Zirconium oxide composition, pre-calcined body, sintered body, and method for producing same

Abstract

The invention relates to a zirconia composition, a pre-calcined body, a sintered body, and a method for producing the same. The composition contains 55% or more of a monoclinic zirconium oxide powder, and a stabilizer capable of suppressing phase transfer of zirconium oxide. The average particle size is 0.06 mu m to 0.17 mu m. At least a portion of the stabilizer is not solid-soluble in zirconia.

Description

[0001] This application is a divisional application of PCT Patent Application No. PCT / JP2017 / 033980, entitled "Zirconia Composition, Pre-Calcined Body and Sintered Body, and Manufacturing Method Thereof", the entire disclosure of which is incorporated herein by reference.

[0002] Related Applications This disclosure claims priority from Japanese Patent Application No. Japanese Patent Application No. 2016-183129 (filed on September 20, 2016), the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a composition containing mainly zirconia (zirconium oxide (IV); ZrO2). Furthermore, the present disclosure relates to a pre-calcined body and a sintered body of zirconia. Further, the present disclosure relates to a manufacturing method of a zirconia composition, a pre-calcined body and a sintered body. BACKGROUND

[0004] Zirconia is a compound that undergoes phase transition among a plurality of crystal systems. Therefore, partially stabilized zirconia (PSZ; Partially-Stabilized Zirconia) and fully stabilized zirconia in which a stabilizer such as yttria (yttrium oxide; Y2O3) is solid-solved in zirconia to suppress phase transition are utilized in a variety of fields. For example, in Patent Literature 1, a partially stabilized zirconia sintered body for use in a dental material is disclosed.

[0005] The light-transmitting zirconia sintered body described in Patent Literature 1 is produced by sintering a press-molded body of a zirconia powder at 1450°C, a temperature increase rate of 600°C / hr, and a holding time of 2 hours. The zirconia powder contains yttria of more than 4.0 mol% and 6.5 mol% or less, and alumina of less than 0.1 wt%, has a BET specific surface area of 8 to 15 m 2 / g, an average particle diameter of 0.40 to 0.50 μm, and a total proportion of tetragonal crystals and cubic crystals contained in the crystal is 80% or more.

[0006] Prior Art Documents Patent Literature Patent Literature 1: WO2015 / 098765A1. SUMMARY

[0007] Problems to be Solved by the Invention The zirconia sintered body obtained by sintering the zirconia particles (powder) is generally high in strength, and thus it is not easy to directly machine the zirconia sintered body into a desired shape. Therefore, the molding of the zirconia sintered body is sometimes performed in a pre-calcined body in which a press-molded body of the zirconia powder, including a molded body subjected to a CIP (Cold Isostatic Pressing) treatment, is calcined at a temperature that does not reach the sintering temperature. At this time, the block of the zirconia pre-calcined body is molded into a desired shape by cutting or the like, and the molded pre-calcined body is calcined at a temperature higher than the sintering temperature, whereby a zirconia sintered body having a target shape is produced.

[0008] The press-molded body of the zirconia powder, if calcined, shrinks depending on the calcination temperature. For example, in the press-molded body, the shrinkage from the pre-calcined body is about 1%, and the shrinkage from the sintered body is about 20%. Therefore, the molding of the pre-calcined body takes into account the shrinkage rate thereof, and is performed to be larger than the size of the sintered body that becomes the final target product. For example, the size of the molded pre-calcined body is determined based on a coefficient calculated by subtracting the shrinkage rate from the press-molded body to the pre-calcined body from the shrinkage rate from the press-molded body to the sintered body.

[0009] Therefore, when a plurality of press-molded bodies are calcined in one calcination furnace to produce a plurality of pre-calcined bodies (blocks), it is desirable that the shrinkage rate from the press-molded body to the pre-calcined body be less likely to be affected by a temperature difference (temperature unevenness) occurring in the calcination furnace at the time of production of the pre-calcined body among the plurality of products.

[0010] Further, in the production method of the zirconia sintered body described in Patent Literature 1, the holding time at the maximum temperature reaches 2 hours. Such a long-time calcination decreases the production efficiency while increasing the energy cost. Further, for example, when a dental restoration is produced using the zirconia sintered body, the patient cannot receive treatment with the restoration on the day of the visit, and must visit the hospital again on another day in order to receive treatment with the restoration. On the other hand, in the zirconia powder described in Patent Literature 1, if the holding time at the maximum temperature is shortened, the sintered body becomes cloudy and the light transmittance thereof decreases.

[0011] Therefore, there is a demand for a zirconia composition and a pre-calcined body that can maintain the light transmittance of the sintered body while shortening the calcination time.

[0012] Means for solving the problem According to a first aspect of the present disclosure, there is provided a composition containing: a zirconia powder of which 55% or more is monoclinic crystals, and a stabilizer that can suppress phase transition of the zirconia. The average particle diameter of the zirconia particles and the particles of the stabilizer is 0.06 μm to 0.17 μm. At least a part of the stabilizer is not solid-solved in the zirconia.

[0013] According to a second aspect of the present disclosure, there is provided a pre-calcined body containing: zirconia of which 55% or more is monoclinic crystals, and a stabilizer that suppresses phase transition of the zirconia. At least a part of the stabilizer is not solid-solved in the zirconia.

[0014] According to a third aspect of the present disclosure, there is provided a pre-calcined body that is produced by calcining a press-molded body of the composition according to the first aspect at 800°C to 1200°C.

[0015] According to a fourth aspect of the present disclosure, there is provided a zirconia pre-calcined body that is obtained by consolidating a zirconia powder without reaching a sintering degree. The zirconia pre-calcined body contains a stabilizer that suppresses phase transition of the zirconia. When a first light transmittance of a first sintered body produced by calcining the pre-calcined body at 1550°C for 30 minutes is compared with a second light transmittance of a second sintered body produced by calcining the pre-calcined body at 1550°C for 120 minutes, the first light transmittance is 85% or more of the second light transmittance.

[0016] According to a fifth aspect of the present disclosure, a method for producing a composition includes a mixing step of producing a mixture of a zirconia powder of which 55% or more is monoclinic crystals, and a stabilizer that suppresses phase transition of the zirconia. The method for producing a composition does not include a step of calcining the mixture at a temperature of 700°C or higher.

[0017] According to a sixth aspect of the present disclosure, there is provided a method for producing a zirconia pre-calcined body, including: a first molding step of molding a composition according to the first aspect and / or the fifth aspect to produce a first molded body; and a pre-calcining step of calcining the first molded body at a temperature that does not reach a sintering degree to produce a pre-calcined body.

[0018] According to a seventh aspect of the present disclosure, there is provided a method for producing a zirconia sintered body, including: a first molding step of molding a composition according to the first aspect and / or the fifth aspect to produce a first molded body; and a sintering step of calcining the first molded body at a temperature of 700°C or higher to produce a sintered body.

[0019] According to an eighth aspect of the present disclosure, there is provided a method for producing a zirconia sintered body, including: a sintering step of calcining a zirconia pre-calcined body according to at least one of the third aspect, the fourth aspect, and the sixth aspect at a temperature of 700°C or higher to produce a sintered body.

[0020] Effects of the Invention According to the present disclosure, it is possible to suppress a variation in shrinkage rate of a composition to a pre-calcined body that can be caused by temperature unevenness in a calcining furnace. Thereby, it is possible to improve a yield of a product, and to improve a production efficiency of the product. Furthermore, it is possible to mold a sintered body with higher precision.

[0021] According to the present disclosure, it is possible to produce a zirconia sintered body having high light transmittance while shortening the production time of the sintered body. Thus, it is possible to reduce the energy cost while improving the production efficiency of products. When the zirconia sintered body is applied to a dental restoration, it is possible to reduce the time burden on patients.

[0022] The composition of the present disclosure can have at least one of the advantages of suppressing the above-mentioned shrinkage deviation and shortening the production time. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is an X-ray diffraction pattern of the pre-sintered body produced in Example 5-2.

[0024] Figure 2 is an X-ray diffraction pattern of the pre-sintered body produced in Example 6-2.

[0025] Figure 3 is an X-ray diffraction pattern of the pre-sintered body produced in Comparative Example 4-2.

[0026] Figure 4 is a graph showing the change in shrinkage rate with respect to the sintering temperature.

[0027] Figure 5 is a graph showing the change in light transmittance with respect to the sintering temperature.

[0028] Figure 6 is an electron microscope photograph of the particles of Example 3-2.

[0029] Figure 7 is an electron microscope photograph of the constituent particles of Example 3-2.

[0030] Figure 8 is an electron microscope photograph of the particles of Comparative Example 1.

[0031] Figure 9 is an electron microscope photograph of the constituent particles of Comparative Example 1. DETAILED DESCRIPTION

[0032] Preferred modes of each of the above-mentioned aspects are described below.

[0033] According to the preferred mode of the above-mentioned first aspect, the BET specific surface area is 7.5 m 2 / g ~ 25 m 2 / g.

[0034] According to the preferred mode according to the above-mentioned first aspect, 80% or more of the zirconia is monoclinic crystals.

[0035] According to the preferred mode of the above-mentioned first aspect, the average particle diameter is 0.10 μm ~ 0.14 μm.

[0036] According to the preferred mode of the above-mentioned first aspect, the average particle diameter is less than 0.13 μm.

[0037] According to the preferred mode of the above-mentioned first aspect, the stabilizer is yttria.

[0038] According to the preferred mode of the above-mentioned first aspect, the composition contains 3 to 7.5 mol% of yttria relative to the total mol of zirconia and yttria.

[0039] According to the preferred mode of the above-mentioned first aspect, a peak of yttria is present in the X-ray diffraction pattern of the composition.

[0040] According to the preferred mode of the above-mentioned first aspect, f y is 1% or more.

[0041] According to the preferred mode of the above-mentioned first aspect, f y is 15% or less.

[0042] According to the preferred mode of the above-mentioned first aspect, the content of yttria in the composition is 3 mol% or more and less than 4.5 mol%.f y is 2% or more.

[0043] According to the preferred mode of the above-mentioned first aspect, the content of yttria in the composition is 4.5 mol% or more and less than 5.8 mol%.f y is 3% or more.

[0044] According to the preferred mode of the above-mentioned first aspect, the content of yttria in the composition is 5.8 mol% or more and 7.5 mol% or less.f y is 4% or more.

[0045] According to the preferred mode of the above-mentioned second aspect, the density of the precalcined body is 2.7 g / cm 3 to 3.6 g / cm 3 .

[0046] According to the preferred mode of the above-mentioned second aspect, the flexural strength of the precalcined body is 15 to 70 MPa.

[0047] According to the preferred mode of the above-mentioned second aspect, 80% or more of the zirconia is monoclinic crystal.

[0048] According to the preferred mode of the above-mentioned second aspect, the stabilizer is yttria.

[0049] According to the preferred mode of the above-mentioned second aspect, 3 to 7.5 mol% of yttria is contained relative to the total mol of zirconia and yttria.

[0050] According to the preferred mode of the above-mentioned 2nd aspect, the peak of yttria is present in the X-ray diffraction pattern of the pre-calcined body.

[0051] According to the preferred mode of the above-mentioned 2nd aspect, f is calculated based on the following mathematical expression 1 y is 1% or more.

[0052] According to the preferred mode of the above-mentioned 2nd aspect, f y is 15% or less.

[0053] According to the preferred mode of the above-mentioned 2nd aspect, the content of yttria in the composition is 3 mol% or more and less than 4.5 mol%.f y is 2% or more.

[0054] According to the preferred mode of the above-mentioned 2nd aspect, the content of yttria in the composition is 4.5 mol% or more and less than 5.8 mol%.f y is 3% or more.

[0055] According to the preferred mode of the above-mentioned 2nd aspect, the content of yttria in the composition is 5.8 mol% or more and 7.5 mol% or less.f y is 4% or more.

[0056] According to the preferred mode of the above-mentioned 2nd and 3rd aspects, when the 1st light transmittance of the 1st sintered body, which is produced by calcining the pre-calcined body at 1550°C for 30 minutes, is compared with the 2nd light transmittance of the 2nd sintered body, which is produced by calcining the pre-calcined body at 1550°C for 120 minutes, the 1st light transmittance is 85% or more of the 2nd light transmittance.

[0057] According to the preferred mode of the above-mentioned 5th aspect, 95% or more of the zirconia oxide powder in the mixture is a monoclinic crystal.

[0058] According to the preferred mode of the above-mentioned 5th aspect, in the mixing step, the separately prepared zirconia oxide powder and the stabilizer are mixed.

[0059] According to the preferred mode of the above-mentioned 5th aspect, the method for producing the composition further includes a pulverizing step of pulverizing the mixture so that the average particle diameter becomes 0.06 μm to 0.17 μm.

[0060] According to the preferred mode of the above-mentioned 5th aspect, in the pulverizing step, the average particle diameter is set to be less than 0.13 μm.

[0061] According to the preferred mode of the above-mentioned 5th aspect, the method for producing the composition further includes a drying step of drying the mixture into a granular state by spray drying.

[0062] According to the preferred mode of the above-mentioned 5th aspect, the method for producing the composition does not include a step of calcining the mixture at a temperature of 700°C or more.

[0063] According to the preferred mode of the above-mentioned 6th aspect, in the pre-calcination step, the 1st shaped body is calcined at 800°C to 1200°C.

[0064] According to the preferred mode of the above-mentioned 6th aspect, the method of manufacturing the pre-calcination body does not include a step of calcining the composition at a temperature of 700°C or higher before the pre-calcination step.

[0065] According to the preferred mode of the above-mentioned 7th aspect, the method of manufacturing the sintered body does not include a step of calcining the composition at a temperature of 700°C or higher before the sintering step.

[0066] According to the preferred mode of the above-mentioned 7th aspect, the method of manufacturing the sintered body further includes, before the sintering step, a pre-calcination step of calcining a 1st shaped body at a temperature that does not reach the sintering temperature to produce a pre-calcination body. In the sintering step, the pre-calcination body is calcined as the 1st shaped body.

[0067] According to the preferred mode of the above-mentioned 8th aspect, the method of manufacturing the sintered body further includes, before the sintering step, a 2nd shaping step of shaping the pre-calcination body to produce a 2nd shaped body. In the sintering step, the 2nd shaped body is calcined as the pre-calcination body.

[0068] According to the preferred mode of the above-mentioned 8th aspect, in the sintering step, the holding time at the maximum calcination temperature is 1 hour or less.

[0069] According to the preferred mode of the above-mentioned 8th aspect, in the sintering step, the element of the stabilizer is solid-solved in the zirconia.

[0070] As a 1st embodiment, a composition according to the present disclosure is described. The composition can be a precursor (intermediate product) of a zirconia sintered body and a pre-calcination body.

[0071] The composition contains a zirconia powder and a stabilizer that can suppress the phase transition of the zirconia. The stabilizer preferably can form partially stabilized zirconia. As the stabilizer, oxides such as calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide, cerium oxide (CeO2), scandium oxide (Sc2O3), and the like can be given. The content rate of the stabilizer in the composition, the pre-calcination body, and the sintered body can be determined, for example, by inductively coupled plasma (ICP) emission spectroscopy, fluorescence X-ray analysis, or the like.

[0072] In the composition, the stabilizer is preferably present so that at least a part of the crystals of the zirconia is monoclinic crystals. At least a part of the stabilizer is preferably not solid-solved in the zirconia. That a part of the stabilizer is not solid-solved in the zirconia can be confirmed by, for example, an X-ray diffraction (XRD) pattern. In the XRD pattern of the composition, when a peak derived from the stabilizer is confirmed, the stabilizer not solid-solved in the zirconia is present in the composition. In the case of the total amount of the stabilizer being solid-solved, a peak derived from the stabilizer is not substantially confirmed in the XRD pattern. However, depending on the conditions such as the crystalline state of the stabilizer, even in the case where a peak of the stabilizer is not present in the XRD pattern, the stabilizer can not be solid-solved in the zirconia. In the case where the main crystal system of the zirconia is tetragonal crystals and / or cubic crystals, and a peak of the stabilizer is not present in the XRD pattern, it can be considered that a large part, substantially all, of the stabilizer is solid-solved in the zirconia.

[0073] In the composition of the present disclosure, the entire stabilizer can not be solid-solved in the zirconia.

[0074] Note that, in the present disclosure, the solid-solution of the stabilizer means, for example, that the element (atom) included in the stabilizer is solid-solved in the zirconia.

[0075] From the viewpoint of the strength and the light transmittance of the sintered body produced from the composition of the present disclosure, the stabilizer is preferably yttria. The content of the yttria is preferably 3 mol% or more, more preferably 3.5 mol% or more, and further preferably 4 mol% or more, with respect to the total mol of the zirconia and the yttria. If the content of the yttria is 3 mol% or more, the light transmittance of the sintered body can be improved. In addition, the content of the yttria is preferably 7.5 mol% or less, more preferably 7 mol% or less, more preferably 6.5 mol% or less, and further preferably 6 mol% or less, with respect to the total mol of the zirconia and the yttria. If the content of the yttria is 7.5 mol% or less, the decrease in the strength of the sintered body can be suppressed.

[0076] The presence ratio f of the yttria not solid-solved in the zirconia (hereinafter referred to as "not solid-solved yttria") in the composition y can be calculated based on the following mathematical expression 1. The presence ratio f of the not solid-solved yttria y is preferably more than 0%, more preferably 1% or more, more preferably 2% or more, and further preferably 3% or more. The presence ratio f of the not solid-solved yttria y The upper limit of the presence ratio f of the not solid-solved yttria depends on the content of the yttria in the composition. When the content of the yttria is 7.5 mol% or less with respect to the total mol of the zirconia and the yttria, f y can be set to 15% or less. For example, when the content of the yttria is 3.5 mol% to 4.5 mol%, f ymay be 7% or less. When the content of yttria is 5 mol% to 6 mol%, f y may be 10% or less. When the content of yttria is 5.5 mol% to 6.5 mol%, f y may be 11% or less.

[0077] When the content of yttria in the composition is 3 mol% or more and less than 4.5 mol%, f y is preferably 2% or more, more preferably 3% or more, more preferably 4% or more, further preferably 5% or more. When the content of yttria 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, further preferably 7% or more. When the content of yttria is 5.8 mol% or more and less than 7.5 mol%, f y is preferably 4% or more, more preferably 5% or more, more preferably 6% or more, more preferably 7% or more, further preferably 8% or more.

[0078] [Mathematical Formula 1] In Mathematical Formula 1, I y (111) represents the peak intensity of the (111) plane of yttria in the vicinity of 2θ = 29° in the XRD pattern based on CuKα rays. I m (111) and I m (11-1) represents the peak intensity of the (111) plane and the (11-1) plane of the monoclinic system of zirconia. I t (111) represents the peak intensity of the (111) plane of the tetragonal system of zirconia. I c (111) represents the peak intensity of the (111) plane of the cubic system of zirconia.

[0079] Mathematical Formula 1 described above can also be applied to the calculation of the non-solid-solution existence ratio of the stabilizer other than yttria by substituting I y (111) with other peaks.

[0080] The main crystal system of zirconia in the composition is preferably the monoclinic system. In the composition, the proportion f m is preferably 20% or more, preferably 30% or more, preferably 40% or more, preferably 50% or more, preferably 55% or more, preferably 60% or more, preferably 70% or more, more preferably 80% or more, more preferably 85% or more, more preferably 90% or more, further preferably 95% or more, with respect to the total amount of the monoclinic system, the tetragonal system, and the cubic system. The proportion f mThe ratio f of the monoclinic crystal system can be calculated from the following mathematical expression 2 based on the XRD peaks using CuKα rays. The meanings of the respective symbols in mathematical expression 2 are the same as those in mathematical expression 1. The main crystal system in the composition can contribute to an increase in the shrinkage temperature and a reduction in the sintering time.

[0081] In the composition of the present disclosure, peaks of tetragonal crystals and cubic crystals can not be substantially detected. That is, the ratio f of the monoclinic crystal system m may be set to 100%.

[0082] [mathematical expression 2] When the press-molded body of the composition is calcined at a temperature of 800°C or higher and 1000°C or lower to produce a pre-calcined body, the shrinkage ratio of the press-molded body to the pre-calcined body is preferably 1% or lower with respect to the size of one direction of the press-molded body. Further, when the press-molded body of the composition is calcined at a temperature higher than 1000°C and 1200°C or lower to produce a pre-calcined body, the shrinkage ratio of the press-molded body to the pre-calcined body is preferably 5% or lower with respect to the size of one direction of the press-molded body. However, the press-molded body referred to herein is a molded body obtained by performing press-molding on a zirconia powder at a pressure of 300 kg / cm 2 or higher to further perform CIP treatment at 1700 kg / cm 2 or higher.

[0083] The composition can have the form of a powder. The powder can be a collection of particles. The particles are primary particles and / or secondary particles obtained by agglomeration of primary particles.

[0084] The particles are a collection (agglomerate) of primary particles. When the composition takes the form of particles, in order to distinguish the primary particles and the particles, the expressions "primary particles" and "primary particles constituting the particles" are used hereinafter. The composition of the present disclosure can not have the form of particles. When the composition does not take the form of particles, the "primary particles constituting the particles" refer to the primary particles in the powder. Among the "primary particles constituting the particles", the zirconia particles and the stabilizer particles are included.

[0085] The "primary particles" referred to in the present disclosure refer to particles of the smallest unit of a spherical body. For example, the primary particles refer to spherical bodies observed in a state that the particles are not combined with each other and are separable in an electron microscope. The "secondary particles" referred to in the present disclosure refer to particles in a state of agglomeration of the primary particles observed in an electron microscope. Among the secondary particles, agglomerates obtained by the primary particles being attached in a state that can be broken, and agglomerates observed by the primary particles being fused in a state that cannot be separated from each other to form 1 particle are also included. The secondary particles do not mostly form a spherical body in an electron microscope image, and have a twisted shape.

[0086] The particles constituting the particles are preferably mainly primary particles. For example, the number of primary particles is preferably greater than the number of secondary particles when visually confirming an electron microscope image. For example, of the primary particles (including primary particles constituting secondary particles), 50% or more, preferably 70% or more, and more preferably 80% or more of the primary particles are preferably particles that do not constitute secondary particles when visually confirming an electron microscope image. Secondary particles generally form irregular shapes, and thus if the number of secondary particles increases, the circularity of the particles described later decreases.

[0087] The average particle diameter of the particles constituting the particles is preferably 0.06 μm or more, more preferably 0.08 μm or more, more preferably 0.10 μm or more, and further preferably 0.11 μm or more when measured by a laser diffraction / scattering particle size distribution measurement method. If less than 0.06 μm, sintering is difficult, or even if sintering is possible, the sintered body is white and cloudy. In addition, the average particle diameter is preferably 0.17 μm or less, more preferably 0.15 μm or less, more preferably 0.14 μm or less, and further preferably 0.13 μm or less. If greater than 0.17 μm, the shift temperature described later increases, and is easily affected by temperature unevenness in the calcination furnace. In addition, if the calcination time for sintering is shortened, the light transmittance of the sintered body decreases. The average particle diameter referred to herein means a particle diameter measured without distinguishing between primary particles and secondary particles.

[0088] When the particles or the particles are produced without the calcination step, in order to further improve the light transmittance of the sintered body produced from the particles or the particles, the average particle diameter of the particles constituting the particles is more preferably less than 0.13 μm, more preferably 0.125 μm or less, more preferably 0.12 μm or less, and further preferably 0.115 μm or less.

[0089] The BET specific surface area of the particles constituting the particles is preferably 7.0 m 2 / g or more, more preferably 7.5 m 2 / g or more, and further preferably 8 m 2 / g or more. If less than 7.0 m 2 / g, sintering is difficult, or even if sintering is possible, the sintered body is white and cloudy. In addition, the BET specific surface area is preferably 30 m 2 / g or less, more preferably 25 m 2 / g or less, and further preferably 20 m 2 / g or less. If greater than 30 m 2 / g, the shift temperature described later increases, and is easily affected by temperature unevenness in the calcination furnace. In addition, if the calcination time for sintering is shortened, the light transmittance of the sintered body decreases. The BET specific surface area referred to herein means a specific surface area measured without distinguishing between primary particles and secondary particles.

[0090] Of the zirconia in the zirconia composition, 50% or more, preferably 70% or more, more preferably 80% or more, further preferably 90% or more of the zirconia can take the form of particles.

[0091] When the zirconia composition of the present disclosure does not take the form of particles, the zirconia particles that constitute the powder can have the average particle diameter and the BET specific surface area described above.

[0092] The average particle diameter of the particles in the zirconia composition is preferably 10 μm or more, more preferably 12 μm or more, further preferably 14 μm or more. If the average particle diameter of the particles is less than 10 μm, air is entrapped when the particles are added to the mold, and degassing becomes insufficient during molding, and it can not be possible to produce a molded body that is uniform and dense. In addition, the particles are ejected from the gaps during molding, and it can not be possible to produce a molded body that satisfies the required amount prescribed. The average particle diameter of the particles is preferably 200 μm or less, more preferably 190 μm or less, more preferably 180 μm or less, more preferably 150 μm or less, further preferably 100 μm or less. If the average particle diameter of the particles is greater than 200 μm, voids are easily formed inside the particles. In addition, gaps are easily generated when the particles are added to the mold. Through these phenomena, degassing becomes insufficient during molding, and it can not be possible to produce a dense molded body. In addition, shrinkage during molding becomes large, and it can not be possible to produce a molded body having a desired size. Of the zirconia in the zirconia composition, 50% or more preferably constitutes the particles. The average particle diameter of the particles is preferably measured by a method that does not damage the particles. For example, the average particle diameter of the particles can be measured by a vibration type・low-pile particle size distribution measurement method, or an acoustic vibration sieve type particle size distribution measurement method (for example, using a Seishin Enterprise Co., Ltd. Robot Shifter).

[0093] The sphericity of the particles is preferably high. By increasing the sphericity of the particles, when layers of zirconia powders having different compositions are stacked, mixing at the interface between the layers can be caused. In addition, when a molded body is produced by filling the zirconia powder into a mold, even if the average particle diameters are the same, the filling density can be increased in the case where the sphericity is high. By increasing the filling density, the strength and the light transmittance of the sintered body can be increased. In addition, in the case where the mold has a corner portion, the filling property of the particles in the corner portion can also be increased.

[0094] The sphericity of the particles can be represented by, for example, the circularity based on a projected image, the angle of repose, the unrammed bulk density, the rammed bulk density, and the like.

[0095] The average circularity of the particles in the zirconia composition, based on the projected image, is preferably 0.81 or more, more preferably 0.85 or more, more preferably 0.90 or more, further preferably 0.95 or more. The circularity can be calculated as the ratio of the circumference of a circle equal in area to the particle to the circumference of the particle in the projected image. That is, the circularity can be calculated by the following formula. The average circularity is preferably set as the average of the circularities of 10,000 or more particles.

[0096] Circumference of circle equal in area to particle / Circumference of particle The repose angle of the zirconia composition is preferably 35° or less, more preferably 32° or less, more preferably 28° or less, more preferably 26° or less, further preferably 24° or less. The repose angle can be measured in accordance with JIS R9301-2-2.

[0097] The unrammed bulk density of the zirconia composition is preferably 1.0 g / cm 3 or more, more preferably 1.1 g / cm 3 or more, further preferably 1.2 g / cm 3 or more, further preferably 1.3 g / cm 3 or more. The unrammed bulk density can be measured in accordance with JIS R9301-2-3.

[0098] The rammed bulk density of the zirconia composition is preferably 1.3 g / cm 3 or more, more preferably 1.4 g / cm 3 or more, further preferably 1.5 g / cm 3 or more. The rammed bulk density can be measured in accordance with JIS R9301-2-3.

[0099] The composition can contain an additive other than the zirconia and the yttria. As the additive, pigments (including colorants and fluorescent agents), binders, dispersants, antifoaming agents, alumina (AI2O3), titania (TiO2), silica (SiO2), and the like can be mentioned, for example.

[0100] As the colorant and the like, the oxide of at least one element selected from the group of Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, Zr, Sn, Sb, Bi, Ce, Pr, Sm, Eu, Gd, Tb, and Er can be mentioned, for example. As the fluorescent agent, Y2SiO5:Ce, Y2SiO5:Tb, (Y, Gd, Eu)BO3, Y2O3:Eu, YAG:Ce, ZnGa2O4:Zn, BaMgAl 10 O 17 :Eu, and the like can be mentioned, for example.

[0101] As the adhesive, an organic adhesive can be used. For example, an acrylic-based, an acrylic-based, a paraffin-based, a fatty acid-based, a polyvinyl alcohol-based can be used.

[0102] The composition of the present disclosure can be in a dry state, or in a state containing a liquid or contained in a liquid. For example, the composition can take the form of a powder, a paste, a slurry, or the like. Furthermore, the composition can be a shaped body having a prescribed shape (hereinafter referred to as "1st shaped body").

[0103] The density of the 1st shaped body is preferably 2.75 g / cm 3 More preferably, 2.80 g / cm 3 More preferably, 2.85 g / cm 3 More preferably, 2.90 g / cm 3 Further preferably, 3.00 g / cm 3 or more. The density can be calculated as, for example, (mass of the 1st shaped body) / (volume of the 1st shaped body).

[0104] Generally, the shrinkage rate of the press-molded body to the sintered body is not constant with respect to the calcination temperature, and the shrinkage rate is low up to a certain temperature, but the shrinkage rate becomes high at that temperature. The temperature at which this change in shrinkage rate occurs is described herein as the "change rate temperature". According to the composition of the present disclosure, the change rate temperature can be set to 1050°C or more, preferably 1100°C or more. The change rate temperature can be determined by making a plot of the shrinkage rate with respect to the maximum calcination temperature, as in the examples described later.

[0105] When a plurality of press-molded bodies are simultaneously calcined in one calcination furnace in one batch to produce a plurality of pre-calcined bodies (blocks), the deviation in the shrinkage rate of the press-molded bodies to the pre-calcined bodies is preferably small. If the deviation in the shrinkage rate is large, when the pre-calcined bodies are subjected to molding processing, if the same coefficient is applied to the batch to determine the size of the molding-processed bodies, sintered bodies having the target size cannot be obtained. This is particularly problematic in the case of products such as dental restorations that require high dimensional accuracy. Therefore, blocks in which the shrinkage rate deviates from the allowable range in one batch cannot be used as products, and the yield is reduced.

[0106] According to the composition of the present disclosure, it is possible to reduce the variation in the shrinkage rate in one batch, relative to the calcination temperature (for example, about 1000°C) for manufacturing the pre-calcined block. Generally, the highest calcination temperature for making the pre-calcined body (hereinafter referred to as "pre-calcination temperature") is close to the inflection temperature. Generally, a temperature difference (temperature unevenness) of about 20°C to 50°C occurs in the calcination furnace at the pre-calcination temperature. Therefore, if the inflection temperature is near the pre-calcination temperature, the batch of the composition is strongly affected by this temperature unevenness. That is, in one batch, the pre-calcined bodies located at a low temperature site and the pre-calcined bodies located at a high temperature site have significantly different shrinkage rates. The pre-calcined bodies whose shrinkage rates deviate from the allowable range cannot be made into products, and thus the yield is reduced. On the other hand, according to the composition of the present disclosure, the inflection temperature is high, and thus it is possible to reduce the difference between the inflection temperature and the pre-calcination temperature. Therefore, in one batch, it is possible to reduce the difference in the shrinkage rate between the pre-calcined bodies located at a low temperature site and the pre-calcined bodies located at a high temperature site. Thus, it is possible to reduce the pre-calcined bodies whose shrinkage rates deviate from the allowable range, and to improve the yield. Furthermore, it is possible to increase the number of products that can be calcined at one time, and to improve the production efficiency. Further, according to the composition and the pre-calcined body of the present disclosure, it is possible to make the final product (sintered body) with high dimensional accuracy from any block within one batch. The composition and the pre-calcined body of the present disclosure are useful for making products that particularly require high dimensional accuracy, such as dental products.

[0107] The composition and the pre-calcined body of the present disclosure have further advantages. According to the composition and the pre-calcined body of the present disclosure, it is possible to shorten the calcination time for manufacturing the sintered body without reducing the light transmittance and the strength of the zirconia sintered body to be made. In particular, it is possible to shorten the holding time at the highest calcination temperature for making the sintered body (hereinafter referred to as "sintering temperature") (short-time sintering). Thus, it is possible to improve the production efficiency while reducing the manufacturing cost. Furthermore, when the composition and the pre-calcined body of the present disclosure are applied to dental products, it is possible to shorten the time from the determination of the size of the dental product to be used in treatment to the time when the dental product can be used for treatment, and to reduce the time burden on the patient.

[0108] The composition according to the first embodiment has at least one of the advantages related to the inflection temperature and the short-time sintering. The composition according to the first embodiment preferably has both of the advantages related to the inflection temperature and the short-time sintering.

[0109] As the second embodiment, a method for manufacturing the composition of the present disclosure is described.

[0110] First, a mixture is prepared by mixing zirconia and a stabilizer in a prescribed ratio (mixing step). For example, when the stabilizer is yttria, the mixing ratio can be set to be the same as the above-described content ratio of yttria. Mixing can be performed in a dry manner or in a wet manner. The composition can be pulverized to achieve the above-described average particle diameter and / or BET specific surface area (first pulverization step). The mixing step and the first pulverization step can be performed in the same step. Pulverization can be performed using, for example, a ball mill after dispersing the composition in a solvent such as water (dispersion step). In the case where the steps after the calcination step described later are not performed, in order to increase the sintering temperature and / or to sinter in a short time, the composition is pulverized so that the average particle diameter of the composition is, for example, 0.10 μm to 0.14 μm. The average particle diameter can be measured by a laser diffraction / scattering particle size distribution measurement method. After the mixing step and / or the first pulverization step, the mixture can be dried by a spray dryer or the like to shape the composition into the above-described granular form (first drying step). Thus, the composition of the present disclosure can be prepared.

[0111] In the case where the steps after the calcination step described later are not performed, in the first pulverization step, the average particle diameter of the composition is preferably set to be less than 0.13 μm, more preferably 0.125 μm or less, more preferably 0.12 μm or less, and further preferably 0.115 μm or less. By setting the average particle diameter of the composition to be less than 0.13 μm, the light transmittance of the sintered body can be improved.

[0112] In the case where the steps after the calcination step described later are not performed, before the steps of preparing the pre-calcined body and the sintered body described later, a step of calcining the composition at a temperature of 700°C or higher is preferably not included. Thus, it is possible to simplify the manufacturing steps while suppressing the solid solution of the stabilizer before sintering.

[0113] The zirconia and the stabilizer are preferably prepared separately. For example, the zirconia and the stabilizer are not extracted at the same time (in the same step), and the preparation step (for example, the manufacturing step) of the zirconia and the preparation step (for example, the manufacturing step) of the stabilizer are preferably separate steps. Thus, it is possible to suppress the solid solution of the stabilizer into the zirconia in the manufacturing step of the pre-calcined body described later.

[0114] The following steps can be optionally performed depending on the purpose of use of the composition. For example, after any of the above steps, the mixture and / or the composition can be calcined (calcination (pre-calcination) step). The calcination conditions are as described above, and preferably, the main crystal system of the zirconia after cooling after calcination is not tetragonal and cubic. Further, the calcination conditions are preferably conditions in which at least part of the stabilizer is not solid-solved in the zirconia. For example, the calcination temperature is preferably 700°C or higher, more preferably 800°C or higher. Further, the calcination temperature is preferably 1100°C or lower, more preferably 1000°C or lower, more preferably 980°C or lower, further preferably 950°C or lower. The calcination can be performed in the atmosphere. It is considered that by performing the calcination step, part of the stabilizer is solid-solved in the zirconia, or the stabilizer is easily solid-solved in the sintering step, or the properties of the sintered body are improved.

[0115] After any of the above steps, the composition can be dispersed in a solvent such as water to produce a slurry, and an additive such as a binder, a pigment, or the like can be added to the composition (addition step). The composition can be pulverized to achieve the above-mentioned average particle diameter and / or BET specific surface area (2nd pulverization step). The addition step and the 2nd pulverization step can be performed in the same step. The 2nd pulverization step can be performed in the same manner as the 1st pulverization step. After the addition step and / or the 2nd pulverization step, the mixture can be dried by spray drying with a spray dryer or the like, and the composition can be formed into the above-mentioned granular form (2nd drying step).

[0116] The composition can be formed to produce a 1st formed body (1st forming step). The forming method is not limited to a particular method, and an appropriate method can be appropriately selected depending on the purpose. For example, the composition can be formed by press forming, injection molding, stereolithography, or the like. Further, multi-stage forming can be performed. For example, after the composition is subjected to press forming, CIP treatment can be further performed.

[0117] The above-mentioned additive can be appropriately added in each step.

[0118] According to the composition production method according to the 2nd embodiment, the composition according to the 1st embodiment can be produced. That is, according to the composition production method according to the 2nd embodiment, the composition in which the shift temperature is high, and / or the calcination time for sintering can be shortened can be produced.

[0119] The yttria-doped zirconia powder is generally produced by a coprecipitation method and a hydrolysis method. In the coprecipitation method and the hydrolysis method, a mixture of hydrous zirconia and yttria is produced from zirconium oxychloride and yttrium chloride in the same step, and the mixture is calcined at 800°C to 900°C to produce the yttria-doped (yttria-doped) stabilized zirconia powder. The yttria-doped zirconia is mainly tetragonal and / or cubic. The zirconia powder thus obtained has a particle size of several tens of nm. In order to use the zirconia powder as a raw material for a zirconia sintered body, the calcine is pulverized to a predetermined particle size, and then granulated to produce a composition.

[0120] In the composition produced by such a coprecipitation method or a hydrolysis method, the temperature dependence of the shrinkage in the pre-calcine production temperature region is high. In addition, sufficient light transmittance of the sintered body cannot be obtained in a short calcination time.

[0121] In the production method of the present disclosure, after the zirconia (monoclinic) is produced, the stabilizer (yttria) is mixed separately, and the stabilizer is essentially doped in the zirconia in the sintering step. Thus, the temperature dependence of the shrinkage in the pre-calcine production temperature region can be reduced. In addition, even if sintering is performed for a short time, a sintered body having high light transmittance can be obtained.

[0122] In addition, in the production method of the present disclosure, in the case where the calcining step, the second pulverization step, and the second drying step are not performed, the production cost of the composition can be reduced by greatly reducing the time. In addition, by using the equipment and time for the second pulverization step and the second drying step for the first pulverization step and the first drying step, the production amount per unit time can be doubled. Further, by omitting the second pulverization step and the second drying step, the opportunity of mixing impurities such as dirt in the composition can be reduced.

[0123] As a third embodiment, the zirconia pre-calcine of the present disclosure is described. The pre-calcine can be a precursor (intermediate product) of a zirconia sintered body. In the present disclosure, the pre-calcine can refer to, for example, a substance in which zirconia particles (powder) are agglomerated in a state of not being completely sintered. In particular, the pre-calcine of the present disclosure refers to a substance produced from the composition of the present disclosure. The density of the pre-calcine is preferably 2.7 g / cm 3 The above. In addition, the density of the pre-calcine is preferably 4.0 g / cm 3 More preferably, the above is 3.8 g / cm 3 Further preferably, the above is 3.6 g / cm 3 If it is in this density range, molding processing can be easily performed.

[0124] The contained ratio of zirconia and the stabilizer in the precalcined body is the same as that in the composition before the precalcined body is produced. From the viewpoint of the strength and the light transmittance of the sintered body produced from the precalcined body of the present disclosure, the stabilizer is preferably yttria.

[0125] The non-solubilized proportion of the stabilizer in the precalcined body depends on the calcination temperature at the time of production of the precalcined body, but can be considered to be the non-solubilized ratio in the composition before the precalcined body is produced, for example, as follows. The presence ratio f of the non-solubilized yttria in the precalcined body y can be calculated based on the above mathematical formula 1. The presence ratio f of the non-solubilized yttria in the precalcined body y can be set to be the same as f of the above composition. y

[0126] The presence ratio f of the non-solubilized yttria in the precalcined body y is preferably more than 0%, more preferably 1% or more, more preferably 2% or more, further preferably 3% or more. The upper limit of the presence ratio f of the non-solubilized yttria y depends on the contained ratio of yttria in the precalcined body. When the contained ratio of yttria is 7.5 mol% or less in total of zirconia and yttria, f y can be set to be 15% or less. For example, when the contained ratio of yttria is 3.5 mol% to 4.5 mol%, f y can be set to be 7% or less. When the contained ratio of yttria is 5 mol% to 6 mol%, f y can be set to be 10% or less. When the contained ratio of yttria is 5.5 mol% to 6.5 mol%, f y can be set to be 11% or less.

[0127] When the contained ratio of yttria is 3 mol% or more and less than 4.5 mol% in the precalcined body, f y is preferably 2% or more, more preferably 3% or more, more preferably 4% or more, further preferably 5% or more. When the contained ratio of yttria 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, further preferably 7% or more. When the contained ratio of yttria is 5.8 mol% or more and 7.5 mol% or less, f y is preferably 4% or more, more preferably 5% or more, more preferably 6% or more, more preferably 7% or more, further preferably 8% or more.

[0128] The crystal system of zirconia in the precalcined body depends on the calcination temperature at the time of production of the precalcined body, but the contained proportion of monoclinic crystals can be considered to be the contained proportion of monoclinic crystals in the composition before the precalcined body is produced. The proportion f of monoclinic crystals in zirconia​m The total amount of monoclinic, tetragonal, and cubic crystal systems is preferably 60% or more, more preferably 70% or more, more preferably 80% or more, more preferably 90% or more, and further preferably 95% or more.

[0129] The bending strength of the precalcined body measured according to JIS R1601 is preferably 15 MPa or more in order to ensure a strength capable of mechanical processing. In addition, the bending strength of the precalcined body is preferably 70 MPa or less, and more preferably 60 MPa or less in order to make the mechanical processing easy.

[0130] The bending strength can also be measured according to ISO 6872.

[0131] However, the provisions of JIS R1601 or ISO 6872 refer to changing the size of the test piece to 5 mm x 10 mm x 50 mm. The surface and C face of the test piece are finished with sandpaper of No. 600 along the length direction. The test piece is arranged so that the widest surface faces the vertical direction (load direction). In the bending test measurement, the span is set to 30 mm, and the cross head speed is set to 0.5 mm / minute.

[0132] The precalcined body can contain the above-described additive.

[0133] The precalcined body can be a molded body having a prescribed shape (hereinafter referred to as "second molded body"). For example, the precalcined body can have a disc (circular plate) shape, a cuboid shape, a dental product shape (for example, a crown shape). A dental product (for example, a restoration in the shape of a crown) obtained by machining a precalcined zirconia disc with a CAD / CAM (Computer-Aided Design / Computer-Aided Manufacturing) system is also included in the precalcined body.

[0134] The precalcined body according to the third embodiment can be produced in such a manner that the shrinkage rate of the composition is small. Thus, according to the precalcined body according to the third embodiment, the shrinkage rate from the precalcined body to the sintered body can be equalized, and a sintered body with high dimensional accuracy can be produced.

[0135] According to the precalcined body according to the third embodiment, as described above, even if calcination is performed for a short time, a sintered body with high light transmittance can be produced. Thus, the precalcined body according to the third embodiment has the above-described advantages related to short-time sintering.

[0136] A sintered body produced by calcining the pre-calcined body of the present disclosure at 1550°C for 30 minutes is referred to as a first sintered body. A sintered body produced by calcining the pre-calcined body of the present disclosure at 1550°C for 120 minutes is referred to as a second sintered body. When the light transmittance of the first sintered body is compared with that of the second sintered body (refer to the description below), the light transmittance of the first sintered body is preferably 85% or more, more preferably 90% or more, still more preferably 95% or more, and even more preferably substantially the same as that of the second sintered body.

[0137] The pre-calcined body according to the third embodiment has at least one of the advantages of the dimensional accuracy and the short-time sintering, and preferably both.

[0138] Next, as the fourth embodiment, the production method of the pre-calcined body of the present disclosure is described.

[0139] The pre-calcined body of the present disclosure can be produced by calcining (i.e., pre-calcining) the first molded body produced in the first molding step described above at a temperature at which the zirconia particles do not reach the sintering temperature (pre-calcining step). The calcining temperature is, for example, preferably 800°C or higher, more preferably 900°C or higher, and even more preferably 950°C or higher, in order to surely form a block. In addition, the calcining temperature is, for example, preferably 1200°C or lower, more preferably 1150°C or lower, and even more preferably 1100°C or lower, in order to improve the dimensional accuracy.

[0140] As long as the calcining temperature is such, it can be considered that the solid solution of the stabilizer is not performed.

[0141] The pre-calcined body can be molded to produce a second molded body (second molding step). The molding method is not limited to a particular method, and an appropriate method can be appropriately selected according to the purpose. For example, the zirconia disc also serving as the pre-calcined body can be cut to the shape of a dental product (e.g., a crown-shaped restoration) using a CAD / CAM system, and the second molded body can be produced.

[0142] According to the production method of the pre-calcined body according to the fourth embodiment, the pre-calcined body according to the third embodiment can be produced. According to the fourth embodiment, a pre-calcined body having a small variation in shrinkage can be produced, and / or a pre-calcined body that can be sintered in a short time can be produced.

[0143] As the fifth embodiment, the sintered body of the present disclosure is described. In the present disclosure, the sintered body can refer to a substance obtained by bringing the zirconia particles (powder) to a sintered state. In particular, the sintered body of the present disclosure refers to a substance produced from the composition and / or the pre-calcined body of the present disclosure. The relative density of the sintered body is preferably 99.5% or more. The relative density can be calculated as the proportion of the measured density determined by the Archimedes method to the theoretical density.

[0144] The zirconia sintered bodies disclosed herein include not only sintered bodies obtained by sintering shaped zirconia particles under normal pressure or without pressure, but also sintered bodies obtained by densification through high-temperature and high-pressure treatments such as HIP (Hot Isostatic Pressing).

[0145] The ratio of zirconium oxide and stabilizer in the sintered body is the same as that in the composition and / or pre-calcined body before sintering. Regarding the crystal system of zirconium oxide in the sintered body, the proportion f of the monoclinic crystal system... m Preferably, it is 10% or less, more preferably 5% or less, and even more preferably substantially free of (0%). The crystal system is tetragonal and / or cubic, other than monoclinic.

[0146] Regarding the solid solution ratio of stabilizers in the sintered body, it is preferable that more than 95% of the stabilizers are dissolved in zirconium oxide, and more preferably that substantially all stabilizers are dissolved. The presence rate of undissolved yttrium oxide f y Preferably, it is 5% or less, more preferably 1% or less, and even more preferably substantially all solid solution (0%).

[0147] The light transmittance of the sintered body is preferably 12 or more, more preferably 14 or more, more preferably 15 or more, and even more preferably 16 or more. Here, light transmittance refers to transmittance relative to L. * a * b * The lightness (L) in the color space of the color system (JIS Z8781) * The value was obtained by setting the background of a 1.2 mm thick sample to white. * The value is denoted as the first L. * The value was determined for the first L. * The L value was obtained by setting the background of the sample to black for the same sample. * The value is denoted as the second L. * Value, first L * Subtract the second L from the value * The value obtained is... Regarding the sample preparation method, firstly, the particles (composition) are pressed into shape to achieve a sintered body thickness of 1.2 mm, followed by CIP molding to produce, for example, a circular plate-shaped body with a diameter of 19 mm. Next, the body is calcined under specified calcination conditions to produce a sintered body with a sample thickness of 1.2 mm. Regarding L... * The L value is determined by applying a contact liquid to the surface of the sample and then using a colorimeter (e.g., CE100, analysis software Crystal AI (manufactured by Olinpas)) to measure the L value against a black background and a white background. *The value of the refractive index nD at a measurement wavelength of 589 nm (sodium D line) is preferably 1.60 or more, more preferably 1.65 or more, and even more preferably 1.70 or more. As the contact liquid, a substance having a refractive index nD of 1.60 as measured at a measurement wavelength of 589 nm (sodium D line) can be used, for example.

[0148] The sintered body can contain the above-described additive.

[0149] The sintered body can be a shaped body having a prescribed shape (hereinafter referred to as "a third shaped body"). For example, the sintered body can have a disc (circular plate) shape, a cuboid shape, a dental product shape (for example, a crown shape).

[0150] Next, as the sixth embodiment, a manufacturing method of the sintered body of the present disclosure will be described.

[0151] The sintered body of the present disclosure can be produced (sintering step) by calcining the composition of the present disclosure (including the first shaped body) and / or the pre-sintered body (including the second shaped body) at a temperature at which the zirconia particles reach sintering. The calcination temperature is preferably, for example, 1400°C or higher, and more preferably 1450°C or higher. In addition, the calcination temperature is preferably, for example, 1650°C or lower, and more preferably 1600°C or lower. The temperature increase rate and the temperature decrease rate are preferably 300°C / minute or lower.

[0152] In the sintering step, the holding time at the sinterable temperature (for example, the maximum calcination 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 further 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 calcination time, the decrease in the light transmittance of the produced sintered body can be suppressed. In addition, by shortening the calcination time, the energy cost can be reduced while improving the production efficiency.

[0153] In the sintering step, the holding time at the sinterable temperature (for example, the maximum calcination temperature) can also be set to 25 minutes or less, 20 minutes or less, or 15 minutes or less, for example.

[0154] The temperature increase rate and the temperature decrease rate in the sintering step are preferably set so that the time required for the sintering step is shortened. For example, the temperature increase rate can be set according to the performance of the calcination furnace so that the maximum calcination temperature is reached in the shortest time. The temperature increase rate to the maximum temperature can be set to 10°C / minute or more, 50°C / minute or more, 100°C / minute or more, 120°C / minute or more, 150°C / minute or more, or 200°C / minute or more, for example. The temperature decrease rate is preferably set at a rate at which the sintered body does not generate defects such as cracking. For example, after the heating is completed, the sintered body can be left to cool at room temperature.

[0155] In the production method of the present disclosure, the stabilizer (e.g., yttria) can be considered to be solid-solved in the zirconia oxide in the sintering step.

[0156] The sintered body can be shaped to produce a third shaped body (a third shaping step). The shaping method is not limited to a particular method, and an appropriate method can be appropriately selected according to the purpose. For example, a zirconia oxide block that is also a sintered body is machined into the shape of a dental product (e.g., a restoration in the shape of a crown) using a CAD / CAM system, and the third shaped body can be produced.

[0157] As the seventh embodiment, a dental product of the present disclosure is described. The dental product of the present disclosure has the zirconia sintered body described in the fifth embodiment. The zirconia sintered body can have, for example, a crown shape. The dental product can further include a ceramic material layered on the zirconia sintered body. The ceramic material can be, for example, a ceramic such as a glass material. As the dental product, for example, a restoration (e.g., a ceramic framework, a full-contour crown), a product for orthodontic treatment (e.g., a bracket for orthodontic treatment), a product for dental implants (e.g., an abutment for dental implants) can be given.

[0158] Next, as the eighth embodiment, a production method of a dental product of the present disclosure is described. The dental product can be produced by sintering the composition of the present disclosure (including the first shaped body) and / or the pre-sintered body (including the second shaped body) having a prescribed shape. In addition, the dental product can be produced by machining the sintered body of the present disclosure (including the third shaped body).

[0159] The dental product having a ceramic material can be produced by, for example, a step of applying a slurry containing a ceramic material on the sintered body, and a step of sintering the sintered body on which the ceramic material is applied to bond the ceramic material to the sintered body.

[0160] According to the fifth to eighth embodiments, a sintered body and a dental product having high dimensional accuracy can be obtained, and / or a sintered body and a dental product having high light transmittance can be produced in a short time.

[0161] In addition to the configurations and properties described herein for the composition, the pre-sintered body, the sintered body, and the layered body, it can be considered that they cannot be directly confirmed by analysis or the like at the time of filing of the present application, or it is almost impractical. Therefore, in the case of confirming the configurations or properties other than those described herein, it is considered to be useful to confirm using the production method.

[0162] Hereinafter, examples of the present disclosure are described. The present application is not limited to the following examples. Examples

[0163] [Examples 1 to 4 and Comparative Examples 1 to 3] [Manufacture of composition and XRD measurement] The zirconia composition of the present disclosure was manufactured, and the crystal system of the zirconia and the degree of solid solution of the stabilizer into the zirconia were confirmed. The results are shown in Table 1.

[0164] As the stabilizer, yttria was used. In Examples 1 to 3, the addition rate of yttria was changed, respectively. In Example 4, the proportion of monoclinic crystals was changed. The yttria addition rate shown in Table 1 is the proportion of yttria with respect to the total mol of zirconia and yttria. The step shown in Table 1 indicates the composition obtained in each step described below. f y This was calculated based on the above mathematical formula 1. f m This was calculated based on the above mathematical formula 2.

[0165] The manufacturing method of the composition relating to Examples 1 to 3 shown in Table 1 will be described. First, the zirconia of monoclinic crystals and yttria were combined to manufacture a mixture (mixing step). This zirconia and yttria were manufactured in each independent step. Next, this mixture was added to water to manufacture a slurry, and wet pulverization was performed using a ball mill to mix to an average particle diameter of 0.13 μm (primary pulverization step). The pulverized mixture was noted as the composition of the "primary pulverization" step shown in Table 1. Next, the powder obtained by drying the pulverized slurry using a spray dryer was calcined at 950°C for 2 hours (calcination step). Next, the calcined powder was added to water to manufacture a slurry, and wet pulverization was performed using a ball mill to reach an average particle diameter of 0.13 μm or less (secondary pulverization step). After the binder was added to the pulverized slurry, drying was performed using a spray dryer to manufacture a composition. This dried composition was noted as the composition of the "secondary pulverization" step shown in Table 1.

[0166] Further, as comparative examples, f y and f m of the commercially available partially stabilized zirconia powder were also calculated. The zirconia of Comparative Example 1 was TZ-3YSB-E manufactured by Toho Chemical Industry Co., Ltd. The zirconia of Comparative Example 2 was Zpex manufactured by Toho Chemical Industry Co., Ltd. The zirconia of Comparative Example 3 was Zpex Smile manufactured by Toho Chemical Industry Co., Ltd.

[0167] The composition relating to Example 4 was manufactured by adding the zirconia of monoclinic crystals and yttria in the above mixing step, and adding the composition relating to Comparative Example 1, and the proportion of monoclinic crystals in the composition was further reduced than in Examples 1 to 3.

[0168] In the commercially available zirconium oxide powders of Comparative Examples 1-3, the crystal system of zirconium oxide is basically tetragonal and cubic, with monoclinic crystals accounting for about 50% in some cases. Furthermore, no XRD peaks for yttrium oxide were detected in the powders of Comparative Examples 1-3. Therefore, it can be assumed that yttrium oxide is completely dissolved in zirconium oxide.

[0169] On the other hand, in Examples 1-3, tetragonal and cubic crystallization were partially achieved through the calcination step, but over 90%, and more than 95%, were monoclinic crystals. In Example 4, due to the addition of partially stabilized tetragonal zirconia, approximately 80% were monoclinic crystals. Furthermore, XRD peaks of yttrium oxide were observed in all Examples 1-4. In Example 1, with a low yttrium oxide addition rate, f... y The value is 2.5 or higher and 6 or lower. Furthermore, in Examples 2-4, where the yttrium oxide addition rate is high, f... y The value is between 4 and 10. From the first grinding step to the second grinding step, f y The value decreases, but if we compare the values ​​immediately following the mixing step and immediately following the calcination step, the f value decreases. y The particle size and shape change due to pulverization, therefore, it can be considered that the relative peak of yttrium oxide relative to zirconium oxide decreases. However, the possibility of f being affected by solid solution cannot be denied. y The possibility of a decrease.

[0170] [Examples 5-7 and Comparative Example 4] [Preparation of pre-calcined body, determination of shrinkage rate, and determination of XRD pattern] Pre-calcined blocks were prepared using the compositions of Examples 1-2, 3-2, and 4, as well as Comparative Example 2, and the deviation in dimensional change of each pre-calcined block was measured. First, each composition was subjected to a temperature of 300 kg / cm². 2 Pressed into shape under pressure. Then, the pressed shape is subjected to pressure of 1700 kg / cm². 2Further, the CIP process was performed, and the first molded body described above was produced. The first molded body was calcined to produce a pre-calcined body. The calcination of the first molded body was performed at three set temperatures of 1000°C, 1050°C, and 1100°C. In each calcination, nine first molded bodies having the same size were produced, and the furnace was divided into three sections of upper, middle, and lower, and three first molded bodies were arranged in each section. The diameter of the circular plate was measured for each pre-calcined body produced. Of the nine pre-calcined bodies produced in one calcination, the measured diameters of the pre-calcined body having the largest diameter and the pre-calcined body having the smallest diameter, and the difference between the largest diameter and the smallest diameter are shown in Tables 2 to 4. Further, of the nine pre-calcined bodies, those within ±0.15 mm of the target diameter were judged to be acceptable. The target diameter was set for each example and comparative example according to the composition and the calcination temperature. For example, in Example 5-2, the target diameter was set to 98.20 mm. The number of acceptable products (acceptance rate) in Examples 5 to 7 and Comparative Example 4 is also shown in Tables 2 to 4.

[0171] Table 2 shows the results when the set temperature of the furnace was set to 1000°C. The lowest temperature in the furnace when the set temperature reached 1000°C was 975°C, and the highest temperature was 1025°C. In Examples 5-1 to 7-1, the difference between the largest size and the smallest size could be reduced compared to Comparative Example 4-1. That is, even if there is temperature unevenness in the calcination furnace, the deviation in the shrinkage rate of the pre-calcined bodies calcined at the same time can be reduced. Further, in Examples 5-1 to 7-1, the shrinkage rates of all the pre-calcined bodies could be brought within the allowable range, but in Comparative Example 4-1, one third of the pre-calcined bodies deviated from the allowable range.

[0172] Table 3 shows the results when the set temperature of the furnace was set to 1050°C. The lowest temperature in the furnace when the set temperature reached 1050°C was 1040°C, and the highest temperature was 1060°C. When the set temperature was 1050°C, in Examples 5-2 and 6-2, the deviation in the shrinkage rate could also be reduced compared to Comparative Example 4-2. Further, in Examples 5-2 and 6-2, the shrinkage rates of all the pre-calcined bodies could be controlled within the allowable range, but in Comparative Example 4-2, one third of the pre-calcined bodies deviated from the allowable range. In Example 7-2, one pre-calcined body deviated from the allowable range, but a better result could be obtained compared to Comparative Example 4-2.

[0173] Table 4 shows the results when the set temperature of the furnace was set to 1100°C. The lowest temperature in the furnace when the set temperature reached 1100°C was 1090°C, and the highest temperature was 1100°C. When the set temperature was 1100°C, in Examples 5-3 and 6-3, the deviation in the shrinkage rate could also be reduced compared to Comparative Example 4-3. Further, in Examples 5-3 and 7-3, some deviated from the allowable range, but the acceptance rate could be improved compared to Comparative Example 4-3.

[0174] The average value of the density of each precalcined body was 3.1 g / cm3 3 .

[0175] The XRD pattern was measured using CuKa line for the precalcined body produced in Example 5-2, Example 6-2 and Comparative Example 4-2. Figure 1 The XRD pattern of the precalcined body produced in Example 5-2 is shown in FIG. 5. Figure 2 The XRD pattern of the precalcined body produced in Example 6-2 is shown in FIG. 6. Figure 3 The XRD pattern of the precalcined body produced in Comparative Example 4-2 is shown in FIG. 7.

[0176] If observed Figure 3 , no peak of zirconia of monoclinic crystal was confirmed in the precalcined body in Comparative Example 4-2. Further, no peak of yttria was confirmed. On the other hand, if observed Figure 1 and Figure 2 , peaks of zirconia of monoclinic crystal, tetragonal crystal and cubic crystal were confirmed in the precalcined bodies in Examples 5-2 and 6-2, and the peak of monoclinic crystal was higher in intensity. Further, in either precalcined body, a peak of yttria was also confirmed near 29.4° in 2Θ (peak No. 6 in FIG. 5, Figure 1 peak No. 5 in FIG. 6), and it was considered that part of yttria was not solid-solved in zirconia in the precalcined body. Figure 2

[0177] [Examples 8 to 11 and Comparative Examples 5 to 8] [Measurement of change in shrinkage rate with respect to calcination temperature] ​The pre-calcined bodies were produced under conditions where the calcination temperature was different, and the shrinkage in each of the pre-calcined bodies was measured. In Example 8, the composition of Example 1-1 was directly used as a raw material. In Example 9, yttria was added to the composition of Example 1-1 so that the total content of yttria would be 6 mol% and the resultant was mixed to be used as a raw material. That is, the non-solubilized yttria in the composition of Example 1-1 was increased. In Example 10, the composition of Example 3-1 was directly used as a raw material. In Example 11, zirconia not containing yttria was added to the composition of Example 3-1 so that the content of yttria would be 4 mol% and the resultant was mixed to be used as a raw material. In Comparative Example 5, the composition of Comparative Example 1 was directly used as a raw material. In Comparative Example 6, the composition of Comparative Example 2 was directly used as a raw material. In Comparative Example 7, yttria was added to the composition of Comparative Example 1 so that the total content of yttria would be 6 mol%, and the resultant was mixed and a pulverization step was performed once to be 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 would be 6 mol%, and the resultant powder was used as a raw material, which was subjected to the above-mentioned mixing step to the pulverization step twice.

[0178] First, in the same manner as in Examples 1 to 3, the first molded body was produced. The first molded body was changed in the maximum calcination temperature by 50°C in the range of 950°C to 1200°C to produce a pre-calcined body, and the shrinkage in each of the pre-calcined bodies was measured. In each of the examples, three samples were produced, and were placed in the same position in the calcination furnace so as not to be affected by the temperature unevenness in the calcination furnace. The size of the first molded body was the same as in the above-mentioned Examples 5 to 7. The shrinkage was calculated from the following formula, and was obtained as an average of three samples. The results are shown in Table 5. Further, based on the results shown in Table 5, a graph in which the shrinkage with respect to the calcination temperature was plotted was shown in FIG. 1. Figure 4 .

[0179] Shrinkage (%) = {(diameter of the first molded body) - (diameter of the pre-calcined body)} / (diameter of the first molded body) x 100 When the XRD pattern of the pre-calcined body produced in Example 8 to 11 was measured, the main crystal system of the zirconia was monoclinic crystal. Further, it was confirmed that the peak of yttria was present.

[0180] If the observation Figure 4the shrinkage rate becomes high from around a calcination temperature of 1100°C. That is, the change temperature can be considered to be about 1100°C. Therefore, as shown in Comparative Example 4, the composition involved in the comparative example has a significantly different shrinkage rate (high shrinkage rate) depending on the calcination temperature in the range of 1000°C to 1100°C, and thus, a pre-calcined body having a different shrinkage amount is produced due to temperature unevenness in the calcination furnace. On the other hand, the composition according to the present disclosure, as shown in Examples 5 to 7, has almost the same shrinkage rate (low shrinkage rate) in the range of 1000°C to 1100°C. Therefore, even if temperature unevenness occurs in the calcination furnace, a pre-calcined body having a uniform shrinkage amount can be produced.

[0181] The crystal system of zirconia in the compositions of Comparative Examples 5 to 8 was tetragonal crystal and cubic crystal, and monoclinic crystal could not be substantially detected. In Comparative Examples 5 and 6, no yttria that was not solid-solved was present in the composition. In Comparative Examples 7 and 8, yttria was added to the composition so that yttria that was not solid-solved was present. On the other hand, in the compositions of Examples 8 to 11, the crystal system of zirconia was mainly monoclinic crystal, and yttria that was not solid-solved was present. It can thus be considered that if a pre-calcined body is produced from a composition in which monoclinic crystal is predominant, the change temperature can be increased.

[0182] [Example 12 and Comparative Example 9] [Measurement of light transmittance with respect to calcination time] A sintered body was produced using the composition (pre-calcined body) according to the present disclosure, and the relationship between the holding time at the maximum temperature and the light transmittance was investigated. In Example 12, the composition of Example 3-2 was used. First, a shaped body was produced to obtain a sintered body having a thickness of 1.2 mm, and the shaped body was calcined at 1000°C for 2 hours to produce a pre-calcined body. Next, a sintered body was produced by calcining the sample (pre-calcined body) at a maximum temperature of 1550°C for 120 minutes. Furthermore, the light transmittance of the sintered body was measured. Next, for the samples produced in the same manner, a sintered body was produced by setting the holding time at the maximum temperature to 30 minutes at a maximum calcination temperature of 1450°C, 1500°C, 1550°C, and 1600°C, and the light transmittance was measured for each sintered body. The heating rate and the cooling rate were the same in the 30-minute calcination and the 120-minute calcination. The change in the light transmittance of the sintered body calcined at the maximum temperature for 30 minutes with respect to the light transmittance of the sintered body calcined at the maximum temperature for 120 minutes was calculated as the change rate. As a comparative example, the same test was performed using the composition of Comparative Example 3. The results are shown in Table 6. A graph based on the change rates shown in Table 6 is shown in FIG. 6. Figure 5 .

[0183] The light transmittance was measured using a color difference meter CE100 and analysis software Crystal Eye (Olympus Corporation) and is represented by the value obtained by subtracting the second L value from the first L value. * a * b * The L value of the lightness (color space) in the colorimetric system (JIS Z8781) was calculated. The L value obtained by measuring the sample with the background set to white was recorded as the first L value, and the L value obtained by measuring the same sample with the background set to black was recorded as the second L value. The value obtained by subtracting the second L value from the first L value was recorded as the value representing the light transmittance. The measurement surface of the sample was coated with a contact liquid having a refractive index nD of 1.60. * * * * * * * * The value obtained by subtracting the second L value from the first L value was recorded as the value representing the light transmittance. The measurement surface of the sample was coated with a contact liquid having a refractive index nD of 1.60.

[0184] Generally, if the calcination temperature is increased, the light transmittance of the sintered body can be increased. However, in Comparative Example 9, in the calcination at the highest temperature for 30 minutes, even if the calcination temperature is increased, the transparency cannot be increased, and is about 80% of the light transmittance at 120 minutes of calcination. On the other hand, in Example 12, the light transmittance equivalent to that at 120 minutes of calcination can be ensured even in the calcination for 30 minutes. At the highest calcination temperature of 1450°C, it is also possible to be more than 85% of the light transmittance at 120 minutes of calcination, and at the highest calcination temperature of 1500°C or higher, it is possible to be more than 95%, almost 100%, of the light transmittance at 120°C of calcination. Thus, according to the composition of the present disclosure, it is possible to shorten the calcination time. Thus, it is possible to increase the production efficiency of the sintered body while reducing the energy cost. Furthermore, when a dental restoration is produced using the composition and the pre-calcined body of the present disclosure, it is possible to reduce the time burden on the patient.

[0185] The crystal system of the composition used in Comparative Example 9 was tetragonal and cubic crystals, and monoclinic crystals could not be detected in essence. It can be considered that yttria is entirely solid-solved in zirconia. The composition of Comparative Example 3 used in Comparative Example 9 became a granular state, and the average particle diameter could not be measured, but if it is inferred from Comparative Example 10, it can be considered to be 0.7 μm or more. On the other hand, in the composition of Example 3-2 used in Example 12, the crystal system of zirconia was mainly monoclinic, and yttria was not solid-solved. The average particle diameter was 0.13 μm. It can be considered that any of these differences affects whether or not it is possible to sinter for a short time.

[0186] ​​​​​​​In the XRD pattern of the sintered body produced in Example 12, the monoclinic crystal peak of zirconia was not detected. In addition, the peak of yttria was not detected either. From this, it can be considered that by the calcination for sintering, while the yttria was solid-solved in the zirconia, the zirconia was shifted from the monoclinic crystal phase to the cubic crystal.

[0187] [Examples 13-14 and Comparative Examples 10-12] [Regarding the effects due to the non-solid-solved yttria and the particle size] Experiments were conducted on the behavior in the case where the particle size was reduced while the non-solid-solved yttria was present in the composition of Comparative Example 1. The compositions of Examples 13 and 14 were the same as those of Examples 3-1 and 3-2. The composition of Comparative Example 10 was the same as that of Comparative Example 1, but one pulverization step was performed to the extent of disintegrating the particles. The composition of Comparative Example 11 was subjected to the above-described one pulverization step to the same extent of particle size as the composition of Example 3 after adding yttria to the composition of Comparative Example 1 so that the content of yttria reached 6 mol%. The composition of Comparative Example 12 was a substance obtained by further performing the above-described calcination step and two pulverization steps on 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 Z8830 (2013). The average particle size was measured using a laser diffraction / scattering type particle size distribution measuring method for the powder before the particles were produced. The "1100°C shrinkage" and the "1150°C shrinkage" were measured in the same manner as in the above-described Examples 8-11. The "pass / fail of light transmittance" was visually determined whether the sintered body produced from the pre-calcined body at the maximum calcination temperature of 1550°C for 30 minutes had high light transmittance or not. A determination of A indicates that the sintered body had the same light transmittance as the sintered body at the maximum temperature for 2 hours, and a determination of B indicates that the sintered body had lower light transmittance than the sintered body at the maximum temperature for 2 hours.

[0188] The average particle size of Comparative Example 10, that is, the composition of Comparative Example 1, had a particle size of 0.67 μm, which was larger than the particle size of the composition of the present disclosure. In addition, the shrinkage at the time of pre-calcination became high as shown in Comparative Example 5. In Comparative Example 11, the non-solid-solved yttria was present in the composition of Comparative Example 1. In addition, the average particle size of the composition of Comparative Example 11 reached the same extent as that of Examples 13 and 14. However, the shrinkage was high in both, and the composition was likely to be affected by the temperature unevenness of the calcination furnace. In addition, in the sintering using short-time calcination, sufficient light transmittance could not be obtained. In Comparative Example 12, the yttria added additionally was considered to be solid-solved in the zirconia by the calcination step. In addition, the phase shift from the monoclinic crystal to the tetragonal crystal and the cubic crystal was performed by the calcination step. However, Comparative Example 11 reached the same results as Comparative Example 12.

[0189] The BET specific surface area of ​​the compositions in Examples 13 and 14 is 9 m². 2 / g~10m 2 / g. The average particle size is 0.11μm~0.13μm. The shrinkage rates of Examples 13 and 14 are as low as those shown in Examples 8~11. Furthermore, even in sintering using short calcination times, sufficient light transmittance cannot be obtained. Therefore, it can be considered that the main crystal system of zirconium oxide in the composition needs to be monoclinic. In addition, f y It is also possible that a higher degree of preference is preferred.

[0190] [Examples 15-21 and Comparative Examples 13-16] [Regarding the impact of particle size and BET specific surface area] Compositions with different average particle sizes were prepared, and the above-described tests were performed on each composition. The yttrium oxide content of the composition was 6 mol%. The compositions of Examples 15-21 and Comparative Examples 15-16 were prepared by hydrolysis. The composition of Comparative Example 13 was prepared by hydrothermal synthesis. The composition of Comparative Example 14 was prepared by plasma melting. The average particle size of the compositions of Examples 15-21 and Comparative Examples 15-16 was determined using a laser diffraction / scattering particle size distribution method. The average particle size of the compositions of Comparative Examples 13 and 14 was calculated from the BET specific surface area by assuming each particle was a true sphere. The BET specific surface area of ​​the compositions of Examples 15-21 and Comparative Examples 13-16 was determined according to JIS Z8830 (2013). Table 8 shows the results. "Whether sintering is acceptable" refers to the result of the test on whether sintering is possible in calcination at 1550°C. Judgment A indicates that sintering is possible, judgment B indicates that the product is cloudy, and judgment C indicates that sintering is not possible. The “shrinkage test pass rate” is the same as the pass rate shown in Examples 5-7, which is the pass rate when the pre-calcined body is made at 1100°C. The “transmittance change rate” is the same as the change rate shown in Example 12, which is the change rate when the sintered body is made at the highest calcination temperature of 1550°C.

[0191] Average particle size 0.08μm~0.15μm, BET specific surface area 7m² 2 / g~28m 2 Good results were obtained in Examples 15-21 with a particle size of / g. In particular, good results were obtained in Examples 16-20. On the other hand, in Comparative Examples 13 and 14, the average particle size was too small, so it can be considered that sufficient sintering was not possible. Therefore, it can be considered that the average particle size is preferably greater 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 is considered to be preferably 30 m².2 / g or less, more preferably 20 m 2 / g or less. In addition, in Comparative Examples 15 and 16, both the shrinkage test pass rate and the light transmittance change rate became low. In particular, if Comparative Example 21, Comparative Example 15, and Comparative Example 16 are compared, the shrinkage test pass rate and the light transmittance change rate decrease as the average particle diameter becomes larger (as the BET specific surface area becomes smaller). Thus, the average particle diameter and / or the BET specific surface area can possibly have an influence on the variable temperature and short-time sintering. The average particle diameter can be considered to be preferably less than 0.18 μm, more preferably 0.15 μm or less, and further preferably 0.14 μm or less. The BET specific surface area can be considered to be preferably 6.5 m 2 / g or more, more preferably 7 m 2 / g or more, further preferably 8 m 2 / g or more.

[0192] [Example 22] [Observation using an electron microscope] The shape of the particles of Example 3-2 and Comparative Example 1 was observed using a field emission scanning electron microscope (FE-SEM). In addition, the shape of the particles that constitute the particles was also observed. Figure 6 In FIG. 2, an electron microscope photograph of the particles of Example 3-2 is shown. Figure 7 In FIG. 3, an electron microscope photograph of the particles that constitute the particles of Example 3-2 is shown. Figure 8 In FIG. 4, an electron microscope photograph of the particles of Comparative Example 1 is shown. Figure 9 In FIG. 5, an electron microscope photograph of the particles that constitute the particles of Comparative Example 1 is shown.

[0193] Figure 6 In the particles shown in FIG. 1, the shape of the particles was observed to be spherical (true spherical) and it was found that the sphericity (circularity) was high. Figure 7 In the particles that constitute the particles shown in FIG. 1, a large number of the particles were observed to be primary particles that were separable and the secondary particles that were obtained by agglomeration of the primary particles were few. That is, the particles were mainly composed of primary particles. Figure 6 In the particles shown in FIG. 1, the shape of the particles was observed to be spherical (true spherical) and it was found that the sphericity (circularity) was high. Figure 8 In the particles shown in FIG. 1, the shape of the particles was observed to be spherical (true spherical) and it was found that the sphericity (circularity) was high. Figure 9 In the particles that constitute the particles shown in FIG. 1, a large number of the particles were observed to be primary particles that were separable and the secondary particles that were obtained by agglomeration of the primary particles were few. That is, the particles were mainly composed of primary particles. Figure 8The particles shown are mainly composed of twisted secondary particles. Therefore, it can be considered that the average particle diameter of Comparative Example 1 is large. For example, from the above-described Comparative Example 10, it can be considered that the particles of Comparative Example 1 are formed of constituent particles of at least about 0.7 μm or more, although the particles constituting the particles can be pulverized into fine particles when the particles are broken. Further, it can be considered that since the particles of Comparative Example 1 are composed of twisted secondary particles, a difference in sphericity of the particles is generated.

[0194] [Example 23] [Measurement of Bending Strength of Pre-Calcined Body] The composition of Example 3-2 was calcined at 1100°C to produce a pre- calcined body, and when the bending strength was measured under the conditions of JIS R1601 described above, it was 35 MPa.

[0195] [Examples 24-25] [Effect due to Yttria Addition Rate] In Example 13, a test was performed using the composition of Example 3-1, but in Examples 24-25, the same test as in Example 13 was performed also with respect to the compositions of Examples 1-1 and 2-1, which differ in the yttria addition rate. Table 10 shows the results. The measurement methods of the respective measured values and the evaluation criteria were the same as in Example 13.

[0196] From a comparison of Examples 13-14 and Comparative Examples 10-12 shown in Table 8, it can be seen that in Examples 24 and 25, the shrinkage at 1100°C and the shrinkage at 1150°C can be made to be low values. Further, even in sintering using short-time calcination, sufficient light transmittance can be obtained. From this, it can be considered that the shrinkage at the time of production of the pre-calcined body and the light transmittance at the time of short-time sintering depend on the yttria addition rate. Therefore, the yttria addition rate can be selected to a desired value in accordance with the light transmittance, strength, etc. of the resulting sintered body.

[0197] In Examples 24 and 25, no effect due to the BET specific surface area could be confirmed.

[0198] [Examples 26-35] [Effect on Light Transmittance due to Particle Diameter] Based on the compositions of Example 2-1 and Example 2-2, the time of the first pulverization was adjusted to produce compositions having different average particle diameters from those of Example 2-1 and Example 2-2. The compositions of Examples 26 to 30 were the same as the composition of Example 2-1 except for the average particle diameter. The compositions of Examples 31 to 35 were the same as the composition of Example 2-2 except for the average particle diameter. The compositions of each example were calcined at 1000°C to produce a pre-calcined body, and a sintered body produced by calcining the pre-calcined body at a maximum calcination temperature of 1550°C for 15 minutes and a sintered body produced by calcining the pre-calcined body for 30 minutes, and the light transmittance was measured for each sintered body by the same method as Example 12. The temperature increase rate was set to the maximum rate of the calcination furnace, 150°C / minute. The cooling was set to the cooling by standing at room temperature. The results are shown in Table 11. The measured values shown in Table 11 are the average values of 3 measurements. The change rate shown in Table 11 is the change rate from the measured value of the light transmittance in Example 26 in the case of Examples 27 to 30, and is the change rate from the measured value of the light transmittance in Example 31 in the case of Examples 31 to 35.

[0199] If the sintered body produced by maintaining the maximum calcination temperature for 15 minutes is compared with the sintered body produced by maintaining the maximum calcination temperature for 30 minutes, the light transmittance in any one of Examples 26 to 35 hardly changes. Furthermore, the light transmittance obtained is also a value that does not change from the light transmittance of the sintered body obtained by maintaining the maximum calcination temperature for 2 hours. From this, it is known that the composition and the pre-calcined body of the present disclosure can also be sintered in a very short time of 15 minutes.

[0200] In Examples 31 to 35 based on the composition of Example 2-2, the light transmittance of the sintered body of Example 35 slightly decreased, but no significant change in the light transmittance was observed. That is, in the sintered body produced from the composition that has undergone the above-mentioned calcination step and the second pulverization step in the composition production step, no dependency of the light transmittance on the average particle diameter of the composition could be confirmed. However, in Examples 26 to 30 based on the composition of Example 2-1, a tendency of a decrease in the light transmittance was observed in the sintered body produced from the composition having an average particle diameter of 0.13 μm or more, as compared with the sintered body produced from the composition having an average particle diameter of less than 0.13 μm. From this, it is considered that the sintered body produced in Examples 29 and 30 also has a light transmittance sufficient for applications to dental restorative materials, for example, but when the sintered body is produced from the composition that has not undergone the above-mentioned calcination step and the second pulverization step, in the case where the light transmittance of the sintered body is desired to be further improved, the average particle diameter of the composition is set to less than 0.13 μm, preferably 0.125 μm or less, more preferably 0.120 μm or less, further preferably 0.115 μm or less.

[0201] [Example 36] [Direct sintering of the composition] The first molded body made of the composition of Examples 2-1 and 2-2 was sintered at a maximum temperature of 1550°C for 30 minutes without a pre-sintered body, thereby making a sintered body. Either sintered body had the same light transmittance as the sintered body made via a pre-sintered body. Thus, it was confirmed that a sintered body could be directly made from the composition of the present disclosure even without a pre-sintered body.

[0202] The composition, the pre-sintered body, and the sintered body of the present disclosure and the manufacturing method thereof are explained based on the above-described embodiments and examples, but are not limited to the above-described embodiments and examples, and various modifications, changes, and improvements of each disclosed element (including the elements described in the claims, the specification, and the drawings) based on the basic technical idea of the present disclosure can be included within the scope of the present disclosure. Further, various combinations, substitutions, or selections of each disclosed element can be made within the scope of the claims of the present disclosure.

[0203] Further objects, purposes, and modes (including modified modes) of the present disclosure are also apparent from the entire disclosure of the present disclosure including the claims.

[0204] For the numerical ranges recited herein, even if not otherwise stated, any numerical value or range encompassed therein is to be interpreted as being specifically recited herein.

[0205] Industrial applicability The composition, the pre-sintered body, and the sintered body of the present disclosure and the manufacturing method thereof can be used for dental materials such as restorations, ferrules, optical fiber connecting members such as sleeves, various tools (e.g., crushing balls, grinding tools), various components (e.g., screws, nuts), various sensors, electronic components, ornaments (e.g., watch bands), and the like. When the composition, the pre-sintered body, and the sintered body are used for dental materials, they can be used for, for example, crowns, bracket workpieces, dental crowns, dental crown bridges, abutments, implants, implant bolts, implant fixtures, implant bridges, implant bars, brackets, denture beds, inlays, dental cases, coverings, orthodontic wires, stacked patches, and the like.

Claims

1. A pre-calcined body, which is produced by calcining a press-molded body of a composition at 800°C to 1200°C, and which does not include a step of calcining the composition at a temperature of 700°C or higher before the pre-calcining step, wherein the composition containing: 55% or more of a zirconia powder that is a monoclinic crystal, and a stabilizer, the stabilizer being yttria, 3 mol% to 7.5 mol% of yttria relative to the total mol of zirconia and yttria, the average particle diameter of the zirconia particles and the particles of the stabilizer being 0.06 μm to 0.117 μm, at least a portion of the stabilizer being not solid-solved in the zirconia, The composition has an f calculated based on Mathematical Formula 1 below y is 1% or more, wherein I y (111) represents the peak intensity of the (111) plane of yttrium oxide in the X-ray diffraction pattern using CuKa line, I m (111) and I m (11-1) represents the peak intensity of the (111) plane and the (11-1) plane of the monoclinic system of zirconium oxide in the X-ray diffraction pattern, I t (111) represents the peak intensity of the (111) plane of the tetragonal system of zirconium oxide in the X-ray diffraction pattern, I c (111) represents the peak intensity of the (111) plane of the cubic crystal system of zirconium oxide in the X-ray diffraction pattern, [mathematical formula 1] 。 2. The precalcined body of claim 1, wherein, The composition has a BET specific surface area of 7.5 m 2 / g~25m 2 / g.

3. The precalcined body according to claim 1 or 2, wherein, 80% or more of the zirconia in the composition being a monoclinic crystal.

4. The precalcined body according to any one of claims 1 to 3, wherein, the average particle diameter being 0.08 μm to 0.117 μm.

5. The precalcined body according to any one of claims 1 to 4, wherein, the average particle diameter being 0.10 μm to 0.117 μm.

6. The precalcined body according to any one of claims 1 to 5, wherein, the composition having a peak of yttria in an X-ray diffraction pattern.

7. The precalcined body according to any one of claims 1 to 6, wherein, The composition has an f calculated based on Mathematical Formula 1 below y is 2% or more.

8. The precalcined body according to any one of claims 1 to 7, wherein, The f y is 15% or less.

9. The precalcined body according to any one of claims 1 to 6, wherein, the content of yttria in the composition being 3 mol% or more and less than 4.5 mol%, The f y is 2% or more.

10. The precalcined body according to any one of claims 1 to 6, wherein, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more and less than 5.8 mol%, the content of yttria in the composition being 4.5 mol% or more The f y is 3% or more.

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