sintered body

Abstract

To provide a zirconia sintered body that has high impact resistance even in a thin shape having a thickness of 0.5 mm or less, and also has high light-shielding property such that a member serving as a substrate is not visible therethrough.SOLUTION: A zirconia sintered body comprising a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, wherein a crystallite diameter calculated from an XRD peak attributed to the (111) plane of tetragonal zirconia is 25 nm or more and 100 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

[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 and wearable devices, such as smartphones and smartwatches, they must be thin to reduce weight. Therefore, they require high strength and impact resistance to 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, 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-54780 [Patent Document 2] Japanese Patent Application Publication No. 2020-180048 Summary of the Invention [Problem to be solved by the invention]

[0005] The composite plate of Patent Document 1 requires lamination of zirconia-matrix ceramic members and resin materials, resulting in a complex manufacturing process. Therefore, a material that exhibits high impact resistance even in a thin shape made solely of 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 agent 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 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 also has light-blocking properties that prevent the underlying material from showing through. [Means for solving the problem]

[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, alumina, and iron, cobalt, and zinc as pigment components, 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 [1], characterized in that at least a part of the pigment component forms a spinel-type metal oxide. [3] The zirconia sintered body according to [1] or [2], wherein the stabilizing element contains at least one 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. [4] The zirconia sintered body according to any one of [1] to [3], wherein the niobium content is 0.1% by mass or more and 3.0% by mass or less. [5] The zirconia sintered body according to any one of [1] to [4], wherein the alumina content is more than 0 mass% and 30 mass% or less. [6] The zirconia sintered body according to any one of [1] to [5], wherein the iron content is 0.1% by mass or more and 5% by mass or less, the cobalt content is 0.1% by mass or more and 3% by mass or less, and the zinc content is 0.05% by mass or more and 1% by mass or less, calculated as oxides. [7] The zirconia sintered body according to any one of [1] to [6], 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 1.54° or more. [8] Lightness L * The zirconia sintered body according to any one of [1] to [7], wherein the value of [σ] is 40 or more and 65 or less. [9] The zirconia sintered body according to any one of [1] to [8], which has a total light transmittance of 0.1% or less at a thickness of 0.5 mm.

[10] A zirconia powder containing a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, wherein the content of the stabilizer is 2.0 mol% or more and 5.5 mol% or less, the content of niobium is 0.1 mass% or more and 3.0 mass% or less, the content of alumina is more than 0 mass% and 30 mass% or less, and the BET specific surface area is 5.0 m 2 / g or more 17m 2 / g or less of zirconia powder.

[11] The zirconia powder according to

[10] , wherein the pigment component is contained as a spinel-type metal oxide containing iron, cobalt, and zinc.

[12] Zirconia powder according to

[10] or

[11] , having an iron content of 0.1% by mass or more and 5% by mass or less, a cobalt content of 0.1% by mass or more and 3% by mass or less, and a zinc content of 0.05% by mass or more and 1% by mass or less, calculated as oxides.

[13] Zirconia powder according to any one of

[10] to

[12] , wherein the 10% particle size 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 size D90 is 0.5 μm or more and 1.3 μm or less.

[14] A member comprising the zirconia sintered body according to any one of [1] to [9]. [Brief explanation of the drawings]

[0008] [Figure 1] Schematic diagram of the ball drop test device [Figure 2] Schematic diagram of a sample for a drop ball test [Figure 3] Schematic diagram showing the ball drop test [Figure 4A] Appearance photograph of the zirconia sintered body of Comparative Example 4 [Figure 4B] Photograph of the appearance of the zirconia sintered body of Comparative Example 4 (light transmission through the sintered body) [Figure 5] Photograph of the appearance of the zirconia sintered body of Example 9 (the sintered body does not transmit light) DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes an example of an embodiment of the present disclosure. The present disclosure includes any combination of the configurations and parameters disclosed herein, and also includes any combination of upper and lower limits of the values ​​disclosed herein. (sintered body) The present embodiment is a zirconia sintered body containing a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, and having a crystallite diameter of 25 nm to 100 nm, as calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia (hereinafter also referred to as the "sintered body of the present embodiment"). Furthermore, the sintered body of the present embodiment is a stabilizing element-containing zirconia sintered body containing niobium, alumina, and iron, cobalt, and zinc as pigment components, and having a crystallite diameter of 25 nm to 100 nm, as calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia. Among the additive elements added to conventionally known zirconia sintered bodies, the zirconia sintered body contains niobium, alumina, and additive components containing iron, cobalt, and zinc as pigment components. By satisfying this configuration, the zirconia sintered body has high impact resistance and opacity, preventing the base material from showing through. 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 the 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 preferably 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, at least one of yttrium and erbium, or yttrium.

[0010] The sintered body 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 other than yttrium is preferred (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 lanthanum, erbium, or neodymium, and even more preferably erbium.

[0011] 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.) may be any amount that stabilizes the zirconia crystal phase. The stabilizing element amount may be greater than 0 mol%, 1.5 mol% or more, 2.0 mol% or more, or 2.5 mol% or more, and less than 8.5 mol%, 5.5 mol% or less, 4.0 mol% or less, 3.4 mol% or less, or 3.2 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 stabilizing element amount of the sintered body of this embodiment is preferably greater than 0 mol% and less than 8.5 mol%, 1.5 mol% to 5.5 mol%, 2.0 mol% to 4.0 mol%, 2.5 mol% to 4.0 mol%, or 2.5 mol% to 3.2 mol%.

[0012] When the sintered body contains a sub-stabilizing element, 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.

[0013] 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. The amount of yttrium is more than 0 mol%, 1.0 mol% or more, 1.5 mol% or more, 2.0 mol% or more, or 2.5 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 more than 0 mol% but less than 4.0 mol%, 1.0 mol% or more to 3.5 mol%, 1.5 mol% or more to 3.0 mol% or less, or 2.5 mol% or more to 3.0 mol% or less is preferred.

[0014] When the sub-stabilizing element is erbium, the amount of erbium may be greater than 0 mol%, 0.03 mol% or greater, or 1.0 mol% or greater, 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 greater than 0 mol% and less than 4.0 mol%, 0.01 mol% or greater and 3.0 mol% or less, 0.03 mol% or greater and 2.0 mol% or less, or 1.0 mol% or greater and 1.9 mol% or less.

[0015] 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, 0.2 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.

[0016] When the secondary stabilizing element is lanthanum, the amount of lanthanum may be greater 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 greater 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.

[0017] 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.

[0018] The sintered body of this embodiment contains niobium (Nb). The inclusion of niobium is expected to improve the impact resistance and light-shielding properties of the sintered body. The niobium content (hereinafter also referred to as the "niobium amount") may be greater than 0 mass%, greater than 0.1 mass%, 0.5 mass% or more, or 1.0 mass% or more, and may be 3.0 mass% or less, 2.5 mass% or less, or 2.0 mass% or less. The niobium content may be greater than 0 mass% or 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. The niobium contained in the sintered body of this embodiment may be in any form. For example, niobium may be present in the sintered body as niobium oxide (NbO) particles, i.e., second-phase particles, without forming a solid solution in the sintered body. Alternatively, some or all of the niobium may be present in the sintered body as a solid solution in zirconia, or may react with an oxide other than zirconia in the sintered body to form a composite oxide.

[0019] In this embodiment, the content of niobium is the mass ratio of niobium to the total amount of zirconia, stabilizing element, niobium, aluminum, and pigment component.

[0020] The powder of this embodiment contains alumina (Al2O3). The alumina content (hereinafter also referred to as "alumina amount") can be more than 0% by mass and less than 30% by mass. By including alumina (i.e., an alumina amount greater than 0% by mass), a dense sintered body can be easily obtained even at relatively low temperatures. To improve shielding properties, the alumina amount is preferably 0% by mass or more, more than 0% by mass, 0.005% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.25% by mass or more, 0.5% by mass or more, or 1% by mass or more. On the other hand, to improve mechanical properties such as static strength, the alumina amount may be less than 30% by mass, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 2% by mass or less. The alumina amount of the sintered body of this embodiment can be more than 0% by mass and less than 20% by mass, or 0.1% by mass or more and less than 10% by mass.

[0021] 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.

[0022] The sintered body of this embodiment contains iron, cobalt, and zinc as pigment components. The pigment components contained in the sintered body refer to components (elements) that have the function of coloring the sintered body. This allows the sintered body to exhibit any color tone different from the original color tone of zirconia. By containing iron, cobalt, and zinc, among the pigment components, in particular, the light-blocking properties of the sintered body are improved, and a dense sintered body is easily obtained even when sintered at a relatively low temperature. Note that the above-mentioned stabilizing elements may also include elements that have the function of coloring the sintered body. However, for convenience, in calculating the composition in this embodiment, these stabilizing elements are not included in the pigment components and are calculated as stabilizing elements. Examples of stabilizing elements that have the function of coloring the sintered body include neodymium, cerium, and erbium.

[0023] The iron, cobalt, and zinc contents of the sintered body of this embodiment (hereinafter, the respective contents may also be referred to as "iron amount," "cobalt amount," and "zinc amount") are preferably as follows, respectively.

[0024] The iron content may be 0.10% by mass or more, preferably 0.20% by mass or more, 0.30% by mass or more, or 0.50% by mass or more, and may be 5.0% by mass or less, preferably 4.5% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. The iron content may be 0.10% by mass or more and 5.0% by mass or less, and more preferably 0.20% by mass or more and 4.5% by mass or less, 0.30% by mass or more and 3.0% by mass or less, or 0.50% by mass or more and 2.0% by mass or less.

[0025] The cobalt content is 0.10% by mass or more, preferably 0.20% by mass or more or 0.25% by mass or more, and 3.0% by mass or less, preferably 2.0% by mass or less, 1.5% by mass or less, or 1.0% by mass or less. The cobalt content is 0.10% by mass or more and 3.0% by mass or less, and more preferably 0.20% by mass or more and 2.0% by mass or less, 0.25% by mass or more and 1.5% by mass or less, or 0.25% by mass or more and 1.0% by mass or less.

[0026] The zinc content is 0.05% by mass or more, preferably 0.10% by mass or more, and 1.0% by mass or less, preferably 0.70% by mass or less or 0.50% by mass or less. Furthermore, the zinc content is 0.05% by mass or more and 1.0% by mass or less, preferably 0.10% by mass or more and 0.70% by mass or less, more preferably more than 0.10% by mass and 0.50% by mass or less.

[0027] The sintered body of this embodiment may further contain pigment components other than the above-mentioned iron, cobalt, and zinc (hereinafter also referred to as "other pigment component amounts"). Examples of other pigment components include compounds containing metal elements, and transition metal elements and compounds containing them. Specific examples of pigment components other than iron, cobalt, and zinc include one or more elements selected from the group consisting of vanadium (V), manganese (Mn), nickel (Ni), and copper (Cu), as well as compounds containing one or more of these elements, and oxides containing one or more of these elements. The sintered body of this embodiment may contain chromium (Cr) as a pigment component, but preferably does not contain chromium from an environmental perspective.

[0028] As the pigment component, for example, by sintering a mixture of zirconia powder and pigment powder, 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.

[0029] Preferably, a portion or all of the pigment component in the sintered body of this embodiment forms a spinel-type metal oxide. Having a portion or all of the pigment component form a spinel-type metal oxide improves shielding properties and stabilizes color tone. The spinel-type metal oxide is preferably represented by AB2O4, where A and B are each at least one element selected from the group consisting of Mg, Ca, Sr, Y, La, Gd, V, Mn, Fe, Co, Ni, Cu, Zn, and Al. More preferably, the spinel-type metal oxide is represented by AB2O4, where A and B are each at least one element selected from the group consisting of Mg, Ca, Sr, Y, Gd, Fe, Co, Ni, Zn, and Al. The spinel-type metal oxide that can be contained in the sintered body of this embodiment, when represented by AB2O4, may contain multiple elements in the A site and the B site. When multiple elements are contained in the A site and the B site, the composition ratio of each element in the A site and the B site may be arbitrary. Specific examples of spinel-type metal oxides include one or more selected from the group consisting of CoAl2O4, ZnFe2O4, MgFe2O4, CoFe2O4, NiFe2O4, Co(Fe,Al)2O4, and (Co,Zn)(Fe,Al)2O4.

[0030] In this embodiment, whether the pigment component forms a spinel-type metal oxide can be confirmed by checking the powder X-ray diffraction (hereinafter also referred to as XRD) pattern of the zirconia powder of this embodiment to see if it has a peak at 2θ=36.3±0.5, which corresponds to the (311) plane of the spinel-type metal oxide.

[0031] In this embodiment, the X-ray diffraction pattern of the sintered body when confirming whether the pigment component forms a spinel-type metal oxide can be measured using a general X-ray diffractometer for crystallinity analysis (for example, device name: Ultima IV, manufactured by RIGAKU Corporation).

[0032] The measurement conditions are as follows:

[0033] Radiation source: CuKα radiation (λ=0.15418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=32° to 40° Goniometer: Radius 185mm A disk-shaped sintered body with a diameter of 20 mm and a thickness of 1.0 mm is used as the measurement sample, and the surface to be evaluated is mirror-polished (surface roughness Ra≦0.02 μm), and the polished surface is irradiated with X-rays for measurement.

[0034] The content of other pigment components in the sintered body of this embodiment (hereinafter also referred to as the "amount of other pigment components"; if the other pigment component is manganese, it is also referred to as the "amount of manganese" or the like) is any amount within the range in which the effects of the present invention are exhibited, but is preferably greater 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 amount of other pigment components 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.

[0035] The sintered body of this embodiment may contain one or more additive components selected from the group consisting of silica (SiO2), titania (TiO2), and gallium oxide (Ga2O3). By including such additives, the sintered body can have desired mechanical properties. The content of the additive component (hereinafter also referred to as "additive component amount") is 0% by mass or more, 0.5% by mass or more, or 1.0% by mass or more, and 5.0% by mass or less, or 2.5% by mass or less. The amount of the additive component can be, for example, 0% by mass or more to 5.0% by mass or 1.0% by mass or more to 2.5% by mass or less.

[0036] In the sintered body of the present embodiment, the niobium, alumina, 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.

[0037] In this embodiment, the niobium amount, alumina amount, pigment component amount, other pigment component amount, and additive component amount are the mass proportions (mass %) of niobium, alumina, pigment component, other pigment component amount, and additive component amount, calculated as oxide, relative to the total mass of zirconia and metal elements calculated as oxide.

[0038] In this embodiment, examples of oxide equivalents include calcium as CaO, magnesium as MgO, scandium as Sc2O3, yttrium as Y2O3, lanthanum as La2O3, neodymium as Nd2O3, cerium as CeO2, gadolinium as Gd2O3, erbium as Er2O3, ytterbium as Yb2O3, niobium as Nb2O5, aluminum as Al2O3, silicon as SiO2, gallium as Ga2O3, vanadium as V2O5, chromium as Cr2O3, iron as Fe2O3, cobalt as Co3O4, manganese as Mn3O4, nickel as NiO, copper as CuO, and zinc as ZnO.

[0039] The sintered body of this embodiment may contain inevitable impurities such as hafnia (HfO2). In this embodiment, the content of each component of the sintered body may be calculated by regarding hafnia as zirconia (ZrO2).

[0040] For example, the composition (content of each component) of the zirconia sintered body (the same applies to the powder described below) of the present embodiment, which contains alumina and niobium, as well as iron, cobalt, and zinc as pigment components, and also contains gadolinium and yttrium as stabilizing elements, can be determined as follows.

[0041] Pigment component amount [mass%] = {(Fe2O3 + Co3O4 + ZnO) / (Gd2O3+Y2O3+ZrO2+Nb2O5+Mn3O4+Al2O3+Fe2O3 +Co3O4+ZnO)}×100 Iron amount [mass%]={Fe2O3 / (Gd2O3+Y2O3+ZrO2 +Nb2O5+Al2O3+Fe2O3+Co3O4+ZnO)}×100 Cobalt content [mass%] = {Co3O4 / (Gd2O3 + Y2O3 + ZrO2 +Nb2O5+Al2O3+Fe2O3+Co3O4+ZnO)}×100 Zinc content [mass%] = {ZnO / (Gd2O3 + Y2O3 + ZrO2 +Nb2O5+Al2O3+Fe2O3+Co3O4+ZnO)}×100 Alumina content [mass%] = {Al2O3 / (Gd2O3 + Y2O3 + ZrO2 +Nb2O5+Al2O3+Fe2O3+Co3O4+ZnO)}×100 Niobium amount [mass%]={Nb2O5 / (Gd2O3+Y2O3+ZrO2 +Nb2O5+Al2O3+Fe2O3+Co3O4+ZnO)}×100 Stabilizing element amount [mol%]={(Gd2O3+Y2O3) / (Gd2O3+Y2O3+ZrO2)}×100 Sub-stabilizing element amount [mol%]={(Gd2O3) / (Gd2O3+Y2O3+ZrO2)}×100 Gadolinium content [mol%] = {(Gd2O3) / (Gd2O3+Y2O3+ZrO2)}×100 Yttrium content [mol%] = {(Y2O3) / (Gd2O3+Y2O3+ZrO2)}×100 The sintered body of this embodiment has a crystallite diameter (hereinafter referred to as "D") calculated from the XRD peak attributed to the (111) plane of tetragonal zirconia. t " or simply "crystallite diameter.") 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, 30 nm or more, or 40 nm or more, and D t is preferably 90 nm or less, 85 nm or less, or 80 nm or less. t is, for example, 25 nm or more and 90 nm or less, 30 nm or more and 85 nm or less, or 40 nm or more and 80 nm or less.

[0042] 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 blocking 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 described above, and the interaction between manganese and niobium promotes the segregation of niobium in the sintered body. The promotion of niobium segregation makes it easier for the phase transformation of zirconia to occur, resulting in a zirconia sintered body with high impact resistance and high light-shielding properties, despite the presence of 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.

[0043] As will be described later, the XRD peak attributable 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 considered 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. D t can be calculated from the following formula using the XRD pattern of the zirconia sintered body.

[0044] D t =Kλ / B t cosθ t (1) In equation (1), Dt is 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-rays used in the XRD measurement (0.15418 nm), B t is the broadening (rad) of the peak assigned to the (111) plane of tetragonal zirconia, and θ t is the Bragg angle (rad) of the peak attributed to the (111) plane of tetragonal zirconia.

[0045] 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 specification, the XRD peaks attributable to the (111) plane of tetragonal zirconia and the (111) plane of cubic zirconia are not distinguished, and the overlapping peaks are treated as XRD peaks attributable to the (111) plane of tetragonal zirconia.

[0046] The crystallite diameter of the zirconia sintered body of this embodiment, calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia, can be 25 nm to 90 nm, preferably 30 nm to 85 nm, and more preferably 40 nm to 80 nm. When the crystallite diameter calculated from the XRD peak attributable to the (111) plane of tetragonal zirconia is within the above range, the impact resistance of the zirconia sintered body is improved.

[0047] In this embodiment, the X-ray diffraction pattern of the sintered body, which includes an XRD peak attributed to the (111) plane of tetragonal zirconia, can be measured using a general crystallinity analysis X-ray diffraction device (for example, device name: Ultima IV, manufactured by RIGAKU Corporation).

[0048] The measurement conditions are as follows:

[0049] Radiation source: CuKα radiation (λ=0.15418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=26° to 33° Goniometer: Radius 185mm A disk-shaped sintered body with a diameter of 20 mm and a thickness of 1.0 mm is used as the measurement sample, and the surface to be evaluated is mirror-polished (surface roughness Ra≦0.02 μm), and the polished surface is irradiated with X-rays for measurement.

[0050] In the above-described XRD pattern 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.

[0051] XRD peak corresponding to the (111) plane of monoclinic zirconia: 2θ = 31 ± 0.5° XRD peak corresponding to the (11-1) plane of monoclinic zirconia: 2θ = 28 ± 0.5° XRD peak corresponding to the (111) plane of tetragonal zirconia: 2θ=30±0.5° The patterns obtained by the above-mentioned XRD pattern measurement can be analyzed using the integrated powder X-ray analysis software "PDXL" (manufactured by Rigaku Corporation). The analysis calculates the broadening (rad) of each peak and the area intensity of each peak.

[0052] 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 is mainly composed of tetragonal crystals" 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 of the zirconia crystalline phase is tetragonal.

[0053] 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 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).

[0054] 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 tetragonal crystals (tetragonal zirconia) and the peak top of the XRD peak attributable to the (004) plane of tetragonal zirconia in the XRD pattern at the center of the sintered body (hereinafter also referred to as the "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 examples thereof include 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.

[0055] In this embodiment, the X-ray diffraction pattern including XRD peaks attributable to the tetragonal (004) plane and (400) plane of the zirconia sintered body may be measured in the same manner as in the above-described XRD measurement, except that the measurement conditions are as follows.

[0056] Radiation source: CuKα radiation (λ=0.15418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 2° / min Step width: 0.02° Measurement range: 2θ=72° to 76° Goniometer: Radius 185mm In the above-mentioned 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.

[0057] 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 pattern obtained by the above-mentioned XRD pattern measurement can be analyzed using the integrated powder X-ray analysis software "PDXL" (manufactured by Rigaku Corporation). Specifically, the "PDXL" program is used to remove the background and the XRD peaks due to CuKα2 radiation (λ = 1.5443 Å), and then the positions (°) of the peaks corresponding to the (004) and (400) planes of tetragonal zirconia are detected.

[0058] The sintered body of this embodiment is made of CIE1976(L * a * b * ) Lightness in color space L * The sintered body of this embodiment preferably has a lightness L * is preferably 35 or more, 38 or more, or 40 or more, and is preferably 60 or less, 55 or less, 50 or less, or 48 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.

[0059] The sintered body of this embodiment is CIE1976(L * a * b * ) Chromaticity in color space a * and b * is arbitrary, but a * is between -10 and 10, b * is between -10 and 10.

[0060] 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) according to the method of JIS Z 8722. * and chromaticity a * and b * The measurement conditions are as follows: Measurement may be performed using a black board as the background (so-called black background measurement).

[0061] Light source: D65 light source Viewing angle: 10° Measurement method: SCI The measurement sample is a disk-shaped sintered body with a diameter of 20 mm and a thickness of 1.8 mm, 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.

[0062] The zirconia sintered body of the present 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 impact test in which a 0.5 mm thick sintered body of the present embodiment is bonded to a 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, the sample 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 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 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.

[0063] 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.

[0064] The zirconia sintered body of the present embodiment has high light-blocking properties. For example, when the sintered body of the present embodiment and an underlying member are stacked, it is preferable that the sintered body of the present embodiment exhibits light-blocking properties that prevent the underlying member from showing through when observed in the stacking direction.

[0065] 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 in 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 indicates higher light-blocking properties. Although the total light transmittance is preferably 0%, 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%.

[0066] 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.

[0067] Measurement light source: D65 light source Sample thickness: 0.5±0.05mm Sample diameter: 20 mm Surface roughness: Ra≦0.02μm The total light transmittance means the ratio of the total intensity of diffuse transmitted light and in-line transmitted light to the intensity of incident light, and these have the following relationship:

[0068] 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 the intended purpose, such as various uses, may be used.

[0069] 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 it has 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 a sintered body of this embodiment is a zirconia powder containing a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, 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 alumina content is more than 0% and 30 mass% or less, and the BET specific surface area is 5.0 m 2 / g or more 17.0m 2 / g or less.

[0070] 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, more preferably one or more selected from the group consisting of calcium, lanthanum, yttrium, neodymium, gadolinium, erbium, and ytterbium, more preferably 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 more preferably yttrium. The powder in this embodiment may contain two or more types of stabilizing elements, in which 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 (sub-stabilizing element) other than yttrium. The sub-stabilizing element contained in the sintered body in 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.

[0071] The amount of the stabilizing element in the powder of this embodiment may be any amount that stabilizes the zirconia crystal phase. Examples of the amount of the stabilizing element include more than 0 mol%, 1.5 mol% or more, 2.0 mol% or more, or 2.5 mol% or more, and less than 8.5 mol%, 5.5 mol% or less, 4.0 mol% or less, 3.4 mol% or less, or 3.2 mol%. Further examples of the amount of the stabilizing element in the powder of this embodiment include more 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, 2.5 mol% or more and 4.0 mol% or less, or 2.5 mol% or more and 3.2 mol% or less. When the powder of this embodiment contains a sub-stabilizing element, the amount of the sub-stabilizing element in the powder 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 amount of the sub-stabilizing element is preferably greater than 0 mol% and less than 5.5 mol%, 0.05 mol% to 4.0 mol%, 0.10 mol% to 3.0 mol%, 0.20 mol% to 1.9 mol%, or 1.0 mol% to 1.9 mol%.

[0072] 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.

[0073] The amount of yttrium is greater than 0 mol%, 1.0 mol% or more, 1.5 mol% or more, 2.0 mol% or more, or 2.5 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 greater than 0 mol% and less than 4.0 mol%, 1.0 mol% or more and 3.5 mol% or less, 1.5 mol% or more and 3.0 mol% or less, or 2.5 mol% or more and 3.0 mol% or less.

[0074] When the sub-stabilizing element is erbium, the amount of erbium may be greater than 0 mol%, 0.03 mol% or greater, or 1.0 mol% or greater, 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 greater than 0 mol% and less than 4.0 mol%, 0.01 mol% or greater and 3.0 mol% or less, 0.03 mol% or greater and 2.0 mol% or less, or 1.0 mol% or greater and 1.9 mol% or less.

[0075] 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.

[0076] When the secondary stabilizing element is lanthanum, the amount of lanthanum may be greater 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 greater 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.

[0077] 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, or 1.0 mass% or more, and may be 3.0 mass% or less, 2.5 mass% or less, or 2.0 mass% or less. The niobium content may be greater than 0 mass% but 3.0 mass% or less, and preferably 1.0 mass% or more but 3.0 mass% or less, or 1.0 mass% or more but 2.5 mass% or less.

[0078] The powder of this embodiment contains alumina. The alumina amount can be more than 0% by mass and less than 30% by mass. By including alumina (i.e., by including an alumina amount greater than 0% by mass), the sintered body of this embodiment can be obtained by sintering at a lower temperature. Furthermore, by including an alumina amount less than 30% by mass, the mechanical properties of the sintered body, such as static strength, tend to be improved. The alumina amount can be more than 0% by mass and less than 30% by mass. By including alumina, a dense sintered body can be easily obtained even at a relatively low temperature. To improve shielding properties, the alumina amount is preferably 0% by mass or more, more than 0% by mass, 0.005% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.25% by mass or more, 0.5% by mass or more, or 1% by mass or more. On the other hand, to improve mechanical properties, such as static strength, the alumina amount can be less than 30% by mass, 20% by mass or less, 10% by mass or less, 5% by mass or less, or 2% by mass or less. The alumina content of the sintered body of this embodiment may be more than 0 mass % and 20 mass % or less, or 0.1 mass % or more and 10 mass % or less.

[0079] The powder of this embodiment contains iron, cobalt, and zinc as pigment components. The pigment components contained in the powder of this embodiment refer to components that have the function of coloring the sintered body. This allows the sintered body to exhibit any color tone different from the original color tone of zirconia. Among the pigment components, the inclusion of iron, cobalt, and zinc in particular improves the light-blocking properties of the sintered body and makes it easier to obtain a dense sintered body even when sintered at a relatively low temperature. Note that even if the above-mentioned stabilizing elements have the function of coloring the sintered body, they are not included in the pigment components when calculating their content, but are calculated as stabilizing elements. For example, neodymium, cerium, and erbium are elements that have the function of coloring the sintered body, but are not included in the pigment components when calculating their content, but are calculated as stabilizing elements when calculating their content.

[0080] The iron content may be 0.10% by mass or more, preferably 0.20% by mass or more, 0.30% by mass or more, or 0.50% by mass or more, and may be 5.0% by mass or less, preferably 4.5% by mass or less, 3.0% by mass or less, or 2.0% by mass or less. The iron content may be 0.10% by mass or more and 5.0% by mass or less, and more preferably 0.20% by mass or more and 4.5% by mass or less, 0.30% by mass or more and 3.0% by mass or less, or 0.50% by mass or more and 2.0% by mass or less.

[0081] The cobalt content is 0.10% by mass or more, preferably 0.20% by mass or more or 0.25% by mass or more, and 3.0% by mass or less, preferably 2.0% by mass or less, 1.5% by mass or less, or 1.0% by mass or less. The cobalt content is 0.10% by mass or more and 3.0% by mass or less, and more preferably 0.20% by mass or more and 2.0% by mass or less, 0.25% by mass or more and 1.5% by mass or less, or 0.25% by mass or more and 1.0% by mass or less.

[0082] The zinc content is 0.05% by mass or more, preferably 0.10% by mass or more, and 1.0% by mass or less, preferably 0.70% by mass or less or 0.50% by mass or less. Furthermore, the zinc content is 0.05% by mass or more and 1.0% by mass or less, preferably 0.10% by mass or more and 0.70% by mass or less, more preferably more than 0.10% by mass and 0.50% by mass or less.

[0083] The powder of this embodiment may further contain pigment components other than the above-mentioned iron, cobalt, and zinc. Examples of pigment components other than iron, cobalt, and zinc include, for example, compounds containing metal elements, and preferably transition metal elements and compounds containing them. Specific pigment components other than iron, cobalt, and zinc include, more preferably, one or more elements selected from the group consisting of vanadium, manganese, nickel, and copper, and compounds containing one or more of these, and even more preferably, oxides containing one or more of these. The sintered body of this embodiment may contain chromium as a pigment component, but preferably does not contain chromium from an environmental perspective.

[0084] The content of other pigment components in the powder of this embodiment is arbitrary, but is preferably greater 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, or 3.0% by mass or less. Furthermore, the amount of other pigment components is preferably greater than 0% by mass but less than 5.0% by mass, 0.001% by mass or more but less than 3.5% by mass, or 0.005% by mass or more but less than 3.0% by mass.

[0085] The powder of this embodiment may contain one or more additive components selected from the group consisting of silica, titania, and gallium oxide, in addition to niobium, alumina, and pigment components. By including such additives, a sintered body having desired mechanical properties can be obtained.

[0086] The powder of this embodiment may contain inevitable impurities such as hafnia, etc. In this embodiment, the content of each component of the sintered body may be calculated by regarding hafnia as zirconia.

[0087] In the powder of this embodiment, the niobium, alumina, pigment component, other pigment component, and additive component may each be contained in the powder in any form, and may be contained as at least one of a compound, a composite oxide, and an oxide, or part or all of them may be contained as a solid solution in zirconia.

[0088] The pigment component in the powder of this embodiment may partially or entirely form a spinel-type metal oxide. By partially or entirely forming the pigment component, the shielding properties are improved and the color tone tends to be stable. The spinel-type metal oxide is preferably represented by the formula AB2O4, where A and B are each at least one selected from the group consisting of Mg, Ca, Sr, Y, La, Gd, V, Mn, Fe, Co, Ni, Cu, Zn, and Al. More preferably, the spinel-type metal oxide is represented by the formula AB2O4, where A and B are each at least one selected from the group consisting of Mg, Ca, Sr, Y, Gd, Fe, Co, Ni, Zn, and Al. The spinel-type metal oxide that can be contained in the powder of this embodiment may contain multiple elements in the A site and B site when represented by the formula AB2O4. When multiple elements are contained in the A site and B site, the composition ratio of each element in the A site and the B site is optional. Specific examples of spinel-type metal oxides include one or more selected from the group consisting of CoAl2O4, ZnFe2O4, MgFe2O4, CoFe2O4, NiFe2O4, Co(Fe,Al)2O4, and (Co,Zn)(Fe,Al)2O4.

[0089] The powder of this embodiment has a BET specific surface area of ​​5.0 m 2 / g or more 17.0m 2 The powder of this embodiment has a BET specific surface area of ​​6.0 m 2 / g or more 16m 2 / g or less, 7.0m 2 / g or more 14.0m 2 / g or less, or 8.0m 2 / g or more 12.0m 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.

[0090] In this embodiment, the BET specific surface area of ​​the powder is determined in accordance with JIS R 1626-1996 by a single-point BET method using a general automatic flow-type specific surface area measuring device (e.g., FlowSorb III2305, manufactured by Shimadzu Corporation) and nitrogen (N) as the adsorbent. Prior to the measurement, the powder may be pretreated by treating it in a vacuum atmosphere at 250°C for 2 hours.

[0091] The powder of this embodiment preferably has a 10% particle size 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 size D90 of 0.50 μm or more and 1.30 μm or less in the cumulative particle size distribution of the powder. Both D10 and D90 are indicators of the secondary particle size distribution of the powder. By keeping D10 and D90 within these ranges, the stability of the tetragonal zirconia in the sintered body is controlled, and as a result, the crystallite size 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.

[0092] The powder of this embodiment may have 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. The 10% particle size 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.

[0093] The powder of this embodiment may have a D90 of 0.50 μm to 1.5 μm, 0.50 μm to 1.3 μm, 0.525 μm to 1.25 μm, 0.55 μm to 1.2 μm, or 0.55 μm to less than 1.0 μm. The 90% particle size D90 is preferably 0.50 μm or more, more preferably greater than 0.50 μm, 0.525 μm or more, or 0.55 μm or more, and more preferably 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.

[0094] In this embodiment, D10 and D90 are the general Microtrac particle size distributions. total It can be determined from the cumulative particle size distribution curve obtained by measuring in HRA mode on an instrument (for example, the MT3000II, manufactured by Microtrac-Bell). To break up agglomerations of powders such as powder granules, a slurry of the powder sample suspended in pure water may be pretreated using an ultrasonic homogenizer or the like prior to measurement. A dispersant (for example, sodium hexametaphosphate) may also be used to prepare the slurry.

[0095] The powder of this embodiment may contain a molding aid. By including the 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 the 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.).

[0096] 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 More than 1.50g / cm 3 Below that, 1.10 g / cm 3 More than 1.45g / cm 3 The following points can be mentioned. (Powder manufacturing method) Any manufacturing method can be used as long as the powder of this embodiment can be obtained. One example of a manufacturing method for the powder of this embodiment includes a manufacturing 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 form a calcined powder (hereinafter also referred to as a "powder calcination step"); and pulverizing the calcined powder, a niobium source, an alumina source, an iron source, a cobalt source, and a zinc source (hereinafter also referred to as a "pulverization step").

[0097] 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.

[0098] Any method can be used to produce a zirconia sol containing crystalline zirconia whose main phase is monoclinic zirconia, and examples thereof include at least one of hydrothermal synthesis and hydrolysis. In the hydrothermal synthesis method, a zirconia sol is obtained by mixing a zirconium salt with an alkali or the like in the presence of a solvent, and then heat-treating the resulting coprecipitate at 100 to 200°C. In the hydrolysis method, a zirconium salt is heated in the presence of a solvent, whereby the zirconium salt is hydrolyzed to produce a zirconia sol. Thus, examples of zirconia sols include those obtained by at least one of hydrothermal synthesis and hydrolysis, and preferably those obtained by hydrolysis. Examples of precursors used in the method for producing a zirconia sol include zirconium salts. 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, and zirconium oxychloride is more preferred.

[0099] The powder calcination step produces a calcined powder that is a precursor of zirconia powder. The zirconia raw material composition may contain at least one of a niobium source and an alumina source.

[0100] 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 may be 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, the stabilizing element source when the stabilizing element is yttrium or the like will also be referred to as an "yttrium source," 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 desired sintered body.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] The niobium source may be at least one of niobium oxide and a compound that serves 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 that serve as precursors of niobium oxide, and is preferably one or more selected from the group consisting of niobium oxide and the hydroxides and alkoxides of germanium that serve as precursors thereof. The content of the niobium source in the raw material composition may be equivalent to the niobium content of the target sintered body.

[0105] 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 of the target sintered body.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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 adjusted depending on the heat treatment temperature, the amount of zirconia raw material composition used, 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] The pulverization method may be any method, as long as it is at least one of wet pulverization and dry pulverization, and wet pulverization is 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, and a ball mill is preferred.

[0114] 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, an alumina source, an iron source, a cobalt source, and a zinc source. The alumina source, the iron source, the cobalt source, and the zinc source may be reacted in advance with each other to form a composite oxide.

[0115] The iron source is at least one of iron oxide and its precursor iron-containing compound, and includes one or more selected from the group consisting of iron chloride, iron oxide, and iron hydroxide, with iron oxide being preferred.

[0116] The cobalt source is at least one of iron oxide and a cobalt-containing compound that serves as a precursor thereof, and includes at least one selected from the group consisting of cobalt chloride, cobalt oxide, and cobalt hydroxide, with cobalt oxide being preferred.

[0117] The zinc source is at least one of zinc oxide and a zinc-containing compound that serves as a precursor thereof, and includes one or more selected from the group consisting of zinc chloride, zinc oxide, and zinc hydroxide, with zinc oxide being preferred.

[0118] The powder to be subjected to the pulverization step may be a mixed powder containing a pigment component in addition to the above.

[0119] 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 with 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, 5 hours to 100 hours.

[0120] 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.

[0121] To improve the workability of the powder, the manufacturing method of 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 in which the powder is mixed with a solvent. The solvent is at least one of water and alcohol, preferably water. (Method of manufacturing sintered body) The method for producing the sintered body of this embodiment is arbitrary, and an example thereof is a production method including 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 has 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 compact (pressed powder compact) and then subjected to sintering, or the compact may be calcined to form a calcined body and then subjected to sintering.

[0122] The method for producing a sintered body of this embodiment may include a step of molding the powder into a molded body (green compact) (hereinafter also referred to as a "molding step"). 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 may be, for example, one or more selected from the group consisting of acrylic resin, polyolefin resin, wax, and plasticizer. 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.).

[0123] 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 100% by mass of the molded body. By including a binder, the shape stability of the resulting molded body is improved.

[0124] 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 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. Also, any shape suitable for the purpose may be used.

[0125] The molding method may be any known molding method capable of forming 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 pressing), and even more preferably uniaxial pressing followed by cold isostatic pressing.

[0126] 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.

[0127] 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. However, examples of the conditions 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 and lower than 1100°C.

[0128] In the sintering step, the molded body or the calcined body is sintered to obtain a sintered body. Any sintering method can be used as long as it allows sintering to proceed, 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 by simply heating it without applying an external force during sintering.

[0129] The conditions for atmospheric sintering are that the holding temperature (sintering temperature) in the sintering step is 1050°C or higher and 1600°C or lower, preferably 1100°C or higher and 1550°C or lower, 1100°C or higher and 1500°C or lower, 1150°C or higher and 1500°C or lower, 1200°C or higher and 1500°C or lower, or 1250°C or higher and 1450°C or lower. Sintering temperatures within this range make it easy to obtain a sintered body with a crystallite diameter of 25 nm or higher and 100 nm or lower. The sintering temperature is preferably higher than the calcination temperature. 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 can be 5000°C / hour or less, 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 can be set appropriately depending on the amount and size of the sintered material to be sintered and the characteristics of the sintering furnace, and for example, the holding time at the above sintering temperature is 0.3 hours or more, 0.5 hours or more, or 1 hour or more, and can be 20 hours or less, 10 hours or less, or 5 hours or less, and can be 0.5 hours or more and 20 hours or less, or 0.5 hours or more and 15 hours or less.

[0130] 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. [Example]

[0131] The present disclosure will be specifically described below using examples, but the present disclosure is not limited to these examples. (BET specific surface area) The BET specific surface area of ​​the powder was measured by the single-point BET method using nitrogen (N2) as the adsorbent and a general automatic flow-type specific surface area measuring device (FlowSorb III2305, manufactured by Shimadzu Corporation) in accordance with JIS R 1626-1996. Prior to the measurement, the powder was pre-dried in vacuum at 250°C for 2 hours. (D10 and D90) Typical Microtrac particle size distribution total A cumulative particle size distribution curve was obtained by measuring using the HRA mode of an MT3000II (Microtrac-Bell). D10 and D90 were calculated from the obtained cumulative particle size distribution curve. Prior to measurement, the powder was suspended in pure water containing a dispersant (sodium hexametaphosphate) and dispersed for 10 minutes using an ultrasonic homogenizer as a pretreatment. (Crystallite diameter: Dt) An XRD pattern of the sintered body sample was obtained using a general X-ray diffraction device (device name: Ultima IV, manufactured by RIGAKU Corporation) under the following conditions.

[0132] Radiation source: CuKα radiation (λ=0.15418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=26° to 33° Goniometer: Radius 185mm Using the XRD pattern of the obtained sintered body, the crystallite diameter Dt (nm) was calculated from the XRD peak assigned to the (111) plane of tetragonal zirconia according to formula (1). The surface of the measurement sample to be irradiated with X-rays was polished to a mirror finish by grinding the surface of the sintered body (i.e., the sintered surface) of the sintered body immediately after sintering by 0.3 mm in the depth direction to remove the sintered surface, followed by polishing with an abrasive cloth, polishing with a diamond slurry with an average particle size of 3 μm, and polishing with colloidal silica with a particle size of 0.03 μm. (2θ difference) In addition, the 2θ difference was calculated from the XRD pattern obtained in the same manner except that the XRD measurement was carried out under the following conditions.

[0133] Radiation source: CuKα radiation (λ=1.5418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 2° / min Step width: 0.02° Measurement range: 2θ=72° to 76° Goniometer: Radius 185mm The patterns obtained by the above-mentioned XRD measurements were subjected to background subtraction and XRD peaks due to CuKα2 radiation (λ=1.5443 Å) subtraction using the integrated powder X-ray analysis software "PDXL," and the 2θ angle and 2θ difference at the peak tops of the XRD peaks corresponding to the (004) and (400) planes of tetragonal zirconia were determined. (Confirmation of the formation of spinel-type metal oxides) An XRD pattern of the sintered body sample was obtained using a general X-ray diffraction device (device name: Ultima IV, manufactured by RIGAKU Corporation) under the following conditions.

[0134] Radiation source: CuKα radiation (λ=0.15418nm) Tube voltage: 45kV Tube current: 40mA Measurement mode: Continuous scan Scan speed: 4° / min Step width: 0.02° Measurement range: 2θ=32° to 40° Goniometer: Radius 185mm The patterns obtained by the above-mentioned XRD measurements were analyzed using the integrated powder X-ray analysis software "PDXL," and the presence or absence of a peak at 2θ = 36.3° ± 0.5°, which corresponds to the (111) plane of spinel-type metal oxides, was confirmed. (color tone) The color tone of the sintered body samples was measured using a method in accordance with JIS Z 8722. A general spectrophotometer (device name: CM-700d, manufactured by Konica Minolta) was used for the measurement, and measurements were made against a black background using a black board on the back. The measurement conditions were as follows:

[0135] Light source: D65 light source Viewing angle: 10° Measurement method: SCI The sintered body samples used were disk-shaped samples with a diameter of 20 mm and a thickness of 1.8 mm. One surface of the sintered body sample was mirror-polished (Ra≦0.02 μm), and this surface was used as the evaluation surface for evaluating the color tone. The effective area for color tone evaluation was 10 mm in diameter. (Total light transmittance) The total light transmittance of the sintered body samples was measured using a method in accordance with JIS K 7361-1. Measurements were performed using a general haze meter (device name: NDH4000, manufactured by Nippon Denshoku Co., Ltd.) equipped with a D65 light source. The sintered body samples had a thickness of 0.5±0.05 mm, a diameter of 20 mm, and were mirror-polished on both sides to achieve a surface roughness Ra≦0.02 μm. (Steel ball drop test) The sintered samples were ground into disks with a diameter of 36 mm and a thickness of 0.5 mm. Both surfaces of the disk-shaped sintered samples (the 36 mm diameter surfaces; the main surfaces) were polished to a mirror finish using an automated abrasive cloth, a 3 μm average particle size diamond slurry, and a 0.03 μm average particle size colloidal silica, in that order, to obtain measurement samples. Schematic diagrams of the ball drop test are shown in Figures 1 to 3. To prevent sample fragments from breaking, mending tape 2 (0.05 mm thick) was applied to one main surface of measurement sample 1. Then, 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 mending tape 2 was in contact with the carbide plate 3. The edge of measurement sample 1 was attached to the carbide plate 3 with mending tape 2, thereby securing measurement sample 1 to 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 had been 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 spirit level.

[0136] 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 placed on the iron bar 7, which was inserted horizontally into a hole 8 located 100 cm above the top of the measurement sample 1 in the transparent PVC pipe 5. The iron bar 7 was then removed, 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 was drilled in the transparent PVC pipe 5 approximately 5 cm above the top of the measurement sample 1, allowing the insertion of an iron bar 9 (Φ5 mm, 4 cm). 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.

[0137] If no fracture was confirmed by the drop ball test, the test was repeated: three times with a 25g steel ball, three times with a 50g steel ball, and three times with a 95g steel ball.

[0138] Example 1 3 mol% yttria-stabilized zirconia (TZ-3YS, manufactured by Tosoh Corporation), niobium oxide powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), alumina (AKP-30, manufactured by Sumitomo Chemical), and a spinel-type oxide pigment containing zinc, cobalt, and iron were mixed to obtain a mixed powder having the composition shown in Table 1. Pure water was added to the obtained mixed powder to obtain a mixed slurry. The mixed slurry was pulverized in a ball mill using 10 mm diameter zirconia balls as the milling medium so that the D10 and D90 values ​​were as shown in Table 1, thereby obtaining a pulverized slurry. The pulverized slurry obtained was dried at 110°C in an air atmosphere and then sieved to remove coarse particles with an aggregate diameter exceeding 180 μm, thereby obtaining the powder of this example.

[0139] Examples 2 and 3 Powders according to Examples 2 and 3 were obtained in the same manner as in Example 1, except that mixed powders having the compositions shown in Table 1 were used.

[0140] Examples 4 to 7 The powders of Examples 4 to 7 were obtained in the same manner as in Example 1, except that mixed powders having the compositions shown in Table 1 were used and that grinding was carried out in a ball mill using zirconia balls with a diameter of 2 mm as grinding media to obtain the particle sizes shown in Table 1.

[0141] Example 8 A hydrated zirconia sol was obtained by hydrolysis of an aqueous solution of zirconium oxychloride. Yttrium chloride was added to and mixed with hydrated zirconium so that the yttrium concentration was 2.5 mol%, and the mixture was calcined in air at 1150°C for 2 hours to obtain a calcined yttrium-stabilized zirconia powder.

[0142] The obtained yttrium-stabilized zirconia calcined powder was mixed with niobium oxide powder (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), alumina (AKP-30, manufactured by Sumitomo Chemical), zinc oxide (manufactured by Kishida Chemical), and a spinel-type oxide pigment consisting of cobalt and iron to obtain a mixed powder. Pure water was added to the obtained mixed powder to form a mixed slurry. The mixed slurry was pulverized in a ball mill using 2 mm diameter zirconia balls as the milling medium so that the D10 and D90 values ​​were as shown in Table 1, thereby obtaining a pulverized slurry. The obtained pulverized slurry was dried in an air atmosphere at 110°C and then sieved to remove coarse particles with an aggregate diameter exceeding 180 μm, thereby obtaining the powder of this example.

[0143] Comparative Example 1 The powder of this comparative example was obtained in the same manner as in Example 1, except that niobium oxide was not added.

[0144] Comparative Example 2 The powder of this comparative example was obtained in the same manner as in Example 4, except that TZ-3Y (manufactured by Tosoh Corporation) was used as the 3 mol% yttria-stabilized zirconia instead of TZ-3YS (manufactured by Tosoh Corporation). The compositions and physical properties of the powders of these examples and comparative examples are shown in Table 1.

[0145] [Table 1]

[0146] (Production 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 then pressurelessly sintered at 1400°C to obtain a sintered body of this example containing 2.0% by mass of niobium, 0.5% by mass of iron, 0.25% by mass of cobalt, 0.11% by mass of zinc, 0.14% by mass of alumina, and 3.0 mol% of yttrium. The sintering conditions were as follows:

[0147] Heating rate: 100℃ / h Sintering temperature: 1400℃ Sintering temperature holding time: 1 hour Cooling rate: 200℃ / h Examples 10 to 17, and Comparative Examples 3 and 4 Sintered bodies of each example or comparative example were obtained in the same manner as in Example 9, except that the powders and sintering temperatures were changed as shown in Table 2.

[0148] [Table 2]

[0149] The sintered bodies obtained in the present example and comparative example were all dark gray or black in color.

[0150] Table 3 shows the color tones of Examples 9 to 17 and Comparative Examples 3 and 4.

[0151] [Table 3]

[0152] In all of the Examples and Comparative Examples, the formation of spinel-type metal oxides in the sintered bodies was confirmed from the XRD patterns.

[0153] 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.

[0154] The sintered body of Comparative Example 4, which was produced using the powder of Comparative Example 1 that did not contain niobium, had a -2θ difference of less than 1.55°, and in a ball drop test, cracks occurred when a 25 g steel ball was dropped on it once, confirming that the impact resistance was insufficient.

[0155] In addition, the BET specific surface area is 17m 2 The sintered body of Comparative Example 5, which was produced using the powder of Comparative Example 2 having a SiO2 content of 1 / g or more and a D90 of 1.3 μm or more, was confirmed to have a crystallite diameter Dt of less than 25 nm and a 2θ difference of less than 1.54°.

[0156] Furthermore, the sintered body of Comparative Example 5 cracked when a 25 g steel ball was dropped on it once in a ball drop test, confirming that it had insufficient impact resistance.

[0157] On the other hand, it contains stabilizing elements, niobium, alumina, iron, cobalt and zinc, and has a BET specific surface area of ​​5.0 m 2 / g or more 17m 2 From the zirconia powders of Examples 1 to 8, which had a ZnO content of 0.1 / g or less and a D90 of 1.3 μm or less, zirconia sintered bodies of Examples 9 to 17 were obtained, containing stabilizing elements, niobium, alumina, iron, cobalt, and zinc, and having a crystallite diameter Dt of 25 nm to 100 nm. The sintered bodies were confirmed to have high impact resistance, not breaking even when a 25 g to 50 g steel ball was dropped on them three times. It was also confirmed that the transmittance at a thickness of 0.5 mm was 0%, demonstrating a high shielding factor.

[0158] Furthermore, the sintered body of Comparative Example 4, which did not contain niobium oxide (powder used: Comparative Example 1), had a high transmittance of 0.2%, unlike the sintered body of Example 9, which contained 2.0 mass% niobium oxide (powder used: Example 1).

[0159] Figures 4A and 4B, and Figure 5 show external photographs of the sintered bodies of Comparative Example 4 and Example 9, each 0.5 mm thick, placed on a shielding plate with a hole 1 cm in diameter, using a commercially available LED light (800-LED028, manufactured by Sanwa Supply Co., Ltd.) as a light source.

[0160] As shown in Figures 4A and 4B, the holes in the shielding plate of the sintered body of Comparative Example 4, which had a transmittance of 0.2%, were visible from the top surface of the sintered body. On the other hand, as shown in Figure 5, the holes in the shielding plate of the sintered body of Example 9, which had a transmittance of 0%, were not visible from the top surface of the sintered body, demonstrating high shielding properties. [Explanation of symbols]

[0161] 1...Measurement sample 2. Mending tape 3...Carbide plate 4...Steel ball 5...Transparent PVC pipe 6...Clamp 7. Horizontal bar 8...holes

Claims

1. A zirconia sintered body containing a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, wherein the zirconia sintered body has a crystallite diameter of 25 nm or more and 100 nm or less, calculated from an XRD peak belonging to the (111) plane of tetragonal zirconia.

2. The zirconia sintered body according to claim 1, wherein at least a portion of the pigment component forms a spinel-type metal oxide.

3. 3. The zirconia sintered body according to claim 1 or 2, wherein the stabilizing element comprises 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% or more and 5.5 mol% or less.

4. The 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.

5. A zirconia sintered body as described in claim 1 or 2, having an iron content of 0.1 mass% or more and 5 mass% or less, a cobalt content of 0.1 mass% or more and 3 mass% or less, and a zinc content of 0.05 mass% or more and 1 mass% or less, calculated as oxides.

6. The zirconia sintered body according to claim 1 or 2, wherein the alumina content is more than 0 mass% and not more than 30 mass%.

7. 3. The zirconia sintered body according to claim 1, 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 1.54° or more.

8. Lightness L ＊ The zirconia sintered body according to claim 1 or 2, wherein the zirconia sintered body has a molecular weight of 40 or more and 65 or less.

9. The zirconia sintered body according to claim 1 or 2, having a total light transmittance of 0.1% or less at a thickness of 0.5 mm.

10. A zirconia powder containing a stabilizing element, niobium, alumina, and iron, cobalt, and zinc as pigment components, wherein the content of the stabilizing element is 2.0 mol% or more and 5.5 mol% or less, the content of niobium is 0.1 mass% or more and 3.0 mass% or less, the content of alumina is more than 0 mass% and 30 mass% or less, and the BET specific surface area is 5.0 m ２ / g or more 17m ２ / g or less.

11. 11. The zirconia powder according to claim 10, wherein the pigment component is contained as a spinel-type metal oxide containing iron, cobalt, and zinc.

12. 12. The zirconia powder according to claim 10, wherein the iron content is from 0.1% by mass to 5% by mass, the cobalt content is from 0.1% by mass to 3% by mass, and the zinc content is from 0.05% by mass to 1% by mass, calculated as oxides.

13. 12. The zirconia powder according to claim 10, wherein the 10% particle diameter 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 D90 in the cumulative particle size distribution of the powder is 0.5 μm or more and 1.3 μm or less.

14. A member comprising the zirconia sintered body according to claim 1 or 2.

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