Zirconia sintered body and method for producing zirconia sintered body

Abstract

Disclosed is a zirconia sintered body containing stabilized zirconia that contains zirconia and a stabilizer, wherein: the stabilizer contains Y2O3; the content of Y2O3 in the stabilized zirconia is more than 4.0 mol% but not more than 6.5 mol% in terms of oxides; the average crystal grain size is 100 nm to 200 nm inclusive; the monoclinic phase ratio is 0.5% or less; the tetragonal phase ratio is 20.0% to 96.0% inclusive; the cubic phase ratio is 4.0% to 80.0% inclusive; and the relative sintered density is 99.6% or more.

Description

Zirconia sintered body, and method for manufacturing a zirconia sintered body

[0001] The present invention relates to a zirconia sintered body and a method for producing a zirconia sintered body.

[0002] Conventionally, efforts have been made to improve the mechanical strength, transparency (parallel light transmittance), and light transmission (total light transmittance) of zirconia sintered bodies.

[0003] For example, Patent Document 1 discloses a translucent yttria-containing zirconia sintered body made of zirconia containing more than 4 mol% and 7 mol% or less of yttria, having a sintered body particle size of 2.0 μm or less, a relative density of 99.5% or more, and a total light transmittance of 40% or more for visible light at a wavelength of 600 nm at a thickness of 1 mm (Claim 1). It is also disclosed that a zirconia sintered body with this configuration achieves high translucency and strength (Paragraph

[0011] ).

[0004] Japanese Patent Publication No. 2008-222450

[0005] However, Patent Document 1 states that the crystal grain size is 0.4 μm or larger (paragraph

[0016] ), and it is presumed that it does not have transparency. In other words, while the zirconia sintered body of Patent Document 1 appears to possess a certain degree of light transmission and strength, it cannot be said to have transparency.

[0006] Thus, while sintered bodies that achieve both mechanical strength and transparency or light transmission have been obtained in the past, a zirconia sintered body that possesses all three qualities—mechanical strength, transparency, and light transmission—has not yet been obtained.

[0007] The present invention has been made in view of the above-mentioned problems, and its objective is to provide a zirconia sintered body that has sufficient mechanical strength and excellent light transmission and transparency. Furthermore, it aims to provide a method for manufacturing the zirconia sintered body.

[0008] The inventors of this invention conducted thorough research to address the above-mentioned problems. As a result, they discovered that the above-mentioned problems could be solved by adopting the following configuration, and thus completed the present invention.

[0009] The present invention provides the following: [1] Stabilized zirconia comprising zirconia and a stabilizer, wherein the stabilizer is Y ２ O ３ The Y in the stabilized zirconia includes ２ O ３ A zirconia sintered body characterized by having a content of over 4.0 mol% and up to 6.5 mol% in terms of oxide, an average crystal grain size of 100 nm to 200 nm, a monoclinic phase ratio of 0.5% or less, a tetragonal phase ratio of 20.0% to 96.0%, a cubic phase ratio of 4.0% to 80.0%, and a relative sintering density of 99.6% or more.

[0010] To improve transparency, methods to suppress scattering at grain interfaces can be considered. To suppress scattering at grain interfaces, it is effective to reduce the number of grain interfaces per unit thickness, that is, to increase the grain size. However, increasing the grain size to a degree that transparency can be obtained will reduce the mechanical strength. Therefore, in the present invention, transparency and light transmission were achieved by maintaining high mechanical strength while suppressing other methods, namely "scattering at grain boundaries" and "scattering at residual pores," by setting the average grain size to 200 nm or less. There are two types of "scattering at grain boundaries": scattering at the tetragonal phase / tetragonal phase interface and scattering at the tetragonal phase / cubic phase interface. In order to suppress "scattering at grain boundaries," the inventors came up with the idea of ​​1. increasing the ratio of the cubic phase, which is optically isotropic, and 2. suppressing scattering in the tetragonal phase by reducing the grain size. Regarding "1." above, according to the present invention, Y in stabilized zirconia ２ O ３ Since the content exceeds 4.0 mol% in terms of oxides, the cubic phase ratio can be set to 4.0% or higher. Because the cubic phase ratio is 4.0% or higher, scattering at grain boundaries can be suppressed, and light transmittance can be improved. Also, Y ２ O ３Since the content of [substance] is 6.5 mol% or less in terms of oxide, it has excellent mechanical strength. Also, regarding the above "2.", according to the present invention, since the average crystal grain diameter is 100 nm or more and 200 nm or less, there are particles with a diameter smaller than the visible light wavelength, and the influence of scattering at grain boundaries is reduced. Moreover, since the cubic phase ratio is 4.0% or more, the scattering of the tetragonal phase is suppressed, and particularly the transparency is improved. Also, in the present invention, since the relative sintered density is 99.6% or more, "scattering at residual pores" is suppressed, and high light transmittance and transparency are obtained. Note that Y ２ O ３ When the content of [substance] is more than 4.0 mol% and 6.5 mol% or less in terms of oxide, the tetragonal phase ratio and the cubic phase ratio are in a trade-off relationship. The more the content of Y ２ O ３ is, the higher the cubic phase ratio becomes, while the tetragonal phase ratio becomes lower. The less the content of Y ２ O ３ is, the higher the tetragonal phase ratio becomes, while the cubic phase ratio becomes lower. Also, since the content of Y ２ O ３ in the stabilized zirconia is more than 4.0 mol% in terms of oxide, the monoclinic phase ratio can be made 0.5% or less. The more the monoclinic phase is contained, the lower the mechanical strength and transparency become. On the other hand, according to the present invention, since the monoclinic phase ratio is 0.5% or less, it is excellent in mechanical strength and transparency.

[0011] From the above, according to the above configuration, it is possible to provide a zirconia sintered body having sufficient mechanical strength and excellent light transmittance and transparency.

[0012] Furthermore, the present invention provides the following. [2] The zirconia sintered body according to [1], wherein the content of Y ２ O ３ in the stabilized zirconia is more than 5.2 mol% in terms of oxide.

[0013] When the content of Y ２ O ３ in the stabilized zirconia is more than 5.2 mol% in terms of oxide, it becomes easier to make the cubic phase ratio 40.0% or more.

[0014] Furthermore, the present invention provides the following: [3] The zirconia sintered body according to [1] above, characterized in that the tetragonal phase ratio is 20.0% or more and 60.0% or less, and the cubic phase ratio is 40.0% or more and 80.0% or less.

[0015] When the cubic phase ratio is 40.0% or higher, scattering at grain boundaries can be further suppressed, and light transmittance can be further improved.

[0016] Furthermore, the present invention provides the following: [4] The Y in the stabilized zirconia ２ O ３ The zirconia sintered body according to [1] above, characterized in that the content of exceeds 5.2 mol% in terms of oxide, the tetragonal phase ratio is 20.0% or more and 60.0% or less, and the cubic phase ratio is 40.0% or more and 80.0% or less.

[0017] The Y in the stabilized zirconia ２ O ３ When the content exceeds 5.2 mol% in terms of oxides, it becomes easier to achieve a cubic phase ratio of 40.0% or higher. Furthermore, when the cubic phase ratio is 40.0% or higher, scattering at grain boundaries can be further suppressed, and light transmittance can be further improved.

[0018] Furthermore, the present invention provides the following: [5] Al to the entire zirconia sintered body ２ O ３ A zirconia sintered body according to any one of [1] to [4] above, characterized in that it contains in a range of 0.15% by mass or less.

[0019] Al ２ O ３ When it contains Al, it functions as a sintering aid, resulting in excellent low-temperature sintering properties. ２ O ３ If the content is 0.15% by mass or less, scattering due to the precipitated phase (grain boundaries) of alumina (impurity) is reduced, thus maintaining high light transmittance and transparency.

[0020] Furthermore, the present invention provides the following: [6] A zirconia sintered body according to any one of [1] to [5] above, characterized in that the total light transmittance at a thickness of 1 mm is 45% or more and 60% or less.

[0021] A material with a total light transmittance of 45% or more at a thickness of 1 mm can be said to have superior light transmission properties.

[0022] Furthermore, the present invention provides the following: [7] A zirconia sintered body according to any one of [1] to [6] above, characterized in that the parallel light transmittance at a thickness of 1 mm is 7.0% or more and 30.0% or less.

[0023] A parallel light transmittance of 7.0% or higher at a thickness of 1 mm can be considered to have superior transparency.

[0024] Furthermore, the present invention provides the following: [8] A zirconia sintered body according to any one of [1] to [7] above, characterized in that its three-point bending strength is 500 MPa or more and 1000 MPa or less.

[0025] A material can be considered high-strength if its three-point bending strength is 500 MPa or higher.

[0026] Furthermore, the present invention provides the following: [9] A toughness value of 2.7 MPa·m obtained by the IF method. ０．５ 5.0MPa・m or more ０．５ A zirconia sintered body according to any one of the above [1] to [8], characterized in that it is as follows:

[0027] The toughness value obtained by the IF method is 2.7 MPa·m ０．５ If the above conditions are met, it can be said that the material has high toughness.

[0028] Furthermore, the present invention provides the following:

[10] Zirconia powder at 1.0 t / cm ２ The above is 2.5 t / cm ２A method for producing a zirconia sintered body according to any one of [1] to [9] above, comprising: step A, molding at the following pressure to obtain a molded body; step B, pre-sintering the molded body under normal pressure, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a pre-sintered body; and step C, final sintering the pre-sintered body under a pressure of 50 MPa or higher and 200 MPa or lower, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a sintered body.

[0029] According to the above configuration, the molded body is pre-sintered under relatively low-temperature conditions of 1150°C to 1250°C and 1 to 5 hours under normal pressure, thereby obtaining a pre-sintered body with suppressed grain growth. Because grain growth is suppressed, it is possible to obtain a zirconia sintered body with high transparency.

[0030] Furthermore, according to the above configuration, the molded body is pre-sintered under normal pressure, at a temperature of 1150°C to 1250°C, and for 1 to 5 hours. During the pre-sintering process, the zirconia powder particles bond together appropriately, and the pores (interparticle gaps of zirconia powder) within the molded body can be made into closed pores. In other words, pre-sintering can change the pores from a state where the pores are connected to each other (open pores) to isolated closed pores surrounded by the bonded zirconia powder. Then, the pre-sintered body, in which the pores are closed, is subjected to final sintering under a pressure of 50 MPa to 200 MPa, at a temperature of 1150°C to 1250°C, and for 1 to 5 hours, thereby almost completely eliminating the closed pores. Specifically, the pressurization during final sintering compresses the closed pores to the smallest possible size, and elemental diffusion (flow of elements) during final sintering pushes the pores out of the sintered body, thus almost completely eliminating the closed pores. By removing pores, the total light transmittance (transparency) and parallel light transmittance (transparency) can be improved. However, if the pores in the pre-sintered body are not closed pores, the pores cannot be removed even if the main sintering is performed under conditions of a pressure of 50 MPa to 200 MPa, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours. This is because if the pores in the pre-sintered body are not closed pores, it becomes difficult to transmit pressure to the pores during the main sintering.

[0031] In a pre-sintered body, whether or not the pores are closed can be determined by whether or not the relative sintering density can be measured using the Archimedes method. If the pores are open, the pores will absorb water during measurement, making it impossible to measure the relative sintering density (resulting in an abnormal measurement). In other words, if the relative sintering density can be measured (within the expected range), it can be determined that the pores are closed.

[0032] Furthermore, according to the above configuration, the calcined body is subjected to main sintering under conditions of a pressure of 50 MPa to 200 MPa, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours, thereby achieving a relative sintering density of 99.6% or higher. However, if main sintering is performed directly on the molded body without forming a calcined body, that is, if step C is performed after step A without performing step B, it is not possible to achieve a relative sintering density of 99.6% or higher while maintaining an average crystal grain size of 100 to 200 nm.

[0033] In this specification, a pre-sintered body refers to a sintered body with a relative sintering density of 92% or more and less than 99.5%. Furthermore, in this specification, pre-sintering refers to sintering a sintered body so that its relative sintering density is within the range of 92% or more and less than 99.5%.

[0034] According to the present invention, Y is used as a stabilizer. ２ O ３ In a zirconia sintered body containing [a specific material], it is possible to provide a zirconia sintered body that has sufficient mechanical strength and excellent light transmission and transparency. Furthermore, a method for manufacturing such a zirconia sintered body can be provided.

[0035] This is a schematic diagram illustrating the method for producing zirconia powder according to this embodiment. This is a schematic diagram illustrating the indentation length and crack length.

[0036] Embodiments of the present invention will be described below. However, the present invention is not limited to these embodiments. In this specification, zirconia (zirconium oxide) is a general term and includes impurity metal compounds, including hafnia, in an amount of 10% by mass or less. In this specification, the expressions "contains" and "includes" include the concepts of "contains," "includes," "substantially consists of," and "consists only of."

[0037] The maximum and minimum values ​​of the content of each component shown below are, independently of the content of other components, the preferred minimum and preferred maximum values ​​of the present invention. Similarly, the maximum and minimum values ​​of the various parameters (measured values, etc.) shown below are, independently of the content (composition) of each component, the preferred minimum and preferred maximum values ​​of the present invention.

[0038] [Zirconia Sintered Body] An example of a zirconia sintered body according to this embodiment will be described below. However, the zirconia sintered body of the present invention is not limited to the following examples.

[0039] The zirconia sintered body according to this embodiment includes stabilized zirconia comprising zirconia and a stabilizer, wherein the stabilizer is Y ２ O ３ The Y in the stabilized zirconia includes ２ O ３ The content is between 4.0 mol% and 6.5 mol% in terms of oxide, the average crystal grain size is between 100 nm and 200 nm, the monoclinic phase is 0.5% or less, the tetragonal phase is between 20.0% and 96.0%, the cubic phase is between 4.0% and 80.0%, and the relative sintering density is 99.6% or more.

[0040] As described above, the zirconia sintered body according to this embodiment includes stabilized zirconia.

[0041] The content of the stabilized zirconia is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the entire zirconia sintered body is considered to be 100% by mass. The content of the stabilized zirconia can be 99% by mass or less, 98% by mass or less, etc., when the entire zirconia sintered body is considered to be 100% by mass. The zirconia sintered body may also be composed only of the stabilized zirconia. In other words, the zirconia sintered body may be composed of only the stabilized zirconia. In this case, the content of the stabilized zirconia is 100% by mass when the entire zirconia sintered body is considered to be 100% by mass. The content of the stabilized zirconia is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, even more preferably 90% by mass or more and 98% by mass or less, and particularly preferably 95% by mass or more and 98% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass.

[0042] The stabilized zirconia comprises zirconia and a stabilizing agent.

[0043] The total content of zirconia and stabilizer in the stabilized zirconia is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the total stabilized zirconia is considered to be 100% by mass. The total content of zirconia and stabilizer can be 99% by mass or less, 98% by mass or less, etc., when the total stabilized zirconia is considered to be 100% by mass. Alternatively, the stabilized zirconia may consist only of zirconia and stabilizer. In this case, the total content of zirconia and stabilizer is 100% by mass when the total content of the stabilized zirconia is considered to be 100% by mass. The total content of zirconia and stabilizer in the stabilized zirconia is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, even more preferably 90% by mass or more and 98% by mass or less, and particularly preferably 95% by mass or more and 98% by mass or less, when the total stabilized zirconia is considered to be 100% by mass.

[0044] The aforementioned stabilizer is Y ２ O ３ Includes.

[0045] The Y in the stabilized zirconia ２ O ３ The content is between 4.0 mol% and 6.5 mol% in terms of oxide. Y in stabilized zirconia ２ O ３ Since the content exceeds 4.0 mol% in terms of oxides, the cubic phase ratio can be set to 4.0% or higher. Because the cubic phase ratio is 4.0% or higher, scattering at grain boundaries can be suppressed, and light transmittance can be improved. Also, Y ２ O ３ Since the content is 6.5 mol% or less in terms of oxides, it has excellent mechanical strength. ２ O ３ Within the range of over 4.0 mol% and up to 6.5 mol% in terms of oxides, there is a trade-off relationship between tetragonal phase fraction and cubic phase fraction, Y ２ O ３ The higher the content, the higher the cubic phase ratio and the lower the tetragonal phase ratio. ２ O ３ The lower the content of Y, the higher the tetragonal phase ratio becomes, while the cubic phase ratio becomes lower. ２ O ３ Since the content exceeds 4.0 mol% in terms of oxide, the monoclinic phase ratio can be set to 0.5% or less. The more monoclinic phase is present, the lower the mechanical strength and transparency become. On the other hand, the zirconia sintered body has a monoclinic phase ratio of 0.5% or less, so it has excellent mechanical strength and transparency.

[0046] The Y in the stabilized zirconia ２ O ３ The content of is preferably more than 5.2 mol% in terms of oxide, more preferably 5.3 mol% or more. The Y in the stabilized zirconia ２ O ３ The content of is preferably 6.4 mol% or less in terms of oxide, more preferably 6.3 mol% or less. The Y in the stabilized zirconia ２ O３ The content is preferably more than 5.2 mol% and 6.4 mol% or less in terms of oxides, and more preferably 5.3 mol% or more and 6.3 mol% or less.

[0047] The aforementioned stabilizer further includes Y ２ O ３ Other stabilizers may be included. These other stabilizers are not particularly limited, but include, for example, Yb ２ O ３ Er ２ O ３ , CEO ２ , Sc ２ O ３ , Nd ２ O ３ La ２ O ３ , Tb ２ O ３ Examples include CaO, etc. These other stabilizers may be present in one or more forms.

[0048] Y ２ O ３ If other stabilizers are included, it is preferable that their content is within a range that does not significantly affect transparency and light transmission. ２ O ３ If other stabilizers are included, the content of the other stabilizers in the stabilized zirconia is preferably 0.01 mol% or more and 2.5 mol% or less in terms of oxide. The content of the other stabilizers in the stabilized zirconia is more preferably 0.05 mol% or more in terms of oxide, and even more preferably 0.10 mol% or more. The content of the other stabilizers in the stabilized zirconia is more preferably 2.0 mol% or less in terms of oxide, and even more preferably 1.5 mol% or less. The content of the other stabilizers in the stabilized zirconia is more preferably 0.05 mol% or more and 2.0 mol% or less in terms of oxide, and even more preferably 0.10 ml% or more and 1.5 mol% or less in terms of oxide.

[0049] The total amount of stabilizer in the stabilized zirconia is preferably 4.1 mol% to 6.5 mol% in terms of oxide. When the total amount of stabilizer is 4.1 mol% or more in terms of oxide, the monoclinic phase fraction can be reduced. Furthermore, when the total amount of stabilizer is 6.5 mol% or less in terms of oxide, the cubic phase fraction, which has low mechanical properties (strength, toughness), can be reduced, and the tetragonal phase fraction, which has high mechanical properties, can be increased.

[0050] The total amount of the stabilizer is more preferably 4.5 mol% or more in terms of oxide, even more preferably 5.0 mol% or more, and particularly preferably 5.2 mol% or more. The total amount of the stabilizer is more preferably 6.4 mol% or less in terms of oxide, even more preferably 6.3 mol% or less, and particularly preferably 6.0 mol% or less. The total amount of the stabilizer is more preferably 4.5 mol% or more and 6.4 mol% or less in terms of oxide, even more preferably 5.0 mol% or more and 6.3 mol% or less, and particularly preferably 5.2 mol% or more and 6.0 mol% or less.

[0051] The zirconia content in the stabilized zirconia is preferably 80% by mass or more and 99% by mass or less. The zirconia content in the stabilized zirconia is more preferably 85% by mass or more, and even more preferably 90% by mass or more. The zirconia content in the stabilized zirconia is more preferably 98% by mass or less, and even more preferably 97% by mass or less. The zirconia content in the stabilized zirconia is more preferably 85% by mass or more and 98% by mass or less, and even more preferably 90% by mass or more and 97% by mass or less.

[0052] The zirconia sintered body is composed of Al (Al) throughout the entire zirconia sintered body. ２ O ３ It is preferable that the alumina is included in an amount of 0.15% by mass or less. ２ O ３ When it contains Al, it functions as a sintering aid, resulting in excellent low-temperature sintering properties. ２ O ３If the content of is 0.15% by mass or less, scattering due to the precipitation phase (grain boundary) of alumina (impurity) is reduced, so that light transmittance and transparency can be maintained at high levels.

[0053] When the zirconia sintered body contains Al ２ O ３ the content of the Al ２ O ３ is more preferably 0.01% by mass or more, and even more preferably 0.05% by mass or more. When the zirconia sintered body contains Al ２ O ３ the content of the Al ２ O ３ is more preferably 0.13% by mass or less, and even more preferably 0.10% by mass or less. When the zirconia sintered body contains Al ２ O ３ the content of the Al ２ O ３ is more preferably 0.01% by mass or more and 0.13% by mass or less, and even more preferably 0.05% by mass or more and 0.10% by mass or less.

[0054] In addition to alumina, the zirconia sintered body may contain sinterable ceramics, thermosetting resins, etc. for the purpose of improving properties such as strength.

[0055] The zirconia sintered body may contain one or more selected from the group consisting of Fe, V, Mn, Co, Zn, Cu, and Ti within a range that does not significantly affect transparency and light transmittance. When containing one or more selected from the group consisting of Fe, V, Mn, Co, Zn, Cu, and Ti as coloring elements, the zirconia sintered body can be suitably colored.

[0056] The form of the coloring element is not particularly limited, and it can be added in the form of oxides, chlorides, etc. Specific examples of the colorant containing the coloring element include, for example, Fe ２ O ３ , V ２ O ５ , MnO ２ , CoO, ZnO, CuO, TiO ２ etc.

[0057] Fe as the coloring agent ２ O ３ When the coloring agent is included, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 0.5% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0058] V as the aforementioned coloring agent ２ O ５ When the coloring agent is included, the amount is preferably 0.005% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.1% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0059] As the coloring agent, MnO ２ When the coloring agent is included, the amount is preferably 0.005% by mass or more and 2% by mass or less, and more preferably 0.1% by mass or more and 1.1% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0060] When the coloring agent contains CoO, the content of the coloring agent is preferably 0.005% by mass or more and 2% by mass or less, and more preferably 0.01% by mass or more and 1.5% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0061] When the coloring agent contains ZnO, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0062] When CuO is included as the coloring agent, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 0.6% by mass or less, when the entire zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0063] As the coloring agent, TiO ２ When the coloring agent is included, the content of the coloring agent is preferably 0.005% by mass or more and 2% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less, and even more preferably 0.1% by mass or more and 0.3% by mass or less, when the total mass of the zirconia sintered body is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0064] The zirconia sintered body has an average grain size of 100 nm to 200 nm. Because the average grain size is between 100 nm and 200 nm, there are particles with grain sizes smaller than the wavelength of visible light, and the effect of scattering at grain interfaces is reduced. Furthermore, as will be described later, since the cubic phase fraction is 4.0% or more, scattering of the tetragonal phase is suppressed, and transparency is particularly improved.

[0065] The average grain size is preferably 195 nm or less, more preferably 190 nm or less. The average grain size is preferably 110 nm or more, more preferably 120 nm or more. The average grain size is preferably 110 nm or more and 195 nm or less, more preferably 120 nm or more and 190 nm or less. The average grain size can be controlled, for example, by the sintering conditions (especially the sintering temperature) when sintering the zirconia powder. The method for determining the average grain size is by the method described in the examples.

[0066] The monoclinic phase content in the crystalline phase of the zirconia sintered body is 0.5% or less. The higher the monoclinic phase content, the lower the mechanical strength and transparency. Since the monoclinic phase content of the zirconia sintered body is 0.5% or less, it has excellent mechanical strength and transparency.

[0067] The monoclinic phase ratio is preferably 0.3% or less, more preferably 0.2% or less. The monoclinic phase ratio is preferably as low as possible, for example, 0.05% or more, 0.1% or more, etc. The monoclinic phase ratio is preferably 0.05% or more and 0.3% or less, more preferably 0.1% or more and 0.2% or less. The monoclinic phase ratio is, for example, a stabilizer (especially Y ２ O ３ The content of ) can be controlled by other factors. The method for determining the monoclinic phase fraction is as described in the examples.

[0068] The tetragonal phase content of the zirconia sintered body is 20.0% to 96.0%. The higher the tetragonal phase content, the better the mechanical strength. Since the zirconia sintered body has a tetragonal phase content of 20% or more, it has excellent mechanical strength. Furthermore, since the tetragonal phase content of the zirconia sintered body is 96.0% or less, scattering of the tetragonal phase is suppressed, and transparency is particularly improved.

[0069] The tetragonal phase ratio is preferably 60.0% or less, more preferably 58.0% or less, and even more preferably 55.0% or less. The tetragonal phase ratio is preferably 25.0% or more, more preferably 30.0% or more, and even more preferably 32.0% or more. The tetragonal phase ratio is preferably 25.0% or more and 60.0% or less, more preferably 30.0% or more and 58.0% or less, and even more preferably 32.0% or more and 55.0% or less. The tetragonal phase ratio is, for example, a stabilizer (especially Y ２ O ３ The content of ) can be controlled by other factors. The method for determining the tetragonal phase ratio is as described in the examples.

[0070] The cubic phase ratio in the crystalline phase of the zirconia sintered body is 4.0% or more and 80.0% or less. Since the cubic phase does not exhibit optical anisotropy (it has optical isotropy), increasing the cubic phase ratio improves the total light transmittance (transparency). On the other hand, since the cubic phase has the characteristic of being prone to grain growth, if the cubic phase ratio is made too high, the crystal grains become larger, and the parallel light transmittance (transparency) decreases. Since the cubic phase ratio of the zirconia sintered body is 4.0% or more, scattering at grain boundaries can be suppressed, and the translucency can be improved. Furthermore, since the cubic phase ratio of the zirconia sintered body is 80.0% or less, grain growth can be suppressed, and the parallel light transmittance can be maintained at a high level.

[0071] The cubic phase ratio is preferably 75.0% or less, more preferably 70.0% or less, and even more preferably 68.0% or less. The cubic phase ratio is preferably 40.0% or more, more preferably 42.0% or more, and even more preferably 45.0% or more. The cubic phase ratio is preferably 40.0% or more and 75.0% or less, more preferably 42.0% or more and 70.0% or less, and even more preferably 45.0% or more and 68.0% or less. The cubic phase ratio is, for example, a stabilizer (especially Y ２ O ３ The content of ) can be controlled by other factors. The method for determining the cubic phase fraction is as described in the examples.

[0072] Furthermore, the crystal planes of the zirconia sintered body are unoriented. This is evident from the fact that no orientation can be confirmed in the XRD spectrum of the zirconia sintered body, and from the fact that the molding and sintering methods used to orient the crystal planes in the manufacturing method of the zirconia sintered body, described later, are not employed.

[0073] <Relative Sintering Density> The relative sintering density of the zirconia sintered body is 99.6% or higher. Because the relative sintering density of the zirconia sintered body is 99.6% or higher, scattering in residual pores is suppressed, and high light transmittance and transparency are obtained. Furthermore, because the relative sintering density of the zirconia sintered body is 99.6% or higher, it can be said to have high strength. The relative sintering density is preferably 99.7% or higher, more preferably 99.8% or higher. The relative sintering density is preferable as it is higher, for example, 99.95% or lower, 99.9% or lower, etc. The relative sintering density is preferably 99.7% or higher and 99.95% or lower, more preferably 99.8% or higher and 99.9% or lower.

[0074] <Method for measuring the relative sintering density of a zirconia sintered body> The relative sintering density refers to the relative sintering density expressed by the following formula (1). Relative sintering density (%) = (sintering density / theoretical sintering density) × 100 ... (1) Here, the theoretical sintering density (ρ ０ ρz is the value calculated by the following formula (2-1): ρ0 = 100 / [(Y / 3.987) + (100 - Y) / ρz] ... (2-1) However, ρz is the value calculated by the following formula (2-2): ρz = [124.25(100 - X) + [molecular weight of stabilizer] × X] / [150.5(100 + X)A ２ C]...(2-2) Here, the molecular weight of the stabilizer is Y ２ O ３ For this, 225.81 is used. Also, X and Y are the stabilizer concentration (mol%) and alumina concentration (weight%), respectively. Also, A and C are values ​​calculated by the following formulas (2-3) and (2-4), respectively. A = 0.5080 + 0.06980X / (100 + X) ... (2-3) C = 0.5195 - 0.06180X / (100 + X) ... (2-4) In formula (1), the theoretical sintering density varies depending on the powder composition. For example, the theoretical sintering density of yttria-containing zirconia is 6.117 g / cm³ if the yttria content is 2 mol%. ３ If it's 3 mol%, then it's 6.098 g / cm³. ３ If it's 5.5 mol%, then it's 6.051 g / cm³. ３(Al ２ O ３ (In the case of 0% by weight). Also, the theoretical sintering density (let's call it ρ1) when other components other than alumina (such as stabilizers and colorants) are included is given by: ρ1 = 100 / [(Z / V) + (100 - Z) / ρ0] ... (2 - 5) where Z is the concentration of other components other than alumina (by weight %), and V is the theoretical density of other components other than alumina (g / cm³). ３ ) The theoretical density of components other than alumina is Yb ２ O ３ 9.17 g / cm³ ３ Er ２ O ３ 8.64 g / cm³ ３ , CEO ２ 7.22 g / cm³ ３ , Sc ２ O ３ 3.86 g / cm³ ３ , Nd ２ O ３ 7.24 g / cm³ ３ La ２ O ３ 6.51 g / cm³ ３ , Tb ２ O ３ 7.81 g / cm³ ３ CaO content: 3.34 g / cm³ ３ Fe ２ O ３ 5.24 g / cm³ ３ ZnO content: 5.61 g / cm³ ３ MnO ２ 5.03 g / cm³ ３ CoO is 6.10 g / cm³ ３ , Cr ２ O ３ 5.22 g / cm³ ３ , TiO ２ 4.23 g / cm³ ３ CuO is 6.31 g / cm³ ３ , V ２ O ５ 3.36 g / cm³ ３ The sintering density will be measured using the Archimedes method.

[0075] <Total Light Transmittance> The zirconia sintered body preferably has a total light transmittance of 45% or more and 60% or less at a thickness of 1 mm. If the total light transmittance of the zirconia sintered body at a thickness of 1 mm is 45% or more, it can be said to have superior light transmission.

[0076] The total light transmittance is preferably 46.0% or more, and more preferably 48.0% or more. A higher total light transmittance is preferable, but for example, it may be 59.0% or less, 58.0% or less, etc. The total light transmittance is preferably 46.0% or more and 59.0% or less, and more preferably 48.0% or more and 58.0% or less. The method for determining the total light transmittance is by the method described in the examples.

[0077] <Parallel Light Transmittance> The zirconia sintered body preferably has a parallel light transmittance of 7.0% or more and 30.0% or less at a thickness of 1 mm. If the parallel light transmittance of the zirconia sintered body at a thickness of 1 mm is 7.0% or more, it can be said to have superior transparency.

[0078] The parallel light transmittance is preferably 8.0% or more, more preferably 10.0% or more. A higher parallel light transmittance is preferable, but for example, it may be 29.0% or less, 28.0% or less, etc. The parallel light transmittance is preferably 8.0% or more and 29.0% or less, more preferably 10.0% or more and 28.0% or less. The method for determining the parallel light transmittance is by the method described in the examples.

[0079] <Mechanical Strength> The zirconia sintered body preferably has a three-point bending strength of 500 MPa or more and 1000 MPa or less.

[0080] The three-point bending strength is more preferably 550 MPa or more, and even more preferably 600 MPa or more. The three-point bending strength is preferable as it is greater, but for example it can be 900 MPa or less, 850 MPa or less, etc. The three-point bending strength is more preferably 550 MPa or more and 900 MPa or less, and even more preferably 600 MPa or more and 850 MPa or less.

[0081] A three-point bending strength of 500 MPa or more indicates higher strength. The method for determining the three-point bending strength is as described in the examples.

[0082] <Toughness> The zirconia sintered body has a toughness value of 2.7 MPa·m² as determined by the IF method. ０．５ 5.0MPa・m or more ０．５ The following is preferable:

[0083] The toughness value is more preferably 2.8 MPa·m ０．５ More preferably 3.0 MPa·m ０．５ That concludes the explanation. A higher toughness value is preferable, for example, 4.8 MPa·m. ０．５ Below, 4.6MPa・m ０．５ The following are possible. The toughness value is more preferably 2.8 MPa·m ０．５ 4.8MPa・m or more ０．５ More preferably, 3.0 MPa·m ０．５ 4.6MPa・m or more ０．５ The following applies:

[0084] The aforementioned toughness value is 2.7 MPa·m ０．５ The above values ​​indicate higher toughness. The method for determining the toughness value is as described in the examples.

[0085] <Hydrothermal Degradation Resistance> The zirconia sintered body preferably has a monoclinic phase ratio of 2.0% or less after hydrothermal treatment at 134°C, 0.3 MPa (absolute pressure 0.3 MPa) for 75 hours. A monoclinic phase ratio of 2.0% or less after the hydrothermal treatment indicates superior resistance to hydrothermal degradation. The monoclinic phase ratio after the hydrothermal treatment is, for example, Y ２ O ３ It can be controlled by the amount added and the average crystal grain size.

[0086] The monoclinic phase ratio after the hydrothermal treatment is more preferably 1.7% or less, and even more preferably 1.5% or less. The monoclinic phase ratio after the hydrothermal treatment is preferably as low as possible, for example, 0.1% or more, or 0.2% or more. The monoclinic phase ratio after the hydrothermal treatment is more preferably 0.2% or more and 1.7% or less, even more preferably 0.1% or more and 1.5% or less, and particularly preferably 0% or more and 1.5% or less.

[0087] The zirconia sintered body according to this embodiment is not particularly limited, but can be obtained, for example, using zirconia powder described later and a method for manufacturing a zirconia sintered body described later.

[0088] The zirconia sintered body according to this embodiment can be used as an industrial component, an aesthetic component, or a dental material. More specifically, it can be used in jewelry, watch components, watch dials, artificial teeth, molding components, wear-resistant components, chemical-resistant components, and the like.

[0089] [Zirconia Powder] The zirconia powder according to this embodiment includes stabilized zirconia, which comprises zirconia and a stabilizer, wherein the stabilizer is Y ２ O ３ The Y in the stabilized zirconia includes ２ O ３ The content is between 4.0 mol% and 6.5 mol% in terms of oxides.

[0090] The zirconia powder according to this embodiment can be used in the method for manufacturing a zirconia sintered body, as described later.

[0091] The zirconia powder contains primary particles mainly composed of zirconia. All or part of the primary particles aggregate to form secondary particles. That is, the zirconia powder contains primary particles that have not aggregated and secondary particles formed from aggregated primary particles. However, the amount of primary particles that exist in the zirconia powder without becoming secondary particles and without agglomerating is very small, for example, less than 1% by mass of the total primary particles (the sum of primary particles that have not aggregated and primary particles that have aggregated into secondary particles). In other words, the zirconia powder may contain a very small amount of primary particles that have not aggregated, but is mostly composed of secondary particles. Note that "mainly composed of zirconia" means that when the primary particles are considered to be 100% by mass, the primary particles contain 70% by mass or more of zirconia. That is, in this specification, primary particles mainly composed of zirconia mean primary particles containing 70% by mass or more of zirconia. The zirconia content in the primary particles is preferably 74% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more.

[0092] As described above, the zirconia powder according to this embodiment includes stabilized zirconia.

[0093] The content of the stabilized zirconia is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the total zirconia powder is considered to be 100% by mass. The content of the stabilized zirconia can be 99% by mass or less, 98% by mass or less, etc., when the total zirconia powder is considered to be 100% by mass. The zirconia powder may also be composed only of the stabilized zirconia. In other words, the zirconia powder may be composed of only the stabilized zirconia sintered. In this case, the content of the stabilized zirconia is 100% by mass when the total zirconia powder is considered to be 100% by mass. The content of the stabilized zirconia is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, even more preferably 90% by mass or more and 98% by mass or less, and particularly preferably 95% by mass or more and 98% by mass or less, when the total zirconia powder is considered to be 100% by mass.

[0094] The stabilized zirconia comprises zirconia and a stabilizing agent.

[0095] The total content of zirconia and stabilizer in the stabilized zirconia is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the total stabilized zirconia is considered to be 100% by mass. The total content of zirconia and stabilizer can be 99% by mass or less, 98% by mass or less, etc., when the total stabilized zirconia is considered to be 100% by mass. Alternatively, the stabilized zirconia may consist only of zirconia and stabilizer. In this case, the total content of zirconia and stabilizer is 100% by mass when the total content of the stabilized zirconia is considered to be 100% by mass. The total content of zirconia and stabilizer in the stabilized zirconia is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, even more preferably 90% by mass or more and 98% by mass or less, and particularly preferably 95% by mass or more and 98% by mass or less, when the total stabilized zirconia is considered to be 100% by mass.

[0096] The aforementioned stabilizer is Y ２ O ３ Includes.

[0097] The Y in the stabilized zirconia ２ O ３ The content is between 4.0 mol% and 6.5 mol% in terms of oxide. Y in stabilized zirconia ２ O ３ Since the content exceeds 4.0 mol% in terms of oxide, the cubic phase ratio of the sintered body obtained by sintering the zirconia powder can be made 4.0% or more. Since the cubic phase ratio of the sintered body obtained by sintering the zirconia powder is 4.0% or more, scattering at grain boundaries can be suppressed and light transmittance can be improved. Also, Y ２ O ３ Since the content of is 6.5 mol% or less in terms of oxide, the sintered body obtained by sintering the zirconia powder has excellent mechanical strength. Furthermore, the Y in the stabilized zirconia ２ O ３ Since the content exceeds 4.0 mol% in terms of oxide, the monoclinic phase ratio of the sintered body obtained by sintering the zirconia powder can be made 0.5% or less. The more monoclinic phase is present, the lower the mechanical strength and transparency. On the other hand, the sintered body obtained by sintering the zirconia powder has a monoclinic phase ratio of 0.5% or less, so it has excellent mechanical strength and transparency.

[0098] The Y in the stabilized zirconia ２ O ３ The content of is preferably more than 5.2 mol% in terms of oxide, more preferably 5.3 mol% or more. The Y in the stabilized zirconia ２ O ３ The content of is preferably 6.4 mol% or less in terms of oxide, more preferably 6.3 mol% or less. The Y in the stabilized zirconia ２ O ３ The content is preferably more than 5.2 mol% and 6.4 mol% or less in terms of oxides, and more preferably 5.3 mol% or more and 6.3 mol% or less.

[0099] The aforementioned stabilizer further includes Y２ O ３ Other stabilizers may be included. These other stabilizers are not particularly limited, but include, for example, Yb ２ O ３ Er ２ O ３ , CEO ２ , Sc ２ O ３ , Nd ２ O ３ La ２ O ３ , Tb ２ O ３ Examples include CaO, etc. These other stabilizers may be present in one or more forms.

[0100] Y ２ O ３ If other stabilizers are included, it is preferable that the content is within a range that does not significantly affect the transparency and light transmission of the sintered body obtained by sintering the zirconia powder. ２ O ３ If other stabilizers are included, the content of the other stabilizers in the stabilized zirconia is preferably 0.01 mol% or more and 2.5 mol% or less in terms of oxide. The content of the other stabilizers in the stabilized zirconia is more preferably 0.05 mol% or more in terms of oxide, and even more preferably 0.10 mol% or more. The content of the other stabilizers in the stabilized zirconia is more preferably 2.0 mol% or less in terms of oxide, and even more preferably 1.5 mol% or less. The content of the other stabilizers in the stabilized zirconia is more preferably 0.05 mol% or more and 2.0 mol% or less in terms of oxide, and even more preferably 0.10 mol% or more and 1.5 mol% or less in terms of oxide.

[0101] The total amount of stabilizer in the stabilized zirconia is preferably 4.1 mol% to 6.5 mol% in terms of oxide. When the total amount of stabilizer is 4.1 mol% or more in terms of oxide, the monoclinic phase fraction can be reduced. Furthermore, when the total amount of stabilizer is 6.5 mol% or less in terms of oxide, the cubic phase fraction, which has low mechanical properties (strength, toughness), can be reduced, and the tetragonal phase fraction, which has high mechanical properties, can be increased.

[0102] The total amount of the stabilizer is more preferably 4.5 mol% or more, even more preferably 5.0 mol% or more, and particularly preferably 5.2 mol% or more, on an oxide basis. The total amount of the stabilizer is more preferably 6.4 mol% or less, even more preferably 6.3 mol% or less, and particularly preferably 6.0 mol% or less, on an oxide basis. The total amount of the stabilizer is more preferably 4.5 mol% or more and 6.4 mol% or less, even more preferably 5.0 mol% or more and 6.4 mol% or less, on an oxide basis, and particularly preferably 5.2 mol% or more and 6.0 mol% or less.

[0103] The zirconia content in the stabilized zirconia is preferably 80% by mass or more and 99% by mass or less. The zirconia content in the stabilized zirconia is more preferably 85% by mass or more, and even more preferably 90% by mass or more. The zirconia content in the stabilized zirconia is more preferably 98% by mass or less, and even more preferably 97% by mass or less. The zirconia content in the stabilized zirconia is more preferably 85% by mass or more and 98% by mass or less, and even more preferably 90% by mass or more and 97% by mass or less.

[0104] The zirconia powder is composed of Al relative to the total amount of zirconia powder. ２ O ３ It is preferable that the zirconia powder contains (alumina) in an amount of 0.15% by mass or less. ２ O ３ When it contains Al, it functions as a sintering aid, resulting in excellent low-temperature sintering properties. ２ O ３If the content is 0.15% by mass or less, scattering due to the precipitated phase (grain boundaries) of alumina (impurity) in the sintered body obtained by sintering the zirconia powder is reduced, thus maintaining high light transmittance and transparency.

[0105] The zirconia powder is Al ２ O ３ If it includes, the Al ２ O ３ The content of is more preferably 0.01% by mass or more, and even more preferably 0.05% by mass or more. The zirconia powder is Al ２ O ３ If it includes, the Al ２ O ３ The content of is more preferably 0.13% by mass or less, and even more preferably 0.10% by mass or less. The zirconia powder is Al ２ O ３ If it includes, the Al ２ O ３ The content is more preferably 0.01% by mass or more and 0.13% by mass or less, and even more preferably 0.05% by mass or more and 0.10% by mass or less.

[0106] In addition to alumina, the zirconia powder may also contain sinterable ceramics, thermosetting resins, and other materials to improve properties such as strength.

[0107] The zirconia powder may contain one or more elements selected from the group consisting of Fe, V, Mn, Co, Zn, Cu, and Ti, within a range that does not significantly affect transparency and light transmission. Including one or more elements selected from the group consisting of Fe, V, Mn, Co, Zn, Cu, and Ti as coloring elements allows for suitable coloring of the zirconia sintered body obtained by sintering the zirconia powder.

[0108] The form of the coloring element is not particularly limited and can be added in the form of oxides, chlorides, etc. Specific examples of colorants containing the coloring element include Fe ２ O ３ , V ２ O ５ MnO ２ , CoO, ZnO, CuO, TiO ２Examples include the above. Preferably, the coloring agent is added to the zirconia powder as a mixture.

[0109] Fe as the coloring agent ２ O ３ When the coloring agent is included, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 0.5% by mass or less, when the total zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0110] V as the aforementioned coloring agent ２ O ５ When the coloring agent is included, the amount is preferably 0.005% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.1% by mass or less, when the total amount of zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0111] As the coloring agent, MnO ２ When the coloring agent is included, the amount is preferably 0.005% by mass or more and 2% by mass or less, and more preferably 0.1% by mass or more and 1.1% by mass or less, when the total amount of zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0112] When the coloring agent contains CoO, the content of the coloring agent is preferably 0.005% by mass or more and 2% by mass or less, and more preferably 0.01% by mass or more and 1.5% by mass or less, when the total zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0113] When the coloring agent contains ZnO, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, when the total zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0114] When CuO is included as the coloring agent, the content of the coloring agent is preferably 0.005% by mass or more and 1% by mass or less, and more preferably 0.05% by mass or more and 0.6% by mass or less, when the total zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended coloring is easily obtained. In other words, the color tone can be easily adjusted.

[0115] As the coloring agent, TiO ２ When the coloring agent is included, the content of the coloring agent is preferably 0.005% by mass or more and 2% by mass or less, more preferably 0.01% by mass or more and 1% by mass or less, and even more preferably 0.1% by mass or more and 0.3% by mass or less, when the total zirconia powder is considered to be 100% by mass. When the content of the coloring agent is 0.005% by mass or more, the intended color is easily obtained. In other words, the color tone can be easily adjusted.

[0116] <Pore Distribution> 1. Peak Top Diameter of Primary Particle Gap The zirconia powder preferably has a peak top diameter of 20 nm to 85 nm in the range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method. The peak top diameter is preferably 25 nm or more, more preferably 30 nm, even more preferably 32 nm, and particularly preferably 35 nm or more. The peak top diameter is preferably 65 nm or less, more preferably 60 nm or less, even more preferably 57 nm or less, and particularly preferably 54 nm or less. When multiple peaks exist in the range of 10 nm to 200 nm in the pore distribution, "the peak top diameter of the pore volume distribution is 20 nm to 85 nm" as used herein means that all peak top diameters in the range of 10 nm to 200 nm in the pore distribution are within the range of 20 nm to 85 nm.

[0117] 2. Pore distribution width of primary particle gaps The zirconia powder preferably has a pore distribution width of 40 nm to 105 nm in the range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method. The pore distribution width is preferably 43 nm or more, more preferably 46 nm or more, even more preferably 50 nm or more, and particularly preferably 55 nm or more. The pore distribution width is preferably 100 nm or less, more preferably 95 nm or less, even more preferably 90 nm or less, particularly preferably 85 nm or less, and especially preferably 80 nm or less. Here, the pore distribution width refers to the width of the peak where the log differential pore volume is 0.1 ml / g or more. Furthermore, if multiple peaks exist in the pore distribution range of 10 nm to 200 nm, the phrase "pore distribution width is 40 nm to 105 nm" as used herein means that, in a graph showing the pore distribution with the horizontal axis representing pore diameter and the vertical axis representing log differential pore volume, the point where the graph first intersects with the log differential pore volume of 0.1 mL / g (the point where it intersects while rising) is defined as the minimum diameter, and the point where it intersects with the log differential pore volume of 0.1 mL / g again (the point where it intersects while descending) is defined as the maximum diameter, and the difference between the maximum and minimum diameters is 40 nm to 105 nm.

[0118] 3. Pore Volume of Primary Particle Gaps The zirconia powder preferably has a pore volume of 0.2 ml / g or more and less than 0.5 ml / g in the range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method. The total pore volume is preferably 0.22 ml / g or more, more preferably 0.25 ml / g or more, even more preferably 0.3 ml / g or more, particularly preferably 0.35 ml / g or more, and especially preferably 0.4 ml / g or more. The total pore volume is preferably 0.48 ml / g or less, more preferably 0.46 ml / g or less, and particularly preferably 0.44 ml / g or less.

[0119] The "range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method" is the range in which pores as primary particle gaps can exist in zirconia powder. In the range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method, if the peak top diameter of the pore volume distribution is 20 nm to 85 nm and the pore distribution width is 40 nm to 105 nm, then the size of each pore (each primary particle gap) is small and uniform (the distribution is sharp). Therefore, each primary particle constituting the secondary particle is uniformly and densely aggregated, and there are no large pores. Here, zirconia particles (including primary and secondary particles) have the characteristic that they are difficult to sinter if the pore volume is large. In other words, in order to sinter at low temperatures, it is necessary not only to reduce the size of pores originating from the primary particle gaps within the secondary particles and sharpen the distribution, but also to simultaneously reduce the pore volume originating from the primary particle gaps. Therefore, if the pore volume in the range of 10 nm to 200 nm in the pore distribution based on the mercury intrusion method is 0.2 ml / g to less than 0.5 ml / g, the pore volume originating from the primary particle gaps is small, and there are no large pores, making it possible to obtain a sintered body with high sintering density.

[0120] <Particle size D ５０ > Particle size D of the zirconia powder ５０ The particle size D is preferably 0.1 μm or more and 0.7 μm or less. ５０ The particle size D is preferably 0.12 μm or larger, more preferably 0.14 μm or larger, even more preferably 0.16 μm or larger, and particularly preferably 0.2 μm or larger. ５０ The particle size D of the zirconia powder is preferably 0.62 μm or less, more preferably 0.55 μm or less, even more preferably 0.48 μm or less, particularly preferably 0.4 μm or less, especially preferably 0.3 μm or less, and exceptionally preferably less than 0.3 μm. ５０ When the particle size is 0.7 μm or less, the particle size of the secondary particles is relatively small, which allows for a smaller gap between secondary particles. As a result, it exhibits excellent low-temperature sinterability. Furthermore, because the gap between secondary particles is small, a sintered body with high sintering density can be obtained.

[0121] <Specific Surface Area> The specific surface area of ​​the zirconia powder is 20 m². ２ / g or more 60m ２ It is preferable that the amount is less than or equal to / g. The specific surface area is preferably 22m². ２ / g or more, more preferably 24m ２ / g or more, more preferably 30m ２ / g or more, particularly preferably 35m ２ It is 1 / g or more. The specific surface area is preferably 57 m². ２ / g or less, more preferably 54m ２ / g, more preferably 52m ２ / g, particularly preferably 49m ２ It is / g.

[0122] The zirconia powder was processed using the cold isostatic pressing method (CIP) at a rate of 2.0 t / cm². ２ When molded under this pressure, it is preferable that the relative molded density be between 40% and 55%. Here, the relative molded density is a value calculated by the following formula (3). Relative molded density (%) = (Molded density / Theoretical sintered density) × 100 ... (3) Theoretical sintered density (ρ ０ The value (assumed to be 2.0 t / cm²) is calculated using formula (2-1) described in the section "Method for measuring the relative sintering density of a zirconia sintered body" above. ２ When molded at this pressure, it is easy to achieve a relative molding density of 40% to 55%, therefore, the zirconia powder is applied at a rate of 1.0 t / cm³. ２ The above is 2.5 t / cm ２ By performing the preliminary sintering in step B described later and the final sintering in step C described later on a molded body formed at the following pressure, a zirconia sintered body can be obtained having an average grain size of 100 nm or more and 200 nm or less, a monoclinic phase ratio of 0.5% or less, a tetragonal phase ratio of 20.0% or more and 96.0% or less, a cubic phase ratio of 4.0% or more and 80.0% or less, and a relative sintering density of 99.6% or more.

[0123] The relative molding density is more preferably 43.0% or more, and even more preferably 45.0% or more. The relative molding density is more preferably 50.0% or less, and even more preferably 48.0% or less. The relative molding density is more preferably 40% to 48%, even more preferably 43.0% to 50.0%, and particularly preferably 45.0% to 48.0%. The relative molding density refers to the value obtained by the method described in the examples.

[0124] The zirconia powder according to this embodiment has been described above.

[0125] [Method for Manufacturing Zirconia Powder] An example of a method for manufacturing zirconia powder is described below. However, the method for manufacturing zirconia powder is not limited to the example below.

[0126] The method for producing zirconia powder according to this embodiment includes: Step 1: Heating a zirconium salt solution and a sulfated chloride solution separately to 95°C or higher and 100°C or lower; Step 2: Contacting the heated zirconium salt solution and the heated sulfated chloride solution so that the concentration of the mixture does not change from the start to the end of contact, thereby obtaining a reaction solution containing basic zirconium sulfate as a mixture; Step 3: Aging the reaction solution containing basic zirconium sulfate obtained in Step 2 at 95°C or higher for 3 hours or more; Step 4: Adding a stabilizer to the aged reaction solution containing basic zirconium sulfate obtained in Step 3; Step 5: Adding alkali to the reaction solution containing basic zirconium sulfate obtained in Step 4 to obtain a zirconium-containing hydroxide; and Step 6: Heat treating the zirconium-containing hydroxide obtained in Step 5 to obtain zirconia powder, wherein in Step 2, from the start to the end of contact, the SO2 in the mixture is... ４ ２－ / ZrO ２ Maintain the weight ratio within the range of 0.3 to 0.8, and maintain the temperature of the mixture at 95°C or higher. The process will be explained in detail below.

[0127] <Step 1> In Step 1, the starting materials, a zirconium salt solution and a sulfated chlorine solution, are heated separately to a temperature of 95°C to 100°C. The zirconium salt used to prepare the zirconium salt solution can be any salt that supplies zirconium ions, such as zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, etc. One or more of these can be used. Among these, zirconium oxychloride is preferred because it offers high productivity on an industrial scale.

[0128] The solvent used to prepare the zirconium salt solution can be selected according to the type of zirconium salt, etc. Water (pure water, deionized water, etc.) is generally preferred.

[0129] The concentration of the zirconium salt solution is not particularly limited, but generally it is zirconium oxide (ZrO) per 1000 g of solvent. ２ It is preferable that the amount contained is 5 to 250 g in terms of conversion, and more preferably 20 to 150 g.

[0130] Any sulfated agent that reacts with zirconium ions to produce sulfates (i.e., a sulfated reagent) can be used, and examples include sodium sulfate, potassium sulfate, ammonium sulfate, potassium bisulfate, sodium bisulfate, potassium disulfate, sodium disulfate, and sulfur trioxide. The sulfated agent may be in powder or solution form, but a solution (especially an aqueous solution) is preferred. As for the solvent, the same solvent used to prepare the zirconium salt solution can be used.

[0131] The acid concentration of the zirconium salt solution is preferably 0.1 to 2.0 N. By setting the acid concentration within this range, the aggregation state of the particles constituting the zirconia powder can be controlled to a suitable state. The acid concentration can be adjusted, for example, by using hydrochloric acid, nitric acid, sodium hydroxide, etc.

[0132] The concentration of the sulfated chloride (the sulfated chloride solution) is not particularly limited, but it is generally preferable to use 5 to 250 g of sulfated chloride per 1000 g of solvent, and more preferably 20 to 150 g.

[0133] The material of the containers used to prepare the zirconium salt solution and the sulfated chloride solution is not particularly limited, as long as they have a capacity to sufficiently stir each of the solutions. However, it is preferable to have equipment that can appropriately heat each solution so that its temperature does not fall below 95°C. The heating temperature of the zirconium salt solution and the sulfated chloride solution should be between 95°C and 100°C, and preferably 97°C or higher. If step 2 is carried out while the temperature of the zirconium salt solution and the sulfated chloride solution is below 95°C, the zirconium salt solution and the sulfated chloride will not react sufficiently, and the yield will decrease.

[0134] <Step 2> In Step 2, the heated zirconium salt solution and the heated sulfated chloride solution are brought into contact so that the concentration of the mixture does not change from the start to the end of contact, thereby obtaining a reaction solution containing basic zirconium sulfate as a mixture. Here, from the start to the end of contact, the SO in the mixture ４ ２－ / ZrO ２ Maintain the weight ratio within the range of 0.3 to 0.8, and maintain the temperature of the mixture at 95°C or higher. Step 2 will now be explained with reference to the drawings.

[0135] Figure 1 is a schematic diagram illustrating the method for producing zirconia powder according to this embodiment. As shown in Figure 1, container 10 is connected to one upper end (left side in Figure 1) of the T-tube 20 via valve 12. Container 30 is connected to the other upper end (right side in Figure 1) of the T-tube 20 via valve 32. Container 10 stores a zirconium solution heated to 95°C or higher and 100°C or lower. Container 30 stores a sulfated chloride solution heated to 95°C or higher and 100°C or lower. In step 2, the zirconium solution and the sulfated chloride solution are brought into contact by opening valve 12 and valve 32. The resulting mixture (basic zirconium sulfate-containing reaction solution) flows immediately into the aging container 40 from the bottom of the T-tube 20. In step 2, this method ensures that the concentration of the reaction solution (concentration of the reaction solution in the T-tube 20) does not change from the start to the end of contact between the zirconium solution and the sulfated chloride solution. In step 2, SO4 is used from the start to the end of contact. ４ ２－ / ZrO ２ Because the concentration change is suppressed, a uniform reactant is obtained. By employing such a process (step 2), the peak top diameter, pore volume, and pore distribution width of the primary particles can be controlled. SO in the mixed solution in step 2 ４ ２－ / ZrO ２ The weight ratio is preferably in the range of 0.3 to 0.8, more preferably 0.4 to 0.7, and even more preferably 0.45 to 0.65. ４ ２－ / ZrO ２ By setting the weight ratio to 0.3 or higher, the yield of the reaction product, basic zirconium sulfate, can be increased. Also, the SO in the mixture ４ ２－ / ZrO ２ By setting the weight ratio to 0.8 or less, the formation of soluble zirconium sulfate salts can be suppressed, and the decrease in the yield of basic zirconium sulfate can be suppressed. In step 2, it is preferable to install heaters in the piping (for example, the T-joint 20) that supplies each solution in order to maintain the temperature of the mixed solution at 95°C or higher.

[0136] The following is a detailed explanation of an example of step 2. As the T-tube 20, a T-tube with a diameter L1 of 10 mm at one upper end (left side in Figure 1), a diameter L2 of 10 mm at the other upper end (right side in Figure 1), and a diameter L3 of 15 mm at the bottom is used, and 213 g of 25% by mass sodium sulfate aqueous solution and ZrO ２ When contacting 450 g of a 16% by mass aqueous solution of zirconium oxychloride, the time from the start of contact to the end of contact (until the zirconium chloride aqueous solution in container 10 and the sulfated chloride solution in container 30 are gone) (contact time) is preferably 30 to 300 seconds, more preferably 60 to 200 seconds, and even more preferably 90 to 150 seconds.

[0137] <Step 3> In Step 3, the reaction solution containing basic zirconium sulfate obtained in Step 2 is aged at 95°C or higher for 3 hours or more. In Step 3, for example, the reaction solution containing basic zirconium sulfate that flows into the aging container 40 is stirred with a stirrer 42 and aged at 95°C or higher for 3 hours or more. There is no particular upper limit to the aging time, but for example, it is 7 hours or less. The temperature (aging temperature) of the mixed solution (reaction solution containing basic zirconium sulfate) in Step 3 is preferably 95°C or higher, more preferably 97°C or higher and 100°C or lower. By setting the aging temperature to 95°C or higher and the aging time to 3 hours or more, sufficient basic zirconium sulfate can be produced and the yield can be increased. The above mixed solution contains basic zirconium sulfate as its main component and is a basic zirconium sulfate slurry.

[0138] <Step 4> In Step 4, a stabilizer is added to the aged basic zirconium sulfate-containing reaction solution obtained in Step 3.

[0139] <Step 5> In Step 5, an alkali is added to the reaction solution containing basic zirconium sulfate obtained in Step 4 to carry out a neutralization reaction. By neutralization, zirconium-containing hydroxide is produced. The alkali is not limited and examples include caustic soda, sodium carbonate, ammonia, hydrazine ammonium bicarbonate, etc. The concentration of the alkali is not particularly limited, but it is diluted with water and usually a concentration of 5 to 30% is used. There are two methods for adding the alkali: (1) adding the alkali solution to the reaction solution containing basic zirconium sulfate, and (2) adding the reaction solution containing basic zirconium sulfate to the alkali solution, but neither method is particularly limited and either method may be used. After neutralization, the slurry is filtered to obtain zirconium-containing hydroxide. It is preferable to remove impurities from this zirconium-containing hydroxide by washing it with pure water, etc., as needed. After washing, drying may be carried out as needed.

[0140] <Step 6> In Step 6, the zirconium-containing hydroxide obtained in Step 5 is heat-treated (calcined) to oxidize the zirconium-containing hydroxide and obtain zirconia powder. The heat treatment temperature (calcination temperature) and heat treatment time (calcination time) of the zirconium-containing hydroxide are not particularly limited, but are usually performed at around 600 to 1050°C for 1 to 10 hours. The calcination temperature is more preferably 650°C to 1000°C, and even more preferably 700°C to 980°C. The calcination time is more preferably 2 to 6 hours, and even more preferably 2 to 4 hours. By setting the heat treatment temperature to 600°C to 1000°C, the specific surface area of ​​the obtained zirconia powder is set to a suitable range (20 m²). ２ / g or more 80m ２ The density can be set to less than or equal to 1050°C. Furthermore, by setting the heat treatment temperature to 600°C or higher and 1050°C or lower, the pore distribution of the resulting zirconia powder can be set to a suitable range. The heat treatment atmosphere is not particularly limited, but it is usually sufficient to use air or an oxidizing atmosphere.

[0141] <Step 7> After Step 6, the obtained zirconia powder may be pulverized to form a slurry if necessary. In this case, a binder may be added to improve moldability. If slurrying is not performed (pulverization is not performed), the binder and zirconia powder may be uniformly mixed in a kneader. An organic binder is preferred as the binder. An organic binder is easily removed from the molded body in a heating furnace with an oxidizing atmosphere, and a degreased body can be obtained, so that impurities are less likely to remain in the sintered body in the end. Examples of the organic binder include those that dissolve in alcohol, or those that dissolve in a mixture of two or more selected from the group consisting of alcohol, water, aliphatic ketones, and aromatic hydrocarbons. Examples of the organic binder include at least one selected from the group consisting of polyethylene glycol, glycol fatty acid ester, glycerin fatty acid ester, polyvinyl butyral, polyvinyl methyl ether, polyvinyl ethyl ether, and vinyl propionate. The organic binder may further contain one or more thermoplastic resins that are insoluble in alcohol or the above mixture. After adding the organic binder, the desired zirconia powder can be obtained by drying, grinding, and other processes using known methods. The grinding in step 7 allows for, for example, the particle size D of the zirconia powder to be reduced. ５０ This allows for control of the particle size D of the zirconia powder obtained in step 5. For example, grinding is performed according to the state of the zirconia powder obtained in step 5. ５０ It can be controlled.

[0142] When adding a sintering aid (e.g., alumina), zirconia powder containing the sintering aid can be obtained by adding and mixing it after step 6. A more detailed method of mixing is to disperse it in pure water or the like to form a slurry and then wet mix it. Alternatively, when performing step 7, the sintering aid may be added at the time of step 7.

[0143] The zirconia powder according to this embodiment has been described above.

[0144] [Method for Manufacturing Zirconia Sintered Bodies] An example of a method for manufacturing zirconia sintered bodies will be described below. However, the method for manufacturing zirconia sintered bodies of the present invention is not limited to the following example.

[0145] The method for producing a zirconia sintered body according to this embodiment involves distributing zirconia powder at a rate of 1.0 t / cm². ２ The above is 2.5 t / cm ２ The process includes: step A, molding at the following pressure to obtain a molded body; step B, pre-sintering the molded body under normal pressure, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a pre-sintered body; and step C, fully sintering the pre-sintered body under the conditions of a pressure of 50 MPa or higher and 200 MPa or lower, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a sintered body.

[0146] In the method for manufacturing a zirconia sintered body according to this embodiment, first, zirconia powder is prepared. As the zirconia powder, the one described in the section on [Zirconia Powder] can be used.

[0147] Next, the zirconia powder was added at a rate of 1.0 t / cm². ２ The above is 2.5 t / cm ２ The molded body is obtained by molding at the following pressure (Step A). ​​Molding can be performed using a commercially available mold molding machine or cold isostatic pressing (CIP). Alternatively, the zirconia powder may be pre-molded using a mold molding machine, and then the final molding may be performed by press molding. The pressure is preferably 1.3 t / cm². ２ More preferably, 1.5 t / cm ２ That is all. The pressure is preferably 2.3 t / cm². ２ The following is more comfortable: 2.2 t / cm ２ The following applies: The pressure is preferably 1.3 t / cm². ２ 2.3t / cm or more ２ More preferably, 1.5 t / cm ２ 2.2t / cm or more ２ The following applies:

[0148] Next, the molded body is pre-sintered under normal pressure, at a temperature of 1150°C to 1250°C, and for 1 to 5 hours to obtain a pre-sintered body (Step B). In this embodiment, since the molded body is pre-sintered under relatively low temperature conditions of 1150°C to 1250°C and for 1 to 5 hours under normal pressure, a pre-sintered body with suppressed grain growth can be obtained. Because grain growth is suppressed, it is possible to obtain a zirconia sintered body with high light transmittance and high transparency. In particular, when the proportion of the cubic phase is high, grain growth proceeds isotropically, so growth tends to be promoted between adjacent crystal grains. However, since the molded body is pre-sintered under relatively low temperature conditions of 1150°C to 1250°C and for 1 to 5 hours under normal pressure, grain growth can be suppressed even if the proportion of the cubic phase is high.

[0149] The pre-sintering temperature is preferably 1160°C or higher, more preferably 1170°C or higher. The pre-sintering temperature is preferably 1245°C or lower, more preferably 1240°C or lower. The pre-sintering temperature is preferably 1160°C or higher and 1245°C or lower, more preferably 1170°C or higher and 1240°C or lower. The pre-sintering time is preferably 1.2 hours or more, more preferably 1.5 hours or more. The pre-sintering time is preferably 4.7 hours or less, more preferably 4.5 hours or less. The pre-sintering time is preferably 1.2 hours or more and 4.7 hours or lower, more preferably 1.5 hours or more and 4.5 hours or lower. The pre-sintering atmosphere can be in the air or an oxidizing atmosphere. Pre-sintering can be carried out under normal pressure, and pressurization is not particularly necessary.

[0150] Next, the pre-sintered body is subjected to final sintering under the conditions of a pressure of 50 MPa to 200 MPa, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours to obtain a sintered body (Step C). The final sintering is not particularly limited as long as the pressure of 50 MPa to 200 MPa and the temperature of 1150°C to 1250°C can be maintained, but for example, an apparatus employing the HIP (Hot Isostatic Pressing) method can be used. In Step B, the molded body is pre-sintered under the conditions of atmospheric pressure, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours, so that the zirconia powder particles bond to each other appropriately during the pre-sintering process, and the pores (interparticle gaps of zirconia powder) in the molded body can be made into closed pores. In other words, pre-sintering can change the pores from a state where the pores are connected to each other (open pores) to isolated closed pores surrounded by zirconia powder bonds. Then, in step C, the pre-sintered body, in which the pores are closed pores, is subjected to main sintering under conditions of a pressure of 50 MPa to 200 MPa, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours, thereby almost completely eliminating the closed pores. Specifically, the pressure applied during main sintering compresses the closed pores to the smallest possible size, and elemental diffusion (flow of elements) during main sintering pushes the pores out of the sintered body, thus almost completely eliminating the closed pores. By removing the pores, the total light transmittance (transparency) and parallel light transmittance (transparency) can be improved. Furthermore, since the pre-sintered body is subjected to main sintering under conditions of a pressure of 50 MPa to 200 MPa, a temperature of 1150°C to 1250°C, and a time of 1 to 5 hours, the relative sintering density can be set to 99.6% or higher.

[0151] The sintering pressure is preferably 55 MPa or higher, more preferably 60 MPa or higher. The sintering pressure is preferably 198 MPa or lower, more preferably 195 MPa or lower. The sintering pressure is preferably 55 MPa or higher and 198 MPa or lower, more preferably 60 MPa or higher and 195 MPa or lower. The sintering temperature is preferably 1160°C or higher, more preferably 1170°C or higher. The sintering temperature is preferably 1245°C or lower, more preferably 1240°C or lower. The sintering temperature is preferably 1160°C or higher and 1245°C or lower, more preferably 1170°C or higher and 1240°C or lower. The sintering time is preferably 1.2 hours or more, more preferably 1.5 hours or more. The sintering time is preferably 4.7 hours or less, more preferably 4.5 hours or less. The sintering time is preferably 1.2 hours or more and 4.7 hours or lower, more preferably 1.5 hours or more and 4.5 hours or lower.

[0152] After the preliminary sintering in step B, the material is usually cooled to below 40°C, and then the main sintering (step C) is performed. This is because step B is sintering at atmospheric pressure, while step C is sintering with pressure, so different sintering equipment is used. In other words, after preliminary sintering, the material is cooled, removed from the equipment used for preliminary sintering, placed in the equipment for main sintering, and then the main sintering is performed. Therefore, after the preliminary sintering in step B, the material is usually cooled to below 40°C, and then reheated before the main sintering is performed. However, the present invention is not limited to this example. For example, if steps B and C are performed in the same equipment, the main sintering may be performed immediately after the preliminary sintering in step B without cooling.

[0153] The method for manufacturing a stabilized zirconia sintered body according to this embodiment has been described above.

[0154] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. The zirconia powder and zirconia sintered bodies in the examples and comparative examples contain hafnium oxide as an unavoidable impurity at a concentration of 1.3 to 2.5% by mass relative to the zirconium oxide (calculated by the following formula (X)). <Formula (X)> ([Mass of hafnium oxide] / ([Mass of zirconium oxide] + [Mass of hafnium oxide])) × 100 (%)

[0155] [Preparation of Zirconia Powder] (Production Example 1) 213 g of 25% by mass sodium sulfate aqueous solution and ZrO ２ 450 g each of 16% by mass of zirconium oxychloride aqueous solution (acid concentration: 1N) was heated separately to 95°C (Step 1). Then, the SO2 mixture was heated. ４ ２－ / ZrO ２ The heated aqueous solutions were brought into contact with each other over a period of 2 minutes so that the mass ratio was 0.50 (Step 2). Next, the resulting reaction solution containing basic zirconium sulfate was aged at 95°C for 4 hours to obtain basic zirconium sulfate (Step 3). Next, the aged solution was cooled to room temperature, and then Y ２ O ３ A 10% by mass aqueous solution of yttrium chloride is converted to Y ２ O ３The mixture was added to a total concentration of 4.1 mol% and mixed uniformly (Step 4). Next, a 25% by mass aqueous sodium hydroxide solution was added to the resulting mixed solution and neutralized until the pH reached 13 or higher to form a hydroxide precipitate (Step 5). The obtained hydroxide precipitate was filtered and thoroughly washed with water, and the obtained hydroxide was dried at 105°C for 24 hours. The dried hydroxide was heat-treated in air at 960°C (calcination temperature) for 2 hours to obtain unground zirconia powder (yttria-stabilized zirconia powder) (Step 6). To the obtained unground yttria-stabilized zirconia powder, alumina powder with an average primary particle size of 0.1 μm was added at a concentration of 0.1% by mass relative to the yttria-stabilized zirconia powder, and the mixture was ground and mixed for 40 hours in a wet ball mill using water as the dispersion medium. Zirconia beads with a diameter of φ5 mm were used for grinding. The zirconia slurry obtained after grinding was dried at 110°C to obtain the zirconia powder according to Example 1. The above operations were specifically performed using the apparatus described with reference to Figure 1.

[0156] (Production Example 2 - Production Example 16) Y ２ O ３ Except for changing the amount of yttrium chloride aqueous solution added so that the content of the alumina powder was as shown in Table 1, the zirconia powders of Production Examples 2-16 were obtained in the same manner as in Production Example 1.

[0157] (Manufacturing Example 17) Y ２ O ３ The amount of yttrium chloride aqueous solution added was changed so that the content of the substance was as shown in Table 1, and calcium carbonate (CaCO3) was added at the same time as the yttrium chloride aqueous solution. ３ Except for adding ) in an amount equivalent to 0.5 mol% in terms of CaO, the zirconia powder of Production Example 17 was obtained in the same manner as in Production Example 1.

[0158] (Manufacturing Example 18) Y ２ O ３ The amount of yttrium chloride aqueous solution added was changed so that the content of Yb was as shown in Table 1, and at the same time as adding the yttrium chloride aqueous solution, a 10% by mass ytterbium chloride aqueous solution was added. ２O ３ Except for adding the substance to a converted amount of 0.3 mol%, the zirconia powder of Production Example 18 was obtained in the same manner as in Production Example 1.

[0159] (Manufacturing Example 19) Y ２ O ３ The amount of yttrium chloride aqueous solution added was changed so that the content of Er was as shown in Table 1, and at the same time as adding the yttrium chloride aqueous solution, 10% by mass of erbium chloride aqueous solution was added. ２ O ３ Except for adding the substance in a converted amount of 0.2 mol%, the zirconia powder of Production Example 19 was obtained in the same manner as in Production Example 1.

[0160]

[0161] [Preparation of Zirconia Sintered Bodies] <1. Molded Bodies> First, the zirconia powder of the production example was molded using the cold isostatic pressing method (CIP) to obtain molded bodies. The molding pressure was as shown in Table 1. At this time, the relative molding density of the molded bodies was determined by (3) below. The results are shown in Table 1.

[0162] <2. Pre-sintered bodies> Next, the molded bodies were pre-sintered at atmospheric pressure (1 atmosphere) at the pre-sintering temperature and time shown in Table 2 to obtain pre-sintered bodies. The pre-sintered bodies of Examples 1 to 11 are obtained by pre-sintering the molded bodies of Manufacturing Examples 1 to 11, respectively. The pre-sintered body of Example 12 is obtained by pre-sintering the molded body of Manufacturing Example 5. The pre-sintering conditions for Example 5 and Example 12 are different (the molding conditions are the same). The pre-sintered bodies of Comparative Examples 1 to 5 are obtained by pre-sintering the molded bodies of Manufacturing Examples 12 to 16, respectively. The pre-sintered body of Comparative Example 6 is obtained by pre-sintering the molded body of Manufacturing Example 1. The pre-sintering conditions for Example 1 and Comparative Example 6 are different (the molding conditions are the same). The pre-sintered body of Comparative Example 7 is obtained by pre-sintering the molded body of Manufacturing Example 2. The pre-sintering conditions for Example 2 and Comparative Example 7 are different (the molding conditions are the same). The pre-sintered bodies of Examples 13-15 were obtained by pre-sintering the molded bodies of Manufacturing Examples 17-19, respectively. The relative sintering density (pre-sintered body density) of the obtained pre-sintered bodies was determined as follows. The results are shown in Table 2.

[0163] [Relative Sintering Density] The relative sintering density is the relative sintering density expressed by the following formula (1). Relative sintering density (%) = (Sintering density / Theoretical sintering density) × 100 ... (1) Here, the theoretical sintering density (ρ ０ ρz is the value calculated by the following formula (2-1): ρ0 = 100 / [(Y / 3.987) + (100 - Y) / ρz] ... (2-1) However, ρz is the value calculated by the following formula (2-2): ρz = [124.25(100 - X) + [molecular weight of stabilizer] × X] / [150.5(100 + X)A ２ C]...(2-2) Here, the molecular weight of the stabilizer is Y ２ O ３ For this, 225.81 is used. Also, X and Y are the stabilizer concentration (mol%) and alumina concentration (weight%), respectively. Also, A and C are values ​​calculated by the following formulas (2-3) and (2-4), respectively. A = 0.5080 + 0.06980X / (100 + X) ... (2-3) C = 0.5195 - 0.06180X / (100 + X) ... (2-4) In formula (1), the theoretical sintering density varies depending on the powder composition. For example, the theoretical sintering density of yttria-containing zirconia is 6.117 g / cm³ if the yttria content is 2 mol%. ３ If it's 3 mol%, then it's 6.098 g / cm³. ３ If it's 5.5 mol%, then it's 6.051 g / cm³. ３ (Al ２ O ３ (In the case of 0% by weight). Also, the theoretical sintering density (let's call it ρ1) when other components other than alumina (such as stabilizers and colorants) are included is given by: ρ1 = 100 / [(Z / V) + (100 - Z) / ρ0] ... (2 - 5) where Z is the concentration of other components other than alumina (by weight %), and V is the theoretical density of other components other than alumina (g / cm³). ３ ) The theoretical density of components other than alumina is Yb ２ O ３ 9.17 g / cm³ ３ Er ２ O ３ 8.64 g / cm³ ３ , CEO ２7.22 g / cm³ ３ , Sc ２ O ３ 3.86 g / cm³ ３ , Nd ２ O ３ 7.24 g / cm³ ３ La ２ O ３ 6.51 g / cm³ ３ , Tb ２ O ３ 7.81 g / cm³ ３ CaO content: 3.34 g / cm³ ３ Fe ２ O ３ 5.24 g / cm³ ３ ZnO content: 5.61 g / cm³ ３ MnO ２ 5.03 g / cm³ ３ CoO is 6.10 g / cm³ ３ , Cr ２ O ３ 5.22 g / cm³ ３ , TiO ２ 4.23 g / cm³ ３ CuO is 6.31 g / cm³ ３ , V ２ O ５ 3.36 g / cm³ ３ The sintering density will be measured using the Archimedes method.

[0164] [Relative molding density] Relative molding density (%) = (molding density / theoretical sintering density) × 100 ... (3) Here, theoretical sintering density (ρ ０ (Let's assume this is the value calculated by the above formula (2-1).

[0165] <3. Sintered Body> Next, the pre-sintered body was subjected to final sintering at the pressure, temperature, and time shown in Table 2 to obtain a sintered body. Final sintering was carried out using an apparatus employing the hot isostatic pressing (HIP) method.

[0166] [Relative Sintering Density] The relative sintering density of the sintered body was measured using the same method as for measuring the relative sintering density of the pre-sintered body. The results are shown in Table 2.

[0167]

[0168] [Average Crystal Grain Size] The average crystal grain size was determined using the SEM (Scanning Electron Microscope) image of the sintered body sample obtained by scanning electron microscopy (SEM). The sample for SEM observation was prepared according to JIS R1633. The SEM image was acquired at a magnification such that there were 150 or more crystal particles in one field of view. The average crystal grain size of the zirconia sintered bodies of the examples and comparative examples was determined by the following formula, according to the method described in J. Am. Ceram. Soc., 52[8]443-6 (1969), which measures the grain size from scanning electron microscopy observation of the polished etched surface of the sintered body: D = 1.56L D: Average crystal grain size L: Average length of particles crossing an arbitrary straight line

[0169] [Identification of Crystalline Phase] X-ray diffraction spectra were obtained from zirconia sintered bodies using an X-ray diffractometer ("RINT2500" manufactured by Rigaku). The measurement conditions were as follows: <Measurement Conditions> Measurement device: X-ray diffractometer (Rigaku, RINT2500) Radiation source: CuKα radiation source Sampling interval: 0.02° Scan rate: 2θ = 1.0° / min Divergent slit (DS): 1° Divergent longitudinal limiting slit: 5 mm Scattering slit (SS): 1° Receiving slit (RS): 0.3 mm Monochromatic receiving slit: 0.8 mm Tube voltage: 50 kV Tube current: 300 mA Scanning rate: 2θ = 10 to 80°: 4° / min 2θ = 72 to 76°: 1° / min

[0170] Subsequently, the crystalline phases were identified from the X-ray diffraction spectrum. The phase ratios of each crystalline phase contained in the zirconia sintered body were calculated using the following formulas: Monoclinic phase ratio (%) = (Im(111) + Im(11-1)) / (Im(111) + Im(11-1) + It(101) + Ic(111)) × 100 Tetragonal phase ratio (%) = (100% - Monoclinic phase (%)) × ((It(004) + It(220) / (It(004) + It(220) + Ic(004)) × 100 Cubic phase ratio (%) = (100% - Monoclinic phase (%)) × ((Ic(004) / (It(004) + It(220) + Ic(004)) × 100 Here, Im(111) is the diffraction intensity of (111) in the monoclinic phase, and Im(11-1) is the diffraction intensity of (11-1) in the monoclinic phase. It(101) is the diffraction intensity of (101) in the tetragonal phase, It(220) is the diffraction intensity of (220) in the tetragonal phase, and It(004) is the diffraction intensity of (004) in the tetragonal phase. Ic(004) is the diffraction intensity of (004) in the cubic phase, and Ic(111) is the diffraction intensity of (111) in the cubic phase. The distinction between the monoclinic, tetragonal, and cubic phases of zirconia was performed around 2θ = 26–36° in the XRD spectrum. The distinction between the tetragonal and cubic phases was performed around 2θ = 72–76° in the XRD spectrum. The cubic phase may be distorted depending on the amount of stabilizer added and the manufacturing method, and the peak position may shift, but in this embodiment, the peak between (004) and (220) in the tetragonal phase was treated as the peak of the cubic phase and calculated accordingly.

[0171] [Total Light Transmittance] The total light transmittance of the zirconia sintered bodies of the examples and comparative examples was measured using a spectroscopic haze meter (device name: SH-7000, manufactured by Nippon Denshoku Industries Co., Ltd.) with a D65 light source, in accordance with the method compliant with JIS K7361. The measurement samples were polished on both sides to adjust the thickness to 1 mm. The results are shown in Table 3.

[0172] [Parallel Light Transmittance] The parallel light transmittance of the zirconia sintered bodies of the examples and comparative examples was calculated from the total light transmittance obtained in JIS K7361-1 and the diffuse transmittance Td described in JIS K7136:2000 using the following formula: [Parallel Light Transmittance (%)] = [Total Light Transmittance (%)] - [Diffuse Transmittance Td (%)] Here, [Diffuse Transmittance Td (%)] is calculated as [Total Light Transmittance (%)] × [Haze (%)] × 100 －１ The value is calculated as follows. [Haze (%)] was measured in accordance with JIS K7136:2000. The sample was polished on both sides to adjust the thickness to 1 mm. The results are shown in Table 3.

[0173] [Monoclinic phase ratio after hydrothermal treatment at 134°C, 0.3 MPa, 75 hours] First, the zirconia sintered bodies of the examples and comparative examples were subjected to hydrothermal treatment at 134°C, an absolute pressure of 0.3 MPa (under an underwater atmosphere) for 75 hours. Then, the monoclinic phase ratio contained in the crystalline phase of the zirconia sintered bodies after hydrothermal treatment was determined. The method for determining the monoclinic phase ratio of the zirconia sintered bodies after hydrothermal treatment was the same as described in the [Identification of Crystalline Phases] section. The results are shown in Table 3.

[0174] [Three-point bending strength] The three-point bending strength of the zirconia sintered bodies of the examples and comparative examples obtained above was measured in accordance with the three-point bending strength of JIS R 1601. The results are shown in Table 3.

[0175] [Toughness] Toughness was measured using the IF method with a load of 5.0 kgf (49.0 N), in accordance with JIS R1607 (Test method for room temperature fracture toughness of fine ceramics). Using a Vickers hardness tester, seven indentations with a square shape were selected, and their toughness was determined. The average of the toughness of the remaining five indentations (excluding the one with the smallest and largest values) was used as the toughness value. However, indentations that did not show crack extension were considered invalid, and indentations with four cracks extending from the tip of the square were adopted. Each toughness value was calculated using the following formula: Kc = 0.018 × Hv × a ０．５ ×[(c-a) / a] －０．５ × (Hv / E) －０．４Kc, Hv, a, c, and E have the following meanings. The indentation lengths and crack lengths on the X and Y axes used to determine a and c are as shown in Figure 2. Kc: Toughness value [MPa・m] ０．５ ] Hv: Vickers hardness [GPa] a: Half of the average indentation length on the X and Y axes [μm] c: Half of the average crack length on the X and Y axes [μm] E: Young's modulus [GPa] The Vickers hardness was determined in accordance with JIS R 1610 (Test method for hardness of fine ceramics). The Vickers hardness was calculated using the following formula: Hv = 0.001854 × [F / d ２ Sv] F and d mean the following. The X-axis indentation length and Y-axis indentation length used to determine d are as shown in Figure 2. Hv: Vickers hardness [GPa] F: Test force [N] d: Average value of X-axis indentation length and Y-axis indentation length [mm] The Young's modulus used was 210 GPa, which is a commonly known value for yttria-stabilized zirconia.

[0176]

Claims

1. Stabilized zirconia comprising zirconia and a stabilizer, wherein the stabilizer is Y ２ O ３ The Y in the stabilized zirconia includes ２ O ３ A zirconia sintered body characterized by having a content of over 4.0 mol% and up to 6.5 mol% in terms of oxide, an average crystal grain size of 100 nm to 200 nm, a monoclinic phase ratio of 0.5% or less, a tetragonal phase ratio of 20.0% to 96.0%, a cubic phase ratio of 4.0% to 80.0%, and a relative sintering density of 99.6% or more.

2. The Y in the stabilized zirconia ２ O ３ The zirconia sintered body according to claim 1, characterized in that the content of exceeds 5.2 mol% in terms of oxide.

3. The zirconia sintered body according to claim 1, characterized in that the tetragonal phase ratio is 20.0% or more and 60.0% or less, and the cubic phase ratio is 40.0% or more and 80.0% or less.

4. The Y in the stabilized zirconia ２ O ３ The zirconia sintered body according to claim 1, characterized in that the content of exceeds 5.2 mol% in terms of oxide, the tetragonal phase ratio is 20.0% or more and 60.0% or less, and the cubic phase ratio is 40.0% or more and 80.0% or less.

5. The zirconia sintered body as claimed in any one of claims 1 to 4, characterized in that it contains Al ２ O ３ in a range of 0.15% by mass or less with respect to the entire zirconia sintered body.

6. A zirconia sintered body according to any one of claims 1 to 4, characterized in that the total light transmittance at a thickness of 1 mm is 45% or more and 60% or less.

7. A zirconia sintered body according to any one of claims 1 to 4, characterized in that the parallel light transmittance at a thickness of 1 mm is 7.0% or more and 30.0% or less.

8. A zirconia sintered body according to any one of claims 1 to 4, characterized in that its three-point bending strength is 500 MPa or more and 1000 MPa or less.

9. The toughness value obtained by the IF method is 2.7 MPa·m ０．５ 5.0MPa・m or more ０．５ The zirconia sintered body according to any one of 1 to 4, characterized in that it is as follows:

10. Zirconia powder at 1.0 t / cm ２ The above is 2.5 t / cm ２ A method for producing a zirconia sintered body according to any one of 1 to 4, comprising: step A, molding at the following pressure to obtain a molded body; step B, pre-sintering the molded body under normal pressure, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a pre-sintered body; and step C, final sintering the pre-sintered body under a pressure of 50 MPa or higher and 200 MPa or lower, at a temperature of 1150°C or higher and 1250°C or lower, for 1 hour or more and 5 hours or less, to obtain a sintered body.

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