Red sintered body and method for producing same

Abstract

Provided is at least one of: a sintered body that exhibits, on the basis of the coloration of trivalent cerium, a red color mainly through reflected light, and that is formed of zirconia that exhibits a bright red color under daylight; and a method for producing the sintered body.　This zirconia sintered body contains cerium, aluminum, yttrium, and a color-adjustment element. The contained amount of the cerium expressed as CeO2 is 1.5-6.0 mol%, the contained amount of the aluminum expressed as Al2O3 is 0.05-4.0 mol%, the contained amount of the yttrium expressed as Y2O3 is 2.0-6.0 mol%, and the contained amount of the added color-adjustment element expressed as oxides is more than 0 mol% but not more than 4.0 mol%. The cerium includes trivalent cerium (Ce3+). The color-adjustment element is at least one element among alkaline earth metal elements and rare earth elements excluding yttrium and cerium. The ratio of the ion radius of the color-adjustment element with respect to the ion radius of tetravalent zirconium (Zr4+) is more than 1.00 but not more than 1.60.

Description

Red sintered body and its manufacturing method

[0001] The present disclosure relates to a sintered body containing zirconia as a main component and exhibiting a red color, and a method for producing the same.

[0002] For use in decorative materials and exterior parts of electronic equipment, zirconia sintered bodies containing coloring components, so-called colored zirconia sintered bodies, are in demand. Among these, cerium oxide (CeO ２ Zirconia sintered bodies containing zirconia are attracting attention.

[0003] For example, 0.5 mol % or more of CeO ２ A zirconia sintered body containing tetragonal zirconia obtained by reducing cerium has been reported as a red sintered body (Patent Document 1). ２ O ３ A translucent zirconia sintered body made of cubic crystals containing cerium oxide and neodymium oxide has been reported (Patent Document 2). Compared with previously reported red zirconia sintered bodies, the zirconia sintered body disclosed in Patent Document 2 exhibits a more reddish color tone. Furthermore, Patent Document 3 reports that a zirconia sintered body containing cerium oxide and neodymium oxide as coloring components and subjected to a reduction treatment increases the difference in reflectance between light wavelengths of 590 nm and 630 nm.

[0004] On the other hand, Patent Document 4 reports that in a red zirconia sintered body containing cerium oxide as a coloring component, the zirconia sintered body exhibits uniform coloring by coexisting an aluminum compound, and there is no change in color tone depending on the thickness of the sintered body.

[0005] Japanese Patent Publication No. 62-83366 Japanese Patent Publication No. 2011-207745 Japanese Patent Publication No. 2017-132647 Japanese Patent Publication No. 2017-75086

[0006] The zirconia sintered body of Patent Document 2 has very high translucency, and its color is developed by transmitted light. The color developed by transmitted light is a transparent color tone like that of colored glass, and the color tone changes significantly depending on the thickness of the sintered body. Therefore, when this zirconia sintered body is used as a small or thin component, the color is very weak.

[0007] In contrast, the sintered bodies of Patent Documents 1 and 3 exhibit a stable color regardless of the size of the component, since the color is primarily due to light reflected from the surface of the sintered body. The zirconia sintered bodies containing cerium oxide reported in Patent Document 1 all exhibit a reddish color tone. However, these colors were intermediate colors between orange and red, between brown and red, or between black and red, and were not pure red. Furthermore, the zirconia sintered body containing cerium oxide and neodymium oxide disclosed in Patent Document 3 was a sintered body with a stronger reddish tinge due to the inclusion of neodymium oxide, but still exhibited an intermediate color between orange and red.

[0008] The color tone of the zirconia sintered body of Patent Document 4 is an intermediate color between orange and red, and does not have the aesthetic appeal of a pure red color.

[0009] In view of these problems, the present disclosure aims to provide at least one of a zirconia sintered body that exhibits a red color mainly due to reflected light based on the color development of trivalent cerium and that exhibits a vivid red color under daylight, and a method for producing the same.

[0010] The present inventors have investigated a zirconia sintered body that contains trivalent cerium as a coloring component and that exhibits a red color when subjected to reflected light. As a result, they have found that a zirconia sintered body containing trivalent cerium as a coloring component exhibits a vivid red color in daylight when it contains aluminum and a specific color-tuning element.

[0011] That is, the present invention is as described in the claims, and the gist of the present disclosure is as follows: [1] A ceramic ceramic containing cerium, aluminum, yttrium, and a color-tuning element, and ２The content of cerium converted from Al is 1.5 mol% or more and 6.0 mol% or less. ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as an oxide is 2.0 mol% or more and 6.0 mol% or less, and the content of color-tuning elements calculated as an oxide is more than 0 mol% and 4.0 mol% or less, and the cerium is trivalent cerium (Ce ３＋ ), wherein the color-tuning element is at least one element selected from the group consisting of a rare earth element other than yttrium and cerium, and an alkaline earth metal element, and wherein the color-tuning element is at least one element selected from the group consisting of tetravalent zirconium (Zr ４＋ A zirconia sintered body, wherein the ratio of the ionic radius of the color-tuning element to the ionic radius of L is more than 1.00 and not more than 1.60. [2] The sintered body according to the above [1], wherein the zirconia contains a tetragonal crystal and a cubic crystal in its crystal structure. [3] The sintered body according to the above [1] or [2], wherein the color-tuning element is one or more selected from the group consisting of calcium, magnesium, erbium, holmium, dysprosium, terbium, gadolinium, europium, samarium, neodymium, praseodymium, and lanthanum. [4] The sintered body according to any one of the above [1] to [3], wherein the ratio of the ionic radii of the color-tuning element is more than 1.33 and not more than 1.40. [5] L ＊ a ＊ b ＊ In the color system, hue b ＊ Hue a ＊ The ratio (a ＊ / b ＊ ) is 2.0≦(a ＊ / b ＊ [6] The sintered body according to any one of the above [1] to [4], wherein the reflectance (R ７００ ) and the reflectance (R ６００ ) ratio (R ７００ / R ６００ ) is 2.4≦(R ７００ / R ６００[7] The sintered body according to any one of [1] to [5], wherein the ratio of the height of the peak top at 2θ = 37.0 ± 0.3 to the height of the peak top at 2θ = 30.0 ± 0.3 in an XRD pattern is 0.005 or less. [8] A sintered body according to any one of [1] to [6], comprising a cerium source, an aluminum source, an yttrium-containing zirconia source, and a color-tuning element source, ２ The content of cerium converted from Al is 1.5 mol% or more and 6.0 mol% or less. ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as an oxide is 2.0 mol % or more and 6.0 mol % or less, and the content of the color-tuning element calculated as an oxide is more than 0 mol % and 4.0 mol % or less, the color-tuning element source is a compound containing at least one element selected from the group consisting of a rare earth element other than yttrium and cerium and an alkaline earth metal element, and tetravalent zirconium (Zr ４＋ [9] A method for producing a sintered body according to any one of [1] to [7], comprising a molding step of molding the powder composition according to [8] to obtain a molded body, a step of sintering the molded body under atmospheric pressure to obtain a primary sintered body, and a secondary sintering step of sintering the primary sintered body in a reducing atmosphere.

[0012] The present disclosure makes it possible to provide at least one of a zirconia sintered body that exhibits a red color due to reflected light based on the color development of trivalent cerium, and that exhibits a vivid red color in daylight, and a method for producing the same.

[0013] The sintered body of the present disclosure will be described below by showing an example of an embodiment. The terms used in this embodiment are as follows.

[0014] The term "composition" refers to a substance having a certain composition, and includes, for example, one or more selected from the group consisting of powder, granules, a molded body, a calcined body, and a sintered body. The term "zirconia composition" refers to a composition essentially consisting of zirconia, and further refers to a composition having zirconia as a matrix (base material).

[0015] A "powder" is a composition that is an aggregate of powder particles and has flowability. A "zirconia powder" is a powder that is essentially composed of zirconia, or a powder that has zirconia as a matrix (base material). A "powder composition" is a composition composed of powders with different characteristics, and in particular, a composition that contains powders with different compositions.

[0016] A "molded body" is a composition having a certain shape composed of powder particles agglomerated by physical force, and in particular, a composition in a state in which the composition has not been subjected to heat treatment after imparting the shape (e.g., after molding). A "zirconia molded body" is a molded body essentially made of zirconia, and further, a molded body having zirconia as a matrix (base material).

[0017] A "sintered body" is a composition having a certain shape and composed of crystal grains, and is a composition in a state in which it has been heat-treated at a temperature equal to or higher than the sintering temperature. A "zirconia sintered body" is a sintered body essentially made of zirconia, or a sintered body having zirconia as a matrix (base material).

[0018] The "stabilizing element" is an element that has the function of stabilizing the crystalline phase of zirconia by dissolving in zirconia.

[0019] The "BET specific surface area" may be measured by a BET multipoint method (5 points) using nitrogen as the adsorption gas in accordance with JIS R 1626. Specific measurement conditions for the BET specific surface area include, for example, the following conditions.

[0020] Adsorption medium: N ２ Adsorption temperature: -196°C Pretreatment conditions: Degassing treatment in air at 250°C for 1 hour or more The BET specific surface area can be measured using a common device (for example, Tristar II 3202, manufactured by Shimadzu Corporation).

[0021] The "average particle size" is the particle size corresponding to D50 (median diameter) of the volume particle size distribution obtained by a laser diffraction / scattering method using a general particle size distribution measuring device (for example, device name: MT-3100II, manufactured by Microtrac Bell). Specific measurement conditions include the following:

[0022] Measurement range: 0.01 to 2000 μm Particle refractive index: 2.17 Particle transparency: transparent Particle shape: non-spherical Solvent refractive index: 1.333 "Atmospheric sintering" is a method of sintering by heating without applying an external force to the sintered object (such as a compact or a calcined body). [Sintered body] This embodiment is a sintered body containing cerium, aluminum, yttrium, and a color-tuning element, and ２ The content of cerium converted from Al is 1.5 mol% or more and 6.0 mol% or less. ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as an oxide is 2.0 mol% or more and 6.0 mol% or less, and the content of color-tuning elements calculated as an oxide is more than 0 mol% and 4.0 mol% or less, and the cerium is trivalent cerium (Ce ３＋ ), wherein the color-tuning element is at least one element selected from the group consisting of a rare earth element other than yttrium and cerium, and an alkaline earth metal element, and wherein the color-tuning element is at least one element selected from the group consisting of tetravalent zirconium (Zr ４＋ The present invention relates to a zirconia sintered body, wherein the ratio of the ionic radius of the color-tuning element to the ionic radius of trivalent cerium is more than 1.00 and not more than 1.60. With this configuration, the zirconia sintered body exhibits a red color due to the color development of trivalent cerium and also exhibits a vivid red color under daylight, i.e., a so-called red zirconia sintered body.

[0023] The sintered body of this embodiment contains cerium, aluminum, yttrium, and a color-tuning element. In the sintered body of this embodiment, the cerium, yttrium, and color-tuning element are preferably solid-solved in zirconia. On the other hand, aluminum is preferably contained as alumina particles.

[0024] The sintered body of this embodiment is Y ２ O ３ The converted yttrium content (hereinafter simply referred to as "yttrium content") is 2.0 mol% or more and 6.0 mol% or less. If the yttrium content is less than 2.0 mol%, defects are likely to occur during production, and sintered bodies cannot be obtained stably. On the other hand, if the yttrium content exceeds 6.0 mol%, the strength decreases.

[0025] The yttrium content of the sintered body of this embodiment may be 2.0 mol% or more, 2.2 mol% or more, 2.4 mol% or more, or 2.5 mol% or more, and 6.0 mol% or less, 5.5 mol% or less, 5.0 mol% or less, 4.5 mol% or less, or 4.0 mol% or less. Preferred yttrium contents include, for example, 2.0 mol% or more and 6.0 mol% or less, 2.2 mol% or more and 5.5 mol% or less, 2.4 mol% or more and 5.0 mol% or less, 2.4 mol% or more and 4.5 mol% or less, or 2.5 mol% or more and 4.0 mol% or less.

[0026] The sintered body of this embodiment is CeO ２ The converted cerium content (hereinafter also simply referred to as "cerium content") is 1.5 mol% or more and 6.0 mol% or less. If the cerium content is less than 1.5 mol%, a reddish color cannot be obtained. On the other hand, if the cerium content exceeds 6.0 mol%, the sintered body will have a blackish color, making it impossible to obtain a bright red sintered body. The cerium content may be 1.5 mol% or more, 1.8 mol% or more, 2.0 mol% or more, or 2.2 mol% or more, and 6.0 mol% or less, 5.5 mol% or less, 5.0 mol% or less, 4.5 mol% or less, or 4.0 mol% or less. Preferred cerium contents include, for example, 1.5 mol% or more and 6.0 mol% or less, 1.8 mol% or more and 5.5 mol% or less, 2.0 mol% or more and 5.0 mol% or less, 2.0 mol% or more and 4.5 mol% or less, 2.0 mol% or more and 4.0 mol% or less, or 2.2 mol% or more and 4.0 mol% or less.

[0027] The cerium contained in the sintered body of this embodiment is at least trivalent cerium (Ce３＋ ). By including trivalent cerium, the sintered body exhibits a red color. The more trivalent cerium there is, the more likely the zirconia sintered body will have a reddish color tone. Therefore, the sintered body of this embodiment preferably contains a large amount of trivalent cerium, and the molar ratio of trivalent cerium to the cerium contained in the sintered body is preferably 50 mol% or more, 60 mol% or more, 70 mol% or more, or 80 mol% or more, and 100 mol% or less. Specific molar ratios of trivalent cerium include 50 mol% or more and 100 mol% or less, 60 mol% or more and 100 mol% or less, 70 mol% or more and 100 mol% or less, or 80 mol% or more and 100 mol% or less.

[0028] In this embodiment, the molar ratio of trivalent cerium to cerium can be determined from the X-ray absorption near edge fine structure spectrum (hereinafter also referred to as "XANES spectrum") at the Ce-L3 absorption edge. ３＋ ) and tetravalent cerium (Ce ４＋ ) The XANES spectrum of each standard sample is measured, and pattern fitting is performed between this and the XANES spectrum of the measurement sample to calculate the molar ratio of trivalent cerium to the cerium contained in the sintered body. ３ and tetravalent cerium is CeO ２ The XANES spectrum can be measured by performing background processing on an X-ray absorption fine structure spectrum (hereinafter also referred to as "XAFS spectrum") measured at a general synchrotron radiation facility such as SPring-8 using an analysis program (for example, product name: Demeter, manufactured by Bruce Ravel). Pattern fitting can be performed using the above-mentioned analysis program.

[0029] The sintered body of this embodiment is Al ２ O ３The converted aluminum content (hereinafter simply referred to as "aluminum content") is 0.05 mol% or more and 4.0 mol% or less. If the aluminum content is less than 0.05 mol%, the sintered body will have a strong orange color tone. On the other hand, if the aluminum content exceeds 4.0 mol%, the particles of the aluminum compound precipitated in the sintered body will excessively reflect incident light, resulting in an orange color tone of the sintered body. The aluminum content may be 0.05 mol% or more, more than 0.05 mol%, 0.08 mol% or more, or 0.1 mol% or more, and may be 4.0 mol% or less, 3.5 mol% or less, or 3.0 mol% or less. Preferred aluminum contents include, for example, 0.05 mol% or more and 4.0 mol% or less, more than 0.05 mol% and 4.0 mol% or less, 0.08 mol% or more and 3.5 mol% or less, or 0.1 mol% or more and 3.0 mol% or less.

[0030] The color-tuning element contained in the sintered body of this embodiment is at least one element selected from the group consisting of rare earth elements other than yttrium and cerium, and alkaline earth metal elements, and tetravalent zirconium (Zr ４＋ The ratio of the ionic radius of the color-tuning element to the ionic radius of the color-tuning element (hereinafter also referred to as "ionic radius ratio") is more than 1.0 and 1.6 or less. Specific examples of the color-tuning element include one or more selected from the group consisting of calcium (Ca), magnesium (Mg), strontium (Sr), scandium (Sc), lutetium (Lu), ytterbium (Yb), thulium (Tm), erbium (Er), holmium (Ho), dysprosium (Dy), terbium (Tb), gadolinium (Gd), europium (Eu), samarium (Sm), neodymium (Nd), praseodymium (Pr), and lanthanum (La). , magnesium, erbium, holmium, dysprosium, terbium, gadolinium, europium, samarium, neodymium, praseodymium, and lanthanum are preferred, one or more selected from the group consisting of calcium, magnesium, erbium, gadolinium, europium, neodymium, and lanthanum are more preferred, at least one of neodymium and lanthanum is even more preferred, lanthanum is even more preferred.

[0031] If an element having an ionic radius ratio of 1.0 or less is contained, the color tone of the resulting sintered body will be dark red or brown, and will not exhibit a vivid red color. On the other hand, an element having an ionic radius ratio of more than 1.6 is difficult to dissolve in zirconia, and will not exhibit a vivid red color in daylight. One of the reasons why the inclusion of an element having such a specific ionic radius ratio allows the sintered body to exhibit a vivid red color in daylight is the Ce dissolved in zirconia. ３＋ It is thought that the electronic structure of the color-tuning element changes. The color-tuning element preferably has an ionic radius ratio of more than 1.0, 1.04 or more, 1.1 or more, 1.2 or more, or more than 1.33, and 1.60 or less, 1.50 or less, 1.40 or less, or 1.38 or less. Examples of the ionic radius ratio include more than 1.00 and 1.60 or less, 1.04 or more and 1.50 or less, 1.10 or more and 1.40 or less, 1.20 or more and 1.38 or less, more than 1.33 and 1.40 or less, or more than 1.33 and 1.38 or less. ＊ / b ＊ and R ７００ / R ６００ Therefore, the ionic radius ratio of the color-tuning element is preferably more than 1.33 and not more than 1.40, and more preferably more than 1.33 and not more than 1.38.

[0032] The ionic radius ratio in this embodiment can be calculated by the following formula using the ionic radius reported by Shannon (Acta. Crystallogr., A32, 751-67 (1976)) rounded to two decimal places.

[0033] [Ionic radius ratio] = [Ionic radius of element] / [tetravalent zirconium (Zr ４＋ The ionic radius of the element is the ionic radius of an octacoordinated element, and the valence of the rare earth element corresponds to a trivalent value, and the valence of the Group 2 element corresponds to a divalent value. The ionic radius of a specific element is 1.12 Å (Ca ２＋ ), 0.89 Å (Mg ２＋ ), 1.26 Å (Sr ２＋ ), 0.87 Å (Sc ３＋ ), 0.98 Å (Lu ３＋ ), 0.99 Å (Yb ３＋ ), 0.99 Å (Tm ３＋ ), 1.00 Å (Er ３＋), 1.02 Å (Ho ３＋ ), 1.03 Å (Dy ３＋ ), 1.04 Å (Tb ３＋ ), 1.05 Å (Gd ３＋ ), 1.07 Å (Eu ３＋ ), 1.08 Å (Sm ３＋ ), 1.11 Å (Nd ３＋ ), 1.13 Å (Pr ３＋ ), 1.16 Å (La ３＋ ), and 0.84 Å (Zr ４＋ ) are listed.

[0034] The ionic radius ratio is 1.33 for calcium (Ca ２＋ / Zr ４＋ ), magnesium is 1.06 (Mg ２＋ / Zr ４＋ ), strontium is 1.50 (Sr ２＋ / Zr ４＋ ), scandium is 1.04 (Sc ３＋ / Zr ４＋ ), lutetium is 1.17 (Lu ３＋ / Zr ４＋ ), ytterbium is 1.18 (Yb ３＋ / Zr ４＋ ), thulium is 1.18 (Tm ３＋ / Zr ４＋ ), erbium is 1.19 (Er ３＋ / Zr ４＋ ), holmium is 1.21 (Ho ３＋ / Zr ４＋ ), dysprosium is 1.23 (Dy ３＋ / Zr ４＋ ), terbium is 1.24 (Tb ３＋ / Zr ４＋ ), gadolinium is 1.25 (Gd ３＋ / Zr ４＋ ), europium is 1.27 (Eu ３＋ / Zr ４＋ ), samarium is 1.29 (Sm ３＋ / Zr ４＋ ), neodymium is 1.32 (Nd ３＋ / Zr ４＋ ), praseodymium is 1.35 (Pr ３＋ / Zr ４＋), and lanthanum is 1.38 (La ３＋ / Zr ４＋ )

[0035] The sintered body of this embodiment has a content of the color-tuning element, calculated as an oxide (hereinafter simply referred to as "color-tuning element content"), of more than 0 mol% and not more than 4.0 mol%. If the color-tuning element content is 0 mol%, i.e., if no color-tuning element is contained, the sintered body will have a strong orange hue, and if the color-tuning element content exceeds 4.0 mol%, the strength of the sintered body will be reduced, which is undesirable. If the color-tuning element content exceeds 4.0 mol%, the sintered body will have a strong orange hue and will not exhibit a vivid red color. This is thought to be due to the formation of a dispersed phase containing the color-tuning element in the sintered body.

[0036] The color-tuning element content of the sintered body of this embodiment is preferably greater than 0 mol%, 0.2 mol% or more, 0.3 mol% or more, 0.5 mol% or more, or 0.8 mol% or more, and 4.0 mol% or less, 3.0 mol% or less, 2.5 mol% or less, or 2.0 mol% or less. As a combination of these upper and lower limits, the color-tuning element content is preferably greater than 0 mol% and 4.0 mol% or less, 0.2 mol% or more and 3.0 mol% or less, 0.3 mol% or more and 2.5 mol% or less, 0.5 mol% or more and 2.5 mol% or less, or 0.5 mol% or more and 2.0 mol% or less. For example, in a sintered body containing cerium, aluminum, yttrium, and calcium (Ca) as a color-tuning element, the yttrium content [mol%] is preferably greater than 0 mol% and 4.0 mol% or less, 0.2 mol% or more and 3.0 mol% or less, 0.3 mol% or more and 2.5 mol% or less, 0.5 mol% or more and 2.0 mol% or less. ２ Converted zirconium and Y ２ O ３ Y relative to the total converted yttrium ２ O ３ is the molar ratio of yttrium [mol%] converted to {Y ２ O ３ [mol] / (ZrO ２ +Y ２ O ３ ) [mol]} × 100. The cerium content [mol %] in the sintered body is calculated by the following formula: ２ Converted zirconium, Y ２ O ３ Converted yttrium, CeO２ Cerium in terms of oxides, color-matching elements in terms of oxides, and Al ２ O ３ CeO relative to the total converted aluminum ２ is the molar ratio of cerium [mol%] converted to {CeO ２ [mol] / (ZrO ２ +Y ２ O ３ + CeO ２ + CaO + Al ２ O ３ ) [mol]} × 100. The aluminum content [mol %] in the sintered body is calculated by the following formula: ２ Converted zirconium, Y ２ O ３ Converted yttrium, CeO ２ Cerium in terms of oxides, color-matching elements in terms of oxides, and Al ２ O ３ Al relative to the total converted aluminum ２ O ３ is the molar ratio of aluminum [mol%] converted to {Al ２ O ３ [mol] / (ZrO ２ +Y ２ O ３ + CeO ２ + CaO + Al ２ O ３ ) [mol]} × 100. The color-tuning element content [mol %] in the sintered body is calculated by ２ Converted zirconium, Y ２ O ３ Converted yttrium, CeO ２ Cerium converted to CaO, calcium converted to CaO, and Al ２ O ３ The molar ratio [mol %] of calcium converted into CaO to the total of aluminum converted into ZrO ２ +Y ２ O ３ + CeO ２ + CaO + Al ２ O ３ ) [mol]} × 100.

[0037] When the color-tuning element contains magnesium, the sintered body contains a spinel compound of aluminum and magnesium (MgAl ２ O ４ , hereinafter also referred to simply as "spinel compound." When the sintered body contains magnesium, the color of the sintered body tends to approach orange. Therefore, it is preferable that the sintered body of this embodiment does not contain a spinel compound. In order to suppress the formation of a spinel compound, when the color-tuning element contains magnesium, the magnesium content is preferably low, and is preferably 2.5 mol % or less or 2.0 mol % or less.

[0038] In the sintered body of this embodiment, the toning element is preferably dissolved in zirconia. The dissolution of the toning element in zirconia can be confirmed by a shift of the XRD peak corresponding to the cubic (400) plane to a lower angle. The XRD peak corresponding to the cubic (400) plane is a peak having a top at 2θ = 73.9 ± 0.9° in an XRD pattern measured using CuKα radiation as a radiation source.

[0039] A preferred range of the peak top of the XRD peak corresponding to the cubic (400) plane of the sintered body of this embodiment is 2θ = 73.0° or more and 73.9° or less, further 2θ = 73.1° or more and 73.8° or less, or even 2θ = 73.1° or more and 73.7° or less, in an XRD pattern measured using CuKα radiation as a radiation source.

[0040] The sintered body of this embodiment preferably does not contain impurities. ２ ) and other unavoidable impurities, as long as the effects of the present embodiment are not impaired. In the present embodiment, when calculating values ​​derived from the composition, such as density, hafnia may be regarded as zirconia.

[0041] In addition, the sintered body of this embodiment preferably does not contain a spinel compound. ２ O ４The presence of a spinel compound can be evaluated by the ratio of the peak height of an XRD peak having a peak top at 2θ=37.0±0.3 to the peak height of an XRD peak having a peak top at 2θ=30.0±0.3 in an XRD pattern (hereinafter also referred to as the "spinel ratio"). In this embodiment, a spinel ratio of 0.005 or less, or even 0.004 or less, can be used to determine that a spinel compound is not contained.

[0042] The XRD pattern can be measured using a general X-ray diffraction device (device name: Ultima IV, manufactured by RIGAKU Corporation). The measurement conditions include the following:

[0043] Radiation source: CuKα radiation (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 2° / min Measurement range: 2θ = 26° to 76° Acceleration voltage / current: 40 mA / 40 kV Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm After measurement under the above measurement conditions, analysis can be performed using the analysis program attached to the X-ray diffractometer (program name: Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation). The following conditions can be used as analysis conditions.

[0044] Peak shape: split pseudo-Voigt function Background processing: straight line connecting end points In the sintered body of this embodiment, it is preferable that the zirconia contains tetragonal and cubic crystals in its crystal structure, and may be composed of tetragonal and cubic crystals, as well as monoclinic crystals.

[0045] The cubic phase ratio is a value determined from the XRD pattern of the surface of the sintered body by the following formula.

[0046] f ｃ = [I ｃ(400)] / [I ｔ (400) + I ｔ (004) + I ｃ (400)] In the above formula, f ｃ is the cubic phase fraction, I ｃ (400) is the area intensity of the cubic (400) plane, I ｔ (004) is the area intensity of the tetragonal (004) plane, and I ｔ (400) is the area intensity of the tetragonal (400) plane. The cubic crystal ratio of the sintered body of this embodiment can be, for example, 15% or more, 20% or more, 25% or more, or 30% or more, and 70% or less, 65% or less, or 60% or less. As a combination of these upper and lower limits, the cubic crystal ratio is preferably 15% or more and 70% or less, 20% or more and 65% or less, 25% or more and 60% or less, or 30% or more and 60% or less.

[0047] The XRD pattern and the area intensity of each crystal plane may be determined in the same manner as described above.

[0048] The XRD peaks corresponding to the respective crystal planes measured in the above-mentioned XRD measurement have peak tops at the following 2θ, and are considered to be peaks derived from the tetragonal (004) plane, the cubic (400) plane, and the tetragonal (400) plane, respectively, from the low-angle side to the high-angle side.

[0049] XRD peak corresponding to the tetragonal (004) plane: 2θ = 72.9 ± 0.4° XRD peak corresponding to the cubic (400) plane: 2θ = 73.9 ± 0.9° XRD peak corresponding to the tetragonal (400) plane: 2θ = 74.3 ± 0.4° The sintered body of this embodiment is a zirconia sintered body exhibiting a red color (hereinafter also referred to as a "red zirconia sintered body"), and exhibits a vivid red color, particularly under daylight. The vivid red color tone is L ＊ a ＊ b ＊ In the color system, hue b ＊ Hue a ＊ The ratio of (hereinafter referred to as "a ＊ / b ＊ ") is 2.0≦a ＊ / b ＊ The following points can be mentioned.

[0050] The sintered body of this embodiment is a ＊ / b ＊ is 2.0≦a ＊ / b ＊ By satisfying the above condition, the color tone exhibits a reddish tone in comparison with the yellowish tone. ＊ / b ＊ is preferably 2.0 or more, more preferably 2.1 or more, and is 4.0 or less, more preferably 3.5 or less.

[0051] The sintered body of this embodiment has a vivid red color tone, ＊ a ＊ b ＊ Lightness L in the color system ＊ is 40 or more and 60 or less, and hue a ＊ is 10≦a ＊ ≦30 and hue b ＊ is 3≦b ＊ A more preferable color tone is one having a lightness L ＊ is 45 or more and 55 or less, and hue a ＊ is 15≦a ＊ ≦30 and hue b ＊ is 3≦b ＊ ≦10.

[0052] In this embodiment, the color tone can be measured by a method conforming to the method of JIS Z8722, and can be measured under the following conditions using a general spectrophotometer (for example, CM-700d, manufactured by Konica Minolta).

[0053] Light source: D65 light source Viewing angle: 10° Measurement method: SCI Background: Black Measurement sample: (Sample thickness) 2.4±0.1 mm (Measurement surface roughness) Ra≦0.02 μm Lightness L ＊ The larger the value, the brighter the color tone becomes, and vice versa. ＊ The smaller the hue a, the darker the color tone. ＊ indicates red to green tones, and a ＊ The larger the value, the stronger the red tone, and the smaller the value, the stronger the green tone. ＊ The value indicates yellow to blue tones, and b ＊The higher the value, the stronger the yellow tone, ＊ The lower the value, the stronger the blue tone.

[0054] Since the vivid red coloring is likely to be strong, the reflectance of the sintered body of this embodiment to light with a wavelength of 700 nm (hereinafter referred to as "R ７００ ") is preferably 40% or more, 45% or more, or 50% or more, and 90% or less, 85% or less, or 80% or less. As a combination of these upper and lower limits, R ７００ is preferably 40% or more and 90% or less, 45% or more and 85% or less, or 50% or more and 80% or less. In addition, the orange hue is suppressed and a more vivid red color is easily exhibited, so that the reflectance of the sintered body of this embodiment to light with a wavelength of 600 nm (hereinafter, "R ６００ " is also referred to as ".) is preferably 30% or less, or 25% or less. The lower limit can be 10% or more, or 15% or more. As a combination of these upper and lower limit values, R ６００ is preferably 10% or more and 30% or less, 10% or more and 25% or less, or 15% or more and 25% or less.

[0055] Usually, R ７００ However, when the sintered body of this embodiment contains aluminum and a color-tuning element in the above-mentioned content, the wavelength of light absorbed by the sintered body changes. ７００ Despite the high ６００ As a result, the sintered body of this embodiment exhibits a more vivid red color under daylight. ６００ R against ７００ The ratio of (hereinafter referred to as "R ７００ / R ６００ ") is preferably 2.4 or more or 2.5 or more, and may be 3.5 or less or 3.3 or less. ７００ / R ６００ The combination of the upper and lower limits of " is preferably 2.4 or more and 3.5 or less, and more preferably 2.5 or more and 3.3 or less.

[0056] The reflectance may be determined from a diffuse reflectance spectrum measured under the following conditions using an apparatus comprising an ultraviolet-visible-near-infrared spectrophotometer (for example, V-650, manufactured by JASCO Corporation) equipped with an integrating sphere unit (for example, ILV-724, manufactured by JASCO Corporation), after baseline correction using a standard reflector.

[0057] Standard reflector: Spectrolan (registered trademark) Measurement wavelength range: 380-780 nm Measurement mode: %R Data acquisition interval: 0.5 nm UV / Vis bandwidth: 5.0 nm Response: Fast Scanning speed: 1000 nm / min Light source: WI Regular reflection light: Included Filter switching: Step The measured density of the sintered body of this embodiment is 5.8 g / cm ３ or more than 5.9 g / cm ３ The upper limit of the measured density of the sintered body of this embodiment is 6.3 g / cm ３ or less than 6.2 g / cm ３ The specific measured density of the sintered body of this embodiment is 5.8 g / cm ３ 6.3g / cm or more ３ or less than 5.9 g / cm ３ 6.2g / cm or more ３ The following is preferred:

[0058] In this embodiment, the measured density of the sintered body may be determined by a method conforming to JIS R 1634: 1998. That is, the measured density may be determined as the mass of the sintered body determined by mass measurement relative to the volume of the sintered body determined by Archimedes' method.

[0059] The shape of the sintered body of this embodiment may be, for example, at least one selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral. Furthermore, any shape may be used depending on the purpose, such as various uses.

[0060] The sintered body of this embodiment may have a three-point bending strength of 800 MPa or more or 900 MPa or more, and 1300 MPa or less, or 1200 MPa or less. Preferred three-point bending strengths include 800 MPa or more and 1300 MPa or less, or 900 MPa or more and 1200 MPa or less.

[0061] The three-point bending strength can be measured by a three-point bending test in accordance with JIS R 1601. The measurement is performed 10 times, and the average value is taken as the three-point bending strength. The measurement can be performed using a columnar sintered body sample having a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm.

[0062] The method for producing the sintered body of this embodiment is arbitrary. A preferred method for producing the sintered body of this embodiment includes a method for producing a sintered body containing a cerium source, an aluminum source, an yttrium-containing zirconia source, and a color-tuning element source, and ２ The content of cerium converted from Al is 1.5 mol% or more and 6.0 mol% or less. ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as an oxide is 2.0 mol % or more and 6.0 mol % or less, and the content of color-tuning elements calculated as an oxide is more than 0 mol % and 4.0 mol % or less, the color-tuning element source is a compound containing at least one element selected from the group consisting of a rare earth element other than yttrium and cerium and an alkaline earth metal element, and further, tetravalent zirconium (Zr ４＋ a molding step of molding a powder composition to obtain a molded body, wherein the ratio of the ionic radius of the color-tuning element to the ionic radius of the color-tuning element is greater than 1.0 and not greater than 1.6; a step of sintering the molded body under atmospheric pressure to obtain a primary sintered body; and a secondary sintering step of sintering the primary sintered body in a reducing atmosphere.

[0063] The powder composition can be obtained by mixing a cerium source, an aluminum source, an yttrium-containing zirconia source, and a color-tuning element source. The cerium source, the aluminum source, the yttrium-containing zirconia source, and the color-tuning element source may have a composition similar to that of the target sintered body, and each starting material may be contained in the form of powder.

[0064] The cerium source may be at least one selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, acetates, and nitrates containing cerium, and is preferably at least one selected from the group consisting of oxides, hydroxides, oxyhydroxides, and chlorides, more preferably at least one selected from the group consisting of oxides, hydroxides, and chlorides, and even more preferably an oxide.

[0065] The cerium source may be a powder, and its average particle size is preferably 3.0 μm or less, 2.0 μm or less, or 1.0 μm or less, or 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. Examples of the combination of the upper and lower limits of the average particle size of the cerium source include 0.01 μm or more and 3.0 μm or less, 0.05 μm or more and 2.0 μm or more, and 0.1 μm or more and 1.0 μm or less.

[0066] The purity of the cerium source is preferably 99.0% by mass or more, and more preferably 99.9% by mass or more.

[0067] The aluminum source is alumina (Al ２ O ３ The aluminum compound may be a powder of at least one of aluminum hydroxide, aluminum nitrate, and aluminum chloride, and is preferably alumina, and more preferably α-alumina.

[0068] The average particle size of the aluminum source is preferably 1.0 μm or less, 0.7 μm or less, or 0.5 μm or less, or 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more. Examples of the combination of the upper and lower limits of the average particle size of the aluminum source include 0.01 μm or more and 1.0 μm or less, 0.05 μm or more and 0.7 μm or more, and 0.1 μm or more and 0.5 μm or less.

[0069] The purity of the aluminum source is preferably 99.0% by mass or more, and more preferably 99.9% by mass or more.

[0070] The yttrium-containing zirconia source is preferably zirconia containing 2.0 mol % or more and less than 6.0 mol % of yttrium.

[0071] The BET specific surface area of ​​the yttrium-containing zirconia source is 5 m ２ / g or more 20m ２ / g or less, and even 5m ２ / g or more 17m ２ The crystalline phase of zirconia in the stabilizing element-containing zirconia source preferably contains at least tetragonal crystals in the crystalline structure of zirconia, and the proportion of tetragonal crystals in the crystalline structure is preferably 50% or more.

[0072] The purity of the yttrium-containing zirconia source is preferably 99.6% by mass or more, and more preferably 99.8% by mass.

[0073] The yttrium-containing zirconia source may contain at least one of an yttrium source and a zirconia source in addition to or instead of the yttrium-containing zirconia.

[0074] The yttrium source may be at least one selected from the group consisting of yttria, yttrium hydroxide, and yttrium chloride, preferably at least one of yttria and yttrium chloride, more preferably yttria.The zirconia source may be at least one of zirconia and zirconium hydroxide, preferably zirconia.

[0075] The color-changing element source may be one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, acetates, and nitrates containing the color-changing element, and is preferably one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, and chlorides, more preferably one or more selected from the group consisting of oxides, hydroxides, and chlorides, and even more preferably an oxide.

[0076] The purity of the color-tuning element source powder is preferably 98.0% by mass or more.

[0077] The color-tuning element contained in the color-tuning element source is preferably one or more selected from the group consisting of calcium, magnesium, erbium, holmium, dysprosium, terbium, gadolinium, europium, samarium, neodymium, praseodymium, and lanthanum, more preferably one or more selected from the group consisting of calcium, magnesium, erbium, gadolinium, europium, neodymium, and lanthanum, even more preferably at least one of neodymium and lanthanum, and even more preferably lanthanum.

[0078] The powder composition preferably contains the above-mentioned starting materials in a homogeneous state.

[0079] The method for producing the powder composition is arbitrary as long as the starting materials are homogenized. However, a preferred method for producing the powder composition includes a mixing step by one or more methods selected from the group consisting of wet mixing, ball mill mixing, and stirring mill mixing, and preferably a mixing step by ball mill mixing.

[0080] The ball mill mixing is preferably a method of mixing a powder composition with either water or alcohol to form a slurry, which is then pulverized and mixed.

[0081] Any method may be used to dry the slurry, but one or more methods selected from the group consisting of static drying, spray drying using a two-fluid nozzle, and spray drying using an atomizer system are preferred.

[0082] After the mixing step, a granulation step of granulating the obtained powder composition may be carried out. The granulation of the powder composition may be carried out by any method that results in the powder being in a slowly agglomerated state, such as spray granulation.

[0083] In the compacting step, the powder composition is compacted to obtain a compact.

[0084] The molding method in the molding step may be any method capable of molding the powder composition into a desired shape. Examples of molding methods include one or more methods selected from the group consisting of uniaxial pressing, cold isostatic pressing, slip casting, and injection molding, and at least one of uniaxial pressing and cold isostatic pressing. The molded product may have any shape that takes into consideration the desired shape of the sintered product and thermal shrinkage due to sintering. Examples of the shape of the molded product include one or more shapes selected from the group consisting of disk-like, columnar, plate-like, spherical, and approximately spherical.

[0085] In the primary sintering step, the compact obtained in the compacting step is sintered under atmospheric pressure to obtain a primary sintered body.

[0086] The sintering temperature is preferably 1400°C or higher and 1600°C or lower, and more preferably 1500°C or higher and 1600°C or lower.

[0087] The firing atmosphere is an oxidizing atmosphere, preferably an air atmosphere.

[0088] The sintering time may be adjusted appropriately depending on the size of the compact to be subjected to the primary sintering step and the characteristics of the sintering furnace, and may be, for example, from 2 hours to 6 hours, or even from 2 hours to 4 hours. In the secondary sintering step, the primary sintered body obtained in the primary sintering step is sintered in a reducing atmosphere.

[0089] The sintering temperature is preferably 1300°C or higher and 1500°C or lower, and more preferably 1400°C or higher and 1500°C or lower.

[0090] The reducing atmosphere may be, for example, a mixed atmosphere of a reducing gas and an inert gas. The volume ratio of the reducing gas to the inert gas in the reducing atmosphere is preferably 3% or more and 10% or less, more preferably 5% or more and 10% or less.

[0091] The reducing gas is preferably at least one of hydrogen and carbon monoxide, more preferably hydrogen. The inert gas is preferably at least one of nitrogen and argon, more preferably argon. The reducing atmosphere is preferably a mixed atmosphere of hydrogen and argon.

[0092] The sintering time may be adjusted appropriately depending on the size of the primary sintered body to be subjected to the secondary sintering step and the characteristics of the sintering furnace, and may be, for example, from 1 hour to 6 hours, or from 1 hour to 4 hours.

[0093] The secondary sintering step can be performed by a known method, such as one or more methods selected from the group consisting of pressure sintering, vacuum sintering, and atmospheric sintering. Atmospheric sintering is preferred for the secondary sintering because it is simple and easy to apply industrially. Furthermore, the secondary sintering step preferably does not involve any sintering other than atmospheric sintering, and preferably does not include a pressure sintering step.

[0094] The manufacturing method of this embodiment may include at least one of a polishing step of polishing the sintered body and a processing step of processing the shape. The polishing step polishes the surface of the sintered body after sintering. By polishing, it is possible to give the surface a glossy finish, or to make the sintered body have a surface condition suitable for the intended use. The processing step processes the sintered body into any shape. This allows the sintered body to be shaped according to the use. Either the polishing step or the processing step may be performed first.

[0095] The present disclosure will be specifically described below using examples. However, the present disclosure is not limited to these examples. (Measurement of Measured Density) The measured density of the sintered body was determined by the method described in JIS R 1634:1998. That is, the mass of the sintered body determined by mass measurement relative to the volume of the sintered body determined by Archimedes' method was calculated as the measured density of the sintered body. (Measurement of Color Tone) The color tone of the sintered body sample was measured by a method conforming to JIS Z8722. For the measurement, a general spectrophotometer (device name: CM-700d, manufactured by Konica Minolta Japan Inc.) was used. The measurement conditions were as follows, and the color tone was measured using the SCI method, which measures specular reflected light in addition to diffuse reflected light.

[0096] Light source: D65 light source; Viewing angle: 10°; Measurement method: SCI; Background: Black background; Measurement sample: (Sample thickness) 2.4±0.1 mm; (Measured surface roughness) Ra≦0.02 μm. The sintered body sample was mirror-polished on one side to a thickness of 2.4±0.1 mm and a measured surface roughness of Ra≦0.02 μm, and measurements were performed on the surface. (Reflectance measurement) Reflectance was measured using an ultraviolet-visible-near-infrared spectrophotometer (instrument name: V-670, manufactured by JASCO Corporation) and a dedicated integrating sphere unit, irradiating the sample with light generated from a light source (deuterium lamp and halogen lamp). The sintered body sample was mirror-polished on one side to a thickness of 2.4±0.1 mm and a measured surface roughness of Ra≦0.02 μm, and measurements were performed on the surface. The measurement conditions were as follows:

[0097] Integrating sphere unit: ILV-724 (150 mmφ) Photometry mode: %R Measurement range: 380 nm to 780 nm Data acquisition interval: 0.5 nm Band width: 5.0 nm Response: Fast Scanning speed: 1000 nm / min Light source: Automatic Light source switching wavelength: 340.0 nm Filter switching: Step Baseline correction: Baseline (Measurement of crystalline phase) The crystalline phase was identified by XRD measurement under the following conditions using an X-ray diffractometer (device name: Ultima IV, manufactured by RIGAKU Corporation).

[0098] Radiation source: CuKα ray (λ = 0.15418 nm) Measurement mode: Continuous scan Scan speed: 2 ° / min Measurement range: 2θ = 26 ° to 76 ° Acceleration voltage / current: 40 mA / 40 kV Divergence vertical limiting slit: 10 mm Divergence / entrance slit: 1 ° Receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185 mm The crystalline phase was identified using the analysis program attached to the X-ray diffractometer (program name: Integrated Powder X-ray Analysis Software PDXL Ver. 2.2, manufactured by RIGAKU Corporation) by smoothing and background removal processing, and the XRD pattern after the processing was subjected to profile fitting using a split pseudo-Voigt function. The cubic crystal fraction was calculated from the XRD pattern of the sintered body surface using the above formula. The sintered body samples used were 2.4±0.1 mm thick and mirror-polished on one side so that the measured surface roughness Ra≦0.02 μm. (Three-point bending strength) The three-point bending strength was measured by a three-point bending test in accordance with JIS R 1601. The measurement was performed 10 times, and the average value was taken as the three-point bending strength. The measurement was performed using a columnar sintered body sample with a width of 4 mm and a thickness of 3 mm, with a support distance of 30 mm.

[0099] Example 1: 47.26 g of 3.0 mol% yttrium-containing zirconia (TZ-3YS, manufactured by Tosoh Corporation), 2.50 g of cerium oxide (purity: 99.9%, average particle size: 0.8 μm), 0.12 g of calcium oxide (purity: 98% or more), and 0.12 g of aluminum oxide powder (purity: 99.9% or more, average particle size: 0.3 μm, approximately spherical) were mixed with pure water to obtain a mixed powder having the following composition. The mixing was carried out by wet mixing in a ball mill using 10 mm diameter zirconia balls as the milling medium for 24 hours. After mixing, the mixture was dried in an air atmosphere at 110±15°C for 18 hours to obtain a raw material powder having the following molar composition.

[0100] CeO ２: 3.7mol% CaO : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : Remaining (95.5 mol%) (Primary Sintering) The raw material powder was filled into a cylindrical mold and uniaxially pressed at 98 MPa to obtain a cylindrical compact with a diameter of 25 mm and a thickness of 3.6 mm. The obtained compact was sintered in a muffle furnace at a heating rate of 100°C / hour in an air atmosphere at 1550°C for 2 hours, followed by cooling to room temperature at a heating rate of 200°C / hour to obtain a primary sintered body. The obtained primary sintered body exhibited a yellow color due to tetravalent cerium. (Secondary Sintering) The primary sintered body was placed in a tubular furnace equipped with an alumina core tube with an inner diameter of 50 mm, an outer diameter of 60 mm, and a total length of 100 mm. It was then sintered at 1450°C for 1 hour in a reducing atmosphere at a heating rate of 500°C / hour to obtain a sintered body, which was used as the sintered body of this example. The reducing atmosphere was a hydrogen / argon flow atmosphere (flow rate: 1 L / min) using hydrogen (5%) and argon (95%) gas. The sintered body of this example was red in color and contained tetragonal and cubic crystals in its crystal structure.

[0101] Example 2 A sintered body of this example was obtained in the same manner as in Example 1, except that magnesium oxide (purity: 98% or more) was used instead of calcium oxide to obtain a mixed powder having the following molar composition. The sintered body of this example had a spinel ratio of 0.

[0102] CeO ２ : 3.7 mol% MgO : 0.5 mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : Rest (95.5 mol %) Example 3 A sintered body of this example was obtained in the same manner as in Example 1, except that strontium oxide (purity: 99.9% or more) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0103] CeO ２ : 3.7 mol% SrO : 0.5 mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol %) Example 4 A sintered body of this example was obtained in the same manner as in Example 1, except that scandium oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0104] CeO ２ : 3.7mol% Sc ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol %) Example 5 A sintered body of this example was obtained in the same manner as in Example 1, except that lutetium oxide (purity 99.5%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0105] CeO ２ : 3.7mol% Lu ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol %) Example 6 A sintered body of this example was obtained in the same manner as in Example 1, except that erbium oxide (purity 99.99%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0106] CeO ２ : 3.7mol% Er ２ O ３ : 0.5mol% Al２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol %) Example 7 A sintered body of this example was obtained in the same manner as in Example 1, except that gadolinium oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0107] CeO ２ : 2.2mol% Gd ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (97.0 mol %) Example 8 A sintered body of this example was obtained in the same manner as in Example 1, except that neodymium oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0108] CeO ２ : 3.7mol% Nd ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol %) Example 9 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0109] CeO ２ : 3.7mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO２ : balance (95.5 mol %) Example 10 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0110] CeO ２ : 3.7mol% La ２ O ３ : 1.0mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ The sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition. The three-point bending strength of this example was 999 MPa.

[0111] CeO ２ : 3.8mol% La ２ O ３ : 1.0mol% Al ２ O ３ : 1.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (93.9 mol%) Example 12 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0112] CeO ２ : 3.9mol% La ２ O ３ : 2.0mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２: balance (93.8 mol %) Example 13 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0113] CeO ２ : 3.8mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.1mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.6 mol%) Example 14 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0114] CeO ２ : 3.7mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 1.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (94.5 mol %) Example 15 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0115] CeO ２ : 3.7mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 2.5mol% 3mol%Y ２ O ３ Contains ZrO ２: balance (93.3 mol%) Example 16 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0116] CeO ２ : 2.2mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : balance (97.0 mol %) Example 17 A sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0117] CeO ２ : 4.9mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ The balance (94.3 mol%) was the balance of Example 18. A hydrated zirconia sol was obtained by hydrolyzing an aqueous solution of zirconium oxychloride. Yttria (Y ２ O ３ ) was added to the hydrated zirconia sol, and then dried and calcined at 1160°C for 2 hours to obtain calcined zirconia powder containing yttria (specific surface area 5m ２ / g). The obtained calcined powder was washed with distilled water and then dried at 110°C to obtain a zirconia powder containing 2.5 mol% yttria. The sintered body of this example was obtained in the same manner as in Example 1, except that the 2.5 mol% yttria-containing zirconia powder and lanthanum oxide (purity 99.9%) were used instead of calcium oxide to obtain a mixed powder having the following molar composition.

[0118] CeO ２ : 3.7mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 2.5mol%Y ２ O ３ Contains ZrO ２ : balance (95.5 mol%) Example 19: 4.0 mol% yttria-containing zirconia (TZ-4YS, manufactured by Tosoh Corporation; specific surface area 7 m) ２ The sintered body of this example was obtained in the same manner as in Example 1, except that lanthanum oxide powder (purity 99.9%) was used instead of calcium oxide and that the mixed powder had the following molar composition: CeO ２ : 3.8mol% La ２ O ３ : 0.5mol% Al ２ O ３ : 0.3mol% 4mol%Y ２ O ３ Contains ZrO ２ : Rest (95.4 mol %) Comparative Example 1 A sintered body of this comparative example was obtained in the same manner as in Example 1, except that aluminum oxide was not used, lanthanum oxide (purity 99.9%) was used instead of calcium oxide, and the mixed powder had the following molar composition.

[0119] CeO ２ : 3.8mol% La ２ O ３ : 0.5mol% (Al ２ O ３ : 0.0mol%) 3mol%Y ２ O ３ Contains ZrO ２ : balance (95.7 mol%) Comparative Example 2: No calcium oxide was used, and zirconia powder containing 4.0 mol% yttria (TZ-4YS, manufactured by Tosoh Corporation; specific surface area 7 m) was used. ２The sintered body of this comparative example was obtained in the same manner as in Example 1, except that a sintered body of this comparative example was obtained using a powder of 10000 kJ / g, purity of 99.8% or more, and that the mixed powder had the following molar composition:

[0120] CeO ２ : 3.8mol% Al ２ O ３ : 0.3mol% 4mol%Y ２ O ３ Contains ZrO ２ : balance (95.9 mol %) Comparative Example 3 A sintered body of this comparative example was obtained in the same manner as in Example 1, except that niobium oxide (purity 99.9%) was used instead of calcium oxide and the mixed powder had the following molar composition.

[0121] CeO ２ : 2.2mol% Nb ２ O ５ : 0.5mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : Rest (97.0 mol%). Note that Nb in the mixed powder and sintered body ２ O ５ The content of Nb was calculated by the following formula based on the method for measuring the content of color-matching elements. ２ O ５ Content [mol%] = {(Nb ２ O ５ ) / (ZrO ２ +Y ２ O ３ + CeO ２ +Al ２ O ３ +Nb ２ O ５ )} × 100 The ionic radius ratio of niobium (Nb) to Zr is 0.74 Å (Nb ５＋ ) and the ion radius ratio to Zr was calculated in the same manner as for the other color-matching elements, and was found to be 0.88 (Nb ５＋ / Zr ４＋Comparative Example 4 A sintered body of this comparative example was obtained in the same manner as in Example 1, except that lanthanum oxide (purity 99.9%) was used instead of calcium oxide to obtain a mixed powder having the following molar composition: CeO ２ : 3.7mol% La ２ O ３ : 4.1mol% Al ２ O ３ : 0.3mol% 3mol%Y ２ O ３ Contains ZrO ２ : Remainder (91.9mol%)

[0122]

[0123]

[0124]

[0125] In all of the sintered bodies of Examples 1 to 19, 2.0≦a ＊ / b ＊ and 2.4≦R ７００ / R ６００ It was confirmed that the color was a vivid red under daylight.

[0126] Also, Al ２ O ３ Compared with Comparative Examples 1 and 2 which do not contain a ＊ / b ＊ and R ７００ / R ６００ It was confirmed that the sintered body exhibited a bright red color under daylight while suppressing the orange color. ２ O ３ In contrast to Comparative Example 3, which contains but does not contain a toning element, the examples are ＊ / b ＊ and R ７００ / R ６００ The sintered body of Comparative Example 3 had a high value of 0.01, and it was confirmed that the sintered body exhibited a vivid red color under daylight while suppressing the orange color. ＊ / b ＊ and R ７００ / R ６００The value of a was lower than that of the sintered bodies of Examples 1 to 19. Comparative Example 4, in which the content of the toning element exceeded 4 mol%, ＊ / b ＊ and R ７００ / R ６００ The value was low, and a sintered body exhibiting a vivid red color was not obtained.

[0127] The zirconia sintered body of the present invention is a sintered body with excellent aesthetics and can be used for a variety of components such as scratch-resistant, high-quality jewelry and decorative components, for example, watch components, exterior components for portable electronic devices, etc. The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2023-138864, filed on August 29, 2023, are hereby incorporated by reference as part of the disclosure of the specification of the present disclosure.

Claims

1. Contains cerium, aluminum, yttrium, and color-matching elements, CeO ２ The content of cerium converted is 1.5 mol% or more and 6.0 mol% or less, Al ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as yttrium is 2.0 mol% or more and 6.0 mol% or less, and the content of color-tuning additive elements calculated as oxides is more than 0 mol% and 4.0 mol% or less, and the cerium is trivalent cerium (Ce ３＋ ), the color-tuning element is at least one element selected from the group consisting of rare earth elements other than yttrium and cerium, and alkaline earth metal elements, and tetravalent zirconium (Zr ４＋ ) wherein the ratio of the ionic radius of the color-tuning element to the ionic radius of zirconia is greater than 1.00 and is 1.60 or less.

2. The sintered body according to claim 1, wherein the zirconia has a crystal structure including tetragonal and cubic crystals.

3. The sintered body according to claim 1 or 2, wherein the color-tuning element is one or more selected from the group consisting of calcium, magnesium, erbium, holmium, dysprosium, terbium, gadolinium, europium, samarium, neodymium, praseodymium, and lanthanum.

4. The sintered body according to any one of claims 1 to 3, wherein the ratio of the ion radii of the color-tuning elements is greater than 1.33 and not greater than 1.

40.

5. L ＊ a ＊ b ＊ In the color system, hue b ＊ Hue a ＊ The ratio (a ＊ / b ＊ ) is 2.0≦(a ＊ / b ＊ The sintered body according to claim 1 .

6. Reflectance for light with a wavelength of 700 nm (R ７００ ) and the reflectance (R ６００ ) ratio (R ７００ / R ６００ ) is 2.4≦(R ７００ / R ６００ The sintered body according to claim 1 .

7. A sintered body according to any one of claims 1 to 6, in which the ratio of the height of the peak top at 2θ = 37.0 ± 0.3 to the height of the peak top at 2θ = 30.0 ± 0.3 in an XRD pattern is 0.005 or less.

8. A cerium source, an aluminum source, an yttrium-containing zirconia source, and a color-tuning element source are contained, and CeO ２ The content of cerium converted is 1.5 mol% or more and 6.0 mol% or less, Al ２ O ３ The aluminum content calculated is 0.05 mol% or more and 4.0 mol% or less, Y ２ O ３ The content of yttrium calculated as yttrium is 2.0 mol% or more and 6.0 mol% or less, and the content of the color-changing element calculated as an oxide is more than 0 mol% and 4.0 mol% or less, the color-changing element source is a compound containing at least one element selected from the group consisting of a rare earth element other than yttrium and cerium, and an alkaline earth metal element, and further, tetravalent zirconium (Zr ４＋ A powder composition having an ionic radius ratio of the color-changing element to the ionic radius of the color-changing element of the present invention, which is greater than 1.0 and less than 1.

6.

9. A method for producing a sintered body according to any one of claims 1 to 7, comprising the steps of: forming the zirconia powder composition according to claim 8 into a molded body; sintering the molded body under atmospheric pressure to obtain a primary sintered body; and sintering the primary sintered body in a reducing atmosphere, said method comprising the steps of:

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