Colored sintered body and method for manufacturing the same

Abstract

To provide at least one of: a sintered body that contains zirconia as a matrix, exhibits a vivid green color tone, and is resistant to fading; and a method for producing the same.SOLUTION: A sintered zirconia body comprises: a spinel compound that has a ratio of monoclinic zirconia after hydrothermal treatment at 140°C for 24 hours of less than 25% and further contains aluminum and a coloring element; and an aluminium oxide, wherein a stabilizing element and a lanthanoid element that has an ionic radius that exceeds atomic radiuses of the stabilizing element and the zirconium are dissolved.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a colored sintered body with zirconia as the matrix. [Background technology]

[0002] Sintered bodies with a zirconia matrix can exhibit any desired color by containing lanthanide rare earth elements or transition metal elements. The inclusion of coloring elements enhances the aesthetic appeal of the sintered body, in addition to the inherent high quality and mechanical strength of zirconia. Therefore, colored zirconia matrix sintered bodies are being applied not only to traditional optical, medical, and mechanical applications, but also to decorative and exterior components where aesthetics are important. With the recent expansion of applications, there is a growing demand for sintered bodies that exhibit stable aesthetics over long periods of use.

[0003] As a colored zirconia sintered body, a sintered body exhibiting a greenish hue is known (for example, Patent Documents 1 to 4). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 62-59571 [Patent Document 2] Japanese Patent Application Publication No. 01-157462 [Patent Document 3] Japanese Patent Publication No. 2011-20874 [Patent Document 4] Japanese Patent Publication No. 2017-165599 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The sintered bodies disclosed in Patent Documents 1 to 4 all exhibit a greenish hue, but accelerated degradation tests such as hydrothermal treatment result in significant changes in color, or so-called fading. As a result, their aesthetic appeal changes considerably during use.

[0006] The present disclosure aims to provide at least one of the following: a sintered body containing zirconia as a matrix, exhibiting a vivid green color, and being resistant to discoloration; and a method for manufacturing the same. [Means for solving the problem]

[0007] The inventors focused on and investigated the coloring elements and their solid solution state in a sintered zirconia body that exhibits a green color. As a result, they found that a sintered zirconia body containing a certain compound exhibits a vivid green color, and furthermore, the change in color tone during long-term use is suppressed compared to conventional green sintered bodies.

[0008] In other words, the present invention is as described in the claims, and the gist of this disclosure is as follows. [1] A sintered zirconia body having less than 25% monoclinic zirconia after hydrothermal treatment at 140°C for 24 hours, and containing a spinel compound containing aluminum and a coloring element, as well as aluminum oxide, and containing a stabilizing element and a lanthanide element having an ionic radius exceeding the atomic radius of the stabilizing element and zirconium in solid solution. [2] The sintered body of [1], wherein the stabilizing element is one or more selected from the group consisting of yttrium, cerium, magnesium, and calcium. [3] The sintered body according to [1] or [2] above, wherein the lanthanide element is one or more selected from the group consisting of praseodymium, neodymium, europium, terbium, holonium, and erbium. [4] The sintered body according to any one of [1] to [3] above, wherein the coloring element is one or more selected from the group consisting of manganese, nickel, cobalt, and iron. [5] The sintered body according to any one of the above [1] to [4], wherein the content of the aluminum oxide is 0.5% by mass or more and 25% by mass or less. [6] L * a * b * lightness L in the color system * , hue a * and hue b * is the sintered body according to any one of the above [1] to [5] that satisfies the following.

[0009] lightness L * : 50 or more and 90 or less hue a * : -20 ≦ a * ≦ 2, and hue b * : -20 ≦ b * ≦ 30 [7] The sintered body according to any one of the above [1] to [6], wherein a color difference ΔE before and after hydrothermal treatment at 140°C for 24 hours is 0 or more and 2.0 or less. [8] A member comprising the sintered body according to any one of the above [1] to [7]. [9] A method for producing the sintered body according to any one of the above [1] to [7], comprising: a molding step of molding a powder composition comprising a stabilizing element-containing zirconia source, containing 0.2% by mass or more and 5% by mass or less of a lanthanoid element source having an ionic radius exceeding the atomic radius of zirconium, 0.5% by mass or more and 25% by mass or less of an aluminum source, and 0.03% by mass or more and 8% by mass or less of a coloring element source; and a sintering step of sintering the molded body obtained in the molding step at 1380°C or higher and 1580°C or lower.

[10] A powder composition comprising a stabilizing element-containing zirconia source, containing 0.2% by mass or more and 5% by mass or less of a lanthanoid element source having an ionic radius exceeding the atomic radius of zirconium, 0.5% by mass or more and 25% by mass or less of an aluminum source, and 0.03% by mass or more and 8% by mass or less of a coloring element source. Effects of the Invention

[0010] This disclosure provides at least one of the following: a sintered body containing zirconia as a matrix, exhibiting a vivid green color, and being resistant to discoloration due to degradation; and a method for manufacturing the same. [Modes for carrying out the invention]

[0011] The sintered body of this disclosure will be described below with reference to an example of an embodiment. The terms used in this embodiment are as follows.

[0012] "Composition" refers to a substance having a certain composition, and examples include one or more selected from the group consisting of powder, granules, molded body, calcined body, and sintered body. "Zirconia composition" refers to a composition consisting essentially of zirconia, and more specifically, a composition using zirconia as a matrix (base material).

[0013] "Powder" refers to a composition that is an aggregate of powder particles and also possesses fluidity. "Zirconia powder" refers to powder that is essentially made of zirconia, and more specifically, powder that uses zirconia as a matrix (base material). Furthermore, "powder composition" refers to a composition composed of powders with different characteristics, and in particular, a composition containing powders with different compositions.

[0014] A "molded article" is a composition having a certain shape, composed of powder particles aggregated by physical force, and in particular, a composition that has not undergone heat treatment after the shape has been imparted (e.g., after molding). A "zirconia molded article" is a molded article that is essentially made of zirconia, and more specifically, a molded article that uses zirconia as a matrix (base material).

[0015] A "sintered body" is a composition having a certain shape composed of crystalline particles, and is a composition that has been heat-treated at a temperature above the sintering temperature. A "zirconia sintered body" is a sintered body that is essentially made of zirconia, and more specifically, a sintered body that uses zirconia as a matrix (base material).

[0016] A "stabilizing element" is an element that has the function of stabilizing the crystalline phase of zirconia by being dissolved in it.

[0017] The content of stabilizing elements in a composition (mol%) (hereinafter also referred to as "amount of stabilizing elements") is the molar ratio of stabilizing elements in oxide form to the total amount of zirconium in ZrO2 form and stabilizing elements in oxide form in the composition.

[0018] The "BET specific surface area" should be measured using the BET multi-point method (5 points) with nitrogen as the adsorbent gas, in accordance with JIS R 1626. The following conditions are examples of specific measurement conditions for the BET specific surface area.

[0019] Adsorption medium: N2 Adsorption temperature: -196℃ Pretreatment conditions: Degassing treatment at 250°C for at least 1 hour in an air atmosphere. The BET specific surface area can be measured using a common instrument (e.g., TriStar II 3202, manufactured by Shimadzu Corporation).

[0020] The sintered body of this embodiment is a sintered zirconia body in which the proportion of monoclinic zirconia after hydrothermal treatment at 140°C for 24 hours is less than 25%, and which contains a spinel compound containing aluminum and a coloring element, as well as aluminum oxide, and which is in solid solution with a stabilizing element and a lanthanide element having an ionic radius exceeding the atomic radius of the stabilizing element and zirconium.

[0021] The sintered body of this embodiment is a sintered body of zirconia (hereinafter also referred to as "colored stabilized zirconia") in which a stabilizing element and a lanthanide element having an ionic radius exceeding the atomic radius of the stabilizing element and zirconium are solid-solution, further a sintered body having colored stabilized zirconia as the matrix (parent phase, main phase), and further a colored stabilized zirconia sintered body.

[0022] The stabilizing element can be any element that has the function of stabilizing zirconia, particularly an element that has the function of stabilizing the crystalline phase of zirconia without coloring the zirconia, and can be one or more selected from the group consisting of yttrium (Y), magnesium (Mg), cerium (Ce), and calcium (Ca), with yttrium being more preferred.

[0023] The content of stabilizing elements in colored stabilized zirconia should be such that the crystalline phase of the zirconia is stabilized, but it is preferably 2 mol% or more, 2.5 mol% or more, or 2.9 mol% or more, and also preferably 15 mol% or less, 6 mol% or less, or 5.8 mol% or less. If the content of stabilizing elements is within this range, fracture of the sintered body will be less likely to occur during manufacturing or under hydrothermal conditions. The upper and lower limits of the content of stabilizing elements in colored stabilized zirconia may be any combination of those described above.

[0024] In the sintered body of this embodiment, the colored stabilized zirconia is solid-dissolved with a stabilizing element and a lanthanide element having an ionic radius exceeding that of the stabilizing element and zirconium (hereinafter also referred to as "solid-solution lanthanide element"). In a sintered body having a multiphase structure in which zirconia with solid-solution stabilizing elements, solid-solution lanthanide elements, and other phases coexist, it is believed that during the manufacturing process (sintering process), the solid-solution lanthanide elements preferentially solid-solve in the zirconia as the sintering progresses. As a result, it is believed that the incorporation of phases other than solid-solution lanthanide elements, such as coloring components, into the zirconia is suppressed, making it possible to produce a vivid green color.

[0025] The solid solution lanthanide element is preferably one or more selected from the group consisting of praseodymium (Pr), neodymium (Nd), eurobium (Eu), terbium (Tb), holonium (Ho), and erbium (Er), and more preferably one or more selected from the group consisting of praseodymium, neodymium, and terbium, and even more preferably terbium.

[0026] In this embodiment, the ionic radius of the 8-coordinate lanthanide element may be considered as the ionic radius of the solid solution lanthanide element.4+ ), neodymium is 1.11 Å (Nd 3+ ), europium is 1.07 Å (Eu 3+ ), terbium is 0.88 Å (Tb 4+ ), holonium is 1.02 Å (Ho 3+ ), and erbium is 1.00 Å (Er 3+ ) is one example.

[0027] In this embodiment, the atomic radius of zirconium is 0.84 Å (Zr 4+ ), yttrium is 1.01 Å (Y 3+ ), magnesium is 0.89 Å (Mg 2+ ), cerium is 0.97 Å (Ce 4+ ) and calcium is 1.12 Å (Ca 2+ ) is one example.

[0028] The sintered body of this embodiment comprises a spinel compound containing aluminum and a coloring element, as well as aluminum oxide.

[0029] Aluminum oxide is included in the sintered body as crystalline particles distinct from spinel compounds and color-stabilized zirconia. The inclusion of aluminum oxide stabilizes the color tone, particularly the whiteness, of the sintered body. The aluminum oxide is preferably alumina (Al2O3).

[0030] The aluminum oxide content is preferably 0.5% by mass or 1% by mass or more as a ratio of the mass of aluminum oxide to the mass of the sintered body, and preferably 25% by mass or less or 20% by mass or less. An aluminum oxide content of 25% by mass or less makes it easier to obtain a high-density sintered body at a relatively low firing temperature. This makes the spinel compound more stable and suppresses color changes caused by changes in the spinel compound. The upper and lower limits of the aluminum oxide content may be any combination described above.

[0031] Aluminum and a spinel compound containing a coloring element (hereinafter also referred to as "colored spinel compound") are included in the sintered body as crystalline particles distinct from aluminum oxide and color-stabilized zirconia. The presence of crystalline particles made of color-stabilized zirconia as a matrix, along with crystalline particles made of the colored spinel compound, makes it possible to exhibit a vivid green color.

[0032] The coloring element can be any coloring element that forms a spinel compound with aluminum, preferably an element having an ionic radius smaller than the atomic radius of zirconium, and more preferably an element having an ionic radius smaller than the atomic radius of zirconium and larger than the ionic radius of the aluminum atom. This allows the reaction between the coloring element and aluminum to proceed preferentially during the manufacturing process (sintering process) of the sintered body of this embodiment, and the spinel compound is formed more efficiently. In addition, solid solution of the coloring element into zirconia becomes less likely. This suppresses the color development caused by the mixing of the coloring element and the lanthanide element. The ionic radius of the aluminum atom may be the ionic radius in 6 coordination. The ionic radius of the aluminum atom is 0.54 Å (Al 3+ ) is one example.

[0033] Specific coloring elements include transition metal elements other than hafnium and zirconium, as well as 3d transition metal elements, and furthermore, one or more elements selected from the group consisting of manganese (Mn), iron (Fe), nickel (Ni), and cobalt (Co). The ionic radius of the coloring element should be the ionic radius in 6-coordinate. For example, the ionic radius of manganese is 0.65 Å(Mn). 3+ ), nickel is 0.69 Å (Ni 2+ ), cobalt is 0.61 Å (Co 3+ ), and iron is 0.65 Å (Fe 3+ ) is one example.

[0034] In order to promote the formation of spinel compounds during the sintering process, the content of the coloring element in the sintered body of this embodiment is preferably 0.03% by mass or more, or 0.1% by mass or more, and the upper and lower limits of the coloring element content, which are preferably 8% by mass or less, or 5% by mass or less, may be any combination of those described above.

[0035] The sintered body of this embodiment has a structure in which colored stabilized zirconia crystal particles form a matrix and also contain colored spinel compound crystal particles, making it less susceptible to discoloration due to degradation.

[0036] The sintered body of this embodiment may contain impurities, provided that they do not affect its color. Examples of impurities include hafnia (HfO2), which is an unavoidable impurity in zirconia. The hafnia content in the sintered body varies depending on the origin of the zirconia raw material. In this embodiment, hafnia can be treated as zirconia when calculating values ​​based on composition, such as density.

[0037] The measured density of the sintered body in this embodiment is 5.45 g / cm³. 3 or more, or 5.50 g / cm³ 3 The above points are cited. This corresponds to a relative density of 95% or more. As a result, the pores on the surface of the sintered body become smaller, and even if there are pores on the surface, the impact on the visible color tone is reduced. In addition, the measured density of this embodiment is 6.10 g / cm³. 3 The following or 6.08 g / cm³ 3 The following can be cited: The sintered body of this embodiment has a high theoretical density, which is 95% or more or 97% or more, and 100% or less or 99.9% or less. The upper and lower limits of the measured density and relative density may be any combination described above.

[0038] The measured density is the ratio of the sintered body mass [g] obtained by mass measurement to the volume measured according to the method in accordance with JIS R1634 [g / cm³]. 3 ]

[0039] In this embodiment, the relative density can be determined as the ratio (%) of the measured density to the theoretical density.

[0040] In this embodiment, the colored zirconia sintered body has a monoclinic zirconia content of less than 25% after hydrothermal treatment at 140°C for 24 hours. If the monoclinic zirconia content after hydrothermal treatment at 140°C for 24 hours is 25% or more, the aesthetic quality tends to change significantly over time.

[0041] In this embodiment, the proportion of monoclinic zirconia is the proportion of monoclinic zirconia in the crystalline phase of zirconia (hereinafter also referred to as the "monoclinic ratio").

[0042] The monoclinic fraction can be determined using the following formula, based on the X-ray diffraction (hereinafter also referred to as "XRD") pattern of the surface of the sintered body after mirror polishing.

[0043] Monoclinic fraction (%) = [I m (111)+I m (11-1)] × 100 / [I m (111)+I m (11-1)+I t (111) + I(111) c ] In the above formula, I is the area intensity of each reflection, and the subscripts m, t, and c represent monoclinic, tetragonal, and cubic crystal structures, respectively.

[0044] The following conditions can be listed as requirements for measuring XRD patterns.

[0045] Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ = 26° ~ 33° In the XRD pattern measurement described above, preferably, the XRD peaks corresponding to each crystal plane of zirconia are measured as peaks having a peak top at the following 2θ.

[0046] XRD peak corresponding to the (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° XRD peak corresponding to the (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° The XRD peaks corresponding to the (111) plane of tetragonal and cubic zirconia were measured overlappingly, and the 2θ of the peak top was 2θ = 30 ± 0.5°.

[0047] The area intensity of the XRD peaks on each crystal plane can be determined using SmartLab Studio II (Rigaku).

[0048] The crystal structure of the sintered body in this embodiment preferably includes tetragonal crystals. Including tetragonal crystals in the crystal structure makes it easier to reflect incident light, thus suppressing the transparency of the sintered body. Furthermore, the crystal structure of the sintered body in this embodiment is more preferably predominantly tetragonal, and may also be a mixed crystal of tetragonal and cubic crystals. The strength of the sintered body in this embodiment is further increased when the predominantly tetragonal crystal structure of the sintered body is obtained.

[0049] The proportion of tetragonal crystals in the crystalline structure of the sintered body is preferably 75% or more, and more preferably 90% or more, and may be 100% or less or less than 100%. The upper and lower limits of the proportion of tetragonal crystals may be any combination as described above.

[0050] The tetragonal ratio in this embodiment can be determined from the XRD pattern obtained in the same way as the monoclinic ratio using the following formula.

[0051] Tetragonal ratio (%) = I t (111) × 100 / [I m (111)+I m (11-1)+I t (111) + I(111) c ] In this embodiment, the average grain size of the zirconia crystal particles in the sintered body is preferably 2 μm or less or 1 μm or less, and preferably 0.05 μm or more or 0.1 μm or more. A grain size of 2 μm or less for the zirconia crystal particles tends to increase the strength of the sintered body. The upper and lower limits for the average grain size of the zirconia crystal particles may be any combination described above.

[0052] In this embodiment, the average grain size of zirconia can be determined by extracting 200 or more (250 ± 10) zirconia crystal particles observed in the scanning microscope (SEM) observation image of the sintered body of this embodiment, determining the crystal diameter of the extracted crystal particles using the intercept method, and taking the average value of these values.

[0053] The sintered body of this embodiment is a sintered body that contains aluminum oxide and a colored spinel compound in addition to colored stabilized zirconia, and is composed of crystalline particles of colored stabilized zirconia, crystalline particles of aluminum oxide, and crystalline particles of the colored spinel compound. By including aluminum oxide and the colored spinel compound as crystalline particles independent of the colored stabilized zirconia, the sintered body exhibits a vivid green color tone and is less susceptible to discoloration due to deterioration during sintering.

[0054] The sintered body of this embodiment is a zirconia sintered body exhibiting a vivid green color. As for the vivid green color, L * a * b * In a color system, lightness L * The value is between 50 and 90, and the hue a * -20≦a * ≤2 and hue b * One example is that -20 ≤ b* ≤ 30.

[0055] In this embodiment, the color tone can be measured by a method in accordance with JIS Z8722, and can be measured using a general spectrophotometer (e.g., CM-700d, manufactured by Konica Minolta) under the following conditions.

[0056] Light source: D65 light source Viewing angle: 10° Measurement method: SCI Background: Black background The sintered body of this embodiment has a color difference △E before and after hydrothermal treatment at 140°C for 24 hours, preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.0 or less. This makes it difficult to perceive a change in color tone even when exposed to harsh environments, and the change in color tone is not easily recognized by the naked eye. The color difference △E can be calculated using the following formula. A low △E is preferable, but examples include 0 or more or 0.1 or more. Furthermore, the upper and lower limits of the color difference △E may be any combination as described above.

[0057] △E={(L1 * -L2 * ) 2 +(a1 * -a2 * ) 2 +(b1 * -b2 * ) 2} 0.5 In the above formula, L1 * a1 * and b1 * , and L2 * a2 * and b2 * These represent the brightness L of the sintered body surface before and after hydrothermal treatment at 140°C for 24 hours. * , hue a * and b * That is the case.

[0058] The sintered body of this embodiment only needs to have the strength required for each application, such as an exterior component. For example, it may have a three-point bending strength of 800 MPa or more or 1000 MPa or more. Higher strength is preferable, but examples include 2000 MPa or less or 1800 MPa or less. The upper and lower limits of the three-point bending strength may be any combination described above.

[0059] The three-point bending strength in this embodiment can be measured by a method in accordance with JIS R 1601.

[0060] Next, the method for manufacturing the sintered body of this embodiment will be described.

[0061] The method for manufacturing the sintered body in this embodiment is arbitrary as long as a sintered body satisfying the above configuration can be obtained. A preferred manufacturing method is a method for manufacturing a sintered body which includes a molding step of molding a powder composition containing a stabilizing element-containing zirconia source, which contains 0.2% to 5% by mass of a lanthanide element source having an ionic radius greater than the atomic radius of zirconium, 0.5% to 25% by mass of an aluminum source, and 0.03% to 8% by mass of a coloring element source; and a sintering step of sintering the molded body obtained in the molding step at 1380°C to 1580°C.

[0062] The powder composition used in the molding process contains 0.2% to 5% by mass of a lanthanide element source having an ionic radius exceeding that of zirconium (hereinafter referred to as "solid solution lanthanide element source"), 0.5% to 25% by mass of an aluminum source, and 0.03% to 8% by mass of a coloring element source, and also contains a stabilizing element-containing zirconia source.

[0063] The raw materials included in the powder composition, such as solid-solution lanthanide element sources, may be of the same type and composition as the target sintered body, and may be included in powder form.

[0064] As a solid-solution lanthanide element source, any one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, acetates, and nitrates containing solid-solution lanthanide elements is acceptable. Preferably, it is one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, and chlorides. More preferably, it is one or more selected from the group consisting of oxides, hydroxides, and chlorides, and even more preferably, it is an oxide.

[0065] The solid-solution lanthanide elements contained in the solid-solution lanthanide element source include one or more selected from the group consisting of praseodymium, neodymium, eurobium, terbium, holonium, and erbium, and further, one or more selected from the group consisting of praseodymium, neodymium, and terbium, and further, terbium.

[0066] The aluminum source can be alumina (Al2O3) or an aluminum compound powder that is a precursor thereof, and can be at least one from the group consisting of alumina, aluminum hydroxide, aluminum nitrate, and aluminum chloride, with alumina being preferred and α-alumina being more preferred.

[0067] The BET specific surface area of ​​aluminum oxide powder is 5 m². 2 / g or more 20m 2 It is preferable that the value be less than or equal to / g.

[0068] As a coloring element source, one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, halides, sulfates, acetates, and nitrates containing a coloring element is acceptable. Preferably, one or more selected from the group consisting of oxides, hydroxides, oxyhydroxides, and chlorides is preferred, more preferably one or more selected from the group consisting of oxides, hydroxides, and chlorides is preferred, and even more preferably an oxide.

[0069] The coloring element contained in the elemental source may be any coloring element that forms a spinel compound with aluminum, preferably an element having an ionic radius smaller than the atomic radius of zirconium, more preferably an element having an ionic radius smaller than the atomic radius of zirconium and also larger than the ionic radius of an aluminum atom, even more preferably a transition metal element other than hafnium and zirconium, even more preferably a 3d transition metal element, and particularly preferably one or more selected from the group consisting of manganese, iron, nickel, and cobalt.

[0070] The zirconia source containing stabilizing elements is preferably zirconia containing 2 mol% or more and less than 15 mol% of yttrium.

[0071] The BET specific surface area of ​​zirconia powder containing stabilizing elements is 5 m². 2 / g or more 20m 2 It is preferable that the amount is less than or equal to / g. Furthermore, it is preferable that the crystalline phase of the zirconia in the zirconia powder containing stabilizing elements has a proportion of tetragonal zirconia of 50% or more relative to the crystalline phase of zirconia.

[0072] The zirconia source containing stabilizing elements may be a mixed powder containing zirconia containing stabilizing elements, or in place of zirconia containing stabilizing elements, as well as at least one of the stabilizing element source and the zirconia source.

[0073] Yttria is cited as a source of stabilizing elements.

[0074] The powder composition preferably contains each of the above-mentioned raw materials in a uniform state.

[0075] The molded body subjected to the sintering process may have any shape that takes into account the desired shape of the sintered body and the thermal shrinkage caused by sintering. Examples of molded body shapes include one or more selected from the group consisting of disc-shaped, columnar, plate-shaped, spherical, and substantially spherical shapes.

[0076] The molding method in the molding process can be any method that can mold the powder composition into a desired shape. Examples of molding methods include one or more selected from the group consisting of uniaxial press, cold isohydraulic press, slip casting, and injection molding, and at least one of uniaxial press and cold isohydraulic press.

[0077] In the sintering process, the molded body is sintered at a temperature between 1380°C and 1580°C. Solid-solution lanthanide elements are stably dissolved in the stabilizing element-containing zirconia, and aluminum oxide powder acts as a nucleus to which oxides of coloring elements with an ionic radius smaller than that of zirconium atoms react to form colored spinel compounds.

[0078] The sintering temperature is preferably between 1400°C and 1550°C.

[0079] The sintering method is arbitrary as long as the colored spinel compound can be obtained stably. For example, one or more methods can be selected from the group consisting of atmospheric pressure sintering, hot pressing, and hot isostatic pressing (hereinafter also referred to as "HIP"). Preferred sintering methods include atmospheric pressure sintering, and more specifically, atmospheric pressure sintering in an atmospheric environment. Atmospheric pressure sintering is a method in which the molded body is sintered simply by heating without applying any external force during sintering.

[0080] The sintering time can be set to any range depending on the sintering method and sintering temperature. For example, it can be between 1 hour and 5 hours, or between 2 hours and 4 hours.

[0081] In the sintering process, the sintered body after atmospheric pressure sintering may be subjected to HIP (Heat Isolation). Examples of HIP conditions after atmospheric pressure sintering include argon or nitrogen atmosphere, pressure of 50 MPa to 200 MPa, temperature of 1400°C to 1550°C, and duration of 30 minutes to 4 hours.

[0082] The manufacturing method of this embodiment may include at least one of a polishing step for polishing the sintered body and a processing step for shaping the body. The polishing step involves polishing the surface of the sintered body after sintering. Polishing can give the sintered body a glossy surface, making it suitable for the intended application. The processing step involves shaping the sintered body into an arbitrary shape. This allows the sintered body to be shaped according to its intended use. The polishing step and the processing step may be performed in either order. [Examples]

[0083] The embodiments will be described in detail below with reference to examples. However, the embodiments are not limited to these examples.

[0084] (Color measurement) The color tone of the sintered body sample was measured according to the method specified in JIS Z8722. A general spectrophotometer (device name: CM-700d, manufactured by Konica Minolta) was used for the measurement. The measurement conditions were as follows:

[0085] Light source: D65 light source Viewing angle: 10° Measurement method: SCI Background: Black background A sintered body sample in the shape of a disc with a diameter of 20 mm and a thickness of 2.7 mm was used. The surface of the sintered body sample was ground from both sides to a thickness of 1.0 mm, and then mirror-polished. This surface was used as the evaluation surface, and its color tone was evaluated. A diameter of 10 mm was used as the effective area for color tone evaluation. (Bending strength) The bending test was performed using a three-point bending test in accordance with JIS R 1601 "Test Method for Bending Strength of Fine Ceramics". Ten measurements were taken, and the average value was used 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.

[0086] (Sintered body density) The actual density of the sintered body was measured using a measurement method compliant with JIS R 1634 (Method for measuring the density and open porosity of sintered fine ceramics), and this was defined as the sintered body density.

[0087] (Average grain size) The average grain size of zirconia crystal grains in sintered body samples was measured using the intercept method. After mirror polishing, the sintered body samples were thermally etched, and their surfaces were observed at 20,000x magnification using a scanning microscope. The average particle size of zirconia crystal grains was measured from the resulting SEM image using the intercept method (k=1.78). The number of zirconia crystal grains measured was 200 or more.

[0088] (Hydrothermal treatment) Except for the hydrothermal treatment being performed at 140°C for 24 hours, the hydrothermal treatment of the sintered body was carried out in accordance with ISO 13356. The monoclinic fraction was determined by XRD measurement of the hydrothermal-treated sintered body and using the following formula. Monoclinic fraction (%) = [I m (111)+I m (11-1)] × 100 / [I m (111)+I m (11-1)+I t (111) + I(111) c ] However, in the above formula, I is the area intensity of the XRD peak corresponding to each crystal plane, and the subscripts m, t, and c indicate monoclinic, tetragonal, and cubic crystal structures, respectively.

[0089] XRD measurements were performed using a general-purpose X-ray diffractometer (product name: UltimaIIV, manufactured by Rigaku Corporation) to obtain the XRD patterns of the hydrothermally treated sintered body. The conditions for the XRD measurements were as follows:

[0090] Radiation source: CuKα radiation (λ=0.15418nm) Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ = 26° ~ 33° In the XRD pattern measurement described above, the XRD peaks corresponding to each crystal plane of zirconia were defined as peaks with peak tops at the following 2θ.

[0091] XRD peak corresponding to the (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° XRD peak corresponding to the (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° The RD peaks corresponding to the (111) plane of tetragonal and cubic zirconia were measured overlappingly, and the 2θ of the peak top was 2θ = 30 ± 0.5°.

[0092] The area intensity of the XRD peak for each crystal plane was determined on SmartLab Studio II (Rigaku).

[0093] Further, for the hydrothermally treated sintered body, the color tone was measured by the same method as described above, and based on the obtained color tones of the sintered body before and after hydrothermal treatment, the color difference ΔE before and after hydrothermal treatment was determined using the following formula.

[0094] Color difference ΔE = {(L1 * - L2 * ) 2 + (a1 * - a2 * ) 2 + (b1 * - b2 * ) 2} 0.5 However, in the above formula, L1 * , a1 * and b1 * are the values of the surface of the sintered body before hydrothermal treatment at 140°C for 24 hours, and L2 * , a2 * and b2 * are the lightness L, * hue a, * and b * on the surface of the sintered body after hydrothermal treatment at 140°C for 24 hours.

[0095] Example 1 3 mol% yttrium-containing zirconia powder (BET specific surface area: 6.8 m 2 / g, manufactured by Tosoh Corporation), high-purity alumina powder (BET specific surface area: 7.0 m 2 / g, manufactured by Sumitomo Chemical), nickel oxide (NiO) powder (manufactured by Wako Pure Chemical Industries), and terbium oxide (manufactured by Kojundo Chemical Laboratory) were mixed to obtain a mixed powder having the following composition. The mixing was performed by wet mixing using a ball mill. After mixing, the mixture was dried in air at 115±15°C to obtain a mixed powder.

[0096] Al2O3: 5.0% by mass NiO : 3.0% by mass Tb2O5: 0.2% by mass 3 mol% Y2O3-containing ZrO2: balance Mixed powder, unscrewed molding pressure 1000 kg / cm² 2 The material was compressed and molded to form a molded body, and this molded body was sintered to obtain the sintered body of this embodiment. Sintering was carried out using an electric furnace in air, with a heating rate of 100°C / hour, a sintering temperature of 1450°C, and a sintering time of 2 hours. This resulted in the solid solution of terbium oxide in yttrium-stabilized zirconia and the formation of a nickel-aluminum composite oxide having a spinel structure.

[0097] The obtained terbium and yttrium solid-solution zirconia (colored zirconia phase) was used as the matrix, and a sintered body containing nickel-aluminum composite oxide (colored spinel compound) was used as the sintered body of this example. The sintered body of this example had an aluminum content of 5.0 mass%, a nickel content of 3.0 mass%, and a terbium content of 0.14 mol% and an yttria content of 3.0 mol% in the zirconia.

[0098] Visual inspection of the polished surface of the obtained sintered body revealed a vivid green color, and the three-point bending strength was 1117 MPa.

[0099] Example 2 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1450°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0100] Al2O3: 5.0% by mass NiO: 0.2% by mass Tb2O5: 2.0% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this embodiment had an aluminum content of 5.0 mass%, a nickel content of 0.2 mass%, and a terbium content of 1.4 mol% and an yttria content of 3.0 mol% in zirconia.

[0101] Visual inspection of the polished surface of the obtained sintered body revealed a vivid green color, and the three-point bending strength was 1229 MPa.

[0102] Example 3 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1450°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0103] Al2O3: 5.0% by mass NiO: 3.0% by mass Tb2O5: 2.0% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this embodiment had an aluminum content of 5.0 mass%, a nickel content of 3.0 mass%, and a terbium content of 1.4 mol% and a yttrium content of 3.0 mol% in zirconia.

[0104] Visual inspection of the polished surface of the obtained sintered body revealed a vivid green color, and the three-point bending strength was 1003 MPa.

[0105] Example 4 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1450°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0106] Al2O3: 0.5% by mass NiO: 1.0% by mass Tb2O5: 1.0% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this example had an aluminum content of 0.5 mass%, a nickel content of 1.0 mass%, a terbium content of 0.7 mol% in zirconia, and an yttria content of 3.0 mol%.

[0107] Visual inspection of the polished surface of the obtained sintered body confirmed that it exhibited a vivid green color.

[0108] Example 5 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1450°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0109] Al2O3: 2.0% by mass NiO: 0.5% by mass Tb2O5: 1.5% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this example had an aluminum content of 2.0 mass%, a nickel content of 0.5 mass%, a terbium content of 1.0 mol% in zirconia, and an yttria content of 3.0 mol%.

[0110] Visual inspection of the polished surface of the obtained sintered body confirmed that it exhibited a vivid green color.

[0111] Example 6 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1450°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0112] Al2O3: 0.5% by mass NiO: 1.0% by mass Tb2O5: 2.0% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this example had an aluminum content of 0.5 mass%, a nickel content of 1.0 mass%, a terbium content of 1.4 mol% in zirconia, and an yttria content of 3.0 mol%.

[0113] Visual inspection of the polished surface of the obtained sintered body confirmed that it exhibited a vivid green color.

[0114] Example 7 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1500°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0115] Al2O3: 20% by mass NiO: 3.0% by mass Tb2O5: 2.5% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this example had an aluminum content of 20% by mass, a nickel content of 3.0% by mass, and a terbium content of 1.7 mol% and an yttria content of 3.0 mol% in the zirconia.

[0116] Visual inspection of the polished surface of the obtained sintered body confirmed that it exhibited a vivid green color.

[0117] Example 8 Except for obtaining a mixed powder having the following composition and setting the sintering temperature to 1500°C, a sintered body was obtained using the same method as in Example 1, with terbium and yttrium solid-solution zirconia (colored zirconia phase) as the matrix and containing nickel-aluminum composite oxide (colored spinel compound), and this was used as the sintered body of this example.

[0118] Al2O3: 20% by mass NiO: 2.0% by mass Tb2O5: 2.0% by mass ZrO2 containing 3mol%Y2O3: balance The sintered body of this example had an aluminum content of 20% by mass, a nickel content of 2.0% by mass, and a terbium content of 1.4 mol% and an yttria content of 3.0 mol% in zirconia.

[0119] Visual inspection of the polished surface of the obtained sintered body confirmed that it exhibited a vivid green color.

[0120] Comparative Example 1 3 mol% yttrium-containing zirconia powder (BET specific surface area: 6.8 m²) 2 A mixed powder with the following composition was obtained by mixing (1g, manufactured by Tosoh Corporation) and nickel oxide (NiO) powder (manufactured by Wako Pure Chemical Industries). Mixing was performed using a wet ball mill. After mixing, the mixture was dried in air at 115±15℃ to obtain the mixed powder.

[0121] NiO: 3.0% by mass ZrO2 containing 3mol%Y2O3: balance Mixed powder, unscrewed molding pressure 1000 kg / cm² 2 The material was compression-molded to form a molded body, and this molded body was sintered to obtain the sintered body of this embodiment. Sintering was carried out using an electric furnace in air, with a heating rate of 100°C / hour, a sintering temperature of 1500°C, and a sintering time of 2 hours. This yielded a sintered body of nickel and yttrium solid-solution zirconia, which was used as the sintered body of this comparative example.

[0122] The sintered body in this comparative example had a nickel content of 5.0% by mass and an yttria content of 3.0 mol%.

[0123] Visual inspection of the polished surface of the obtained sintered body revealed that it was green in appearance. However, after hydrothermal treatment, the monoclinic content of the sample was 69%, resulting in a deterioration of surface properties, and it was confirmed that the color tone had also changed from that before the deterioration.

[0124] The evaluation results of these examples and comparative examples are shown in Tables 1 and 2.

[0125] [Table 1] Table 1 confirms that the monoclinic content of the sintered body in this embodiment after hydrothermal treatment is 25% or less.

[0126] [Table 2] Table 2 shows that the sintered body of this embodiment exhibits a color difference △E of 1.0 or less before and after hydrothermal treatment, and no visible color change was observed. This confirms that the sintered body of this embodiment exhibits a vivid green color without compromising aesthetics even under harsh environments. [Industrial applicability]

[0127] The zirconia sintered body of this embodiment is a highly durable and aesthetically pleasing sintered body that maintains a stable color even when it deteriorates with use. It can be used in a variety of components, such as watch parts and exterior parts for portable electronic devices, for example, as a high-quality, scratch-resistant piece of jewelry and decorative material.

Claims

1. A sintered zirconia body having a monoclinic zirconia content of less than 25% after hydrothermal treatment at 140°C for 24 hours, and containing a spinel compound containing aluminum and a coloring element, as well as aluminum oxide, in which a stabilizing element and a lanthanide element having an ionic radius of 8 coordination exceeding the atomic radius of the stabilizing element and zirconium are solid-solution, wherein the stabilizing element is yttrium and the lanthanide element is terbium.

2. The sintered body according to claim 1, wherein the content of the coloring element is 0.03% by mass or more and 8% by mass or less.

3. The sintered body according to claim 1 or 2, wherein the three-point bending strength measured by a method in accordance with JIS R 1601 is 800 MPa or more and 2000 MPa or less.

4. The sintered body according to claim 1 or 2, wherein the coloring element is one or more selected from the group consisting of manganese, nickel, cobalt, and iron.

5. The sintered body according to claim 1 or 2, wherein the content of the aluminum oxide is 0.5% by mass or more and 25% by mass or less.

6. L ＊ a ＊ b ＊ Lightness L in a color system ＊ , hue a ＊ and hue b ＊ However, the sintered body according to claim 1 or 2 that satisfies the following: Brightness L ＊ 50 and below Hue a ＊ : -20≦a ＊ ≦2, and Hue b ＊ : -20≦b ＊ ≤30

7. A sintered body according to claim 1 or 2, wherein the difference in color tone ΔE before and after hydrothermal treatment at 140°C for 24 hours is 0 or more and 2.0 or less.

8. A member comprising the sintered body described in claim 1 or 2.

9. A method for producing a sintered body according to claim 1 or 2, comprising: a molding step of molding a powder composition containing a stabilizing element-containing zirconia source, which contains 0.2% to 5% by mass of a lanthanide element source having an ionic radius of 8 coordination exceeding the atomic radius of zirconium, 0.5% to 25% by mass of an aluminum source, and 0.03% to 8% by mass of a coloring element source; and a sintering step of sintering the molded body obtained in the molding step at 1380°C to 1580°C.

10. A powder composition comprising 0.2% to 5% by mass of a lanthanide element source having an ionic radius of 8 coordination exceeding the atomic radius of zirconium, 0.5% to 25% by mass of an aluminum source, and 0.03% to 8% by mass of a coloring element source, and further comprising a stabilizing element-containing zirconia source, wherein the stabilizing element is yttrium and the lanthanide element is terbium.

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