Zirconia composition and calcined body

Abstract

To provide a zirconia composition that is not easily affected by temperature variations in a firing furnace during preparation of a calcined body, and to provide a zirconia composition and a calcined body that can maintain the translucency of a sintered body while shortening the firing time. The composition contains zirconia powder with a monoclinic content of 55% or more and a stabilizer capable of suppressing the phase transition of zirconia. The zirconia particles and stabilizer particles have average particle sizes of 0.06 μm to 0.115 μm. At least a portion of the stabilizer is not solid-dissolved in the zirconia.

Description

Related Applications

[0001] This disclosure is based on a claim of priority from Japanese Patent Application No. 2016-183129 (filed September 20, 2016), the entire contents of which are incorporated herein by reference. [Technical Field]

[0002] The present disclosure relates to compositions containing primarily zirconia (zirconium(IV) oxide; ZrO2). The present disclosure also relates to calcined bodies of zirconia. [Background technology]

[0003] Zirconia is a compound that undergoes phase transitions between multiple crystal systems. Therefore, partially stabilized zirconia (PSZ) and fully stabilized zirconia, which are formed by dissolving a stabilizer such as yttria (yttrium oxide; YO) in zirconia to suppress the phase transition, are used in various fields. For example, Patent Document 1 discloses a partially stabilized zirconia sintered body for use in dental materials.

[0004] The translucent zirconia sintered body described in Patent Document 1 is produced by sintering a press-molded body of zirconia powder at 1450°C, at a heating rate of 600°C / hr, and for a holding time of 2 hours. The zirconia powder contains more than 4.0 mol% and not more than 6.5 mol% of yttria and less than 0.1 wt% of alumina, and has a BET specific surface area of ​​8 to 15 m. 2 / g, the average particle size is 0.40 to 0.50 μm, and the total ratio of tetragonal and cubic crystals contained in the crystals is 80% or more. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2015 / 098765A1 Summary of the Invention [Problem to be solved by the invention]

[0006] Because zirconia sintered bodies obtained by sintering zirconia particles (powder) usually have high strength, it is not easy to directly machine the zirconia sintered body into a desired shape. Therefore, the zirconia sintered body is sometimes formed by firing (hereinafter referred to as "calcination") a pressed compact of zirconia powder (including a compact subjected to CIP (Cold Isostatic Pressing) treatment) at a temperature below sintering to form a block of calcined bodies. In this case, the block of calcined zirconia body is shaped into the desired shape by cutting or other processing, and the shaped calcined body is fired at a temperature equal to or higher than the sintering temperature to produce a zirconia sintered body having the desired shape.

[0007] When pressed from zirconia powder, the compact shrinks depending on the firing temperature. For example, the pressed compact shrinks by about 1% before it becomes a calcined body, and by about 20% before it becomes a sintered body. Therefore, the calcined body is formed to be larger than the dimensions of the final sintered body, taking these shrinkage rates into consideration. For example, the size of the formed calcined body is determined based on a coefficient calculated by subtracting the shrinkage rate from the shrinkage rate from the press compact to the sintered body.

[0008] Therefore, when a plurality of press-molded bodies are fired in one firing furnace to produce a plurality of calcined bodies (block bodies), there is a need for a zirconia composition in which the shrinkage rate between the plurality of products during the process from the press-molded bodies to the calcined bodies is less affected by the temperature difference (temperature unevenness) that occurs in the firing furnace during the production of the calcined bodies.

[0009] Furthermore, in the manufacturing method of a zirconia sintered body described in Patent Document 1, the holding time at the maximum temperature is two hours. Such a long firing time reduces production efficiency and increases energy costs. Furthermore, for example, when a dental prosthesis is made from a zirconia sintered body, the patient cannot receive treatment with the prosthesis on the same day as the consultation and must return to the hospital on another day to receive treatment with the prosthesis. On the other hand, with the zirconia powder described in Patent Document 1, shortening the holding time at the maximum temperature causes the sintered body to become cloudy and the translucency of the sintered body to decrease.

[0010] Therefore, there is a need for a zirconia composition and a calcined body that can maintain the translucency of the sintered body while shortening the firing time. [Means for solving the problem]

[0011] According to a first aspect of the present disclosure, there is provided a composition containing zirconia powder in which 55% or more of the zirconia powder is monoclinic, and a stabilizer capable of suppressing the phase transition of zirconia. 7 At least a part of the stabilizer is not solid-dissolved in the zirconia. The composition has not been fired above 700°C.

[0012] According to a second aspect of the present disclosure, there is provided a calcined body containing zirconia having a monoclinic content of 55% or more and a stabilizer capable of suppressing the phase transition of the zirconia. At least a portion of the stabilizer is not solid-dissolved in the zirconia. The calcined body is produced by firing a press-molded body of the composition according to the first aspect at 800°C to 1200°C. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to suppress variations in the shrinkage rate from the composition to the calcined body that may occur due to temperature variations in the firing furnace. This makes it possible to increase product yield and improve production efficiency. Furthermore, it is possible to mold the sintered body with higher precision.

[0014] According to the present disclosure, a highly translucent zirconia sintered body can be produced while shortening the manufacturing time of the sintered body. This makes it possible to improve the production efficiency of products and reduce energy costs. When the zirconia sintered body is applied to a dental prosthesis, the time burden on the patient can be reduced.

[0015] The composition of the present disclosure may have at least one of the above-mentioned advantages of suppressing variations in shrinkage rate and shortening production time. [Brief explanation of the drawings]

[0016] [Figure 1] 1 shows an X-ray diffraction pattern of the calcined body produced in Reference Example 5-2. [Figure 2] 1 is an X-ray diffraction pattern of the calcined body produced in Reference Example 6-2. [Figure 3] 4 is an X-ray diffraction pattern of the calcined body produced in Comparative Example 4-2. [Figure 4] 1 is a graph showing the change in shrinkage rate relative to firing temperature. [Figure 5] 1 is a graph showing changes in light transmittance with respect to firing temperature. [Figure 6] Electron microscope photograph of granules of Reference Example 3-2. [Figure 7] Electron microscope photograph of constituent particles of Reference Example 3-2. [Figure 8] Electron microscope photograph of granules of Comparative Example 1. [Figure 9] Electron microscope photograph of constituent particles of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of each of the above aspects will be described below.

[0018] According to a preferred embodiment of the first aspect, the BET specific surface area is 7.5 m 2 / g~25m 2 / g.

[0019] According to a preferred embodiment of the first aspect, 80% or more of the zirconia is monoclinic.

[0020] According to a preferred mode of the first aspect, the average particle size is 0.10 μm to 0.14 μm.

[0021] According to a preferred embodiment of the first aspect, the average particle size is less than 0.13 μm.

[0022] According to a preferred embodiment of the first aspect, the stabilizer is yttria.

[0023] According to a preferred embodiment of the first aspect, the composition contains 3 mol % to 7.5 mol % of yttria relative to the total moles of zirconia and yttria.

[0024] According to a preferred embodiment of the first aspect, the composition has an yttria peak in the X-ray diffraction pattern.

[0025] According to a preferred embodiment of the first aspect, f calculated based on the following equation 1: y is more than 1%.

[0026] According to a preferred embodiment of the first aspect, f y is less than 15%.

[0027] According to a preferred embodiment of the first aspect, the content of yttria in the composition is 3 mol % or more and less than 4.5 mol %. y is 2% or more.

[0028] According to a preferred embodiment of the first aspect, the content of yttria in the composition is 4.5 mol % or more and less than 5.8 mol %. y is more than 3%.

[0029] According to a preferred embodiment of the first aspect, the content of yttria in the composition is 5.8 mol % or more and 7.5 mol % or less. y is more than 4%.

[0030] According to a preferred embodiment of the first aspect, the composition is not fired at 700° C. or higher.

[0031] According to a preferred embodiment of the second aspect, the density of the calcined body is 2.7 g / cm 3 ~3.6g / cm 3 is.

[0032] According to a preferred mode of the second aspect, the calcined body has a bending strength of 15 MPa to 70 MPa.

[0033] According to a preferred embodiment of the second aspect, 80% or more of the zirconia is monoclinic.

[0034] According to a preferred embodiment of the second aspect, the stabilizer is yttria, and a peak of yttria is present in the X-ray diffraction pattern of the calcined body.

[0035] According to a preferred embodiment of the second aspect, f calculated based on the following equation 1: y is more than 1%.

[0036] According to a preferred embodiment of the second aspect, f y is less than 15%.

[0037] According to a preferred embodiment of the second aspect, the content of yttria in the composition is 3 mol % or more and less than 4.5 mol %. y is 2% or more.

[0038] According to a preferred embodiment of the second aspect, the content of yttria in the composition is 4.5 mol % or more and less than 5.8 mol %. y is more than 3%.

[0039] According to a preferred embodiment of the second aspect, the content of yttria in the composition is 5.8 mol % or more and 7.5 mol % or less. y is more than 4%.

[0040] According to a preferred embodiment of the second and third aspects, when a first translucency of a first sintered body produced by firing the calcined body at 1550°C for 30 minutes is compared with a second translucency of a second sintered body produced by firing the calcined body at 1550°C for 120 minutes, the first translucency is 85% or more of the second translucency.

[0041] A composition of the present disclosure will be described as Embodiment 1. The composition can serve as a precursor (intermediate product) of a zirconia sintered body and a calcined body.

[0042] The composition contains zirconia powder and a stabilizer capable of suppressing the phase transition of zirconia. The stabilizer is preferably capable of forming partially stabilized zirconia. Examples of stabilizers include oxides such as calcium oxide (CaO), magnesium oxide (MgO), yttria, cerium oxide (CeO2), and scandium oxide (Sc2O3). The stabilizer content in the composition, calcined body, and sintered body can be measured, for example, by inductively coupled plasma (ICP) emission spectroscopy, X-ray fluorescence analysis, or the like.

[0043] In the composition, the stabilizer is preferably present so that at least a portion of the zirconia crystals are monoclinic. It is preferable that at least a portion of the stabilizer is not solid-dissolved in zirconia. The fact that a portion of the stabilizer is not solid-dissolved in zirconia can be confirmed, for example, by X-ray diffraction (XRD) patterns. If a peak attributable to the stabilizer is observed in the XRD pattern of the composition, this indicates that some stabilizer is present in the composition that is not solid-dissolved in zirconia. If the entire amount of stabilizer is solid-dissolved, essentially no peak attributable to the stabilizer is observed in the XRD pattern. However, depending on conditions such as the crystalline state of the stabilizer, even if no stabilizer peak is present in the XRD pattern, the stabilizer may not be solid-dissolved in zirconia. If the zirconia has a predominant crystalline system of tetragonal and / or cubic, and no stabilizer peak is present in the XRD pattern, it is considered that most, essentially all, of the stabilizer is solid-dissolved in zirconia.

[0044] In the composition of the present disclosure, the stabilizer does not necessarily have to be entirely dissolved in the zirconia.

[0045] In the present disclosure, the term "the stabilizer is solid-dissolved" refers to, for example, the elements (atoms) contained in the stabilizer being solid-dissolved in zirconia.

[0046] From the viewpoint of the strength and translucency of a sintered body produced from the composition of the present disclosure, the stabilizer is preferably yttria. The yttria content is preferably 3 mol% or more, more preferably 3.5 mol% or more, and even more preferably 4 mol% or more, based on the total moles of zirconia and yttria. When the yttria content is 3 mol% or more, the translucency of the sintered body can be increased. Furthermore, the yttria content is preferably 7.5 mol% or less, more preferably 7 mol% or less, more preferably 6.5 mol% or less, and even more preferably 6 mol% or less, based on the total moles of zirconia and yttria. When the yttria content is 7.5 mol% or less, a decrease in the strength of the sintered body can be suppressed.

[0047] The abundance rate f of yttria that is not dissolved in zirconia (hereinafter referred to as "undissolved yttria") in the composition y can be calculated based on the following equation 1: The abundance ratio of undissolved yttria f y is preferably greater than 0%, more preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. y The upper limit of f depends on the content of yttria in the composition. When the content of yttria is 7.5 mol% or less based on the total moles of zirconia and yttria, y For example, when the yttria content is 3.5 mol% to 4.5 mol%, f y When the yttria content is 5 mol% to 6 mol%, f y When the yttria content is 5.5 mol% to 6.5 mol%, f y can be 11% or less.

[0048] In the composition, when the content of yttria is 3 mol% or more and less than 4.5 mol%, f yis preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and even more preferably 5% or more. When the yttria content is 4.5 mol% or more and less than 5.8 mol%, f y is preferably 3% or more, more preferably 4% or more, more preferably 5% or more, more preferably 6% or more, and even more preferably 7% or more. When the yttria content is 5.8 mol% or more and 7.5 mol% or less, f y is preferably 4% or more, more preferably 5% or more, even more preferably 6% or more, still more preferably 7% or more, and even more preferably 8% or more.

[0049]

number

[0050] In number 1, I y (111) indicates the peak intensity of the (111) plane of yttria at around 2θ=29° in the XRD pattern using CuKα radiation. m (111) and I m (11-1) indicates the peak intensity of the (111) and (11-1) planes of the monoclinic system of zirconia. t (111) indicates the peak intensity of the (111) plane of the tetragonal crystal system of zirconia. c (111) indicates the peak intensity of the (111) plane of the cubic crystal system of zirconia.

[0051] The above number 1 is I y By substituting other peaks in place of (111), it can also be applied to calculate the undissolved fraction of stabilizers other than yttria.

[0052] The main crystal system of the zirconia in the composition is preferably monoclinic. In the composition, the proportion of monoclinic zirconia in the composition, f mis preferably 20% or more, preferably 30% or more, preferably 40% or more, preferably 50% or more, preferably 55% or more, preferably 60% or more, more preferably 70% or more, more preferably 80% or more, more preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more, based on the total amount of monoclinic, tetragonal, and cubic crystals. m can be calculated from the following equation 2 based on the XRD peak using CuKα radiation. The meaning of each symbol in equation 2 is the same as in equation 1. The main crystal system in the composition may contribute to increasing the shrinkage temperature and shortening the sintering time.

[0053] In the composition of the present disclosure, tetragonal and cubic peaks may be substantially undetectable. That is, the monoclinic fraction f m can be set to 100%.

[0054]

number

[0055] When a calcined body is produced by firing a press-molded body of the composition at 800°C or higher and 1000°C or lower, the shrinkage rate from the press-molded body to the calcined body is preferably 1% or less relative to the dimension in one direction of the press-molded body. Furthermore, when a calcined body is produced by firing a press-molded body of the composition at a temperature higher than 1000°C and lower than 1200°C, the shrinkage rate from the press-molded body to the calcined body is preferably 5% or less relative to the dimension in one direction of the press-molded body. However, the press-molded body referred to here is a body obtained by firing a zirconia powder at 300 kg / cm. 2 1700kg / cm for a molded body pressed at a pressure of 2 It has been further treated with CIP.

[0056] The composition may be in the form of a powder. The powder may be an aggregate of granules. The granules are aggregates of primary particles and / or secondary particles formed by agglomeration of the primary particles.

[0057] Granules are aggregates (aggregates) of particles. When a composition is in the form of granules, the expressions "particles" and "particles constituting granules" are used below to distinguish between particles and granules. The composition of the present disclosure does not have to have a granular form. When the composition is not in the form of granules, "particles constituting granules" refers to particles in a powder. "Particles constituting granules" include zirconia particles and stabilizer particles.

[0058] As used herein, "primary particles" refer to the smallest unit of spherical particles. For example, primary particles refer to spherical bodies that are not bonded to each other and appear separable under an electron microscope. As used herein, "secondary particles" refer to particles that are aggregates of particles that appear to be primary particles under an electron microscope. Secondary particles include aggregates in which primary particles are attached in a disintegrable manner, and aggregates in which primary particles are fused together in an inseparable manner and appear as a single particle. In electron microscope images, secondary particles often do not appear as spherical bodies but have irregular shapes.

[0059] It is preferable that the particles constituting the granules are mainly primary particles. For example, when visually checking an electron microscope image, it is preferable that the number of primary particles is greater than the number of secondary particles. For example, when visually checking an electron microscope image, it is preferable that 50% or more, preferably 70% or more, and more preferably 80% or more of the primary particles (including primary particles constituting secondary particles) are particles that do not constitute secondary particles. Since secondary particles usually have an irregular shape, if there are a large number of secondary particles, the circularity of the granules, which will be described later, will decrease.

[0060] The average particle size of the particles constituting the granules, as measured by a laser diffraction / scattering particle size distribution measurement method, is preferably 0.06 μm or more, more preferably 0.08 μm or more, more preferably 0.10 μm or more, and even more preferably 0.11 μm or more. If the particle size is less than 0.06 μm, sintering may be difficult, or even if sintering is successful, the sintered body may become cloudy. Furthermore, the average particle size is preferably 0.17 μm or less, more preferably 0.15 μm or less, more preferably 0.14 μm or less, and even more preferably 0.13 μm or less. If the particle size exceeds 0.17 μm, the speed change temperature (described below) becomes high, making the sintered body more susceptible to temperature variations in the sintering furnace. Furthermore, shortening the sintering time reduces the translucency of the sintered body. The average particle size here refers to the particle size measured without distinguishing between primary and secondary particles.

[0061] When the particles or granules are produced without undergoing a firing process, in order to further increase the translucency of the sintered body produced from the particles or granules, the average particle size of the particles constituting the granules is preferably less than 0.13 μm, more preferably 0.125 μm or less, even more preferably 0.12 μm or less, and even more preferably 0.115 μm or less.

[0062] The BET specific surface area of ​​the particles that make up the granules is 7.0 m when measured in accordance with JIS Z 8830 (2013). 2 / g or more is preferable, and 7.5m 2 / g or more is more preferable, and 8m 2 / g or more is more preferable. 2 If the BET specific surface area is less than 30 m / g, sintering will be difficult, or even if sintering is possible, the sintered body will become cloudy. 2 / g or less, and 25m 2 / g or less is more preferable, and 20m 2 / g or less is more preferable. 2If the BET specific surface area exceeds 1 / g, the temperature change temperature (described later) will be high, making the sintered body more susceptible to temperature variations in the sintering furnace. Furthermore, shortening the sintering time will result in a decrease in the translucency of the sintered body. The BET specific surface area here refers to the specific surface area measured without distinguishing between primary and secondary particles.

[0063] Of the zirconia in the zirconia composition, 50% or more, preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more can be in the form of granules.

[0064] When the zirconia composition of the present disclosure does not take the form of granules, it is sufficient that the zirconia particles constituting the powder have the above-mentioned average particle size and BET specific surface area.

[0065] The average particle size of the granules in the zirconia composition is preferably 10 μm or more, more preferably 12 μm or more, and even more preferably 14 μm or more. If the average particle size of the granules is less than 10 μm, air may be entrapped when the granules are placed in a mold, resulting in insufficient degassing during molding, and a uniform, dense molded body may not be produced. Furthermore, the granules may be ejected from gaps during molding, resulting in a molded body that does not meet the required volume. The average particle size of the granules is preferably 200 μm or less, more preferably 190 μm or less, more preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. If the average particle size of the granules exceeds 200 μm, cavities are likely to form inside the granules. Furthermore, gaps are likely to form when the granules are placed in a mold. These phenomena may result in insufficient degassing during molding, making it difficult to produce a dense molded body. Furthermore, significant shrinkage may occur during molding, making it difficult to produce a molded body of the desired size. It is preferable that 50% or more of the zirconia in the zirconia composition constitutes granules. The average particle size of the granules is preferably measured by a method that does not destroy the granules. For example, the average particle size of the granules can be measured by a vibration-type / low-tap particle size distribution measurement method or an ultrasonic vibration sieving particle size distribution measurement method (e.g., using a robot sifter manufactured by Seishin Enterprise Co., Ltd.).

[0066] It is preferable that the granules have a high sphericity. By increasing the sphericity of the granules, mixing at the interface between layers can be induced when zirconia powders of different compositions are stacked. Furthermore, when filling a mold with zirconia powder to produce a compact, a higher sphericity can increase the packing density even if the average particle size is the same. Increasing the packing density can increase the strength and translucency of the sintered body. Furthermore, even if the mold has corners, the packing of the granules into the corners can be improved.

[0067] The sphericity of granules can be expressed, for example, by the circularity based on a projected image, the angle of repose, the loose bulk density, the tight bulk density, etc.

[0068] The average circularity based on a projected image of granules in the zirconia composition is preferably 0.81 or more, more preferably 0.85 or more, even more preferably 0.90 or more, and even more preferably 0.95 or more. The circularity can be calculated as the ratio of the perimeter of a circle equal to the area of ​​the granule to the perimeter of the granule in the projected image. That is, the circularity can be calculated using the following formula. The average circularity is preferably the average circularity of 10,000 or more granules. Circularity = (perimeter of a circle equal to the area of ​​the granule) / perimeter of the granule

[0069] The angle of repose of the zirconia composition is preferably 35° or less, more preferably 32° or less, more preferably 28° or less, more preferably 26° or less, and even more preferably 24° or less. The angle of repose can be measured in accordance with JIS R9301-2-2.

[0070] The zirconia composition has a bulk density of 1.0 g / cm 3 It is preferable that the value is 1.1 g / cm or more. 3 More preferably, it is 1.2 g / cm or more. 3 More preferably, it is 1.3 g / cm or more. 3 The loose bulk density can be measured in accordance with JIS R9301-2-3.

[0071] The compacted bulk density of the zirconia composition is 1.3 g / cm 3 It is preferable that the value is 1.4 g / cm or more. 3 More preferably, it is 1.5 g / cm or more. 3 The compacted bulk density can be measured in accordance with JIS R9301-2-3.

[0072] The composition may contain additives other than zirconia and yttria, such as pigments (including colorants and fluorescent agents), binders, dispersants, antifoaming agents, alumina (Al2O3), titanium oxide (TiO2), and silica (SiO2).

[0073] Examples of additives such as colorants include oxides of at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb, and Er. Examples of fluorescent agents include Y2SiO5:Ce, Y2SiO5:Tb, (Y,Gd,Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, BaMgAl 10 O 17 :Eu and the like.

[0074] As the binder, an organic binder can be used, for example, an acrylic binder, an acrylic acid binder, a paraffin binder, a fatty acid binder, or a polyvinyl alcohol binder.

[0075] The composition of the present disclosure may be in a dry state, or may contain or be contained in a liquid. For example, the composition may be in the form of a powder, a paste, a slurry, or the like. The composition may also be in the form of a molded product having a predetermined shape (hereinafter referred to as a "first molded product").

[0076] The density of the first compact is 2.75 g / cm 3 It is preferable that the value is 2.80 g / cm or more. 3 More preferably, it is 2.85 g / cm or more. 3 More preferably, it is 2.90 g / cm or more. 3 More preferably, it is 3.00 g / cm or more. 3 It is more preferable that the density is equal to or greater than this. The density can be calculated, for example, as (mass of the first molded body) / (volume of the first molded body).

[0077] Generally, the shrinkage rate from the press-molded body to the sintered body is not constant with respect to the firing temperature. The shrinkage rate is low up to a certain temperature, but at that temperature, the shrinkage rate increases. The temperature at which this shrinkage rate changes is referred to as the "change temperature" in this specification. According to the composition of the present disclosure, the change temperature can be set to 1050°C or higher, preferably 1100°C or higher. The change temperature is set as described in the Examples below. and reference examples This can be determined by plotting the shrinkage rate against the maximum firing temperature, as shown below.

[0078] When multiple press-molded bodies are simultaneously fired in a single firing furnace to produce multiple calcined bodies (blocks) as a single lot, it is preferable for the shrinkage coefficients of the multiple press-molded bodies to vary little among the calcined bodies. If the shrinkage coefficients vary significantly, applying the same coefficient to the entire lot to determine the dimensions of the calcined bodies will result in sintered bodies that do not meet the desired dimensions. This is particularly problematic for products that require high dimensional accuracy, such as dental prostheses. Therefore, blocks with shrinkage coefficients outside the allowable range within a single lot cannot be used as products, resulting in a low yield.

[0079] The composition of the present disclosure can reduce the variation in shrinkage rate within a single lot relative to the firing temperature (e.g., approximately 1000°C) used to produce a calcined block. Typically, the maximum firing temperature used to produce a calcined body (hereinafter referred to as the "calcination temperature") is close to the temperature-varying temperature. Typically, a temperature difference (temperature unevenness) of approximately 20°C to 50°C occurs within a firing furnace at the calcination temperature. Therefore, when the temperature-varying temperature is close to the calcination temperature, the composition lot is strongly affected by this temperature unevenness. In other words, within a single lot, the calcined bodies in low-temperature areas and those in high-temperature areas will have significantly different shrinkage rates. Calcined bodies with shrinkage rates outside the allowable range cannot be used as products, resulting in a reduced yield. On the other hand, the composition of the present disclosure has a high temperature-varying temperature, which can reduce the difference between the temperature-varying temperature and the calcination temperature. Therefore, within a single lot, the difference in shrinkage rate between the calcined bodies in low-temperature areas and those in high-temperature areas can be reduced. This reduces the number of calcined bodies with shrinkage rates outside the allowable range, thereby increasing yield. It also increases the number of products that can be fired at one time, improving production efficiency. Furthermore, the composition and calcined body of the present disclosure allow for the production of final products (sintered bodies) with high dimensional accuracy for any block body within a single lot. The composition and calcined body of the present disclosure are particularly useful for producing products (e.g., dental products) that require high dimensional accuracy.

[0080] The composition and calcined body of the present disclosure have further advantages. The composition and calcined body of the present disclosure can shorten the firing time for producing a sintered body without reducing the translucency and strength of the zirconia sintered body produced. In particular, the holding time at the maximum firing temperature for producing a sintered body (hereinafter referred to as the "sintering temperature") can be shortened (short-time sintering). This can improve production efficiency and reduce manufacturing costs. Furthermore, when the composition and calcined body of the present disclosure are applied to dental products, the time from determining the dimensions of the dental product to being able to use the dental product for treatment can be shortened, thereby reducing the time burden on patients.

[0081] The composition according to the first embodiment may have at least one of the advantages related to the variable speed temperature and the short sintering time described above, but it is preferable that the composition according to the first embodiment has both advantages related to the variable speed temperature and the short sintering time.

[0082] As a second embodiment, a method for producing the composition of the present disclosure will be described.

[0083] First, zirconia and a stabilizer are mixed in a predetermined ratio to prepare a mixture (mixing step). For example, when the stabilizer is yttria, the mixing ratio can be the same as the above-mentioned yttria content. Mixing can be performed in a dry or wet manner. The composition can be pulverized to the above-mentioned average particle size and / or BET specific surface area (first pulverization step). The mixing step and the first pulverization step can be performed in the same step. The pulverization can be performed, for example, using a ball mill after dispersing the composition in a solvent such as water (dispersion step). When the steps after the firing step described below are not performed, the composition is pulverized so that the average particle size of the composition is, for example, 0.10 μm to 0.14 μm, due to the high temperature change temperature and / or short sintering time. The average particle size can be measured by a laser diffraction / scattering particle size distribution measurement method. After the mixing step and / or the first grinding step, the mixture can be dried by spray drying using a spray dryer or the like to form the composition into the granular form described above (first drying step), thereby producing the composition of the present disclosure.

[0084] When the firing step and subsequent steps described below are not performed, the average particle size of the composition in the first pulverization step is preferably less than 0.13 μm, more preferably 0.125 μm or less, more preferably 0.12 μm or less, and even more preferably 0.115 μm or less. By making the average particle size of the composition less than 0.13 μm, the light transmittance of the sintered body can be increased.

[0085] When the steps subsequent to the firing step described below are not performed, it is preferable not to include a step of firing the composition at 700°C or higher before the steps of producing the calcined body and sintered body described below, which simplifies the manufacturing process and prevents the stabilizer from becoming solid-dissolved before sintering.

[0086] It is preferable to prepare the zirconia and the stabilizer separately. For example, it is preferable that the zirconia and the stabilizer are not precipitated simultaneously (in the same process), but that the zirconia preparation step (e.g., manufacturing step) and the stabilizer preparation step (e.g., manufacturing step) are separate, independent processes. This makes it possible to prevent the stabilizer from dissolving in the zirconia during the process for producing the calcined body described below.

[0087] The following steps can be performed as desired depending on the intended use of the composition. For example, after any of the above steps, the mixture and / or composition can be fired (calcination (calcination) step). As described above, the firing conditions are preferably such that the primary crystal system of zirconia when cooled after firing is neither tetragonal nor cubic. Furthermore, the firing conditions are preferably such that at least a portion of the stabilizer does not dissolve in zirconia. For example, the firing temperature is preferably 700°C or higher, more preferably 800°C or higher. Furthermore, the firing temperature is preferably 1100°C or lower, more preferably 1000°C or lower, more preferably 980°C or lower, and even more preferably 950°C or lower. Firing can be performed in the atmosphere. It is believed that the firing step can dissolve a portion of the stabilizer in zirconia, facilitate the dissolution of the stabilizer in the sintering step, and improve the properties of the sintered body.

[0088] After any of the above steps, the composition can be dispersed in a solvent such as water to prepare a slurry, and additives such as a binder or pigment can be added to the composition (addition step). The composition can be pulverized to the above-mentioned average particle size and / or BET specific surface area (second pulverization step). The addition step and the second pulverization step can be carried out in the same process. The second pulverization step can be carried out in the same manner as the first pulverization step. After the addition step and / or the second pulverization step, the mixture can be spray-dried using a spray dryer or the like to form the composition into the above-mentioned granular form (second drying step).

[0089] The composition can be molded into a first molded body (first molding step). The molding method is not limited to a specific method, and a suitable method can be selected depending on the purpose. For example, the composition can be molded by press molding, injection molding, stereolithography, etc. Multi-stage molding may also be performed. For example, the composition may be press-molded and then further subjected to CIP treatment.

[0090] The above-mentioned additives can be added appropriately in each step.

[0091] The method for producing a composition according to the second embodiment makes it possible to produce the composition according to the first embodiment. That is, the method for producing a composition according to the second embodiment makes it possible to produce a composition that has a high temperature for changing the speed and / or that can shorten the firing time for sintering.

[0092] Zirconia powder with yttria dissolved therein is generally produced by coprecipitation and hydrolysis. In the coprecipitation and hydrolysis methods, a mixture of hydrated zirconia and yttria is produced from zirconium oxychloride and yttrium chloride in the same process, and this mixture is fired at 800°C to 900°C to produce stabilized zirconia powder with yttria (yttrium) dissolved therein. This yttria-dissolved zirconia is primarily a tetragonal and / or cubic crystal. The particle size of the resulting zirconia powder is on the order of several tens of nanometers. To use this zirconia powder as a raw material for a zirconia sintered body, the fired product is pulverized to a predetermined particle size and then granulated to produce a composition.

[0093] Compositions prepared by such coprecipitation or hydrolysis methods have a high temperature dependency of shrinkage in the temperature range in which the calcined body is prepared, and sufficient translucency of the sintered body cannot be obtained with a short firing time.

[0094] In the manufacturing method of the present disclosure, after producing zirconia (monoclinic crystal), a stabilizer (yttria) is separately mixed, and the stabilizer is essentially dissolved in the zirconia during the sintering process. This reduces the temperature dependence of the shrinkage rate in the temperature range for producing a calcined body. Furthermore, a highly translucent sintered body can be obtained even with a short sintering time.

[0095] Furthermore, in the manufacturing method of the present disclosure, if the firing step, second pulverization step, and second drying step are not performed, the manufacturing cost of the composition can be reduced by a significant time reduction. Furthermore, by diverting the equipment and time used for the second pulverization step and second drying step to the first pulverization step and first drying step, the production volume per hour can be doubled. Furthermore, omission of the second pulverization step and second drying step reduces the chance of impurities such as dust being mixed into the composition.

[0096] As a third embodiment, a zirconia calcined body according to the present disclosure will be described. The calcined body can be a precursor (intermediate product) of a zirconia sintered body. In the present disclosure, the calcined body can refer to, for example, a block of zirconia particles (powder) that is not completely sintered. In particular, the calcined body according to the present disclosure refers to a body made from the composition according to the present disclosure. The density of the calcined body is 2.7 g / cm 3 The density of the calcined body is preferably 4.0 g / cm or more. 3 It is preferable that the value is 3.8 g / cm or less. 3 More preferably, it is 3.6 g / cm or less. 3 It is more preferable that the density is not more than 1000 kJ / cm. When the density is in this range, molding can be easily carried out.

[0097] The content ratio of zirconia and stabilizer in the calcined body is the same as the content ratio in the composition before the calcined body is produced. From the viewpoint of the strength and translucency of the sintered body produced from the calcined body of the present disclosure, it is preferable that the stabilizer is yttria.

[0098] The proportion of undissolved yttria in the calcined body depends on the firing temperature during preparation of the calcined body, but is considered to be equal to or less than the proportion of undissolved yttria in the composition before preparation of the calcined body. y can be calculated based on the above equation 1. The abundance ratio of undissolved yttria in the calcined body, f y is the f of the above composition y It can be the same as:

[0099] In the calcined body, the fraction of undissolved yttria f y is preferably greater than 0%, more preferably 1% or more, more preferably 2% or more, and even more preferably 3% or more. y The upper limit of f depends on the yttria content in the calcined body. When the yttria content is 7.5 mol% or less based on the total moles of zirconia and yttria, y For example, when the yttria content is 3.5 mol% to 4.5 mol%, fy When the yttria content is 5 mol% to 6 mol%, f y When the yttria content is 5.5 mol% to 6.5 mol%, f y can be 11% or less.

[0100] In the calcined body, when the yttria content is 3 mol% or more and less than 4.5 mol%, f y is preferably 2% or more, more preferably 3% or more, even more preferably 4% or more, and even more preferably 5% or more. When the yttria content is 4.5 mol% or more and less than 5.8 mol%, f y is preferably 3% or more, more preferably 4% or more, more preferably 5% or more, more preferably 6% or more, and even more preferably 7% or more. When the yttria content is 5.8 mol% or more and 7.5 mol% or less, f y is preferably 4% or more, more preferably 5% or more, even more preferably 6% or more, still more preferably 7% or more, and even more preferably 8% or more.

[0101] The crystal system of zirconia in the calcined body depends on the firing temperature when the calcined body is produced, but the content of monoclinic crystals is thought to be equal to or less than the content of monoclinic crystals in the composition before the calcined body is produced. m is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, still more preferably 90% or more, and even more preferably 95% or more of the total amount of monoclinic, tetragonal, and cubic crystals.

[0102] The bending strength of the calcined body measured in accordance with JIS R 1601 is preferably 15 MPa or more to ensure strength that allows mechanical processing, and is preferably 70 MPa or less, more preferably 60 MPa or less, to facilitate mechanical processing.

[0103] Flexural strength can also be measured in accordance with ISO6872.

[0104] However, the size of the test piece differs from that specified in JIS R1601 or ISO 6872, and is 5 mm x 10 mm x 50 mm. The test piece's face and C-face are finished in the longitudinal direction with 600-grit sandpaper. The test piece is positioned so that the widest surface faces vertically (in the load direction). In bending test measurements, the span is 30 mm and the crosshead speed is 0.5 mm / min.

[0105] The calcined body may contain the above-mentioned additives.

[0106] The calcined body may be a molded body having a predetermined shape (hereinafter referred to as a "second molded body"). For example, the calcined body may have a disk shape, a rectangular parallelepiped shape, or a dental product shape (e.g., a crown shape). Dental products (e.g., crown-shaped prostheses) obtained by processing calcined zirconia disks using a CAD / CAM (Computer-Aided Design / Computer-Aided Manufacturing) system are also included in the calcined body.

[0107] The calcined body according to the third embodiment is produced with a small variation in shrinkage rate due to the composition, and therefore, with the calcined body according to the third embodiment, it is possible to equalize the shrinkage rate from the calcined body to the sintered body, and to produce a sintered body with high dimensional accuracy.

[0108] As described above, the calcined body according to the third embodiment can produce a highly translucent sintered body even with short firing times. Therefore, the calcined body according to the third embodiment has the advantages of short sintering times.

[0109] The calcined body of the present disclosure is fired at 1550°C for 30 minutes to produce a sintered body, which is designated as the first sintered body. The calcined body of the present disclosure is fired at 1550°C for 120 minutes to produce a sintered body, which is designated as the second sintered body. When comparing the translucency (see below) of the first sintered body and the second sintered body, the translucency of the first sintered body is preferably 85% or more of the translucency of the second sintered body, more preferably 90% or more, even more preferably 95% or more, and even more preferably substantially the same.

[0110] The calcined body according to the third embodiment has at least one of the advantages relating to dimensional accuracy and short-time sintering described above, and preferably has both advantages.

[0111] Next, a method for producing a calcined body according to the present disclosure will be described as a fourth embodiment.

[0112] The calcined body of the present disclosure can be produced by firing (i.e., calcining) the first compact produced in the first molding step at a temperature that does not result in sintering of the zirconia particles (calcination step). To ensure blocking, the firing temperature is preferably, for example, 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher. To improve dimensional accuracy, the firing temperature is preferably, for example, 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1100°C or lower.

[0113] It is believed that at such a firing temperature, the stabilizer does not dissolve in the solution.

[0114] The calcined body can be shaped to produce a second molded body (second molding step). The molding method is not limited to a specific method, and a suitable method can be selected depending on the purpose. For example, the second molded body can be produced by cutting a zirconia disk, which is also the calcined body, into the shape of a dental product (e.g., a crown-shaped prosthesis) using a CAD / CAM system.

[0115] According to the method for producing a calcined body of the fourth embodiment, it is possible to produce the calcined body of the third embodiment. According to the fourth embodiment, it is possible to produce a calcined body with small fluctuations in shrinkage rate and / or a calcined body that can be sintered in a short time.

[0116] As a fifth embodiment, a sintered body according to the present disclosure will be described. In the present disclosure, a sintered body can be defined as, for example, a body in which zirconia particles (powder) have reached a sintered state. In particular, the sintered body according to the present disclosure refers to a body made from the composition and / or calcined body according to the present disclosure. The relative density of the sintered body is preferably 99.5% or higher. The relative density can be calculated as the ratio of the actual density measured by Archimedes' method to the theoretical density.

[0117] The zirconia sintered body of the present disclosure includes not only a sintered body obtained by sintering molded zirconia particles under normal pressure or under no pressure, but also a sintered body obtained by densifying the zirconia particles by a high-temperature pressure treatment such as HIP (hot isostatic pressing) treatment.

[0118] The content ratio of zirconia and stabilizer in the sintered body is the same as the content ratio in the composition before the sintered body is produced and / or in the calcined body. Regarding the crystal system of zirconia in the sintered body, the proportion of monoclinic system f m is preferably 10% or less, more preferably 5% or less, and even more preferably substantially absent (0%). The crystal system other than the monoclinic system is a tetragonal system and / or a cubic system.

[0119] Regarding the proportion of the stabilizer dissolved in the sintered body, it is preferable that 95% or more of the stabilizer is dissolved in zirconia, and it is more preferable that substantially all of the stabilizer is dissolved in zirconia. y is preferably 5% or less, more preferably 1% or less, and even more preferably, all of it is substantially in solid solution (0%).

[0120] The light transmittance of the sintered body is preferably 12 or more, more preferably 14 or more, even more preferably 15 or more, and even more preferably 16 or more. * a * b * Lightness (color space) L in the color space (JISZ8781) * The L value was measured on a 1.2 mm thick sample with a white background. * The value of the first L * Let the value be the first L * For the same sample for which the value was measured, the L value was measured with the sample background set to black. * The value of the second L * Let the value be the first L * Second L from the value * The value is the value from which the L value has been subtracted. Regarding the method of preparing the sample, first, the granules (composition) are press-molded so that the thickness of the sintered body is 1.2 mm, and then, by CIP molding, a disk-shaped molded body with a diameter of, for example, 19 mm can be prepared. Next, the molded body is fired under predetermined firing conditions to prepare a sintered body with a thickness of 1.2 mm that serves as the sample. * To measure the value, apply the contact liquid to the surface of the sample, then use a colorimeter (e.g., CE100, analysis software Crystal Eye (manufactured by Olympus)) to measure the L value of the black and white backgrounds. * The contact liquid may have a refractive index nD of 1.60 measured at a measurement wavelength of 589 nm (sodium D line), for example.

[0121] The sintered body may contain the additives described above.

[0122] The sintered body may be a molded body having a predetermined shape (hereinafter referred to as a "third molded body"), for example, the sintered body may have a disk shape, a rectangular parallelepiped shape, or a dental product shape (e.g., a dental crown shape).

[0123] Next, as a sixth embodiment, a method for producing a sintered body according to the present disclosure will be described.

[0124] The sintered body of the present disclosure can be produced by firing the composition (including the first compact) and / or the calcined body (including the second compact) of the present disclosure at a temperature at which the zirconia particles are sintered (sintering step). The firing temperature is, for example, preferably 1400°C or higher, more preferably 1450°C or higher. The firing temperature is, for example, preferably 1650°C or lower, more preferably 1600°C or lower. The heating rate and cooling rate are preferably 300°C / min or lower.

[0125] In the sintering step, the holding time at the sinterable temperature (e.g., the maximum firing temperature) is preferably less than 120 minutes, more preferably 90 minutes or less, more preferably 75 minutes or less, more preferably 60 minutes or less, more preferably 45 minutes or less, and even more preferably 30 minutes or less. The holding time is preferably 1 minute or more, more preferably 5 minutes or more, and more preferably 10 minutes or more. According to the manufacturing method of the present disclosure, even with such a firing time, it is possible to suppress a decrease in the translucency of the sintered body produced. Furthermore, by shortening the firing time, it is possible to increase production efficiency and reduce energy costs.

[0126] In the sintering step, the holding time at the sinterable temperature (for example, the maximum firing temperature) can be, for example, 25 minutes or less, 20 minutes or less, or 15 minutes or less.

[0127] The temperature increase and decrease rates in the sintering step are preferably set so as to shorten the time required for the sintering step. For example, the temperature increase rate can be set so as to reach the maximum sintering temperature in the shortest time possible, depending on the performance of the sintering furnace. The temperature increase rate to the maximum temperature can be, for example, 10°C / min or more, 50°C / min or more, 100°C / min or more, 120°C / min or more, 150°C / min or more, or 200°C / min or more. The temperature decrease rate is preferably set so as not to cause defects such as cracks in the sintered body. For example, after heating is completed, the sintered body can be allowed to cool at room temperature.

[0128] In the manufacturing method of the present disclosure, it is believed that the stabilizer (for example, yttria) is dissolved in zirconia during the sintering process.

[0129] The sintered body can be molded to produce a third molded body (third molding step). The molding method is not limited to a specific method, and a suitable method can be selected depending on the purpose. For example, a zirconia block, which is also a sintered body, can be machined into the shape of a dental product (e.g., a crown-shaped prosthesis) using a CAD / CAM system to produce the third molded body.

[0130] As a seventh embodiment, a dental product of the present disclosure will be described. The dental product of the present disclosure includes a zirconia sintered body according to the fifth embodiment. The zirconia sintered body may have, for example, a crown shape. The dental product may further include a porcelain material laminated on the zirconia sintered body. The porcelain material may be a ceramic material such as a glass material. Examples of dental products include prostheses (e.g., ceramic frames, full-contour crowns), orthodontic products (e.g., orthodontic brackets), and dental implant products (e.g., dental implant abutments).

[0131] Next, as an eighth embodiment, a method for manufacturing a dental product according to the present disclosure will be described. The dental product can be produced by sintering a composition (including a first molded body) and / or a calcined body (including a second molded body) according to the present disclosure having a predetermined shape. The dental product can also be produced by cutting the sintered body according to the present disclosure (including a third molded body).

[0132] Dental products having porcelain can be produced, for example, by applying a slurry containing porcelain onto a sintered body, and firing the sintered body to which the porcelain has been applied to fuse the porcelain onto the sintered body.

[0133] According to the fifth to eighth embodiments, a sintered body and a dental product with high dimensional accuracy can be obtained, and / or a sintered body and a dental product with high translucency can be produced in a short time.

[0134] At the time of filing this application, it is believed that it is impossible or practical to directly identify the configurations and properties of the composition, calcined body, sintered body, and laminate other than those described herein by analysis, etc. Therefore, when identifying configurations or properties other than those described herein, it is believed that it is useful to identify them by their manufacturing methods.

[0135] Examples of the present disclosure will be described below, but the present invention is not limited to the following examples. [Example]

[0136] Examples 1 to 4 , Reference examples 1-3 and Comparative Examples 1 to 3] [Preparation of composition and XRD measurement] The zirconia composition of the present disclosure was prepared, and the crystal system of the zirconia and the extent to which the stabilizer was not dissolved in the zirconia were confirmed. The results are shown in Table 1.

[0137] Yttria was used as a stabilizer. Examples 1 to 3 and Reference Examples 1 to 3 In Example 1, the yttria addition rate was changed. In Example 4, the monoclinic ratio was changed. The yttria addition rate shown in Table 1 is the ratio of yttria to the total moles of zirconia and yttria. The steps shown in Table 1 indicate the compositions obtained in each step described below. f indicates the proportion of undissolved yttria. y was calculated based on the above formula 1. f m was calculated based on the above formula 2.

[0138] Examples 1 to 3 shown in Table 1 and Reference Examples 1 to 3The method for producing the composition according to the present invention will be described. First, monoclinic zirconium oxide and yttria were mixed to prepare a mixture (mixing step). The zirconium oxide and yttria were prepared in separate steps. Next, this mixture was added to water to prepare a slurry, which was then wet-pulverized and mixed in a ball mill until the average particle size reached 0.13 μm (primary pulverization step). This pulverized mixture is designated the composition for the "primary pulverization" step shown in Table 1. Next, the pulverized slurry was dried using a spray dryer, and the resulting powder was fired at 950°C for 2 hours (firing step). Next, the fired powder was added to water to prepare a slurry, which was then wet-pulverized in a ball mill until the average particle size reached 0.13 μm or less (secondary pulverization step). A binder was added to the pulverized slurry, which was then dried using a spray dryer to prepare a composition. This dried composition is designated the composition for the "secondary pulverization" step shown in Table 1.

[0139] As a comparative example, commercially available partially stabilized zirconia powder was also used. y and f m was calculated. The zirconia of Comparative Example 1 was TZ-3YSB-E manufactured by Tosoh Corporation. The zirconia of Comparative Example 2 was Zpex manufactured by Tosoh Corporation. The zirconia of Comparative Example 3 was Zpex Smile manufactured by Tosoh Corporation.

[0140] For the composition of Example 4, in the mixing step, the composition of Comparative Example 1 was added in addition to the monoclinic zirconium oxide and yttria, so that the proportion of monoclinic crystals in the composition was lower than in Examples 1 to 3.

[0141] In the commercially available zirconia powders of Comparative Examples 1 to 3, the zirconia crystal system was basically tetragonal and cubic, with monoclinic crystals accounting for at most about 50%. Furthermore, no XRD peaks of yttria were observed in the powders of Comparative Examples 1 to 3. Therefore, it is believed that all of the yttria was solid-dissolved in zirconia.

[0142] On the other hand, Examples 1 to 3 and Reference Examples 1 to 3In Example 1, the tetragonal and cubic crystals were partially converted to monoclinic crystals by the firing process, but 90% or more, and even 95% or more, of the crystals were monoclinic crystals. In Example 4, tetragonal partially stabilized zirconia was added, so that about 80% of the crystals were monoclinic crystals. and Reference Examples 1 to 3 In Example 1, which had a low yttria content, XRD peaks of yttria were observed. y The value was 2.5 or more and 6 or less. and Reference Examples 2-3 In this case, f y The value of the pulverization rate was between 4 and 10. y Although f immediately after the mixing process and immediately after the baking process is y This is thought to be due to the change in particle size and shape caused by the grinding, which resulted in a decrease in the relative peak of yttria to zirconia. y This does not deny the possibility of a decline in

[0143] [Table 1]

[0144] [ Reference examples 5~6, implementation Example 7 and Comparative Example 4] [Preparation of calcined body, measurement of shrinkage rate, and measurement of XRD pattern] reference Examples 1-2, 3-2 and Example Calcined blocks were prepared using each of the compositions of Comparative Example 4 and Comparative Example 2, and the variations in the dimensional changes of each calcined block were measured. 2 The pressed body was then subjected to a pressure of 1700 kg / cm. 2The first compact was then subjected to a CIP treatment to produce the first compact. The first compact was fired to produce a calcined body. The first compact was fired at three set temperatures: 1000°C, 1050°C, and 1100°C. For each firing, nine first compacts having the same dimensions were produced, and the electric furnace was divided into three upper and lower levels, with three first compacts placed on each level. The diameter of the disk was measured for each of the produced calcined bodies. Of the nine calcined bodies produced in one firing, the measured diameters (maximum diameter and minimum diameter) of the largest and smallest calcined bodies, as well as the difference between the maximum and minimum diameters, are shown in Tables 2 to 4. Of the nine calcined bodies, those within ±0.15 mm of the target diameter were judged to be acceptable. The target diameter was determined for each example depending on the composition and firing temperature. , reference example and were set individually for each comparative example. For example, reference In Example 5-2, the target diameter was set to 98.20 mm. Reference examples 5~6, implementation Example 7 The number of passed products (pass rate) in Comparative Example 4 are also shown in Tables 2 to 4.

[0145] Table 2 shows the results when the electric furnace temperature was set to 1000°C. When the set temperature reached 1000°C, the minimum temperature inside the furnace was 975°C and the maximum temperature was 1025°C. reference Example 5-1 6-1 and Examples In Comparative Example 7-1, the difference between the maximum and minimum dimensions could be made smaller than in Comparative Example 4-1. In other words, even if there was temperature unevenness in the firing furnace, the variation in the shrinkage rate of the calcined bodies fired at the same time could be reduced. reference Example 5-1 6-1 and Examples In Comparative Example 7-1, the shrinkage rates of all the calcined bodies were within the allowable range, but in Comparative Example 4-1, one-third of the calcined bodies were outside the allowable range.

[0146] Table 3 shows the results when the set temperature of the electric furnace was 1050°C. When the set temperature reached 1050°C, the minimum temperature inside the furnace was 1040°C and the maximum temperature was 1060°C. Even when the set temperature was 1050°C, reference In Examples 5-2 and 6-2, the variation in shrinkage rate was reduced more than in Comparative Example 4-2. reference In Examples 5-2 and 6-2, the shrinkage rates of all the calcined bodies were within the allowable range, but in Comparative Example 4-2, one-third of the calcined bodies were outside the allowable range.In Example 7-2, one calcined body was outside the allowable range, but better results were obtained than in Comparative Example 4-2.

[0147] Table 4 shows the results when the electric furnace temperature was set to 1100°C. When the set temperature reached 1100°C, the minimum temperature inside the furnace was 1090°C and the maximum temperature was 1100°C. Even when the set temperature was 1100°C, reference In Examples 5-3 and 6-3, the variation in shrinkage rate was reduced more than in Comparative Example 4-3. reference Example 5-3 and Example Although some parts of 7-3 were outside the allowable range, the pass rate was higher than that of comparative example 4-3.

[0148] The density of each calcined body was measured and the average value was 3.1 g / cm 3 It was.

[0149] reference Example 5-2, reference The XRD patterns of the calcined bodies prepared in Example 6-2 and Comparative Example 4-2 were measured using CuKα radiation. reference The XRD pattern of the calcined body prepared in Example 5-2 is shown in FIG. reference 3 shows the XRD pattern of the calcined body produced in Example 6-2 and Comparative Example 4-2.

[0150] 3, the calcined body of Comparative Example 4-2 did not show any peaks of monoclinic zirconia. Furthermore, no peaks of yttria were observed. On the other hand, FIGS. 1 and 2 show that referenceIn the calcined bodies of Examples 5-2 and 6-2, peaks of monoclinic, tetragonal, and cubic zirconia were observed, with the monoclinic peak being stronger. In addition, in both calcined bodies, a peak of yttria (peak number 6 in Figure 1 and peak number 5 in Figure 2) was also observed at 2θ of approximately 29.4°, suggesting that some of the yttria was not dissolved in the zirconia in the calcined bodies.

[0151] [Table 2]

[0152] [Table 3]

[0153] [Table 4]

[0154] [Examples 8 to 11 and Comparative Examples 5 to 8] [Measurement of shrinkage rate change with firing temperature] Calcined bodies were prepared under different firing temperature conditions, and the shrinkage of each calcined body was measured. In Example 8, the composition of Example 1-1 was used as is as a raw material. In Example 9, yttria was added to the composition of Example 1-1 so that the total yttria content was 6 mol%, and the resulting mixture was used as a raw material. That is, the amount of undissolved yttria in the composition of Example 1-1 was increased. In Example 10, the composition of Example 3-1 was used as is as a raw material. In Example 11, yttria-free zirconia was added to the composition of Example 3-1 so that the yttria content was 4 mol%, and the resulting mixture was used as a raw material. In Comparative Example 5, the composition of Comparative Example 1 was used as is as a raw material. In Comparative Example 6, the composition of Comparative Example 2 was used as is as a raw material. In Comparative Example 7, yttria was added to the composition of Comparative Example 1 so that the total yttria content was 6 mol%, and the resulting mixture was subjected to a primary grinding process and used as a raw material. In Comparative Example 8, yttria was added to the composition of Comparative Example 1 so that the total content of yttria was 6 mol %, and the powder that had been subjected to the above-mentioned mixing step to secondary pulverization step was used as the raw material.

[0155] First, a first molded body was prepared in the same manner as in Examples 1 to 3. The first molded body was calcined by varying the maximum firing temperature in increments of 50°C within the range of 950°C to 1200°C, and the shrinkage of each calcined body was measured. In each Example, three samples were prepared and placed in the same position in the firing furnace to avoid the influence of temperature variations within the furnace. The dimensions of the first molded body were the same as in Examples 5 to 7 described above. The shrinkage was calculated using the following formula and was found to be the average value of the three samples. The results are shown in Table 5. Based on the results shown in Table 5, a graph of the shrinkage versus firing temperature is shown in Figure 4. Shrinkage rate (%)={(diameter of first compact)−(diameter of calcined body)} / (diameter of first compact)×100

[0156] When the XRD patterns of the calcined bodies produced in Examples 8 to 11 were measured, the main crystal system of the zirconia was found to be monoclinic, and a peak of yttria was also confirmed.

[0157] As shown in the graph of FIG. 4, in Comparative Examples 5 to 8, the shrinkage rate increases from a firing temperature of approximately 1000°C. In other words, the rate-changing temperature can be considered to be approximately 1000°C. On the other hand, in Examples 8 to 11, the shrinkage rate increases from a firing temperature of approximately 1100°C. In other words, the rate-changing temperature can be considered to be approximately 1100°C. Therefore, as shown in Comparative Example 4, the composition according to the comparative example has a significantly different shrinkage rate depending on the firing temperature in the range of 1000°C to 1100°C (high shrinkage rate), which results in calcined bodies with different shrinkage amounts due to temperature variations in the firing furnace. On the other hand, with the composition of the present disclosure, as shown in Examples 5 to 7, the shrinkage rate is almost the same in the range of 1000°C to 1100°C (low shrinkage rate). Therefore, even if temperature variations occur in the firing furnace, calcined bodies with a uniform amount of shrinkage can be produced.

[0158] The zirconia crystal system in the compositions of Comparative Examples 5 to 8 was tetragonal and cubic, with substantially no monoclinic crystals being detectable. In Comparative Examples 5 and 6, no undissolved yttria was present in the compositions. In Comparative Examples 7 and 8, yttria was added so that undissolved yttria was present in the compositions. On the other hand, in the compositions of Examples 8 to 11, the zirconia crystal system was primarily monoclinic, with undissolved yttria present. This suggests that the speed change temperature can be increased by preparing a calcined body from a composition primarily composed of monoclinic crystals.

[0159] [Table 5]

[0160] [ reference Example 12 and Comparative Example 9 [Measurement of light transmittance as a function of firing time] A sintered body was produced using the composition (calcined body) of the present disclosure, and the relationship between the holding time at the maximum temperature and the translucency was investigated. reference In Example 12 referenceThe composition of Example 3-2 was used. First, a molded body was prepared to obtain a sintered body with a thickness of 1.2 mm. The molded body was then fired at 1000°C for 2 hours to produce a calcined body. Next, the maximum temperature was set to 1550°C, and the sample (calcined body) was fired for 120 minutes to produce a sintered body. The translucency of the sintered body was then measured. Next, for samples prepared using the same method, sintered bodies were prepared at maximum firing temperatures of 1450°C, 1500°C, 1550°C, and 1600°C, with a holding time at the maximum temperature of 30 minutes, and the translucency of each sintered body was measured. The heating rate and cooling rate were the same for both the 30-minute firing and the 120-minute firing. The change in translucency of the sintered body fired at the maximum temperature for 30 minutes relative to the translucency of the sintered body fired at the maximum temperature for 120 minutes was calculated as the rate of change. As a comparative example, the same test was conducted using the composition of Comparative Example 3. The results are shown in Table 6. A graph created based on the rate of change shown in Table 6 is shown in Figure 5.

[0161] The light transmittance was measured using a color difference meter CE100 and analysis software Crystal Eye (manufactured by Olympus Corporation). * a * b * Lightness (color space) L in the color space (JISZ8781) * The L value was calculated using the measured value against a white background. * The value of the first L * Let the value be the first L * For the same sample for which the value was measured, the L value was measured with the sample background set to black. * The value of the second L * Let the value be the first L * Second L from the value * The value obtained by subtracting the value from the total was used as the numerical value indicating the light transmittance. A contact liquid with a refractive index nD of 1.60 was applied to the measurement surface of the sample.

[0162] Generally, increasing the firing temperature can increase the translucency of the sintered body. However, in Comparative Example 9, when firing was performed at the maximum temperature for 30 minutes, the transparency could not be increased even when the firing temperature was increased, and the translucency was about 80% of that obtained after firing for 120 minutes. referenceIn Example 12, the same translucency was achieved even with 30-minute firing as with 120-minute firing. Even at a maximum firing temperature of 1450°C, the translucency was 85% or more of that achieved with 120-minute firing, and at a maximum firing temperature of 1500°C or higher, the translucency was 95% or more, nearly 100%, of that achieved with 120°C firing. Thus, the composition of the present disclosure can shorten the firing time. This can increase the production efficiency of sintered bodies and reduce energy costs. Furthermore, when dental prostheses are produced using the composition and calcined body of the present disclosure, the time burden on patients can be reduced.

[0163] The crystal system of the composition used in Comparative Example 9 is tetragonal and cubic, and monoclinic crystals are not substantially detectable. It is believed that all of the yttria is dissolved in zirconia. The composition of Comparative Example 3 used in Comparative Example 9 is in a granular state, and the average particle size could not be measured, but estimating from Comparative Example 10, it is believed to be 0.7 μm or more. reference Used in Example 12 reference In the composition of Example 3-2, the zirconia crystal system was mainly monoclinic, and undissolved yttria was present. The average particle size was 0.13 μm. It is believed that at least one of these differences affects the feasibility of short-time sintering.

[0164] reference No monoclinic zirconia peak was detected in the XRD pattern of the sintered body produced in Example 12. Furthermore, no yttria peak was detected. From this, it is believed that yttria was dissolved in zirconia during firing for sintering, and the zirconia underwent a phase transition from monoclinic to cubic.

[0165] [Table 6]

[0166] Example 13 , reference example 14 and Comparative Examples 10 to 12] [Effects of undissolved yttria and particle size] The behavior of the composition of Comparative Example 1 was tested when undissolved yttria was present and the particle size was reduced. Reference example The composition of Example 3-1 and Reference example The results are the same as in 3-2. The composition of Comparative Example 10 is the same as in Comparative Example 1, but the primary pulverization step was carried out to the extent that the granules were crushed. The composition of Comparative Example 11 was prepared by adding yttria to the composition of Comparative Example 1 so that the yttria content was 6 mol%, and then carrying out the above-mentioned primary pulverization step until the particle size was approximately the same as that of the composition of Example 3. The composition of Comparative Example 12 was prepared by further carrying out the above-mentioned firing step and secondary pulverization step to the composition of Comparative Example 11. The results are shown in Tables 7 and 8. The BET specific surface area was measured in accordance with JIS Z 8830 (2013). The average particle size was measured using a laser diffraction / scattering particle size distribution measurement method for powder in a state before being made into granules. The "1100°C shrinkage rate" and the "1150°C shrinkage rate" were measured in the same manner as in Examples 8 to 11. The "translucency" was determined by reference In the same manner as in Example 12, a sintered body was produced from the calcined body by holding it at a maximum firing temperature of 1550°C for 30 minutes, and the sintered body was visually judged for its high translucency. Grade A indicates that the sintered body has the same translucency as a sintered body held at the maximum temperature for 2 hours, and grade B indicates that the sintered body has lower translucency than a sintered body held at the maximum temperature for 2 hours.

[0167] The average particle size of the composition of Comparative Example 10, i.e., Comparative Example 1, is 0.67 μm, which is larger than the particle size of the composition of the present disclosure. In addition, the shrinkage rate during calcination is high as shown in Comparative Example 5. In Comparative Example 11, undissolved yttria is present in the composition of Comparative Example 1. In addition, the average particle size of the composition of Comparative Example 11 is 0.67 μm, which is larger than the particle size of the composition of Examples 13 and 14. Reference exampleThe results were comparable to those of Comparative Example 14. However, the shrinkage rates were high in both cases, making the compositions susceptible to temperature variations in the firing furnace. Furthermore, sufficient translucency could not be obtained by sintering for a short period of time. In Comparative Example 12, it is believed that the separately added yttria was dissolved in the zirconia during the firing process. Furthermore, the firing process promoted a phase transition from monoclinic to tetragonal and cubic crystals. However, Comparative Example 11 produced results similar to those of Comparative Example 12.

[0168] Example 13 and Reference example The BET specific surface area of ​​composition 14 is 9m 2 / g~10m 2 The average particle size was 0.11 μm to 0.13 μm. Reference example The shrinkage rate of 14 is low as shown in Examples 8 to 11. Furthermore, sufficient translucency can be obtained even with short-time sintering. From this, it is considered that the main crystal system of zirconia in the composition must be monoclinic. y It may be preferable for the temperature to be somewhat higher.

[0169] [Table 7]

[0170] [Table 8]

[0171] [Examples 15 to 21 and Comparative Examples 13 to 16] [Effects of particle size and BET specific surface area] Compositions with different average particle sizes were prepared, and the above-mentioned tests were performed on each composition. The yttria content of the composition was 6 mol%. The compositions of Examples 15 to 21 and Comparative Examples 15 to 16 were prepared by a hydrolysis method. The composition of Comparative Example 13 was prepared by a hydrothermal synthesis method. The composition of Comparative Example 14 was prepared by a plasma melting method. The average particle sizes of the compositions of Examples 15 to 21 and Comparative Examples 15 to 16 were measured using a laser diffraction / scattering particle size distribution measurement method. The average particle sizes of the compositions of Comparative Examples 13 and 14 were calculated from the BET specific surface area, assuming that each particle was spherical. The BET specific surface areas of the compositions of Examples 15 to 21 and Comparative Examples 13 to 16 were measured in accordance with JIS Z 8830 (2013). The results are shown in Table 8. "Sinterability" refers to the test results of whether or not the composition could be sintered at 1550°C. Grade A indicates that the product was sinterable, Grade B indicates that the product was cloudy, and Grade C indicates that it could not be sintered. "Shrinkage test pass rate" was calculated using the following: Reference Examples 5 to 6 and implementation Example 7 The "transparency change rate" is the same as the change rate shown in Example 12, and is the change rate when a sintered body is produced at the maximum firing temperature of 1550°C.

[0172] Average particle size 0.08μm~0.15μm, BET specific surface area 7m 2 / g~28m 2 Good results were obtained in all of Examples 15 to 21, where the average particle size was 30 m / g. Particularly, good results were obtained in Examples 16 to 20. On the other hand, it is thought that in Comparative Examples 13 and 14, the average particle size was too small, and therefore sufficient sintering was not possible. For this reason, it is thought that the average particle size is preferably larger than 0.05 μm, more preferably 0.08 μm or more, and even more preferably 0.10 μm or more. The BET specific surface area was 30 m 2 / g or less, and 2 / g or less is considered more preferable. Furthermore, in Comparative Examples 15 and 16, both the shrinkage test pass rate and the light transmittance change rate were low. In particular, compared with Example 21, Comparative Examples 15 and 16, the shrinkage test pass rate and the light transmittance change rate decreased as the average particle size increased (as the BET specific surface area decreased). This suggests that the average particle size and / or BET specific surface area may have an effect on the speed change temperature and short-time sintering. It is considered that the average particle size is preferably smaller than 0.18 μm, more preferably 0.15 μm or less, and even more preferably 0.14 μm or less. The BET specific surface area is 6.5 m 2 / g or more is preferable, and 7m 2 / g or more is more preferable, and 8m 2 It is considered more preferable that the saturation rate is 1 / g or more.

[0173] [Table 9]

[0174] [ reference Example 22] [Observation by electron microscope] reference The shapes of the granules of Example 3-2 and Comparative Example 1 were observed using a field emission scanning electron microscope (FE-SEM). The shapes of the particles constituting the granules were also observed. reference An electron microscope photograph of the granules of Example 3-2 is shown in Figure 7. reference An electron microscope photograph of constituent particles of Example 3-2 is shown in Fig. 8. An electron microscope photograph of granules of Comparative Example 1 is shown in Fig. 9. An electron microscope photograph of constituent particles of Comparative Example 1 is shown in Fig. 10.

[0175] The granules shown in Figure 6 appear spherical (perfectly spherical) and have a high degree of sphericity (circularity). In the particles constituting the granules shown in Figure 7, many of the particles are primary particles that appear separable, and there are few secondary particles formed by agglomerations of primary particles. That is, the granules shown in Figure 6 are primarily composed of primary particles. On the other hand, the granules shown in Figure 8 are non-spherical (irregularly shaped) and have a low degree of sphericity (circularity). The particles constituting the granules shown in Figure 9 are secondary particles formed by inseparable agglomerations of primary particles (secondary particles formed by the fusion of multiple primary particles). That is, the granules shown in Figure 8 are primarily composed of irregular secondary particles. This is likely why the average particle size of Comparative Example 1 is large. For example, based on the above-mentioned Comparative Example 10, it is believed that the granules of Comparative Example 1 are composed of constituent particles of at least approximately 0.7 μm or larger (although it is possible that the particles constituting the granules were finely pulverized during granule crushing). Furthermore, it is believed that the difference in sphericity of the granules in Comparative Example 1 occurs because the granules are composed of irregular secondary particles.

[0176] [ reference Example 23] [Measurement of bending strength of calcined body] reference The composition of Example 3-2 was fired at 1100° C. to prepare a calcined body, and the bending strength was measured under the conditions in accordance with the above-mentioned JIS R1601, and was found to be 35 MPa.

[0177] [Examples 24 to 25] [Effect of yttria addition rate] In Example 13, the test was performed using the composition of Example 3-1, but in Examples 24 and 25, the same test as in Example 13 was performed on the compositions of Examples 1-1 and 2-1, which had different yttria addition rates. The results are shown in Table 10. The measurement methods and evaluation criteria for each measurement value were the same as in Example 13.

[0178] As is clear from comparisons with Examples 13 and 14 and Comparative Examples 10 to 12 shown in Table 8, Examples 24 and 25 were able to achieve low shrinkage rates at 1100°C and 1150°C. Furthermore, sufficient translucency was achieved even with short-time sintering. This suggests that the shrinkage rate during preparation of the calcined body and the translucency during short-time sintering do not depend on the yttria content. Therefore, the yttria content can be selected to a desired value depending on the translucency, strength, etc. of the sintered body to be obtained.

[0179] In Examples 24 and 25, no effect of the BET specific surface area was confirmed.

[0180] [Table 10]

[0181] [Example 26~ 30 and Reference Example 31 35] [Effect of particle size on translucency] Example 2-1 and reference Based on the composition of Example 2-2, the time for primary grinding was adjusted to produce Examples 2-1 and 2-2. reference Compositions having average particle sizes different from those of Example 2-2 were prepared. The compositions of Examples 26 to 30 were the same as the composition of Example 2-1 except for the average particle sizes. reference The compositions of Examples 31 to 35 have the same properties except for the average particle size. reference The composition is the same as that of Example 2-2. and reference examples The composition was fired at 1000°C to prepare a calcined body, and the calcined body was fired at a maximum firing temperature of 1550°C for 15 minutes to prepare a sintered body, and another sintered body was fired for 30 minutes to prepare a sintered body. reference The translucency was measured in the same manner as in Example 12. The heating rate was set to 150°C / min, the maximum rate of the firing furnace. Cooling was performed by allowing the material to stand at room temperature. The results are shown in Table 11. The measured values ​​shown in Table 11 are the average values ​​of three measurements. The rate of change shown in Table 11 is the rate of change from the measured value of translucency in Example 26 for Examples 27 to 30, reference For examples 31 to 35 referenceThis is the percent change in transmittance from the measured value in Example 31.

[0182] When comparing the sintered body produced by holding the maximum firing temperature for 15 minutes with the sintered body produced by holding the maximum firing temperature for 30 minutes, the results are as follows: 30 and Reference Example 31 The translucency was almost the same for all sintered bodies at 15 minutes and 35 minutes. The translucency values ​​were also comparable to those of the sintered bodies obtained with a holding time of 2 hours. This demonstrates that the compositions and calcined bodies of the present disclosure can be sintered in as short a time as 15 minutes.

[0183] reference Based on the composition of Example 2-2 reference In Examples 31 to 35, reference Although the translucency of the sintered body of Example 35 was slightly reduced, no significant change in translucency was observed. That is, for sintered bodies produced from compositions that underwent the firing and secondary pulverization steps in the composition production process, no dependence of translucency on the average particle size of the composition was observed. However, in Examples 26 to 30, which were based on the composition of Example 2-1, sintered bodies produced from compositions with an average particle size of 0.13 μm or more tended to have lower translucency than sintered bodies produced from compositions with an average particle size of less than 0.13 μm. Thus, the sintered bodies produced in Examples 29 and 30 also had sufficient translucency for use, for example, in dental prosthetic materials. However, when producing sintered bodies from compositions that did not undergo the firing and secondary pulverization steps, if the translucency of the sintered body is to be further enhanced, it is considered preferable to set the average particle size of the composition to less than 0.13 μm, preferably 0.125 μm or less, more preferably 0.120 μm or less, and even more preferably 0.115 μm or less.

[0184] [Table 11]

[0185] [Example 36] [Direct sintering of the composition] Example 2-1 and Reference exampleThe first compacts prepared from the composition 2-2 were fired at a maximum temperature of 1550°C for 30 minutes without first being calcined to produce sintered bodies. All of the sintered bodies had the same translucency as the sintered bodies prepared via calcination. This confirmed that sintered bodies can be produced directly from the composition of the present disclosure without first being calcined.

[0186] The composition, calcined body, sintered body, and manufacturing method thereof of the present invention have been described based on the above embodiments and examples, but are not limited to the above embodiments and examples, and can include various modifications, changes, and improvements to each disclosed element (including elements described in the claims, specification, and drawings) within the scope of the present invention and based on the basic technical idea of ​​the present invention. Furthermore, various combinations, substitutions, and selections of each disclosed element are possible within the scope of the claims of the present invention.

[0187] Further objects, purposes and modes (including modifications) of the present invention will become apparent from the entire disclosure of the present invention including the claims.

[0188] With respect to numerical ranges set forth herein, unless otherwise specified, any numerical value or range falling within that range should be construed as being specifically set forth herein. [Industrial Applicability]

[0189] The compositions, calcined bodies, and sintered bodies disclosed herein, as well as methods for producing them, can be used in a variety of applications, such as dental materials such as prostheses, optical fiber connecting components such as ferrules and sleeves, various tools (e.g., grinding balls, grinding tools), various parts (e.g., screws, bolts, and nuts), various sensors, electronics components, and decorative items (e.g., watch bands).When the compositions, calcined bodies, and sintered bodies are used as dental materials, they can be used, for example, for copings, frameworks, crowns, crown bridges, abutments, implants, implant screws, implant fixtures, implant bridges, implant bars, brackets, denture bases, inlays, onlays, onlays, orthodontic wires, and laminate veneers.

Claims

1. A composition as a precursor of a zirconia calcined body, the composition being used to prepare the zirconia calcined body, comprising: zirconia powder having 55% or more monoclinic crystals; and a stabilizer capable of suppressing the phase transition of zirconia, the average particle size of the zirconia particles and the particles of the stabilizer is 0.06 μm to less than 0.13 μm; At least a part of the stabilizer is not solid-dissolved in the zirconia, A composition that has not been fired at temperatures above 700°C.

2. BET specific surface area is 7.5m ２ / g~25m ２ The composition of claim 1, wherein the hydroxyl group is 0.1 to 0.5 wt.

3. 3. The composition of claim 1, wherein at least 80% of the zirconia is monoclinic.

4. The composition according to any one of claims 1 to 3, wherein the average particle size is from 0.10 µm to less than 0.13 µm.

5. The composition of any one of claims 1 to 4, wherein the average particle size is less than 0.115 µm.

6. The composition of any one of claims 1 to 5, wherein the stabilizer is yttria.

7. The composition according to claim 6, containing yttria in an amount of 3 mol % to 7.5 mol % based on the total moles of zirconia and yttria.

8. 8. The composition according to claim 6, wherein an yttria peak is present in the X-ray diffraction pattern.

9. f calculated based on the following equation 1 ｙ The composition according to any one of claims 6 to 8, wherein: However, I ｙ (111) indicates the peak intensity of the (111) plane of yttria in the X-ray diffraction pattern using CuKα radiation, I ｍ (111) and I ｍ (11-1) indicates the peak intensity of the (111) plane and (11-1) plane of the monoclinic system of zirconia in the X-ray diffraction pattern, I ｔ (111) indicates the peak intensity of the (111) plane of the tetragonal system of zirconia in the X-ray diffraction pattern, I ｃ (111) indicates the peak intensity of the (111) plane of the cubic crystal system of zirconia in the X-ray diffraction pattern. [Equation 1]

10. Said f ｙ The composition of claim 9, wherein is 15% or less.

11. The content of yttria in the composition is 3 mol% or more and less than 4.5 mol%, Said f ｙ The composition according to claim 9 or 10, wherein the amount of hydroxybenzoates is 2% or more.

12. the content of yttria in the composition is 4.5 mol% or more and less than 5.8 mol%, Said f ｙ The composition according to claim 9 or 10, wherein the amount of hydroxybenzoates is 3% or more.

13. the content of yttria in the composition is 5.8 mol% or more and 7.5 mol% or less, Said f ｙ The composition according to claim 9 or 10, wherein the amount of hydroxybenzoates is 4% or more.

14. zirconia having at least 55% monoclinic crystals; and a stabilizer capable of suppressing the phase transition of zirconia, At least a part of the stabilizer is not solid-dissolved in the zirconia, A calcined body produced by firing a press-molded body of the composition according to any one of claims 1 to 13 at 800°C to 1200°C.

15. Density is 2.7 g / cm ３ ~4.0 g / cm ３ The calcined body according to claim 14, wherein

16. The calcined body according to claim 14 or 15, having a bending strength of 15 MPa to 70 MPa.

17. The calcined body according to any one of claims 14 to 16, wherein 80% or more of the zirconia is monoclinic.

18. the stabilizer is yttria; The calcined body according to any one of claims 14 to 17, wherein an yttria peak is present in an X-ray diffraction pattern.

19. f calculated based on the following equation 2 ｙ The calcined body according to claim 18, wherein However, I ｙ (111) indicates the peak intensity of the (111) plane of yttria in the X-ray diffraction pattern using CuKα radiation, I ｍ (111) and I ｍ (11-1) indicates the peak intensity of the (111) plane and (11-1) plane of the monoclinic system of zirconia in the X-ray diffraction pattern, I ｔ (111) indicates the peak intensity of the (111) plane of the tetragonal system of zirconia in the X-ray diffraction pattern, I ｃ (111) indicates the peak intensity of the (111) plane of the cubic crystal system of zirconia in the X-ray diffraction pattern. [Equation 2]

20. Said f ｙ The calcined body according to claim 19, wherein the content of SiO2 is 15% or less.

21. The content of yttria in the composition is 3 mol% or more and less than 4.5 mol%, Said f ｙ The calcined body according to claim 19 or 20, wherein the content of C is 2% or more.

22. the content of yttria in the composition is 4.5 mol% or more and less than 5.8 mol%, Said f ｙ The calcined body according to claim 19 or 20, wherein the content of C is 3% or more.

23. the content of yttria in the composition is 5.8 mol% or more and 7.5 mol% or less, Said f ｙ The calcined body according to claim 19 or 20, wherein the content of C is 4% or more.

24. a first translucency of a first sintered body produced by firing the calcined body at 1550°C for 30 minutes; When compared with the second translucency of a second sintered body produced by firing the calcined body at 1550°C for 120 minutes, The calcined body according to any one of claims 14 to 23, wherein the first translucency is 85% or more of the second translucency.

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