JP4196608B2 - Method for producing colored zirconia composite ceramic sintered body - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a colored zirconia composite ceramic sintered material suitably used for, for example, industrial machine parts, office / physical and chemical supplies, biomaterials, medical tools, etc.the body'sIt relates to a manufacturing method.
[0002]
[Prior art]
Conventionally 2-3 mol% yttria (Y₂O₃) Tetragonal zirconia polycrystal (Y-TZP) as a stabilizer is superior in mechanical properties such as high strength and high toughness compared to general-purpose materials such as alumina, silicon nitride and silicon carbide. Therefore, they are widely used in practical applications from optical connector ferrules, grinding media, various blades, sports and leisure goods, and the like.
[0003]
Also, in recent years, when joint function of limbs is lost due to illness, disaster, etc., to reconstruct a sliding member or a tooth lost due to aging, illness, etc. on an artificial joint used to restore these Applications to biomaterials such as artificial tooth roots, attachments, and crowns used in the field of medicine are gradually advancing.
[0004]
However, conventional yttria-based tetragonal zirconia (Y-TZP) is a phase transition from a metastable tetragonal crystal to a monoclinic crystal at a relatively low temperature range (200 to 300 ° C.). It has been pointed out that the volume expansion of about 4.6% sometimes causes internal cracks and causes a significant strength deterioration (hereinafter referred to as "low temperature deterioration"). . In addition, it is a well-known fact that the phase transition is further accelerated in a humid environment containing moisture.
[0005]
In Y-TZP, trivalent Y ions are dissolved in an interstitial form at the 8-coordinate position of tetravalent Zr ions, so oxygen defects occur on the zirconia side due to the difference in valence, which deteriorates at low temperatures. It is interpreted that it is an essential cause.
[0006]
In recent years, attempts have been made to suppress low-temperature degradation by controlling the crystal grain size of the sintered body to about 0.5 μm or less, but when Y-TZP is exposed to a humid environment of 200 to 300 ° C. However, there is a risk that phase transitions will occur easily, or that phase transitions will gradually occur in a living body that is always in a moist environment even when the ambient temperature is as low as about 37 ° C. The situation has to be handled carefully.
[0007]
In contrast, Ceria (CeO₂Unlike Y-TZP, tetragonal zirconia polycrystal (Ce-TZP) containing) as a stabilizer is a ceria (CeO) which is a stabilizer.₂) Is dissolved in zirconia as tetravalent Ce ions, and no oxygen defects occur, so that it is supported by many experimental data that it is a material that does not cause crystallographic degradation at low temperatures. In addition, it is also known that ceramics have an unprecedented high toughness value.
[0008]
However, Ce-TZP has a remarkably low strength and hardness compared to Y-TZP, so that it has been practically not used at all.
[0009]
On the other hand, in a field where palatability is also required for accessories such as accessories, cutlery, sports and leisure goods, etc., zirconia crystals colored in red, blue, yellow or black have been required. I came. Furthermore, in the field applied to living bodies such as artificial teeth and crowns, there is a strong demand for colored zirconia having color variations having the same texture as natural teeth and excellent in aesthetics.
[0010]
In response to such demands, various colored zirconia having a desired color tone have been developed by adding and sintering a rare earth metal or an oxide such as a transition metal to zirconia. For example, JP-A-6-199098 discloses orange (CeO) as the color tone of zirconia and the types of various colorants in a system in which 0.05% by weight of a colorant is contained in zirconia containing 3 mol% of yttria.₂) To olive color (Cr₂O₃), Lilac (Co₂O₃, Nd₂O₃), Yellow (CuO, Fe₂O₃, NiO, TiO₂), Pink (Er₂O₃, Eu₂O₃, Ho₂O₃), Brown (MnO₂), Amber color (Pr₂O₃), Green (Tm₂O₃, V₂O₃) Until now. JP-A-8-310860 discloses a black zirconia sintered body, and JP-A-8-33650 discloses a zirconia orthodontic bracket as a field requiring aesthetics.
[0011]
However, any of these colored zirconia is a tetragonal zirconia polycrystal (Y-TZP) mainly containing yttria as a stabilizer, or a composite crystal based on it. The fact was that some limitations were put on practical use due to various problems involved.
[0012]
[Problems to be solved by the invention]
  The present invention has been made in view of the above points, and has excellent mechanical properties and excellent colored zirconia composite ceramic sintering that does not exhibit low-temperature deterioration.the body'sThe object is to provide a manufacturing method.
[0018]
[Means for Solving the Problems]
  ContractClaim1The method for producing a colored zirconia composite ceramic sintered body according toA zirconia-based composite ceramic sintered body in which a first phase mainly composed of tetragonal zirconia and a second phase composed of alumina particles containing at least ceria as a stabilizer is dispersed, and as a coloring component element, a period Containing at least one element selected from elements belonging to Groups 6 and 8-10 in the second phaseA method for producing a colored zirconia-based ceramic sintered body, which comprises a first raw material component composed of tetragonal zirconia containing at least ceria as a stabilizer, and belongs to groups 6 and 8 to 10 in the periodic table in alumina powder. A second raw material component containing at least one element selected from the elements is mixed, formed into a desired shape, and then fired in an oxygen-containing atmosphere.Is. In this production method, a pre-prepared powder prepared by mixing alumina powder with at least one coloring component element selected from Cr, Fe, and Co or a compound thereof, and coloring the pre-prepared powder as a whole The amount of component element or its compound in terms of oxide is Cr ₂ O _Three 0.01 to 20 mol%, Fe ₂ O _Three Mixing was performed so that at least one of 0.01 to 20 mol% and CoO 0.01 to 15 mol% was satisfied and the total amount of these oxides in terms of oxide was 0.01 to 20 mol%. A pre-prepared powder is prepared, and the pre-mixed powder is heat-treated in an oxygen-containing atmosphere at a temperature range of 500 to 1000 ° C. and used as the second raw material component.
[0020]
  And claims2The invention of claim1In Cr₂O_Three, Fe₂O_ThreeThe pre-prepared powder is prepared by mixing at least one metal oxide powder selected from CoO and alumina powder.
[0021]
  And claims3The invention of claim1In at least one oxide precursor selected from a metal salt containing trivalent Cr, trivalent Fe, or divalent Co, an organometallic complex, or a metal alkoxide is dissolved in an organic solvent and mixed with alumina powder. Then, a pre-prepared powder is prepared by removing the solvent.
[0022]
  And claims4The invention of claim1Thru3In any of the above, ceria-based tetragonal zirconia powder containing 8 to 12 mol% of ceria is used as the first raw material component, and the specific surface area of the first raw material component is 5 to 20 m.²g^-1And the average particle diameter of the second raw material component is 0.1 to 0.3 μm.
[0023]
  And claims5The invention of claim1Thru4In any one of the above, after firing the mixture of the first raw material component and the second raw material component, the temperature is equal to or lower than the firing temperature and 1000 ° C or higher in an oxygen-containing atmosphere. An annealing process is performed.
[0024]
  And claims6The invention of claim5In the above, as the annealing process, hot isostatic pressing is performed in an oxygen-containing atmosphere.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0026]
First, each phase constituting the colored zirconia composite ceramic sintered body of the present invention and the structure of the composite ceramic sintered body will be described, and then the coloring component and the added form will be described.
[0027]
The colored zirconia composite ceramic sintered body of the present invention is constituted by dispersing first phase crystal particles mainly composed of tetragonal zirconia and second phase crystal particles mainly composed of alumina.
[0028]
The first phase crystal particles made of tetragonal zirconia must contain at least ceria as a stabilizer. As described above, ceria acts as a stabilizer for tetragonal zirconia, and is extremely important for crystallographically suppressing low temperature degradation of zirconia. The ratio of tetragonal crystals in the first phase is preferably 90% by volume or more with respect to the entire first phase.
[0029]
Although the content of ceria in the first phase is not particularly limited, for example, it is preferably 8 to 12 mol%, more preferably 10 to 12 mol%, based on the total amount of the first phase. If this content is too small, tetragonal crystallization, which is a metastable phase, is insufficient and monoclinic crystals are predominantly increased, and there is a risk of cracking after sintering, or microcracks are inherent, There is a risk of strength degradation. On the other hand, when the content is excessive, cubic crystals which are high-temperature stable phases begin to appear, and the amount of tetragonal crystals becomes less than 90% by volume, which may result in insufficient strength and toughness.
[0030]
In addition to the zirconia and ceria as a stabilizer, the first phase may contain other stabilizers such as magnesia, calcia, or yttria, and further contains other trace amounts of impurities. It may be. When other impurities are contained, the content is desirably 0.5 mol% or less with respect to the total amount of the first phase.
[0031]
The second phase crystal particles made of alumina contain a coloring component element.
[0032]
As the coloring component element, it is preferable to use only at least one element selected from elements belonging to Group 6 (former Group 6a) and Group 8 to Group 10 (former Group 8) in the periodic table. Moreover, as an addition form, it is preferable to make it contain mainly in the form dissolved in the alumina particle which comprises a 2nd phase, and not to make it dissolve in a 1st phase.
[0033]
  Here, as a conventional general zirconia coloring method, a method of sintering by adding an inorganic colorant, or a method of sintering by adding an oxide such as a rare earth metal or a transition metal to zirconia It has been known. At this time, in order to obtain a desired color tone, the addition of an inorganic colorant usually requires addition of several tens of weight% or more, and the excellent mechanical performance (high strength, high toughness) of zirconia is impaired. There are many. On the other hand, rare earth ions with vacancies in f orbit, or vacancies in d orbit and energyAssociateAddition of transition metal ions whose position is split by the influence of the ligand field can develop zirconia in a trace amount compared to the addition of inorganic pigments, but by dissolving various metal ions in zirconia, Since the light absorption region is controlled to emit light, the solid solution of the metal ion in zirconia becomes a factor that inhibits the stabilization of tetragonal crystals, and there is concern that the mechanical properties may be adversely affected.
[0034]
On the other hand, in the present invention, as the coloring component, one which is preferentially dissolved in alumina mainly constituting the second phase and preferably not substantially dissolved in zirconia constituting the first phase is used. Accordingly, it is possible to add various kinds of colors while maintaining the excellent mechanical properties (high strength and high toughness) of zirconia. Here, it is conceivable that a very small amount of the coloring component element is unavoidably dissolved in the first phase. Even in this case, the amount of the coloring component element in the first phase is 0 in terms of oxide. It is preferable to be less than 0.01 mole.
[0035]
From the above viewpoint, it is preferable to use Cr as an element belonging to Group 6 of the periodic table and Fe and Co as elements belonging to Group 8 to 10 as the coloring component. Moreover, the addition amount of these elements is Cr equivalent to the total amount of the second phase in terms of oxide of the coloring component element.₂O₃0.01 to 20 mol%, Fe₂O₃Is preferably 0.01 to 20 mol%, or CoO is preferably 0.01 to 15 mol%, and at least one of them is preferably blended. % Range is preferable. A more preferable addition amount of each coloring component element is 0.05 to 8 mol%, and a more preferable addition amount is 0.05 to 1 mol%. Moreover, the more preferable range of the total addition amount of a coloring component element is 0.05-8 mol%, and a still more preferable range is 0.05-1 mol%. If the addition amount of the coloring component element is too small, it is difficult to obtain a sufficient coloring effect, and if this addition amount is excessive, it becomes difficult to make the coloring component element dissolve in the alumina.
[0036]
Further, in the colored zirconia composite ceramic sintered body according to the present invention, among the second phase made of alumina, those made of extremely fine crystal particles of several tens of nanometers are contained in the crystal particles constituting the first phase. It is preferable to form a so-called “nanocomposite structure” which is dispersed, whereby the strength and hardness of the zirconia composite ceramic sintered body are dramatically improved.
[0037]
More specifically, the second phase fine crystal particles made of alumina incorporated in the first phase crystal particles made of tetragonal zirconia are localized in the first phase crystal particles due to a difference in thermal expansion. A critical residual stress field, resulting in an increase in the critical stress of the stress-induced phase transition from tetragonal to monoclinic, and a subgrain bindery in which the transition and transition piled up in the first phase grains By forming and virtually subdividing the first phase crystal particles, it effectively contributes to high strength. As a result, the low strength and low hardness, which are disadvantages of ceria-based zirconia (Ce-TZP), have been improved to a level comparable to yttria-based zirconia (Y-TZP), and a high toughness that is three times or more that of Y-TZP. It is possible to realize tough zirconia ceramics that have both.
[0038]
The number of the second phase particles dispersed and present in the particles constituting the first phase is preferably 2 with respect to the total number of the second phase crystal particles in the colored zirconia composite ceramic sintered body. %, And the larger the ratio, the better.
[0039]
Here, titania having an effect of promoting grain growth of the zirconia particles may be dissolved in the first phase and contained. In this case, in the sintering process, more second phase particles can be dispersed in the first phase to promote the formation of the nanocomposite structure. At this time, the content of titania in the first phase is not particularly limited. For example, the content of titania is preferably 0.02 to 4 mol%, more preferably, based on the total amount of the first phase. Is 0.05 to 1 mol%. If the content of titania is too small, the effect of improving the grain growth of the first phase due to titania cannot be obtained, and if it is excessive, the strength of the first phase may become coarse, resulting in a significant decrease in strength. It is not preferable.
[0040]
Further, the content of the second phase in the colored zirconia composite ceramic sintered body is not particularly limited, but is preferably 0.5 to 50% by volume, for example, based on the total amount of the sintered body. Preferably it is 30-40 volumes. If the content of the second phase is less than 0.5% by volume, the effect of improving the strength and toughness is hardly obtained, and if it exceeds 40% by volume, the particles of the second phase are sintered together. Since the second phase particles incorporated into the first phase particles are reduced, the strength and toughness are gradually lowered. Further, when the volume exceeds 50% by volume, the second phase is matrixed. May decrease.
[0041]
Next, a method for producing a colored zirconia composite ceramic sintered body according to the present invention will be described.
[0042]
The colored zirconia composite ceramic sintered body can be formed from a first raw material component made of tetragonal zirconia containing at least ceria as a stabilizer and a second raw material component made of alumina.
[0043]
As the first raw material component, it is preferable to use ceria-based tetragonal zirconia powder (Ce-TZP) containing 8 to 12 mol% of ceria and the balance being zirconia. In addition, other stabilizers such as magnesia, calcia, or yttria can be dissolved in the ceria-based tetragonal zirconia powder. Other trace amounts of impurities may be contained, but the content is preferably 0.05 mol% or less in terms of oxide. Further, when titania is contained in the first phase in order to promote the formation of the nanocomposite structure of the sintered body, the one containing titania as the first raw material component is used. In one raw material component, it is preferable to contain titania in a range of 0.02 to 4 mol% with respect to the total amount of the first phase.
[0044]
As the second raw material component, alumina powder and a coloring component raw material are used.
[0045]
Examples of the coloring component material include at least one coloring component element selected from elements belonging to Group 6 (former group 6a) and Group 8 to 10 (former group 8) of the periodic table, or a compound thereof. In particular, at least one element selected from Cr, Fe and Co or a compound thereof is preferable. As the coloring component raw material, one in the state of an oxide of the coloring component element can be used, for example, Cr₂O₃, Fe₂O₃At least one oxide powder selected from CoO can be used. Alternatively, at least one oxide precursor selected from a metal salt containing trivalent Cr, trivalent Fe, or divalent Co, an organometallic complex, or a metal alkoxide can also be used.
[0046]
The first raw material component and the second raw material component as described above are mixed to prepare a mixed raw material. At this time, as the second raw material component, the alumina powder and the coloring component raw material can be blended separately in the mixed raw material.
[0047]
More preferably, as the second raw material component, an alumina powder containing a coloring component element is used. In this case, when obtaining a sintered body by firing, the coloring component element with respect to alumina is used. The preferential solid solution can be promoted, and good color development can be prevented from being inhibited by the coloring component raw material remaining around the first phase made of zirconia.
[0048]
  MaTheAs the second raw material component, one obtained by firing a pre-prepared powder obtained by mixing a coloring component raw material containing a coloring component element with alumina powder is used. In this case, before forming the sintered body by firing, the coloring component elements can be preferentially dissolved in alumina in advance, and the remaining of the coloring component raw material in the sintered body can be further effectively prevented. Can do.
[0049]
  At the time of preparing the pre-prepared powder, the coloring component raw materials as described above are dispersed or dissolved in an organic solvent, and then mixed with the alumina powder, and the organic solvent is removed therefrom, whereby the pre-prepared powder can be obtained. The pre-prepared powder is fired in a temperature range of 500 to 1000 ° C. in an oxygen-containing atmosphere such as the air.TheBy applying this treatment, the ions of the coloring component elements can be preferentially dissolved in alumina.
[0050]
  In the second raw material component thus obtained, a coloring component element is contained in the same composition as the second phase composition in the desired colored zirconia composite ceramic sintered body. When at least one of Cr, Fe, and Co is contained as a coloring component element, when these coloring component elements are converted into oxides, the total amount of the second raw material component in the second raw material component Against Cr₂O_Three0.01 to 20 mol%, Fe₂O_ThreeIs blended so that at least 0.01 to 20 mol% or CoO is 0.01 to 15 mol%.TheAt this time, the total addition amount of the color component elements should be in the range of 0.01 to 20 mol%.TheA more preferable addition amount of each coloring component element is 0.05 to 8 mol%, and a more preferable addition amount is 0.05 to 1 mol%. Moreover, the more preferable range of the total addition amount of a coloring component element is 0.05-8 mol%, and a still more preferable range is 0.05-1 mol%. If the addition amount of the coloring component element is too small, it is difficult to obtain a sufficient coloring effect, and if this addition amount is excessive, it becomes difficult to make the coloring component element dissolve in the alumina.
[0051]
Moreover, the specific surface area which contains 8-12 mol% ceria as a 1st raw material component and a remainder consists of zirconia is 5-20m.²g^-1It is preferable to use those having an average particle size of 0.1 to 0.3 μm as the second raw material component. When such a combination of raw material components is used, the second phase formed from the second raw material component is easily taken into the first phase formed from the first raw material component in the sintering process, and more Many second phase crystal particles can be dispersed within the first phase to facilitate the formation of a nanocomposite structure.
[0052]
The first raw material component and the second raw material component are mixed at a blending ratio that matches the ratio of the first phase and the second phase in the desired colored zirconia composite ceramic sintered body, preferably It mix | blends so that the ratio of a 2nd raw material component may be 0.5-50 volume% with respect to the total amount of a 1st raw material component and a 2nd raw material component, More preferably, it is 30-40 volume%.
[0053]
Next, the mixed powder of the first raw material component and the second raw material component thus obtained is formed into a desired shape by pressure molding or the like, and then fired. The firing conditions are not particularly limited, but firing is preferably performed in a temperature range of 1400 to 1550 ° C. for 3 to 5 hours in an oxygen-containing atmosphere such as the air. If the firing temperature at this time is less than 1400 ° C., it will be difficult to obtain a dense sintered body, it will be difficult to impart sufficient strength to the sintered body, and if the firing temperature exceeds 1550 ° C. There is a possibility that the crystal grains of the first phase and the second phase grow excessively and cause a decrease in strength. At this time, the firing is performed so that the percentage of the actual density of the sintered body relative to the theoretical density derived based on the relative density, that is, the composition ratio of each component constituting the sintered body, is 99% or more. It becomes possible to form a ligature.
[0054]
In addition, it is preferable that the sintered body thus obtained is further subjected to a treatment for imparting translucency (translucency). In this case, the obtained colored zirconia composite ceramic sintered body is obtained. It is suitable for application to crowns and the like that require various color variations and aesthetics.
[0055]
Here, generally, alumina and zirconia do not have an absorption edge in a specific wavelength region, and thus basically show translucency. Further, these ceramics can be imparted with transparency by improving the consistency of the polycrystalline grain boundaries to suppress light scattering, or by forming a single crystal without the light scattering source. A typical example is cubic zirconia as the former and sapphire as the latter. On the other hand, the colored zirconia composite ceramic sintered body according to the present invention is a principle that controls the light absorption region by causing various metal ions to be dissolved, and develops color. Will act negatively. Therefore, in order to impart translucency, it is an important factor to enhance the consistency of the grain boundary of the composite sintered body and suppress light scattering at the grain boundary.
[0056]
The treatment for imparting translucent in the present invention is not particularly limited, and there is a method for enhancing the consistency of grain boundaries in the sintered body by performing an annealing treatment. In addition, as an annealing treatment of the sintered body, it is particularly effective to perform hot isostatic pressing (HIP) in an oxygen-containing atmosphere. When performing hot isostatic pressing (HIP), the atmosphere during the treatment is not particularly limited, but a mixed gas of an inert gas such as argon and oxygen gas can be used. The oxygen gas concentration with respect to the total amount of the mixed gas is preferably 5% by volume.
[0057]
【Example】
Hereinafter, the present invention will be described in detail by way of examples.
[0058]
<Reference Examples 1-3>
Alumina powder having an average particle size of 0.2 μm (hereinafter simply referred to as “Al₂O₃As a coloring component for Cr (NO)₃)₃・ 9H₂O, Fe (NO₃)₃・ 9H₂O or Co (NO₃)₂・ 6H₂Each nitrate of O was blended and wet ball mill mixed in an ethanol solvent for 24 hours. At this time, each nitrate is Al₂O₃And oxide equivalent to the total amount of coloring components (Cr₂O₃, Fe₂O₃, CoO) was added so that the molar fraction in Table 1 would be the ratio shown in Table 1.
[0059]
Next, the dried powder is uniaxially pressed under a condition of 20 MPa using a φ20 mm mold, and further CIP (cold isostatic pressing) under a condition of 145 MPa to obtain a tablet-like molded body. It was.
[0060]
Subsequently, each compact was fired in the atmosphere at 1440 ° C. for 4 hours to obtain a sintered body.
[0061]
  <Reference Examples 4-6>
  Specific surface area of 15 m containing 10 mol% of CeO as a stabilizer²g^-1Tetragonal zirconia powder (hereinafter referred to as “Ce-TZP”), Al₂O_ThreeAnd Cr (NO_Three)_Three・ 9H₂O, Fe (NO_Three)_Three・ 9H₂O or Co (NO_Three)₂・ 6H₂Each nitrate of O was blended and wet ball mill mixed in an ethanol solvent for 24 hours. At this time, each nitrate is Al₂O_ThreeAnd oxide equivalent to the total amount of coloring components (Cr₂O_Three, Fe₂O_Three, CoO) so that the molar fraction is as shown in Table 1, and Al₂O_ThreeThe blending amount of the coloring component is Al based on the total amount of the sintered body obtained₂O_ThreeThe volume fraction of the solid solution with the coloring component was set to 30% by volume.
[0062]
Next, the dried powder was molded and fired in the same manner as in Reference Examples 1 to 3, to obtain a sintered body.
[0063]
<Comparative Examples 1-3>
In Ce-TZP, Cr (NO₃)₃・ 9H₂O, Fe (NO₃)₃・ 9H₂O or Co (NO₃)₂・ 6H₂Each nitrate of O was blended and wet ball mill mixed in an ethanol solvent for 24 hours. At this time, each nitrate is converted to oxide (Cr) with respect to the total amount of Ce-TZP and coloring components.₂O₃, Fe₂O₃, CoO) so that the molar fraction in Table 1 is as shown in Table 1.
[0064]
Next, the dried powder was molded and fired in the same manner as in Reference Examples 1 to 3, to obtain a sintered body.
[0065]
  <Evaluation>
  Each obtained in this wayreferenceThe sintered bodies of the examples and the comparative examples are dense ones in which the relative density is 99% or more with respect to the theoretical density derived from the composition ratio of the constituent components in the sintered body.Reference Examples 4-6In the first to third crystal grains composed of zirconia and Comparative Examples 1 to 3, the first phase crystal grains composed of zirconia in the sintered body are homologous to tetragonal-monoclinic-cubic crystals by X-ray diffraction. As a result, the monoclinic crystal was 5 vol% or less, and the tetragonal crystal was the main phase.
[0066]
  Also eachreferenceAbout the example and the comparative example, the external appearance was visually inspected and the color tone was evaluated. The results are summarized in Table 1. According to this result, Al₂O_ThreeReference Examples 1 to 3 in which coloring components were added to Ce, TZP, and Al₂O_ThreeAnd coloring ingredientsReference Examples 4-6In this case, a sintered body was obtained which was generally colored pink when chromium was added, generally yellow when iron was added, and generally blue when cobalt was added. However,Reference Examples 4-6The color tone of the sintered body exhibited a darker color as compared with Reference Examples 1 to 3.
[0067]
On the other hand, in Comparative Examples 1 to 3 in which a coloring component was added to Ce-TZP, the sintered bodies exhibited a grayish black color, and showed significantly different aspects from the sintered bodies of Reference Examples 1 to 3.
[0068]
  Also, eachreferenceIn the sintered bodies of Examples and Comparative Examples, the presence or absence of solid solution of the coloring component elements was evaluated based on the lattice constant derived by X-ray diffraction measurement. According to this, reference examples 1 to6Then, the lattice constant derived from the diffraction peak based on the measured crystal of alumina was higher than that of pure alumina. Where Cr³⁺The ion radius of the ions is 0.82Å, Fe³⁺The ion radius of the ions is 0.67Å, Co²⁺The ion radius of the ions is 0.82Å, both of which are Al³⁺Therefore, the increase in the lattice constant of alumina is considered to be due to the solid solution of these coloring component elements in alumina. On the contrary,Reference Examples 4-6In Comparative Examples 1 to 3, the lattice constant derived from the diffraction peak based on the zirconia crystal does not change compared to the lattice constant of Ce-TZP used as the raw material, and the solid solution of the color component element is I was not able to admit.
[0069]
Therefore, the sintered bodies of Comparative Examples 1 to 3 all showed grayish black color because the color of each nitrate powder added as a coloring component was reflected, and coloration due to the solid solution of various metal ions occurred at all. It became clear that it was not.
[0070]
  AlsoReference Examples 4-6The sintered body of No. 1 became darker than Reference Examples 1 to 3 because the metal ions present around the Ce-TZP particles were not dissolved in Ce-TZP during sintering. It is thought that it remained in the state of nitrate and the color of this nitrate was reflected.
[0071]
Based on the above results, the coloring components Cr, Fe, and Co are preferentially dissolved only in alumina and not in zirconia. Confirmed by derivation.
[0072]
[Table 1]
[0073]
<Examples 4 to 16>
Al₂O₃On the other hand, Cr (NO₃)₃・ 9H₂O, Fe (NO₃)₃・ 9H₂O and Co (NO₃)₂・ 6H₂Two or three of each nitrate of O₂O₃And oxide equivalent to the total amount of coloring components (Cr₂O₃, Fe₂O₃, CoO) was added so that the molar fraction in Table 2 would be the ratio shown in Table 2, followed by wet ball mill mixing in an ethanol solvent for 24 hours, followed by drying to prepare a pre-formulated powder.
[0074]
The pre-prepared powder was fired at 800 ° C. for 1 hour in the air to obtain a second raw material component.
[0075]
As a first raw material component, a specific surface area of 15 m²g^-1Of Ce-TZP was used.
[0076]
Then, these two kinds of powders are blended so that the volume fraction of the second raw material component relative to the total of the first raw material component and the second raw material component is 30% by volume, and wet ball mill mixing is performed in an ethanol solvent for 24 hours. did.
[0077]
Next, the dried powder is uniaxially pressed under a condition of 20 MPa using a φ20 mm mold, and further subjected to CIP (cold isostatic pressing) under a condition of 147 MPa to obtain a tablet-like molded body. It was.
[0078]
Subsequently, each compact was fired in the atmosphere at 1440 ° C. for 4 hours to obtain a sintered body.
[0079]
<Evaluation>
The sintered bodies of the examples obtained in this way are all dense with a relative density of 99% or more, and the first-phase crystal particles made of zirconia in the sintered body are X As a result of phase identification of tetragonal crystal-monoclinic crystal-cubic crystal by line diffraction, monoclinic crystal was 1% by volume or less, and almost tetragonal crystal was the main phase.
[0080]
Moreover, about each Example, the external appearance was visually inspected and the color tone was evaluated. The results are summarized in Table 2. According to this result, as in Examples 4 to 12, when Cr, Fe, and Co ions, which are coloring components, are dissolved in a binary system in alumina, a color tone that interpolates each single color is obtained. Became clear. Further, at this time, a darkish color as in Examples 1 to 3 was not observed, and it was extremely clear. This is because the second raw material component in which the coloring component is dissolved in the alumina powder in advance is prepared, so that the solid solution of the coloring component element in the alumina is promoted and is not dissolved in the sintered body. This is probably because the coloring component did not remain. Further, as in Examples 13 to 16, it was confirmed that it is possible to obtain a grayish black color tone by increasing the absorption edge of the light by dissolving the coloring component in a ternary system. .
[0081]
Moreover, the presence or absence of the solid solution of the color component element in the sintered body of each example was evaluated based on the lattice constant derived by X-ray diffraction measurement in the same manner as in Examples 1 to 3 and the like. According to this, the solid solution of the color component element in alumina was confirmed, and the solid solution of the color component element in zirconia was not recognized.
[0082]
From the above results, it was confirmed that the coloring components Cr, Fe, and Co were preferentially dissolved in only alumina and not in zirconia. In addition, since the second raw material component in which the coloring component is solid-dissolved in the alumina powder is prepared in advance, the solid-solution of the coloring component element into the alumina is promoted and the remaining of the coloring component in the sintered body is suppressed. It was confirmed that
[0083]
[Table 2]
[0084]
<Examples 17 to 19>
Al₂O₃On the other hand, Cr (NO₃)₃・ 9H₂O, Fe (NO₃)₃・ 9H₂One kind of each nitrate of O is Al₂O₃In terms of oxide (Cr)₂O₃, Fe₂O₃) Were added so that the molar fraction in Table 3 would be the ratio shown in Table 3, mixed in an ethanol solvent for 24 hours by wet ball milling, and then dried to prepare a pre-prepared powder.
[0085]
The pre-prepared powder was fired at 800 ° C. for 1 hour in the air to obtain a second raw material component.
[0086]
As a first raw material component, a specific surface area of 15 m²g^-1Of Ce-TZP was used.
[0087]
Then, these two kinds of powders are blended so that the volume fraction of the second raw material component is 30% by volume with respect to the total of the first raw material component and the second raw material component, and wet ball mill mixing is performed in an ethanol solvent for 24 hours. did.
[0088]
Next, the dried powder is uniaxially pressed under a condition of 7 MPa using a φ68 mm mold, and further CIP (cold isostatic pressing) under a condition of 147 MPa to obtain a tablet-like molded body. It was.
[0089]
Subsequently, each compact was fired in the atmosphere at 1440 ° C. for 4 hours to obtain a sintered body.
[0090]
<Comparative example 4>
Except not mix | blending a coloring component, it carried out similarly to Examples 17-19, and obtained the sintered compact.
[0091]
<Evaluation>
Each sintered body thus obtained was dense with a relative density of 99% or more.
[0092]
Moreover, about each Example and the comparative example, the external appearance was visually inspected and the color tone was evaluated. The results are summarized in Table 3.
[0093]
For each of the examples and comparative examples, 5 prismatic specimens of 3 mm × 4 mm × 40 mm were cut out from a molded sintered body having a diameter of 50 mm and a thickness of 5 mm with a diamond blade, and a sample for evaluating mechanical properties and did. The ridge line of the sample was chamfered with C of 0.1 mm, and the side surface was polished with a 600-800 diamond grindstone. In the test of bending strength, the tensile surface of the sample was mirror finished with the final diamond paste.
[0094]
Using such a sample, a three-point bending test was performed under the conditions of a lower span of 30 mm and a crosshead speed of 0.5 mm / min to obtain a bending strength.
[0095]
Further, a Vickers indenter was imprinted on the sample mirror surface under the conditions of a load of 490 N (50 kgf) and a holding time of 15 seconds, and the fracture toughness value was measured by the IF method.
[0096]
The fracture toughness value was calculated using the following Niihara equation corresponding to the palmqvist type crack shown below by measuring the length of the crack and the size of the indentation caused by the indentation of the Vickers indenter.
[0097]
K_IC= 0.018H_v・ A^1/2・ (L / a)^1/2・ (H_v/ E)^-2/5
K_IC: Fracture toughness value
H_v: Vickers hardness
a: 1/2 length of diagonal line of Vickers indentation
l: l = c−a
c: Length of crack extending from Vickers indentation
E: Young's modulus (elastic modulus)
These results are also summarized in Table 3. According to this result, Examples 17 to 19 have the same mechanical characteristics as Comparative Example 4 in which no coloring component was used, and it was confirmed that the mechanical strength was not deteriorated even if the coloring component was used. . As a result, the coloring component is not dissolved in the first phase composed of tetragonal zirconia, but is preferentially dissolved in the second phase composed of alumina, thereby maintaining various mechanical properties while maintaining the mechanical properties. It was confirmed that can be added.
[0098]
In addition, as a result of observing the microstructure of these sintered bodies with a scanning electron microscope and a transmission electron microscope, in any of the sintered bodies, tens to hundreds of nanometers of the second phase crystal particles. It was confirmed that some of the very fine second-phase crystal particles have a so-called “nanocomposite structure” dispersed in the first-phase crystal particles.
[0099]
Moreover, in the case of Examples 17-19 and the case of Comparative Example 4, the same nanocomposite structure | tissue is formed, and even when a coloring component is used, the bad influence with respect to a fine structure is not recognized, A coloring component is used. It was confirmed that the same nanocomposite structure was maintained as in the case of no.
[0100]
[Table 3]
[0101]
<Example 20>
After the sintered body was formed in the same manner as in Example 18, it was treated in air at 1340 ° C. for 3 hours, and then annealed to 1000 ° C. at a rate of 0.5 ° C./min.
[0102]
<Example 21>
After forming the sintered body in the same manner as in Example 18, the pressure was 1.5 MPa by hot isostatic pressing (HIP) under an oxygen-containing mixed gas atmosphere with an argon gas / oxygen volume ratio of 90/10. An annealing treatment was performed at 1300 ° C. for 3 hours under the conditions, and then the temperature was lowered to 100 ° C. at a temperature lowering rate of 0.5 ° C./min.
[0103]
<Evaluation>
For Examples 20 and 21, the same color tone evaluation and mechanical property evaluation as described above were performed. The results are shown in Table 4 together with the results of Example 18, and in Examples 20 and 21 where the annealing treatment was performed, the results were 1 to 2 compared to Example 18 where the annealing treatment was performed with the same composition. The bending strength was improved by about 30%, and a great improvement was observed especially by annealing treatment by hot isostatic pressing.
[0104]
Moreover, as a result of observing the microstructure of these sintered bodies with a scanning electron microscope and a transmission electron microscope, it was found that annealing was performed in Examples 20 and 21 compared to Example 18 where annealing was performed. Grain growth of crystal grains due to was not observed.
[0105]
As a result, in Examples 20 and 21 where the annealing treatment was performed, the crystallinity at the grain boundary was increased, and the alignment of the crystal orientation at the grain boundary interface was improved, thereby improving the strength of the sintered body. It is guessed.
[0106]
Moreover, about each Example, when a sintered compact was sliced to thickness 0.2mm and the translucent was evaluated by visually observing the transmission degree of visible light, compared with Example 18, in Examples 20 and 21, it is a little. An improvement in opacity was observed. Such an improvement in translucency is considered to be brought about by suppressing the light scattering at the grain boundary as a result of improving the consistency at the grain boundary interface by the annealing treatment.
[0107]
[Table 4]
[0113]
【The invention's effect】
ContractClaim1The method for producing a colored zirconia composite ceramic sintered body according toA zirconia-based composite ceramic sintered body in which a first phase mainly composed of tetragonal zirconia and a second phase composed of alumina particles containing at least ceria as a stabilizer is dispersed, and as a coloring component element, a period Containing at least one element selected from elements belonging to Groups 6 and 8-10 in the second phaseA method for producing a colored zirconia-based ceramic sintered body, which comprises a first raw material component composed of tetragonal zirconia containing at least ceria as a stabilizer, and belongs to groups 6 and 8 to 10 in the periodic table in alumina powder. After mixing with a second raw material component containing at least one element selected from the elements, forming into a desired shape, and firing in an oxygen-containing atmosphere, the resulting colored sintered body is: Ceria suppresses low-temperature degradation of tetragonal zirconia, suppresses solid solution of colored component elements to tetragonal zirconia, suppresses strength deterioration of the sintered body, and further suppresses the deterioration of the sintered body by the second phase made of alumina. It has improved strength and has sufficient toughness and strength, and since the coloring component element is preliminarily contained in alumina at the time of firing, it is attached to the second phase made of alumina. Is capable of preventing the inhibition of color development by the coloring component element or a compound thereof to the periphery of the first phase of tetragonal zirconia with a solid solution of the constituent elements is promoted remains.
[0114]
  MaTheA pre-mixed powder prepared by mixing at least one color component element selected from Cr, Fe, Co or a compound thereof with alumina powder, and the color component element or compound thereof for the entire pre-powder powder The amount of oxide in terms of oxide is Cr₂O_Three0.01 to 20 mol%, Fe₂O_ThreeMixing was performed so that at least one of 0.01 to 20 mol% and CoO 0.01 to 15 mol% was satisfied and the total amount of these oxides in terms of oxide was 0.01 to 20 mol%. Since a pre-prepared powder is prepared and heat-treated in a temperature range of 500 to 1000 ° C. in an oxygen-containing atmosphere is used as the second raw material component, the effect of sufficient coloring by the color component element is obtained. In addition to being obtained, it is possible to prevent the occurrence of colored component elements that cannot be completely dissolved in the second phase, and it is possible to previously dissolve the colored component elements in the second raw material component. Further, the coloring component element or the compound thereof remains around the first phase composed of tetragonal zirconia, so that inhibition of color development can be prevented more reliably.
[0115]
  And claims2The invention of claim1In Cr₂O_Three, Fe₂O_ThreeIn order to prepare a pre-prepared powder by mixing at least one metal oxide powder selected from CoO and alumina powder, the second raw material in which the coloring component elements are dissolved in the pre-mixed powder by heat treatment Ingredients can be easily obtained.
[0116]
  And claims3The invention of claim1In at least one oxide precursor selected from a metal salt containing trivalent Cr, trivalent Fe, or divalent Co, an organometallic complex, or a metal alkoxide is dissolved in an organic solvent and mixed with alumina powder. Then, in order to prepare the pre-prepared powder by removing the solvent, the second raw material component in which the color component element is dissolved can be easily obtained by heat treatment of the pre-prepared powder.
[0117]
  And claims4The invention of claim1Thru3In any of the above, ceria-based tetragonal zirconia powder containing 8 to 12 mol% of ceria is used as the first raw material component, and the specific surface area of the first raw material component is 5 to 20 m.²g^-1In order to set the average particle size of the second raw material component to 0.1 to 0.3 μm, a part of the second phase crystal particles is dispersed inside the first phase crystal particles at the time of firing. The microstructure of the aggregate can be a so-called “nanocomposite structure”, and the strength and hardness of the sintered body can be further improved.
[0118]
  And claims5The invention of claim1Thru4In any one of the above, after firing the mixture of the first raw material component and the second raw material component, the temperature is equal to or lower than the firing temperature and 1000 ° C or higher in an oxygen-containing atmosphere. Since the annealing treatment is performed, the consistency of the grain boundary of the sintered body can be improved, light scattering at the grain boundary can be suppressed, and the translucent of the sintered body can be improved.
[0119]
  And claims6The invention of claim5In this case, as the annealing treatment, hot isostatic pressing is performed in an oxygen-containing atmosphere, so that the consistency of the grain boundaries of the sintered body can be improved, and light scattering at the grain boundaries can be suppressed. Translucent can be improved.

Claims (6)

A zirconia-based composite ceramic sintered body in which a first phase mainly composed of tetragonal zirconia and a second phase composed of alumina particles containing at least ceria as a stabilizer is dispersed, and the coloring component element is a periodic A method for producing a colored zirconia-based ceramic sintered body comprising at least one element selected from elements belonging to Group 6 and Group 8 to 10 in the second phase ,
A first raw material component composed of tetragonal zirconia containing at least ceria as a stabilizer, and alumina powder containing at least one element selected from elements belonging to Groups 6 and 8 to 10 in the periodic table. The two raw material components are mixed, formed into a desired shape, and then fired in an oxygen-containing atmosphere .
And, it is a pre-mixed powder prepared by mixing at least one kind of color component element selected from Cr, Fe, Co or its compound with respect to the alumina powder, amount is Cr ₂ O ₃ 0.01 to 20 mol% as oxides of the compounds, Fe ₂ O ₃ 0.01 to 20 mol%, of the CoO0.01~15 mol%, either at least A pre-prepared powder was prepared by mixing so that the total amount of these oxides in terms of oxide was 0.01 to 20 mol%, and the pre-prepared powder was heated to a temperature of 500 to 1000 ° C. in an oxygen-containing atmosphere. What was heat-processed in the range is used as said 2nd raw material component , The manufacturing method of the coloring zirconia type composite ceramic sintered compact characterized by the above-mentioned . The colored zirconia system according to claim 1 , wherein a pre-prepared powder is prepared by mixing at least one metal oxide powder selected from Cr ₂ O ₃ , Fe ₂ O ₃ and CoO with an alumina powder. A method for producing a composite ceramic sintered body. After dissolving at least one oxide precursor selected from a metal salt containing trivalent Cr, trivalent Fe, or divalent Co, an organometallic complex, and a metal alkoxide in an organic solvent, and mixing with alumina powder 2. The method for producing a colored zirconia composite ceramic sintered body according to claim 1 , wherein a pre-prepared powder is prepared by removing the solvent. The ceria-based tetragonal zirconia powder containing 8 to 12 mol% of ceria is used as the first raw material component, and the specific surface area of the first raw material component is 5 to 20 m ² g ^−1, and the average grain of the second raw material component The method for producing a colored zirconia composite ceramic sintered body according to any one of claims 1 to 3 , wherein the diameter is 0.1 to 0.3 µm. After firing and mixing the first raw material component and the second raw material component, annealing is performed in an oxygen-containing atmosphere at a temperature not higher than the baking temperature and not lower than 1000 ° C. A method for producing a colored zirconia composite ceramic sintered body according to any one of claims 1 to 4 . The method for producing a colored zirconia composite ceramic sintered body according to claim 5 , wherein hot annealing is performed under an oxygen-containing atmosphere as the annealing treatment.