CN114195514A

CN114195514A - Zirconia powder, method for producing zirconia sintered body, and zirconia sintered body

Info

Publication number: CN114195514A
Application number: CN202110998087.6A
Authority: CN
Inventors: 高井优行; 金西启太
Original assignee: Daiichi Kigenso Kagaku Kogyo Co Ltd
Current assignee: Daiichi Kigenso Kagaku Kogyo Co Ltd
Priority date: 2020-09-02
Filing date: 2021-08-27
Publication date: 2022-03-18
Also published as: JP2022042315A

Abstract

Provided is a zirconia powder which has excellent moldability and a high sintering density and which can be produced into a colored zirconia sintered body by a simple method. The zirconia powder comprises: zirconia containing yttria in a range of 2 mol% to 6 mol%; and at least one oxide selected from the group consisting of group 4 to group 9, group 12, group 14 and lanthanides, and has a fine pore diameter of 200nm or lessThe pore volume is 0.14-0.28 mL/g, and the molding pressure is 1t/cm²The relative molding density during molding is 44-55%.

Description

Zirconia powder, method for producing zirconia sintered body, and zirconia sintered body

Technical Field

The present invention relates to a zirconia powder, a method for producing a zirconia sintered body, and a zirconia sintered body.

Background

Zirconia sintered bodies, particularly tetragonal zirconia sintered bodies, have been used for household goods such as tools and sports goods such as golf spikes because of their high strength and good surface gloss after mirror polishing, and further, have been used for decorative parts such as watch cases and ornaments. In order to cope with such an expansion of use, zirconia having various colors is strongly required.

Under the above background, various colored ceramics for decorative parts have been proposed. For example, patent document 1 discloses a black zirconia sintered body composed of (a)98 to 67 mol% of ZrO₂1.5 to 26 mol% of a stabilizer, and 0.3 to 1.5 mol% of MnO_4/3And (d)0.1 to 3.5 mol% of Al₂O₃And (e) is selected from the group consisting of CoO and Cr₂O₃、Fe₂O₃、TiO₂0.1 to 2.0 mol% of one or more oxides of the group.

Patent document 2 discloses a stabilizer-containing ZrO₂0.5 to 2.0 mol% of Er₂O₃And 0.1 to 0.6 mol% of ZnO.

Patent document 3 discloses a stabilizer-containing ZrO₂0.01 to 0.1 mol% of Pr₆O₁₁And 0.1 to 0.6 mol% of ZnO.

The zirconia sintered body is produced by molding zirconia powder and then sintering the molded body. At this time, the zirconia powder is stabilized in advance. By performing the stabilization treatment, the crystal structure of a tetragonal system or a cubic system, which is a high-temperature stable phase of the zirconia crystal, can be maintained at normal temperature. The stabilizing treatment of the zirconia crystal is usually performed by dissolving oxides such as calcium oxide, magnesium oxide, and yttrium oxide in zirconia as a solid solution.

Sintered bodies composed of zirconia formed only of a cubic crystal structure are widely used as so-called fully stabilized zirconia (generally referred to as "stabilized zirconia") sintered bodies. Further, sintered bodies containing zirconia having a tetragonal crystal structure are widely used as partially stabilized zirconia sintered bodies. In the case of obtaining the above zirconia sintered body, the characteristics of the powder affect the operation and sintering characteristics at the time of production. Therefore, the characteristics of the obtained zirconia sintered body greatly depend on the characteristics of the zirconia powder as the raw material.

For example, patent document 4 discloses a zirconia powder containing 2 to 6 mol% of yttria, having a pore volume of 0.14 to 0.28mL/g and a pore diameter of 200nm or less, and molded at a molding pressure of 1t/cm²The relative molding density of the resin composition represented by the following formula (1) during molding is 44-55%.

Relative molding density (%) (molding density/theoretical sintered density) × 100 · (1)

Patent document 4 discloses the following: the zirconia powder has a high molding density at the time of molding, and can give a sintered body having a sintered density of 99.5% or more with respect to a theoretical sintered density.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 4-114964

Patent document 2: japanese laid-open patent publication No. 4-2658

Patent document 3: japanese laid-open patent publication No. 4-2657

Patent document 4: international publication No. 2017/170565

Disclosure of Invention

Problems to be solved by the invention

As described in patent documents 1 to 3, colored zirconia sintered bodies (hereinafter, also referred to as colored zirconia sintered bodies) and powders have been conventionally known. On the other hand, there has been no example in which the moldability in obtaining a colored zirconia sintered body has been studied in detail. As described in patent documents 1 to 3, in general, in molding for obtaining a colored zirconia sintered body, 2t/cm is required as a molding pressure²On the other hand, there is a problem of high process load.

In order to obtain a colored zirconia sintered body, it is generally necessary to press zirconia powder by press molding or the like to prepare a green compact, i.e., a molded body, and then sinter the molded body, but the properties of zirconia powder are greatly affected in the molding step for preparing the molded body. In order to obtain a colored zirconia sintered body having a high sintered density and sintered body strength, it is necessary to reduce defects and density unevenness in the formed body and to make the formed body have a higher density. In the press molding step, it is important to reduce friction with the wall surface of the mold during molding and to reduce friction between powder particles. When the friction is large, defects such as delamination and cracks occur in the molded body, and if the friction is large, the molding pressure is hard to propagate between particles, and a molded body with a high molding density cannot be obtained. Further, in the case of using injection molding, extrusion molding, cast molding, or the like, deformation of a molded body, cracking of a sintered body due to unevenness of molding density, or the like occurs, and in the case of using sheet molding, the molding density cannot be increased, the sheet strength is lowered, and the workability is often deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to provide a zirconia powder which is excellent in moldability, has a high sintering density, and can produce a colored zirconia sintered body by a simple method. Also disclosed is a method for producing a zirconia sintered body using such a zirconia powder. Also disclosed is a zirconia sintered body produced using such a zirconia powder.

Means for solving the problems

The present inventors have made extensive studies to achieve the above object, and as a result, have found that the above object can be achieved by controlling the degree of aggregation of primary particles in a state in which an oxide for coloring is dispersed within a specific range, and have completed the present invention.

Namely, the zirconia powder of the present invention comprises:

zirconia containing yttria in a range of 2 mol% to 6 mol%; and

one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14 and lanthanoid elements,

the pore volume of the pores having a diameter of 200nm or less is 0.14 to 0.28mL/g,

at a molding pressure of 1t/cm²The relative molding density of the resin composition represented by the following formula (1) during molding is 44-55%.

According to the above configuration, the pore volume of pores having a pore diameter of 200nm or less is 0.14 to 0.28mL/g, and therefore, the molding density is high during molding. Therefore, the zirconia powder is suitable for various molding methods such as press molding, injection molding, cast molding, sheet molding, and the like. Further, the zirconia powder is easy to mass-produce, and therefore, is excellent in cost competitiveness, and can be suitably used for various applications. Further, since the relative molding density is 44 to 55%, a sintered body having a high sintering density can be obtained. In addition, since the sintered body contains one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements, the sintered body can be colored.

Thus, according to the zirconia powder of the present invention, the degree of aggregation of the primary particles in a state in which the coloring oxide is dispersed is controlled within a specific range, whereby a colored zirconia sintered body can be produced by a simple method while having excellent moldability and a high sintering density.

In the above configuration, it is preferable that the groups 4 to 9 are one or more selected from the group consisting of Ti, V, Cr, Mn, Fe, and Co, the group 12 is Zn, the group 14 is Si, and the lanthanoid element is one or more selected from the group consisting of Er, Tb, and Pr. In addition, in the case of coloring, a combination of elements and an addition amount suitable for the combination are included, which will be described later.

In the above constitution, the specific surface area is preferably 5 to 20m²/g，

The average particle size is 0.3 to 0.8 μm.

When the specific surface area of the zirconia powder is in the above range, a molded body having a high molding density can be easily obtained, and the reduction of sinterability and sintering density can be easily suppressed.

Further, if the average particle diameter of the zirconia powder is within the above range, a molded body having a high molding density can be easily obtained, and the sinterability and the reduction in the sintered density can be easily suppressed.

In the above constitution, alumina is preferably contained.

When the zirconia powder contains alumina, the sinterability of the zirconia powder is improved, and the crystal structure is easily made uniform. Further, since the zirconia powder contains alumina, it is easy to suppress a decrease in fracture toughness of the zirconia sintered body.

In the above constitution, it is preferable that the molding pressure is 1t/cm²The relative sintered density when the molded article is sintered at 1450 ℃ for 2 hours is 99.5% or more.

When the relative sintered density is 99.5% or more, the sintered density is said to be high.

In the above composition, it is preferable that the oxide contains 0.4 to 1.0 mass% of Fe₂O₃0.9 to 1.5 mass% of CoO, 1.0 to 1.6 mass% of Cr₂O₃0.5 to 0.9 mass% of TiO₂. When the colorant is contained in the above range, preferable color development is obtained.

In the above constitution, it is preferable that the oxide contains 0.9 to 1.5 mass% of CoO and 1.0 to 1.6 mass% of Cr₂O₃0.8 to 1.4 mass% of MnO₂. When the colorant is contained in the above range, preferable color development is obtained.

In the above configuration, it is preferable that 0.15 to 0.35 mass% of ZnO be contained as the oxide. When the colorant is contained in the above range, preferable color development is obtained.

In the above composition, the oxide preferably contains 0.02 to 0.1 mass% of Cr₂O₃. When the colorant is contained in the above range, preferable color development is obtained.

In the above constitution, it is preferable that the content of alumina is less than 0.005 mass%,

the oxide contains 0.03 to 0.06 mass% of MnO₂. Such asIf the colorant is contained in the above range, preferable color development is obtained.

In the above constitution, the content of alumina is preferably 0.005 mass% or more and 2 mass% or less,

the oxide contains 0.02 to 0.05 mass% of MnO₂. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.2 to 0.5 mass% of MnO₂. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.12-0.40 mass% of Fe₂O₃. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.12-0.23 mass% of Fe₂O₃. When the colorant is contained in the above range, preferable color development is obtained.

In the above constitution, it is preferable that the content of alumina is 1 mass% or more and 3 mass% or less,

the oxide contains 0.3 to 1.0 mass% of CoO. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.20 to 0.60 mass% of Pr₆O₁₁. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.03 to 0.30 mass% of SiO₂. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.3 to 1.0 mass% of CoO and 0.05 to 0.25 mass% of Cr₂O₃0.03 to 0.2 mass% of MnO₂. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 0.2 to 0.8 mass% of CoO and 0.26 to 0.7 mass% of Cr₂O₃0.21 to 0.4 mass% of MnO₂. When the colorant is contained in the above range, preferable color development is obtained.

In the above constitution, the content of alumina is preferably 1.5 mass% or more and 4 mass% or less,

the oxide contains 0.1 to 0.5 mass% of Fe₂O₃1 to 2 mass% of CoO, 0.3 to 0.9 mass% of Cr₂O₃0.2 to 0.4 mass% of TiO₂. When the colorant is contained in the above range, preferable color development is obtained.

In the above-described configuration, the content of alumina is preferably 0.5 mass% or more and 2.5 mass% or less,

the oxide contains 0.02-1 mass% of Fe₂O₃1 to 2 mass% of CoO, 0.03 to 0.3 mass% of Cr₂O₃0.01 to 0.1 mass% of TiO₂. When the colorant is contained in the above range, preferable color development is obtained.

the oxide contains 1.05 to 2 mass% of CoO. When the colorant is contained in the above range, preferable color development is obtained.

Further, a method for producing a zirconia sintered body of the present invention includes:

a step X of molding the zirconia powder to obtain a molded body;

and a step Y of sintering the molded body after the step X.

The zirconia powder disperses an oxide for coloring, is excellent in moldability, and has a high sintering density. Therefore, according to the method for producing a zirconia sintered body using the zirconia powder, a colored zirconia sintered body having a high sintering density can be produced.

The zirconia sintered body of the present invention contains one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements, and is obtained by the above-described production method.

The zirconia sintered body of the present invention is obtained by the method for producing a zirconia sintered body, and therefore has a high sintering density. Further, since the sintered body contains one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements, the sintered body is colored. That is, according to the zirconia sintered body of the present invention, a colored zirconia sintered body having a high sintering density can be provided.

In the above configuration, when the zirconia sintered body is colored black, it is preferable that 0.4 to 1.0 mass% of Fe is contained₂O₃0.9 to 1.5 mass% of CoO, 1.0 to 1.6 mass% of Cr₂O₃0.5 to 0.9 mass% of TiO₂In the L × a × b color system, L is defined to be-1 to 13, a is-7 to 7, and b is-8 to 6. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-mentioned structure, when the zirconia sintered body is colored to be black of different systems, it is preferable that 0.9 to 1.5 mass% of the zirconia sintered body is containedCoO and 1.0-1.6 mass% Cr₂O₃0.8 to 1.4 mass% of MnO₂In the L × a × b color system, L is defined to be 1 to 17, a is-9 to 5, and b is-8 to 6. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in white, it is preferable that 0.15 to 0.35 mass% of ZnO be contained, and L defined in a la b color system is 80 to 96, a is-7 to 7, and b is-6 to 8. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-mentioned structure, when the zirconia sintered body is colored in a gray color, it is preferable that 0.02 to 0.1 mass% of Cr is contained₂O₃In the L × a × b color system, L is 30 to 52, a is-5 to 8, and b is 0 to 20. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a gray color, it is preferable that MnO is contained in an amount of 0.03 to 0.06 mass% under the condition that the alumina content is less than 0.005 mass% (under the condition that the alumina is not substantially contained)₂In the L × a × b color system, L is defined to be 28 to 44, a is-3 to 8, and b is-8 to 8. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a gray color, it is preferable that MnO is contained in an amount of 0.02 to 0.05 mass% under the condition that the alumina content is 0.005 mass% to 2 mass%, respectively₂In the L, a, b, and the color system, L is not less than 31 and not more than 47A is-4 to 12 inclusive, and b is-9 to 7 inclusive. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored black, it is preferable that MnO is contained in an amount of 0.2 to 0.5 mass% under the condition that the alumina content is 0.005 mass% or more and 2 mass% or less₂In the L × a × b color system, L is 1 to 23, a is-5 to 11, and b is-10 to 6. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored brown, it is preferable that 0.12 to 0.40 mass% of Fe is contained under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂O₃In the L × a × b color system, L is defined to be 55 to 75, a is-2 to 17, and b is 18 to 40. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored brown, it is preferable that 0.12 to 0.23 mass% of Fe is contained under the condition that the content of alumina is less than 0.005 mass% (under the condition that alumina is not substantially contained)₂O₃In the L × a × b color system, L × defined is 41 to 61, a × is 2 to 18, and b × is 18 to 38. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a blue color, it is preferable that 0.3 to 1.0 mass% of CoO is contained under the condition that the content of alumina is 1 mass% or more and 3 mass% or less, and L x defined in a la b color system is 22 to 44, a is-10 to 7, and b is-50 to 28. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a yellow color, it is preferable that 0.20 to 0.60 mass% of Pr is contained under the condition that the alumina content is 0.005 mass% or more and 2 mass% or less₆O₁₁In the L × a × b color system, L is defined to be 55 to 75, a is 4 to 20, and b is 40 to 60. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a white color, it is preferable that 0.03 to 0.30 mass% of SiO is contained under the condition that the alumina content is 0.005 mass% or more and 2 mass% or less₂In the L × a × b color system, L is defined to be 77 or more and 97 or less, a is-5 or more and 5 or less, and b is-5 or more and 5 or less. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above configuration, when the zirconia sintered body is colored in a deep blue color, it is preferable that the zirconia sintered body contains 0.3 to 1.0 mass% of CoO and 0.05 to 0.25 mass% of Cr under the condition that the alumina content is 1 to 3 mass% inclusive₂O₃0.03 to 0.2 mass% of MnO₂In the L × a × b color system, L is defined to be 13 to 33, a is-12 to-2, and b is-29 to-19. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-mentioned constitution, when the zirconia sintered body is colored in a deep blue color, it is preferable that the zirconia sintered body contains 0.2 to up to 3 mass% of alumina under the condition that the content of alumina is 1 to up to 3 mass%0.8 mass% of CoO, and 0.26-0.7 mass% of Cr₂O₃0.21 to 0.4 mass% of MnO₂In the L x a b color system, L x is 8 to 28, a x is-14 to-4, and b x is-21 to-11. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above configuration, when the zirconia sintered body is colored in a deep blue color, it is preferable that 0.1 to 0.5 mass% of Fe is contained under the condition that the alumina content is 1.5 to 4 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.3 to 0.9 mass% of Cr₂O₃0.2 to 0.4 mass% of TiO₂In the L x a b color system, L x is 27 to 48, a x is-6 to 4, and b x is-10 to-1. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above configuration, when the zirconia sintered body is colored in a deep blue color, it is preferable that 0.02 to 1 mass% of Fe is contained under the condition that the alumina content is 0.5 to 2.5 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.03 to 0.3 mass% of Cr₂O₃0.01 to 0.1 mass% of TiO₂In the L x a b color system, L x is 27 to 48, a x is-6 to 4, and b x is-10 to-1. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

In the above-described configuration, when the zirconia sintered body is colored in a deep blue color, it is preferable that the zirconia sintered body contains 1.05 to 2 mass% of CoO under the condition that the content of alumina is 1 to 3 mass%, and L defined in the laabb color system is 27 to 48, a is-5 to 6, and b is-12 to-2. When the oxide is contained in the above range, L, a, b defined in the colorimetric system are easily within the above numerical range, and preferred color development is easily achieved.

Effects of the invention

According to the present invention, a zirconia powder which is excellent in moldability, has a high sintering density, and can be produced into a colored zirconia sintered body by a simple method can be provided. Further, a method for producing a zirconia sintered body using the zirconia powder can be provided. Further, a zirconia sintered body produced using the zirconia powder can be provided.

Detailed Description

Embodiments of the present invention will be described below. However, the present invention is not limited to these embodiments. In the present specification, zirconia is a general zirconia and contains 10% by weight or less of an impurity metal compound containing hafnium oxide. In the present specification, expressions "including" and "containing" include concepts of "including", "containing", "substantially constituting" and "consisting of only".

[ zirconia powder ]

The zirconia powder of the present embodiment includes:

zirconia containing yttria in a range of 2 mol% to 6 mol%; and

The zirconia powder contains primary particles containing zirconia as a main component. All or a part of the primary particles are aggregated to form secondary particles. That is, the zirconia powder contains unagglomerated primary particles and agglomerated secondary particles of the primary particles.

However, in the above-mentioned zirconia powder, the amount of primary particles that are not secondary particles but exist in a state of unagglomerated primary particles is extremely small, for example, less than 1 mass% of the entire primary particles (the total amount of unagglomerated primary particles and primary particles that are agglomerated to become secondary particles). That is, the zirconia powder may contain a very small amount of unagglomerated primary particles, but most of the zirconia powder is composed of secondary particles.

The zirconia powder contains zirconia. The content of the zirconia is preferably 90 mass% or more, more preferably 92 mass% or more, further preferably 94 mass% or more, and particularly preferably 94.3 mass% or more, when the zirconia powder is 100 mass%. The upper limit of the content of zirconia is not particularly limited, but the content of zirconia is preferably 97.5% by mass or less, more preferably 97.2% by mass or less, still more preferably 97% by mass or less, and particularly preferably 96.9% by mass or less.

The zirconia powder contains 2 mol% or more and 6 mol% or less of yttria with respect to the total mol amount of the zirconia. Yttria has the function of acting as a stabilizer. Yttria may be present as a solid solution with zirconia or as a mixture. From the viewpoint of element dispersibility at the time of sintering, yttria preferably exists as a solid solution with zirconia. That is, yttria is preferably present in the form of yttria-stabilized zirconia. Since the content ratio of yttria is 2 mol% or more, the excess ratio of monoclinic phase in the sintered body of zirconia powder can be suppressed. That is, by suppressing propagation of cracks due to large volume expansion caused by phase transition from a tetragonal phase to a monoclinic phase, it is possible to suppress a decrease in fracture toughness of the zirconia sintered body.

The content of yttrium oxide is preferably 2 to 5 mol%, particularly preferably 2 to 4 mol%. In the case where the content ratio of yttria is 3 to 6 mol%, which is another preferable range, a cubic phase having low optical anisotropy is formed, and therefore, a zirconia sintered body having excellent light transmittance can be obtained.

The zirconia powder may contain other components instead of a part of the yttria. Examples of the other components include alkaline earth metal oxides such as calcium oxide and magnesium oxide, and rare earth oxides such as cerium oxide.

The zirconia powder may contain alumina (alumina) as needed. The content of the alumina is not particularly limited, but may be 0.005 to 4.0% by mass, and more preferably 0.005 to 2.0% by mass, based on the total mass of the zirconia powder. In the case where the zirconia powder contains alumina, the sinterability of the zirconia powder is improved and the crystal structure is easily uniformized. Further, since the zirconia powder contains alumina, it is easy to suppress a decrease in fracture toughness of the zirconia sintered body. Further, if the content of alumina is adjusted, the light transmittance of the zirconia sintered body can be improved. The upper limit of the content of alumina is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, further preferably 0.4 mass% or less, and particularly preferably 0.3 mass% or less, with respect to the total mass of the zirconia powder.

The form of alumina is not particularly limited, but alumina powder is preferred from the viewpoint of workability in the production of zirconia powder and reduction of impurity residues.

When the alumina powder is added, the average particle size of the primary particles is not particularly limited, and may be 0.02 to 0.4. mu.m, more preferably 0.05 to 0.3. mu.m, and still more preferably 0.07 to 0.2. mu.m. The average particle diameter of the primary particles of alumina was measured by using a laser diffraction particle diameter distribution measuring apparatus "SALD-2300" (manufactured by Shimadzu corporation).

The zirconia powder contains one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements. Since the zirconia sintered body obtained by sintering the zirconia powder contains, as a colorant, one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements, it is possible to color the zirconia sintered body.

The above-mentioned groups 4 to 9 are preferably at least one selected from the group consisting of Ti, V, Cr, Mn, Fe and Co. The group 12 is preferably Zn. The group 14 is preferably Si. The lanthanoid is preferably one or more selected from the group consisting of Er, Tb, and Pr.

As the above-mentioned oxide, there may be mentionedIn particular, TiO may be mentioned₂、V₂O₅、Cr₂O₃、MnO₂、Fe₂O₃、CoO、ZnO、SiO₂、Er₂O₃、Tb₄O₇、Pr₆O₁₁And the like. The above oxides are preferably added as a mixture to the above zirconia powder.

< first Black color line >

When the zirconia sintered body obtained by sintering is colored black, the oxide preferably contains 0.4 to 1.0 mass% of Fe₂O₃0.9 to 1.5 mass% of CoO, 1.0 to 1.6 mass% of Cr₂O₃0.5 to 0.9 mass% of TiO₂。

Fe as described above₂O₃The content of (b) is more preferably 0.5 to 0.9% by mass, and still more preferably 0.6 to 0.8% by mass.

The content of CoO is more preferably 1.0 to 1.4% by mass, and still more preferably 1.1 to 1.3% by mass.

The above Cr₂O₃The content of (b) is more preferably 1.1 to 1.5% by mass, and still more preferably 1.2 to 1.4% by mass.

The above TiO compound₂The content of (b) is more preferably 0.55 to 0.85 mass%, and still more preferably 0.6 to 0.8 mass%.

When the colorant is contained within the above range, preferable color development is obtained.

< second Black color line >

When the zirconia sintered body obtained by sintering is colored in a black system different from the first black system, the oxide preferably contains 0.9 to 1.5 mass% of CoO and 1.0 to 1.6 mass% of Cr₂O₃0.8 to 1.4 mass% of MnO₂。

MnO as described above₂The content of (b) is more preferably 0.9 to 1.3% by mass, and still more preferably 1.0 to 1.2% by mass.

< third Black line >

When the zirconia sintered body obtained by sintering is colored in a black system different from the first and second black systems, it is preferable that the oxide contains 0.2 to 0.5 mass% of MnO under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂。

MnO as described above₂The content of (b) is more preferably 0.25 to 0.45 mass%, and still more preferably 0.3 to 0.4 mass%.

< first white color line >

When the zirconia sintered body obtained by sintering is colored in a white color, the oxide preferably contains 0.15 to 0.35 mass% of ZnO.

The content of ZnO is more preferably 0.2 to 0.3 mass%, and still more preferably 0.22 to 0.28 mass%.

< second white color line >

When the zirconia sintered body obtained by sintering is colored in a white color, it is preferable that the oxide contains 0.03 to 0.30 mass% of SiO under the condition that the content of alumina is 0.005 to 2 mass%, and the content of SiO is 0.03 to 0.30 mass%₂。

The above SiO₂The content of (b) is more preferably 0.05 to 0.2 mass%, and still more preferably 0.07 to 0.13 mass%.

< first gray color line >

When the zirconia sintered body obtained by sintering is colored in a gray systemUnder the condition that the content of alumina is less than 0.005 mass% (under the condition that alumina is not substantially contained), MnO is preferably contained in an amount of 0.03 to 0.06 mass% as the oxide₂。

MnO as described above₂The content of (b) is more preferably 0.035 to 0.055 mass%, and still more preferably 0.04 to 0.05 mass%.

< second gray color line >

When the zirconia sintered body obtained by sintering is colored in a gray color, it is preferable that the oxide contains 0.02 to 0.05 mass% of MnO under the condition that the content of alumina is 0.005 to 2 mass%, and₂。

MnO as described above₂The content of (b) is more preferably 0.025 to 0.045% by mass, and still more preferably 0.03 to 0.04% by mass.

< third gray color line >

When the zirconia sintered body obtained by sintering is colored in a gray color, it is preferable that 0.02 to 0.1 mass% of Cr is contained₂O₃。

The above Cr₂O₃The content of (b) is more preferably 0.04 to 0.08% by mass, and still more preferably 0.05 to 0.07% by mass.

< first brown line >

When the zirconia sintered body obtained by sintering is colored brown, the oxide preferably contains 0.12 to 0.23 mass% of Fe under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂O₃。

Fe as described above₂O₃The content of (b) is more preferably 0.14 to 0.21% by mass, and still more preferably 0.16 to 0.2% by mass.

< second brown line >

When the zirconia sintered body obtained by sintering is colored brown, the oxide preferably contains 0.12 to 0.23 mass% of Fe under the condition that the content of alumina is less than 0.005 mass% (under the condition that alumina is not substantially contained)₂O₃。

< third brown line >

When the zirconia sintered body obtained by sintering is colored into a brown system having a darker color than the first brown color, it is preferable that 0.23 to 0.40 mass% of Fe is contained under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂O₃。

Fe as described above₂O₃The content of (b) is more preferably 0.25 to 0.35% by mass, and still more preferably 0.28 to 0.32% by mass.

< blue color system >

When the zirconia sintered body obtained by sintering is colored in a blue color, it is preferable that the content of CoO is 0.3 to 1.0 mass% under the condition that the content of alumina is 1 to 3 mass%.

The content of CoO is more preferably 0.4 to 0.8% by mass, and still more preferably 0.5 to 0.7% by mass.

< yellow color series >

When the zirconia sintered body obtained by sintering is colored in a yellow color, the content of alumina is preferably 0.20 to 0% by mass under the condition that the content is 0.005% by mass or more and 2% by mass or less.60 mass% of Pr₆O₁₁。

The above Pr₆O₁₁The content of (b) is more preferably 0.30 to 0.50 mass%, and still more preferably 0.35 to 0.45 mass%.

< first deep blue color family >

When the zirconia sintered body obtained by sintering is colored in a deep blue color, the oxide preferably contains 0.3 to 1.0 mass% of CoO and 0.05 to 0.25 mass% of Cr under the condition that the alumina content is 1 to 3 mass% inclusive₂O₃0.03 to 0.2 mass% of MnO₂。

The content of CoO is more preferably 0.4 to 0.8% by mass, and still more preferably 0.5 to 0.6% by mass.

The above Cr₂O₃The content of (b) is more preferably 0.08 to 0.2% by mass, and still more preferably 0.1 to 0.15% by mass.

MnO as described above₂The content of (b) is more preferably 0.05 to 0.15% by mass, and still more preferably 0.08 to 0.12% by mass.

< second deep blue color family >

When the zirconia sintered body obtained by sintering is colored in a deep blue color, the oxide preferably contains 0.2 to 0.8 mass% of CoO and 0.26 to 0.7 mass% of Cr under the condition that the alumina content is 1 to 3 mass% inclusive₂O₃0.21 to 0.4 mass% of MnO₂。

The content of CoO is more preferably 0.3 to 0.7% by mass, and still more preferably 0.35 to 0.5% by mass.

The above Cr₂O₃The content of (b) is more preferably 0.3 to 0.5 mass%, and still more preferably 0.35 to 0.45 mass%.

MnO as described above₂The content of (b) is more preferably 0.25 to 0.4% by mass, and still more preferably 0.28 to 0.32% by mass.

< third deep blue color line >

When the zirconia sintered body obtained by sintering is colored in a deep blue color, it is preferable that the oxide contains 0.1 to 0.5 mass% of Fe under the condition that the content of alumina is 1.5 to 4 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.3 to 0.9 mass% of Cr₂O₃0.2 to 0.4 mass% of TiO₂。

Fe as described above₂O₃The content of (b) is more preferably 0.2 to 0.4% by mass, and still more preferably 0.25 to 0.35% by mass.

The content of CoO is more preferably 1.2 to 1.8% by mass, and still more preferably 1.3 to 1.6% by mass.

The above Cr₂O₃The content of (b) is more preferably 0.4 to 0.7% by mass, and still more preferably 0.47 to 0.63% by mass.

The above TiO compound₂The content of (b) is more preferably 0.23 to 0.36 mass%, and still more preferably 0.25 to 0.33 mass%.

< fourth deep blue color line >

When the zirconia sintered body obtained by sintering is colored in a deep blue color, it is preferable that the oxide contains 0.02 to 1 mass% of Fe under the condition that the content of alumina is 0.5 to 2.5 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.03 to 0.3 mass% of Cr₂O₃0.01 to 0.1 mass% of TiO₂。

Fe as described above₂O₃The content of (b) is more preferably 0.03 to 0.08% by mass, and still more preferably 0.035 to 0.07% by mass.

The content of CoO is more preferably 1.2 to 1.9% by mass, and still more preferably 1.4 to 1.7% by mass.

The above Cr₂O₃The content of (b) is more preferably 0.05 to 0.2 mass%, and still more preferably 0.07 to 0.13 mass%.

The above TiO compound₂The content of (b) is more preferably 0.02 to 0.09 mass%, and still more preferably 0.03 to 0.07 mass%.

< fifth deep blue color line >

When the zirconia sintered body obtained by sintering is colored in a deep blue color, it is preferable that the oxide contains 1.05 to 2 mass% of CoO under the condition that the content of alumina is 1 to 3 mass%.

The content of CoO is more preferably 1.1 to 1.8% by mass, and still more preferably 1.2 to 1.4% by mass.

The zirconia powder has a pore volume of 0.14 to 0.28mL/g, wherein the pore diameter is 200nm or less. The pore diameter referred to herein indicates the size of voids in the secondary particles formed by the aggregation of the primary particles.

When the pore volume of 200nm or less is less than 0.14mL/g, the primary particles are too strongly aggregated, and therefore, the secondary particles become coarse and the sinterability is lowered. When the pore volume of 200nm or less exceeds 0.28mL/g, the aggregation of primary particles is weak, and therefore the molding density of the molded article is low, and a sintered body having a high sintering density cannot be obtained. The pore volume of 200nm or less is preferably 0.15 to 0.27mL/g, more preferably 0.16 to 0.27 mL/g. Further, the pore volume exceeding 200nm indicates the voids between the secondary particles, and therefore, the correlation between such large voids and the degree of aggregation of the primary particles is low. The pore volume was measured according to the method described in the examples.

When the particle size of the primary particles of the zirconia powder of the present embodiment is 200nm or less, voids in the secondary particles formed by aggregation of the primary particles, that is, the pore diameter between the primary particles is likely to be 200nm or less. The degree of aggregation of the primary particles constituting the secondary particles can be controlled by controlling the pore volume of pores having a pore diameter of 200nm or less. When the pore volume is small, voids in the secondary particles are reduced, and the aggregation of the primary particles is enhanced. Therefore, a molded body obtained from a powder having a small pore volume value tends to have a high molding density because the primary particles constituting the secondary particles are densely packed.

As described above, the zirconia powder of the present embodiment has a pore volume within a specific range, and thus can improve the cohesiveness of the primary particles constituting the secondary particles and suppress the coarsening of the primary particles, as compared with the zirconia powder known in the related art. Therefore, by controlling the pore volume of pores having a pore diameter of 200nm or less in the above range, the aggregation of the primary particles themselves is enhanced, and the coarsening of the primary particles is suppressed. Thus, the zirconia powder of the present embodiment has excellent characteristics, and particularly, the zirconia powder has excellent moldability.

The average particle diameter of the zirconia powder is preferably 0.3 μm or more and 0.8 μm or less. When the average particle diameter of the zirconia powder is within the above range, a molded body having a high molding density can be easily obtained, and the sinterability and the reduction in the sintered density can be easily suppressed. Further, if the average particle diameter of the zirconia powder is within the above range, it is not necessary to extend the grinding time in the grinding step. In addition, if the average particle diameter of the zirconia powder is 0.8 μm or less, the monoclinic phase in the powder is not excessive, and therefore a sintered body having a high sintering density is easily obtained. The average particle diameter of the zirconia powder is preferably 0.35 μm or more, and more preferably 0.4 μm or more. The average particle diameter of the zirconia powder is preferably 0.75 μm or less, and more preferably 0.7 μm or less.

The average particle diameter of the zirconia powder was measured by using a laser diffraction particle size distribution measuring apparatus "SALD-2000" (manufactured by Shimadzu corporation). More specifically, the method is based on the method described in examples. The average particle diameter described in the present specification is a value measured on a volume basis.

The specific surface area of the zirconia powder is preferably 5m²More than 20 m/g²The ratio of the carbon atoms to the carbon atoms is less than g. If the specific surface area of the above zirconia powder is 5m²More than 20 m/g²(ii) a specific ratio of (i) to (ii) is not more than g, a molded article having a high molding density can be easily obtained, and sinterability and sintering density can be easily suppressedAnd decreases. The specific surface area of the zirconia powder is preferably 6m²A value of at least one of,/g, more preferably 6.5m²A total of 7m or more, preferably²More than g. The specific surface area of the zirconia powder is preferably 18m²A ratio of 15m or less per gram²A total of 13m or less, preferably²The ratio of the carbon atoms to the carbon atoms is less than g.

In the present specification, the specific surface area of the zirconia powder refers to BET specific surface area, and is a value measured using a specific surface area meter "Macsorb" (manufactured by MOUNTECH corporation).

The zirconia powder was formed at a forming pressure of 1t/cm²The relative molding density during molding is 44-55%. The relative molding density is preferably 45% or more, more preferably 46% or more, still more preferably 47% or more, and particularly preferably 48% or more. The relative molding density is preferably 54% or less, more preferably 53% or less, still more preferably 52% or less, particularly preferably 51% or less, and even more preferably 50% or less.

The relative molding density is a value calculated by the following formula (1).

Wherein the theoretical sintered density (is defined as ρ)₀) Is a value calculated by the following formula (2-1).

ρ₀＝100/[(Y/3.987)+(100-Y)/ρz]···(2-1)

Wherein X and Y are the yttria concentration (mol%) and alumina concentration (wt%), respectively. ρ z is a value calculated by the following formula (2-2).

ρz＝[124.25(100-X)+225.81X]/[150.5(100+X)A²C]···(2-2)

Wherein A and C are values calculated by the following formulas (2-3) and (2-3), respectively.

A＝0.5080+0.06980X/(100+X)···(2-3)

C＝0.5195-0.06180X/(100+X)···(2-4)

In formula (1), the theoretical sintered density varies depending on the composition of the powder. For example, if the yttria content is 2 mol%, thenThe theoretical sintered density of the yttria-containing zirconia was 6.112g/cm³When the content of yttrium oxide is 3 mol%, the theoretical sintered density of yttrium oxide-containing zirconia is 6.092g/cm³When the content of yttrium oxide is 5.5 mol%, the theoretical sintered density of yttrium oxide-containing zirconia is 6.045g/cm³. In addition, these theoretical sintered densities take into account the amount of alumina of 0.25%. The molding density can be calculated by measuring the weight and volume of the molded article. In the case where a colorant is added, the theoretical density can be calculated by the same calculation as that for the addition of alumina.

The zirconia powder is preferably molded at a molding pressure of 1t/cm²Molding, and the relative sintering density is more than 99.5% when the material is sintered for 2 hours at 1450 ℃. When the relative sintered density is 99.5% or more of the theoretical sintered density, the sintered density is said to be high.

The relative sintered density is a value calculated by the following formula (3).

Relative sintered density ((%)) x 100 · (3) (sintered density/theoretical sintered density)

The sintered density is a value measured by the archimedes method.

The zirconia powder of the present embodiment is explained above.

[ method for producing zirconia powder ]

Although an example of the method for producing the zirconia powder will be described below, the method for producing the zirconia powder of the present invention is not limited to the following example.

The zirconia powder of the present embodiment can be obtained by mixing the above-described oxide with a powder serving as a base material before adding the colorant (the above-described oxide). Specifically, the powder to be the base material can be produced by the method for producing zirconia powder disclosed in japanese patent No. 62250242 (international publication No. 2007/170565). As a more detailed method of mixing, it is preferable to disperse in pure water or the like to make a slurry and wet mix the slurry. It is preferable to dry the mixture after wet mixing and size-control the mixture by sieving or the like. The mixing is preferably performed in a form in which the powder to be the base material and the oxide are not pulverized (a form in which the average particle diameter and crystallite diameter are not changed).

The method for producing the zirconia powder of the present embodiment is explained above.

[ method for producing zirconia sintered body ]

An example of a method for producing a zirconia sintered body will be described below, but the method is not limited to the following example.

The method for producing a zirconia sintered body according to the present embodiment includes:

step X of molding the zirconia powder to obtain a molded body; and

and a step Y of sintering the molded body after the step X.

< Process X >

In the method for producing a zirconia sintered body according to the present embodiment, first, the zirconia powder is molded to obtain a molded body (step X). The molding pressure is not particularly limited, and may be 0.5t/cm²Above 5t/cm²0.8t/cm or less²Above 2t/cm²The following, etc.

When the zirconia powder is molded, a commercially available mold molding machine or Cold Isostatic Pressing (CIP) method may be used. Alternatively, the zirconia powder may be temporarily molded by a die molding machine and then subjected to main molding by CIP isostatic pressing. Conventionally, the production of a molded article of a colored zirconia powder was carried out under high pressure, but in the present embodiment, a low molding pressure (for example, a molding pressure of 0.8 t/cm) can be used even in the above numerical range²Above 1.5t/cm²Below) was prepared into a molded article. In the present embodiment, even when a compact is produced by using the zirconia powder at such a low molding pressure, a sintered body having high strength can be obtained.

< Process Y >

After the step X, the molded body is sintered (step Y). Thus, the zirconia sintered body of the present embodiment is obtained.

The heat treatment temperature and time at the time of sintering are not particularly limited, and preferably about 1400 to 1550 ℃ for about 1 to 5 hours. The heat treatment atmosphere is preferably in the atmosphere or an oxidizing atmosphere.

The method for producing the zirconia sintered body of the present embodiment is explained above.

[ zirconia sintered body ]

The zirconia sintered body of the present embodiment,

containing at least one oxide selected from the group consisting of group 4 to group 9, group 12, group 14 and lanthanoid elements,

the zirconia powder is obtained by the method for producing zirconia powder.

The zirconia sintered body contains zirconia. The content of the zirconia is preferably 90 mass% or more, more preferably 92 mass% or more, further preferably 94 mass% or more, and particularly preferably 94.3 mass% or more, assuming that the zirconia sintered body is 100 mass%. The upper limit of the content of zirconia is not particularly limited, and the content of zirconia is preferably 97.5% by mass or less, more preferably 97.2% by mass or less, still more preferably 97% by mass or less, and particularly preferably 96.9% by mass or less.

The zirconia sintered body contains yttria in an amount of 2 mol% to 6 mol% based on the total mol amount of the zirconia.

The content of yttrium oxide is preferably 2 to 5 mol%, particularly preferably 2 to 4 mol%. In the case where the content ratio of yttria is 3 to 6 mol%, a cubic phase having low optical anisotropy is formed, and therefore, a zirconia sintered body having excellent light transmittance can be obtained.

The zirconia sintered body may contain alumina (alumina).

The content of the alumina is not particularly limited, and may be 0.005 to 4.0% by mass, and more preferably 0.005 to 2.0% by mass, based on the total mass of the zirconia sintered body. In the case where the zirconia sintered body contains alumina, sinterability is improved and the crystal structure is easily uniformized. Further, if the zirconia sintered body contains alumina, the reduction of fracture toughness is easily suppressed. Further, if the content of alumina is adjusted, the light transmittance of the zirconia sintered body can be improved. The upper limit of the content of alumina is preferably 1.0 mass% or less, more preferably 0.5 mass% or less, further preferably 0.4 mass% or less, and particularly preferably 0.3 mass% or less, with respect to the total mass of the zirconia sintered body.

The zirconia sintered body contains one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements. Since the zirconia sintered body contains, as a colorant, one or more oxides selected from the group consisting of group 4 to group 9, group 12, group 14, and lanthanoid elements, the zirconia sintered body can be colored.

Specifically, the oxide includes, for example, TiO₂、V₂O₅、Cr₂O₃、MnO₂、Fe₂O₃、CoO、ZnO、SiO₂、Er₂O₃、Tb₄O₇、Pr₆O₁₁And the like.

< first Black color line >

When the zirconia sintered body is colored black, it is preferable that the oxide contains 0.4 to 1.0 mass% of Fe₂O₃0.9 to 1.5 mass% of CoO, 1.0 to 1.6 mass% of Cr₂O₃0.5 to 0.9 mass% of TiO₂In the L × a × b color system, L is defined to be-1 to 13, a is-7 to 7, and b is-8 to 6.

L is more preferably 4 to 8, and still more preferably 5 to 6.5.

A is more preferably-2 to 2, and still more preferably-1 to 0.

B is more preferably from-3 to 1, and still more preferably from-1.5 to 0.5.

When the oxide is contained in the above range, L, a, b defined in the system of L, a, b are easily within the above numerical range, and preferable color development is achieved.

< second Black color line >

When the zirconia sintered body is colored in a black system different from the first black system, it is preferable that the oxide contains 0.9 to 1.5 mass% of CoO and 1.0 to 1.6 mass% of Cr₂O₃0.8 to 1.4 mass% of MnO₂In the L × a × b color system, L is defined to be 1 to 17, a is-9 to 5, and b is-8 to 6.

L is more preferably 6 to 12, and still more preferably 8 to 9.

A is more preferably-4 to 0, and still more preferably-2 to-1.

B is more preferably from-3 to 1, and still more preferably from-1.5 to 0.5.

< third Black line >

When the zirconia sintered body is colored in a black system different from the first and second black systems, it is preferable that the oxide contains 0.2 to 0.5 mass% of MnO under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂In the L × a × b color system, L is 1 to 23, a is-5 to 11, and b is-10 to 6.

L is more preferably 6 to 18, and still more preferably 10 to 14.

A is more preferably 0 to 6, and still more preferably 2 to 4.

B is more preferably from-5 to 1, and still more preferably from-3 to 1.

< first white color line >

When the zirconia sintered body is colored in white, it is preferable that 0.15 to 0.35 mass% of ZnO be contained as the oxide, and L defined in the laa b color system is 80 to 96, a is-7 to 7, and b is-6 to 8.

L is more preferably 85 to 91, and still more preferably 87 to 89.

A is more preferably-2 to 2, and still more preferably-1 to 0.

B is more preferably from-1 to 3, and still more preferably from 1 to 2.

< second white color line >

When the zirconia sintered body is colored in a white color, it is preferable that 0.03 to 0.30 mass% of SiO is contained as the oxide under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂In the L × a × b color system, L is defined to be 77 or more and 97 or less, a is-5 or more and 5 or less, and b is-5 or more and 5 or less.

L is more preferably 82 to 91, and still more preferably 84 to 89.

A is more preferably from-3 to 3, and still more preferably from-1 to 1.

B is more preferably from-3 to 3, and still more preferably from 0 to 2.

< first gray color line >

When the zirconia sintered body is colored in gray, it is preferable that the oxide contains 0.03 to 0.06 mass% of MnO under the condition that the content of alumina is less than 0.005 mass% (under the condition that alumina is not substantially contained)₂In the L × a × b color system, L is defined to be 28 to 44, a is-3 to 8, and b is-8 to 8.

L is more preferably 33 to 39, and still more preferably 35 to 37.

A is more preferably 2 to 7, and still more preferably 4 to 6.

B is more preferably from-3 to 3, and still more preferably from-1 to 1.

< second gray color line >

When the zirconia sintered body is colored in gray, it is preferable that the oxide contains 0.02 to 0.05 mass% of MnO under the condition that the content of alumina is 0.005 to 2 mass% inclusive₂In the L × a × b color system, L is defined to be 31 to 47, a is-4 to 12, and b is-9 to 7.

L is more preferably 36 to 42, and still more preferably 38 to 40.

A is more preferably 1 to 7, and still more preferably 3 to 5.

B is more preferably-4 to 2, and still more preferably-2 to 0.

< third gray color line >

When the zirconia sintered body is colored in gray, it is preferable that 0.02 to 0.1 mass% of Cr is contained₂O₃In the L × a × b color system, L is 30 to 52, a is-5 to 8, and b is 0 to 20.

L is more preferably 35 to 47, and still more preferably 39 to 43.

A is more preferably 0 to 6, and still more preferably 2 to 4.

B is more preferably 5 to 15, and still more preferably 9 to 12.

< first brown line >

When the zirconia sintered body is colored brown, it is preferable that 0.12 to 0.23 mass% of Fe is contained as the oxide under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂O₃In the L × a × b color system, L is defined to be 55 to 75, a is-2 to 14, and b is 18 to 40.

L is more preferably 60 to 70, and still more preferably 63 to 67.

A is more preferably 3 to 9, and still more preferably 5 to 7.

B is more preferably 23 to 33, and still more preferably 26 to 30.

< second brown line >

When the zirconia sintered body is colored brown, it is preferable that the content of the alumina is less than 0.005 mass% (under the condition that the alumina is not substantially contained), and 0.12 to 0.23 mass% of Fe is contained as the oxide₂O₃In the L × a × b color system, L × defined is 41 to 61, a × is 2 to 18, and b × is 18 to 38.

L is more preferably 46 to 56, and still more preferably 49 to 53.

A is more preferably 7 to 13, and still more preferably 9 to 11.5.

B is more preferably 23 to 33, and still more preferably 27 to 30.

< third brown line >

When the zirconia sintered body is colored in a brown system having a darker hue than the first brown color, it is preferable that 0.23 to 0.40 mass% of Fe is contained under the condition that the content of alumina is 0.005 mass% or more and 2 mass% or less₂O₃In the L × a × b color system, L × defined is 44 to 64, a × is 1 to 17, and b × is 20 to 40.

L is more preferably 49 to 59, and still more preferably 52 to 56.

A is more preferably 6 to 12, and still more preferably 8 to 10.5.

B is more preferably 25 to 35, and still more preferably 28 to 32.

< blue color system >

When the zirconia sintered body is colored in a blue color, it is preferable that 0.3 to 1.0 mass% of CoO is contained under the condition that the alumina content is 1 mass% or more and 3 mass% or less, L defined in the laa b color system is 22 to 44, a is-10 to 7, and b is-50 to 28.

L is more preferably 27 to 39, and still more preferably 31 to 36.

A is more preferably from-5 to 2, and still more preferably from-3 to 0.

B is more preferably from-45 to-33, and still more preferably from-41 to-37.

< yellow color series >

When the zirconia sintered body is colored in a yellow color, it is preferable that 0.20 to 0.60 mass% of Pr is contained under the condition that the alumina content is 0.005 mass% or more and 2 mass% or less₆O₁₁In the L × a × b color system, L is defined to be 55 to 75, a is 4 to 20, and b is 40 to 60.

L is more preferably 60 to 70, and still more preferably 63 to 67.

A is more preferably 6 to 18, and still more preferably 9 to 13.

B is more preferably 43 to 57, and still more preferably 47 to 54.

< first deep blue color family >

When the zirconia sintered body is colored in a deep blue color, it is preferable that the oxide contains 0.3 to 1.0 mass% of CoO and 0.05 to 0.25 mass% of Cr under the condition that the alumina content is 1 to 3 mass% inclusive₂O₃0.03 to 0.2 mass% of MnO₂In the L x a b color system, L x is 13 to 33, a x is-12And b is from-29 to-19.

L is more preferably 16 to 30, and still more preferably 20 to 26.

A is more preferably from-11 to-3, and still more preferably from-9 to-5.

B is more preferably from-28 to-20, and still more preferably from-26 to-22.

< second deep blue color family >

When the zirconia sintered body is colored in a deep blue color, it is preferable that the oxide contains 0.2 to 0.8 mass% of CoO and 0.26 to 0.7 mass% of Cr under the condition that the content of alumina is 1 to 3 mass% inclusive₂O₃0.21 to 0.4 mass% of MnO₂In the L x a b color system, L x is 8 to 28, a x is-14 to-4, and b x is-21 to-11.

L is more preferably 11 to 25, and still more preferably 14 to 22.

A is more preferably from-13 to-5, and still more preferably from-11 to-7.

B is more preferably from-20 to-12, and still more preferably from-18 to-14.

< third deep blue color line >

When the zirconia sintered body is colored in a deep blue color, it is preferable that the oxide contains 0.1 to 0.5 mass% of Fe under the condition that the content of alumina is 1.5 to 4 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.3 to 0.9 mass% of Cr₂O₃0.2 to 0.4 mass% of TiO₂In the L x a b color system, L x is 27 to 48, a x is-6 to 4, and b x is-10 to-1.

L is more preferably 30 to 45, and still more preferably 34 to 40.

A is more preferably from-5 to 3, and still more preferably from-3 to 1.

B is more preferably-9 to-2, and still more preferably-7 to-4.

< fourth deep blue color line >

When the zirconia sintered body is colored in a deep blue color, it is preferable that 0.02 to 1 mass% of Fe is contained as the oxide under the condition that the content of alumina is 0.5 to 2.5 mass%, inclusive₂O₃1 to 2 mass% of CoO, 0.03 to 0.3 mass% of Cr₂O₃0.01 to 0.1 mass% of TiO₂In the L x a b color system, L x is 27 to 48, a x is-6 to 4, and b x is-10 to-1.

L is more preferably 30 to 45, and still more preferably 34 to 40.

A is more preferably from-5 to 3, and still more preferably from-2 to 2.

B is more preferably-9 to-2, and still more preferably-7 to-4.

< fifth deep blue color line >

When the zirconia sintered body is colored in a deep blue color, it is preferable that the zirconia sintered body contains 1.05 to 2 mass% of CoO as the oxide under the condition that the content of alumina is 1 to 3 mass%, L defined in a la b color system is 27 to 48, a is-5 to 6, and b is-12 to-2.

L is more preferably 30 to 45, and still more preferably 35 to 41.

A is more preferably from-5 to 3, and still more preferably from-2 to 2.

B is more preferably from-11 to-3, and still more preferably from-9 to-5.

Note that the L × a × b color system is a color space recommended by the international commission on illumination (CIE) in 1976, and refers to a color space called CIE1976(L × a × b) color system. In japanese industrial standards, the color system is defined in JIS Z8729. In the present specification, the values of L, a, and b (measurement of color tone) are measured after adjusting the zirconia sintered body to a thickness of 3mm and performing mirror polishing using a diamond polishing paste containing diamond abrasive grains having a grain size of 3 μm or less.

The sintered density of the zirconia sintered body is preferably 99.5% or more of the theoretical sintered density. When the sintered density is 99.5% or more of the theoretical sintered density, the sintered density can be said to be high.

The zirconia sintered body of the present embodiment is explained above.

[ examples ]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples as long as the invention does not depart from the gist thereof. In the zirconia powders obtained in examples and comparative examples, 1.3 to 2.5 mass% of hafnium oxide (calculated by the following formula (X)) was contained as an inevitable impurity with respect to zirconia.

< formula (X) >

([ mass of hafnium oxide ]/([ mass of zirconium oxide ] + [ mass of hafnium oxide ])). times.100 (%)

[ production of zirconia powder and zirconia sintered body ]

(example 1)

The sodium sulfate powder was dissolved in ion-exchanged water to obtain a 5 mass% solution of sodium sulfate. The resulting sodium sulfate solution was heated and maintained at 85 ℃.

On the other hand, the zirconium oxychloride solution was adjusted so that zirconium was contained in an amount of 1 mass% in terms of zirconia, and the solution was heated and maintained at 85 ℃. The total amount of zirconia was 100 g.

Subsequently, 1000g of the entire sodium sulfate solution kept at a constant temperature of 85 ℃ was added to the zirconium oxychloride solution kept at a constant temperature of 85 ℃ for 10 seconds while stirring, and mixed, thereby obtaining basic zirconium sulfate slurry. To this was added a yttrium chloride solution so that the amount of yttrium oxide was 3.0 mol% with respect to zirconium oxide, followed by neutralization with sodium hydroxide to obtain a hydroxide.

After filtering and washing the hydroxide, the hydroxide was fired in an electric furnace at a firing temperature of 1000 ℃ to obtain an oxide (zirconia), and then 0.25 mass% of alumina powder having an average particle size of 0.1 μm and 0.7 mass% of Fe as a colorant were added to the oxide₂O₃Powder, 1.2 mass% CoO powder, 1.3 mass% Cr₂O₃Powder, 0.7 mass% TiO₂The powder was pulverized and mixed in a wet ball mill using water as a dispersion medium for 30 hours. The resulting slurry was dried at a constant temperature of 120 ℃ to obtain the zirconia powder of example 1.

8g of the obtained zirconia powder was temporarily molded using a mold having a diameter of 25mm at a rate of 1t/cm²The molding is performed under the molding pressure (hydrostatic pressure). The molding density of the molded article was calculated by measuring the weight and volume. The obtained molded body was sintered at 1450 ℃ for 2 hours to obtain a zirconia sintered body of example 1.

(examples 2 to 19)

The zirconia powders of examples 2 to 19 were obtained in the same manner as in example 1, except that the amounts of yttria, alumina powder, colorant and firing temperature were changed as shown in table 1. In addition, the zirconia sintered bodies of examples 2 to 19 were obtained in the same manner as in example 1.

[ measurement of composition of zirconia powder ]

The compositions (in terms of oxides) of the zirconia powders of the examples were analyzed by ICP-AES ("ULTIMA-2" HORIBA, HORIBA). As shown in table 1.

[ measurement of pore volume ]

The zirconia powder of the examples was subjected to mercury intrusion method using a pore distribution measuring apparatus ("AutoPore IV 9500" manufactured by mike instruments) to obtain a pore distribution. The measurement conditions are as follows.

< measurement conditions >

A measuring device: pore distribution measuring device (AutoPore IV 9500, product of Mike instruments)

Measurement range: 0.0036 to 10.3 μm

Measuring the number of points: 120 points

Mercury contact angle: 140degrees

Mercury surface tension: 480dyne/cm

The pore volume in the range of 200nm or less was determined using the obtained pore distribution. Table 2 shows the results.

[ average particle diameter of zirconia powder ]

The average particle diameter of the zirconia powder of the examples was measured by using a laser diffraction particle diameter distribution measuring apparatus "SALD-2000" (manufactured by Shimadzu corporation). More specifically, 0.15g of the sample and 40ml of a 0.2% aqueous solution of sodium hexametaphosphate were put into a 50ml beaker, dispersed for 5 minutes by a ultrasonic bench-top cleaning machine "W-113" (manufactured by Suppon electronics Co., Ltd.), and then put into a laser diffraction particle size distribution measuring apparatus ("SALD-2000", manufactured by Shimadzu corporation) for measurement. Table 2 shows the results.

[ measurement of specific surface area of zirconia powder ]

The specific surface area of the zirconia powder of the example was measured by the BET method using a specific surface area meter ("Macsorb" manufactured by MOUNTECH). Table 2 shows the results.

[ at a molding pressure of 1t/cm²Relative molding density at the time of molding]

At a molding pressure of 1t/cm²The zirconia powders of the examples were molded, and the relative molding density was calculated by the following formula (1).

ρ₀＝100/[(Y/3.987)+(100-Y)/ρz]···(2-1)

ρz＝[124.25(100-X)+225.81X]/[150.5(100+X)A²C]···(2-2)

A＝0.5080+0.06980X/(100+X)···(2-3)

C＝0.5195-0.06180X/(100+X)···(2-4)

In formula (1), the theoretical sintered density varies depending on the composition of the powder. For example, if the yttria content is 2 mol%, the theoretical sintered density of yttria-containing zirconia is 6.112g/cm³When the content of yttrium oxide is 3 mol%, the theoretical sintered density of yttrium oxide-containing zirconia is 6.092g/cm³When the content of yttrium oxide is 5.5 mol%, the theoretical sintered density of yttrium oxide-containing zirconia is 6.045g/cm³. In addition, these theoretical sintered densities take into account the amount of alumina of 0.25%. The molding density was calculated by measuring the weight and volume of the molded article. In the case where a coloring agent was added, the theoretical density was calculated by the same calculation as that for the addition of alumina.

[ at a molding pressure of 1t/cm²Molding, relative sintered density at 1450 deg.C for 2 hr]

The relative sintered density of the zirconia sintered body of the example was determined according to the formula (3).

Relative sintered density (%) (sintered density/theoretical sintered density) × 100 · (3)

The sintered density was measured by the archimedes method.

[ color tone of sintered body ]

After the zirconia sintered bodies of examples were adjusted to a thickness of 3mm, mirror polishing was performed using an automatic polishing machine ("Ecomet 250" manufactured by BUEHLER (trademark). In the finish of mirror polishing, a diamond paste containing diamond abrasive grains having a grain size of 3 μm was used. Thereafter, the color tone of the obtained sintered body was measured using a color difference meter (trade name: CM-3500d, manufactured by Konika Mendata). Table 1 shows the results.

[ Table 1]

[ Table 2]

Claims

1. A zirconia powder, comprising:

zirconia containing yttria in a range of 2 mol% to 6 mol%; and

at a molding pressure of 1t/cm²The relative molding density of the resin composition represented by the following formula (1) during molding is 44 to 55%,

relative molding density (%) (molding density/theoretical sintered density) × 100 · (1).

2. The zirconia powder according to claim 1,

the groups 4 to 9 are at least one selected from the group consisting of Ti, V, Cr, Mn, Fe and Co,

the group 12 is Zn, and the group is Zn,

the group 14 is Si, and the group is,

the lanthanide is one or more selected from the group consisting of Er, Tb and Pr.

3. The zirconia powder according to claim 1,

the specific surface area is 5-20 m²/g，

The average particle size is 0.3 to 0.8 μm.

4. The zirconia powder according to claim 1,

contains alumina.

5. The zirconia powder according to any one of claims 1 to 4,

at a molding pressure of 1t/cm²Molding, and the relative sintering density is more than 99.5% when the material is sintered for 2 hours at 1450 ℃.

6. A method for producing a zirconia sintered body, comprising:

a step X of molding the zirconia powder according to any one of claims 1 to 5 to obtain a molded body;

and a step Y of sintering the molded body after the step X.

7. A zirconia sintered body characterized by comprising, in a sintered body,

the method according to claim 6.

8. The zirconia sintered body according to claim 7,

the group 12 is Zn, and the group is Zn,

the group 14 is Si, and the group is,