Sintered body

Abstract

Provided is a zirconia sintered body that has a high impact resistance even as a thin shape with a thickness of 0.5 mm or less, and has a high light-shielding property in which a member serving as a substrate does not show through. This zirconia sintered body includes a stabilizing element, niobium, manganese, and alumina, wherein the crystallite diameter calculated from an XRD peak that is attributed to the (111) plane of tetragonal zirconia is 25 nm to 100 nm.

Description

sintered body

[0001] The present disclosure relates to a sintered body, and more particularly to a sintered body that has impact resistance and light-shielding properties and is mainly made of zirconia.

[0002] Sintered bodies with a zirconia matrix (zirconia sintered bodies) are not only highly strong and tough, but also highly aesthetic. Therefore, their use in decorative applications, such as exterior components for watches and portable electronic devices, is being considered. In particular, when using zirconia sintered bodies in mobile devices and wearable devices, such as smartphones and smartwatches, they must be thin to reduce weight. Therefore, they require high strength and impact resistance that prevent cracking even in thin shapes.

[0003] As a thin, impact-resistant material, a composite material (laminate material) has been proposed in which a zirconia sintered body is laminated with a synthetic resin, a fiber-reinforced plastic, or the like. For example, Patent Document 1 reports a composite plate in which a zirconia matrix is ​​combined with a polymer material. The composite plate has a thickness of less than 1 mm, and when a 20 g steel ball is dropped onto the composite plate, the plate cracks and breaks to a height of 40 cm or more, demonstrating high impact resistance.

[0004] Japanese Patent Publication No. 2014-54780 Japanese Patent Publication No. 2020-180048

[0005] The composite plate of Patent Document 1 requires lamination of a zirconia-matrix ceramic member and a resin material, resulting in a complex manufacturing process. Therefore, a material that exhibits high impact resistance even in a thin shape made solely of a zirconia sintered body is needed. Furthermore, when a thin exterior component is fabricated solely from a zirconia sintered body, the translucency of zirconia allows the underlying component to be seen through the exterior component, impairing the design. Patent Document 2 discloses the inclusion of alumina or titania as a light-blocking material to adjust the translucency of dental zirconia sintered bodies. However, such zirconia sintered bodies show through the underlying component when formed into a shape with a thickness of 0.5 mm or less (thin shape). Furthermore, because alumina has low toughness, increasing the alumina content decreases the fracture toughness value of the zirconia sintered body, resulting in reduced impact resistance.

[0006] The present disclosure provides a zirconia sintered body that has high impact resistance even in a thin shape with a thickness of 0.5 mm or less, and has light-blocking properties that prevent the underlying material from showing through.

[0007] That is, the present invention is as defined in the claims, and the gist of the present disclosure is as follows. [1] A zirconia sintered body containing a stabilizing element, niobium, manganese, and alumina, wherein the crystallite size calculated from the XRD peak assigned to the (111) plane of tetragonal zirconia is 25 nm to 100 nm. [2] The zirconia sintered body according to [1], wherein the stabilizing element includes one or more selected from the group consisting of calcium, yttrium, lanthanum, neodymium, gadolinium, erbium, and ytterbium, and the content of the stabilizing element is 2.0 mol% to 5.5 mol%. [3] The zirconia sintered body according to [1] or [2], wherein the content of niobium is 0.1 mass% to 3.0 mass%. [4] The zirconia sintered body according to any one of [1] to [3], wherein the content of manganese is 0.5 mass% to 2.0 mass%. [5] The zirconia sintered body according to any one of [1] to [4], having an alumina content of more than 0 mass% and not more than 30 mass%. [6] The zirconia sintered body according to any one of [1] to [5], having a difference of 2θ of the peak top attributable to the (400) plane of tetragonal zirconia from 2θ of the peak top attributable to the (004) plane of tetragonal zirconia of 1.55° or more. [7] Lightness L ＊ [8] The zirconia sintered body according to any one of [1] to [6], having a total light transmittance of 0.1% or less at a thickness of 0.5 mm. [9] A zirconia powder containing a stabilizing element, niobium, manganese, and alumina, wherein the content of the stabilizing element is 2.0 mol% or more and 5.5 mol% or less, the niobium content is 0.1 mass% or more and 3.0 mass% or less, the manganese content is 0.5 mass% or more and 2.0 mass% or less, and the alumina content is more than 0 mass% and 30 mass% or less, and the 10% particle size in the cumulative particle size distribution of the powder is 0.15 μm or more and 0.5 μm or less, and the 90% particle size is 0.5 μm or more and 1.5 μm or less.

[10] A zirconia powder having a BET specific surface area of ​​8.0 m ２ / g or more 12m ２

[11] A member comprising the zirconia sintered body according to any one of [1] to [8].

[0008] Schematic diagram of the drop ball test equipment Schematic diagram of the sample for the drop ball test Schematic diagram showing the drop ball test

[0009] An example of an embodiment of the present disclosure will be described below. The present disclosure includes any combination of the configurations and parameters disclosed herein, and also includes any combination of the upper and lower limits of the values ​​disclosed herein. (Sintered Body) This embodiment is a zirconia sintered body containing zirconia, niobium, manganese, and alumina containing a stabilizing element, wherein the crystallite diameter calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia is 25 to 100 nm (hereinafter also referred to as the "sintered body of this embodiment"). Furthermore, the sintered body of this embodiment is a stabilizing element-containing zirconia sintered body containing niobium, manganese, and aluminum, and wherein the crystallite diameter calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia is 25 to 100 nm. Among the additive elements conventionally known to zirconia sintered bodies, the zirconia sintered body contains additive components including a combination of niobium, manganese, and alumina, and by satisfying this constitution, the zirconia sintered body has high impact resistance and shielding properties that prevent the base material from showing through.

[0010] The sintered body of the present embodiment is a sintered body containing zirconia containing a stabilizing element, a sintered body having zirconia containing a stabilizing element as a main phase, and further a sintered body in which zirconia accounts for the largest proportion (particularly, mass proportion) of the components constituting the sintered body, and is a so-called zirconia sintered body. The stabilizing element is an element that has the function of stabilizing zirconia, and the stabilizing element contained in the sintered body of this embodiment is one or more selected from the group consisting of calcium (Ca), magnesium (Mg), scandium (Sc), lanthanum (La), yttrium (Y), neodymium (Nd), cerium (Ce), gadolinium (Gd), erbium (Er) and ytterbium (Yb), one or more selected from the group consisting of calcium, yttrium, lanthanum, neodymium, gadolinium, erbium and ytterbium, one or more selected from the group consisting of yttrium, lanthanum, neodymium, gadolinium and erbium, one or more selected from the group consisting of yttrium, lanthanum and neodymium, one or more selected from the group consisting of yttrium and neodymium, one or more selected from the group consisting of yttrium and lanthanum, one or more selected from the group consisting of yttrium and erbium, or yttrium.

[0011] The sintered body of this embodiment may contain two or more stabilizing elements, and in this case, the stabilizing elements may be two or more selected from the group consisting of calcium, magnesium, scandium, lanthanum, yttrium, neodymium, cerium, gadolinium, erbium, and ytterbium, and preferably a combination of yttrium and a stabilizing element other than yttrium (hereinafter, when the stabilizing elements contained in the sintered body are such a combination, the stabilizing element other than yttrium is also referred to as a "sub-stabilizing element"). The sub-stabilizing element contained in the sintered body of this embodiment is preferably one or more selected from the group consisting of calcium, magnesium, scandium, lanthanum, neodymium, cerium, gadolinium, erbium, and ytterbium, more preferably one or more selected from the group consisting of lanthanum, erbium, and neodymium, even more preferably one or more selected from the group consisting of lanthanum, erbium, or neodymium, and even more preferably erbium.

[0012] The content of the stabilizing element (hereinafter also referred to as the "stabilizing element amount", and when the stabilizing element is yttrium or the like, also referred to as the "yttrium amount", etc.) is the amount that stabilizes the zirconia crystal phase, and is preferably 2.0 mol% or more and 5.5 mol% or less. The stabilizing element amount is, for example, more than 0 mol%, 1.5 mol% or more, 2.0 mol% or more, or 2.8 mol% or more, and less than 8.5 mol%, 5.5 mol% or less, 4.0 mol% or less, or 3.5 mol% or less. When the stabilizing element amount is 2.0 mol% or more and 5.5 mol% or less, the zirconia in the sintered body is mainly composed of tetragonal zirconia. The amount of stabilizing elements in the sintered body of this embodiment is preferably more than 0 mol% and less than 8.5 mol%, 1.5 mol% to 5.5 mol%, 2.0 mol% to 4.0 mol%, or 2.8 mol% to 3.5 mol%.

[0013] When a sub-stabilizing element is contained, the total content of one or more sub-stabilizing elements (hereinafter also referred to as "sub-stabilizing element amount") is greater than 0 mol%, 0.05 mol% or more, 0.10 mol% or more, 0.20 mol% or more, or 1.0 mol% or more, and less than 5.5 mol%, 4.0 mol% or less, 3.0 mol% or less, or 1.9 mol% or less. The sub-stabilizing element amount is preferably greater than 0 mol% and less than 5.5 mol%, 0.05 mol% or more and 4.0 mol% or less, 0.10 mol% or more and 3.0 mol% or less, 0.20 mol% or more and 1.9 mol% or less.

[0014] The content of each stabilizing element is arbitrary as long as the total content of the stabilizing elements satisfies the above-mentioned stabilizing element amount. The following contents can be exemplified as the content of each stabilizing element.

[0015] The amount of yttrium is, for example, more than 0 mol%, 1.0 mol% or more, or 1.5 mol% or more, and less than 4.0 mol%, 3.5 mol% or less, 3.0 mol% or less, or less than 3.0 mol%, and is preferably more than 0 mol% and less than 4.0 mol%, 1.0 mol% or more and 3.5 mol% or less, or 1.5 mol% or more and less than 3.0 mol%.

[0016] When the sub-stabilizing element is erbium, the amount of erbium may be more than 0 mol%, 0.03 mol% or more, or 1.0 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, or 1.9 mol% or less, and is preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 3.0 mol% or less, 0.03 mol% or more and 2.0 mol% or less, or 1.0 mol% or more and 1.9 mol% or less.

[0017] When the secondary stabilizing element is neodymium, the neodymium amount may be more than 0 mol%, 0.01 mol% or more, 0.03 mol% or more, 0.09 mol% or more, 0.2 mol% or more, or 0.25 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, 0.5 mol% or less, or 0.4 mol% or less, and more preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 2.0 mol% or less, 0.03 mol% or more and 0.5 mol% or less, or 0.09 mol% or more and 0.4 mol% or less.

[0018] When the secondary stabilizing element is lanthanum, the amount of lanthanum may be more than 0 mol%, 0.01 mol% or more, 0.03 mol% or more, or 0.1 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, or 0.5 mol% or less, and more preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 0.5 mol% or less, or 0.1 mol% or more and 0.5 mol% or less.

[0019] In this embodiment, the "amount of stabilizing element" is the ratio (mol %) of the total amount of the stabilizing element converted into an oxide to the total amount of zirconia and the stabilizing element converted into an oxide, and the "amount of sub-stabilizing element" is the ratio (mol %) of the total amount of the sub-stabilizing element converted into an oxide to the total amount of zirconia and the sub-stabilizing element converted into an oxide.

[0020] The sintered body of this embodiment contains niobium (Nb). By including niobium, the impact resistance and light-shielding properties of the sintered body are expected to be improved. The niobium content (hereinafter also referred to as "niobium amount") may be greater than 0 mass%, greater than 0.1 mass%, 0.5 mass% or more, 1.0 mass% or more, or 1.5 mass% or more, and may be 3.0 mass% or less, 2.5 mass% or less, or 2.0 mass% or less. The niobium amount of the sintered body of this embodiment may be greater than 0 mass% and 3.0 mass% or less, 1.0 mass% or more and 2.5 mass% or less, or 1.5 mass% or more and 2.0 mass% or less.

[0021] The sintered body of this embodiment contains manganese (Mn). The inclusion of manganese not only improves the light-shielding properties of the sintered body, but also makes it easier to obtain a dense sintered body even when sintered at a relatively low temperature. The manganese content (hereinafter also referred to as "manganese amount") can be greater than 0% by mass and less than 3.0% by mass, and is preferably 0.1% by mass to 2.5% by mass, 0.5% by mass to 2.0% by mass, or 0.8% by mass to 1.75% by mass. The manganese amount may also be greater than 0% by mass, greater than 0.1% by mass, 0.25% by mass, 0.5% by mass, or 0.8% by mass, and may be 3.0% by mass or less, 2.5% by mass or less, 2.0% by mass or less, or 1.75% by mass or less.

[0022] The manganese contained in the sintered body of this embodiment may be in any state, and for example, a part of it may be solid-solved in zirconia in the sintered body. ３ O ４ , Mn ２ O ３ and MnO ２ The manganese contained in the sintered body of this embodiment may be one or more manganese oxides selected from the group consisting of Mn ３ O ４ and a composite oxide with aluminum.

[0023] The sintered body of this embodiment is made of alumina (Al ２ O ３). The alumina content (hereinafter also referred to as "alumina amount") can be more than 0 mass% and less than 30 mass%. By including alumina, a dense sintered body can be easily obtained even at relatively low temperatures. To improve shielding properties, the alumina amount is preferably 0 mass% or more, more than 0 mass%, 0.005 mass% or more, 0.05 mass% or more, 0.25 mass% or more, 5 mass% or more, or 8 mass% or more. On the other hand, to improve mechanical properties such as static strength, the alumina amount may be less than 30 mass%, 25 mass% or less, or 20 mass% or less. The alumina amount of the sintered body of this embodiment can be more than 0 mass% and 25 mass% or less, or 8 mass% or more and 20 mass% or less.

[0024] In this embodiment, the amount of alumina is the mass ratio of aluminum converted into oxide to the total mass of zirconia and metal elements converted into oxide.

[0025] Alumina may be contained as at least one of alumina particles and aluminum-containing composite oxide particles, or further as alumina particles, that is, second phase particles, and a part of these may be solid-dissolved in zirconia.

[0026] The sintered body of this embodiment may contain a pigment component as long as the effects of the present invention are achieved. This allows the sintered body to exhibit any color tone different from the original color tone of zirconia. The pigment component contained in the sintered body refers to a component (element) that has the function of coloring the sintered body. Note that the above-mentioned stabilizing elements may also include elements that have the function of coloring the sintered body. For convenience, in calculating the composition in this embodiment, these stabilizing elements are not included in the pigment components but are calculated as stabilizing elements. Examples of stabilizing elements that have the function of coloring the sintered body include neodymium, cerium, and erbium.

[0027] The pigment component contained in the sintered body of this embodiment is at least one of an element and its compound having the function of coloring zirconia. For example, a compound containing a metal element, or even a transition metal element other than manganese and a compound containing the same, is preferred. Specific pigment components are more preferably one or more elements selected from the group consisting of vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu), and compounds containing one or more of these elements. Oxides containing one or more elements selected from the group consisting of iron, cobalt, and nickel are even more preferred. For example, by sintering a mixture of zirconia powder and pigment powder, the pigment powder-derived coloring element or a compound containing the coloring element can be included as a pigment component in the zirconia sintered body. However, although manganese is also an element that has the function of coloring the sintered body, for convenience, manganese is not included in the pigment component in this embodiment. Furthermore, the sintered body of this embodiment preferably does not contain zinc.

[0028] The content of the pigment component in the sintered body of this embodiment (hereinafter also referred to as the "pigment component amount," and when the pigment component is iron or the like, also referred to as the "iron amount") is preferably 0% by mass or more, more than 0% by mass, 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, and is preferably 5.0% by mass or less, 3.5% by mass or less, 3.0% by mass or less, 1.0% by mass or less, or 0.7% by mass or less. Examples of the pigment component amount in the sintered body of this embodiment include 0% by mass or more and 5.0% by mass or less, 0.01% by mass or more and 3.0% by mass or less, 0.1% by mass or more and 1.0% by mass or less, or 0.1% by mass or more and 0.7% by mass or less.

[0029] The sintered body of this embodiment is made of silica (SiO ２ ), titania (TiO ２ ) and gallium oxide (Ga ２ O ３) group. By including such an additive component, a sintered body having desired mechanical properties can be obtained. The content of the additive component (hereinafter also referred to as "additive component amount") is 0 mass% or more, 0.5 mass% or more, or 1.0 mass% or more, and 5.0 mass% or less, or 2.5 mass% or less. Furthermore, the amount of the additive component can be, for example, 0 mass% or more to 5.0 mass% or less, or 1.0 mass% or more to 2.5 mass% or less.

[0030] In the sintered body of this embodiment, the niobium, manganese, pigment component, and additive component may each be contained in the sintered body in any form, and may be contained as at least one of a compound, a composite oxide, and an oxide, or a part or all of them may be contained as a solid solution in zirconia.

[0031] In the present embodiment, the niobium amount, manganese amount, alumina amount, pigment component amount, and additive component amount are the mass proportions (mass %) of niobium, manganese, aluminum, pigment component, and additive component, respectively, calculated as oxides, relative to the total mass of zirconia and metal elements calculated as oxides.

[0032] In this embodiment, the oxide equivalents are, for example, CaO for calcium, MgO for magnesium, and Sc for scandium. ２ O ３ , yttrium is Y ２ O ３ , the lantern is La ２ O ３ , neodymium is Nd ２ O ３ , cerium is CeO ２ , gadolinium is Gd ２ O ３ , erbium is Er ２ O ３ , ytterbium is Yb ２ O ３ , niobium is Nb ２ O ５ , aluminum is Al ２ O ３ , silicon is SiO ２ , gallium is Ga ２ O ３ , vanadium is V２ O ５ , chromium is Cr ２ O ３ , iron is Fe ２ O ３ , and cobalt is Co ３ O ４ , manganese is Mn ３ O ４ Nickel is NiO, copper is CuO, and zinc is ZnO.

[0033] The sintered body of this embodiment is made of hafnia (HfO ２ In this embodiment, the content of each component of the sintered body is calculated by dividing hafnia by zirconia (ZrO ２ ) and calculate these values.

[0034] For example, alumina, niobium, manganese and alumina, and iron oxide (Fe ２ O ３ ) and cobalt oxide (Co ３ O ４ The composition (content of each component) of the zirconia sintered body (the same applies to the powder described below) containing gadolinium, lanthanum, and yttrium as stabilizing elements can be determined as follows.

[0035] Zirconia and metal element amount converted into oxide [g] = Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ Pigment component amount [mass%] = {(Fe ２ O ３ +Co ３ O ４ ) / (Gd ２ O３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )}×100 Iron content [mass%] = {Fe ２ O ３ / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )×100 Cobalt content [mass%] = {Co ３ O ４ / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )}×100 Alumina content [mass%]={Al ２ O ３ / (Gd ２ O ３ +La ２ O ３ +Y ２ O３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )} × 100 Manganese content [mass%] = {Mn ３ O ４ / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )} × 100 Niobium content [mass%] = {Nb ２ O ５ / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ +Nb ２ O ５ +Mn ３ O ４ +Al ２ O ３ +Fe ２ O ３ +Co ３ O ４ )}×100 Stabilizing element amount [mol%]={(Gd ２ O ３ +La ２ O ３ +Y ２ O ３ ) / (Gd ２ O ３ +La ２ O３ +Y ２ O ３ + ZrO ２ )}×100 Amount of substabilizing element [mol%]={(Gd ２ O ３ +La ２ O ３ ) / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ )} × 100 Gadolinium content [mol%] = {(Gd ２ O ３ ) / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ )} × 100 Lanthanum amount [mol%] = {(La ２ O ３ ) / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ )}×100 Yttrium content [mol%]={(Y ２ O ３ ) / (Gd ２ O ３ +La ２ O ３ +Y ２ O ３ + ZrO ２ )}×100 The sintered body of the present embodiment has a crystallite diameter (hereinafter, "D") calculated from a powder X-ray diffraction (hereinafter, also referred to as "XRD") peak assigned to the (111) plane of tetragonal zirconia. ｔ " or simply "crystallite size.") is 25 nm or more and 100 nm or less. D ｔ When the value of D is within the above range, the impact resistance of the zirconia sintered body is improved. ｔis preferably 25 nm or more or 30 nm or more, and D ｔ is preferably 90 nm or less, 80 nm or less, or 75 nm or less. ｔ is, for example, 25 nm or more and 90 nm or less, 25 nm or more and 80 nm or less, or 30 nm or more and 75 nm or less.

[0036] The sintered body of this embodiment contains niobium, manganese, and alumina, and the above-mentioned D ｔ One of the reasons why high impact resistance and high light-shielding properties are obtained by satisfying the above condition is thought to be as follows. That is, the impact resistance is likely to be improved by containing manganese and alumina. ｔ This allows sintering under the conditions of (a) and (b), and the interaction between manganese and niobium promotes the segregation of niobium in the sintered body. It is believed that the promotion of niobium segregation makes it easier for the phase transformation of zirconia to occur, resulting in a zirconia sintered body that has high impact resistance and high light-shielding properties despite containing alumina, which reduces impact resistance. ｔ If the grain size exceeds 100 nm, the crystal grain size of the sintered body becomes large, and large pores are likely to be formed as defects in the sintered body, which is thought to result in a decrease in impact resistance.

[0037] As will be described later, the XRD peak attributed to the (111) plane of tetragonal zirconia is measured as an XRD peak having a peak top at 2θ=30±0.5° in XRD measurement using CuKα radiation as a radiation source. ｔ can also be regarded as the crystallite diameter calculated from an XRD peak having a peak top at 2θ=30±0.5° measured in an XRD measurement using CuKα radiation as a radiation source.

[0038] D ｔ can be calculated from the following formula using the XRD pattern of the zirconia sintered body.

[0039] D ｔ = Kλ / B ｔ cosθ ｔ (1) In formula (1), D ｔis the crystallite diameter (nm) calculated from the XRD peak assigned to the (111) plane of tetragonal zirconia, K is the Scherrer constant (K=1), λ is the wavelength of the X-ray used in the XRD measurement (0.15418 nm), B ｔ is the broadening (rad) of the XRD peak assigned to the (111) plane of tetragonal zirconia, θ ｔ is the Bragg angle (rad) of the peak attributed to the (111) plane of tetragonal zirconia.

[0040] The XRD peaks attributable to the (111) plane of tetragonal zirconia and the (111) plane of cubic zirconia are measured in overlapping fashion. In this embodiment, the XRD peaks attributable to the (111) plane of tetragonal zirconia and the (111) plane of cubic zirconia are not distinguished from each other, and the overlapping peaks are considered to be XRD peaks attributable to the (111) plane of tetragonal zirconia.

[0041] In this embodiment, the XRD pattern of the zirconia sintered body including the XRD peak attributable to the (111) plane of tetragonal zirconia can be measured using a general crystallinity analysis X-ray diffractometer (for example, device name: Ultima IV, manufactured by RIGAKU Corporation). The following conditions can be mentioned as measurement conditions.

[0042] Radiation source: CuKα ray (λ=0.15418 nm) Tube voltage: 45 kV Tube current: 40 mA Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=26° or more and 33° or less Goniometer: Radius 185 mm A disk-shaped sintered body having a diameter of 20 mm and a thickness of 1.0 mm was used as the measurement sample, and the surface to be evaluated was mirror-polished (surface roughness Ra≦0.02 μm), and the polished surface was irradiated with X-rays for measurement.

[0043] In the above-described XRD measurement, the XRD peaks having peak tops at the following 2θ may be considered as XRD peaks attributable to the respective crystal planes of zirconia in this embodiment.

[0044] The (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° The (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° The (111) plane of tetragonal zirconia: 2θ = 30 ± 0.5° The patterns obtained by the above-mentioned XRD pattern measurement can be analyzed using integrated powder X-ray analysis software (PDXL, manufactured by Rigaku Corporation). The analysis calculates the broadening (rad) of each peak and the integrated intensity of each peak.

[0045] The zirconia contained in the sintered body of this embodiment preferably contains tetragonal zirconia (i.e., the zirconia crystalline phase contains a tetragonal phase) and is mainly composed of tetragonal zirconia. "Zirconia mainly composed of tetragonal zirconia" means that the zirconia crystalline phase is mainly composed of tetragonal zirconia, and 50% by volume or more of the zirconia crystalline phase is tetragonal. In the sintered body of this embodiment, it is preferable that 50% by volume or more or 60% by volume or more of the zirconia crystalline phase is tetragonal, and it is preferable that 100% by volume or less or 90% by volume or less is tetragonal.

[0046] Furthermore, the crystalline phase of the zirconia contained in the sintered body of this embodiment may include at least one of a cubic phase and a monoclinic phase in addition to the tetragonal phase. That is, the zirconia contained in the sintered body of this embodiment may consist of at least one of tetragonal zirconia, cubic zirconia, and monoclinic zirconia. In other words, the crystalline phase of the zirconia contained in the sintered body of this embodiment may consist of at least one of a tetragonal phase, a cubic phase, and a monoclinic phase. Note that, for convenience, in this embodiment, the crystalline phase of the zirconia may be considered to consist of one or more phases selected from the group consisting of a tetragonal phase, a cubic phase, and a monoclinic phase (that is, the zirconia consists of one or more phases selected from the group consisting of tetragonal zirconia, cubic zirconia, and monoclinic zirconia).

[0047] In the sintered body of this embodiment, the difference in 2θ between the peak top of the XRD peak attributable to the (400) plane of the tetragonal crystal (tetragonal zirconia) and the peak top of the XRD peak attributable to the (004) plane of the tetragonal crystal (tetragonal zirconia) in the XRD pattern of the center of the sintered body (hereinafter also referred to as "2θ difference") is preferably 1.55° or more. A 2θ difference of 1.55° or more improves impact resistance. The 2θ difference is preferably 1.55° or more, 1.57° or more, or 1.60° or more, and may also be 3.0° or less, 2.5° or less, 2.2° or less, or 2.0° or less. The 2θ difference of the sintered body of this embodiment may be 1.55° or more to 3.0° or less, 1.57° or more to 2.5° or less, or 1.60° or more to 2.0° or less.

[0048] In this embodiment, the X-ray diffraction pattern including the XRD peaks attributable to the zirconia tetragonal (004) plane and (400) plane may be measured in the same manner as the above-described XRD measurement, except that the measurement conditions are as follows:

[0049] Radiation source: CuKα radiation (λ=0.15418 nm) Tube voltage: 45 kV Tube current: 40 mA Measurement mode: Continuous scan Scan speed: 2° / min Step width: 0.02° Measurement range: 2θ=72° or more and 76° or less Goniometer: Radius 185 mm In the above-described XRD pattern measurement, the XRD peaks attributable to each crystal plane of zirconia contained in the central part of the zirconia sintered body of this embodiment are measured as XRD peaks having peak tops at the following 2θ:

[0050] XRD peak corresponding to the (004) plane of tetragonal zirconia: 2θ=72.5±0.5° XRD peak corresponding to the (400) plane of tetragonal zirconia: 2θ=74.5±0.5° The sintered body of this embodiment conforms to CIE1976 (L ＊ a ＊ b ＊ ) Lightness L in color space ＊ The sintered body of the present embodiment preferably has a lightness L ＊is preferably 40 or more, 42 or more, or 44 or more, and is preferably 65 or less, or 60 or less. This makes it easy for a thin sintered body, for example, a sintered body with a sample thickness of 0.5 mm, to have shielding properties.

[0051] The sintered body of this embodiment is CIE1976 (L ＊ a ＊ b ＊ ) Chromaticity a in color space ＊ and b ＊ is arbitrary, but a ＊ is between -10 and 10, b ＊ is between -10 and 10.

[0052] Lightness L ＊ and chromaticity a ＊ and b ＊ The lightness L can be measured using a general spectrophotometer (for example, CM-700d, manufactured by Konica Minolta) in accordance with a method in accordance with JIS Z 8722. ＊ and chromaticity a ＊ and b ＊ The measurement conditions are as follows: The measurement may be performed using a black board as the background (so-called black background measurement).

[0053] Light source: F2 light source Viewing angle: 10° Measurement method: SCI A disk-shaped sintered body having a diameter of 20 mm and a thickness of 1.8 mm is used as a measurement sample, and the surface to be evaluated is mirror-polished (surface roughness Ra≦0.02 μm), and the color tone is evaluated. The effective area for color tone evaluation is 10 mm in diameter.

[0054] The sintered body of this embodiment has impact resistance, i.e., it is a sintered body that is resistant to fracture such as cracking when subjected to impact, and is particularly resistant to fracture even when made into a thin shape. Specifically, in a ball drop test in which a sample of the sintered body of this embodiment with a thickness of 0.5 mm is bonded to a cemented carbide plate, and a steel ball (diameter 23 mm, material: bearing steel SUJ2) with a mass of 25 g, 50 g, or 95 g is dropped onto the sintered body from a height of 100 cm, it is found that it is resistant to fracture such as cracking. Furthermore, the sintered body of this embodiment does not break when subjected to a ball drop test in which a sample having a thickness of 0.5±0.05 mm is dropped from a height of 100 cm three times by gravity using an SUJ2 steel ball having a diameter of 23 mm and a mass of 95 g.Furthermore, it is preferable that the sintered body does not break when subjected to a ball drop test in which a sample having a thickness of 0.5±0.05 mm is dropped from a height of 100 cm three times by gravity using an SUJ2 steel ball having a diameter of 23 mm and a mass of 25 g, three times by gravity using an SUJ2 steel ball having a diameter of 23 mm and a mass of 50 g, and three times by gravity using an SUJ2 steel ball having a diameter of 23 mm and a mass of 95 g.

[0055] In the ball drop test, "fracture" is judged to have occurred when the sintered body is split or cracked due to the free fall of a steel ball.

[0056] The sintered body of this embodiment has high light-blocking properties even in a thin shape. For example, when it is made into a laminated member consisting of the sintered body of this embodiment and an underlying material, it is preferable that the sintered body of this embodiment exhibits light-blocking properties that prevent the underlying material from showing through when observed in the stacking direction.

[0057] In order to achieve such light-blocking properties, the total light transmittance (hereinafter also simply referred to as "total light transmittance") of the sintered body of this embodiment to a D65 light source at a sample thickness of 0.5±0.05 mm is preferably 10% or less, 1% or less, or less than 0.1%. A lower total light transmittance means higher light-blocking properties. The total light transmittance is preferably 0%, but the total light transmittance of the sintered body of this embodiment may be 0% or more, more than 0%, or 0.01% or more, and examples thereof include 0% to 10%, 0% to 1%, 0% to less than 0.1%, or more than 0% but less than 0.1%.

[0058] In this embodiment, the total light transmittance is a value measured under the following conditions using a general haze meter (for example, NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with a method in accordance with JIS K 7361-1.

[0059] Measurement light source: D65 light source Sample thickness: 0.5±0.05 mm Sample diameter: 20 mm Surface roughness: Ra≦0.02 μm The total light transmittance means the ratio of the total intensity of diffuse transmitted light and direct transmitted light to the intensity of incident light, and these have the following relationship:

[0060] Incident light = Reflected light + (Diffuse transmitted light + Direct transmitted light) The shape of the sintered body of this embodiment may be, for example, one or more shapes selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral. Furthermore, any shape suitable for achieving a desired purpose, such as various applications, may be used.

[0061] The sintered body of the present embodiment can be used for conventional zirconia sintered bodies, particularly for one or more applications selected from the group consisting of structural materials, optical materials, and dental materials, but can also be used as components that require advanced processing, such as decorative items, covers for accessories such as watches and housings, and exterior components for portable electronic devices such as mobile phones. In particular, because of its impact resistance, it is preferably used for portable applications where drops and collisions are likely to occur. (Powder) The sintered body of this embodiment can be produced by molding and sintering a raw material powder having a similar composition. A preferred powder for producing the sintered body of this embodiment is a zirconia powder containing a stabilizing element, zirconia, niobium, manganese, and alumina, in which the stabilizer content is 2.0 mol% or more and 5.5 mol% or less, the niobium content is 0.1 mass% or more and 3.0 mass% or less, the manganese content is 0.5 mass% or more and 2.0 mass% or less, and the alumina content is more than 0% and 30 mass% or less, and the 10% particle diameter (hereinafter also referred to as "D10") in the cumulative particle size distribution of the powder is 0.15 μm or more and 0.5 μm or less, and the 90% particle diameter (hereinafter also referred to as "D90") is 0.5 μm or more and 1.5 μm or less.

[0062] The powder of this embodiment is a zirconia powder containing a stabilizing element. The stabilizing element is an element that has the function of stabilizing zirconia, and the stabilizing element contained in the powder of this embodiment is preferably one or more selected from the group consisting of calcium, magnesium, scandium, lanthanum, yttrium, neodymium, cerium, gadolinium, erbium, and ytterbium, and is preferably one or more selected from the group consisting of calcium, lanthanum, yttrium, neodymium, gadolinium, erbium, and ytterbium, one or more selected from the group consisting of yttrium, lanthanum, neodymium, gadolinium, and erbium, one or more selected from the group consisting of yttrium, lanthanum, and neodymium, one or more selected from the group consisting of yttrium and neodymium, one or more selected from the group consisting of yttrium and lanthanum, one or more selected from the group consisting of yttrium and erbium, or yttrium.

[0063] The powder of this embodiment may contain two or more stabilizing elements. In this case, the stabilizing elements may be two or more selected from the group consisting of calcium, magnesium, scandium, lanthanum, yttrium, neodymium, cerium, gadolinium, erbium, and ytterbium. A combination of yttrium and a stabilizing element (sub-stabilizing element) other than yttrium is preferred. The sub-stabilizing element contained in the sintered body of this embodiment is preferably one or more selected from the group consisting of calcium, magnesium, scandium, lanthanum, neodymium, cerium, gadolinium, erbium, and ytterbium, more preferably one or more selected from the group consisting of lanthanum, erbium, and neodymium, even more preferably one or more selected from the group consisting of lanthanum, erbium, or neodymium, and even more preferably erbium. The amount of the stabilizing element in the powder of this embodiment is an amount that stabilizes the zirconia crystal phase, and is preferably 2.0 mol% to 5.5 mol%. The amount of the stabilizing element is greater than 0 mol%, 1.5 mol% or more, 2.0 mol% or more, or 2.8 mol% or more, and less than 8.5 mol%, 5.5 mol% or less, 4.0 mol% or less, or 3.5 mol% or less. When the amount of the stabilizing element is 2.0 mol% or more and 5.5 mol% or less, the zirconia in the sintered body is mainly composed of tetragonal zirconia. The amount of the stabilizing element in the sintered body of this embodiment is preferably greater than 0 mol% and less than 8.5 mol%, 1.5 mol% or more and 5.5 mol% or less, 2.0 mol% or more and 4.0 mol% or less, or 2.8 mol% or more and 3.5 mol% or less.

[0064] When the powder of this embodiment contains a sub-stabilizing element, the amount of the sub-stabilizing element in the powder is, for example, more than 0 mol%, 0.05 mol% or more, 0.10 mol% or more, 0.20 mol% or more, or 1.0 mol% or more, and less than 5.5 mol%, 4.0 mol% or less, 3.0 mol% or less, or 1.9 mol% or less. The amount of the sub-stabilizing element is preferably more than 0 mol% and less than 5.5 mol%, 0.05 mol% or more and 4.0 mol% or less, 0.10 mol% or more and 3.0 mol% or less, 0.20 mol% or more and 1.9 mol% or less.

[0065] As long as the total content of the stabilizing elements satisfies the above-mentioned stabilizing element amount, the content of each stabilizing element is arbitrary, and the following contents can be exemplified.

[0066] The amount of yttrium is, for example, more than 0 mol%, 1.0 mol% or more, or 1.5 mol% or more, and less than 4.0 mol%, 3.5 mol% or less, 3.0 mol% or less, or less than 3.0 mol%, and is preferably more than 0 mol% and less than 4.0 mol%, 1.0 mol% or more and 3.5 mol% or less, or 1.5 mol% or more and less than 3.0 mol%.

[0067] When the stabilizing element other than yttrium is erbium, the amount of erbium may be more than 0 mol%, 0.03 mol% or more, or 1.0 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, or 1.9 mol% or less, and is preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 3.0 mol% or less, 0.03 mol% or more and 2.0 mol% or less, or 1.0 mol% or more and 1.9 mol% or less.

[0068] When the stabilizing element other than yttrium is neodymium, the neodymium amount may be more than 0 mol%, 0.01 mol% or more, 0.03 mol% or more, 0.09 mol% or more, 0.2 mol% or more, or 0.25 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, 0.5 mol% or less, or 0.4 mol% or less, and more preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 2.0 mol% or less, 0.03 mol% or more and 0.5 mol% or less, or 0.09 mol% or more and 0.4 mol% or less.

[0069] When the stabilizing element other than yttrium is lanthanum, the amount of lanthanum may be more than 0 mol%, 0.01 mol% or more, 0.03 mol% or more, or 0.1 mol% or more, and less than 4.0 mol%, 3.0 mol% or less, 2.0 mol% or less, or 0.5 mol% or less, and more preferably more than 0 mol% and less than 4.0 mol%, 0.01 mol% or more and 0.5 mol% or less, or 0.1 mol% or more and 0.5 mol% or less.

[0070] The powder of this embodiment contains niobium. The inclusion of niobium is expected to have the effect of improving the impact resistance and light-shielding properties of the resulting sintered body. The niobium content may be greater than 0 mass%, greater than 0.1 mass%, 0.5 mass% or more, 1.0 mass% or more, or 1.6 mass% or more, and may be 2.5 mass% or less, 2.5 mass% or less, or 2.0 mass% or less. The niobium content of the powder of this embodiment may be greater than 0 mass% and 3.0 mass% or less, 1.0 mass% or more and 2.5 mass% or less, or 1.5 mass% or more and 2.0 mass% or less.

[0071] The powder of this embodiment contains manganese. By including manganese, it is expected that the light-shielding properties of the resulting sintered body will be improved and that a dense body will be more easily obtained even at a relatively low temperature.

[0072] The manganese content may be greater than 0% by mass and not greater than 3.0% by mass, and is preferably 0.1% by mass to 2.5% by mass, 0.5% by mass to 2.0% by mass, or 0.8% by mass to 1.75% by mass. The manganese content may also be greater than 0%, greater than 0.1%, 0.25% by mass or greater, 0.5% by mass or greater, or 0.8% by mass or greater, and may be 3.0% by mass or less, 2.5% by mass or less, 2.0% by mass or less, or 1.75% by mass or less.

[0073] The powder of this embodiment may contain a pigment component. This allows the resulting sintered body to exhibit any color tone different from the original color tone of zirconia. The pigment component contained in the powder of this embodiment is at least one of an element and its compound that has the function of coloring zirconia. For example, a compound containing a metal element, or even a transition metal element and a compound containing such an element, is preferred. Specific pigment components are more preferably one or more elements selected from the group consisting of vanadium, chromium, iron, cobalt, nickel, and copper, and compounds containing one or more of these elements. Oxides containing one or more elements selected from the group consisting of iron, cobalt, and nickel are even more preferred. Furthermore, the powder of this embodiment preferably does not contain zinc. For example, by mixing a pigment powder with a zirconia powder and sintering the mixture, a coloring element derived from the pigment powder or a compound containing the coloring element can be contained as a pigment component in the zirconia sintered body.

[0074] When a pigment component is contained, the amount of the pigment component in the powder of this embodiment is preferably more than 0% by mass, 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more. The amount of the pigment component is, for example, 5.0% by mass or less, 3.5% by mass or less, or 3.0% by mass or less. In order to obtain a sintered body having desired mechanical properties, the powder of this embodiment may contain one or more additive components selected from the group consisting of silica, titania, and gallium oxide.

[0075] The powder of this embodiment may contain unavoidable impurities such as hafnia, etc. In this embodiment, the content of each component of the powder may be calculated by regarding hafnia as zirconia.

[0076] In the powder of this embodiment, the niobium, manganese, pigment component, and additive component may each be contained in the powder in any form, and may be contained as a compound, or further as at least one of a composite oxide and an oxide, or part or all of them may be contained as a solid solution in zirconia.

[0077] The powder of this embodiment contains alumina. The alumina amount can be greater than 0 mass% and less than 30 mass%. By including alumina (i.e., by including alumina greater than 0 mass%), the sintered body of this embodiment can be obtained by sintering at a lower temperature. Furthermore, by including alumina less than 30 mass%, the mechanical properties of the sintered body, such as static strength, tend to be improved. The alumina amount can be greater than 0 mass% and less than 30 mass%. By including alumina, a dense sintered body can be easily obtained even at relatively low temperatures. To improve shielding properties, the alumina amount is preferably 0 mass% or more, greater than 0 mass%, 0.005 mass% or more, 0.05 mass% or more, 0.25 mass% or more, 5 mass% or more, or 8 mass% or more. On the other hand, to improve mechanical properties, such as static strength, the alumina amount can be less than 30 mass%, 25 mass% or less, or 20 mass% or less. The alumina amount of the sintered body of this embodiment can be greater than 0 mass% and 25 mass% or less, or 8 mass% or more and 20 mass% or less.

[0078] The form of alumina in the powder of this embodiment is arbitrary, and a part or all of the alumina may be dissolved in the zirconia powder, or may react with an oxide other than zirconia to form a composite oxide.

[0079] The powder of this embodiment has a 10% particle diameter D10 of 0.15 μm or more and 0.50 μm or less in the cumulative particle size distribution of the powder, and a 90% particle diameter D90 of 0.50 μm or more and 1.5 μm or less in the cumulative particle size distribution of the powder. D10 and D90 are both indicators that indicate the secondary particle diameter distribution of the powder. By having D10 and D90 within these ranges, the stability of the tetragonal crystals of zirconia in the sintered body is controlled, and as a result, the crystallite diameter D ｔ It is considered that a sintered body having a particle size of 25 nm or more and 100 nm or less can be easily obtained.

[0080] The powder of this embodiment has a D10 of 0.15 μm or more and 0.50 μm or less, 0.20 μm or more and 0.48 μm or less, or 0.30 μm or more and 0.46 μm or less, for example. D10 is preferably 0.15 μm or more, 0.20 μm or more, or 0.30 μm or more, and 0.50 μm or less, 0.48 μm or less, or 0.46 μm or less. If D10 is small, the tetragonal crystals of zirconia in the sintered body become unstable, and the crystallite size tends to become small.

[0081] The powder of this embodiment has a D90 of 0.50 μm or more and 1.5 μm or less, 0.525 μm or more and 1.3 μm or less, 0.55 μm or more and 1.2 μm or less, or 0.55 μm or more and less than 1.0 μm. D90 is preferably 0.50 μm or more, more than 0.50 μm, 0.525 μm or more, or 0.55 μm or more, and 1.5 μm or less, 1.3 μm or less, 1.2 μm or less, or less than 1.0 μm. If D90 is large, the tetragonal crystals of zirconia in the sintered body become unstable, and the crystallite size tends to become small.

[0082] In this embodiment, D10 and D90 can be determined from a cumulative particle size distribution curve obtained by measuring using the HRA mode of a general Microtrac particle size distribution diameter (for example, device name: MT3000II, manufactured by Microtrac Bell). In order to break up agglomerations of powder such as powder granules, a slurry prepared by suspending a powder sample in pure water may be pretreated using an ultrasonic homogenizer or the like prior to measurement. Furthermore, a dispersant (for example, sodium hexametaphosphate) may be used when preparing the slurry.

[0083] The powder of this embodiment has a BET specific surface area of ​​8.0 m ２ / g or more 12m ２ / g or less, 8.2m ２ / g or more 11.5m ２ / g or less, or 8.4m ２ / g or more 11.0m ２ When the BET specific surface area is within this range, a sintered body having a crystallite diameter of 25 nm or more and 100 nm or less can be easily obtained.

[0084] In this embodiment, the BET specific surface area of ​​the powder is measured by a method conforming to JIS R 1626-1996, using a general flow-type automatic specific surface area measuring device (for example, Flowsorb III 2305, manufactured by Shimadzu Corporation) and nitrogen (N ２ Prior to the measurement, the powder may be pretreated in a vacuum atmosphere at 250° C. for 2 hours.

[0085] The powder of this embodiment may contain a molding aid. By including a molding aid, the molded body obtained by molding this embodiment has high strength. The molding aid may be a molding aid that can be applied to ceramic powder used in dry press molding, and may further be a molding aid that can improve the properties of a molded body obtained by dry press molding of ceramic powder. Examples of such molding aids include one or more selected from the group consisting of polyethylene glycol resins, polyvinyl alcohol resins, polyvinylpyrrolidone resins, and acrylic resins. Specific examples of molding aids include one or more selected from the group consisting of AS-1100, AS-1800, and AS-2000 (all product names, manufactured by Toagosei Co., Ltd.).

[0086] The powder of this embodiment may be a granulated powder (hereinafter also referred to as "powder granules"). The powder granules have an average granule diameter of 30 μm or more and 80 μm or less, and further have a bulk density of 1.00 g / cm. ３ 1.50g / cm or more ３ Further, 1.10 g / cm ３ 1.45g / cm or more ３ (Method for Producing Powder) Any method for producing the powder of this embodiment is possible as long as it can produce the powder. One example of a method for producing the powder of this embodiment is a production method including: heat-treating a composition containing a zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia and a stabilizing element source at 600°C or higher and 1250°C or lower to produce a calcined powder (hereinafter also referred to as a "powder calcining step"); and pulverizing the calcined powder, the niobium source, the alumina source, and the manganese source (hereinafter also referred to as a "pulverizing step").

[0087] In the powder calcination step, a composition (hereinafter also referred to as "raw material composition") containing a zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia and a stabilizing element source is provided.

[0088] Zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia can be produced by any method, including at least one of hydrothermal synthesis and hydrolysis. In the hydrothermal synthesis method, a zirconium salt is mixed with an alkali or the like in the presence of a solvent to obtain a coprecipitate, and the resulting mixture is then heat-treated at 100 to 200°C to obtain a zirconia sol. In the hydrolysis method, a zirconium salt is heated in the presence of a solvent to hydrolyze the zirconium salt, thereby obtaining a zirconia sol. Thus, the zirconia sol can be produced by at least one of hydrothermal synthesis and hydrolysis, with hydrolysis being preferred. Zirconium salts can be used as precursors in the method for producing a zirconia sol. Examples of zirconium salts include one or more selected from the group consisting of zirconium oxychloride, zirconium nitrate, zirconium chloride, and zirconium sulfate. At least one of zirconium nitrate and zirconium oxychloride is preferred, with zirconium oxychloride being more preferred.

[0089] The powder calcination step produces a calcined powder that is a precursor of the zirconia powder. The raw material composition may contain one or more sources selected from the group consisting of a niobium source, a manganese source, and an alumina source.

[0090] The stabilizing element source may be at least one of an oxide of the stabilizing element and a compound containing the stabilizing element that serves as a precursor thereof, and examples thereof include one or more selected from the group consisting of oxides, hydroxides, oxychlorides, chlorides, acetates, nitrates, and sulfates that serve as precursors of the oxides of the stabilizing element, with at least one of chlorides and nitrates being preferred. (Hereinafter, when the stabilizing element is yttrium or the like, these will also be referred to as "yttrium sources," etc.) The content of the stabilizing element source in the raw material composition may be equivalent to the amount of the stabilizing element in the target sintered body.

[0091] The yttrium source may be at least one of yttria and its precursor yttrium compound, and may be one or more selected from the group consisting of yttrium chloride, yttria, and yttrium carbonate, with yttrium chloride being preferred.

[0092] The erbium source may be at least one of erbia (erbium oxide) and its precursor erbium compound, and may be one or more selected from the group consisting of erbium chloride, erbia, and erbium carbonate, with erbium oxide being preferred.

[0093] The neodymium source may be at least one of neodia (neodymium oxide) and a neodymium compound that serves as a precursor thereof, and examples thereof include one or more selected from the group consisting of neodymium chloride, neodia, neodymium hydroxide, and neodymium carbonate, with neodia being preferred.

[0094] The lanthanum source may be at least one of lanthana (lanthanum oxide) and its precursor lanthanum compounds, and examples thereof include one or more selected from the group consisting of lanthanum chloride, lanthana, lanthanum hydroxide, and lanthanum carbonate, with lanthana being preferred.

[0095] The niobium source may be at least one of niobium oxide and a compound serving as a precursor thereof, and examples thereof include one or more selected from the group consisting of hydroxides, chlorides, alkoxides, nitrates, oxalates, and sulfates of germanium, which serve as precursors of niobium oxide. Niobium oxide and one or more selected from the group consisting of hydroxides and alkoxides of germanium, which serve as precursors of niobium oxide, are preferred. The content of the niobium source in the raw material composition may be equivalent to the niobium content of the target sintered body.

[0096] The alumina source is at least one of alumina and an aluminum-containing compound serving as a precursor thereof, and includes one or more selected from the group consisting of aluminum chloride, aluminum sulfate, aluminum nitrate, aluminum hydroxide, alumina sol, and alumina, with alumina being preferred. The content of the alumina source in the raw material composition may be equivalent to the alumina content in the target sintered body.

[0097] The manganese source is at least one of manganese oxide and a manganese-containing compound that serves as a precursor thereof, and includes one or more selected from the group consisting of manganese chloride, manganese carbonate, manganese oxide, and manganese hydroxide, with manganese oxide being preferred. The content of the manganese source in the raw material composition may be equivalent to the manganese content in the target sintered body.

[0098] Instead of a zirconia sol containing monoclinic zirconia, zirconium oxide may be used as the zirconia source, or stabilizing element-containing zirconia containing a stabilizing element may be used. Examples of stabilizing element-containing zirconia include yttrium-stabilized zirconia. When using stabilizing element-containing zirconia, any method can be used to incorporate the stabilizing element into zirconia. For example, a hydrated zirconia sol may be mixed with a stabilizing element source having a desired stabilizing element content, followed by drying, calcination, and water washing.

[0099] Furthermore, niobium-containing stabilized zirconia containing niobium and a stabilizing element may be used as the zirconia. When niobium-containing stabilized zirconia is used, any method can be used to incorporate niobium into the zirconia. For example, a method of mixing a hydrated zirconia sol with a stabilizing element source and a niobium source, followed by drying, calcining and washing with water, or a method of mixing a hydrated zirconia sol with a stabilizing element source, drying and calcining, and then mixing with a niobium source and calcining the mixture may be used.

[0100] Any mixing method may be used, preferably at least one of dry mixing and wet mixing, more preferably wet mixing, and even more preferably wet mixing using a ball mill.

[0101] In the powder calcination step, heat treatment is performed at 500°C or higher and 1250°C or lower, and further at 600°C or higher and 1250°C or lower. Heat treatment at 500°C or higher results in a powder that is easily densified by atmospheric sintering. On the other hand, heat treatment at 1250°C or lower results in a powder that is easily dispersible by pulverization. The heat treatment time can be appropriately changed depending on the heat treatment temperature, the amount of zirconia raw material composition to be treated, and the characteristics of the heat treatment furnace, and may be, for example, 30 minutes to 6 hours. The rate of temperature increase to the heat treatment temperature has little effect on the calcined powder obtained, and the rate of temperature increase may be, for example, 50°C / hour to 1000°C / hour.

[0102] The heat treatment may be carried out in any atmosphere, for example, an oxidizing atmosphere, a reducing atmosphere, an inert atmosphere, or a vacuum atmosphere, preferably an oxidizing atmosphere, and more preferably an air atmosphere.

[0103] The raw material composition to be subjected to the powder calcination step may contain the above-mentioned zirconia sol and the stabilizing element source, and all or part of the stabilizing element source may be solid-dissolved in the zirconia sol. For example, at least part of the stabilizing element source may be easily solid-dissolved in the zirconia sol by mixing a zirconium salt and the stabilizing element source and hydrolyzing the mixture, or by mixing a zirconium salt, the stabilizing element source, and an alkali or the like to form a coprecipitate.

[0104] In the pulverization process, the calcined powder is pulverized. Zirconia with a low content of stabilizing elements is prone to cracking and chipping during sintering. In contrast, pulverizing the calcined powder tends to increase the yield during sintering.

[0105] The pulverization method may be any method, as long as it is at least one of wet pulverization and dry pulverization, with wet pulverization being preferred. Specific examples of wet pulverization include one or more selected from the group consisting of a ball mill and a continuous media stirring mill, with a ball mill being preferred. The powder to be subjected to the pulverization step may be a calcined powder or a mixed powder containing the calcined powder, a niobium source, a manganese source, and an alumina source.

[0106] The powder to be subjected to the pulverization step may be a mixed powder containing a pigment component in addition to the above.

[0107] As a milling condition using a ball mill, for example, the calcined powder and a solvent (for example, water and / or alcohol, or water) are mixed to form a slurry in which the mass ratio of the powder mass to be subjected to the milling step to the slurry mass is 30% by mass to 60% by mass, and the slurry is milled using zirconia balls having a diameter of 0.5 mm to 15 mm as milling media. The milling time may be adjusted appropriately depending on the amount of calcined powder to be subjected to the treatment, and may be, for example, 8 hours to 100 hours.

[0108] After wet grinding, the mixture is dried by any method to obtain zirconia powder. Drying conditions include air atmosphere and a temperature of 110° C. to 200° C.

[0109] To improve the workability of the powder, the method for producing the powder may include a step of granulating the powder (hereinafter also referred to as the "granulation step"). Granulation may be performed by any method, including spray granulation of a slurry obtained by mixing the powder with a solvent. The solvent is at least one of water and alcohol, preferably water. (Method for producing a sintered body) The method for producing the sintered body of this embodiment is any method, including a production method having a step of sintering the powder of this embodiment. The powder may be subjected to the above step (hereinafter also referred to as the "sintering step") in any form, and it is preferable that the powder be in a form that allows the desired shape of the sintered body to be obtained, taking into consideration thermal shrinkage due to sintering. For example, the powder may be formed into a molded body (pressed powder body) and then subjected to sintering, or the molded body may be calcined to form a calcined body and then subjected to sintering.

[0110] The method for producing a sintered body according to this embodiment may include a step of molding the powder into a molded body (green compact) (hereinafter also referred to as a "molding step").

[0111] The raw material used for molding may be the powder of this embodiment, a powder slurry obtained by slurriing the powder of this embodiment, or a powder composite containing the powder of this embodiment and a binder. The binder may be any organic binder used in molding ceramics, and examples thereof include one or more selected from the group consisting of acrylic resins, polyolefin resins, waxes, and plasticizers. Specific examples of binders include one or more selected from the group consisting of AS-1100, AS-1800, and AS-2000 (all product names, manufactured by Toagosei Co., Ltd.).

[0112] The binder content can be, for example, 25% by volume or more and 65% by volume or less of the volume of the molded body at room temperature. Alternatively, the binder can be, for example, more than 0% by mass and 10% by mass of the molded body (100% by mass). The inclusion of a binder improves the shape stability of the resulting molded body.

[0113] The shape of the molded body may be any shape suitable for the purpose, taking into consideration shrinkage due to heat treatment such as sintering, and may include, for example, one or more shapes selected from the group consisting of spherical, approximately spherical, elliptical, disk-like, cylindrical, cubic, rectangular, polyhedral, and approximately polyhedral, and may be any shape suitable for the purpose.

[0114] The molding method may be any known molding method capable of converting the powder of this embodiment into a green compact, and is preferably one or more selected from the group consisting of uniaxial pressing, isostatic pressing, injection molding, extrusion molding, rolling granulation, slip casting, and slip casting, more preferably at least one of uniaxial pressing and isostatic pressing, even more preferably at least one of cold isostatic pressing and uniaxial pressing (powder press molding), and even more preferably uniaxial pressing followed by cold isostatic pressing.

[0115] Prior to sintering, a step of calcining the compact to obtain a calcined body (hereinafter also referred to as a "calcining step") may be included. By calcining the compact, a calcined body can be obtained in which the binder has been removed from the compact. The "calcined body" is a composition composed of fused particles, which retains the shape of at least some of the powder particles and has a structure in which the particles are necked together.

[0116] The conditions for the calcination step are arbitrary as long as the sintered body of this embodiment can be obtained by the subsequent sintering step. Examples of the conditions for the calcination step include heat treatment at a temperature at which densification of the molded body does not proceed, specifically, heat treatment in an air atmosphere at 400°C or higher but lower than 1100°C.

[0117] In the sintering step, a sintered body is obtained by sintering a molded body or a calcined body. Any sintering method can be used as long as sintering proceeds, and examples include one or more selected from the group consisting of atmospheric sintering, pressure sintering, and vacuum sintering, as well as other known sintering methods. Preferred sintering methods include atmospheric sintering, and even atmospheric sintering alone. This allows the sintered body of this embodiment to be obtained as a so-called atmospheric sintered body. Atmospheric sintering is a method in which the material to be sintered (e.g., powder, molded body, or calcined body) is sintered simply by heating without applying an external force during sintering.

[0118] The conditions for atmospheric sintering are preferably a holding temperature (sintering temperature) of 1050°C to 1600°C, 1100°C to 1550°C, 1100°C to 1500°C, 1150°C to 1500°C, 1200°C to 1500°C, or 1250°C to 1450°C. When the sintering temperature is within this range, a sintered body having a crystallite diameter of 25 nm to 100 nm is easily obtained. The sintering temperature is preferably higher than the calcination temperature.

[0119] The sintering atmosphere may be at least one of an air atmosphere and an oxygen atmosphere, with an air atmosphere being preferred. The temperature rise rate is 20°C / hour or more or 75°C / hour or more, and may be 500°C / hour or less or 200°C / hour or less, for example, 20°C / hour or more and 500°C / hour or less, or 75°C / hour or more and 200°C / hour or less. The sintering time may be appropriately set depending on the amount and size of the sintered material to be sintered and the characteristics of the sintering furnace. For example, the holding time at the sintering temperature may be 0.3 hours or more, 0.5 hours or more, or 1 hour or more, and may be 20 hours or less, 10 hours or less, or 5 hours or less, and may be 0.5 hours or more and 20 hours or less, 0.5 hours or more and 15 hours or less, or 1 hour or more and 5 hours or less.

[0120] In addition, since there is substantially no variation in the metal elements and their contents in the molding step, calcination step, and sintering step, in this embodiment, the composition of the metal components (inorganic substances) in the powder, and the resulting molded body, calcined body, and sintered body may be considered to be the same.

[0121] The present disclosure will be specifically described below with reference to examples. However, the present disclosure is not limited to these examples. (BET Specific Surface Area) In accordance with JIS R 1626-1996, a typical flow-type automatic specific surface area measuring device (device name: Flowsorb III2305, manufactured by Shimadzu Corporation) was used. ２ The BET specific surface area of ​​the powder was measured by the BET single-point method using a 1000-kJ / cm2 SiO2 SiO3 SiO4 SiO4 SiO5 SiO6 SiO6 SiO7 SiO8 SiO9 SiO10 SiO20 SiO21 SiO22 SiO30 SiO42 SiO50 SiO60 SiO70 SiO80 SiO90 SiO90 SiO10 SiO11 SiO12 SiO13 SiO14 SiO25 SiO26 SiO27 SiO30 SiO48 SiO50 SiO51 SiO52 SiO53 SiO54 SiO55 SiO60 SiO61 SiO72 SiO73 SiO74 SiO75 SiO80 SiO90 SiO91 SiO92 SiO95 SiO96 SiO97 SiO98 SiO9 ...

[0122] Radiation source: CuKα ray (λ = 0.15418 nm) Tube voltage: 45 kV Tube current: 40 mA Measurement mode: continuous scan Scan speed: 4 ° / min Step width: 0.02 ° Measurement range: 2θ = 26 ° or more and 33 ° or less Goniometer: radius 185 mm Using the XRD pattern of the obtained sintered body, the crystallite diameter Dt (nm) calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia was obtained from the formula (1). Note that the X-ray irradiation surface of the measurement sample was the sintered body surface (i.e., the sintered surface) of the sintered body immediately after sintering was ground by 0.3 mm in the depth direction to remove the sintered surface, and then polished with abrasive cloth, polished with a diamond slurry with an average particle size of 3 μm, and polished with colloidal silica of 0.03 μm, and then mirror-polished. (2θ Difference) The 2θ difference was determined from an XRD pattern obtained in the same manner except that the XRD measurement was carried out under the following conditions.

[0123] Radiation source: CuKα radiation (λ = 1.5418 nm) Tube voltage: 45 kV Tube current: 40 mA Measurement mode: Continuous scan Scan speed: 2° / min Step width: 0.02° Measurement range: 2θ = 72° to 76° Goniometer: Radius 185 mm The pattern obtained by the above XRD measurement was subjected to background removal and CuKα analysis using the integrated powder X-ray analysis software "PDXL". ２ The XRD peaks due to the line (λ = 1.5443 Å) were removed, and the 2θ at the peak tops of the XRD peaks corresponding to the (004) and (400) planes of tetragonal zirconia and the 2θ difference were determined. (Color Tone) The color tone of the sintered body sample was measured using a method in accordance with JIS Z 8722. For the measurement, a general spectrophotometer (device name: CM-700d, manufactured by Konica Minolta) was used, and the measurement was performed against a black background using a black plate on the back. The measurement conditions are as follows.

[0124] Light source: F2 light source; Viewing angle: 10°; Measurement method: SCI. The sintered body samples used were disc-shaped, 20 mm in diameter and 1.8 mm in thickness. One surface of the sintered body sample was mirror-polished (Ra≦0.02 μm), and this surface was used as the evaluation surface for color tone evaluation. The effective area for color tone evaluation was 10 mm in diameter. (Total luminous transmittance) The total luminous transmittance of the sintered body sample was measured using a method conforming to JIS K 7361-1. Measurements were performed using a standard haze meter (device name: NDH4000, manufactured by Nippon Denshoku Co., Ltd.) equipped with a D65 light source. The sintered body samples were 0.5±0.05 mm thick, 20 mm in diameter, and both surfaces were mirror-polished to achieve a surface roughness Ra≦0.02 μm. (Ball Drop Test) A sintered body sample was ground into a disk shape with a diameter of 36 mm and a thickness of 0.5 mm. Both surfaces of the disk-shaped sintered body sample (the 36 mm diameter surface; the main surface) were mirror-polished in the following order: with an abrasive cloth, with a diamond slurry having an average particle size of 3 μm, and with colloidal silica having a particle size of 0.03 μm. A measurement sample was obtained.

[0125] Schematic diagrams of the ball drop test are shown in Figures 1 to 3. After mending tape 2 (thickness: 0.05 mm) was applied to one main surface of measurement sample 1, the measurement sample 1 was placed on a 10 mm thick carbide plate 3 (MAST-FB10, Takeuchi Mold Materials Research Institute, HRA: 93.5) so that the surface with the mending tape 2 contacted the carbide plate 3. The end of the measurement sample 1 was attached to the carbide plate 3 with mending tape 2, and the measurement sample 1 was fixed on the carbide plate 3. The carbide plate 3 with the measurement sample 1 attached was placed so that a steel ball 4 (material: bearing steel SUJ2) would fall near the center of the measurement sample 1 after it was fixed to the carbide plate 3, and a transparent PVC pipe 5 (Φ30 mm) was fixed with a clamp 6. The transparent PVC pipe 5 was fixed perpendicular to the carbide plate 3 using a level.

[0126] The steel ball 4 was then allowed to free fall from a height of 100 cm through the inside of the transparent PVC pipe 5. The steel ball 4 was initially positioned by inserting an iron bar 7 horizontally into a hole 8 provided in the transparent PVC pipe 5 at a position 100 cm above the top surface of the measurement sample 1, with the steel ball 4 resting on the iron bar 7. The iron bar 7 was then pulled out, allowing the steel ball 4 to free fall. The steel ball 4 was allowed to free fall so as not to come into contact with the inner wall of the transparent PVC pipe 5 during its fall. To prevent the steel ball 4 from bouncing off or falling again and contacting the measurement sample 1 after the free fall, a hole 10 for inserting an iron bar 9 (Φ5 mm, 4 cm) was drilled in the transparent PVC pipe 5 at a height of approximately 5 cm above the top surface of the measurement sample 1. When the rebounded steel ball 4 reached a height of 5 cm or more, the iron bar 9 was inserted into the hole 10, and the free fall of the re-dropped steel ball 4 was stopped by the iron bar 9.

[0127] If no fracture was confirmed by the ball drop test, the test was repeated in the following order: three times with a 25 g steel ball, three times with a 50 g steel ball, and three times with a 95 g steel ball.

[0128] Example 1 A hydrated zirconia sol was obtained by hydrolyzing an aqueous solution of zirconium oxychloride. Yttrium chloride was added to and mixed with hydrated zirconium so that the yttrium concentration was 3.0 mol%, and the mixture was calcined in an air atmosphere at 1,150°C for 2 hours to obtain a calcined yttrium-stabilized zirconia powder.

[0129] The obtained yttrium-stabilized zirconia calcined powder was mixed with niobium oxide (Fujifilm Wako Pure Chemical Industries, Ltd.), manganese tetraoxide (Brownox, Tosoh), and alumina (AKP30, Sumitomo Chemical Co., Ltd.) to obtain a mixed powder with a niobium content of 2.0% by mass, a manganese content of 0.5% by mass, and an alumina content of 10.0% by mass. Pure water was added to the obtained mixed powder to obtain a mixed slurry. The mixed slurry was pulverized in a ball mill using 2 mm diameter zirconia balls as a milling medium to obtain a pulverized slurry with D10 and D90 values ​​shown in Table 1. The obtained pulverized slurry was dried at 110°C in an air atmosphere, and then coarse particles having an agglomeration diameter exceeding 180 µm were removed by sieving, thereby obtaining an yttrium-stabilized zirconia powder containing niobium, manganese, and alumina, with a niobium content of 2.0 mass%, a manganese content of 0.5 mass%, an alumina content of 10 mass%, and an yttrium content of 3.0 mol%.

[0130] Example 2 A yttrium-stabilized zirconia powder containing niobium, manganese, and alumina was obtained in the same manner as in Example 1, except that trimanganese tetroxide was mixed so that the manganese content was 1.0 mass%. The niobium content was 2.0 mass%, the manganese content was 1.0 mass%, the alumina content was 10 mass%, and the yttrium content was 3.0 mol%.

[0131] Example 3 A yttrium-stabilized zirconia powder containing niobium, manganese, and alumina, having a niobium content of 1.5% by mass, a manganese content of 1.5% by mass, an alumina content of 10% by mass, and an yttrium content of 3.0 mol%, was obtained in the same manner as in Example 1, except that niobium oxide and trimanganese tetroxide were mixed so that the niobium content was 1.5% by mass and the manganese content was 1.5% by mass.

[0132] Example 4 A calcined yttrium-stabilized zirconia powder was obtained in the same manner as in Example 1. Meanwhile, erbium chloride was added to and mixed with hydrated zirconium so that the erbium content was 3.2 mol %, and the mixture was calcined in an air atmosphere at 1,150° C. for 2 hours to obtain a calcined erbium-stabilized zirconia powder.

[0133] A mixed powder of yttrium-stabilized zirconia and erbium-stabilized zirconia containing niobium, manganese, and alumina, having a niobium content of 1.5 mass%, a manganese content of 1.5 mass%, a alumina content of 10 mass%, a yttrium content of 1.5 mol%, and an erbium content of 1.6 mol%, was obtained in the same manner as in Example 1, except that the obtained yttrium-stabilized zirconia calcined powder, erbia-stabilized zirconia calcined powder, niobium oxide, trimanganese tetroxide, and alumina were mixed so that the yttrium content was 1.5 mol%, the erbium content was 1.6 mol%, the niobium content was 1.5 mass%, the manganese content was 1.5 mass%, and the alumina content was 10.0 mass%.

[0134] Example 5 A calcined powder of yttrium-stabilized zirconia was obtained in the same manner as in Example 1.

[0135] The obtained yttrium-stabilized zirconia calcined powder, niobium oxide, manganese oxide, alumina, iron oxide (FeO), and manganese tetraoxide were mixed together so that the niobium content was 2.0 mass%, the manganese content was 0.95 mass%, the alumina content was 10.0 mass%, the iron content was 0.27 mass%, and the cobalt content was 0.33 mass%. ２ O ３ , manufactured by Kanto Chemical Co., Ltd.) and cobalt oxide (Co ３ O ４ A powder made of yttrium-stabilized zirconia containing niobium, manganese, alumina, iron, and cobalt, having a niobium content of 2.0 mass%, a manganese content of 0.95 mass%, alumina content of 10 mass%, iron content of 0.27 mass%, cobalt content of 0.33 mass%, and yttrium content of 3.0 mol%, was obtained in the same manner as in Example 1, except that yttrium-stabilized zirconia (manufactured by CoreMax Corporation) was mixed.

[0136] Examples 6 to 8 Powders having the compositions shown in Table 1 were obtained in the same manner as in Example 5, except that niobium oxide, manganese oxide, iron oxide and cobalt oxide were mixed to obtain the compositions shown in Table 1.

[0137] Comparative Example 1 A niobium- and alumina-containing yttrium-stabilized zirconia powder having a niobium content of 2.0 mass%, an alumina content of 10 mass%, and an yttrium content of 3.0 mol% was obtained in the same manner as in Example 1, except that trimanganese tetroxide was not mixed.

[0138] Comparative Example 2 A manganese- and alumina-containing yttrium-stabilized zirconia powder containing 0.5 mass % manganese, 10 mass % alumina, and 3.0 mol % yttrium was obtained in the same manner as in Example 1, except that niobium oxide was not mixed.

[0139] Comparative Example 3 A powder of this comparative example was obtained, which contained 2.0 mass % niobium, 0.95 mass % manganese, 10 mass % alumina, 0.27 mass % iron, and 0.33 mass % cobalt and was composed of zirconia stabilized with 3.0 mol % yttrium, under the same conditions as in Example 5, except that the mixed slurry was pulverized using a ball mill using zirconia balls with a diameter of 10 mm as a milling medium so that the D10 and D90 values ​​would be as shown in Table 1.

[0140] Comparative Example 4 A powder of this comparative example was obtained under the same conditions as in Example 7, consisting of zirconia stabilized with 3.0 mo of yttrium, containing 2.0 mass % niobium, 1.5 mass % manganese, 10 mass % lumina, 0.5 mass % iron, and 0.33 mass % cobalt, except that the mixed slurry was ground in a ball mill using zirconia balls with a diameter of 2 mm as grinding media so that the D10 and D90 in the cumulative particle size distribution of the powder would have the values ​​shown in Table 1.

[0141] The evaluation results of the powders of these Examples and Comparative Examples are shown in Table 1.

[0142]

[0143] (Preparation of Sintered Body) Example 9 The powder of Example 1 was subjected to a mold press at a pressure of 50 MPa and a cold isostatic press (CIP) at a pressure of 196 MPa to form a compact. The obtained compact was sintered at atmospheric pressure at 1350°C to obtain a sintered body of this example, which is zirconia containing 2.0 mass% niobium, 0.5 mass% manganese, and 10 mass% alumina and stabilized with 3.0 mol% yttrium. The sintering conditions are as follows:

[0144] Heating rate: 100°C / h Sintering temperature: 1350°C Holding time at sintering temperature: 2 hours Heating rate: 200°C / h Examples 10 to 16 and Comparative Examples 5 to 8 Sintered bodies of each Example or Comparative Example were obtained in the same manner as in Example 9, except that the powder obtained in each Example or Comparative Example was used and the sintering temperature shown in Table 2 was used.

[0145]

[0146] Table 3 shows the evaluation results of the sintered bodies of Examples 9 to 16 and Comparative Examples 5 to 8.

[0147]

[0148] In Table 3, samples that did not break in the ball drop test are marked with "O", samples that broke are marked with "X", and the number of times the steel ball was dropped when the break occurred is written in parentheses.

[0149] The sintered bodies obtained from the zirconia powders of the Examples all contained a stabilizing element, manganese, niobium, and alumina, and had a Dt of 25 nm or more and 100 nm or less. These sintered bodies were not broken even when a 90 g steel ball was dropped on them three times, demonstrating high impact resistance, and all had a total light transmittance of 0%, demonstrating high shielding efficiency.

[0150] The sintered body of Comparative Example 5, which did not contain manganese, was white and had a total light transmittance of 13%.

[0151] The sintered body of Comparative Example 6, which did not contain niobium, had a 2θ difference of less than 1.55°, and in a ball drop test, it was confirmed that cracks occurred when a 25 g steel ball was dropped on it three times.

[0152] The sintered body of Comparative Example 7 obtained from the powder of Comparative Example 3 having a D90 of 1.5 μm or more and the sintered body of Comparative Example 8 obtained from the powder of Comparative Example 4 having a D10 of 0.15 μm or less both had a crystallite diameter Dt of less than 25 nm.

[0153] The sintered body of Comparative Example 7 cracked when a 25 g steel ball was dropped on it once in a ball drop test, and the sintered body of Comparative Example 8 cracked when a 25 g steel ball was dropped on it three times in a ball drop test, confirming that both had insufficient impact resistance.

[0154] Example 17: A hydrated zirconia sol was obtained by hydrolyzing an aqueous zirconium oxychloride solution. Yttrium chloride and neodymium chloride were added to and mixed with the hydrated zirconium oxychloride to give an yttrium concentration of 2.99 mol% and a neodymium concentration of 0.44 mol%, respectively, and the mixture was calcined in an air atmosphere at 1,150°C for 2 hours to give a calcined yttrium- and neodymium-stabilized zirconia powder.

[0155] An yttrium- and neodymium-stabilized zirconia powder containing niobium, manganese, alumina, iron, and cobalt, having a niobium content of 1.8 mass%, a manganese content of 1.3 mass%, alumina content of 10 mass%, an iron content of 0.15 mass%, a cobalt content of 0.3 mass%, a yttrium content of 2.99 mol%, and a neodymium content of 0.44 mol%, was obtained in the same manner as in Example 1, except that the obtained yttrium- and neodymium-stabilized zirconia calcined powder, niobium oxide, manganese oxide, alumina, iron oxide, and cobalt oxide were mixed together so that the niobium content was 1.8 mass%, the manganese content was 1.3 mass%, the alumina content was 10 mass%, the iron content was 0.15 mass%, and the cobalt content was 0.3 mass%.

[0156] Example 18 An yttrium- and neodymium-stabilized zirconia powder having a niobium content of 2.0 mass%, manganese content of 1.3 mass%, alumina content of 10 mass%, iron content of 0.15 mass%, cobalt content of 0.3 mass%, yttrium content of 2.99 mol%, and neodymium content of 0.35 mol% was obtained in the same manner as in Example 17, except that neodymium chloride was added and mixed so that the neodymium content was 0.35 mol%, and niobium oxide was mixed so that the niobium content was 2.0 mass%.

[0157] Example 19 A yttrium- and neodymium-stabilized zirconia powder containing niobium, manganese, alumina, iron, and cobalt was obtained in the same manner as in Example 18, except that niobium oxide was mixed so that the niobium content was 1.8% by mass. The niobium content was 1.8% by mass, the manganese content was 1.3% by mass, the alumina content was 10% by mass, the iron content was 0.15% by mass, the cobalt content was 0.3% by mass, the yttrium content was 2.99 mol%, and the neodymium content was 0.35 mol%.

[0158] Example 20 A yttrium- and neodymium-stabilized zirconia powder containing niobium, manganese, alumina, iron, and cobalt was obtained in the same manner as in Example 18, except that niobium oxide was mixed so that the niobium content was 1.6% by mass. The niobium content was 1.6% by mass, the manganese content was 1.3% by mass, the alumina content was 10% by mass, the iron content was 0.15% by mass, the cobalt content was 0.3% by mass, the yttrium content was 2.99 mol%, and the neodymium content was 0.35 mol%.

[0159] Example 21 A yttrium- and neodymium-stabilized zirconia powder containing niobium, manganese, alumina, iron, and cobalt was obtained, having a niobium content of 1.6 mass%, a manganese content of 1.3 mass%, alumina content of 10 mass%, iron content of 0.15 mass%, cobalt content of 0.3 mass%, yttrium content of 2.99 mol%, and neodymium content of 0.26 mol%, in the same manner as in Example 20, except that neodymium oxide was mixed so that the neodymium content was 0.26 mol%.

[0160] Example 22 A calcined powder of yttrium- and lanthanum-stabilized zirconia was obtained in the same manner as in Example 17, except that lanthanum chloride was used instead of neodymium chloride and that lanthanum chloride was mixed so that the lanthanum content was 0.27 mol %. An yttrium- and lanthanum-stabilized zirconia powder containing niobium, manganese, alumina, iron, and cobalt, having a niobium content of 1.6 mass%, a manganese content of 1.3 mass%, alumina content of 10 mass%, iron content of 0.15 mass%, cobalt content of 0.3 mass%, yttrium content of 2.99 mol%, and lanthanum content of 0.26 mol%, was obtained in the same manner as in Example 17, except that the obtained yttrium- and lanthanum-stabilized zirconia calcined powder, niobium oxide, manganese oxide, alumina, iron oxide, and cobalt oxide were mixed so that the niobium content was 1.6 mass%, the manganese content was 1.3 mass%, the alumina content was 10 mass%, the iron content was 0.15 mass%, and the cobalt content was 0.3 mass%.

[0161] Example 23 A calcined powder of yttrium-, neodymium-, and lanthanum-stabilized zirconia was obtained in the same manner as in Example 17, except that yttrium chloride, neodymium chloride, and lanthanum chloride were added to and mixed with hydrated zirconium so that the yttrium concentration was 2.99 mol %, the neodymium concentration was 0.09 mol %, and the lanthanum concentration was 0.14 mol %. Furthermore, a yttrium-, neodymium-, and lanthanum-stabilized zirconia powder containing niobium, manganese, alumina, and iron was obtained in the same manner as in Example 17, except that the obtained yttrium-, neodymium-, and lanthanum-stabilized zirconia calcined powder, niobium oxide, manganese oxide, alumina, and iron oxide were mixed so that the niobium content was 1.5% by mass, the alumina content was 15% by mass, the manganese content was 1.4% by mass, and the iron content was 0.02% by mass. The obtained yttrium-, neodymium-, and lanthanum-stabilized zirconia powder contained niobium, manganese, alumina, and iron, and the resulting yttrium-, neodymium-, and lanthanum-stabilized zirconia powder had a niobium content of 1.5% by mass, a manganese content of 1.4% by mass, alumina content of 15% by mass, iron content of 0.02% by mass, yttrium content of 2.99 mol%, neodymium content of 0.09 mol%, and lanthanum content of 0.17 mol%.

[0162] The compositions and physical properties of the powders of these Examples and Comparative Examples are shown in Table 4.

[0163]

[0164] (Preparation of sintered bodies) Examples 24 to 30 Sintered bodies of each example were obtained in the same manner as in Example 9, except that the powders obtained in Examples 17 to 23 were used and the sintering temperatures were set to the temperatures shown in Table 5.

[0165]

[0166] Table 6 shows the evaluation results of the sintered bodies of Examples 24 to 30.

[0167]

[0168] As shown in Tables 4 to 6, the zirconia powders of Examples 17 to 23, which contained a stabilizing element, manganese, niobium, and alumina and had a D90 of 1.5 μm or less and a D10 of 0.15 μm or more, were used to obtain the zirconia sintered bodies of Examples 24 to 30, which contained a stabilizing element, manganese, niobium, and alumina and had a crystallite diameter Dt of 25 nm to 100 nm. These sintered bodies were confirmed to have high impact resistance, with no breakage even when a 25 g to 90 g steel ball was dropped on them three times. Furthermore, the total light transmittance was 0%, confirming a high shielding factor.

[0169] The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2024-69536, filed on April 23, 2024, are hereby incorporated by reference as the disclosure of the specification of the present disclosure.

[0170] 1... Measurement sample 2... Mending tape 3... Carbide plate 4... Steel ball 5... Transparent PVC pipe 6... Clamp 7... Iron bar 8... Hole

Claims

1. A zirconia sintered body containing a stabilizing element, niobium, manganese, and alumina, wherein the crystallite diameter calculated from the XRD peak assigned to the (111) plane of tetragonal zirconia is 25 nm or more and 100 nm or less.

2. The zirconia sintered body according to claim 1, wherein the stabilizing element comprises one or more elements selected from the group consisting of calcium, yttrium, lanthanum, neodymium, gadolinium, erbium and ytterbium, and the content of the stabilizer is 2.0 mol % or more and 5.5 mol % or less.

3. A zirconia sintered body according to claim 1 or 2, wherein the niobium content is 0.1 mass % or more and 3.0 mass % or less.

4. A zirconia sintered body according to any one of claims 1 to 3, wherein the manganese content is 0.5 mass % or more and 2.0 mass % or less.

5. A zirconia sintered body according to any one of claims 1 to 4, wherein the alumina content is more than 0 mass% and not more than 30 mass%.

6. A zirconia sintered body according to any one of claims 1 to 5, wherein the difference in 2θ of the peak top attributable to the (400) plane of tetragonal zirconia from the 2θ of the peak top attributable to the (004) plane of tetragonal zirconia is 1.55° or more.

7. Lightness L ＊ The zirconia sintered body according to any one of claims 1 to 6, wherein the zirconia sintered body has a molecular weight of 40 or more and 65 or less.

8. A zirconia sintered body according to any one of claims 1 to 7, having a total light transmittance of 0.1% or less at a thickness of 0.5 mm.

9. A zirconia powder containing a stabilizing element, niobium, manganese, and alumina, wherein the content of the stabilizing element is 2.0 mol% or more and 5.5 mol% or less, the niobium content is 0.1 mass% or more and 3.0 mass% or less, the manganese content is 0.5 mass% or more and 2.0 mass% or less, and the alumina content is more than 0 mass% and 30 mass% or less, and the 10% particle size in the cumulative particle size distribution of the powder is 0.15 μm or more and 0.5 μm or less, and the 90% particle size is 0.5 μm or more and 1.5 μm or less.

10. BET specific surface area is 8.0 m ２ / g or more 12m ２ The zirconia powder according to claim 9, wherein the zirconia powder has a molecular weight of 1 / g or less.

11. A member comprising the zirconia sintered body according to any one of claims 1 to 8.

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