JP6911290B2 - Colored translucent zirconia sintered body, its manufacturing method, and its use - Google Patents

Description

The present invention relates to a colored zirconia sintered body having high translucency and strength, and a method for producing the same.

A sintered body containing zirconia as a main component and having translucency (hereinafter, also referred to as “translucent zirconia sintered body”) is superior in mechanical properties to glass and alumina. Therefore, the translucent zirconia sintered body is being studied as a material for applications that require not only optical properties but also mechanical properties.

For example, Patent Document 1 discloses a translucent zirconia sintered body as a material suitable for dental materials, exterior members, and the like. The translucent zirconia sintered body was a zirconia sintered body containing 3 mol% yttria.

Patent Document 2 discloses a translucent zirconia sintered body as a material suitable for dental materials, particularly orthodontic brackets. The translucent zirconia sintered body was a zirconia sintered body containing 8 mol% yttria.

Patent Document 3 discloses a zirconia sintered body as a dental material, particularly a denture and a material suitable for a mill blank for obtaining a denture. The zirconia sintered body was a zirconia sintered body containing yttria and titania.

Publication of Patent No. 2008-050247 Patent Publication No. 2009-269812 Publication of Patent No. 2008-222450

In the conventional zirconia sintered body, the content of the stabilizer in the zirconia is increased, so that the translucency is increased and the strength is decreased. On the other hand, due to the low content of the stabilizer, the conventional zirconia sintered body has a low translucency and a high strength. As described above, the conventional zirconia sintered body has only high translucency or strength.

An object of the present invention is to solve these problems and to provide a zirconia sintered body having high translucency and high strength, and also having excellent aesthetics and design.

The researchers investigated a translucent zirconia sintered body. As a result, it was found that by controlling the structure structure in the crystal particles, a sintered body having both strength and translucency can be obtained. It has been found that the structure structure in such crystal particles can be controlled by dissolving lanthanum in zirconia. Furthermore, it has been found that the sintered body can be colored without changing the structure structure in the crystal particles, and the design property can be further enhanced.

That is, the present invention is characterized by containing crystal particles having a cubic domain and a tetragonal domain, dissolving a stabilizer and lanthanum as a solid solution, and containing at least one of a lanthanoid other than lanthanum or a transition metal. It is a zirconia sintered body.

Hereinafter, the zirconia sintered body of the present invention will be described.

The zirconia sintered body of the present invention is a lanthanum solid-dissolved zirconia sintered body in which lanthanum is solid-dissolved in zirconia, rather than simply containing lanthanum (La) in the sintered body. The solid solution of the lantern makes the structure of the crystal particles of the sintered body finer.

In the zirconia sintered body of the present invention (hereinafter, also referred to as “sintered body of the present invention”), the fact that the lantern is solid-dissolved in zirconia is a powder X-ray diffraction (hereinafter, referred to as “XRD”) pattern. You can check from. The sintered body of the present invention has a peak of 2θ = 30 ± 2 ° (hereinafter, also referred to as “main peak”) in XRD measurement using CuKα ray (λ = 0.15418 nm) as a radiation source. The main peak is a peak in which the XRD peak of tetragonal zirconia (2θ = 30.0 ± 2 °) and the XRD peak of cubic zirconia (2θ = 29.6 ± 2 °) overlap, and the sintering of the present invention. This is the XRD peak with the strongest diffraction intensity in the XRD pattern of the body. Since the lattice constant obtained from the main peak is larger than that of the zirconia sintered body in which the lanthanum is not solid-solved, it can be confirmed that the lanthanum is solid-solved in zirconia in the sintered body of the present invention. For example, when the sintered body of the present invention contains lantern and 3 mol% yttria, its lattice constant is larger than the lattice constant of the zirconia sintered body containing only the same amount of yttria. The large lattice constant can be confirmed from the fact that the main peak shifts to the low angle side in the XRD pattern.

Further, it is preferable that the sintered body of the present invention does not substantially contain a composite oxide composed of lanthanum and zirconium or a lanthanum oxide (hereinafter, also referred to as "lanthanum oxide or the like"). By not containing lanthanum oxide or the like, the sintered body of the present invention becomes a sintered body having higher translucency. The absence of lanthanum oxide or the like can be confirmed from the fact that the XRD pattern of the sintered body of the present invention does not have an XRD peak corresponding to other than the XRD peak of zirconia. Examples of the lanthanum oxide and the like include La ₂ Zr ₂ O ₇ and La ₂ O _3.

The lanthanum content of the sintered body of the present invention is preferably 1 mol% or more. By containing 2 mol% or more of lanthanum, the domain in the crystal particles tends to become fine. The lanthanum content (mol%) is at least one of zirconia in the sintered body, a stabilizer, an oxide-converted lanthanum (La ₂ O ₃ ), and a lanthanoid or transition metal other than lanthanum (hereinafter, "coloring component"). It is the molar ratio of lanthanum converted to oxide to the total of converted lanthanum. Since all the lanterns are dissolved in zirconia, the lanthanum content of the sintered body of the present invention is preferably 10 mol% or less. By setting the lanthanum content to 10 mol% or less, the precipitation of lanthanum oxide and the like is further suppressed, and the strength of the sintered body of the present invention tends to be increased. Preferred lanthanum content is 1 mol% or more and 10 mol% or less, further 1 mol% or more, 7 mol% or less, further 2 mol% or more and 10 mol% or less, further 2 mol% or more, 7 mol% or less, and further 2 mol. % Or more and 6.5 mol% or less, and further 3 mol% or more and 6.5 mol% or less.

In addition to the stabilizer and lanthanum, the sintered body of the present invention contains at least one kind (coloring component) of a lanthanoid or a transition metal other than lanthanum. By containing a coloring component, the sintered body of the present invention develops a color other than colorless. Such coloring can improve the design of the sintered body. The number of moles of the coloring component when converted to oxide differs greatly depending on the type. On the other hand, the content of the coloring component is, for example, 0.01 wt% or more and 5 wt% or less, and further 0.01 wt% or more and 3 wt% or less as the weight ratio of the colored component in terms of oxide to the weight of the sintered body. Can be mentioned.

Examples of lanthanoid elements other than lanthanum include cerium (Ce), praseodymium (Pr), neodymium (Nd), europium (Eu), gadolinium (Gd), terbium (Tb), disprodium (Dy), holonium (Ho), and erbium (Er). ), Thurium (Tm), Itterbium (Yb) and Lutetium (Lu), and at least one of the group consisting of cerium, praseodymium, neodymium and erbium.

Since the lanthanoid element has a function of stabilizing zirconia, it has been considered that if a lanthanoid element other than lanthanum is contained, it becomes difficult to obtain crystal particles containing a cubic domain and a tetragonal domain. However, in the sintered body of the present invention, lanthanoids other than lanthanum can coexist without affecting the structure of crystal particles obtained by solid solution of the stabilizer and lanthanum. The content of lanthanoid elements other than lanthanum in the sintered body of the present invention preferably exceeds 0.6 mol%. The content of the lanthanoid other than lanthanum may be 0.65 mol% or more, further 0.7 mol% or more, and the lanthanoid element may be 2 mol% or less, further 1.5 mol% or less. When the content of lanthanoids other than lanthanum is in this range, these lanthanoids are also solid-solved in zirconia while maintaining the structure of the crystal particles obtained by solid-solving the stabilizer and lanthanum. It is possible to show the coloration caused by these lanthanoids.

The transition metal contained in the sintered body of the present invention is a group consisting of copper (Cu), iron (Fe), cobalt (Co), manganese (Mn), chromium (Cr), nickel (Ni) and vanadium (V). At least one of the group consisting of iron, manganese, chromium, copper and vanadium is preferable. Since the coloration caused by the transition metal is strong, it is easy to color the sintered body even if the content is lower than that of the lanthanoid. The content of the transition metal in the sintered body of the present invention may be 0.01 mol% or more as an element, further 0.05 mol% or more, and 0.2 mol% or less as a transition metal element, further 0.1 mol% or less. It should be.

The number of moles of the coloring component contained in the oxide differs greatly depending on the type of the coloring component element, for example, Nd ₂ O ₃ and Pr ₆ O _{11 in the oxide of the coloring component.} Therefore, as the coloring component, for example, Nd ₂ O ₃ is regarded as _{Nd O 1.5} , Pr ₆ O ₁₁ is regarded as _{Pr O 11/6,} and V ₂ O ₅ is regarded as VO _2.5 , that is, the coloring component element in the composition formula. It can also be converted as an oxide conversion amount (hereinafter, also referred to as "specific oxide conversion") in which the number of is expressed as 1. The amount converted to specific oxide is equal to the elemental amount of the coloring component in the sintered body.

Therefore, the content of the coloring component of the sintered body of the present invention is the weight ratio (wt%) of the coloring component in terms of oxide to the weight of the sintered body, or zirconia, stabilizer, oxide in the sintered body. The molar ratio of the colored component converted to the specific oxide to the total of the converted lanthanum (La ₂ O _{3) and the colored component converted to the specific oxide may be used.}

The sintered body of the present invention contains a stabilizer. The stabilizer dissolves in zirconia. When the lanthanum and the stabilizer are dissolved in zirconia, the crystal particles of the sintered body of the present invention contain the cubic domain and the tetragonal domain even in a low temperature environment such as room temperature. The stabilizer is preferably at least one of the group consisting of Itria (Y ₂ O ₃ ), Scandia (Sc ₂ O ₃ ), Calcia (CaO), and Magnesia (MgO). Since it is easy to use industrially, the stabilizer is preferably at least one of the group consisting of calcia, magnesia and ittoria, and more preferably yttrium.

The stabilizer contained in the sintered body of the present invention is 2 mol% or more, 7 mol% or less, further 2 mol% or more and 5 mol% or less, further 2.1 mol% or more and 4.9 mol% or less, and further 2 mol. % Or more and 4 mol% or less. The stabilizer content (mol%) is the amount of the stabilizer with respect to the total of zirconia, stabilizer, oxide-converted lanthanum (La ₂ O ₃ ) and oxide-converted coloring component in the sintered body. It is a molar ratio.

The sintered body of the present invention is a zirconia sintered body, which is a sintered body containing zirconia as a main component. Therefore, the total content of the stabilizer and the lanthanum contained in the sintered body of the present invention may be less than 50 mol%. The zirconia content of the sintered body of the present invention may be more than 50 mol%, more preferably 60 mol% or more, further 80 mol% or more, further more than 83 mol%, and further preferably 90 mol% or more. ..

The sintered body of the present invention may contain _{alumina (Al 2} O _3). By containing alumina, the translucency tends to be high especially in a sintered body having high strength. When the sintered body of the present invention contains alumina, the alumina content is preferably 100% by weight or more and 2000% by weight or less, and more preferably 200% by weight or more and 1000% by weight or less. The alumina content (ppm by weight) is the oxide-converted aluminum (weight ppm) with _{respect to the total weight of zirconia, stabilizer, oxide-converted lanthanum (La 2} O ₃ ) and oxide-converted coloring component in the sintered body. It is the weight ratio of Al ₂ O _3).

The sintered body of the present invention has the above composition, but may contain unavoidable impurities. Examples of unavoidable impurities include hafnium (Hf).

The sintered body of the present invention has a cubic domain and a tetragonal domain in the crystal particles. By including the cubic domain and the tetragonal domain in the crystal particles, not only the translucency is high but also the strength is high. In the present invention, a domain is at least one of a crystallite or an aggregate of crystallites in a crystal particle, and is a portion in which the same crystal structure is continuous. The cubic domain is a domain whose crystal structure is a cubic fluorite type structure, and the tetragonal domain is a domain whose crystal structure is a tetragonal fluorite type structure. It can be confirmed by Rietveld analysis of the XRD pattern that the sintered body of the present invention has a cubic domain and a tetragonal domain in its crystal particles. That is, it can be confirmed by Rietveld analysis of the XRD pattern that the sintered body of the present invention contains cubic crystals and tetragonal crystals. Moreover, since the crystallite diameters of cubic and tetragonal crystals calculated by Rietveld analysis are smaller than the crystal particle diameter, it can be confirmed that the crystal particles include the cubic and tetragonal domains. can. Further, it is preferable that the crystallite diameter of the tetragonal crystal and the crystallite diameter of the cubic crystal are about the same. For example, the crystallite diameter of the cubic crystal is 0.8 to 1.3 with respect to the crystallite diameter of the tetragonal crystal. Further, it may be 0.9 to 1.1. The sintered body of the present invention contains crystal particles having a cubic domain and a tetragonal domain, and is preferably composed of crystal particles having a cubic domain and a tetragonal domain.

Since the sintered body of the present invention contains the above domains, its crystal structure includes a cubic fluorite type structure and a tetragonal fluorite type structure. Furthermore, the sintered body of the present invention preferably contains substantially no monoclinic crystals. Here, the fact that the monoclinic crystal is not substantially contained means that the XRD peak of the monoclinic crystal is not confirmed in the XRD pattern.

The lantern concentrations of the cubic domain and the tetragonal domain may be the same, but in the sintered body of the present invention, the lantern concentrations of the cubic domain and the tetragonal domain in the crystal particles may be different. Furthermore, the lantern concentration in the cubic domain may be higher than the lantern concentration in the tetragonal domain. In the present invention, the lanthanum concentration in each domain can be observed by composition analysis in transmission electron microscope (hereinafter referred to as "TEM") observation.

The sintered body of the present invention has an average crystallite diameter (hereinafter, also simply referred to as “average crystallite diameter”) calculated from the full width at half maximum of the main peak (hereinafter, referred to as “FWHM”) of 255 nm or less. Is preferable. When the average crystallite diameter is 250 nm or less, further 150 nm or less, and further 130 nm or less, the translucency tends to be high. Further, when the average crystallite diameter is 100 nm or less, further 60 nm or less, further 50 nm or less, further 35 nm or less, and further 25 nm or less, light scattering is further suppressed. As a result, the translucency of the sintered body of the present invention becomes higher.

The average crystallite diameter is preferably small, but in the sintered body of the present invention, it is usually 2 nm or more, further 5 nm or more, further 10 nm or more, and further 15 nm or more.

The fact that the average crystallite diameter of the sintered body of the present invention is 255 nm or less can be confirmed by the fact that the FWHM is 0.1536 ° or more in the XRD pattern of the sintered body of the present invention. Therefore, the sintered body of the present invention preferably has a FWHM of 0.1536 ° or more. The larger the FWHM, the smaller the average crystallite diameter. For example, FWHM is 0.154 ° or more when the average crystallite diameter is 250 nm or less, 0.178 ° or more when the average crystallite diameter is 150 nm or less, 0.187 ° or more when the average crystallite diameter is 130 nm or less, and 100 nm or less. It becomes 0.25 ° C. or higher. The FWHM is preferably 0.3 ° or more, more preferably 0.4 ° or more. On the other hand, the higher the crystallinity, the smaller the FWHM of the XRD peak, but the FWHM that can be measured in a normal XRD measurement is up to about 40 °. The FWHM of the main peak of the sintered body of the present invention is 1 ° or less, more preferably 0.7 ° or less.

The crystallite diameters of cubic crystals and tetragonal crystals contained in the crystal particles of the present invention can be determined by Rietveld analysis of the XRD pattern of the sintered body of the present invention. That is, the Rietveld method separates the XRD pattern of the sintered body of the present invention into an XRD peak caused by cubic crystals and an XRD peak caused by tetragonal crystals. The half-value width of the XRD peak of each crystal structure after separation may be obtained, and the crystallite diameter may be obtained from the obtained half-value width by the following Scherrer equation.

D = K × λ / ((β−B) × cosθ)
In the above formula, D is the crystallite diameter (nm) of each crystal, K is the Scheller constant (1.0), λ is the wavelength of CuKα (0.15418 nm), β is the half width (°), and B is the device constant (approximate constant). 0.1177 °) and θ are the diffraction angles (°) of the XRD peak. The XRD peaks used to determine the full width at half maximum are the XRD peak with 2θ = 30.0 ± 2 ° for tetragonal crystals and the XRD peak with 2θ = 29.6 ± 2 ° for cubic crystals.

The average crystal particle size of the sintered body of the present invention is 20 μm or more and 150 μm or less, and further 20 μm or more and 100 μm or less. When the average crystal particle size is in this range, the sintered body has high translucency. In the present invention, the average crystal particle size can be measured by the planimetric method.

The sintered body of the present invention preferably has a high density. The density varies depending on the amount of stabilizer and lanthanum. The density of the sintered body of the present invention is 6.0 g / cm ³ or more 6.2 g / cm ³ or less, more can be exemplified 6.0 g / cm ³ or more 6.12 g / cm ³ or less.

The sintered body of the present invention has high translucency. Therefore, in the sintered body of the present invention, the maximum value of the total light transmittance (hereinafter, also simply referred to as “total light transmittance”) at a sample thickness of 1 mm and a measurement wavelength of 300 to 800 nm is 45% or more. The higher the translucency, the more preferable, and the maximum value of the total light transmittance is preferably 50% or more, and further preferably 55% or more. The sintered body of the present invention absorbs wavelengths in the visible light region due to coloration. Therefore, it can be confirmed that the sintered body of the present invention has high translucency if it has the above-mentioned total light transmittance at any of the measurement wavelengths. On the other hand, the value of the transmittance measured with the measurement wavelength fixed (for example, the measurement wavelength of 600 nm) and the value of the transmittance measured with a radiation source having a plurality of wavelengths (for example, sunlight or a D65 light source) are set. It cannot be used as an index for comparing the translucency of sintered bodies having different colors.

The translucency of the sintered body of the present invention may satisfy the above-mentioned total light transmittance, but the linear transmittance at a sample thickness of 1 mm and a measurement wavelength of 300 to 800 nm (hereinafter, also simply referred to as “linear transmittance”). The maximum value of is 1% or more, further 3% or more, further 10% or more, further 20% or more, and further 30% or more. It can be exemplified that the upper limit of the linear transmittance of the sintered body of the present invention is 70% or less, further 66% or less.

The sintered body of the present invention has high strength. The bending strength of the sintered body of the present invention is 500 MPa or more, and further 600 MPa or more. Since the applicable applications are widened, the strength of the sintered body of the present invention is preferably 800 MPa or more, more preferably 1000 MPa or more. The strength in the present invention is 500 MPa or more and 1600 MPa or less, and further 600 MPa or more and 1500 MPa or less as the biaxial bending strength measured according to ISO / DIS6782. Further, the strength in the present invention is 500 MPa or more and 1500 MPa or less, and further 600 MPa or more and 1200 MPa or less as the three-point bending strength measured according to JIS R1601.

The sintered body of the present invention preferably has fracture toughness equal to or higher than that of a translucent zirconia sintered body made of cubic zirconia such as an 8 mol% yttria-containing zirconia sintered body. Thereby, the sintered body of the present invention can be used as a member in which the conventional translucent zirconia sintered body is used. As fracture toughness of the sintered body of the present invention 1.7MP ^{· m 0.5} or more, still more 2 MPa ^{· m 0.5} or more, also be mentioned that further is 2.2 MPa ^{· m 0.5} or more.

In the present invention, the fracture toughness can be measured by the IF method according to JIS R1607.

Next, a method for producing the zirconia sintered body of the present invention will be described.

In the zirconia sintered body of the present invention, at least one of a lanthanoid raw material other than lantern or a transition metal raw material, a zirconia raw material, a stabilizer raw material and a lantern raw material are mixed to obtain a mixed powder, and the obtained mixed powder is used. A molding step of molding to obtain a molded body, a sintering step of sintering the obtained molded body at a sintering temperature of 1650 ° C. or higher to obtain a sintered body, and a sintering temperature of 1 ° C./up to 1000 ° C. It can be manufactured by a manufacturing method, which comprises a temperature lowering step of lowering the temperature at a temperature lowering rate of more than min.

In the mixing step, at least one of a lanthanoid raw material other than lanthanum or a transition metal raw material (hereinafter, also referred to as “coloring component raw material”), a zirconia raw material, a stabilizer raw material, and a lanthanum raw material are mixed to obtain a mixed powder. As long as the coloring component raw material, the zirconia raw material, the stabilizer raw material, and the lanthanum raw material are uniformly mixed, the mixing method may be either wet mixing or dry mixing. Since a more uniform mixed powder can be obtained, the mixing method is preferably wet mixing, and more preferably wet mixing by at least one of a wet ball mill and a wet stirring mill.

The zirconia raw material is zirconia or a precursor thereof, and examples thereof include zirconia powder having ^{a BET specific surface area of 4 to 20 m 2 / g.}

Examples of the stabilizer raw material include powder of at least one (stabilizer) of the group consisting of yttrium, scandia, calcia, and magnesia (stabilizer) or a precursor thereof, and further, yttrium powder or a precursor thereof.

Further, the zirconia raw material is preferably a zirconia powder containing a stabilizer. Such zirconia powder becomes a zirconia raw material and a stabilizer raw material. The stabilizer contained in the zirconia powder is preferably at least one of the group consisting of yttria, scandia, calcia, and magnesia, and more preferably yttria. As the stabilizer-containing zirconia powder, a zirconia powder containing a stabilizer of 2 mol% to 7 mol%, and a zirconia having a BET specific surface area of 4 to ²⁰ m 2 / g and containing a stabilizer of 2 mol% to 7 mol%. It is preferably a powder. The amount of the stabilizer contained in the stabilizer-containing zirconia powder is preferably 2 mol% to 5 mol%, more preferably 2 mol% to 4 mol%.

Examples of the lanthanum raw material include compounds containing lanthanum, and at least one of the group consisting of lanthanum oxide, lanthanum hydroxide, lanthanum nitrate, lanthanum sulfate, lanthanum chloride, lanthanum carbonate, and pyrochlor type La ₂ Zr ₂ O _{7 is used.} It can be mentioned, preferably at least one of _{lanthanum oxide or La 2} Zr ₂ O _7.

The coloring component raw material may be at least one of the group consisting of oxides, nitrates, sulfates, chlorides, carbonates and pyrochloroa-type structures of the coloring component, and is preferably an insoluble salt of the coloring component. It is preferably at least one of oxides and carbonates. The amount of the coloring component may be any amount, but the weight ratio of the coloring component raw material to the weight of the mixed powder may be, for example, 0.01 wt% or more and 5 wt% or less, and further 0.05 wt% or more and 3 wt% or less. Can be mentioned.

The mixed powder may contain an alumina raw material. Examples of the alumina raw material include compounds containing aluminum, and examples thereof include at least one of the group consisting of alumina, aluminum hydroxide, aluminum carbonate and spinel, and further examples of alumina. Preferred alumina includes at least one of α-type alumina and γ-type alumina, and further includes α-type alumina.

The composition of the mixed powder may be any desired ratio.

In the molding step, the mixed powder is molded to obtain a molded product. The molding method is arbitrary as long as a molded product having a desired shape can be obtained. As the molding method, at least one of a group consisting of press molding, injection molding, sheet molding, extrusion molding, and casting molding can be mentioned, and at least one of press molding or injection molding is preferable.

Further, the shape of the obtained molded product is arbitrary, and examples thereof include shapes such as a disc shape, a columnar shape, and a polyhedral shape, an orthodontic bracket, a semiconductor manufacturing jig, and other complicated shapes. can.

In the sintering step, by sintering the molded product, a sintered body having a high-temperature crystal structure such as cubic crystal is obtained. Therefore, in the sintering step, the obtained molded product is sintered at a sintering temperature of 1650 ° C. or higher. It is considered that the crystal structure of the sintered body becomes a high temperature type crystal structure by sintering at 1650 ° C. or higher. When a sintered body having a high-temperature type crystal structure undergoes a temperature lowering step, a cubic domain and a rectangular domain are generated as a crystal structure in the crystal particles, and the sintered body including the crystal structure of the sintered body of the present invention is sintered. You can get a body. The sintering temperature is preferably 1700 ° C. or higher, more preferably 1725 ° C. or higher, and further preferably 1750 ° C. or higher. When a general-purpose firing furnace is used, the sintering temperature is 2000 ° C. or lower, further 1900 ° C. or lower, and further 1800 ° C. or lower.

The sintering method is arbitrary as long as it is sintered at the above sintering temperature. As the sintering method, for example, at least one of the group consisting of normal pressure sintering, pressure sintering and vacuum sintering can be mentioned, and normal pressure sintering and pressure sintering are preferable.

As a preferable sintering step in the production method of the present invention, a primary sintering in which a molded body is fired at 1000 ° C. or higher and lower than 1650 ° C. to obtain a primary sintered body and a primary sintering body in which the primary sintered body is sintered at 1650 ° C. or higher are used. A sintering step including subsintering (hereinafter, also referred to as “two-stage sintering method”) can be mentioned.

In the two-stage sintering method, the molded body is first-sintered to obtain a primary-sintered body, and the primary-sintered body is secondarily sintered. For the primary sintering, it is preferable to sinter the molded product at 1000 ° C. or higher and lower than 1650 ° C. The atmosphere of the primary sintering is preferably at least one of an oxidizing atmosphere and a reducing atmosphere, and is preferably an atmospheric atmosphere. Preferred primary sinterings include atmospheric pressure sinterings of 1000 ° C. or higher and lower than 1650 ° C., further 1400 ° C. or higher and 1520 ° C. or lower, and further 1425 ° C. or higher and 1500 ° C. or lower. As a result, the structure of the obtained primary sintered body becomes fine. In addition to this, it becomes difficult for pores to be formed in the crystal particles of the primary sintered body.

In the secondary sintering, the primary sintered body is sintered at 1650 ° C. or higher, further 1700 ° C. or higher, further 1725 ° C. or higher, and further 1750 ° C. or higher. In order to obtain a sintered body having high strength, the secondary sintering temperature is preferably 2000 ° C. or lower, further 1900 ° C. or lower, and further preferably 1800 ° C. or lower. By setting the secondary sintering temperature to 2000 ° C. or lower, it becomes difficult to generate coarse crystal particles. A particularly preferable secondary sintering temperature can be raised to 1675 ° C. or higher and 1775 ° C. or lower.

In order to obtain a higher density sintered body, the secondary firing is preferably a hot hydrostatic press (hereinafter referred to as "HIP") treatment.

The HIP processing time (hereinafter referred to as "HIP time") is preferably at least 10 minutes. If the HIP time is at least 10 minutes, the pores of the sintered body are sufficiently removed during the HIP treatment.

Examples of the HIP-treated pressure medium (hereinafter, also simply referred to as “pressure medium”) include argon gas, nitrogen gas, oxygen, and the like, but general argon gas is convenient.

The HIP treatment pressure (hereinafter, also referred to as “HIP pressure”) is preferably 5 MPa or more, more preferably 50 MPa or more. When the HIP pressure is 5 MPa or more, the removal of pores in the sintered body is further promoted. The upper limit of the pressure is not particularly specified, but when a normal HIP device is used, the HIP pressure is 200 MPa or less.

In the HIP treatment, it is preferable to arrange the molded product or the primary sintered body in a container made of a non-reducing material. As a result, local reduction of the sintered body by the reducing component derived from the material of the HIP device such as a heating element is suppressed. Examples of the non-reducing material include at least one of the group consisting of alumina, zirconia, mullite, yttria, spinel, magnesia, silicon nitride and boron nitride, and at least one of alumina or zirconia.

In the temperature lowering step, the temperature is lowered from the sintering temperature to 1000 ° C. at a temperature lowering rate of more than 1 ° C./min. By setting the temperature lowering rate to more than 1 ° C./min, further to 5 ° C./min or more, and further to 8 ° C./min or more, a sintered body having high translucency can be obtained. When the temperature lowering rate is 1 ° C./min or less, precipitates and monoclinic crystals are formed, so that the obtained sintered body has low translucency. The translucency of the obtained sintered body is remarkably low. In order to obtain a lanthanum solid solution zirconia sintered body having higher translucency, the temperature is lowered from the firing temperature to 1000 ° C. at a temperature lowering rate of 10 ° C./min or more, further 15 ° C./min or more, and further 30 ° C./min. It is preferably min or more, and more preferably 50 ° C./min or more. Preferred temperature lowering rates include 30 ° C./min or more and 100 ° C./min or less, and further 50 ° C./min or more and 100 ° C./min or less.

The production method of the present invention may include an annealing step of heat-treating the sintered body after the temperature lowering step. By subjecting the sintered body to the annealing step, the translucency of the sintered body can be further increased. Examples of the annealing step include treating the sintered body at 900 ° C. or higher and 1200 ° C. or lower, and further 980 ° C. or higher and 1030 ° C. or lower in an oxidizing atmosphere.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a zirconia sintered body having both high translucency and high strength. The sintered body of the present invention has higher translucency and mechanical strength than conventional translucent ceramics. Therefore, when used as a dental member such as an orthodontic bracket that requires aesthetics, its size can be reduced. As a result, it can be used as a dental member with higher aesthetics.

Rietveld analysis result of XRD pattern of zirconia sintered body of Example 1 Appearance of the zirconia sintered body of Example 1 UV-VIS spectrum of the zirconia sintered body of Example 1 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 2 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 3 (a: total light transmittance, b: linear transmittance) Appearance of the zirconia sintered body of Example 4 UV-VIS spectrum of the zirconia sintered body of Example 4 (a: total light transmittance, b: linear transmittance) Appearance of the zirconia sintered body of Example 5 UV-VIS spectrum of the zirconia sintered body of Example 5 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 6 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 7 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 8 (a: total light transmittance, b: linear transmittance) UV-VIS spectrum of the zirconia sintered body of Example 9 (a: total light transmittance, b: linear transmittance)

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.
(Measurement of density)
The measured density of the sintered sample was determined by measuring the weight in water by the Archimedes method.

(Measurement of average crystal grain size)
After surface grinding the sintered sample, mirror polishing was performed using 9 μm, 6 μm, and 1 μm diamond abrasive grains in this order. The polished surface was held at 1400 ° C. for 1 hour, heat-etched, and then observed by SEM. From the obtained SEM observation diagram, the average crystal grain size was determined by a planimetric method.

(Identification of crystal structure)
By identifying and analyzing the XRD pattern obtained by the XRD measurement of the sintered body sample, the crystal structure of each sintered body sample was identified and the presence or absence of the impurity layer was confirmed. The XRD measurement was performed on a mirror-polished sintered body sample using a general powder X-ray diffractometer (device name: UltraIII, manufactured by Rigaku Co., Ltd.). The conditions for XRD measurement are as follows.
Radioactive source: CuKα ray (λ = 0.15418 nm)
Measurement mode: Step scan
Scan conditions: 0.04 ° / s
Divergence slit: 0.5 deg
Scattering slit: 0.5 deg
Light receiving slit: 0.3 mm
Measurement time: 1.0 second
Measurement range: 2θ = 20 ° to 80 °
XRD analysis software (trade name: JADE7, manufactured by MID) was used for the identification analysis of the XRD pattern.

(Measurement of average crystallite diameter)
The average crystallite diameter of the sintered sample was determined using the Scherrer equation for the range of 2θ = 27 ° to 30 ° of the XRD pattern obtained by the same measurement method as the identification of the crystal phase.
D = K × λ / ((β−B) × cosθ)
In the above formula, D is the average crystallite diameter (nm), K is the Scheller constant (1.0), λ is the wavelength of CuKα (0.15418 nm), β is the half width (°), and B is the device constant (0. 1177 °) and θ are the diffraction angles (°) of the main peak.
As for the main peak, the peak corresponding to the cubic (111) plane of zirconia and the peak corresponding to the tetragonal (111) plane were regarded as a single peak.
The full width at half maximum was determined using Industrial Analysis for Windows (Version 6.0) manufactured by Rigaku.

(Rietveld analysis)
By Rietveld analysis of the XRD pattern obtained by the same measurement method as the identification of the crystal structure, the ratio of each cubic and tetragonal crystal structure in the sintered sample, the crystallite diameter, and the lattice constant can be determined. I asked. A general-purpose program (Rietan-2000) was used for Rietveld analysis.
From the resulting lattice constant was determined Y ₂ O ₃ concentration of tetragonal Akirachu based on the following equation.
YO _1.5 = (1.0223-cf / af) /0.001319
Y ₂ O ₃ = 100 x YO _1.5 / (200-YO _1.5 )
In the above formula, YO _1.5 is the yttria concentration, and cf and af are the lattice constants of the c-axis and a-axis of the tetragonal fluorite-type structure obtained by Rietveld analysis, respectively.

(Measurement of transmittance)
The total light transmittance, the diffuse transmittance, and the linear transmittance of the sample were measured by UV-VIS by the method according to the method of JIS K321-1. The measurement conditions are as follows.
Light source: Deuterium lamp and halogen lamp Measurement wavelength: 200 to 800 nm
Measurement step: 1 nm
A general double-beam spectrophotometer (device name: V-650 type, manufactured by JASCO Corporation) was used for UV-VIS measurement.
A disk-shaped molded product having a diameter of 16 mm and a thickness of 1.0 mm was used as the measurement sample. Prior to the measurement, both sides of the measurement sample were polished, and the surface roughness Ra was mirror-polished to 0.02 μm or less.

(Brightness, hue)
As a measurement sample, a sample having a sample thickness of 1 mm and having a surface roughness Ra = 0.02 μm or less was mirror-polished on both sides was used. The measurement is performed using a precision spectrophotometric colorimeter (device name: TC-1500SX, manufactured by Tokyo Denshoku) in accordance with Sections 5.3 and 5.4 of JIS K7105 "Plastic Optical Property Test Method". rice field. In the measurement, a D65 ray is applied to a measurement sample having a standard white plate placed on the back surface, the light transmitted through the measurement sample is reflected by the white plate, and the light transmitted through the measurement sample is measured again to obtain a brightness L ^* , The hues a ^* and b ^* were determined. A D65 ray was used for the measurement.

(Measurement of biaxial bending strength)
The biaxial bending strength of the sample was measured by the biaxial bending strength measurement according to ISO / DIS6782. The thickness of the measurement sample was set to 1 mm, and the measurement was performed on a sample that had been mirror-polished on both sides.

(Measurement of fracture toughness)
The fracture toughness of the sample was measured by the IF method by a method according to JIS R1607. As the measurement sample, a sample having a surface roughness Ra of 0.02 μm or less mirror-polished was used. The measurement was performed 5 times for one sample, and the average value was taken as the fracture toughness value of the sample. The measurement conditions in the IF method are as follows.
Push-in weight: 5 kgf
Elastic modulus of sintered body: 205 GPa

Example 1
3 mol% yttria-containing zirconia powder (BET specific surface area 7 m ² / g, trade name: TZ-3YS, manufactured by Toso), lanthanum oxide powder and neodymium oxide (Nd ₂ O ₃ ) powder are mixed in the following proportions. , A mixed powder was obtained.
Zirconia powder containing 3 mol% yttria: 90% by weight
Lanthanum oxide powder: 9% by weight
Neodymium oxide powder: 1% by weight

Mixing was carried out in an ethanol solvent for 120 hours by a ball mill using zirconia balls having a diameter of 10 mm. The obtained mixed powder was dried in the air at 80 ° C. to obtain a raw material powder.

The raw material powder is molded by uniaxial pressure with a mold press having a molding pressure of 50 MPa to obtain a preformed body, and then this is subjected to a cold hydrostatic press (hereinafter referred to as "CIP") at 200 MPa. , A columnar molded body having a diameter of 20 mm and a thickness of about 3 mm was obtained.

The obtained molded product was first sintered in the air at a heating rate of 100 ° C./h, a sintering temperature of 1450 ° C., and a sintering time of 2 hours to obtain a primary sintered body. The obtained primary sintered body was placed in a container made of zirconia with a lid, and this was subjected to HIP treatment to obtain a HIP-treated body.

The HIP treatment conditions were a heating rate of 600 ° C./h, a HIP temperature of 1750 ° C., a HIP pressure of 150 MPa, and a holding time of 1 hour in a 99.9% argon gas atmosphere as a pressure medium.

After the HIP treatment, the temperature was lowered from the sintering temperature to room temperature to obtain a HIP-treated product. The temperature lowering rate from the HIP temperature to 1000 ° C. was 83 ° C./min.

The obtained HIP-treated product was heat-treated in the air at 1000 ° C. for 1 hour to obtain a zirconia sintered body of this example. The physical characteristics of the zirconia sintered body of this example are shown in Table 1, and the evaluation results are shown in Table 2.

The appearance of this embodiment is shown in FIG. From FIG. 1, a diagram of the back surface can be confirmed through the zirconia sintered body of this example, and it can be confirmed that the zirconia sintered body of this example has translucency and transparency. The sintered body has ^{a light blue hue with a brightness L *} of 79.0, a hue a ^* of 1.03 and b ^* of 3.14, and has a maximum total light transmittance of 71.4% (measurement wavelength). : 710 nm) and the maximum value of linear transmittance was 53.4% (measurement wavelength: 770 nm), and it was a blue translucent zirconia sintered body having high transparency.

The Rietveld analysis results of the zirconia sintered body of this example are shown in FIG. From FIG. 2, it can be confirmed that the zirconia sintered body of this example does not contain lanthanum oxide or the like.

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 62.4% by weight of cubic crystals and 37.6% by weight of tetragonal crystals, and the crystallite diameter is 22 nm for cubic crystals and 22 nm for tetragonal crystals. It was 22 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51801 nm for cubic crystals, af = 0.51065 nm and cf = 0.52041 nm for tetragonal crystals. The Rietveld analysis showed reliability factors Rwp = 26% and S = 1.41. The average crystal grain size was 132 μm.

The lattice constant of the 8 mol% yttria solid solution translucent zirconia sintered body having a cubic fluorite-type crystal phase was a = 0.51383 nm. Since the lattice constant of the zirconia sintered body of this example is larger than that of the cubic zirconia sintered body, it was confirmed that lantern and neodymium were solidly dissolved in the zirconia sintered body of this example. ..

Further, the biaxial bending strength was 880 MPa, and it was confirmed that the zirconia sintered body of this example had both strength and translucency.

Example 2
The zirconia sintered body of this example was obtained in the same manner as in Example 1 except that the _{placeodymium oxide (Pr 6} O ₁₁ ) powder was used instead of the neodymium oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 1, and the evaluation results are shown in Table 2.

The sintered body has ^{a yellow hue with a brightness L *} of 75.1, a hue a ^* of 3.9 and a b ^* of 73.8, and has a maximum total light transmittance of 73.5% (measurement wavelength:: It was a yellow translucent zirconia sintered body having high transparency (800 nm) and a maximum value of linear transmittance of 42.5% (measurement wavelength: 800 nm).

According to the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 60.9% by weight of cubic crystals and 39.1% by weight of tetragonal crystals, and the crystallite diameter is 17 nm for cubic crystals and 17 nm for tetragonal crystals. It was 17 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51628 nm for cubic crystals, af = 0.50999 nm and cf = 0.52079 nm for tetragonal crystals. The average crystal grain size was 144 μm.

Example 3
The zirconia sintered body of this example was obtained in the same manner as in Example 1 except that _{erbium oxide (Er 2} O ₃ ) powder was used instead of neodymium oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 1, and the evaluation results are shown in Table 2.

The sintered body has ^{a light pink color tone with a brightness L *} of 83.4, a hue a ^* of 5.6 and a b ^* of 5.5, and the maximum value of total light transmittance is 73.5% (measurement). It was a pink translucent zirconia sintered body having a wavelength: 800 nm) and a maximum value of linear transmittance of 47.4% (measurement wavelength: 800 nm) and having high transparency.

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 78.7% by weight of cubic crystals and 21.3% by weight of tetragonal crystals, and the crystallite diameter is 82 nm for cubic crystals and 82 nm for tetragonal crystals. It was 28 nm, and the tetragonal crystallite diameter was 1.05 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51833 nm for cubic crystals, af = 0.51040 nm and cf = 0.52014 nm for tetragonal crystals. The average crystal grain size was 132 μm.

Example 4
_{The same method as in Example 1 except that cerium oxide (CeO 2} ) powder was used instead of neodymium oxide powder, the primary sintering temperature was set to 1475 ° C., and no heat treatment was performed after the HIP treatment. The zirconia sintered body of this example was obtained. The physical characteristics of the zirconia sintered body of this example are shown in Table 1, and the evaluation results are shown in Table 2.

The sintered body has ^{a red color tone of 47.9 for brightness L *} , 56.9 for hue a ^{* and 78.7 for b *, and} has a maximum total light transmittance of 73.3% (measured). It was a red translucent zirconia sintered body having a wavelength (wavelength: 800 nm).

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 52.4% by weight of cubic crystals and 47.6% by weight of tetragonal crystals, and the crystallite diameter is 24 nm for cubic crystals and 47.6% by weight for tetragonal crystals. It was 24 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51834 nm for cubic crystals, af = 0.51047 nm and cf = 0.52014 nm for tetragonal crystals. The average crystal grain size was 39 μm.

From Tables 1 and 2, it can be seen that the zirconia sintered bodies of all the examples have a total light transmittance of more than 70% and have high translucency. Further, although these sintered bodies contain a coloring component, the crystallite diameters of tetragonal and cubic crystals are sufficiently small. The crystallite diameters of tetragonal and cubic crystals obtained from Rietveld analysis tended to be smaller than the average crystallite diameter obtained from FWHM, but it was confirmed that both were about the same size. As described above, the zirconia sintered body of the present invention has crystal particles composed of a tetragonal domain and a cubic domain sufficiently smaller than the wavelength of visible light, and therefore has high translucency and high transparency. Conceivable.

Example 5
The zirconia sintered body of this example was obtained in the same manner as in Example 1 except that _{iron oxide (Fe 2} O ₃ ) powder was used instead of neodymium oxide powder and the mixed powder had the following composition. .. The physical characteristics of the zirconia sintered body of this example are shown in Table 3, and the evaluation results are shown in Table 4.
Zirconia powder containing 3 mol% yttria: 90.0% by weight
Lanthanum oxide powder: 9.95% by weight
Iron oxide powder: 0.05% by weight
The sintered body has ^{a light blue hue with a brightness L *} of 75.4, a hue a ^* of 0.4 and a b ^* of 20.9, and has a maximum total light transmittance of 70.0% (measurement wavelength). : 800 nm) and the maximum value of linear transmittance was 54.0% (measurement wavelength: 800 nm), and it was a blue translucent zirconia sintered body having high transparency.

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 78.5% by weight of cubic crystals and 21.5% by weight of tetragonal crystals, and the crystallite diameter is 22 nm for cubic crystals and 22 nm for tetragonal crystals. It was 22 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51696 nm for cubic crystals, af = 0.51044 nm and cf = 0.52009 nm for tetragonal crystals. The average crystal grain size was 93 μm.

Example 6
A zirconia sintered body of this example was obtained in the same manner as in Example 5 except that manganese oxide (MnO) powder was used instead of iron oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 3, and the evaluation results are shown in Table 4.

Sintered body lightness ^{L *} of 33.0, a hue ^{a *} is 23.7 and ^{b *} exhibits the color tone of purple -12.9, the maximum value of the total light transmittance of 57.2% (measured wavelength : 800 nm) and the maximum value of linear transmittance was 40.5% (measurement wavelength: 800 nm), and it was a purple translucent zirconia sintered body having high transparency.

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 65.6% by weight of cubic crystals and 34.5% by weight of tetragonal crystals, and the crystallite diameter is 19 nm for cubic crystals and 19 nm for tetragonal crystals. It was 19 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51697 nm for cubic crystals, af = 0.50992 nm and cf = 0.52129 nm for tetragonal crystals. The average crystal grain size was 86 μm.

Example 7
A zirconia sintered body of this example was obtained in the same manner as in Example 5 except that _{chromium oxide (Cr 2} O ₃ ) powder was used instead of iron oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 3, and the evaluation results are shown in Table 4.

The sintered body has ^{an amber color tone with a brightness L *} of 46.4, a hue a ^* of 17.2 and a b ^* of 33.2, and has a maximum total light transmittance of 67.4% (measurement wavelength). : 800 nm) and the maximum value of linear transmittance was 55.9% (measurement wavelength: 800 nm), and it was an amber color translucent zirconia sintered body having high transparency.

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 55.6% by weight of cubic crystals and 44.4% by weight of tetragonal crystals, and the crystallite diameter is 31 nm for cubic crystals and 31 nm for tetragonal crystals. It was 30 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51878 nm for cubic crystals, af = 0.51046 nm and cf = 0.52015 nm for tetragonal crystals. The average crystal grain size was 112 μm.

Example 8
A zirconia sintered body of this example was obtained in the same manner as in Example 5 except that copper oxide (CuO) powder was used instead of iron oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 3, and the evaluation results are shown in Table 4.

The sintered body has ^{an orange color tone of 58.4 lightness L *} , 12.5 hue a ^{* and 46.7 b *, and} has a maximum total light transmittance of 54.2% (54.2%). It was an orange translucent zirconia sintered body having a measurement wavelength (measurement wavelength: 800 nm).

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 51.6% by weight of cubic crystals and 48.4% by weight of tetragonal crystals, and the crystallite diameter is 12 nm for cubic crystals and 48.4% by weight for tetragonal crystals. It was 11 nm, and the tetragonal crystallite diameter was 1.09 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51962 nm for cubic crystals, af = 0.51044 nm and cf = 0.52014 nm for tetragonal crystals. The average crystal grain size was 92 μm.

Example 9
A zirconia sintered body of this example was obtained in the same manner as in Example 5 except that copper oxide (CuO) powder was used instead of iron oxide powder. The physical characteristics of the zirconia sintered body of this example are shown in Table 3, and the evaluation results are shown in Table 4.

The sintered body has ^{a blue hue with a brightness L *} of 62.3, a hue a ^* of 1.5 and b ^* of 28.1, and has a maximum total light transmittance of 62.7% (measurement wavelength:: It was a blue translucent zirconia sintered body having high transparency with a maximum value of 48.8% (measurement wavelength: 800 nm) and a linear transmittance (800 nm).

From the Rietbelt analysis, the crystal phase of the zirconia sintered body of this example contains 61.4% by weight of cubic crystals and 48.4% by weight of tetragonal crystals, and the crystallite diameter is 18 nm for cubic crystals and 48.4% by weight for tetragonal crystals. It was 18 nm, and the tetragonal crystallite diameter was 1.0 with respect to the cubic crystallite diameter. The lattice constants were a = 0.51879 nm for cubic crystals, af = 0.51044 nm and cf = 0.52014 nm for tetragonal crystals. The average crystal grain size was 98 μm.

From Tables 3 and 4, it was found that even in the case of a zirconia sintered body containing a transition metal as a coloring component, a zirconia sintered body containing crystal particles composed of a tetragonal domain and a cubic domain can be obtained. It was confirmed that each of the sintered bodies had a total light transmittance of more than 50% and a biaxial bending strength of more than 600 MPa, and exhibited a coloration other than colorless.

Comparative Example 1
3 mol% yttria-containing zirconia powder (BET specific surface area 7 m ² / g, trade name: TZ-3YS, manufactured by Toso) and erbium oxide (Er ₂ O ₃ ) powder are mixed in the following proportions, and the mixed powder is mixed. Obtained.
Zirconia powder containing 3 mol% yttria: 99% by weight
Erbium oxide powder: 1% by weight
A zirconia sintered body of this comparative example was obtained in the same manner as in Example 1 except that the obtained mixed powder was used.

The obtained zirconia sintered body has a composition of 96.68 mol% of zirconia, 2.99 mol% of yttria, and 0.33 mol% of erbium oxide in terms of oxide (0.66 mol% in terms of specific oxide), which is square. It had a crystal structure with crystals as the main phase, the average crystallite diameter was 276 nm, and the average crystal grain size was 19.3 μm. The maximum value of the total light transmittance was 43.6%, which was low in translucency and was colored pink.

Comparative Example 2
3 mol% itria-containing zirconia powder (BET specific surface area 7 m ² / g, trade name: TZ-3YS, manufactured by Toso) and iron oxide (Fe ₂ O ₃ ) powder are mixed in the following proportions, and the mixed powder is mixed. Obtained.
Zirconia powder containing 3 mol% yttria: 99.5% by weight
Iron oxide powder: 0.5% by weight
A zirconia sintered body of this comparative example was obtained in the same manner as in Example 1 except that the obtained mixed powder was used.

The obtained zirconia sintered body has a composition of 96.61 mol% of zirconia, 2.99 mol% of yttria, and 0.4 mol% of iron oxide in terms of oxide (0.8 mol% in terms of specific oxide), and is a square crystal. The crystal structure was mainly composed of, and the average crystallite diameter was 284 nm and the average crystal grain size was 1.6 μm. The maximum value of the total light transmittance was 39.2%, which was low in translucency and was colored light brown.

The zirconia sintered body of the present invention has both high translucency and high strength. Therefore, it can be used for dental members such as dental prosthetic materials and orthodontic members that require aesthetics. Further, since the zirconia sintered body of the present invention has a high design property, it can be used as a decorative member for watches, jewelry and the like, and further, it can be used as a plasma resistant member for a member for a semiconductor manufacturing apparatus. ..

Claims (9)

Containing crystal particles having a cubic domain and a tetragonal domain , at least one of the group consisting of itria, scandia, calcia, and magnesia as a stabilizer and lanthanum are solid-dissolved, and a lanthanoid or transition metal other than lanthanum is dissolved. A zirconia sintered body containing at least one of them. The zirconia sintered body according to claim 1, wherein the average crystallite diameter calculated from the half width of 2θ = 30 ± 2 ° in the powder X-ray diffraction pattern using CuKα as a radiation source is 255 nm or less. The zirconia sintered body according to claim 1 or 2, wherein the content of at least one of a lanthanoid other than lanthanum or a transition metal is 0.01 wt% or more and 5 wt% or less. The zirconia sintered body according to any one of claims 1 to 3, wherein the lanthanum content is 1 mol% or more and 10 mol% or less. The zirconia sintered body according to any one of claims 1 to 4 , wherein the bending strength is 500 MPa or more. The zirconia sintered body according to any one of claims 1 to 5 , wherein the maximum value of the total light transmittance at a sample thickness of 1 mm and a measurement wavelength of 300 to 800 nm is 45% or more. A mixing step of mixing at least one of a lanthanoid raw material or a transition metal raw material other than lantern, a zirconia raw material, a stabilizer raw material, and a lanthanum raw material to obtain a mixed powder, and a molding step of molding the obtained mixed powder to obtain a molded product. , A sintering step of sintering the obtained molded product at a sintering temperature of 1650 ° C. or higher to obtain a sintered body, and a temperature reduction in which the temperature from the sintering temperature to 1000 ° C. is lowered at a temperature lowering rate of 5 ° C./min or more. The method for producing a zirconia sintered body according to any one of claims 1 to 6 , which comprises a step. 7. The claim 7 includes a primary sintering in which the sintering step obtains a primary sintered body by firing at 1000 ° C. or higher and lower than 1650 ° C., and a secondary sintering in which the primary sintered body is sintered at 1650 ° C. or higher. The manufacturing method described in. A member containing the zirconia sintered body according to any one of claims 1 to 6.

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