Method for manufacturing calcined bodies and sintered bodies

Abstract

To provide a method for producing a sintered compact satisfying translucency and mechanical strength required as a dental prosthetic material, especially a denture for front teeth.SOLUTION: In the method for producing a sintered body, the ratio [%] of the total light transmission measured according to JISK7361 1 when the sintered body is heated from ambient temperature to 1050 °C at a heating rate of 250 °C / min and from 1050 °C to 900 °C at a heating rate of 50 °C / min, held at a firing temperature of 1580 °C for 8 minutes, and then cooled to 1500 °C at 60 °C / min in an air atmosphere to the total light transmission measured according to JISK7361 1 when the sintered body is heated from ambient temperature to 600 °C at a heating rate of 1580 °C / hr in an air atmosphere and fired at a firing temperature of 2 hours is 91% or more. A calcined body is used.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a powder composition mainly composed of zirconia, a calcined body, a sintered body, and a method for producing the same. [Background technology]

[0002] Sintered bodies with zirconia as the matrix (base material), used in dental prosthetic materials such as crowns and bridges, are required to have aesthetics equivalent to natural teeth. To meet this requirement, improving the translucency of sintered bodies by increasing the content of stabilizing elements is being investigated (Patent Document 1).

[0003] However, sintered bodies with zirconia as the matrix experience a significant decrease in mechanical strength as the content of stabilizing elements increases. In contrast, a sintered body has been disclosed that, by including crystal grains with different stabilizing element content in the sintered body, can satisfy the high mechanical strength required for dental prosthetics, even at stabilizing element content levels that would normally cause a decrease in mechanical strength (Patent Document 2).

[0004] On the other hand, the sintered bodies described in Patent Documents 1 and 2 are manufactured by sintering that requires a holding time of 2 hours at the maximum temperature and 7 hours or more for heating, holding, and cooling (hereinafter also referred to as "normal sintering"). Therefore, the manufacture of these sintered bodies required a long sintering time.

[0005] In recent years, dental treatment using sintered bodies produced using a sintering method that requires less time than conventional sintering—so-called short-time sintering—is being investigated. This is known as chairside treatment. Chairside treatment is expected to reduce the burden of hospital visits for patients.

[0006] Patent Document 3 discloses a sintered body obtained by short-time sintering, in which the matrix is ​​zirconia with a stabilizing element content of 4 mol% to 6 mol% and contains undissolved yttria. Patent Document 4 also discloses a sintered body obtained by short-time sintering, in which the matrix is ​​zirconia with a contrast ratio of 0.68 to 0.70. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2015-143178 [Patent Document 2] Japanese Patent Application Publication No. 2021-059489 [Patent Document 3] International Publication No. 2018 / 056330 [Patent Document 4] Japanese Patent Publication No. 2020-033338 [Overview of the project] [Problems that the invention aims to solve]

[0008] Because it contains undissolved yttria, the sintered body described in Patent Document 3 does not have sufficient mechanical strength. Furthermore, in Patent Document 4, even when a sintered body with a high yttria content is produced by short-time sintering, the resulting sintered body does not have the translucency to be used as an anterior denture, and moreover, its translucency was about the same as that of a sintered body with an yttria content of 4 mol% obtained by normal sintering. The present disclosure aims to provide at least one of a powder composition and a calcined body, as well as a method for producing them, in which a sintered body that satisfies the translucency and mechanical strength required for dental prostheses, particularly anterior dentures, can be obtained by short-time sintering using zirconia with a high content of stabilizing elements as the matrix. [Means for solving the problem]

[0009] The inventors investigated the sintering of powders and calcined bodies using zirconia with a high content of stabilizing elements as a matrix. As a result, they found that even when applying short-time sintering, it is difficult to obtain sintered bodies with the same translucency as those obtained by normal sintering, or even sintered bodies with properties suitable for use as anterior dentures, when using powders and calcined bodies with a high content of zirconia as a matrix. Furthermore, the inventors found that the sintering behavior in the first half of the sintering process has a significant influence on densification in short-time sintering.

[0010] Based on these findings, we focused on the surface activity of each particle constituting the powder and calcined body. As a result, we conceived the idea of ​​coexisting particles with different surface activities in a specific relationship and changing the state of the interface between these particles. We found that this allows control of the sintering behavior in the first half of the sintering process. Consequently, we have completed the powder composition and calcined body of this disclosure, which, even when applying a sintering method applicable to chairside treatment, can produce a sintered body with a zirconia matrix that has a high content of stabilizing elements and that satisfies the translucency required for dental prostheses, particularly anterior dentures.

[0011] In other words, the present invention is as claimed, and the gist of this disclosure is as follows. [1] Contains two or more stabilized zirconia with different stabilizing element content, wherein the stabilizing element content is greater than 4.0 mol% and less than or equal to 5.8 mol%, and the rate of change of thermal shrinkage per unit temperature at 1300°C is 0.07%°C. ―1 A powder composition characterized by the following, and further, having a content of stabilizing elements in the stabilized zirconia of 8.0 mol% or less. [2] The powder composition according to [1] above, wherein the stabilized zirconia comprises a first stabilized zirconia having a content of 1.0 mol% or more and 5.0 mol% or less of stabilizing elements, and a second stabilized zirconia having a content of 3.0 mol% or more and 8.0 mol% or less of stabilizing elements. [3] The rate of change of thermal contraction per unit temperature at 1500°C is 0.02%°C. ―1The powder composition described above in [1] or [2]. [4] The powder composition according to any one of [1] to [3] above, wherein the stabilizing element is one or more selected from the group consisting of yttrium, calcium, and magnesium. [5] BET specific surface area is 8m 2 / g or more 13m 2 A powder composition according to any one of the above [1] to [4], wherein the amount is less than or equal to / g. [6] The powder composition according to any one of [1] to [5] above, wherein the proportion of tetragonal and cubic crystals in the crystalline phase is 65% or more. [7] Contains two or more stabilized zirconia with different stabilizing element content, wherein the stabilizing element content is greater than 4.0 mol% and less than or equal to 5.8 mol%, and the rate of change of thermal shrinkage per unit temperature at 1300°C is 0.07%°C. ―1 A calcined body characterized by the following, and further, the content of the stabilizing element in the stabilized zirconia being 8.0 mol% or less. [8] The calcined body according to [7] above, wherein the stabilized zirconia comprises a first stabilized zirconia having a content of 1.0 mol% or more and 5.0 mol% or less of stabilizing elements, and a second stabilized zirconia having a content of 3.0 mol% or more and 8.0 mol% or less of stabilizing elements. [9] The rate of change of thermal contraction per unit temperature at 1500°C is 0.02%°C. ―1 The above-mentioned incinerated body as described in [7] or [8].

[10] The calcined body according to any one of [7] to [9] above, wherein the stabilizing element is one or more selected from the group consisting of yttrium, calcium, and magnesium.

[11] A calcined body according to any one of [7] to

[10] above, wherein the proportion of tetragonal and cubic crystals in the crystalline phase is 75% or more. A method for producing a sintered body, characterized by using a powder composition according to any one of [1] to [6] above, or a calcined body according to any one of [7] to

[11] above.

[13] A sintered body obtained by sintering any one of the powder compositions described in [1] to [6] above.

[14] A sintered body in which any one of the calcined bodies described in [7] to

[11] above has been sintered.

[15] A sintered body characterized by having a matrix of zirconia containing a stabilizing element, wherein the content of the stabilizing element is greater than 4.0 mol% and less than or equal to 5.8 mol%, the average grain size is 2.5 μm or less, the grain size difference is 0.10 μm or less, and the tetragonal prime phase ratio is 70% or more. [Effects of the Invention]

[0012] The present disclosure aims to provide at least one of the following: a powder composition and a calcined body, and a method for manufacturing the same, which use zirconia with a high content of stabilizing elements as a matrix, and which can be obtained by short-time sintering to produce a sintered body that satisfies the translucency required for dental prostheses, particularly anterior dentures. [Brief explanation of the drawing]

[0013] [Figure 1] This is an example of a TEM observation image used in STEM-EDS measurements. [Figure 2] This is an example of a TEM observation image used in STEM-EDS measurements. [Figure 3] This graph shows the frequency distribution of the stabilizing element amounts in the powder composition obtained in Example 2. [Figure 4] This graph shows the frequency distribution of stabilizing elements in the calcined body obtained in Example 11. [Figure 5] This graph shows the frequency distribution of stabilizing elements in the calcined material obtained in Comparative Example 9. [Modes for carrying out the invention]

[0014] The powder compositions of this disclosure will be described with reference to examples of embodiments. The definitions of terms used in this embodiment are as follows.

[0015] "Composition" refers to a substance having a certain composition, and examples include one or more selected from the group consisting of powder, granules, molded body, calcined body, and sintered body. "Zirconia composition" refers to a composition consisting essentially of zirconia, and more specifically, a composition using zirconia as a matrix (base material).

[0016] "Powder" refers to a composition that is an aggregate of powder particles (powdered particles) and also possesses fluidity. "Zirconia powder" refers to powder that is essentially made of zirconia, and more specifically, powder that uses zirconia as a matrix (base material). Furthermore, "powder composition" refers to a composition composed of powders with different characteristics, and in particular, a composition containing powders with different compositions.

[0017] "Granular powder" refers to a composition that is an aggregate of powder particles and is fluid, and in particular, a composition in which the powder particles are slowly aggregated. "Zirconia granular powder" refers to granular powder that is essentially made of zirconia, and more specifically, granular powder that has zirconia as its matrix (base material).

[0018] A "molded body" is a composition having a certain shape, composed of powder particles aggregated by physical force, and in particular, a composition that has not undergone heat treatment after the shape has been imparted (e.g., after molding). A "zirconia molded body" is a molded body that is essentially made of zirconia, and more specifically, a molded body that uses zirconia as a matrix (base material). Furthermore, molded bodies are used interchangeably with "compacted bodies".

[0019] A "calcined body" is a composition having a certain shape and composed of fused particles, which has been heat-treated at a temperature below the sintering temperature. A "zirconia calcined body" is a calcined body that is essentially made of zirconia, and more specifically, a calcined body that uses zirconia as a matrix (base material).

[0020] A "sintered body" is a composition having a certain shape composed of crystalline particles, and is a composition that has been heat-treated at a temperature above the sintering temperature. A "zirconia sintered body" is a sintered body that is essentially made of zirconia, and more specifically, a sintered body that uses zirconia as a matrix (base material).

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

[0022] The content of stabilizing elements in a composition (e.g., powder composition, calcined body, sintered body) (mol%; hereinafter also referred to as "stabilizing element amount") is the molar ratio of the stabilizing elements in oxide form to the total amount of zirconium in ZrO2 form and the stabilizing elements in oxide form in the composition. For example, if only yttrium is included as a stabilizing element, the stabilizing element amount (yttrium amount) is the molar ratio of yttria (Y2O3) to the total amount of zirconium in ZrO2 form and yttrium in oxide form (i.e., yttria: Y2O3) in the composition.

[0023] "Change in thermal shrinkage rate per unit temperature (hereinafter also referred to as "rate of change in thermal shrinkage rate" or "ΔV")" is a physical property inherent to the composition and is the change in the thermal shrinkage rate of the composition per unit temperature at a specific temperature. In this embodiment, the rate of change in thermal shrinkage rate can be determined from the following formula.

[0024] ΔV = ΔL / ΔT = {|L(T2)-L(T1)|} / (T2-T1) In the above equation, ΔV is the rate of change in thermal contraction [%℃]. -1 ΔT is the difference in temperature between T1 and T2 [°C], where T2-T1=3±0.5 [°C]. ΔL is the difference in thermal shrinkage rate at temperature T1 (L(T1)) and at temperature T2 (L(T2)) [%].

[0025] Furthermore, the thermal shrinkage rate L(T)[%] at temperature T can be determined using equation (1) by using the measurement results of the amount of thermal shrinkage (l-l0) during the heating process.

[0026] [Number]

[0027] In Equation (1), L(T) is the thermal shrinkage rate [%] at temperature T, l is the length [mm] of the molded body at temperature T, l0 is the length [mm] of the molded body before heat treatment, T is the measurement temperature [°C], T0 is the temperature [°C] at the start of measurement, and β is a coefficient (11.1×10 -6 °C -1 ).

[0028] The thermal shrinkage amount is obtained by measuring the thermal shrinkage amount using a general thermal dilatometer (for example, TD5000SE, manufactured by NETZSCH). The following conditions are listed as the conditions for measuring the thermal shrinkage amount.

[0029] Atmosphere: Under air circulation (100 mL / min) Temperature rising rate: 20 °C / min Maximum reachable temperature: 1600 °C Measurement sample: Molded body Diameter 6 mm Length 15 ± 2 mm Shape: Cylindrical Standard sample: Alumina Diameter 6 mm Length: (Length of the measurement sample) - (1.5 ± 0.5) mm Shape: Cylindrical

[0030] The molded body to be used as the measurement sample may be a molded body obtained by filling a powder sample into a mold, uniaxially molding it at a pressure of 19.6 MPa, and then subjecting it to CIP treatment at a pressure of 196 MPa, or a calcined body obtained by calcining this. Also, when the molded body contains a molding aid, prior to measurement, the measurement sample (molded body) may be heat-treated in an air atmosphere at 700 °C for 1 hour.

[0031] To measure the amount of thermal shrinkage, the sample should be heated while a load of 0.01 kg-force is applied to its length. After heating begins, measure the temperature T and the length (l) of the sample at each temperature every 3 seconds, and calculate L(T) from equation (1) above. ΔL is derived from L(T) at two temperatures T1 and T2 that satisfy the relationship ΔT = 3 ± 0.5°C.

[0032] For measuring thermal shrinkage, alumina is used as the standard sample. The thermal expansion of the standard sample can be corrected using general thermal analysis software (for example, analysis software for TD5000SE Ver. 5.0.2, manufactured by NETZSCH).

[0033] The "BET specific surface area" should be measured using the BET multi-point method (5 points) with nitrogen as the adsorbent gas, in accordance with JIS R 1626. The following conditions are examples of specific measurement conditions for the BET specific surface area.

[0034] Adsorption medium: N2 Adsorption temperature: -196℃ Pretreatment conditions: Degassing treatment at 250°C for at least 1 hour in an air atmosphere.

[0035] The BET specific surface area can be measured using a common instrument (e.g., TriStar II 320, manufactured by Shimadzu Corporation).

[0036] "Tetragonal and cubic crystallinity (hereinafter also referred to as "T+C phase ratio")" refers to the total proportion of tetragonal and cubic crystals in the crystalline phase, and is a value obtained from the powder X-ray diffraction (hereinafter also referred to as "XRD") pattern of the composition using formula (2).

[0037] f T+C =[I t (111)+I c (111)] / [I m (111)+I m (11-1)+I t (111)+I c (111)] (2) In equation (2), f T+C tetragonal and cubic properties, It (111) is the area intensity of the tetragonal (111) plane, I c (111) is the area intensity of the cubic (111) plane, I m (111) is the area intensity of the monoclinic (111) plane, I m (11-1) represents the area intensity of the monoclinic (11-1) plane.

[0038] The area intensity of each crystal plane can be determined by profile fitting the XRD pattern after smoothing and background removal using a segmented pseudo-Voigt function. XRD pattern analysis, including smoothing, background removal, and area intensity calculation, can be performed using the analysis program included with the X-ray diffractometer (for example, the integrated powder X-ray analysis software PDXL Ver.2.2, manufactured by RIGAKU).

[0039] In this embodiment, the XRD pattern is preferably obtained by XRD measurement under the following conditions. Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ = 26° ~ 33° 2θ = 72°~76° Acceleration voltage / current: 40mA / 40kV Divergence vertical limiting slit: 10mm Divergence / Induction Slit: 1° Light-receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185mm

[0040] XRD measurements can be performed using a general-purpose X-ray diffractometer (e.g., Ultima IV, manufactured by RIGAKU). If the composition is a calcined body, the surface should be polished with #400 grit sandpaper conforming to JIS R 6001-2, and then lapped with a 3 μm diamond abrasive before performing the XRD measurement. If the composition is a sintered body, the surface should be polished to a surface roughness of Ra ≤ 0.02 μm, and then the XRD measurement should be performed on that surface.

[0041] In the XRD measurement described above, the XRD peaks corresponding to each crystal plane of zirconia measured are those with peak tops at the following 2θ. XRD peak corresponding to the monoclinic (111) plane: 2θ = 31 ± 0.5° XRD peak corresponding to the monoclinic (11-1) plane: 2θ = 28 ± 0.5° XRD peak corresponding to the tetragonal (111) plane: 2θ = 30 ± 0.5° XRD peak corresponding to the cubic (111) plane: 2θ = 30 ± 0.5°

[0042] The XRD peaks corresponding to the tetragonal (111) plane and the XRD peaks corresponding to the cubic (111) plane are measured as a single overlapping peak. Therefore, I in the above equation t (111)+I c (111) can be obtained from the area intensity of a single XRD peak with its peak top at 2θ = 30 ± 0.5°.

[0043] The "tetragonal prime phase ratio (hereinafter also referred to as "T' phase ratio")" is the proportion of tetragonal prime phase in the crystalline phase, and the "cubic phase ratio (hereinafter also referred to as "C phase ratio")" is the proportion of cubic phase in the crystalline phase. These values ​​are obtained from the XRD pattern on the surface of the sintered body using equations (3) and (4).

[0044] f T’ =[I t’ (004)+I t’ (400)] / [It (004)+I t (400)+I t’ (004)+I t’ (400)+I c (400)] (3) f c =[I c (400)] / [I t (004)+I t (400)+I t’ (004)+I t’ (400)+I c (400)] (4) In equations (3) and (4), f T’ The T' phase ratio is f C C is the phase ratio, I t’ (004) is the area intensity of the tetragonal prime (004) plane, I t’ (400) is the area intensity of the tetragonal prime (400) plane, I t (004) is the area intensity of the tetragonal (004) plane, I t (400) represents the area intensity of the tetragonal (400) plane, and I c (400) represents the area intensity of the cubic (400) plane.

[0045] The XRD pattern and the area intensity of each crystal plane can be determined using the same method as described in equation (2).

[0046] In the XRD measurements described above, the XRD peaks corresponding to each crystal plane measured are those with peak tops at the following 2θ. XRD peak corresponding to the tetragonal (004) plane: 2θ = 72.9 ± 0.1° XRD peak corresponding to the tetragonal prime (004) plane: 2θ = 73.3 ± 0.1° XRD peak corresponding to the tetragonal prime (400) plane: 2θ = 73.9 ± 0.1° XRD peak corresponding to the tetragonal (400) plane: 2θ = 74.3 ± 0.1° XRD peak corresponding to the cubic (400) plane: 2θ = 73.7 ± 0.05°

[0047] The "average particle size" is the D50 in the volume particle size distribution of a powder or powder composition measured by the wet method, and can be measured using a general instrument (e.g., MT3300EXII, manufactured by Microtrac-Bell). As the sample to be measured, a slurry can be used, which is made by dispersing powder that has had slow aggregation removed by a dispersion treatment such as sonication in pure water. When measuring the volume particle size distribution by the wet method, it is preferable to measure the slurry at a pH of 3.0 to 6.0.

[0048] "Average granule size" is the D50 in the volume particle size distribution of granular powder measured by the dry method, and can be measured using a common instrument (e.g., MT3100II, Microtrac-Bell). The sample to be measured should be the granular powder in a slowly aggregated state, without any dispersion treatment such as sonication.

[0049] The "average grain size" is the average diameter based on the number of crystal grains constituting the sintered body. It is obtained by analyzing an SEM (Scanning Electron Microscope) image obtained by observing a region from the surface of the sintered body up to 1% of the surface in the thickness direction of the sintered body using a scanning electron microscope (hereinafter also referred to as "SEM"). In other words, a cross-section of the sintered body is used as the observation sample, and an SEM image is obtained by observing any region from the surface of the sintered body up to 1% of the surface in the thickness direction of the sintered body using an SEM.

[0050] SEM observation can be performed using a general scanning electron microscope (e.g., JSM-IT500LA, manufactured by JEOL Ltd.). The SEM observation should be performed by setting the observation magnification appropriately so that the number of crystal grains to be image-analyzed (crystal grains observed without interruption of grain boundaries in the SEM observation image (described later)) is 450 ± 50. In order to suppress the variation in observed crystal grains due to differences in the SEM observation area, it is preferable to obtain SEM observation images such that the total number of crystal grains observed by 2 or more, preferably 3 to 5 or less, SEM observation images equals the number of crystal grains mentioned above. The following conditions can be exemplified as conditions for SEM observation. Acceleration voltage: 15kV Observation magnification: 5000x to 10000x

[0051] Prior to measurement, the sample should be mirror-polished so that the cross-section of the sintered body has a surface roughness of Ra ≤ 0.02 μm, and then thermally etched at a temperature 100°C lower than the sintering temperature for 30 minutes.

[0052] Image analysis of SEM observations can be performed using image analysis software (for example, Mac-View Ver. 5, manufactured by MOUNTECH). Specifically, crystal grains in which grain boundaries are observed without interruption in the SEM observation are extracted, and the area [μm²] of each extracted crystal grain is calculated. 2 The area is calculated. From the calculated area, the diameter [μm] of a circle with an equal area is converted, and the resulting diameter (Heywood diameter; hereinafter also called "equivalent circle diameter") can be considered as the grain size of the crystal grains. The average value of the equivalent circle diameters of the extracted crystal grains can be used as the average grain size of the sintered body.

[0053] "Molded body density" is the measured density of the molded body [g / cm³]. 3 ] and the volume of the molded body [cm³] can be determined from the dimensions by measuring the volume with calipers. 3 This is the mass [g] of the molded body obtained by mass measurement using a balance, relative to [ ].

[0054] "Incinerated material density" is the measured density of the incinerated material [g / cm³] 3 The volume of the calcined body [cm³] can be determined from the dimensions by measuring the volume with calipers. 3 This is the mass [g] of the calcined body obtained by mass measurement using a balance, relative to [ ].

[0055] Vickers hardness is a value measured using a standard Vickers tester (e.g., Q30A, Qness) equipped with a diamond square pyramidal indenter. The measurement is performed by statically pressing the indenter into the surface of the sample and measuring the diagonal length of the indentation formed on the sample surface. The Vickers hardness can then be calculated using equation (5) with the obtained diagonal length.

[0056] Hv=F / {d 2 / 2sin(α / 2)} (5)

[0057] In equation (5), Hv is the Vickers hardness (HV), F is the measured load (1 kgf), d is the diagonal length of the indentation (mm), and α is the angle of the indenter (136°).

[0058] The following conditions can be used to measure Vickers hardness: Measurement sample: Disc-shaped object with a thickness of 3.0 ± 0.5 mm Measured load: 1 kgf

[0059] Prior to measurement, the sample should be pre-treated by polishing the measurement surface with #800 grit waterproof abrasive paper to remove any irregularities exceeding 0.1 mm.

[0060] "Light transmittance" is the total light transmittance measured in accordance with JIS K 7361-1 for a sample with a thickness of 1 mm. Light transmittance can be measured using a disc-shaped sintered body with a thickness of 1 mm and a surface roughness Ra ≤ 0.02 μm on both sides as the sample, and a haze meter equipped with a D65 light source (for example, haze meter NDH4000, manufactured by Nippon Denshoku Co., Ltd.) as the measuring device.

[0061] "Biaxial bending strength" is a value determined by a two-point bending test in accordance with JIS T 6526. To measure biaxial bending strength, a disc-shaped sintered body with a diameter of 14.5 mm ± 0.5 mm and a thickness of 1.25 mm ± 0.05 mm is used as the measurement sample, and the average value of 10 measurements with a support circle radius of 6 mm and an indenter radius of 0.7 mm is taken as the biaxial bending strength of the sintered body.

[0062] The "Weibull coefficient" is a value calculated according to the method conforming to JIS R 1625. Specifically, a disc-shaped sintered body with a diameter of 14.5 mm ± 0.5 mm and a thickness of 1.25 mm ± 0.05 mm is used as the measurement sample, and the biaxial bending strength is measured 15 times with a support circle radius of 6 mm and an indenter radius of 0.7 mm. After that, the obtained measured strengths are ranked in ascending order. The nth lowest measured strength σ i σ n This is how it works, for example, the first lowest measured intensity σ i σ1 is the second lowest measurement intensity σi σ² is the 15th lowest measured intensity σ i is σ 15 This is how you should do it. Next, using the data ranked in ascending order, ln(1 / ln(1-F i )) on the vertical axis, ln(σ i The regression line can be found by plotting the values ​​on the x-axis, and the slope of this regression line can be taken as the Weibull coefficient. Here, i is the rank when ranked in ascending order, σ i The measured intensity and F i F is the cumulative destroyed probability. i The value can be calculated using the following formula. In the formula below, N is the number of samples to be measured.

[0063] {F i =(i-0.3) / (N+0.4)}

[0064] "Atmospheric pressure sintering" is a method of sintering by heating the material to be sintered (such as a molded body or calcined body) without applying any external force during the sintering process. "Sintering temperature" is the highest temperature reached during sintering, and "sintering time" is the time during which this sintering temperature is maintained.

[0065] The powder composition of this embodiment contains two or more stabilized zirconias with different stabilizing element content, the stabilizing element content in the powder composition is greater than 4.0 mol% and less than or equal to 5.8 mol%, and the rate of change of thermal shrinkage per unit temperature at 1300°C is 0.07%°C. ―1 The powder composition is characterized by the following, and furthermore, the content of each of the two or more stabilized zirconias is 8.0 mol% or less. The powder composition may be a powder composition of stabilized zirconia. The total ratio of the two or more stabilized zirconias in the powder composition may be 90% by mass or more, 95% by mass or more, or 98% by mass or more, from the viewpoint of sufficiently increasing the light transmittance of the sintered body, or it may be 100% by mass or less or less than 100% by mass.

[0066] The powder composition of this embodiment includes a first stabilized zirconia and a second stabilized zirconia, each containing 8.0 mol% or less of stabilizing elements. The first stabilized zirconia and the second stabilized zirconia have different stabilizing element content. For example, the stabilizing element content of the first stabilized zirconia and the second stabilized zirconia may each be 8.0 mol% or less. The total stabilizing element content of the first stabilized zirconia and the second stabilized zirconia may be greater than 4.0 mol% and less than or equal to 5.8 mol%. The rate of change in thermal shrinkage per unit temperature of the powder composition at 1300°C is 0.02%°C. ―1 That's all.

[0067] The powder composition of this embodiment contains two or more stabilized zirconias with different amounts of stabilizing elements (hereinafter, the amount of stabilizing elements is also referred to as "amount of stabilizing elements," and if the stabilizing element is yttrium, etc., it is also referred to as "amount of yttrium," etc.). This results in a powder composition in which particles (powder particles) with different surface activities coexist. A powder composition that does not contain stabilized zirconia with different amounts of stabilizing elements is hypothetically ΔV 1300 Even if the conditions described below are met, short-time sintering cannot yield a sintered body with the translucency suitable for anterior dentures.

[0068] The powder composition of this embodiment contains two or more stabilized zirconias with different amounts of stabilizing elements, which can be confirmed by STEM-EDS of the powder composition.

[0069] When powder compositions without stabilized zirconia, with varying amounts of stabilizing elements, are measured by STEM-EDS, the distribution range of stabilizing element amounts in the powder particles is less than ±1.0 mol% (i.e., the difference between the maximum and minimum values ​​of stabilizing element amounts in the powder particles is less than 2.0 mol%). In this case, the distribution shape of the stabilizing element amounts may be monodisperse. In contrast, the powder composition of this embodiment has a distribution range of ±1.0 mol% or more (i.e., the difference between the maximum and minimum values ​​of stabilizing element amounts in the powder particles is 2.0 mol% or more), and the distribution shape of the stabilizing element amounts is multimodal (e.g., bimodal). It is preferable that the powder composition of this embodiment has a distribution range of ±1.0 mol% or more of stabilizing element amounts in the powder particles, and that the distribution shape of the stabilizing element amounts is multimodal. It is also preferable that the distribution shape of the stabilizing element distribution of the powder composition of this embodiment is bimodal.

[0070] STEM-EDS measurements can be obtained from the TEM observation map and STEM-EDS elemental map of the powder composition. Specifically, zirconia powder particles that are observed without overlapping in the TEM observation map are selected. The number of selected powder particles should be 20±10, and multiple TEM observation maps (e.g., 3±2 maps) may be used. For the selected powder particles, the EDS spectra of each measurement point in the STEM-EDS elemental map are integrated to obtain the EDS spectrum of the powder particles.

[0071] Next, using the relative sensitivity coefficient, the molar ratio of the stabilizing element to the total of zirconium and the stabilizing element is calculated from the peak intensities of zirconium and the stabilizing element in the obtained EDS spectrum. Since the relative sensitivity coefficient is a value specific to the STEM-EDS instrument, the value used in the STEM-EDS instrument used for the measurement should be used. This value can also be confirmed in the instrument's manual, etc. By converting the obtained molar ratios of zirconium and the stabilizing element to oxide equivalents, the amount of the stabilizing element can be determined. The amount of the stabilizing element is the molar ratio (mol%) of the stabilizing element, converted to oxide equivalents, to the total of zirconium and the stabilizing element, converted to oxide equivalents.

[0072] For example, if the stabilizing element is yttrium, the peak intensities of zirconium (Zr) and yttrium (Y) in the powder particles are determined, and the ratio of the yttrium peak intensity to the zirconium peak intensity is calculated. The obtained ratio of the yttrium peak intensity to the zirconium peak intensity is corrected using a relative sensitivity coefficient to determine the molar ratio of yttrium to zirconium. Using the obtained molar ratio, zirconium and yttrium are converted to oxide values. In this way, the amount of yttrium in the powder particles, that is, the molar ratio [mol%] of yttrium converted to Y2O3 relative to the sum of zirconium converted to ZrO2 and yttrium converted to Y2O3 in the powder particles, can be determined. The amount of stabilizing elements in a sufficient number of zirconia powder particles (e.g., 20 ± 10 particles) can be determined, and the difference between the maximum and minimum values ​​can be used as the distribution width of the amount of stabilizing elements in the powder composition. Furthermore, the distribution shape of the stabilizing element amount can be confirmed by plotting the relationship between the amount of stabilizing element in the powder particles and the frequency of the powder particles containing that stabilizing element amount, using a graph or histogram, etc.

[0073] In this embodiment, STEM-EDS measurements can be performed using a general-purpose transmission electron microscope (e.g., TEM: JEM-2100F, manufactured by JEOL Ltd.) and an energy-dispersive X-ray spectrometer (e.g., JED-2300T, manufactured by JEOL Ltd.). The following conditions can be used for TEM observation.

[0074] Acceleration voltage: 200kV Observation magnification: 50,000x to 5,000,000x

[0075] As a pretreatment, the powder composition is crushed in a mortar, and then the powder, from which slow aggregation has been removed by a dispersion treatment such as ultrasonic treatment, is dispersed in acetone to form a slurry, and this slurry is dried on a collodion membrane.

[0076] Figures 1 and 2 are examples of TEM observation diagrams used for STEM-EDS measurements. As shown in Figures 1 and 2, the amount of stabilizing elements can be determined by performing measurements in the areas enclosed by the curves of each powder particle that are observed without overlap. The three-digit numbers in Figures 1 and 2 are for numbering purposes. If necessary, multiple TEM observation diagrams can be used to measure the composition of 20 ± 10 powder particles.

[0077] Thus, in this embodiment, the powder composition can be confirmed to contain two or more stabilized zirconia with different amounts of stabilizing elements, based on the difference (distribution range) between the maximum and minimum values ​​of the stabilizing element content of the zirconia powder particles measured by STEM-EDS, which is 2.0 mol% or more (the distribution range of the amount of stabilizing elements is ±1.0 mol% or more from the median). For example, in the STEM-EDS measurement of the powder composition, if the minimum value of the amount of stabilizing elements is 2 mol% and the maximum value is 5 mol%, the amount of stabilizing elements in the first stabilized zirconia will be 2 mol% and the amount of stabilizing elements in the second stabilized zirconia will be 5 mol%, resulting in a difference of 3 mol% in the amount of stabilizing elements. Therefore, it can be confirmed that the powder composition contains two or more stabilized zirconia with different amounts of stabilizing elements.

[0078] In this embodiment, it is preferable that the powder composition uniformly disperses stabilized zirconia with different amounts of stabilizing elements (i.e., the distribution of the first stabilized zirconia and the second stabilized zirconia is uniform). For example, it is preferable that multiple stabilized zirconia particles with different amounts of stabilizing elements are distributed with high uniformity. Whether or not it is uniform can be evaluated by repeating the measurement of the amount of stabilizing elements by STEM-EDS measurement multiple times (e.g., three or more times) using different TEM observation figures, and determining the variability of the difference between the maximum and minimum values ​​of the amount of stabilizing elements obtained in each measurement. That is, if the variability of the difference between the maximum and minimum values ​​of the measured amount of stabilizing elements obtained by STEM-EDS measurement (variability across multiple measurements) is sufficiently small (e.g., less than ±1 mol%, and even less than ±0.8 mol%), it can be considered that it is uniformly distributed.

[0079] The powder composition of this embodiment may be a powder composition containing two or more stabilized zirconias having different content of stabilizing elements, or a powder composition containing two types of stabilized zirconias having different content of stabilizing elements. Alternatively, it may be a powder composition containing powders of two or more stabilized zirconias having different content of stabilizing elements, or a powder composition containing powders of two types of stabilized zirconias having different content of stabilizing elements. Alternatively, it may be a powder composition of stabilized zirconia containing a first stabilized zirconia and a second stabilized zirconia, or a powder composition of zirconia containing powders of a first stabilized zirconia and a second stabilized zirconia. Alternatively, it may be a mixture of powders of two or more stabilized zirconias having different content of stabilizing elements.

[0080] To fine-tune the amount of stabilizing elements in the powder composition, the powder composition of this embodiment may contain three or more, four or more, or six or five or fewer stabilized zirconia particles with different stabilizing element content. When three or more stabilized zirconia particles are included, it is sufficient to include three or more stabilized zirconia particles with different stabilizing element content, and it is preferable that each of the three stabilized zirconia particles has a different stabilizing element content.

[0081] The amount of stabilizing elements in each stabilized zirconia contained in the powder composition of this embodiment is 8.0 mol% or less. For example, if the powder composition contains a first stabilized zirconia and a second stabilized zirconia, the amount of stabilizing elements in each of the first and second stabilized zirconia is 8.0 mol% or less. That is, the powder composition of this embodiment does not contain stabilized zirconia with a stabilizing element content exceeding 8.0 mol% (the stabilizing element content of the first and second stabilized zirconia is 8.0 mol% or less). In order to make the powder composition suitable for short-time sintering, it is preferable that the powder composition of this embodiment does not contain stabilized zirconia with a stabilizing element content exceeding 8.0 mol%, and furthermore, does not contain stabilized zirconia with a stabilizing element content of 8.0 mol% or more, or even furthermore, 7.5 mol% or more. A powder composition containing stabilized zirconia with a stabilizing element content exceeding 8.0 mol% is, for example, ΔV 1300 Even if the conditions described below are met, short-time sintering cannot yield a sintered body with the translucency suitable for anterior dentures.

[0082] The powder composition of this embodiment preferably contains a first stabilized zirconia having a stabilizing element content of 1.0 mol% to 5.0 mol% and a second stabilized zirconia having a stabilizing element content of 3.0 mol% to 8.0 mol%. Furthermore, the first and second stabilized zirconia may each be powders of stabilized zirconia with different stabilizing element content. In this embodiment, the stabilized zirconia with a low stabilizing element content is referred to as the "first stabilized zirconia," and the stabilized zirconia with a high stabilizing element content is referred to as the "second stabilized zirconia." "First" and "second" are terms used to conveniently distinguish between two stabilized zirconias with different stabilizing element content and do not imply any order or sequence.

[0083] The first stabilized zirconia (stabilized zirconia with a low content of stabilizing elements) preferably has a content of stabilizing elements of 1.0 mol% or more, 1.3 mol% or more, 1.5 mol% or more, 1.8 mol% or more, 2.0 mol% or more, or 2.3 mol% or more, and preferably 5.0 mol% or less, 4.5 mol% or less, 4.2 mol% or less, 4.0 mol% or 3.5 mol% or less.

[0084] The second stabilized zirconia (stabilized zirconia with a high content of stabilizing elements) preferably has a stabilizing element content of 3.0 mol% or more, 3.5 mol% or more, 4.0 mol%, 4.5 mol% or more, or 5.0 mol% or more, and preferably 8.0 mol% or less, 7.5 mol% or less, 7.0 mol% or less, 6.8 mol%, 6.5 mol% or less, or 6.3 mol% or less. By including a first stabilized zirconia with a small ΔV in the first half of sintering and a second stabilized zirconia with a large ΔV in the first half of sintering, the powder composition has a ΔV that exhibits a synergistic effect of the first stabilized zirconia and the second stabilized zirconia. As a result, despite the high amount of stabilizing elements in the powder composition, the ΔV of the powder composition in the first half of sintering is easily suppressed.

[0085] By reducing the content of stabilizing elements in the first stabilized zirconia, or by increasing the content of the first stabilized zirconia in the powder composition, it becomes easier to suppress ΔV in the first half of the sintering of the powder composition.

[0086] In order to allow particles (powder particles) with different surface activities to coexist, the first stabilized zirconia and the second stabilized zirconia only need to have different amounts of stabilizing elements.

[0087] The difference in the amount of stabilizing elements between the first stabilized zirconia and the second stabilized zirconia (hereinafter also referred to as the "stabilizing element difference") is preferably 1.5 mol% or more, 2.0 mol% or more, 2.5 mol% or more, or 3.0 mol% or more, and preferably 5.0 mol% or less, 4.5 mol% or less, 4.0 mol% or less, or 3.5 mol% or less.

[0088] The ratio of the first stabilized zirconia to the second stabilized zirconia contained in the powder composition of this embodiment is arbitrary as long as the above configuration is satisfied, and examples of the ratio of first stabilized zirconia to second stabilized zirconia include 1 mass%:99 mass% to 99 mass%:1 mass%, 20 mass%:80 mass% to 80 mass%:20 mass%, or 35 mass%:65 mass% to 65 mass%:35 mass%, or 45 mass%:55 mass% to 55 mass%:45 mass%.

[0089] The first stabilized zirconia and the second stabilized zirconia may each be in the form of powder particles. That is, the powder composition may contain the first stabilized zirconia particles and the second stabilized zirconia particles. The powder composition may also contain three or more types of stabilized zirconia (stabilized zirconia particles).

[0090] To facilitate densification during short-time sintering, it is preferable that the BET specific surface area of ​​the first stabilized zirconia is greater than or equal to the BET specific surface area of ​​the second stabilized zirconia, and that the BET specific surface area of ​​the first stabilized zirconia is 0 m² less than the BET specific surface area of ​​the second stabilized zirconia. 2 / g or more, and even 1.5m 2 / g or more, and even 2.0m 2 It is preferable that the BET specific surface area is greater than or equal to / g. There is no need to make the difference in BET specific surface area unnecessarily large; for example, the difference between the BET specific surface area of ​​the first stabilized zirconia and the BET specific surface area of ​​the second stabilized zirconia should be 8.0m². 2 / g or less, 6.0m 2 / g or less or 3.5m 2 For example, it can be said that it is less than or equal to / g.

[0091] Furthermore, the BET specific surface area of ​​the first stabilized zirconia was 8 m². 2 / g or more, 10m 2 / g or more, 12m 2 / g or more, 14m 2 It is 16m or more, and also 16m 2 / g or less or 15m 2 For example, it can be said that it is less than or equal to / g.

[0092] The amount of stabilizing elements in the powder composition of this embodiment (i.e., the content of stabilizing elements in the powder composition) is greater than 4.0 mol% and less than or equal to 5.8 mol%. If the amount of stabilizing elements is 4.0 mol% or less, a sintered body that satisfies the translucency required for anterior dentures cannot be obtained by short-time sintering. On the other hand, if the content of stabilizing elements exceeds 5.8 mol%, it becomes difficult to stably manufacture a sintered body that satisfies the translucency required for anterior dentures by short-time sintering. The amount of stabilizing elements in the powder composition of this embodiment is preferably greater than 4.0 mol%, 4.2 mol% or more, 4.4 mol% or more, 4.5 mol% or more, 4.7 mol% or more, 4.8 mol% or more, or 5.0 mol% or more, and also preferably 5.8 mol% or less, 5.7 mol% or less, or 5.5 mol% or less. In this embodiment, the amount of stabilizing elements in the powder composition can be determined by ICP analysis.

[0093] The powder composition of this embodiment preferably does not contain undissolved stabilizing elements. "Not containing undissolved stabilizing elements" means that in the above-described XRD measurement and XRD pattern analysis, no XRD peaks originating from compounds of stabilizing elements (for example, oxides of stabilizing elements such as yttria (Y2O3)) are detected. It is permissible for the powder composition of this embodiment to contain undissolved stabilizing elements to an extent that does not impair the effect of the powder composition of this embodiment.

[0094] The stabilizing element is preferably one or more selected from the group consisting of yttrium (Y), calcium (Ca), and magnesium (Mg). Yttrium, calcium, and magnesium function as stabilizing elements without coloring the zirconia. The stabilizing element may include yttrium, or even consist solely of yttrium.

[0095] The preferred yttrium content of the powder composition of this embodiment is greater than 4.0 mol%, 4.2 mol% or more, 4.4 mol% or more, 4.5 mol% or more, 4.7 mol% or more, 4.8 mol% or more, or 5.0 mol% or more, and also less than or equal to 5.8 mol%, 5.7 mol% or less, or 5.5 mol% or less.

[0096] To fine-tune ΔV, the powder composition of this embodiment may contain one or more elements selected from the group consisting of aluminum, germanium, silicon, and lanthanum as additive elements, or it may contain one or more elements selected from the group consisting of aluminum and germanium, or it may contain aluminum. When additive elements are included, the powder composition of this embodiment may be considered as a powder composition having a zirconia matrix that contains additive elements and also contains stabilizing elements. The additive elements may be included in the powder composition as oxides. Note that the powder composition of this embodiment does not have to contain additive elements (i.e., the content of additive elements may be below the detection limit of compositional analysis).

[0097] The oxide content of the additive elements (hereinafter also referred to as "amount of additive elements," and in cases where the additive element is aluminum, etc., the amount of additive elements is also referred to as "aluminum amount," etc.) is 0% by mass or more, greater than 0% by mass, or 0.001% by mass or more, and examples include being less than 0.2% by mass, 0.1% by mass or less, less than 0.05% by mass, 0.03% by mass or less, 0.01% by mass or less, or 0.005% by mass or less.

[0098] For example, in a composition containing yttrium as a stabilizing element, aluminum as an additive element, and zirconia as the matrix, the amount of stabilizing element (amount of yttrium) is the molar ratio [mol%] of yttrium converted to Y2O3 to the total amount of zirconium converted to ZrO2 and yttrium converted to Y2O3, and can be calculated from {Y2O3 [mol] / (ZrO2 + Y2O3) [mol]} × 100. Furthermore, the amount of additive element (amount of aluminum) in the same composition is the mass ratio [mass%] of aluminum converted to Al2O3 to the total amount of zirconium converted to ZrO2, yttrium converted to Y2O3, and aluminum converted to Al2O3, and can be calculated using the following formula. {Al2O3[g] / (ZrO2+Y2O3+Al2O3)[g]}×100

[0099] The powder composition of this embodiment may contain elements that have the function of coloring zirconia (hereinafter also referred to as "coloring elements"), as long as their effect is not impaired. The coloring elements may be elements that have the function of suppressing the phase transformation of zirconia, or they may be elements that do not have the function of suppressing the phase transformation of zirconia. Specific coloring elements include at least one of transition metal elements and lanthanide rare earth elements, further including at least one of transition metal elements other than zirconium and hafnium, and at least one of lanthanide rare earth elements other than lanthanum. Preferably, one or more selected from the group consisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), titanium (Ti), vanadium (V), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolium (Gd), terbium (Tb), erbium (Er), and ytterbium (Yb), further including one or more selected from the group consisting of iron, cobalt, manganese, titanium, praseodymium, neodymium, terbium, and erbium, and further including one or more selected from the group consisting of iron, cobalt, titanium, terbium, and erbium.

[0100] The powder composition of this embodiment may contain unavoidable impurities such as hafnia (HfO2). The hafnia content as an unavoidable impurity varies greatly depending on the raw ore and manufacturing method, but for example, it can be exemplified as 2.0% by mass or less. In this embodiment, when calculating composition-related values ​​such as content and density, calculations can be performed by considering hafnia as zirconia (ZrO2).

[0101] The rate of change in thermal shrinkage rate per unit temperature at 1300°C for the powder composition of this embodiment (hereinafter referred to as "ΔV") 1300 It is also called ". ) is 0.07%℃ -1 The following is true: 0.07%℃ -1 Less than 0.065%℃ -1 Below or at 0.06%℃ -1 The following is preferable: In addition to the above configuration, such ΔV 1300By satisfying this, even when the powder composition of the present embodiment is sintered in a short time, a sintered body having translucency suitable for a front tooth denture can be obtained. Note that 1300°C is the temperature range in which the thermal shrinkage of zirconia progresses. Therefore, ΔV 1300 is more than 0%°C -1 and, furthermore, is 0.02%°C -1 or more, 0.04%°C -1 or more, or 0.05%°C -1 or more.

[0102] The rate of change of the thermal shrinkage rate per unit temperature at 1500°C of the powder composition of the present embodiment (hereinafter, also referred to as "ΔV 1500 ") is preferably 0.02%°C -1 or more, or 0.03%°C -1 or more. Thereby, densification in short-time sintering is more likely to be promoted. ΔV 1500 is 0.05%°C -1 or less, or 0.04%°C -1 or less. ΔV 1500 is 0.05%°C -1 or less, so that a sintered body having high translucency can be stably obtained easily when the powder composition is subjected to short-time sintering.

[0103] In order to have suitable sinterability by short-time sintering and reduce it, ΔV 1300 and ΔV 1500 are preferably different, that is, the rate of change of the thermal shrinkage rate is not constant. Furthermore, ΔV 1300 is larger than ΔV 1500 (satisfying the relationship of ΔV 1300 >ΔV 1500 ) is preferable, and (ΔV 1300 -ΔV 1500 ) is 0.05%°C -1 or less, furthermore 0.045%°C -1 or less, and ΔV 1300 -ΔV 1500 is 0%°C -1 or more, furthermore more than 0%°C -1 , furthermore 0.010%°C -1 or more, furthermore 0.020%°C-1 It is preferable that the above conditions are met.

[0104] ΔV 1300 and ΔV 1500 This is indirectly affected by the composition of the powder composition, etc. For example, a decrease (or increase) in the amount of stabilizing elements and a decrease (or increase) in the amount of added elements will affect ΔV. 1300 There is a tendency for it to become slower (or faster). Also, due to a decrease (or increase) in the BET specific surface area of ​​the first stabilized zirconia or a decrease (or increase) in the amount of stabilizing elements, ΔV 1300 There is a tendency for it to become slower (or faster). Also, due to the decrease (or increase) in the BET specific surface area of ​​the second stabilized zirconia, ΔV 1500 There is a tendency for it to become faster (or slower). By adjusting these, ΔV 1300 and ΔV 1500 You can control it as needed.

[0105] The powder composition of this embodiment has a BET specific surface area of ​​8 m². 2 / g or more 13m 2 It is preferable that the amount of stabilizing elements in the powder composition of this embodiment satisfies this range when the BET specific surface area is less than or equal to ΔV. 1300 This makes it easier to satisfy the condition. The BET specific surface area is 8m 2 / g or more, 9m 2 / g or more, 9.5m 2 / g or more or 10m 2 It is 13m or more / g, and also 13m 2 / g or less, 12m 2 / g or less or 11m 2 It is preferable that the value be less than or equal to / g.

[0106] The T+C phase ratio of the powder composition in this embodiment is preferably 65% ​​or more, 75% or more, 80% or more, or 90% or more. Alternatively, the T+C phase ratio may be 95% or less, or 93% or less.

[0107] The average particle size of the powder composition of this embodiment is 0.35 μm or more, 0.40 μm or more, and more preferably 0.50 μm or less, or 0.45 μm or less.

[0108] To improve flowability, the powder composition of this embodiment may be in granular form. Examples of granular powder particle sizes include 30 μm or more, 40 μm or more, or 50 μm or more, and also 80 μm or less, or 60 μm or less. Furthermore, the bulk density of the granular powder is 1.00 g / cm³. 3 or more, or 1.10 g / cm³ 3 That is all, and also 1.40 g / cm³ 3 The following or 1.30 g / cm³ 3 The following are some examples:

[0109] A method for producing the powder composition of this embodiment will now be described.

[0110] The manufacturing method of the powder composition of this embodiment is arbitrary, as long as it has the characteristics described above. A preferred manufacturing method of the powder composition of this embodiment is a method for producing the powder composition that includes the step of mixing two or more stabilized zirconia powders having different content of stabilizing elements.

[0111] The stabilized zirconia powders subjected to the step of mixing two or more stabilized zirconia powders having different content of stabilizing elements (hereinafter also referred to as the "mixing step") may be, for example, the first stabilized zirconia powder and the second stabilized zirconia powder described above.

[0112] It is preferable that each stabilized zirconia powder has a BET specific surface area similar to that of the powder composition of this embodiment. In addition, it is more preferable that the BET specific surface areas of each stabilized zirconia powder differ from each other. It is even more preferable that the BET specific surface area of ​​the first stabilized zirconia powder is greater than or equal to the BET specific surface area of ​​the second stabilized zirconia powder. Specifically, it is preferable that the BET specific surface area of ​​the first stabilized zirconia powder is greater than, for example, 0 m² than the BET specific surface area of ​​the second stabilized zirconia powder. 2 / g or more, preferably 1.5m 2 / g or more, more preferably 2.0m 2It is greater than / g. Also, the difference between the BET specific surface area of ​​the first stabilized zirconia powder and the BET specific surface area of ​​the second stabilized zirconia powder is 6.0m². 2 / g or less, and 5.0m 2 It may be less than / g.

[0113] If the amount of stabilizing elements in each powder of stabilized zirconia used as a starting material in the method for producing the powder composition is known, the amount of stabilizing elements in each stabilized zirconia contained in the powder composition may be calculated from the amount of stabilizing elements and the mixing ratio of each powder of stabilized zirconia, instead of the STEM-EDS measurement described above.

[0114] The difference between the maximum and minimum values ​​of stabilizing element amounts obtained by STEM-EDS measurement (distribution width, Method I) tends to be larger than the difference in stabilizing element amounts for each powder of stabilized zirconia (Method II). This is because the difference in Method II is determined as the difference in the average values ​​of stabilizing element amounts for each powder, while the difference in Method I is determined as the maximum and minimum values ​​in a mixture of each powder. If at least one of the differences obtained by Method I and Method II is 2.0 mol% or more, it can be determined that the mixture contains two or more types of stabilized zirconia with different amounts of stabilizing elements. At least one of the differences obtained by Method I and Method II may be 2.5 mol% or more, greater than 2.5 mol%, or 3.0 mol% or more. This allows for sufficiently high light transmittance and biaxial bending strength of the resulting sintered body. At least one of the differences obtained by Method I and Method II may be 6.0 mol% or less, 5.0 mol% or less, or 4.0 mol% or less. At least one of the differences obtained by Method I and Method II may be between 2.0 and 6.0 mol%. The upper and / or lower limits of this numerical range can be replaced with the values ​​mentioned above.

[0115] The method for producing the stabilized zirconia powder to be used in the mixing process is arbitrary. For example, such a method includes a powder calcination step in which a composition containing a zirconia sol and a stabilizing element source (hereinafter also referred to as the "sol composition") is heat-treated to obtain calcined powder, and a powder grinding step in which the calcined powder is ground.

[0116] The zirconia sol is a sol in which zirconium dioxide is hydrated and crosslinked, and is preferably a zirconia sol obtained by at least one of hydrothermal synthesis and hydrolysis, and more preferably a zirconia sol obtained by hydrolysis.

[0117] A stabilizing element source (hereinafter also referred to as a "yttrium source" when the stabilizing element is yttrium, etc.) can be any compound containing a stabilizing element, and may be one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, nitrates, and acetates of the stabilizing element, preferably oxides, hydroxides, oxyhydroxides, and chlorides of the stabilizing element, and more preferably at least one of oxides, hydroxides, and chlorides of the stabilizing element. For example, a yttrium source may be one or more selected from the group consisting of yttrium oxide (yttria), yttrium hydroxide, and yttrium chloride, preferably at least one of yttrium oxide and yttrium chloride.

[0118] The amount of stabilizing element source content should be similar to the amount of stabilizing element in the target stabilized zirconia, and an amount equivalent to the amount of stabilizing element mentioned above is an example.

[0119] The sol composition may contain zirconia sol and a stabilizing element source, and an aqueous solution containing zirconia sol and a stabilizing element source is an example.

[0120] In the powder calcination process, the sol composition is heat-treated. This yields calcined powder, which is a precursor to stabilized zirconia powder.

[0121] In the heat treatment of the powder calcination process, the heat treatment conditions should be set appropriately according to the amount of sol composition subjected to the powder calcination process, the BET specific surface area of ​​the target calcined powder, and the characteristics of the calcination furnace used for calcination. For example, the higher (or lower) the heat treatment temperature, the more likely the BET specific surface area is to decrease (or increase). Examples of heat treatment temperatures include 950°C or higher, 1000°C or higher, 1020°C or higher, or 1100°C or higher, and 1250°C or lower, 1200°C or lower, 1180°C or lower, or 1150°C or lower. Examples of holding times at the heat treatment temperature include 1 hour or more and 8 hours or more, and 2 hours or more and 6 hours or less. However, the effect of holding time on the BET specific surface area of ​​the calcined powder is small compared to the heat treatment temperature. The heat treatment can be carried out using a general calcination furnace.

[0122] The atmosphere for the heat treatment is arbitrary and can be one or more selected from the group consisting of an oxidizing atmosphere, a reducing atmosphere, an inert atmosphere, and a vacuum atmosphere. An oxidizing atmosphere is preferred, and an atmospheric atmosphere is more preferred.

[0123] In the powder grinding process, the grinding method is arbitrary as long as it produces a powder with the desired particle size. The grinding method can be at least one of wet grinding or dry grinding, with wet grinding being preferred. Ball mill grinding is an example of a preferred grinding method. Furthermore, the grinding conditions can be appropriately set according to the grinding method and the desired particle size. For example, increasing the grinding time tends to reduce the particle size.

[0124] In the manufacturing method of this embodiment, two or more stabilized zirconia powders with different stabilizing element content are mixed in the mixing step. The mixing method can be any method that ensures uniform mixing of the stabilized zirconia powders, and at least one of dry mixing and wet mixing can be exemplified, with wet mixing being preferable and mixing in an aqueous solvent being more preferable.

[0125] A preferred mixing method is to prepare a slurry containing stabilized zirconia powder, as this allows for uniform mixing of the stabilized zirconia powder.

[0126] Another method involves adding a slurry containing stabilized zirconia powder with a large BET specific surface area to a slurry containing stabilized zirconia powder with a small BET specific surface area, and then mixing the two. This mixing method makes it easier to uniformly mix the slurry containing stabilized zirconia powder, and makes it easier to satisfy the ΔV suitable for short-time sintering.

[0127] Mixing requires a stirring power of 0.005 kW / m 3 Above or above, or 0.01 kW / m 3 Anything above that is acceptable, and even better, 0.1 kW / m 3 Above or above, or 0.3kW / m 3 The above is preferable. Mixing with such required stirring power helps to suppress variations in properties when the powder composition of this embodiment is repeatedly manufactured. As a result, the Weibull coefficient of the sintered body obtained by short-time sintering of the powder composition tends to be higher. The required stirring power does not need to be excessively high, 1.0 kW / m 3 The following or 0.7 kW / m 3 The following can be given as examples.

[0128] The mixing time can be set appropriately depending on the amount of powder used in the mixing process, but examples include 0.5 hours to 12 hours.

[0129] The mixing ratio of the stabilized zirconia powder can be appropriately adjusted depending on the amount of stabilizing elements in the stabilized zirconia and the target powder composition. Examples of ratios such as 1% by mass:99% by mass to 99% by mass:1% by mass, 20% by mass:80% by mass to 80% by mass:20% by mass, or 35% by mass:65% by mass to 65% by mass:35% by mass, or 45% by mass:55% by mass to 55% by mass:45% by mass.

[0130] In order to fine-tune the amount of stabilizing elements in the powder composition, three or more types of stabilized zirconia with different amounts of stabilizing elements, or six or fewer types of stabilized zirconia with five or fewer types, may be mixed during the mixing process.

[0131] In the mixing step, an additional element source may be added. This yields a powder composition containing the added element. The additional element source (hereinafter also referred to as "aluminum source," etc., when the added element is aluminum, etc.) is at least one of the added element and its compounds, preferably at least one of the oxide of the added element and its precursor, and more preferably the oxide of the added element. For example, the aluminum source is at least one of alumina and its precursor, preferably alumina, and more preferably α-alumina.

[0132] The amount of additive element source mixed in should be the same as the amount of additive element in the target powder composition, and an amount equivalent to the amount of additive element mentioned above is an example.

[0133] In the mixing step, a coloring element source may be added. The coloring element source is a compound containing a coloring element, preferably at least one of the oxide of the coloring element and its precursor, more preferably the oxide of the coloring element. The amount of coloring element source added should be such that it results in the desired color tone of the sintered body.

[0134] In the mixing process, in addition to mixing at least one of the additive element source and the coloring element source (hereinafter also referred to as "additive element source, etc."), or instead of mixing the additive element source, etc., stabilized zirconia containing at least one of the additive element and the coloring element may be provided.

[0135] The manufacturing method of this embodiment may include a granulation step after the mixing step in which the powder composition is granulated. The granulation can be carried out by any method that results in a state in which the zirconia powder is slowly aggregated, and granulation methods such as spray granulation can be exemplified.

[0136] In the granulation process, the powder composition of this embodiment may be mixed with a binder and then granulated. Including a binder improves the shape retention of the molded article obtained by molding the granular powder. The binder contained in the granular powder can be a known one used for molding ceramics, and is preferably an organic binder. The organic binder is one or more selected from the group consisting of polyvinyl alcohol, polyvinyl butyrate, wax, and acrylic resin, preferably one or more of polyvinyl alcohol and acrylic resin, and more preferably an acrylic resin. In this embodiment, the acrylic resin is a polymer containing at least one of acrylic acid ester and methacrylic acid ester. Specific examples of acrylic resins include one or more selected from the group consisting of polyacrylic acid, polymethacrylic acid, acrylic acid copolymer and methacrylic acid copolymer, and their derivatives.

[0137] Next, an example of an embodiment of the calcined body of this disclosure will be described.

[0138] The calcined body of this embodiment contains two or more stabilized zirconia materials with different stabilizing element content, the stabilizing element content in the calcined body is greater than 4.0 mol% and less than or equal to 5.8 mol%, and the rate of change of thermal shrinkage per unit temperature at 1300°C is 0.07%°C. ―1 The calcined body is characterized by the following, and furthermore, the content of stabilizing elements in each of the two or more stabilized zirconias is 8.0 mol% or less. The calcined body may be a calcined body of stabilized zirconia. The total ratio of the two or more stabilized zirconias in the calcined body may be 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass or less, from the viewpoint of sufficiently increasing the light transmittance of the sintered body. With the calcined body of this embodiment, a sintered body that satisfies the light transmittance required for anterior dentures can be obtained even with short sintering time.

[0139] The calcined body of this embodiment may contain a first stabilized zirconia and a second stabilized zirconia, each having a stabilizing element content of 8.0 mol% or less. The first stabilized zirconia and the second stabilized zirconia have different stabilizing element content. For example, the stabilizing element content of the first stabilized zirconia and the second stabilized zirconia may each be 8.0 mol% or less. The stabilizing element content in the calcined body may be greater than 4.0 mol% and less than or equal to 5.8 mol%. The rate of change in thermal shrinkage per unit temperature of the calcined body at 1300°C is 0.02%°C. ―1 That's all.

[0140] The calcined body of this embodiment contains two or more stabilized zirconia with different stabilizing element content. The fact that the calcined body of this embodiment contains two or more stabilized zirconia with different stabilizing element content can be measured by STEM-EDS in the same manner as the powder composition of this embodiment, except that the calcined body is dry-ground to obtain a powder with an average particle size of 0.40 μm or more and 0.50 μm or less. A calcined body that has at least one of the following conditions: the distribution width of the stabilizing element amount is ±1.5 mol% or more, and the distribution shape of the stabilizing element amount is multimodal (e.g., bimodal) contains two or more stabilized zirconia with different stabilizing element content. It is preferable that the distribution shape of the stabilizing element amount distribution of the calcined body of this embodiment is bimodal.

[0141] The BET specific surface area of ​​the calcined body in this embodiment is 5 m². 2 / g or more or 6m 2 It is 1 / g or more, and also 8m 2 / g or less or 7m 2 It is preferable that the value be less than or equal to / g.

[0142] The T+C phase ratio of the calcined body in this embodiment is preferably 75% or more, 80% or more, 90% or more, 95% or more, or 98% or more, and preferably 100% or less or 99% or less.

[0143] The calcined density of the calcined material in this embodiment is 2.95 g / cm³. 3or more, or 3.00 g / cm³ 3 The above, and also 3.50 g / cm³ 3 Below, 3.30g / cm 3 The following or 3.15 g / cm³ 3 The following are some examples:

[0144] To reduce the likelihood of defects occurring during shape processing such as CAM machining, the Vickers hardness of the calcined body in this embodiment is set to 35 kgf / mm². 2 40 kgf / mm² or more 2 The above conditions apply, and the load is 100 kgf / mm². 2 Below, 80kgf / mm 2 Below, 70kgf / mm 2 Below, 55kgf / mm 2 Below, 50kgf / mm 2 The following, or 47 kgf / mm² 2 The following is preferable:

[0145] Aside from the fact that the calcined body is composed of fused particles, the characteristics of the calcined body of this embodiment are the same as those of the powder composition of this embodiment.

[0146] Next, the method for manufacturing the calcined body of this embodiment will be described.

[0147] The method for manufacturing the calcined body of this embodiment is arbitrary, but one example is a method for manufacturing the calcined body that includes the step of calcining a molded body containing the powder composition of this embodiment.

[0148] The molded body subjected to the calcination step (hereinafter also referred to as the "calcination step") of a molded body containing the powder composition of this embodiment is preferably a molded body in which the powder composition of this embodiment has been molded.

[0149] The shape of the molded body can be at least one selected from the group consisting of cubic, rectangular, polyhedral, columnar, cylindrical, disc-shaped, and approximately spherical. The molded body can have a shape similar to the intended calcined or sintered body, such as a dental prosthesis, taking into account thermal shrinkage due to sintering.

[0150] The density of the molded body is 2.80 g / cm³. 3 More than 2.95g / cm 3 or more, or 3.00 g / cm³ 3 The above, and also 3.50 g / cm³ 3 Below, 3.40g / cm 3 Below, 3.30g / cm 3 Below, 3.20g / cm 3 The following or 3.15 g / cm³ 3 The following are some examples:

[0151] In this embodiment, the method for manufacturing the molded article is arbitrary, and known ceramic molding methods can be applied. Examples of molding methods include one or more selected from the group consisting of uniaxial pressing, cold isohydrostatic pressing, slip casting, and injection molding. For simplicity, the molding method is preferably at least one other than slip casting, and more preferably at least one of uniaxial pressing and cold isohydrostatic pressing, and more preferably cold isohydrostatic pressing after uniaxial pressing. Examples of uniaxial pressing pressures include 15 MPa to 150 MPa and cold isohydrostatic pressing pressures include 90 MPa to 400 MPa, and the higher the pressure during molding, the higher the density of the molded article tends to be.

[0152] If the molded article contains a binder, a step to remove the binder, a so-called debindering step, may be included prior to calcination. The method of removing the binder is arbitrary, but examples include heat treatment in an air atmosphere at 400°C or higher but less than 900°C.

[0153] Calcination is a heat treatment performed at a temperature that does not lead to sintering of the zirconia. The following conditions are examples of calcination conditions. Calcination atmosphere: Oxidizing atmosphere, preferably air atmosphere Calcination temperature: 950°C or higher or 1000°C or higher, 1150℃ or below, or 1100℃ or below Pre-cooking time: 0.5 hours or more, or 1 hour or more, 5 hours or less or 3 hours or less

[0154] Next, a method for manufacturing a sintered body using at least one of the powder composition and calcined body of this embodiment (hereinafter also referred to as "the powder composition, etc." of this embodiment) will be described.

[0155] The powder composition of this embodiment can be used to produce a calcined body suitable as a precursor for anterior dentures by calcining. The powder composition of this embodiment can be used to produce a sintered body suitable for anterior dentures by sintering. In particular, the powder composition of this embodiment can be used to produce a sintered body that has the same translucency and aesthetic properties as a sintered body obtained by a conventional sintering method (e.g., normal sintering), even when the sintering is performed in a short time.

[0156] The method for manufacturing a sintered body using the powder composition of this embodiment allows for obtaining a sintered body by sintering it using any sintering method. The sintering process can be performed using one or more sintering methods selected from the group of known ceramic sintering methods, such as atmospheric pressure sintering, pressure sintering, and vacuum sintering. Since it is widely applied to the manufacture of dental prosthetic materials, the sintering method is preferably atmospheric pressure sintering, and more preferably atmospheric pressure sintering only, that is, a sintering method that does not use pressure sintering or vacuum sintering. When the sintering method is atmospheric pressure sintering only, a sintered body is obtained from the powder composition of this embodiment as a so-called atmospheric pressure sintered body.

[0157] A particularly preferred sintering method is atmospheric pressure sintering in an atmospheric environment, and the sintering time is 7 hours or less, preferably 5 hours or less, more preferably 3 hours or less, and even more preferably 1 hour or less. Furthermore, it is preferable to perform sintering by raising the temperature to the sintering temperature at different heating rates (for example, sintering by raising the temperature at two different heating rates).

[0158] The following conditions are examples of preferred sintering conditions. Sintering method: atmospheric pressure sintering Sintering atmosphere: Oxidizing atmosphere, preferably air atmosphere Sintering temperature: 1450°C or higher, 1500°C or higher, or 1550°C or higher, and 1650°C or lower, 1620°C or lower, or 1600°C or lower. Sintering time: 3 minutes or more, 5 minutes or more, 7 minutes or more, or 8 minutes or more, 30 minutes or less, 20 minutes or less, or 15 minutes or less Heating rate: (from room temperature to 1050°C) 150°C / min or higher, 200°C / min or higher, or 250°C / min or higher, 350°C / min or less or 300°C / min or less (From 1050℃ to sintering temperature) 30°C / min or higher, 40°C / min or higher, or 50°C / min or higher, Below 150°C / min, below 70°C / min, or below 60°C / min Cooling rate: (from sintering temperature to 900°C) 30°C / min or higher, 40°C / min or higher, or 60°C / min or higher, Below 300°C / min, below 100°C / min, or below 65°C / min

[0159] When sintering a powder composition, the powder composition may be molded into a body by any method prior to sintering. Similarly, when sintering a calcined body, the calcined body may be processed into any shape prior to sintering. The calcined body can be shaped into any shape by processing using CAD / CAM or similar methods, making it easier to obtain a sintered body of any shape.

[0160] Next, as an example of a sintered body obtained by sintering the powder composition of this embodiment, a sintered body obtained by sintering the powder composition of this embodiment in a short time (hereinafter also referred to as "the sintered body of this embodiment") will be described below as an example.

[0161] The sintered body of this embodiment is characterized by containing stabilized zirconia containing stabilizing elements as a matrix, wherein the content of the stabilizing elements is greater than 4.0 mol% and less than or equal to 5.8 mol%, the average crystal grain size is 2.5 μm or less, and the tetragonal prime phase ratio is 70% or more. The above sintered body may also have a content of stabilizing elements greater than 4.0 mol% and less than or equal to 5.8 mol%, a crystal grain size difference of 0.10 μm or less, and a tetragonal prime phase ratio of 70% or more. The sintered body may be a zirconia sintered body (zirconia sintered body) with zirconia as the matrix.

[0162] The stabilizing element is preferably one or more selected from the group consisting of yttrium, calcium, and magnesium, and more preferably yttrium.

[0163] In the sintered body of this embodiment, the stabilizing element is solid-dissolved in zirconia, and more preferably, the sintered body of this embodiment does not contain any undissolved stabilizing element.

[0164] The amount of stabilizing elements in the sintered body or matrix is ​​preferably greater than 4.0 mol% and less than or equal to 5.8 mol%, and more preferably greater than 4.0 mol%, 4.2 mol% or more, 4.4 mol% or more, 4.5 mol% or more, 4.7 mol% or more, 4.8 mol% or more, or 5.0 mol% or more, and also preferably 5.8 mol% or less, 5.7 mol% or less, or 5.5 mol% or less.

[0165] In this embodiment, the amount of stabilizing elements in the sintered body and matrix can be determined by ICP analysis.

[0166] The average grain size of the sintered body in this embodiment is preferably 2.5 μm or less, 2.0 μm or less, 1.8 μm or less, 1.5 μm or less, 1.3 μm or less, or less than 1.3 μm. Alternatively, the average grain size may be 0.7 μm or more, 0.8 μm or more, 1.0 μm or more, or 1.2 μm or more.

[0167] The grain size difference of the sintered body in this embodiment is 0.10 μm or less, preferably less than 0.10 μm, 0.09 μm or less, 0.07 μm or less, 0.05 μm or less, or 0.04 μm or less. Alternatively, the grain size difference may be 0 μm or more, or 0.005 μm or more. Such grain sizes are considered to represent the state of the crystalline particles obtained by sintering the powder composition of this embodiment for a short time.

[0168] "Grain particle size difference" is an indicator that shows the state of the crystalline particles constituting the sintered body. Specifically, it is an indicator that shows the difference between the crystalline particles constituting the surface of the sintered body and the crystalline particles constituting the interior of the sintered body.

[0169] The grain size difference can be determined by image analysis of SEM observation images of the cross-section obtained by cutting the sintered body along its thickness. Specifically, first, with the total thickness of the sintered body set to 100%, SEM observation is performed in an arbitrary region between the surface and 1% (surface portion) in the thickness direction. The resulting SEM observation image is then image-analyzed to determine the average value of the equivalent circle diameter of the crystal grains constituting the surface portion of the sintered body (hereinafter referred to as "surface grain size"). Next, SEM observation is performed in an arbitrary region between 40% and 60% from the surface in the thickness direction of the sintered body. The resulting SEM observation image is then image-analyzed to determine the average value of the equivalent circle diameter of the crystal grains constituting the interior of the sintered body (hereinafter referred to as "interior grain size") in the same manner as the surface grain size. The number of crystal grains measured in the surface portion of the sintered body and the number of crystal grains contained in the interior portion of the sintered body are set to 450 ± 50 each. If necessary, multiple SEM observation images may be used to measure the equivalent circle diameter. The absolute value of the difference between the surface grain size and the interior grain size obtained in this way is the grain size difference.

[0170] Surface grain size and internal grain size can be obtained by analysis using image analysis software (e.g., Mac-View Ver. 5, manufactured by MOUNTECH). The absolute value of the difference between the surface grain size and the internal grain size can be calculated and used as the crystal grain size difference.

[0171] The T' phase ratio of the sintered body in this embodiment is preferably 70% or more, 80% or more, or 90% or more. Furthermore, the T' phase ratio may be 100% or less, or 99% or less.

[0172] The light transmittance of the sintered body of this embodiment is preferably greater than 45%, 46% or more, or 47% or more. Having this light transmittance allows for application to dental prosthetic materials, such as anterior dentures, where particularly high light transmission is required. Examples of light transmittances within the range of stabilizing element content of the sintered body of this embodiment include 52% or less, 51% or less, or 50% or less.

[0173] The carbon phase ratio of the sintered body in this embodiment is preferably less than 30%, 10% or less, 5% or less, 1% or less, or 0.5% or less. The sintered body in this embodiment does not need to contain carbon phase (the carbon phase ratio may be 0%), and the carbon phase ratio of the sintered body in this embodiment should be 0% or more.

[0174] The biaxial bending strength of the sintered body of this embodiment is preferably 650 MPa or higher, 700 MPa or higher, 720 MPa or higher, 740 MPa or higher, 770 MPa or higher, 790 MPa or higher, or 800 MPa or higher. By satisfying such biaxial bending strength, the sintered body of this embodiment can also be applied to dental prostheses of smaller shapes. A higher biaxial bending strength is preferable. When the amount of stabilizing elements of this embodiment is satisfied, the biaxial bending strength can be exemplified as 1000 MPa or less, 900 MPa or less, 850 MPa or less, or 800 MPa or less.

[0175] The Weibull coefficient of the sintered body in this embodiment can be exemplified as 4.0 or higher, 5.0 or higher, or 6.0 or higher. A higher Weibull coefficient is preferable, but when the amount of stabilizing elements in this embodiment is satisfied, the Weibull coefficient can be exemplified as 15.0 or lower, or 12.0 or lower.

[0176] Although some embodiments of the present disclosure have been described above, the present disclosure is not limited to any of the above embodiments. For example, numerical ranges obtained by arbitrarily combining the upper and lower limit values specifically described in the above embodiments are also included in the present disclosure. In addition, those in which the upper limit value and / or the lower limit value are replaced with the values of the examples described below are also included in the present disclosure.

Examples

[0177] Hereinafter, the content of the present disclosure will be described in detail with reference to examples and comparative examples. However, the present disclosure is not limited to the examples.

[0178] (Crystal phase, tetragonal + cubic ratio, tetragonal prime phase ratio, cubic ratio) The crystal phase was identified by XRD measurement under the following conditions using an X-ray diffractometer (device name: Ultima IV, manufactured by Rigaku Corporation). X-ray source: CuKα ray (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ = 26° to 33° 2θ = 72° to 76° Acceleration voltage and current: 40 mA · 40 kV Divergence vertical limit slit: 10 mm Divergence / incidence slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm

[0179] The identification of the crystal phase was performed by using an analysis program attached to the X-ray diffractometer (program name: integrated powder X-ray analysis software PDXL Ver. 2.2, manufactured by Rigaku Corporation) to perform smoothing processing and background removal processing, and then performing profile fitting on the XRD pattern after the processing by a split pseudo-Voigt function.

[0180] The tetragonal + cubic fraction, cubic fraction, and tetragonal prime fraction were determined from the XRD patterns of the surface of the powder composition, calcined body, and sintered body of this embodiment using formulas (2), (4), and (3).

[0181] (composition analysis) The composition of the composition was determined by ICP analysis.

[0182] (Stabilizing element amount: Y2O3 [mol%]) The amount of stabilizing elements (mol% of yttrium in oxide terms) was determined by STEM-EDS measurement of the powder composition or calcined material using the method described above. STEM-EDS measurements were performed using a transmission electron microscope (instrument name: JEM-2100F, manufactured by JEOL Ltd.) and an energy-dispersive X-ray spectrometer (instrument name: JED-2300T, manufactured by JEOL Ltd.) under the following conditions. Multiple STEM observations were used so that the number of powder particles measured was 20 ± 10. Acceleration voltage: 200kV Observation magnification: 400,000x

[0183] As a pretreatment for STEM-EDS measurement, the powder composition was crushed in a mortar. Then, the powder, whose slow agglomeration was undone by sonication, was dispersed in acetone to prepare a slurry. This slurry was dried on a collodion membrane to obtain the sample for measurement. In the case of calcined bodies, the sample for measurement was obtained in the same manner as for the powder composition, except that the calcined bodies were dry-ground in a mortar.

[0184] (BET specific surface area) The BET specific surface area was measured using an automatic specific surface area measuring device (device name: Tristar II 320, manufactured by Shimadzu Corporation) in accordance with JIS R 1626, under the following conditions, using the BET multi-point method (5 points). Adsorption medium: N2 Adsorption temperature: -196℃ Pretreatment conditions: Degassing treatment at 250°C for at least 1 hour in an air atmosphere.

[0185] (Average particle size) The average particle size was measured using a Microtrac particle size distribution analyzer (instrument name: MT3300EXII, manufactured by Microtrac-Bell) by laser diffraction and scattering. The measurement conditions are shown below. Light source: Semiconductor laser (wavelength: 780nm) Voltage: 3mW Sample to be measured: Grinding slurry Refractive index of zirconia: 2.17 Refractive index of solvent (water): 1.333 Calculation mode: HRA

[0186] As a pretreatment, the sample powder was suspended in distilled water to form a slurry, which was then dispersed for 3 minutes using an ultrasonic homogenizer (device name: US-150T, manufactured by Nippon Seiki Seisakusho).

[0187] (Rate of change in thermal shrinkage coefficient: ΔV) ΔV(ΔV) of the powder composition and calcined body 1300 and ΔV 1500 The thermal expansion coefficient () was determined using a thermal expander (device name: TD5000SE, manufactured by NETZSCH) and alumina as a standard sample, according to the method described above. Thermal analysis software (software name: TD5000SE analysis software Ver. 5.0.2, manufactured by NETZSCH) was used to correct for the thermal expansion of the standard sample.

[0188] The ΔV of the powder composition and the calcined body were measured using the following procedure. For the ΔV of the powder composition, the powder composition was filled into a mold, uniaxially molded at a pressure of 19.6 MPa, and then subjected to CIP treatment at a pressure of 196 MPa to obtain a cylindrical molded body A with a diameter of 6 mm and a length of 15 ± 2 mm. Molded body A was treated in an air atmosphere at 700°C for 1 hour and used as the measurement sample for measuring the ΔV of the powder composition. For the ΔV of the calcined body, molded body A was calcined at 1000°C for 1 hour and used as the measurement sample for measuring the ΔV of the calcined body. The measurement conditions are shown below. Atmosphere: Under atmospheric flow (100 mL / min) Heating rate: 20℃ / min Maximum temperature reached: 1600℃

[0189] T0 was set at 30°C, and the length (l) of the molded body was measured every 3 seconds after starting the temperature increase. The thermal shrinkage rate L(T) at each temperature T including T1 and T2 was determined from the above formula (1). ΔV 1300 In the measurement of ΔV, T1 was 1300°C and T2 was 1303°C. Also, in the measurement of ΔV 1500 In the measurement of ΔV, T1 was 1500°C and T2 was 1503°C. Tables 2 and 3 show the difference between ΔV 1300 and ΔV 1500 .

[0190] (Density of the molded body) The mass of the molded body sample was measured with a balance, and the volume was measured with a caliper and determined from the dimensions. The density of the molded body was determined from the obtained mass and volume.

[0191] (Density of the calcined body) The mass of the calcined body sample was measured with a balance, and the volume was measured with a caliper and determined from the dimensions. The density of the calcined body was determined from the obtained mass and volume.

[0192] (Vickers hardness) For the Vickers hardness, using a Vickers hardness tester (device name: Q30A, manufactured by Qness), under the following conditions, the indenter was statically pressed into the surface of the measurement sample, and the diagonal length of the indentation formed on the surface of the measurement sample was measured. Using the obtained diagonal length, it was determined from formula (5). Measurement sample: Disk-shaped with a thickness of 3.0 ± 0.5 mm Measurement load: 1 kgf

[0193] Prior to the measurement, a calcined body with a measurement surface polished by 0.1 mm using #800 waterproof abrasive paper was used as the measurement sample.

[0194] (Average crystal grain size, and crystal grain size difference) The average crystal grain size and the crystal grain size difference (= |surface grain size - internal grain size|) were determined by the above method using a SEM (device name: JSM-IT500LA, manufactured by JEOL Ltd.) and image analysis software (software name: Mac-View Ver.5, manufactured by MOUNTECH).

[0195] The conditions for SEM observation were as follows: The average grain size, surface grain size, and internal grain size were determined by measuring 450 ± 50 crystal grains, each. Multiple SEM observation images were used for each measurement. Acceleration voltage: 15kV Observation magnification: 5000x

[0196] Prior to the measurement, the sintered body cross-section of the sample was polished to a surface roughness of Ra ≤ 0.02 μm, and then thermally etched at a temperature 100°C lower than the sintering temperature for 30 minutes.

[0197] For the SEM observation images imported into the image analysis software, grain boundaries of crystal particles without interruption were extracted by tracing the grain boundaries within the software. After extraction, the area and equivalent diameter of the crystal particles were determined using the image analysis software, and the average crystal grain size, surface grain size, and internal grain size were determined. The absolute value of the difference between the obtained surface grain size and internal grain size was calculated and defined as the crystal grain size difference. These values ​​were obtained by processing with the image analysis software. Furthermore, for the average crystal grain size and surface grain size, the SEM observation image observed in the region 20 μm from the surface of the sintered body (1% of the thickness from the surface of the sintered body) was used, and for the internal grain size, the SEM observation image observed in the region 800 μm from the surface of the sintered body (40% of the thickness from the surface of the sintered body) was used.

[0198] (light transmittance) Light transmittance (total light transmittance) was measured using a haze meter (device name: NDH4000, manufactured by Nippon Denshoku Co., Ltd.) with a D65 light source, in accordance with the method compliant with JIS K 7361-1. The measurement sample was a 1 mm thick disc-shaped sintered body that had been polished on both sides to a surface roughness of Ra ≤ 0.02 μm.

[0199] (Light transmittance ratio) The light transmittance ratio was calculated by determining the ratio of the light transmittance [%] of the short-time sintered body (described later) to the light transmittance [%] of the normally sintered body (described later).

[0200] (Biaxial bending strength) Biaxial bending strength was measured according to the method specified in JIS T 6526. Ten measurements were taken, and the average value was calculated. The measurements were performed on a disc-shaped sintered sample with a diameter of 14.5 mm ± 0.5 mm and a thickness of 1.25 mm ± 0.05 mm, using a support circle radius of 6 mm and an indenter radius of 0.7 mm. The crosshead speed was set to 0.5 mm / min.

[0201] (Weibull coefficient) The Weibull coefficient was calculated according to the method specified in JIS R 1625. A circular sintered body with a diameter of 14.5 mm ± 0.5 mm and a thickness of 1.25 mm ± 0.05 mm was used as the measurement sample. Biaxial bending strength was measured 15 times with a support circle radius of 6 mm and an indenter radius of 0.7 mm, and the Weibull coefficient was determined using the calculation method described above.

[0202] <Manufacturing of powdered compositions> [Example 1] Hydrated zirconia sol obtained by hydrolyzing an aqueous solution of zirconium oxychloride was mixed with yttria (Y2O3) to a yttrium content of 2.5 mol%, and then dried. Subsequently, it was heat-treated at 1160°C for 2 hours in an air atmosphere to obtain a calcined powder with a matrix of yttrium-containing zirconia (yttrium-stabilized zirconia) with a yttrium content of 2.5 mol%. The obtained calcined powder and pure water were mixed and ground in a ball mill for 18 hours using 2 mm diameter beads as the grinding medium. The resulting product had a matrix of zirconia with a yttrium content of 2.5 mol%, and a BET specific surface area of ​​11.9 m². 2 A slurry containing a powder (yttrium-stabilized zirconia powder) at a concentration of / g was obtained and designated as Slurry A of Example 1.

[0203] Except for mixing yttrium to a yttrium content of 5.5 mol% and grinding for 10 hours, the matrix was made of zirconia with a yttrium content of 5.5 mol% (yttrium-stabilized zirconia) and a BET specific surface area of ​​9.7 m², using the same method as slurry A. 2A slurry containing powder at / g was obtained. This was designated as Slurry B of Example 1. The BET specific surface area of ​​the powder contained in Slurry A was 2.2 m² greater than the BET specific surface area of ​​the powder contained in Slurry B. 2 The / g was large.

[0204] Slurry A was added to and mixed with agitated slurry B so that the yttrium content in the powder composition was 4.5 mol%. Then, under air circulation at 110°C, the mixture was dried to form zirconia with a yttrium content of 4.5 mol% (yttrium-stabilized zirconia) as the matrix, with a BET specific surface area of ​​10.4 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias (stabilized zirconia powders contained in the two slurries) in the powder composition was 3.0 mol%.

[0205] [Example 2] Slurry A was added to and mixed with slurry B so that the yttrium content in the powder composition was 5.2 mol%. Otherwise, in the same manner as in Example 1, zirconia with a yttrium content of 5.2 mol% (yttrium-stabilized zirconia) was used as the matrix (main component), and the BET specific surface area was 9.9 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in the powder composition was 3.0 mol%.

[0206] [Example 3] A mixture of hydrated zirconia sol and yttria was dried and then heat-treated at 1125°C for 6 hours in an air atmosphere, followed by pulverization in a ball mill for 8 hours. Otherwise, the process was the same as in Example 1, using zirconia with a yttrium content of 2.5 mol% (yttrium-stabilized zirconia) as the matrix, with a BET specific surface area of ​​9.7 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry A of Example 3. The BET specific surface area of ​​the powder contained in Slurry A was equal to the BET specific surface area of ​​the powder contained in Slurry B of Example 1.

[0207] Slurry A from Example 3 was added to and mixed with Slurry B from Example 1 so that the yttrium content in the powder composition was 5.2 mol%. Otherwise, using the same method as in Example 1, a zirconia matrix with a yttrium content of 5.2 mol% (yttrium-stabilized zirconia) was prepared, with a BET specific surface area of ​​9.7 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in the powder composition was 3.0 mol%.

[0208] [Example 4] A mixture of hydrated zirconia sol and yttria was dried and then heat-treated at 1045°C for 6 hours in an air atmosphere, followed by 7 hours of grinding using a ball mill. Otherwise, the same method as in Example 1 was used to create a matrix of zirconia with a yttrium content of 2.5 mol% (yttrium-stabilized zirconia) with a BET specific surface area of ​​14.4 m². 2 A slurry containing powder at / g was obtained. This was designated as Slurry A of Example 4. The BET specific surface area of ​​the powder contained in Slurry A was 4.7 m² greater than the BET specific surface area of ​​the powder contained in Slurry B of Example 1. 2 The / g was large.

[0209] Except for adding and mixing slurry A of Example 4 to slurry B of Example 1 so that the yttrium content in the powder composition was 5.2 mol%, the matrix was zirconia (yttrium-stabilized zirconia) with a yttrium content of 5.2 mol%, and the BET specific surface area was 10.2 m², in the same manner as in Example 1. 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in the powder composition was 3.0 mol%.

[0210] [Example 5] Slurry A was added to and mixed with slurry B so that the yttrium content in the powder composition was 5.4 mol%. Except for this, the same method as in Example 1 was used to prepare a matrix of zirconia with a yttrium content of 5.4 mol%, and a BET specific surface area of ​​9.8 m². 2A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in the powder composition was 3.0 mol%.

[0211] [Example 6] A mixture of hydrated zirconia sol and yttria was dried and then heat-treated at 1145°C in an air atmosphere. Otherwise, the process was the same as in Example 1, using zirconia with a yttrium content of 5.5 mol% (yttrium-stabilized zirconia) as the matrix, with a BET specific surface area of ​​10.8 m². 2 A slurry containing powder at / g was obtained. This was designated as Slurry B of Example 6. Slurry A of Example 4 was used for Slurry A. The BET specific surface area of ​​the powder contained in Slurry A was 3.6 m² greater than the BET specific surface area of ​​the powder contained in Slurry B. 2 The / g was large.

[0212] Except for adding and mixing slurry A of Example 4 to slurry B so that the yttrium content in the powder composition was 5.2 mol%, the matrix (yttrium-stabilized zirconia) was made in the same manner as in Example 1, with a yttrium content of 5.2 mol%, and a BET specific surface area of ​​11.2 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in this powder composition was 3.0 mol%.

[0213] [Example 7] Yttria was mixed in the yttrium-stabilized zirconia so that the yttrium content was 1.5 mol%. Otherwise, using the same method as in Slurry A of Example 1, zirconia with a yttrium content of 1.5 mol% was used as the matrix, and the BET specific surface area was 11.9 m². 2 A slurry containing powder (yttrium-stabilized zirconia powder) at a concentration of / g was obtained. This was designated as Slurry A of Example 7. Slurry B of Example 1 was used for Slurry B. The BET specific surface area of ​​the powder contained in Slurry A of Example 7 was 2.2 m² higher than the BET specific surface area of ​​the powder contained in Slurry B of Example 1. 2 The / g was large.

[0214] Except for adding and mixing slurry A to slurry B so that the yttrium content in the powder composition was 5.2 mol%, the matrix was zirconia (yttrium-stabilized zirconia) with a yttrium content of 5.2 mol%, and the BET specific surface area was 9.9 m². 2 A powder composition with a concentration of / g was obtained. Furthermore, the difference in the amount of stabilizing elements between the two stabilized zirconias contained in the powder composition was 4.0 mol%.

[0215] [Example 8] Yttria was mixed in the yttrium-stabilized zirconia so that the yttrium content was 6.5 mol%. Otherwise, the matrix was made of zirconia with a yttrium content of 6.5 mol%, using the same method as in Slurry B of Example 1, with a BET specific surface area of ​​10.3 m². 2 A slurry containing powder (yttrium-stabilized zirconia powder) at a concentration of / g was obtained. This was designated as Slurry B of Example 8. Slurry A of Example 1 was used for Slurry A. The BET specific surface area of ​​the powder contained in Slurry A of Example 1 was 1.6 m² higher than the BET specific surface area of ​​the powder contained in Slurry B of Example 8. 2 The / g was large.

[0216] Slurry A was added to and mixed with slurry B so that the yttrium content in the powder composition was 5.2 mol%. Otherwise, the same method as in Example 1 was used to prepare a matrix of zirconia with a yttrium content of 5.2 mol%, and a BET specific surface area of ​​10.8 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in this powder composition was 4.0 mol%.

[0217] [Example 9] Using slurry A and slurry B from Example 1, slurry A was added to the stirred slurry B so that the yttrium content in the powder composition was 5.0 mol%, thereby obtaining a mixed slurry. The mixed slurry was stirred using a power of 0.5 kW / m². 3After mixing for 0.5 hours, it was dried. In this way, zirconia with a yttrium content of 5.0 mol% (yttrium-stabilized zirconia) was used as the matrix, and the BET specific surface area was 10.1 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in this powder composition was 3.0 mol%.

[0218] [Example 10] Using slurry A and slurry B from Example 1, slurry A was added to the stirred slurry B so that the yttrium content in the powder composition was 5.0 mol%, thereby obtaining a mixed slurry. The mixed slurry was stirred using a power of 0.01 kW / m². 3 After mixing for 0.5 hours, it was dried. In this way, zirconia with a yttrium content of 5.0 mol% (yttrium-stabilized zirconia) was used as the matrix, and the BET specific surface area was 10.1 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements between the two stabilized zirconias contained in this powder composition was 3.0 mol%.

[0219] [Comparative Example 1] A hydrated zirconia sol obtained by hydrolysis of an aqueous zirconium oxychloride solution was mixed with yttria to a yttrium content of 2.5 mol%, and the mixture was dried. The resulting dried product was heat-treated at 1160°C for 2 hours in an air atmosphere to obtain a powder with a matrix of zirconia containing yttrium with a yttrium content of 2.5 mol%. The obtained powder, α-alumina, and pure water were mixed. The mixing was performed by grinding and mixing for 8 hours using a ball mill with 2 mm beads as the grinding medium. As a result, a zirconia matrix with a yttrium content of 2.5 mol%, containing 0.05 mass% alumina, and having a BET specific surface area of ​​10.0 m² was obtained. 2 A slurry containing a powder (alumina-containing yttrium-stabilized zirconia powder) at a concentration of / g was obtained. This was designated as Slurry A of Comparative Example 1.

[0220] Except for setting the yttrium content in the yttrium-stabilized zirconia to 5.5 mol% and setting the grinding and mixing time in a ball mill to 10 hours, the same method as for slurry A was used to create a matrix of zirconia with a yttrium content of 5.5 mol%, containing 0.05 mass% alumina, and having a BET specific surface area of ​​10.0 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry B of Comparative Example 1. The BET specific surface area of ​​the powder contained in Slurry A was equal to the BET specific surface area of ​​the powder contained in Slurry B.

[0221] Slurry A and slurry B were mixed so that the yttrium content in the powder composition was 4.0 mol%, and then dried. In this way, a zirconia matrix with a yttrium content of 4.0 mol% was obtained, containing 0.05 mass% alumina, and having a BET specific surface area of ​​10.0 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements in the stabilized zirconia contained in this powder composition was 3.0 mol%.

[0222] [Comparative Example 2] Yttria was mixed into the yttrium-stabilized zirconia so that the yttrium content was 1.5 mol%, and then heat-treated at 1130°C. Otherwise, the process was the same as in Comparative Example 1 (Slurry A), using zirconia with a yttrium content of 1.5 mol%, an alumina content of 0.05 mass%, and a BET specific surface area of ​​11.4 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry A of Comparative Example 2. The BET specific surface area of ​​the powder contained in Slurry A was 1.4 m² higher than the BET specific surface area of ​​the powder contained in Slurry B of Comparative Example 1. 2 The / g was large.

[0223] Slurry A and slurry B were mixed in the same manner as in Comparative Example 1, except that slurry A was used. In this way, a matrix was obtained with zirconia having a yttrium content of 5.2 mol%, containing 0.05 mass% alumina, and having a BET specific surface area of ​​10.1 m². 2A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements in the stabilized zirconia contained in this powder composition was 4.0 mol%.

[0224] [Comparative Example 3] The powder composition of Comparative Example 3 was obtained by the same method as in Example 12 of Japanese Patent Publication No. 2021-059489. Specifically, yttria was mixed so that the yttrium content in the yttrium-stabilized zirconia was 2.0 mol%, and α-alumina was not mixed. Except for this, the same method as in Slurry A of Comparative Example 1 was used, with zirconia having a yttrium content of 2.0 mol% as the matrix, and a BET specific surface area of ​​10.2 m². 2 A slurry containing powder at / g was obtained. This was designated as Slurry A of Comparative Example 3. The BET specific surface area of ​​the powder contained in Slurry A was 2.2 m² greater than the BET specific surface area of ​​the powder contained in Slurry B of Comparative Example 3. 2 The / g was small.

[0225] The slurry was prepared in the same manner as slurry B of Comparative Example 1, except that yttria was mixed so that the yttrium content in the yttrium-stabilized zirconia was 8.5 mol%, the heat treatment temperature was set to 1130°C, and α-alumina was not mixed. As a result, a zirconia matrix with a yttrium content of 8.5 mol% was obtained, with a BET specific surface area of ​​12.4 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry B of Comparative Example 3.

[0226] The obtained slurries A and B were used. Except for this, the same method as in Comparative Example 1 was used, with zirconia having a yttrium content of 5.2 mol% as the matrix, and a BET specific surface area of ​​11.3 m². 2 A powder composition with a concentration of / g was obtained. The difference in the amount of stabilizing elements in the stabilized zirconia contained in this powder composition was 6.5 mol%.

[0227] [Comparative Example 4] Using a method similar to slurry B in Comparative Example 1, a matrix of zirconia with a yttrium content of 5.5 mol% was prepared, and the BET specific surface area was 10.0 m².2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry B of Comparative Example 4.

[0228] The resulting slurry B is dried to form a matrix of zirconia with a yttrium content of 5.5 mol%, containing 0.05 mass% alumina, and having a BET specific surface area of ​​10.0 m². 2 A powder (alumina-containing yttrium-stabilized zirconia powder) was obtained at a concentration of / g. This was used as the powder (powder composition) for Comparative Example 4.

[0229] [Comparative Example 5] Except for the absence of α-alumina, the same method as in Comparative Example 1's slurry B was used, with zirconia having a yttrium content of 5.5 mol% as the matrix and a BET specific surface area of ​​10.0 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry B of Comparative Example 5.

[0230] The resulting slurry B is dried, and a zirconia matrix with a yttrium content of 5.5 mol% is used, with a BET specific surface area of ​​10.0 m². 2 A powder (yttrium-stabilized zirconia powder) with a concentration of / g was obtained. This was used as the powder (powder composition) for Comparative Example 5.

[0231] [Comparative Example 6] Except for not mixing in α-alumina and setting the calcination temperature to 1140°C, the same method as for slurry A in Comparative Example 1 was used, with zirconia having a yttrium content of 2.5 mol% as the matrix and a BET specific surface area of ​​11.3 m². 2 A slurry containing powder at a concentration of / g was obtained. This was designated as Slurry A of Comparative Example 6.

[0232] The slurry was prepared in the same manner as slurry B of Comparative Example 1, except that yttria was mixed so that the yttrium content in the yttrium-stabilized zirconia was 7.5 mol%, and α-alumina was not mixed. As a result, a zirconia matrix with a yttrium content of 7.5 mol% was obtained, with a BET specific surface area of ​​11.9 m². 2A slurry containing powder at / g was obtained. This was designated as Slurry B of Comparative Example 6. The BET specific surface area of ​​the powder contained in Slurry A was 0.6 m² greater than the BET specific surface area of ​​the powder contained in Slurry B. 2 The / g was small.

[0233] Except for using the obtained slurries A and B, and mixing the two slurries so that the yttrium content was 6.0 mol%, the same method as in Comparative Example 1 was used to prepare a matrix of zirconia with a yttrium content of 6.0 mol% and a BET specific surface area of ​​11.6 m². 2 A powder composition with a concentration of / g was obtained. This was designated as the powder composition for Comparative Example 6. The difference in the amount of stabilizing elements in the stabilized zirconia contained in this powder composition was 5.0 mol%.

[0234] Table 1 shows the amount of stabilizing elements (Y2O3:mol%) in the powder contained in each slurry prepared in each example and comparative example, and the difference in the amount of stabilizing elements (difference in Y2O3). Table 2 shows the amount of stabilizing elements (mol%) of Y2O3, the oxide content of the added elements, and the properties of the powder compositions obtained in each example and comparative example.

[0235] [Table 1]

[0236] [Table 2]

[0237] Examples 2 to 4 and 6 to 8 all have the same amount of stabilizing element (yttrium) in the powder composition. Compared to Example 2, Example 4 has a higher BET specific surface area of ​​yttrium-containing zirconia with a yttrium content of 2.5 mol%, and the ΔV of the powder composition is also higher. 1300 and ΔV 1500It can be confirmed that it is fast. Furthermore, for Example 2, Example 3 containing yttria-containing zirconia with a lower BET specific surface area and a yttria content of 2.5 mol% has a lower BET specific surface area of the obtained powder composition, but ΔV 1500 becomes faster compared to Example 2. From the comparison between Example 4 and Comparative Example 2, it can be confirmed that by containing alumina, ΔV 1300 becomes faster.

[0238] For Example 2, in Example 7, the amount of yttrium in the yttria-containing zirconia with a lower amount of yttrium is lower. In this case, it can be confirmed that ΔV 1300 and ΔV 1500 are slower for Example 7 than for Example 2. For Example 2, in Example 8, the amount of yttrium in the yttria-containing zirconia with a higher amount of yttrium is 6.5 mol%, which is higher compared to Example 2, and it can be confirmed that ΔV 1300 and ΔV 1500 are faster.

[0239] For Example 4, in Example 6, the BET specific surface area of the yttria-containing zirconia with a yttrium amount of 5.5 mol% is high, and it can be confirmed that ΔV 1300 is fast and ΔV 1500 is slow for the powder composition.

[0240] <Measurement of the amount of stabilizing element by STEM-EDS> The amount of stabilizing element of the powder composition obtained in Example 2 was determined by STEM-EDS measurement (n = 1). Specifically, the composition of 10 non-overlapping powder particles was measured, and the frequency when the data interval (class interval) of the amount of stabilizing element was 0.1 mol% was determined. The measurement results were as shown in Figure 3. The maximum value of the yttrium amount in the powder particles of the yttria-containing zirconia was 6.5 mol%, and the minimum value was 2.7 mol%. Therefore, the difference (distribution width) between the maximum value and the minimum value of the yttrium amount was 3.8 mol%. From this, it was confirmed that the powder composition obtained in Example 2 contains two or more stabilized zirconias with different amounts of stabilizing elements.

[0241] The powder composition obtained in Example 2 was subjected to two more STEM-EDS measurements (n=2, n=3). Each measurement was performed using different powder particles. These measurements were performed in the same manner as in the case of n=1.

[0242] The distribution range of yttrium content (difference between the maximum and minimum values) was 3.8 mol% for n=1, 4.4 mol% for n=2, and 3.7 mol% for n=3. These results confirmed that the powder composition of Example 2 had sufficiently small variation in distribution range. Therefore, it was confirmed that stabilized zirconia particles with varying yttrium content were dispersed with high uniformity in the powder composition of Example 2.

[0243] STEM-EDS measurements were performed on the powder composition obtained in Comparative Example 5 using the same procedure as for the powder composition in Example 2 (n=1 only). As a result, the maximum value of yttrium content in the zirconia powder particles was 6.4 mol%, and the minimum value was 4.9 mol%. Thus, the difference (distribution range) between the maximum and minimum values ​​of yttrium content was 1.5 mol%. Since the difference in Y2O3 for Comparative Example 5 shown in Table 1 was also 0 mol%, it was confirmed that the powder composition obtained in Comparative Example 5 did not contain two or more stabilized zirconia with different amounts of stabilizing elements.

[0244] <Manufacturing of a flammable body> [Examples 11-17, Comparative Example 7 and Comparative Example 9] The powder compositions obtained in the same manner as in Examples 2 and 5-10, and Comparative Examples 2, 3, and 5, were each filled into a 25 mm diameter mold and molded by uniaxial pressure press molding at a pressure of 49 MPa and CIP treatment at a pressure of 196 MPa to obtain molded bodies. The obtained molded bodies were calcined in an air atmosphere at a calcination temperature of 1000°C for 1 hour to obtain calcined bodies of Examples 11-17 and calcined bodies of Comparative Examples 7 to 9. The powder compositions used in each example and comparative example, and the properties of the calcined bodies are shown in Table 3.

[0245] [Table 3]

[0246] The ΔV of Example 2 1300 is 0.058% / °C -1 and the ΔV of Example 11 1300 is 0.060% / °C -1 It can be confirmed from this that the powder composition and the calcined body obtained by calcining the powder composition have equivalent ΔV 1300 It can be confirmed that the calcined body of Example 11 has a T + C phase ratio of 100%. From this, it can be confirmed that the T + C phase ratio becomes higher by heat treatment than that of the powder composition. Examples 12 to 17 and Examples 5 to 10 which are precursors have equivalent ΔV 1300 It can be confirmed that they have. It can be confirmed that the calcined bodies of Examples 13 to 17 have a T + C phase ratio of 100%.

[0247] It can be confirmed that the calcined bodies of each example have a Vickers hardness suitable for shape processing such as CAM processing.

[0248] <Measurement of the amount of stabilizing element (yttrium amount) by STEM-EDS> The calcined body obtained in Example 11 was dry pulverized in a mortar, and in the same manner as the powder composition of Example 2, the amount of yttrium in the calcined body was measured by STEM-EDS measurement. The measurement results were as shown in Fig. 4. The maximum value of the amount of yttrium in the powder particles of stabilized zirconia was 6.2 mol%, and the minimum value was 2.9 mol%. Therefore, the difference (distribution width) between the maximum value and the minimum value of the amount of yttrium was 3.3 mol%. From this, it was confirmed that the calcined body obtained in Example 11 contains two or more stabilized zirconias having different amounts of stabilizing elements.

[0249] The yttrium content of the calcined material obtained in Comparative Example 9 was measured in the same manner as in Example 11. The measurement results are shown in Figure 5. The maximum yttrium content of the stabilized zirconia powder particles was 6.5 mol%, and the minimum was 5.0 mol%. Therefore, the difference (distribution range) between the maximum and minimum yttrium content was 1.5 mol%. Since the difference in Y2O3 for Comparative Example 5 shown in Table 1 was also 0 mol%, it was confirmed that the calcined material obtained in Comparative Example 9 did not contain two or more stabilized zirconia with different amounts of stabilizing elements.

[0250] <Manufacturing of sintered bodies> [Examples 18-27 and Comparative Examples 10-15] The powder compositions obtained in Examples 1 to 10, and the powder compositions and powders obtained in Comparative Examples 1 to 6, were each filled into a mold with a diameter of 25 mm, and molded bodies were obtained by uniaxial pressure press molding at a pressure of 49 MPa and CIP treatment at a pressure of 196 MPa.

[0251] Each of the obtained molded bodies was calcined in an air atmosphere at a calcination temperature of 1000°C for 1 hour to obtain calcined bodies. The obtained calcined bodies were heated in an air atmosphere from room temperature to 1050°C at a heating rate of 250°C / min, and from 1050°C to 1580°C at a heating rate of 50°C / min. After heating, the sintering temperature was held at 1580°C for 8 minutes, and then cooled to 900°C at a heating rate of 60°C / min. The sintered bodies were then removed from the sintering furnace (hereinafter also referred to as the "short-time sintering program") to obtain the sintered bodies of Examples 18 to 27 and Comparative Examples 10 to 15 (hereinafter also referred to as the "short-time sintered bodies").

[0252] Furthermore, the calcined body obtained using the same procedure was sintered in an air atmosphere at a heating rate of 600°C / hour and a sintering temperature of 1500°C for 2 hours to obtain a sintered body (hereinafter also referred to as "normally sintered body"). The ratio of the light transmittance of the short-time sintered body to the light transmittance of the normally sintered body obtained in this way (light transmittance ratio) [%] was determined. The results are shown in Table 4.

[0253] [Table 4]

[0254] While the conventional sintered body in Comparative Example 10 had low light transmittance, it can be confirmed that all other conventional sintered bodies had light transmittances exceeding 45%.

[0255] The light transmittance of the sintered bodies (short-time sintered bodies) in each example exceeded 45%, confirming that they possessed the light transmittance required for use as anterior dentures. On the other hand, the light transmittance of the sintered bodies (short-time sintered bodies) in each comparative example was 45% or less, and they did not possess the light transmittance required for anterior dentures.

[0256] Comparative Example 10, which has a yttrium content of 4.0 mol%, has ΔV 1300 0.07%℃ -1 Despite exceeding the limit, it was confirmed that there was no change in light transmittance between the normally sintered body and the short-time sintered body. However, in Comparative Example 10, the light transmittance was 45% or less even in the normally sintered body, and it did not have the light transmittance to be used as an anterior denture.

[0257] ΔV 1300 0.07%℃ -1 The short-time sintered body of Comparative Example 11, obtained from the powder composition of Comparative Example 2 exceeding [a certain value], exhibits significantly reduced translucency compared to a normally sintered body and is confirmed to lack the translucency suitable for use as an anterior denture.

[0258] The powder composition of Comparative Example 3 containing stabilized zirconia with a yttrium content exceeding 8.0 mol%, the powder of Comparative Example 5 not containing two or more stabilized zirconias with different stabilizing element content, and the powder composition of Comparative Example 6 with a stabilizing element content (yttrium content) of 5.8 mol% or more are all ΔV 1300 0.07%℃ -1 The following is the result. Nevertheless, in Comparative Examples 12, 14, and 15, which used these powder compositions, the translucency of the short-time sintered body was significantly reduced compared to the normally sintered body. Therefore, it was confirmed that the translucency suitable for use as anterior dentures could not be obtained.

[0259] Table 5 shows the evaluation results of the short-time sintered bodies obtained in Examples 19 to 27 and Comparative Examples 10 to 14.

[0260] [Table 5]

[0261] The average grain size of the sintered bodies in each example shown in Table 5 was 2.5 μm or less, and the grain size difference was also small. These were all sintered bodies with a stabilized zirconia matrix consisting mainly of a tetragonal prime phase. In other words, it can be confirmed that these are sintered bodies of stabilized zirconia whose crystalline phase consists of a tetragonal prime phase. The sintered body of Example 19 had a biaxial bending strength of 745 MPa. It was confirmed that the grain size difference of the sintered bodies in each example was 0.10 μm or less. The sintered bodies of Examples 21 to 26 had a biaxial bending strength of 800 MPa or more, so it was confirmed that they can be used for bridges with 4 or more teeth based on JIS T 6526.

[0262] The Weibull coefficient of the sintered body in Example 26 was 8.0, and the Weibull coefficient of the sintered body in Example 27 was 3.2. Thus, the sintered body in Example 26, in which the required stirring power during the preparation of the powder composition was kept within a preferred range, was able to achieve a higher Weibull coefficient than the sintered body in Example 27.

[0263] The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2021-150878, filed on September 16, 2021, are incorporated herein by reference as the disclosure of the specification.

Claims

1. The content of the stabilizing element is greater than 4.0 mol% and less than or equal to 5.8 mol%, The BET specific surface area is 5 m² / g or more. Under an atmospheric environment, the total light transmittance measured according to JIS K7361-1 is greater than 45% when the temperature is raised from room temperature to 1050°C at a rate of 250°C / min, then from 1050°C to 1580°C at a rate of 50°C / min, held at a sintering temperature of 1580°C for 8 minutes, and then cooled to 900°C at a rate of 60°C / min, and furthermore, A calcined stabilized zirconia body in which the ratio [%] of the total light transmittance measured in accordance with JIS K7361-1 when

2. The density of the calcined material is 2.95 g / cm³. ３ The above is the calcined body according to claim 1.

3. The calcined body according to claim 1 or 2, wherein the tetragonal and cubic fractions are 75% or more.

4. The Vickers hardness is 35 kgf / mm². ２ The above is the calcined body according to claim 1 or 2.

5. The calcined body according to claim 1 or 2, comprising two or more stabilized zirconia with different content of stabilizing elements.

6. The calcined body according to claim 1 or 2, wherein the rate of change of thermal shrinkage per unit temperature at 1300°C is 0.02%°C - 1 or more.

7. The calcined body according to claim 5, comprising an element having the function of coloring zirconia.

8. A method for manufacturing a sintered body using the calcined body described in claim 1 or 2.

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