Black sintered body and its manufacturing method

Abstract

To provide a sintered body that reduces the content of coloring agent compared to a conventional sintered body, and exhibits color tone visible as a black color without assuming hue.SOLUTION: A sintered body includes a solid solution containing cobalt and iron, and the balance zirconia. A total amount of a content of cobalt in terms of CoO and a content of iron in terms of Fe2O3 is over 0.1 wt.% and less than 3.0 wt.%, and a percentage of the cobalt region over 5.5 μm2 occupied in element mapping by an electron beam microanalyzer is equal to or less than 25%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sintered body containing a colorant and zirconia, and more particularly to a sintered body containing a colorant and zirconia and exhibiting a black color. [Background technology]

[0002] Coloring of sintered bodies, i.e., changing the color tone of zirconia sintered bodies from the inherent color tone of zirconia, has been studied for some time. To obtain a black sintered body, a sintered body has been reported in which a compound containing chromium (Cr) is used as a colorant, and this is mixed with zirconia and sintered (e.g., Patent Document 1). Patent Document 1 also discloses that a black sintered body can be obtained by using cobalt (Co) or iron (Fe) as a colorant, and mixing and sintering this with zirconia.

[0003] However, because chromium is an element that is difficult to handle, studies have been conducted to color sintered bodies without using chromium (Patent Documents 2 and 3). For example, a sintered body obtained by using cobalt oxide and iron oxide as colorants and firing it in air (Patent Document 2) and a sintered body containing a new colorant made of a Co-Zn-Fe-Al composite oxide (Patent Document 3) have been reported as black zirconia sintered bodies. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-342036 [Patent Document 2] Japanese Patent Application Publication No. 07-291630 [Patent Document 3] Japanese Patent Application Laid-Open No. 2007-308338 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional sintered bodies have a black color due to the use of a large amount of colorant or a novel colorant. In contrast, the present invention aims to provide a sintered body having a reduced colorant content compared to conventional sintered bodies, which exhibits a color tone that is visually recognized as a neutral black (hereinafter also referred to as "jet black"). [Means for solving the problem]

[0006] The present inventors have discovered that by controlling the distribution of the colorant in the sintered body, even a small amount of colorant can be used to make the sintered body appear jet black, and have completed the present invention.

[0007] That is, the gist of the present invention is as follows. [1] Contains a solid solution containing cobalt and iron, with the balance being zirconia, and the total content of cobalt converted as CoO and iron converted as Fe2O3 is more than 0.1 wt% and less than 3.0 wt%, and the elemental mapping by electron beam microanalyzer shows a value of 5.5 μm 2 A sintered body characterized in that the proportion of cobalt regions exceeding this is 25% or less. [2] 6.5 μm in elemental mapping by electron probe microanalyzer 2 The sintered body according to the above [1], wherein the proportion of iron regions exceeding this is 30% or less. [3] 5.0 μm in elemental mapping by electron probe microanalyzer 2 The sintered body according to the above [1] or [2], wherein the proportion of iron regions exceeding this is 50% or less. [4] The sintered body according to any one of [1] to [3] above, which contains aluminum oxide. [5] The sintered body according to any one of the above [1] to [4], wherein the zirconia contains at least one selected from the group consisting of yttria, calcia, magnesia, vanadia and titania. [6] The sintered body according to any one of [1] to [5] above, wherein the zirconia is zirconia containing titania and yttria. [7] The sintered body according to any one of [1] to [6] above, wherein the zirconia contains 1.0 mol % or more and 6.0 mol % or less of titania and 2.0 mol % or more and 4.0 mol % or less of yttria. [8] The sintered body according to any one of [1] to [7] above, wherein the monoclinic ratio of zirconia is 10% or less. [9] The sintered body according to any one of [1] to [8] above, wherein the average diameter of the zirconia crystal grains is 3.0 μm or less.

[10] A method for producing a sintered body according to any one of [1] to [9] above, comprising a sintering step of sintering in a reducing atmosphere a compact containing a cobalt compound and an iron compound, with the remainder being zirconia, wherein the total of the content of cobalt converted as CoO and the content of iron converted as Fe2O3 is more than 0.1 wt% and less than 3.0 wt%.

[11] The method according to the above

[10] , wherein the reducing atmosphere is an atmosphere using at least one of a reducing gas and a reducing heating element.

[12] The method according to the above

[10] or

[11] , wherein the sintering method in the sintering step is pressure sintering.

[13] The manufacturing method according to any one of the above

[10] to

[12] , which comprises a pre-sintering step of sintering the compact in a non-reducing atmosphere to obtain a pre-sintered body.

[14] The method according to any one of

[10] to

[13] above, further comprising a heat treatment step of heat treating the sintered body at a temperature of 650°C to 1100°C in an oxidizing atmosphere. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a sintered body having a jet black color and containing a reduced amount of colorant compared to conventional sintered bodies. [Brief explanation of the drawings]

[0009] [Figure 1] Elemental mapping of Example 3 ((a) backscattered electron image, (b) Fe, (c) Co) [Figure 2]Elemental Mapping of Example 17 ((a) Elemental Mapping of Co, (b) Elemental Mapping after Binarization) [Figure 3] Elemental mapping of Example 17 ((a) Y, (b) Ti) DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described.

[0011] The sintered body of this embodiment contains a solid solution containing cobalt and iron (hereinafter also referred to as a "Co-Fe solid solution"). The Co-Fe solid solution functions as a colorant that exhibits a black color. A sintered body that does not contain a Co-Fe solid solution and contains only iron or only cobalt will not be able to obtain the sintered body of this embodiment for reasons such as its color tone being different from that of the sintered body of this embodiment or being more susceptible to defects.

[0012] The Co—Fe solid solution in the sintered body of this embodiment can be confirmed by element mapping using an electron probe microanalyzer (hereinafter also simply referred to as “element mapping”).

[0013] FIG. 1 shows an example of elemental mapping of the sintered body of this embodiment. FIGS. 1(a) to 1(c) are a backscattered electron image of the sintered body (FIG. 1(a)), a mapping of iron (FIG. 1(b)), and a mapping of cobalt (FIG. 1(c)) in the same field of view. In the backscattered electron image, the zirconia base material and the Co-Fe solid solution are confirmed as light-colored regions (broken circle in FIG. 1(a)) and dark-colored regions (arrows in FIG. 1(a)), respectively. In FIG. 1(a), it can be confirmed that the Co-Fe solid solution is distributed mainly as approximately spherical regions with diameters of 0.1 μm or more and less than 3.5 μm.

[0014] In the iron and cobalt mapping, it can be seen that cobalt and iron are distributed in the same locations as the Co-Fe solid solution region in Figure 1(a) (arrows in Figures 1(a) to 1(c)). In Figures 1(b) and 1(c), the roughly spherical regions in the backscattered electron images contain cobalt and iron, confirming that the Co-Fe solid solution particles contain homogeneous solid solutions of Co and Fe. Figures 1(a) to 1(c) confirm that the Co-Fe solid solution is contained in the sintered compact as particles, even roughly spherical particles, and even roughly spherical particles with diameters of 0.1 μm to 3.5 μm.

[0015] One of the reasons why the sintered body of this embodiment contains the Co-Fe solid solution in such a distributed state is thought to be that cobalt and iron are incorporated into zirconia to form a solid solution, which then re-precipitates from the zirconia particles as fine particles.

[0016] The sintered body of this embodiment has a 5.5 μm 2 The proportion of the cobalt region exceeding (hereinafter also referred to as "Co distribution (5.5)") is 25% or less, preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and particularly preferably 3% or less. The Co distribution (5.5) is one of the indicators that shows the distribution state of the Co-Fe solid solution in the sintered body of this embodiment. By containing cobalt and iron and showing such a Co distribution (5.5), the sintered body of this embodiment shows a color tone (jet black) that is visually recognized as a colorless black.

[0017] In this embodiment, element mapping is performed at X μm 2 The proportion of the region of element M exceeding this is hereinafter also referred to as "M distribution (X)", and is represented as M distribution (X1), M distribution (X2), ..., M distribution (X n ) are collectively referred to as the "M distribution."

[0018] When the Co-Fe solid solution has an uneven distribution that affects the visible color tone, such as the presence of coarse particles or uneven distribution of Co-Fe solid solution particles, the Co distribution (5.5) exceeds 25%. In other words, the presence of coarse particles or uneven distribution of particles increases the likelihood that the sintered body will exhibit an uneven, non-uniform color tone or a color tone other than jet black. Furthermore, the presence of coarse particles or uneven distribution of particles makes it more likely that defects will occur during manufacturing.

[0019] For the same reason, the Fe distribution (6.5) is preferably 30% or less, more preferably 25% or less, even more preferably 20% or less, even more preferably 10% or less, and particularly preferably 3% or less.

[0020] In the sintered body of this embodiment, it is preferable that the Co—Fe solid solution is distributed more uniformly, and it is preferable that at least one of the Co distribution and the Fe distribution shown below is satisfied.

[0021] Co distribution (5.0): 30% or less, preferably 25% or less, more preferably 15% or less, even more preferably 10% or less, particularly preferably 5% or less Co distribution (4.5): 35% or less, preferably 30% or less, more preferably 25% or less, even more preferably 10% or less, particularly preferably 5% or less Co distribution (3.5): 55% or less, preferably 50% or less, more preferably 35% or less, even more preferably 15% or less, particularly preferably 8% or less Fe distribution (5.5): 45% or less, preferably 35% or less, more preferably 25% or less, even more preferably 15% or less, even more preferably 5% or less, particularly preferably 3.5% or less Fe distribution (5.0): 50% or less, preferably 45% or less, more preferably 40% or less, even more preferably 20% or less, particularly preferably 5% or less Fe distribution (4.5): 60% or less, preferably 50% or less, more preferably 15% or less, even more preferably 10% or less, particularly preferably 5% or less Fe distribution (3.5): 70% or less, preferably 60% or less, more preferably 20% or less, even more preferably 15% or less, particularly preferably 10% or less The sintered body of this embodiment has a 0 μm occupancy in the cobalt region in element mapping. 2 More than 2.0 μm 2 The proportion of the region below (hereinafter also referred to as the "most frequent Co region") is preferably 40% or more, and more preferably 80% or more.

[0022] The sintered body of this embodiment has a 0 μm 2 More than 2.0 μm 2 The proportion of regions containing less than 100% iron (hereinafter also referred to as "mode Fe region") is preferably 50% or more, and more preferably 60% or more.

[0023] In this embodiment, the element mapping is carried out by using a sintered body having a surface roughness (Ra) of 0.02 μm or less as a measurement sample and measuring element mapping for each element under the conditions shown below.

[0024] Measurement method: wavelength dispersion type Accelerating voltage: 15kV Irradiation current: 300nA Analysis area: 51.2μm×51.2μm Number of fields of view: 3 to 5 fields of view The M distribution, the most frequent Co region, and the most frequent Fe region can be determined from the obtained element mapping of each element by the following method.

[0025] FIG. 2 shows an example of element mapping. The minimum intensity of the characteristic X-rays observed in the element mapping (FIG. 2(b)) obtained by binarizing the element mapping (FIG. 2(a)) of each element is regarded as the background intensity, and the number of regions (hereinafter also referred to as "detection regions"; for example, arrows in FIG. 2(b)) where the intensity of the characteristic X-rays is 1.5 times or more the background intensity, and the number of regions corresponding to the area of ​​interest (hereinafter also referred to as "target regions") are counted. For example, the target region is 5.5 μm for Co(5.5). 2 The most frequent Co region is 0 μm 2 More than 2.0 μm 2 It is an area less than

[0026] The ratio of the number of target regions to the number of detection regions is calculated and used as the distribution of each element. For example, the ratio of the number of regions where the intensity of the characteristic X-rays of cobalt is 1.5 times the background intensity to the number of regions where the intensity of the characteristic X-rays of 5.5 μm is 1.5 times the background intensity. 2 The ratio of the number of regions occupying more than 5.0 μm is the Co distribution (5.5). 2 The ratio of the number of regions that occupy more than this is the Co distribution (5.0).

[0027] The binarization, detection of the detection area and the target area, and counting of their numbers can be performed using software provided with a general-purpose electron probe microanalyzer (e.g., Shimadzu Corporation's EPMA System Ver. 2.14). An example of an electron probe microanalyzer is the Shimadzu Corporation EPMA1610. Because the measurement processing methods are different, the detection area and the target area do not need to be identical in size to the Co-Fe solid solution observed in the backscattered electron image or elemental mapping.

[0028] The sintered body of this embodiment may contain at least one of cobalt oxide and iron oxide in addition to the Co—Fe solid solution.

[0029] The sintered body of this embodiment has a total (hereinafter also referred to as "colorant content") of the cobalt content calculated as CoO (hereinafter also referred to as "cobalt content") and the iron content calculated as Fe2O3 (hereinafter also referred to as "iron content") greater than 0.1 wt% and less than 3.0 wt%, preferably greater than 0.1 wt% and less than 2.5 wt%, more preferably 0.12 wt% to 2.5 wt%, and even more preferably 0.2 wt% to 1.5 wt%. If the colorant content is 0.1 wt% or less, the color tone of the sintered body will be grayish. If the colorant content is 3.0 wt% or more, defects during production and variations in color tone between individual pieces are likely to occur, making it difficult to consistently produce the sintered body of this embodiment.

[0030] Particularly preferred colorant contents of the sintered body of this embodiment are 0.1% by weight or more and less than 1.0% by weight, and further 0.2% by weight or more and less than 1.0% by weight.

[0031] In the sintered body of this embodiment, the cobalt content relative to the colorant content is preferably 0.10 or more and 0.98 or less, and more preferably 0.10 or more and 0.50 or less.

[0032] The sintered body of this embodiment may contain aluminum oxide, preferably alumina (Al2O3). When aluminum oxide is contained, the content of aluminum converted to Al2O3 (hereinafter also referred to as "alumina content") is preferably 0.1 wt% to 3.0 wt%, more preferably 0.1 wt% to 2.5 wt%, more preferably 0.2 wt% to 2.5 wt%, even more preferably 0.1 wt% to 2.0 wt%, even more preferably 0.2 wt% to 2.0 wt%, even more preferably 0.1 wt% to 1.0 wt%, and particularly preferably 0.2 wt% to 1.0 wt%. When the aluminum oxide content is 3.0 wt% or less, alumina has little effect on the color tone of the sintered body of this embodiment, and even when the colorant content is high, the formation of monoclinic zirconia tends to be suppressed. When containing aluminum oxide, the sintered body of this embodiment may contain a composite oxide of Al and Co, such as cobalt aluminate (CoAl2O4). The sintered body may contain a composite oxide such as cobalt aluminate as long as the effect of the sintered body of this embodiment is not impaired.

[0033] The sintered body of this embodiment preferably contains no impurities other than inevitable impurities such as hafnium (Hf), and is particularly preferably free of zinc (Zn) and chromium (Cr) (i.e., 0 wt%). The sintered body of this embodiment preferably has a zinc content calculated as ZnO (hereinafter also referred to as "zinc content") and a chromium content calculated as Cr2O3 (hereinafter also referred to as "chromium content") that are each less than 0.1 wt%, more preferably 0.05 wt% or less, and particularly preferably below the detection limit in general composition analysis (e.g., 0.005 wt% or less).

[0034] The sintered body of this embodiment is composed of the remainder zirconia. The sintered body of this embodiment has a content of zirconia converted into ZrO2 (hereinafter also referred to as "zirconia content") of 94.0 wt% or more, preferably 95.0 wt% or more, and more preferably 97.0 wt% or more.

[0035] In this embodiment, the cobalt content, iron content, colorant content, alumina content, zirconia content, zinc content, and chromium content are each the weight ratio of each component relative to the weight of the sintered body of this embodiment.

[0036] The zirconia (ZrO2) contained in the sintered body of this embodiment is preferably zirconia containing at least one selected from the group consisting of yttria (Y2O3), calcia (CaO), magnesia (MgO), vanadia (BaO), and titania (TiO2) (hereinafter also referred to as "solid solution component"), and more preferably zirconia containing yttria. Because the particles of the Co-Fe solid solution in the sintered body tend to be fine, the zirconia is preferably zirconia containing at least one selected from the group consisting of calcia, magnesia, vanadia, and titania, and yttria, and more preferably zirconia containing titania and yttria. Furthermore, since the particles of the Co-Fe solid solution in the sintered body tend to be particularly fine, it is particularly preferable that the total content of cobalt converted as CoO and iron converted as Fe2O3 is more than 0.1 wt% but not more than 0.4 wt%, preferably more than 0.1 wt% but not more than 0.3 wt%, and that the zirconia contains titania and yttria. In this embodiment, the finer the particles of the Co-Fe solid solution in the sintered body, the more easily the sintered body is visually recognized as having a uniform color tone.

[0037] The content of the solute components may be any amount that can dissolve in zirconia, and the content of each solute component may be, for example, 2.0 mol % or more and 10.0 mol % or less.

[0038] In this embodiment, the content of the solid solution component is the proportion (mol%) of each solid solution component relative to the total of zirconia and each solid solution component, and is a value calculated by [each solid solution component (mol)] / [each solid solution component (mol) + ZrO2 (mol)] × 100. For example, in zirconia containing yttria and titania, the yttria content (mol%) is a value calculated by [YO3 (mol)] / [YO3 (mol) + ZrO2 (mol)] × 100, and the titania content (mol%) is a value calculated by [TiO2 (mol)] / [TiO2 (mol) + ZrO2 (mol)] × 100.

[0039] For example, preferred contents of each solid solution component include at least one of the following.

[0040] Yttria content: 2.0 mol% or more and 4.0 mol% or less, preferably 2.5 mol% or more and 3.5 mol% or less Titania content: 1.0 mol% or more and 6.0 mol% or less, preferably 1.5 mol% or more and 4.8 mol% or less The sintered body of this embodiment preferably does not contain elements that dissolve in zirconia and that significantly change the color tone of the sintered body by dissolving in zirconia, such as at least one of erbia (Er2O3) and ceria (CeO2). The content of these elements is preferably below the detection limit, and taking into account measurement errors, etc., each can be, for example, 0 mol% or more and less than 1 mol%.

[0041] The sintered body of this embodiment preferably has an alumina content of 0.1% by weight or more and 2.0% by weight or less, further 0.1% by weight or more and 1.5% by weight or less, further 0.1% by weight or more and 1.0% by weight or less, or even 0.1% by weight or more and 0.5% by weight or less, and a titania content of 1.0% by weight or more and 4.0% by weight or less, further 1.0% by weight or more and 3.5% by weight or less, further 1.2% by weight or more and 3.2% by weight or less, or even 1.5% by weight or more and 3.0% by weight or less.

[0042] The zirconia crystalline phase contained in the sintered body of this embodiment may be tetragonal or cubic, as long as it has tetragonal as the main phase. The main zirconia crystalline phase contained in the sintered body of this embodiment is the phase that accounts for the largest proportion of the zirconia crystalline phase in a powder X-ray diffraction (hereinafter also referred to as "XRD") pattern measured under the following conditions.

[0043] Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Step width: 0.02° Scan speed: 5° / min Measurement range: 2θ=20° to 80° The XRD peaks of the Co-Fe solid solution and the like contained in the sintered body of this embodiment are not detected in the XRD pattern, and therefore the XRD pattern of the sintered body of this embodiment is the same as that of the zirconia crystalline phase contained in the sintered body.

[0044] In the sintered body of this embodiment, the monoclinic ratio of zirconia is preferably 10% or less, more preferably 6.5% or less, even more preferably 2% or less, and most preferably 1% or less.

[0045] The monoclinic ratio of zirconia is a value calculated from the XRD pattern of the surface of the sintered body of this embodiment measured under the above-mentioned conditions, using the following formula:

[0046] Monoclinic ratio (%) = [I m (111)+I m (11-1)] × 100 / [I m (111)+I m (11-1)+I t (111)+I c (111)] In the above equation, I m (111) is the area intensity of the (111) plane of monoclinic zirconia, I m (11-1) is the area intensity of the (11-1) plane of monoclinic zirconia, I t(111) is the area intensity of the (111) plane of tetragonal zirconia, and I c (111) is the area intensity of the (111) plane of cubic zirconia.

[0047] The average diameter of the zirconia crystal grains contained in the sintered body of this embodiment (hereinafter also referred to as "average crystal grain size") is preferably 3.0 μm or less, more preferably 2.5 μm or less. Particularly preferred average crystal grain sizes include 0.3 μm to 2.5 μm, and even more preferably 0.5 μm to 1.3 μm.

[0048] In this embodiment, the average crystal grain size can be determined by observing the surface of the sintered body of this embodiment using a scanning electron microscope at a magnification of 15,000 times, randomly extracting 200 or more zirconia crystal grains, preferably 250±50, from the obtained SEM observation image, measuring their crystal grain sizes using the intercept method (k=1.78), and averaging the measured values. In the SEM observation image of the sintered body of this embodiment, the zirconia crystal grains can be distinguished from particles other than the zirconia crystal grains, such as particles of the Co-Fe solid solution, and pores, by differences in shade.

[0049] The sintered body of this embodiment is L * a * b * In the color system, lightness L * is 10 or less, and hue a * is between -2.00 and 2.00, and hue b * It is preferable that the color tone is -2.00 or more and 5.00 or less.

[0050] Particularly preferred color tones of the sintered body of this embodiment are those having a lightness L * , hue a * and b * Any combination of the above may be mentioned.

[0051] Lightness L * : 0 or more and 9.0 or less, preferably 0 or more and 5.5 or less, More preferably, it is 0 or more and less than 3.0 hue a* : -3.00 or more and 2.00 or less, Preferably -0.50 or more and 0.50 or less hue b * : -2.00 or more and 4.00 or less, Preferably -1.00 or more and 1.00 or less L * a * b * The color tone of the color system is obtained by measuring a sintered body with a surface roughness (Ra) of 0.02 nm or less using a method based on JIS Z 8722. The color tone can be evaluated as a color tone closer to that seen with the naked eye by determining it using the SCE method, which removes specular reflection and measures diffuse reflection.

[0052] The sintered body of this embodiment preferably has a biaxial bending strength (hereinafter simply referred to as "biaxial bending strength") of 1400 MPa or more, more preferably 1700 MPa or more, measured in accordance with ISO / DIS 6872 and with a sample thickness of 1 mm. From the viewpoint of processability, the biaxial bending strength is preferably 3000 MPa or less, more preferably 2500 MPa or less.

[0053] The sintered body of this embodiment is a sintered body that exhibits a color tone that is visually recognized as a colorless black, and can be used for various components such as high-end jewelry and decorative components, for example, watch components and exterior components for portable electronic devices.

[0054] Next, a method for producing the sintered body of this embodiment will be described.

[0055] The method for producing a sintered body of this embodiment includes a sintering step of sintering in a reducing atmosphere a compact containing a cobalt compound and an iron compound, with the remainder being zirconia, and in which the total content of cobalt calculated as CoO and iron calculated as Fe2O3 is more than 0.1 wt% and less than 3.0 wt%. This allows the production of a jet-black sintered body.

[0056] In the sintering step, a sintered body is obtained by sintering a compact containing a cobalt compound and an iron compound, with the remainder being zirconia, and having a total content of cobalt converted as CoO and iron converted as Fe2O3 of more than 0.1 wt% and less than 3.0 wt%.

[0057] The molded body to be subjected to the sintering step contains a cobalt compound and an iron compound, with the remainder being zirconia. The molded body preferably contains no impurities other than unavoidable impurities. The molded body preferably does not contain zinc or chromium (i.e., the zinc content and chromium content are each 0 wt %, and preferably less than 0.1 wt %).

[0058] The cobalt compound is a compound containing cobalt (Co), and examples thereof include at least one selected from the group consisting of tricobalt tetroxide (Co3O4), cobalt (III) oxide (Co2O3), cobalt (II) oxide (CoO), cobalt oxyhydroxide (CoOOH), cobalt hydroxide (Co(OH)2), cobalt nitrate (Co(NO3)2), cobalt chloride (CoCl2), and cobalt sulfate (CoSO4), and at least one selected from the group consisting of Co3O4, Co2O3, CoO, and CoOOH is preferred.

[0059] The iron compound is a compound containing iron (Fe), and examples thereof include at least one selected from the group consisting of iron oxide (III, II) (Fe3O4), iron oxide (III) (Fe2O3), iron oxide (II) (FeO), iron oxyhydroxide (FeOOH), iron hydroxide (FeOH), iron nitrate (Fe(NO3)2), iron chloride (FeCl), and iron sulfate (FeSO4), and at least one selected from the group consisting of Fe3O4, Fe2O3, FeO, and FeOOH is preferred.

[0060] The molded body may contain an aluminum compound. The aluminum compound is a compound containing aluminum (Al), and examples thereof include alumina (Al2O3), aluminum hydroxide (Al(OH)3), aluminum chloride (AlCl3), and aluminum isopropoxide (CH9). 21At least one selected from the group consisting of aluminum nitrate (Al(NO3)3) and aluminum nitrate (Al(NO3)3) can be exemplified, and at least one of alumina and aluminum hydroxide is preferred.

[0061] The cobalt compound, iron compound, and aluminum compound may be a composite oxide containing two or more selected from the group consisting of cobalt, iron, and aluminum. Examples of the composite oxide include one or more selected from the group consisting of CoFe2O4 (cobalt ferrite), CoAl2O4 (cobalt aluminate), FeAl2O4, and FeAlO3, with CoAl2O4 being preferred.

[0062] The zirconia (ZrO2) may be zirconia containing at least one selected from the group consisting of yttria, calcia, magnesia, vanadia, and titania, and is preferably yttria-containing zirconia, more preferably yttria-containing zirconia having an yttria content of 2 mol% or more and 4 mol% or less, and even more preferably yttria-containing zirconia having an yttria content of 2.5 mol% or more and 2.5 mol% or less.

[0063] The molded body may contain a compound containing a solute component or a precursor thereof (hereinafter also referred to as a "source of solute component"). Examples of such a compound include at least one selected from the group consisting of yttrium compounds, calcium compounds, magnesium compounds, vanadium compounds, and titanium compounds. At least one of an yttrium compound and a titanium compound is preferred, and a titanium compound is more preferred.

[0064] The yttrium compound may be at least one selected from the group consisting of yttria, yttrium chloride, and yttrium hydroxide, and is preferably at least one of yttria or yttrium chloride. The calcium compound may be at least one selected from the group consisting of calcia, calcium chloride, and calcium hydroxide, and is preferably at least one of calcia or calcium chloride. The magnesium compound may be at least one selected from the group consisting of magnesia, magnesium chloride, and magnesium hydroxide, and is preferably at least one of magnesia or magnesium chloride. The vanadium compound may be at least one selected from the group consisting of vanadia, vanadium chloride, and vanadium hydroxide, and is preferably at least one of vanadia or vanadium chloride. The titanium compound may be at least one selected from the group consisting of titania, titanium chloride, titanium hydroxide, and titanium tetraisopropoxide, and is preferably at least one of titania or titanium hydroxide.

[0065] The compact has a total of the content of cobalt converted into CoO (cobalt content) and the content of iron converted into Fe2O3 (iron content) in the compact that is more than 0.1 wt% and less than 3.0 wt%, preferably more than 0.1 wt% and not more than 2.5 wt%, more preferably 0.12 wt% or more and 2.5 wt% or less, and particularly preferably 0.2 wt% or more and 1.5 wt% or less.

[0066] The ratio of the cobalt compound to the iron compound is arbitrary, but it is preferable that the weight ratio of the cobalt and iron in the compact, converted into CoO and Fe2O3, CoO / (CoO+Fe2O3), is 0.10 or more and 0.99 or less, preferably 0.10 or more and 0.50 or less.

[0067] When the molded body contains an aluminum compound, the content of aluminum in the molded body converted to Al2O3 is preferably 0.1 wt% or more and 3.0 wt% or less, more preferably 0.1 wt% or more and 2.5 wt% or less, even more preferably 0.2 wt% or more and 2.5 wt% or less, even more preferably 0.1 wt% or more and 2.0 wt% or less, even more preferably 0.2 wt% or more and 2.0 wt% or less, even more preferably 0.1 wt% or more and 1.0 wt% or less, and particularly preferably 0.2 wt% or more and 1.0 wt% or less.

[0068] The content of the solute component source can be, for example, 2.0 mol% or more and 10.0 mol% or less. The content of the solute component source is the ratio (mol%) of each solute component source, calculated as an oxide, to the total of zirconia and each solute component source calculated as an oxide, and is a value calculated by [each solute component source (mol)] / [each solute component source (mol) + ZrO2 (mol)] × 100. For example, when the compact contains an yttrium compound and a titanium compound, the content (mol%) of the yttrium compound is calculated by [YO3 (mol)] / [YO3 (mol) + ZrO2 (mol)] × 100, and the content (mol%) of the titanium compound is calculated by [TiO2 (mol)] / [TiO2 (mol) + ZrO2 (mol)] × 100.

[0069] For example, preferred contents of the sources of the solid solution components include at least one of the following.

[0070] Yttria content: 2.0 mol% or more and 4.0 mol% or less, preferably 2.5 mol% or more and 3.5 mol% or less Titania content: 1.0 mol% or more and 6.0 mol% or less, preferably 1.5 mol% or more and 4.8 mol% or less On the other hand, it is preferable that the molded body does not contain erbia (Er2O3) or ceria (CeO2) or at least one of their precursors, and the content of these is preferably below the detection limit (0 mol%), and taking into account measurement errors, etc., it can be said that each content is less than 1 mol%.

[0071] The molded product may be obtained by any method, and is preferably obtained by, for example, a step of mixing raw material compounds and molding the mixture.

[0072] The mixing may be any mixing method that can homogenize the raw material compounds. A preferred mixing method is wet mixing of the raw material compound powders. Specific examples of wet mixing include mixing using at least one selected from the group consisting of a ball mill, a bead mill, and an agitator mill. Mixing using at least one of a ball mill and a bead mill is preferred, and mixing using a ball mill using zirconia balls with a diameter of 1.0 mm to 10.0 mm as a milling medium is more preferred. In this embodiment, it is preferable to mill the raw material compound powders when wet mixing them.

[0073] Any molding method can be used as long as it can produce a molded product of the desired shape. Examples of molding methods include at least one selected from the group consisting of uniaxial pressing, cold isostatic pressing, slip casting, and injection molding. Preferred molding methods include at least one of uniaxial pressing and cold isostatic pressing, with uniaxial pressing followed by cold isostatic pressing being more preferred. Examples of conditions for uniaxial pressing include a pressure of 20 MPa or more and 70 MPa or less, and examples of conditions for cold isostatic pressing include a pressure of 150 MPa or more and 250 MPa or less.

[0074] The shape of the molded body may be any shape depending on the purpose, and examples include at least one selected from the group consisting of disk, column, cube, rectangular parallelepiped, polyhedron, approximately polyhedron, plate, sphere, and approximately spherical.

[0075] In the sintering step, the compact is sintered in a reducing atmosphere to obtain a sintered body, which contains a solid solution of cobalt and iron.

[0076] In the sintering step, the compact is sintered in a reducing atmosphere. Sintering in a reducing atmosphere promotes both solid solution formation and precipitation of cobalt and iron. Sintering in an oxidizing atmosphere alone can result in different or uneven color tones of the sintered body, making it difficult to consistently obtain the sintered body of this embodiment.

[0077] In this embodiment, the reducing atmosphere may be an atmosphere using at least one of a reducing gas and a reducing heating element. The reducing gas may be a gas containing at least one of hydrogen and carbon monoxide. The reducing heating element may be a carbon heating element.

[0078] A preferred reducing atmosphere in this embodiment is an atmosphere in which a reducing heating element is used in an inert gas, and further an atmosphere in which a carbon heating element is used in an argon or nitrogen atmosphere.

[0079] In the sintering step, any sintering method may be used, preferably either atmospheric sintering or pressure sintering, more preferably pressure sintering. Heat sintering is preferably a hot press method or a hot isostatic pressing (hereinafter also referred to as "HIP") treatment, more preferably HIP treatment. In this embodiment, atmospheric sintering is a method of sintering by simply heating the molded body without applying an external force during sintering, and pressure sintering is a method of sintering by applying an external force to the molded body during sintering and heating it.

[0080] The sintering temperature in the sintering step is 1300°C or higher and 1700°C or lower, preferably 1300°C or higher and 1675°C or lower, and more preferably 1450°C or higher and 1675°C or lower.

[0081] Preferred sintering conditions include the following:

[0082] Sintering method: HIP processing Sintering atmosphere: at least one of argon and nitrogen, preferably argon Sintering temperature: 1300℃ to 1675℃ Preferably, 1450°C or higher and 1675°C or lower Sintering time: 0.5 to 5 hours Sintering pressure: 50MPa to 200MPa Preferably, 100 MPa or more and 175 MPa or less Heating element: Carbon heater The manufacturing method of this embodiment may include a pre-sintering step of sintering the compact in a non-reducing atmosphere to obtain a pre-sintered body, prior to the sintering step.

[0083] The sintering atmosphere in the pre-sintering step may be a non-reducing atmosphere, and may be either an oxidizing atmosphere or an inert atmosphere, and is preferably an oxidizing atmosphere or, more preferably, an air atmosphere.

[0084] As long as sintering proceeds, any pre-sintering method may be used, but the pre-sintering method is preferably atmospheric sintering, and more preferably atmospheric sintering in an air atmosphere.

[0085] The pre-sintering conditions are exemplified as follows.

[0086] Pre-sintering method: Atmospheric pressure sintering Pre-sintering atmosphere: Air Pre-sintering temperature: 1300℃ to 1500℃ Preferably, the temperature is 1300°C or higher and 1450°C or lower. More preferably, 1300°C or higher and 1400°C or lower Pre-sintering time: 30 minutes to 5 hours When the manufacturing method of this embodiment includes a pre-sintering step, the pre-sintered body may be subjected to the sintering step instead of the compact.

[0087] The manufacturing method of this embodiment may include a heat treatment step of heat treating the sintered body at 650° C. or higher and 1100° C. or lower in an oxidizing atmosphere.

[0088] Any heat treatment method can be used as long as it is performed in an oxidizing atmosphere. For simplicity, the heat treatment is preferably a method in which the sintered body is simply heated without applying an external force during the heat treatment (hereinafter also referred to as "atmospheric sintering"), and more preferably atmospheric sintering in an air atmosphere.

[0089] The heat treatment temperature is preferably 650° C. or higher and 1100° C. or lower, and more preferably 700° C. or higher and 950° C. or lower. When the zirconia contains two or more solid solution components, particularly when the zirconia is zirconia containing yttria and titania, the heat treatment temperature is preferably 700° C. or higher and 950° C. or lower.

[0090] The heat treatment time may be from 1 hour to 48 hours at the above heat treatment temperature.

[0091] Particularly preferred conditions for the heat treatment step include the following.

[0092] Heat treatment method: Normal pressure firing Heat treatment atmosphere: air Heat treatment temperature: 700℃ to 1050℃ Preferably, 800°C or higher and 950°C or lower Heat treatment time: 1 hour to 10 hours [Example]

[0093] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[0094] The method for measuring the properties of the sintered body and powder of this embodiment will be described below.

[0095] (Measured density) The actual density of the sintered body samples was measured by the Archimedes method. As a pretreatment, the sintered body samples were boiled to remove any remaining bubbles on the surface of the sintered body samples.

[0096] (Crystalline phase and monoclinic ratio) The XRD pattern of the surface of the sintered body sample was measured using a powder X-ray analyzer (device name: RINT Ultima III, manufactured by Rigaku Corporation) under the following measurement conditions.

[0097] Radiation source: CuKα radiation (λ=1.5405Å) Measurement mode: Continuous scan Step width: 0.02° Scan speed: 5° / min Measurement range: 2θ=20° to 80° The crystalline phase was determined from the obtained XRD pattern, and the monoclinic ratio of zirconia was measured using the following formula.

[0098] Monoclinic ratio (%) = [I m (111)+I m (11-1)] × 100 / [I m (111)+I m (11-1)+I t (111)+I c (111)] In the above equation, I m (111) is the area intensity of the (111) plane of monoclinic zirconia, I m (11-1) is the area intensity of the (11-1) plane of monoclinic zirconia, I t (111) is the area intensity of the (111) plane of tetragonal zirconia, and I c (111) is the area intensity of the (111) plane of cubic zirconia.

[0099] (Color and reflectance) The color tone of the sintered body samples was measured according to JIS Z 8722. A general color difference meter (Spectrophotometer SD 3000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used for the measurement. The measurement conditions were as follows, and the color tone and reflectance were determined using the SCE method, which removes specular reflected light and measures diffuse reflected light.

[0100] Light source: D65 light source Viewing angle: 10° The sintered body samples used were disk-shaped sintered bodies with a surface roughness of Ra=0.02 μm or less, a thickness of 1 mm, and a diameter of 16 mm.

[0101] (biaxial bending strength) The biaxial bending strength of the sintered samples was measured using a method conforming to ISO / DIS 6872. For the measurements, disk-shaped sintered samples with a diameter of 16 mm and a thickness of 1 mm were used. The measurements were carried out three times for sintered samples prepared under the same conditions, and the average value was used as the biaxial bending strength.

[0102] (Average grain size) The average grain size of the zirconia crystal grains in the sintered body samples was measured by the intercept method.

[0103] As a pretreatment, the sintered samples were mirror-polished to a surface roughness Ra of 0.02 μm or less, followed by thermal etching. The surfaces of the sintered samples were observed using an SEM at 15,000x magnification to obtain SEM images. From the SEM images, 200 or more zirconia crystal grains (250 ± 50 grains) were randomly selected, and their grain sizes were measured using the intercept method (k = 1.78). The average of these measurements was used as the average grain size of the zirconia crystal grains.

[0104] (EPMA measurement and Co distribution measurement) Using an EPMA device (device name: EPMA1610, manufactured by Shimadzu Corporation), backscattered electron images were observed and elemental mapping was performed under the following conditions.

[0105] Measurement method: wavelength dispersion type Accelerating voltage: 15kV Irradiation current: 300nA Analysis area: 51.2μm×51.2μm Number of fields of view: 3 The analysis software attached to the EPMA1610 (product name: EPMA System Ver. 2.14, manufactured by Shimadzu Corporation) was used to digitize the obtained elemental mapping and count the number of regions where the intensity of the characteristic X-rays of cobalt or iron was 1.5 times or more that of the background. For cobalt, the intensity of the mapping result was set to 120 counts, and the areas where no particles were observed were defined as the background. The threshold for binarization was 1.5 times the average value. For iron, the intensity of the mapping result was set to 110 counts, and the areas where no particles were observed were defined as the background. The threshold for binarization was 1.5 times the average value. The Co distribution, Fe distribution, modal Co distribution, and modal Fe distribution were calculated based on the proportion of each region to the total number of measured regions.

[0106] The sintered body samples used were disk-shaped sintered bodies with a surface roughness of Ra=0.02 μm or less, a thickness of 1 mm, and a diameter of 16 mm.

[0107] Example 1 Iron oxide powder, cobalt oxide powder, and 3 mol% yttria-containing zirconia powder were wet mixed with ethanol in a ball mill using zirconia balls to obtain a mixed powder containing 0.04 wt% iron oxide, 0.16 wt% cobalt oxide, and the remainder containing 3 mol% yttria-containing zirconia. The mixed powder was dried at 110°C in air and then sieved to obtain an agglomerated powder with an agglomerated particle size of 500 μm or less.

[0108] The agglomerated powder was uniaxially pressed using a die press at a pressure of 50 MPa, and then cold isostatically pressed at a pressure of 200 MPa to obtain a disk-shaped compact with a diameter of 20 mm and a thickness of 3 mm. The compact was sintered in air at 1350°C for 2 hours to obtain a primary sintered body. The density of the primary sintered body was 5.98 g / cm. 3 It was.

[0109] The primary sintered body was subjected to HIP treatment in an argon atmosphere at 1500°C, 150 MPa, and 1 hour to obtain a sintered body. The sintered body was then sintered in an air atmosphere at 900°C and atmospheric pressure for 8 hours to obtain the sintered body of this example.

[0110] The results of elemental mapping of the sintered body of this example are shown in the table below.

[0111] [Table 1] The sintered body of this example was jet black, the Co distribution (5.5) was 0%, and no coarse particles were observed in the cobalt element mapping. It was also found that the Fe distribution was smaller than the Co distribution.

[0112] The modal Co and Fe regions were 42.4% and 65.4%, respectively.

[0113] Example 2 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.40 wt% iron oxide and 0.10 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.05 g / cm. 3 It was.

[0114] Example 3 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.25 wt% iron oxide and 0.25 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.02 g / cm. 3 It was.

[0115] Figure 1 shows a backscattered electron image (Figure 1(a)), elemental mapping of iron (Figure 1(b)), and elemental mapping of cobalt (Figure 1(c)) of the sintered body of this example. From Figure 1, it can be confirmed that the sintered body of this example contains a Co-Fe solid solution, and that the Co-Fe solid solution is contained in the sintered body as particles of 0.1 to 3.5 μm.

[0116] Furthermore, elemental mapping of the zirconia crystal particles (the dotted circle in Figure 1(a)) showed that the cobalt and iron contents of the zirconia crystal particles were below the measurement limit.

[0117] Example 4 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.10 wt% iron oxide and 0.40 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.95 g / cm. 3 It was.

[0118] The results of elemental mapping of the sintered body of this example are shown in the table below.

[0119] [Table 2] The sintered body of this example was jet black, had a Co distribution (5.5) of 18.6%, and no coarse particles were observed in the cobalt element mapping. It was also found that the Fe distribution was smaller than the Co distribution.

[0120] The modal Co and Fe regions were 38.4% and 59.9%, respectively.

[0121] Example 5 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.65 wt% iron oxide and 0.35 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.96 g / cm. 3 It was.

[0122] Comparative Example 1 The sintered body of this comparative example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.02 wt% iron oxide and 0.08 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.76 g / cm. 3 It was.

[0123] The results of elemental mapping of the sintered body of this comparative example are shown in the table below.

[0124] [Table 3] The sintered body of this comparative example had a Co distribution (5.5) of 0%, but did not contain iron, and no coarse particles were observed in the cobalt element mapping. However, the color was light gray, not jet black.

[0125] Comparative Example 2 A sintered body of this comparative example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.50% by weight of cobalt oxide and the remainder being 3 mol% yttria-containing zirconia was used. The obtained sintered body had cracks.

[0126] Comparative Example 3 The sintered body of this comparative example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.50 wt% iron oxide and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.02 g / cm. 3 It was.

[0127] Comparative Example 4 The sintered body of this comparative example was obtained in the same manner as in Example 1, except that a mixed powder containing 1.95 wt% iron oxide and 1.05 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.95 g / cm. 3 The obtained sintered body had cracks.

[0128] Element mapping was performed on the surface of the sintered body of this comparative example, which did not contain defects such as cracks. The results are shown in the table below.

[0129] [Table 4] The sintered body of this comparative example had a Co distribution (5.5) of 35.3%, cobalt and iron contents of 3.0 mass% or more, and coarse particles were confirmed in the cobalt element mapping. The sintered body had a non-uniform color tone with dark gray and dark brown areas.

[0130] Comparative Example 5 The sintered body of this comparative example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.25 wt% iron oxide and 0.25 wt% cobalt oxide, with the remainder being 3 mol% yttria-containing zirconia, was used, and that the HIP treatment and the firing after the HIP treatment were not performed. The density of the primary sintered body was 6.02 g / cm. 3 It was.

[0131] The evaluation results of Examples 1 to 5 and Comparative Examples 1 to 5 are shown in the table below.

[0132] [Table 5]

[0133] [Table 6] All of the sintered bodies of the examples were jet black in color and had a tetragonal main phase. In contrast, the sintered body containing 0.1 wt% of colorant (Comparative Example 1) and the sintered body containing no cobalt (Comparative Example 3) were dark gray and dark brown, respectively, and had a color tone that was not black.

[0134] Furthermore, the sintered body that had not been sintered in a reducing atmosphere (Comparative Example 5) was light gray in color, and the sintered body was dotted with spots and did not have a uniform color tone.

[0135] In both the sintered body containing no iron (Comparative Example 2) and the sintered body containing 3.0 wt % of colorant (Comparative Example 4), cracks occurred and a defect-free sintered body could not be obtained.

[0136] Example 6 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder containing 0.10 wt% iron oxide, 0.40 wt% cobalt oxide, and 0.25 wt% alumina, with the remainder being 3 mol% yttria-containing zirconia, was used, using iron oxide powder, cobalt oxide powder, aluminum oxide (Al2O3) powder, and 3 mol% yttria-containing zirconia. The density of the primary sintered body was 6.04 g / cm3 It was.

[0137] Example 7 The sintered body of this example was obtained in the same manner as in Example 1, except that a mixed powder of iron oxide (FeO) powder (purity 99% or more), cobalt aluminate (CoAlO) powder (purity 99% or more), and 3 mol% yttria-containing zirconia powder (purity 99.8% or more) was used, so that the mixture was 0.10 wt% iron oxide, 0.25 wt% cobalt aluminate (including 0.14 wt% AlO and 0.11 wt% CoO), and the remainder was 3 mol% yttria-containing zirconia. The density of the primary sintered body was 6.05 g / cm. 3 It was.

[0138] Example 8 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 0.50 wt% cobalt aluminate (including 0.28 wt% Al2O3 and 0.22 wt% CoO), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.05 g / cm 3 It was.

[0139] Example 9 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 1.00 wt% cobalt aluminate (including 0.56 wt% Al2O3 and 0.44 wt% CoO), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.04 g / cm 3 It was.

[0140] Example 10 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 2.00 wt% cobalt aluminate (including 1.12 wt% AlO and 0.88 wt% CoO), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.01 g / cm. 3 It was.

[0141] Example 11 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 3.00 wt% cobalt aluminate (including 1.68 wt% AlO and 1.32 wt% CoO), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.99 g / cm. 3 It was.

[0142] The results of elemental mapping of the sintered body of this example are shown in the table below.

[0143] [Table 7] The sintered body of this example was jet black, with a Co distribution (5.5) of 23.7%. No coarse particles were observed in the cobalt element mapping. It was also found that the Fe distribution was smaller than the Co distribution.

[0144] Example 12 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 5.00 wt% cobalt aluminate (including 2.8 wt% AlO and 2.2 wt% CoO), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.86 g / cm. 3 It was.

[0145] The physical properties of Examples 6 to 12 are shown in the table below.

[0146] [Table 8] The biaxial bending strength and color tone of Examples 6 to 12 are shown in the table below.

[0147] [Table 9] The sintered body (Example 3) containing 0.50% by weight of colorant and not containing alumina had a monoclinic crystal ratio exceeding 1%, whereas the sintered body containing alumina had a monoclinic crystal ratio of 0% even when the colorant content was between 0.21% by weight and 2.22% by weight.

[0148] Furthermore, since all of the sintered bodies of the examples exhibit a jet black color, it is clear that by setting the alumina content within this range (for example, 0.2% by weight or more and 2.5% by weight or less), the formation of monoclinic zirconia crystals is suppressed without affecting the color tone of the sintered body.

[0149] Example 13 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt% iron oxide, 5.00 wt% cobalt aluminate, and the remainder 3 mol% yttria-containing zirconia was used, and the HIP treatment temperature was set to 1650°C. The density of the primary sintered body was 5.84 g / cm. 3 The color tone of the sintered body of this example was jet black. The results are shown in the table below.

[0150] [Table 10] Example 14 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt % iron oxide, 5.00 wt % cobalt aluminate, and the remainder 3 mol % yttria-containing zirconia was used, and the atmospheric sintering temperature was set to 800°C.

[0151] The density of the primary sintered body is 5.84 g / cm 3 The sintered body of this example had high density, high bending strength, and a jet black color.

[0152] Example 15 The sintered body of this example was obtained in the same manner as in Example 7, except that a mixed powder containing 0.10 wt % iron oxide, 5.00 wt % cobalt aluminate, and the remainder 3 mol % yttria-containing zirconia was used, and the atmospheric sintering temperature was set to 1000°C.

[0153] The density of the primary sintered body is 5.84 g / cm 3 The sintered body of this example had high density, high bending strength, and a jet black color.

[0154] The results of Examples 14 and 15 are shown in the table below.

[0155] [Table 11] The sintered body obtained was jet black whether the atmospheric firing temperature was 800°C or 1000°C. It was also found that the color value of the sintered body obtained by atmospheric firing at 800°C was higher than that obtained by atmospheric firing at 1000°C.

[0156] Example 16 Iron oxide powder, cobalt oxide powder, titanium oxide powder, alumina powder, and 3 mol% yttria-containing zirconia powder were wet mixed with ethanol in a bead mill using zirconia beads to obtain a sintered body of this example in the same manner as in Example 1, except that a mixed powder containing 0.16 wt% iron oxide, 0.04 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.69 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.08 g / cm. 3 It was.

[0157] Example 17 The sintered body of this example was obtained in the same manner as in Example 16, except that iron oxide powder, cobalt oxide powder, titanium oxide powder, alumina powder, and 3 mol% yttria-containing zirconia powder were wet mixed with ethanol in a ball mill using zirconia balls. The density of the primary sintered body was 5.94 g / cm. 3It was.

[0158] The results of elemental mapping of the sintered bodies of Examples 16 and 17 are shown in the table below.

[0159] [Table 12] In both Examples 16 and 17, the total iron content and cobalt content was 0.2 wt%. Compared with Example 1, which had the same total iron content and cobalt content as these Examples, Examples 16 and 17 had smaller Co and Fe distributions. Furthermore, the modal Co and Fe regions of the sintered body of Example 16 were 87.0% and 74.4%, respectively. The inclusion of yttria and titania in the zirconia tended to result in a finer Co-Fe solid solution, as confirmed by elemental mapping.

[0160] Example 18 Iron oxide powder, cobalt oxide powder, titanium oxide powder, alumina powder, and 3 mol% yttria-containing zirconia powder were wet mixed with ethanol in a ball mill using zirconia balls to obtain a sintered body of this example in the same manner as in Example 1, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 1.0 wt% titanium oxide (corresponding to a titania content of 1.59 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.02 g / cm. 3 It was.

[0161] Example 19 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 2.0 wt% titanium oxide (corresponding to a titania content of 3.15 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.00 g / cm. 3 It was.

[0162] Example 20 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.70 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 5.96 g / cm. 3 It was.

[0163] Example 21 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.24 wt% iron oxide, 0.06 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.69 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.00 g / cm. 3 It was.

[0164] Example 22 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 1.0 wt% titanium oxide (corresponding to a titania content of 1.58 mol%), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.06 g / cm. 3 It was.

[0165] Example 23 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 2.0 wt% titanium oxide (corresponding to a titania content of 3.14 mol%), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 6.02 g / cm. 3 It was.

[0166] Example 24 The sintered body of this example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.4 wt% iron oxide, 0.1 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.69 mol%), and the remainder being 3 mol% yttria-containing zirconia, was used. The density of the primary sintered body was 5.99 g / cm. 3 It was.

[0167] The results of elemental mapping of the sintered bodies of Examples 18 to 24 are shown in the table below.

[0168] [Table 13] Comparative Example 6 The sintered body of this comparative example was obtained in the same manner as in Example 18, except that a mixed powder containing 0.08 wt% iron oxide, 0.02 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.68 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 6.01 g / cm. 3 It was.

[0169] The results of elemental mapping of the sintered body of this comparative example are shown in the table below.

[0170] [Table 14] The sintered body of this comparative example had a Co distribution (5.5) of 0%, but the total content of cobalt and iron was 0.1 wt% or less, and no coarse particles were observed in the cobalt element mapping. However, the color was light gray, not jet black.

[0171] The physical properties of Examples 16 to 24 and Comparative Example 6 are shown in the table below.

[0172] [Table 15] The biaxial bending strength and color tone of Examples 16 to 24 and Comparative Example 6 are shown in the table below.

[0173] [Table 16] The sintered bodies of all the examples were jet black, whereas the sintered body of Comparative Example 6, in which the colorant content was 0.10% by weight, was gray, and the lightness L * is greater than 9 and hue b * was more than 5.

[0174] FIG. 3 shows elemental mapping of titanium and yttrium for the sintered body of Example 17.

[0175] 3, titanium and yttrium show similar distributions and are both detected from the same particles. This indicates that titania and yttria are solid-dissolved in zirconia, and that the zirconia is zirconia containing titania and yttria.

[0176] Comparative Example 7 The sintered body of this comparative example was obtained in the same manner as in Example 18, except that a mixed powder containing 1.2 wt% iron oxide, 0.3 wt% cobalt oxide, 3.0 wt% titanium oxide (corresponding to a titania content of 4.68 mol%), 0.25 wt% aluminum oxide, and the remainder being 3 mol% yttria-containing zirconia was used. The density of the primary sintered body was 5.97 g / cm. 3 The obtained sintered body had cracks.

[0177] The results of elemental mapping of the sintered body of this comparative example are shown in the table below.

[0178] [Table 17] The sintered body of this comparative example had a cobalt and iron content of less than 3.0 wt%, but the Co distribution (5.5) was 29.0%, and coarse particles were confirmed in the cobalt element mapping. The sintered body had a non-uniform color tone, with dark gray and dark brown areas.

Claims

1. The solid solution contains cobalt and iron, and the balance is zirconia, and the content of cobalt converted as CoO and the content of iron converted as Fe ２ O ３ The total content calculated as a percentage of 5.5 μm in elemental mapping by an electron beam microanalyzer is more than 0.1 wt % and less than 3.0 wt %. ２ The proportion of the cobalt region exceeding L is 25% or less, and ＊ a ＊ b ＊ In the color system, lightness L ＊ is less than 3.0, and the hue a ＊ is -2.00 or more and 2.00 or less, and hue b ＊ A sintered body characterized by having a color tone of -2.00 or more and 5.00 or less.

2. The sintered body according to claim 1, which contains aluminum oxide.

3. 3. The sintered body according to claim 1, wherein the zirconia contains at least one selected from the group consisting of yttria, calcia, magnesia, vanadia, and titania.

4. 4. The sintered body according to claim 1, wherein the zirconia contains titania and yttria.

5. 5. The sintered body according to claim 1, wherein the zirconia contains 1.0 mol% or more and 6.0 mol% or less of titania and 2.0 mol% or more and 4.0 mol% or less of yttria.

6. 6. The sintered body according to claim 1, wherein the monoclinic fraction of zirconia is 10% or less.

7. 7. The sintered body according to claim 1, wherein the average diameter of the zirconia crystal grains is 3.0 μm or less.

8. The content of cobalt converted to CoO and iron converted to Fe ２ O ３ 8. The sintered body according to claim 1, wherein the content of cobalt converted as CoO is 0.10 or more and 0.98 or less relative to the total content converted as CoO.

9. 9. The sintered body according to claim 1, wherein the content of cobalt calculated as CoO is 1.32% by weight or less.

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