilizing element, wherein the content of the stabilizing element on an oxide basis is 5.6 mol% or more and less than 7.0 mol%, the total light transmittance to a D65 light source is 50% or more, and the ratio of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light at wavelengths of 400 nm to 700 nm on a sample thickness of 1 ± 0.1 mm is 1.5% or more. Such a zirconia sintered body can be used as a sintered body for cut ends.

[0167] The content of stabilizing elements in oxide terms (amount of stabilizing elements) of the sintered body is preferably 5.6 mol% or more and less than 7.0 mol%. The amount of stabilizing elements of the sintered body is preferably 5.8 mol% or more, 5.9 mol% or more, or 6.0 mol% or more, and also preferably 6.9 mol% or less, 6.6 mol% or less, 6.4 mol% or less, or 6.3 mol% or less. Examples of the amount of stabilizing elements of the sintered body include 5.8 mol% or more and 6.9 mol% or less, 5.9 mol% or more and 6.6 mol% or less, 6.0 mol% or more and 6.4 mol% or less, or 6.0 mol% or more and 6.3 mol% or less.

[0168] The sintered body has a sample thickness of 1 ± 0.1 mm and a total light transmittance (total light transmittance) of 50% or more to a D65 light source. Having such a total light transmittance allows the sintered body to exhibit light transmittance equivalent to that of the incisal edge of an anterior tooth. The total light transmittance of the sintered body is preferably 50% or more, 50.5% or more, 51% or more, 53% or more, or 55% or more, and also preferably 62% or less, 60% or less, or 59% or less. Examples of total light transmittance of the sintered body include 50% or more and 60% or less, 51% or more and 60% or less, or 55% or more and 59% or less.

[0169] The sintered body has a sample thickness of 1 ± 0.1 mm, and the ratio of the integrated value of linear transmitted light to the total integrated value of diffusely transmitted light at wavelengths of 400 nm to 700 nm (PT / TT ratio) is preferably 1.5% or more, 2.0% or more, 2.5% or more, or 3.5% or more. Having such a PT / TT ratio results in transparency suitable for dental prosthetic materials for the incisal edges of anterior teeth. The PT / TT ratio can also be 8.0% or less, 7.0% or less, or 6.0% or less, and examples include 1.5% to 8.0%, 2.0% to 7.0%, 2.5% to 6.0%, or 3.5% to 5.5%. By combining the PT / TT ratio with the above-mentioned total light transmittance, a zirconia sintered body with aesthetic properties suitable for dental prosthetic materials for the incisal edges of anterior teeth is obtained.

[0170] The sintered body only needs to have mechanical strength suitable for use as a dental prosthesis, particularly for the incisal portion of anterior teeth. For example, the three-point bending strength of the sintered body is preferably 400 MPa or more, 450 MPa or more, or 500 MPa or more. Other examples of three-point bending strength include 700 MPa or less, 650 MPa or less, or 600 MPa or less, as well as 400 MPa to 700 MPa, 450 MPa to 650 MPa, or 500 MPa to 600 MPa.

[0171] The sintered body is preferably a sintered body obtained by atmospheric pressure sintering, i.e., a sintered body obtained by atmospheric pressure sintering.

[0172] The contents of this disclosure will be described in detail below with reference to examples and comparative examples. However, this disclosure is not limited to the examples.

[0173] (Compositional Analysis) The composition of the composition was measured by ICP analysis.

[0174] (BET specific surface area) The BET specific surface area was measured using an automatic specific surface area measuring device (device name: Tristar II 3020, manufactured by Shimadzu Corporation) in accordance with JIS R 1626, under the following conditions, using the BET multi-point method (5 points).

[0175] Adsorption medium: N ２Adsorption temperature: -196°C Pretreatment conditions: Degassing at 250°C for 1 hour or more in an air atmosphere

[0176] (Crystal phase, monoclinic phase fraction, and tetragonal and cubic phase fractions) The crystalline phase was identified by XRD measurement using an X-ray diffractometer (instrument name: Ultima IV, manufactured by RIGAKU Corporation) under the following conditions. Radiation source: CuKα line (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ = 26° to 33°, 72° to 76° Acceleration voltage / current: 40kV / 40mA Divergence longitudinal limiting slit: 10 mm Divergence / incident slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm Crystal phase identification and calculation of area intensity of each crystal plane were performed by smoothing and background removal processing using the analysis program attached to the X-ray diffractometer (program name: Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation), and then profile fitting of the XRD pattern after processing was performed using a divided pseudo-Voigt function.

[0177] The M phase ratio and T+C phase ratio were determined from the XRD pattern of the calcined body of this embodiment using the above formula, assuming that the zirconia crystal phase consists of three types: monoclinic, tetragonal, and cubic.

[0178] (Cryslite size) The crystallite sizes of the tetragonal and cubic crystals, and the crystallite size of the monoclinic crystal, were determined from the main XRD peak and the monoclinic XRD peak obtained by the XRD measurements described above, using the above-mentioned equations (3) and (4).

[0179] (Average particle size and D90 / D10) The average particle size was determined by measuring the volume particle size distribution of a powder sample using a wet method with a general-purpose instrument (e.g., MT3300EXII, Microtrac-Bell). From the obtained volume particle size frequency curve, the values ​​for 10% particle size (D10), 50% particle size (D50), and 90% particle size (D90) were determined. D90 / D10 was calculated from the 90% particle size value relative to the 10% particle size, and the particle size corresponding to D50 was taken as the average particle size. The volume particle size distribution was measured using the wet method with a slurry pH of 4.5 ± 1.5.

[0180] The sample used for measurement was a slurry prepared by dispersing powder, from which slow aggregation had been removed by ultrasonic treatment, in pure water.

[0181] (Molding shrinkage rate) The molding shrinkage rate was determined by filling a cylindrical mold with a diameter of 25 mm with 4 g of powder sample, then press molding at a molding pressure of 98 MPa and CIP treatment at a pressure of 196 MPa, and using the following formula.

[0182] Molding shrinkage rate [%] = {(D1 - D2) / D1} × 100 In the above formula, D1 is the diameter of the mold (25 mm), and D2 is the diameter of the molded body after CIP treatment [mm]. The diameter of the molded body can be determined by measuring three points with calipers and taking the average of the obtained values.

[0183] (Calculated shrinkage rate) The calcined shrinkage rate was determined using a molded body obtained by the same method as for measuring the molding shrinkage rate, from the shrinkage rates before and after heat treatment in an air atmosphere with a heating rate of 50°C / hour, a holding temperature of 1000°C, and a holding time of 1 hour, using the following formula.

[0184] Calcination shrinkage rate [%] = {(D3 - D4) / D3} × 100 In the above formula, D3 is the diameter of the molded body before calcination [mm], and D4 is the diameter of the molded body after calcination [mm]. The diameter of the molded body can be determined by measuring three points with calipers and taking the average of the obtained values.

[0185] (Sintering shrinkage rate) The sintering shrinkage rate was determined using a calcined body obtained by the same method as for measuring the calcination shrinkage rate. The body was heated in an air atmosphere at a heating rate of 600°C / hour (=10°C / min) to a holding temperature of 1500°C, and the shrinkage rate before and after holding at this temperature for 2 hours was calculated using the following formula.

[0186] Sintering shrinkage rate [%] = {(D5 - D6) / D5} × 100 In the above formula, D5 is the diameter of the calcined body before sintering [mm], and D6 is the diameter of the calcined body after sintering [mm]. The diameter of the calcined body was determined by measuring three points with a caliper and taking the average value of the obtained values.

[0187] (Total Light Transmittance) Total light transmittance was measured using a haze meter (device name: NDH4000, manufactured by Nippon Denshoku Co., Ltd.) with a D65 light source, in accordance with the method compliant with JIS K 7361-1. The measurement sample was a disc-shaped sintered body with a thickness of 1.0 ± 0.1 mm, which had been polished on both sides to a surface roughness Ra ≤ 0.02 μm.

[0188] (PT / TT ratio) The PT / TT ratio was determined using a general UV-VIS spectrophotometer (device name: V-650, manufactured by JASCO Corporation) equipped with a halogen lamp as the light source. It was calculated as the percentage [%] of the integrated value of linear transmitted light to the integrated value of the total transmittance of linear transmitted light and diffuse transmitted light of a sample with a thickness of 1.0 ± 0.1 mm at measurement wavelengths of 400 nm to 700 nm.

[0189] For the measurement sample, a disc-shaped sintered body with a sample thickness of 1.0 ± 0.1 mm and a surface roughness Ra ≤ 0.02 μm on both sides was used.

[0190] Synthesis Example 1 (Synthesis of the First Powder) To the aqueous solution of hydrated zirconia sol obtained by hydrolyzing an aqueous solution of zirconium oxychloride, yttrium oxide (Y) was added to each solution to obtain the amount of yttrium shown in Table 1. ２ O ３ The following was added and mixed: After mixing, the resulting mixed aqueous solution was dried in an air atmosphere at 180°C to remove moisture, and the dried powder was recovered. The dried powder was heat-treated in an air atmosphere at the holding temperature (powder calcination temperature) and holding time (powder calcination time) shown in Table 1 to obtain yttrium-containing zirconia calcined powder.

[0191]

[0192] The recovered calcined zirconia powder was mixed with pure water and wet-ground for 1 to 6 hours using 2 mm diameter zirconia beads as the grinding medium to obtain a slurry containing zirconia powder (any of powders A1 to A11) composed of M particles, as shown in Table 2. These slurry samples were then used as the respective powder slurries. The evaluation results of the obtained zirconia powders are shown in the table below.

[0193]

[0194] Synthesis Example 2 (Synthesis of the Second Powder) Yttrium oxide was added to and mixed with an aqueous solution of hydrated zirconia sol obtained by hydrolyzing an aqueous solution of zirconium oxychloride in the amounts of yttrium shown in Table 3. After mixing, the resulting mixed aqueous solution was dried in an air atmosphere at 180°C to remove moisture, and the dried powder was recovered. The dried powder was heat-treated in an air atmosphere at the holding temperature (powder calcination temperature) shown in Table 3 for 6 hours to recover calcined zirconia powder containing yttrium.

[0195]

[0196] The recovered calcined zirconia powder was mixed with pure water and wet-mixed for 6 hours using zirconia beads with a diameter of 2 mm as a grinding medium to obtain a slurry containing zirconia powder (powder B1 to B10) composed of TC particles, which was then used as each powder slurry.

[0197] The results are shown in the table below.

[0198]

[0199] In each of the Examples 1 to 15, the first powder slurry was added to the second powder slurry, which was being stirred, to obtain the yttrium content described in Table 5. After mixing, the mixture was dried in an air atmosphere at 105°C to obtain the zirconia powder (zirconia powder composition) of each example.

[0200] The results are shown in Table 5.

[0201]

[0202] Comparative Example 1: Zirconia powder for this comparative example was obtained in the same manner as in Example 15, except that powder A5 and powder B8 were mixed so that the yttrium content was 7.0 mol%.

[0203] Comparative Example 2: Zirconia powder for this comparative example was obtained in the same manner as in Example 15, except that powder A5 and powder B1 were mixed so that the yttrium content was 6.0 mol%.

[0204] Comparative Example 3 Powder A8 was used as the first powder. Furthermore, a slurry containing yttrium-containing zirconia powder with a yttrium content of 6.5 mol% was obtained using the same method as for powder B1, except that the powder calcination temperature was set to 1185°C, and this was designated as the second powder slurry. This powder had a T+C phase ratio of 100%, an average crystallite diameter of 360 Å, and a BET specific surface area of ​​8.8 m². ２ It was / g.

[0205] The difference in yttria content between the first powder slurry and the second powder slurry was 3.5 mol%. After mixing the two slurries to achieve a yttria content of 6.0 mol%, the mixture was dried in an air atmosphere to obtain yttrium-containing zirconia powder with a yttrium content of 6.0 mol%.

[0206] Comparative Example 4 Yttrium-containing zirconia powder was obtained by a method similar to Example 4 of Patent Document 4. That is, yttria (Y) was added to the hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium oxychloride solution so that the yttrium content was 2.5 mol%. ２ O ３ The mixture was dried. Then, it was heat-treated in an air atmosphere at 1160°C for 2 hours to obtain a calcined powder with a matrix of yttrium-containing zirconia (yttrium-stabilized zirconia) having a yttrium content of 2.5 mol%. The obtained calcined powder and pure water were mixed and ground in a ball mill for 7 hours using 2 mm diameter beads as the grinding medium. The result was a powder with a yttrium content of 2.5 mol%, a monoclinic phase ratio of 71%, and a BET specific surface area of ​​14.4 m². ２ A slurry containing zirconia powder at a concentration of / g was obtained and designated as the first powder slurry.

[0207] Except for mixing yttrium to a yttrium content of 5.5 mol% and grinding for 10 hours, the same method as for the first powder slurry was used, resulting in a yttrium content of 5.5 mol% and a BET specific surface area of ​​9.7 m². ２ A slurry containing zirconia powder at a concentration of 1 / g was obtained and designated as the second powder slurry. The BET specific surface area of ​​the powder contained in the first powder slurry was 2.2 m² greater than the BET specific surface area of ​​the powder contained in the second powder slurry. ２ The amount was large.

[0208] The first powder slurry was added to and mixed with the second powder slurry, which was being stirred, until the yttrium content reached 5.2 mol%. Afterward, it was dried in an air-circulating atmosphere at 110°C, resulting in a yttrium content of 5.2 mol% and a BET specific surface area of ​​10.2 m². ２ A zirconia powder with a concentration of 1 / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias (stabilized zirconia powders contained in the two slurries) in the powder composition was 3.0 mol%.

[0209] Comparative Example 5 Zirconia powder was obtained in the same manner as in Example 1 of Patent Document 3. Specifically, a hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium oxychloride solution was mixed with yttrium oxide and dried, then heat-treated at 1160°C for 2 hours in an air atmosphere to obtain yttrium-containing zirconia powder with a yttrium content of 2.5 mol%. The obtained yttrium-containing zirconia powder, α-alumina with an average particle size of 0.3 μm, and pure water were mixed to obtain a slurry containing aluminum and yttrium-containing zirconia powder, with an aluminum content of 0.05 mass% and a yttrium content of 2.5 mol%, which was used as the first powder slurry. This powder had a monoclinic phase fraction of 82%, an average crystallite size of 196 Å, and a BET specific surface area of ​​10.0 m². ２ It was / g.

[0210] Furthermore, a slurry containing aluminum and yttrium-containing zirconia powder was obtained by the same method as the first powder slurry, except that the yttrium content was set to 8.5 mol%, resulting in an aluminum content of 0.05 mass% and an yttria content of 8.5 mol%, and this was designated as the second powder slurry. This powder had a T+C phase ratio of 100%, an average crystallite size of 397 Å, and a BET specific surface area of ​​11.3 m². ２ It was / g.

[0211] The difference in yttria content between the first powder slurry and the second powder slurry was 6.0 mol%. After mixing the two slurries to achieve a yttria content of 5.2 mol%, the mixture was dried in an air atmosphere to obtain an aluminum-containing yttrium-containing zirconia powder with an aluminum content of 0.05 mass% and a yttrium content of 5.2 mol%.

[0212] Comparative Example 6: Yttrium chloride was added and mixed to an aqueous solution of hydrated zirconia sol obtained by hydrolyzing an aqueous solution of zirconium oxychloride so that the yttrium content was 6.0 mol%. After mixing, the resulting mixed aqueous solution was dried in an air atmosphere at 180°C to remove moisture, and the dried powder was recovered. The dried powder was heat-treated in an air atmosphere at a holding temperature of 1120°C for 2 hours to recover calcined zirconia powder containing yttrium.

[0213] The recovered calcined zirconia powder was washed with distilled water and dried at 110°C. α-alumina was then added to achieve an aluminum content of 0.05% by mass. After adding α-alumina, distilled water was added to the calcined zirconia powder to achieve a solid content of 45%. The mixture was then wet-milled for 17 hours using a ball mill with 2 mm diameter zirconia beads as the grinding medium to obtain a zirconia powder slurry. A polyacrylic acid-based organic binder was added by mass to the slurry and spray-dried by dropping it with hot air at 180°C to obtain the zirconia powder (granular powder) of this comparative example. The obtained zirconia powder had an average granule size of 48 μm and a bulk density of 26 g / cm³. ３ That was the case.

[0214] Comparative Example 7: Yttrium oxide was added and mixed to an aqueous solution of hydrated zirconia sol obtained by hydrolyzing an aqueous solution of zirconium oxychloride so that the yttrium content was 6.0 mol%. After mixing, the resulting mixed aqueous solution was dried in an air atmosphere at 180°C to remove moisture, and the dried powder was recovered. The dried powder was heat-treated in an air atmosphere at a holding temperature of 1120°C for 6 hours to recover calcined zirconia powder containing yttrium.

[0215] A zirconia powder slurry was obtained by mixing the recovered calcined zirconia powder with pure water and wet grinding it for 6 hours using 2 mm diameter zirconia beads as the grinding medium.

[0216] The obtained slurry was dried in an air atmosphere at 180°C to remove moisture, and the dried powder was recovered. The dried powder was heat-treated in an air atmosphere at a holding temperature (powder calcination temperature) of 1120°C for 6 hours to recover yttrium-containing zirconia calcined powder, which was used as the zirconia powder for this comparative example.

[0217] Comparative Example 8: A zirconia powder slurry of this comparative example was obtained in the same manner as in Comparative Example 7, except that yttrium oxide was added and mixed so that the yttrium content was 6.0 mol%, the dried powder was heat-treated in an air atmosphere at a holding temperature of 1120°C for 6 hours, and α-alumina was added to the dried powder and then wet-ground so that the aluminum content was 0.025 mass%.

[0218]

[0219] Measurement Example 1 <Preparation of Calcined and Sintered Bodies> 3 g of the powder from the example or comparative example was placed in a mold with a diameter of 25 mm, and press-molded at a molding pressure of 98 MPa for shrinkage rate and 49 MPa for permeability. After that, a molded body was obtained by CIP treatment at a pressure of 196 MPa.

[0220] The obtained molded bodies were calcined in an air atmosphere, at a calcination temperature of 1000°C, a heating rate of 50°C / hour, and a holding time of 1 hour to obtain calcined zirconia bodies.

[0221] The evaluation results for the powder, molded body, and calcined body of the example are shown in the table below.

[0222]

[0223] The Vickers hardness of the obtained zirconia calcined bodies was 44 HV (Example 1), 43 HV (Example 3), 44 HV (Example 4), 53 HV (Example 5), 50 HV (Example 6), 53 HV (Example 7), 41 HV (Example 9), 42 HV (Example 11), 40 HV (Example 12), and 43 HV (Example 13), with all Vickers hardnesses being between 40 HV and 55 HV. From this, it was confirmed that the zirconia calcined bodies of the examples have appropriate workability.

[0224] The resulting calcined material was placed in an alumina sagger and sintered at atmospheric pressure under the following conditions to obtain a zirconia sintered body. Sintering method: Atmospheric pressure sintering atmosphere: Air atmosphere Heating rate: 10°C / min Holding temperature: 1500°C Holding time: 2 hours

[0225] The evaluation results of the obtained sintered bodies are shown in the table below.

[0226]

[0227] The zirconia sintered bodies in the examples all had a total light transmittance of 50.5% or more, and even 52% or more, and a PT / TT ratio of 1.5% or more, and even 2.0% or more, confirming that they were zirconia sintered bodies with high light transmittance and high transparency required for anterior tooth incisal tip applications. On the other hand, the zirconia sintered bodies in the comparative examples all had low PT / TT ratios and did not have the transparency required for incisal tip sintered bodies. Furthermore, the sintered bodies obtained from the zirconia powders of Comparative Examples 1 to 4 and 6 to 8, whose stabilizing element content, BET specific surface area, or monoclinic phase fraction were outside the scope of this disclosure, all had low light transmittance and transparency. In Comparative Example 5, while the total light transmittance exceeded 50%, the PT / TT ratio was 0.70, indicating low transparency. It was confirmed that if these zirconia powders were provided for industrial production, incisal tip sintered bodies could not be obtained.

[0228] Furthermore, when the zirconia powder of Comparative Example 8 was sintered using the same method except that the heating rate was 100°C / hour (= 1.67°C / min), the total light transmittance of the resulting zirconia sintered body was 51.0%, confirming that a zirconia sintered body with high light transmittance can be obtained.

[0229] Furthermore, the three-point bending strengths of the zirconia sintered bodies of Examples 2 to 7 were 537 MPa (Example 2), 512 MPa (Example 3), 506 MPa (Example 4), 496 MPa (Example 5), 466 MPa (Example 6), and 606 MPa (Example 7), all of which were 450 MPa or higher, and even 500 MPa or higher. This confirmed that these zirconia sintered bodies possess mechanical properties suitable for use as dental prosthetic materials for the incisal edges of anterior teeth.

[0230] Measurement Example 2 <Confirmation of Reproducibility> Using the zirconia powders from Examples and Comparative Examples 6 and 8, three zirconia sintered bodies were prepared using the same method as in Measurement Example 1. The total light transmittance of the obtained zirconia sintered bodies was measured, and the average value (average total light transmittance) and standard deviation were calculated. The results are shown in the table below.

[0231]

[0232] The zirconia sintered bodies in the examples showed a small standard deviation of total light transmittance, confirming that even when industrial manufacturing is applied to the zirconia powder in the examples, sintered bodies for cut edges can be obtained with high reproducibility. In contrast, the zirconia sintered bodies obtained from the zirconia powder of the comparative examples showed large variations in total light transmittance, confirming that it is difficult to obtain zirconia sintered bodies of stable quality when industrial manufacturing is applied.

[0233] Measurement Example 3 <Preparation of Calcined and Sintered Bodies> Molded bodies and calcined bodies were obtained in the same manner as in Measurement Example 1, except that the powders of Examples 1, 3, and 5, and Comparative Example 5 were used. The obtained calcined bodies were placed in alumina saggers and sintered at atmospheric pressure under the following conditions to obtain a zirconia sintered body. Sintering method: Atmospheric pressure sintering atmosphere: Air atmosphere Holding temperature: 1550°C Holding time: 30 minutes Heating rate: (From room temperature to 1100°C) 250°C / min (From 1100°C to holding temperature) 10°C / min Cooling rate: (From holding temperature to 900°C) 50°C / min

[0234] The evaluation results of the obtained sintered bodies are shown in the table below.

[0235]

[0236] As can be seen from the table above, even with high-speed sintering, which involves sintering in a short time of less than 100 minutes, it was confirmed that sintered bodies with high light transmittance exceeding 50%, and even 50.5%, can be obtained.

[0237] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2025-038739, filed on March 11, 2025, are incorporated herein by reference as part of the disclosure of the specification.

Claims

1. Contains stabilizing elements, with an oxide content of stabilizing elements of 5.6 mol% or more and less than 7.0 mol%, and a BET specific surface area of ​​9.0 m². ２ / g or more 16.0m ２ Zirconia powder characterized by having a density of less than or equal to / g, containing monoclinic crystals in its crystalline phase, and having a monoclinic phase ratio of 2.5% to 20.0%.

2. The zirconia powder according to claim 1, wherein the stabilizing element is one or more selected from the group consisting of yttrium (Y), calcium (Ca), magnesium (Mg), niobium (Nb), europium (Eu), gadolinium (Gd), ytterbium (Yb), praseodymium (Pr), lanthanum (La), scandium (Sc), erbium (Er), and terbium (Tb).

3. The zirconia powder according to claim 1 or 2, wherein the aluminum content is 200 ppm by mass or less.

4. The zirconia powder according to any one of claims 1 to 3, comprising zirconia powder particles with different amounts of stabilizing elements.

5. Zirconia powder according to any one of claims 1 to 3, comprising: zirconia powder particles containing at least one of tetragonal and cubic crystals, with a monoclinic zirconia content of 2% or less; and zirconia powder particles containing at least one of tetragonal and cubic crystals in the crystalline phase, with a monoclinic zirconia content of more than 2%.

6. The zirconia powder according to any one of claims 1 to 5, wherein the crystallite size of monoclinic zirconia is 1.00 or less relative to the crystallite sizes of tetragonal zirconia and cubic zirconia.

7. Zirconia powder according to any one of claims 1 to 6, wherein the ratio of D90 [μm] to D10 [μm] is 1.5 or more.

8. Zirconia powder according to any one of claims 1 to 7, wherein the shrinkage rate after filling 4 g of the powder into a cylindrical mold with a diameter of 25 mm, press molding at a molding pressure of 98 MPa, and cold isostatic pressing (CIP) at a pressure of 196 MPa is 2.00% or more and 3.00% or less.

9. Zirconia powder according to any one of claims 1 to 8, wherein the total light transmittance is 50% or more when 3 g of the powder is filled into a cylindrical mold with a diameter of 25 mm, press-formed at a molding pressure of 49 MPa and subjected to CIP treatment at a pressure of 196 MPa, calcined in an air atmosphere at a calcination temperature of 1000°C, a heating rate of 50°C / hour, and a holding time of 1 hour, and sintered at atmospheric pressure at a heating rate of 10°C / min, a holding temperature of 1500°C, and a holding time of 2 hours.

10. Contains stabilizing elements, with a stabilizing element content of 3.5 mol% or less in terms of oxides, and a BET specific surface area of ​​9.0 m². ２ / g or more 16.0m ２ A first zirconia powder having a concentration of less than or equal to 1 / g and a monoclinic phase ratio of more than 2%, and a stabilizing element containing a stabilizing element whose oxide content is 5.8 mol% or more, a monoclinic phase ratio of 2% or less, and a difference of 7.5 m² from the BET specific surface area of ​​the first zirconia powder. ２ A method for producing zirconia powder, comprising the step of mixing a second zirconia powder having a BET specific surface area of ​​0.5 / g or less with 1.

11. The manufacturing method according to claim 10, wherein the first zirconia powder is a zirconia powder obtained by a manufacturing method comprising: a powder calcination step of heat-treating a composition containing a zirconia sol and a stabilizing element source, wherein the content of the stabilizing element in terms of oxide is 3.5 mol% or less, at a holding temperature of 1190°C or less to obtain calcined powder; and a powder grinding step of grinding the calcined powder for 7.0 hours or less.

12. The manufacturing method according to claim 10 or 11, wherein the second zirconia powder is a zirconia powder obtained by a manufacturing method comprising: a powder calcination step of heat-treating a composition containing a zirconia sol and a stabilizing element source, wherein the content of the stabilizing element in terms of oxide is 5.8 mol% or more, at a holding temperature of 1150°C or lower for 3 hours or more to obtain calcined powder; and a powder grinding step of grinding the calcined powder for 7.0 hours or less.

13. A method for producing a zirconia molded article using the zirconia powder described in any one of claims 1 to 9.

14. A method for producing a calcined zirconia body using the zirconia powder described in any one of claims 1 to 9.

15. The manufacturing method according to claim 14, wherein the zirconia calcined body contains a stabilizing element, the amount of the stabilizing element in terms of oxides being 5.6 mol% or more and less than 7.0 mol%, and the shrinkage rate when heated to a holding temperature of 1500°C in an air atmosphere at a heating rate of 600°C / hour and held at the holding temperature for 2 hours is 15% or more and 25% or less.

16. A method for producing a zirconia sintered body using the zirconia powder described in any one of claims 1 to 9.

17. The manufacturing method according to claim 16, wherein the zirconia sintered body contains a stabilizing element, the content of the stabilizing element in terms of oxide is 5.6 mol% or more and less than 7.0 mol%, the total light transmittance to a D65 light source is 50% or more and the ratio of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light at wavelengths of 400 nm to 700 nm is 1.5% or more for a sample thickness of 1 ± 0.1 mm.

18. A calcined zirconia body containing stabilizing elements, wherein the amount of stabilizing elements in terms of oxides is 5.6 mol% or more and less than 7.0 mol%, and when heated in an air atmosphere at a heating rate of 600°C / hour to a holding temperature of 1500°C, the shrinkage rate when held at the holding temperature for 2 hours is 15% or more and 25% or less.

19. A zirconia sintered body containing stabilizing elements, wherein the content of stabilizing elements in terms of oxides is 5.6 mol% or more and less than 7.0 mol%, the sample thickness is 1 ± 0.1 mm, the total light transmittance to a D65 light source is 50% or more, and the ratio of the integrated value of linear transmitted light to the total integrated value of linear transmitted light and diffuse transmitted light at wavelengths of 400 nm to 700 nm is 1.5% or more, with a sample thickness of 1 ± 0.1 mm.

20. A method for producing a zirconia sintered body, comprising the step of sintering the zirconia calcined body described in claim 18 under the following sintering conditions. <Sintering conditions> Sintering method: atmospheric pressure sintering atmosphere: atmospheric atmosphere Holding temperature: 1500°C or more and 1650°C or less Holding time: 5 minutes or more and less than 1 hour Heating rate: (Heating rate from room temperature to 1100°C) 150°C / min or more and 300°C / min or less (Heating rate from 1100°C to holding temperature) 1°C / min or more and 20°C / min or less

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