KR950000697B1 - Sintered zirconia material and manufacturing method thereof - Google Patents

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Description

Zirconia Sintered Body and Manufacturing Method Thereof

1A is an electron micrograph (magnification: 132,000 times) of the zirconia sintered compact which concerns on the Example of this invention.

FIG. 1b is a schematic view of the electron microscope photograph shown in FIG. 1a. FIG.

2A is an electron micrograph (magnification: 170,000 times) of a zirconia sintered compact according to another embodiment of the present invention.

FIG. 2b is a schematic diagram that is simulated along the electron micrograph shown in FIG. 2a.

3A is an electron micrograph (magnification: 132,000 times) of a zirconia sintered compact according to another embodiment of the present invention.

FIG. 3b is a schematic view taken along the electron micrograph shown in FIG. 3a.

Figure 4a is an electron micrograph (magnification: 6,000 times) of the conventional zirconia sintered body.

FIG. 4b is a schematic diagram which is simulated along the electron micrograph shown in FIG. 4a. FIG.

The present invention relates to a zirconia sintered body and a manufacturing method thereof.

Conventionally, there are various kinds of zirconia sintered compacts. Japanese Unexamined Patent Application Publication No. 57-111278 discloses a so-called high strength zirconia sintered compact. This conventional zirconia sintered body contains 5 to 70 mol% of zirconia (quadratic zirconia) having a tetragonal crystal structure, and has a porosity of 2 to 10%. However, when this sintered body is subjected to thermal shock, tetragonal zirconia transforms into zirconia (monocrystalline zirconia) having a monoclinic crystal structure and expands by about 4% by volume. Since the region of compressive stress is formed in or near the zirconia, it acts to absorb strain due to thermal shock, so that the thermal shock strength is high. In addition, when the compressive stress region is formed, the elastic deformation energy decreases when the external stress is applied, so that the bending strength of the sintered body is also improved. However, the improvement in bending strength is not so remarkable because the porosity is relatively high by 2 to 10%, and further, the variation in strength is large. In addition, there is a drawback that the toughness is low.

On the other hand, Japanese Patent Application Laid-Open No. 59-227770 discloses that a zirconia powder containing a stabilizer and a black colorant is subjected to a hot press or hot hydrostatic pressure method using a graphite mold or a graphite die under an inert atmosphere. The sintering process for press) is performed and the zirconia sintered compact is obtained. By the way, it is described that this sintered compact has high heat resistance and toughness. However, graphite is used for this sintered compact, and carbon remains because it sinters in an inert atmosphere. When the carbon is used at a high temperature of 600 ° C. or higher, carbon is evaporated to form a cavity. Therefore, there is a drawback that the strength is greatly reduced, and even the strength is reduced even at room temperature.

The object of the present invention is to solve the above-mentioned shortcomings of the conventional sintered body, and the mechanical properties, in particular, the strength and toughness are high, moreover, the nonuniformity of the mechanical properties is extremely small, and the strength is reduced even when used at a high temperature of 600 ° C or higher. It is to provide a zirconia sinter with almost no.

Another object of the present invention is to provide a method for easily and safely producing a zirconia sintered body having the above-described mechanical properties.

In order to achieve the above object, in the present invention,

(a) contains at least 50 mole percent zirconia having a tetragonal crystal structure,

(b) contains 1.5 to 5 mol% of yttria;

(c) contains substantially no carbon,

(d) porosity is 0.6% or less,

(e) the pore size is 0.1 μm or less,

(f) A zirconia sintered body is provided, wherein the pores are mainly present at triple points of the zirconia grain boundaries.

In the present invention,

(a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder;

(b) calcining the zirconia powder at 800 to 1000 ° C, and then pulverizing the powder to prepare a raw material zirconia powder formed of a solid solution mixed with yttrium oxide;

(c) compressing the raw zirconia powder to form a green body,

(d) pre-sintering the molded body to produce a pre-sintered body having a bulk density of at least 95% of the theoretical density;

(e) sintering the presintered body by hot hydrostatic pressure method under an oxidizing atmosphere,

Provided is a method for producing a zirconia sintered body consisting of.

In the present invention, the following other manufacturing method is also applied.

Another method of manufacturing zirconia sintered body,

(a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder;

(b) calcining the zirconia powder at 800 to 1000 ° C, and then pulverizing the powder to prepare a raw material zirconia powder formed of solid solution mixed with yttrium oxide;

(c) compressing the raw zirconia powder to form a compact;

(d) a step of pre-sintering and sintering the above-mentioned molded product in a capsule by hot hydrostatic pressing under an oxidizing atmosphere,

It consists of.

Another method of the present invention for producing a zirconia sintered compact,

(a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder;

(b) calcining the zirconia powder at 800 to 1000 ° C, and then pulverizing the powder to prepare a raw material zirconia powder formed of solid solution mixed with yttrium oxide;

(c) a step of pre-sintering and sintering the raw material zirconia powder by directly solidifying the raw material zirconia powder using a hot hydrostatic pressure method under an oxidizing atmosphere after filling the capsule with the raw material zirconia powder,

It consists of.

Hereinafter, the zirconia sintered compact which concerns on this invention, and its manufacturing method are demonstrated in detail.

In the present invention, first, a zirconia powder containing yttrium oxide powder is prepared as follows. After mixing an aqueous solution containing zirconium chloride having a purity of 99.9% or more and an aqueous solution containing yttrium chloride having a purity of 99.5% or more in a predetermined ratio, there are known coprecipitation methods, hydrolysis methods, pyrolysis methods, and metals. The zirconia powder which has an average particle diameter of 0.1 micrometer or less and contains 1.5-5 mol% of yttrium oxide is prepared using the alkoxide method, the sol-gel method, and the gas phase method. The above-mentioned zirconia can be obtained from an aqueous solution containing zirconium nitrate with a purity of at least 99.9% and an aqueous solution containing yttrium nitrate with a purity of at least 99.5%, or from pure zirconia powder with a purity of at least 99,9% and a yttrium oxide powder having a purity of at least 99.9%. Powder may also be prepared.

Next, the powder is calcined at 800 to 1000 ° C, preferably 850 to 950 ° C, and then ground in a ball mill. If necessary, the above-described firing and grinding are repeated to obtain a raw material powder. This raw material powder forms a solid solution in which pure zirconia powder and yttrium oxide powder are uniformly mixed. In solid solution, zirconia varies depending on the purity, particle size, mixing ratio, firing temperature, firing time, etc. of zirconia, but usually forms a mixed phase of monoclinic and tetragonal.

Next, the raw material powder is molded into a desired molded body by using known molding methods such as rubber pressing, injection molding, mold molding, and extrusion molding.

Next, the above-mentioned molded product is put into a heating furnace, and the temperature is raised to a rate of 20 to 100 ° C / hr, preferably 30 to 70 ° C / hr, to 850 to 1000 ° C, preferably 900 to 950 ° C, and then to 1150 to 1150 ° C. The temperature is secondarily raised to 1550 ° C., preferably 1200 to 1450 ° C., more preferably 1300 to 1400 ° C. at a rate of 30 to 50 ° C./hour, and then maintained at that temperature for several hours. By this temperature raising step and subsequent temperature holding, a pre-sintered body having a bulk density of 95% or more (preferably 97.5% or more, more preferably 99% or more) of the theoretical density is obtained. In the above temperature raising process, the crystal structure of zirconia changes from the coexistence state of the monoclinic system and the tetragonal system to the tetragonal system, or to the coexistence state of the tetragonal system and the cubic system, or the cubic system. The transformation temperature and transformation speed of such a crystal structure depend on the amount of yttrium oxide. Therefore, with reference to the state diagram of the zirconia to be used, the presintering temperature having the above crystal structure is determined within the above-mentioned range. When the presintered body is cooled after presintering, the crystal structure of the zirconia changes, and the degree of change depends on the cooling rate. In zirconia with tetragonal crystal structure, part of tetragonal zirconia changes to monoclinic zirconia, from zirconia with mixed phase of tetragonal and cubic system, and part of tetragonal zirconia into monoclinic zirconia Part of the cubic zirconia changes to tetragonal zirconia and part of the tetragonal zirconia into monoclinic zirconia. In zirconia having a cubic crystal structure, some or most of the cubic zirconia changes to tetragonal zirconia, and part of the tetragonal zirconia into monoclinic zirconia. As a result, a mixed phase of tetragonal, monoclinic and cubic systems is produced.

Next, the pre-sintered body is sintered. In the sintering according to the present invention, sintering is carried out by a hot hydrostatic pressure method (hereinafter referred to as HIP method) under a controlled oxidation atmosphere. First, the presintered body is heated under a pressure of 1000 to 2200 kg / cm 2 (preferably 1500 to 2000 kg / cm 2) and stored at 1150 to 1500 ° C. (preferably 1300 to 1400 ° C.) for several hours. It cools at the cooling rate of 200-600 degreeC / hour (preferably 300-500 degreeC / hour), and a zirconia sintered compact is obtained.

In the HIP method, the oxygen concentration in the oxidizing atmosphere is controlled to 0.1 to 25% by volume, preferably 1 to 20% by volume, more preferably 3 to 10% by volume. If it is less than 0.1 volume%, oxygen concentration is too low, and a sintered compact will be reduced by the gas discharge | released from the component material which comprises a process furnace, and carbon will remain in a sintered compact. Moreover, when it exceeds 25 volume%, the flash point of the member which comprises a process furnace will fall largely, and the lifetime of a furnace will be shortened remarkably, and it is not practical.

In general, there are two methods for treatment by the HIP method. One is container powder solubilization by HIP method, and the other is container HIP method of pre-sintered body. In the former method, the raw material powder or the molded product is placed in a glass, ceramic or metal container (called a capsule), sealed and directly sintered. In the latter method, a pre-sintered body having a bulk density of 95% or more of the theoretical density is prepared as described above, and then sintered by a HIP method without a capsule.

The former method has the advantage that a compact sintered compact can be obtained even at a relatively low temperature. However, due to the use of a container, it is not suitable for producing a sintered body having a complicated shape. The latter method is not limited in such a shape, but requires that the pores of the pre-sintered body are not open pores but waste holes because of pressurization by gas. In this method, the pores of the pre-sintered body, in which the bulk density is 95% or more of the theoretical density, are almost waste pores, so there is no problem. In this HIP method, the pre-sintered body is solidified, and the bonding strength between the crystal grains is increased to obtain a sintered body having excellent mechanical properties. Moreover, a compact sintered compact is obtained even under relatively low temperature conditions. In the former method, a presintered body having a low bulk density may be used instead of the molded body. Since the absorbency of such presintered body is low and the shrinkage is accelerated compared to the raw powder or the molded body, even if the bulk density is relatively low, the presintered body can be easily manufactured by using the presintered body instead of the raw material powder or the molded body. .

As described above, the HIP method needs to be performed under an oxidizing component crisis. The HIP method is usually performed under an inert atmosphere such as argon gas atmosphere using a heater composed of carbon or the like. However, when the HIP method is performed in this manner, trace amounts of carbon and carbon monoxide remain during sintering. When the sintered compact thus obtained is used at a high temperature of 600 ° C. or higher, the remaining carbon and carbon monoxide become carbon dioxide gas and evaporate. As a result, a cavity is formed in the portion where carbon monoxide was located, and the high temperature strength of the sintered compact is greatly reduced.

The crystal structure of zirconia before sintering is a tetragonal system, a mixed phase of a tetragonal system and a cubic system, or a cubic system. This crystal structure changes during cooling and depends on the cooling rate. In the case of zirconia having a tetragonal crystal structure, part of the tetragonal crystal structure is changed into a monoclinic crystal structure. In zirconia with tetragonal and cubic crystal structures, part of the tetragonal crystal structure is changed to monoclinic, part or most of the cubic crystal structure is changed to tetragonal, and part of the changed tetragonal crystal structure is monolithic again. Change to politics As a result, the crystal structure changes into a mixed phase (coexistence state) of tetragonal, monoclinic and cubic systems. In the case of zirconia having a cubic crystal structure, part or most of the cubic crystal structure changes into a tetragonal system, and a part of the changed tetragonal crystal structure changes into a monoclinic crystal structure.

In the sintered compact, the amount of static preventive rconia varies depending on various conditions such as purity, particle size, composition of the raw powder, density of the pre-sintered compact, temperature and time of the main sintering, and cooling conditions after the main sintering. Therefore, in manufacture, these conditions need to be strictly controlled. In the present invention, the amount of tetragonal zirconia needs to be 50 mol% or more. Preferably it is 70 mol% or more, More preferably, it is 80 mol% or more.

Zirconia containing tetragonal zirconia increases its strength and toughness by transformation of the crystal structure from tetragonal to monoclinic when subjected to external stress. This mechanism is called "stress organic transformation mechanism". In order to fully express the improvement effect of strength and toughness by this stress organic transformation mechanism, it is necessary to make the amount of tetragonal zirconia 50 mol% or more.

Here, the amount CT of the tetragonal zirconia (mol%) is calculated | required as follows.

That is, the sintered compact is cut into thin pieces, polished with # 150 to 300 grindstones, and optically polished with diamond paste. The optically polished surface of the sintered body thus processed was subjected to the X-ray diffraction method, and the diffraction intensity A (area strength, the same below) of the tetragonal zirconia, the diffraction intensity B of the monoclinic zirconia 111, and the monoclinic zirconia Obtain the diffraction intensity C on the 111 plane of, and use it to calculate the CT from the following equation. Here, the diffraction intensity uses a value after correction by the Lorentz factor.

CT = (A / (A + B + C)) × 100

The 111 plane of tetragonal zirconia is diffracted almost with the 111 plane of cubic zirconia. Therefore, in the X-ray diffraction method, since it is difficult to separate the diffraction intensities on both sides, the data obtained together is used as the diffraction intensity value of the 111 plane of tetragonal zirconia.

The Lorentz factor L is represented by the following equation.

L = (1 + cos ² 2θ) / (sin ² × cosθ)

Diffraction conditions are as follows.

I) The X-ray generator used is RU-200B manufactured by Rigaku Denkisha, Japan. This device is a rotary pair cathode type and uses X-ray source as CuK α ray and curved crystal monochromator.

Ii) The goniometer is a 2155D type manufactured by Rigaku Denkisha. The slit system of this goniometer is 1 ^o -0.15 mm-1 ^o and the detector is a scintillation counter.

V) The counter is of type RAD-B manufactured by Rigaku Denkisha.

I) Scan systems are 2θ / θ scans and step scans.

Ⅴ) 2θ measurement range is 27~33 and 70~76 ^{o o.}

I) The 2θ coefficient step is 0.01 ^o .

V) Counting time is 1 second / step.

In the same manner as described above, the amount of cubic zirconia (C _c ) (mol%) is obtained by the following equation.

C _c = (D / (D + E + F)) × 100

Here, D is the diffraction intensity of the 400 plane of cubic zirconia, the diffraction intensity of the 004 plane of tetragonal zirconia, and F is the diffraction intensity of the 220 plane of tetragonal zirconia.

When the quantity of tetragonal zirconia and cubic zirconia is calculated | required by said formula, the remainder is monoclinic zirconia.

Monoclinic zirconia sometimes forms microcracks or compressive stress fields around it. When too many nonuniformity is formed, the strength and toughness of a sintered compact will fall. Therefore, the amount of monoclinic zirconia is preferably 10 mol% or less from the above point of view. On the other hand, tetragonal zirconia in a zirconia sintered body has a stress organic transformation mechanism, and a nucleus needs to exist to cause transformation. In view of this, it is desirable to have a small amount of tantalum zirconia. That is, the presence of monoclinic zirconia causes microcracks and microdefects to function as a nucleus. Although the above-mentioned nucleus is necessary to cause stress organic transformation, when too much exists, the strength of the sintered compact is lowered. Therefore, in the present invention, it is preferable to suppress the amount of monoclinic zirconia to 10% or less in consideration of the balance between the promotion of stress organic transformation and the maintenance of strength.

Next, the reason for containing cubic zirconia is preferable.

The cubic crystal structure has the highest thermal stability among the three crystal structures. Therefore, by the presence of cubic zirconia, the heat resistance and the corrosion resistance of the sintered body can be improved in high temperature use. For sintered bodies containing at least 50 mole% tetragonal zirconia, cubic zirconia is present in a dispersed state around the tetragonal zirconia, or between particles of tetragonal zirconia, forming a matrix. When moisture, acid, or alkali acts on the zirconia sintered body, the stability of tetragonal zirconia is reduced, a part of tetragonal zirconia is transformed into a monoclinic system, and microcracks are generated at the intergranular position of tetragonal zirconia. This non-crack can cause sintered body breakdown. However, when cubic zirconia exists to some extent in a sintered compact, since cubic zirconia does not accompany the above-mentioned deformation | transformation, the progress of destruction is largely suppressed and the heat resistance and corrosion resistance of a sintered compact are improved. These improved properties are highly desirable for sintered bodies used under high temperature or other harsh conditions.

The sintered compact in this invention contains 1.5-5 mol% of yttrium oxide as a stabilizer. The range of 1.5 to 5 mol% is a necessary condition for the amount of tetragonal zirconia to be 50 mol% or more. However, it is not a sufficient condition. That is, the amount of tetragonal zirconia also varies depending on the raw material powder, presintering condition, main sintering condition, and the like as described above. These conditions and the amount of yttrium co-act with each other to make the amount of tetragonal zirconia 50 mol% or more. If the amount of yttrium oxide is less than 1.5 mol%, a sudden transformation from tetragonal zirconia to monoclinic zirconia in the cooling process is caused, and a large number of cracks are generated in the sintered compact by monoclinic zirconia, resulting in a decrease in strength and toughness of the sintered compact. . When the amount of yttrium oxide exceeds 5 mol%, it is difficult to control the amount of tetragonal zirconia to 50 mol% or more depending on the sintering or cooling conditions, and the strength and toughness of the sintered compact are also lowered. Preferred amounts of yttrium oxide are 1.75 to 4.5 mol%. In order to increase the toughness of the sintered compact, 1.75-2.25 mol% is preferable, and in order to increase the high temperature strength or heat resistance of the sintered compact under the temperature of 600 degreeC or more, 3.5-4.5 mol% is preferable. By using yttrium oxide, sintering is possible under relatively low temperature conditions, and a compact sintered body can be obtained. However, stabilizers can be used together. For example, oxides forming a solid solution with zirconia, such as magnesia, calcia and ceria, can be used together with yttrium oxide as a stabilizer.

The sintered compact which concerns on this invention WHEREIN: It does not contain substantially the carbon which becomes the cause of the strength fall of a sintered compact at 600 degreeC or more. Here, the sintered compact which does not contain carbon substantially is defined as follows.

That is, to analyze the amount of carbon in the sintered sintered body, various methods such as infrared absorption spectroscopy, secondary ion mass spectrometry (SIMS), laser Raman spectroscopy, etc. are used. When the sintered body was excited with light of 4880 Å and 4579 하여 by using an argon laser using Raman spectroscopy, when the presence of the carbon detected as amorphous carbon was not recognized at all, the sintered body Is defined as substantially free of carbon. The conditions of this measurement are as follows.

Device is Ramanov U-1000, manufactured by Jobin Yuon, France

The wavelength of the laser is 4880Å and 4579Å

Supply voltage is 1650V

Gate time is 1.0 seconds,

Scanning speed 60cm ^-1 / min,

Scan inc is 0cm ^-1 ,

Latency is 0 seconds,

Sample spacing is 1cm ^-1 ,

Repeat three times,

The spectral range is 1800 cm ^{-1 to} 1100 cm ^-1 ,

Next, in this invention, it is essential that the porosity of a sintered compact is 0.6% or less, and the pore size is 0.1 micrometer or less. Here, the porosity P (%) is defined by the following equation.

P = (1- (volume density / theoretical density)) × 100

Theoretical density d _th is obtained by the following equation.

d _th = 4 M / (d ³ N)

From here,

N is the avogadro constant (6.0 × 10 ²³ mol ⁻¹ ),

M is the molecular weight of zirconia,

d is the lattice parameter

The value of d depends on the crystal structure of zirconia and the amount of yttrium oxide, and is determined by X-ray diffraction.

In the present invention, the theoretical density of tetragonal zirconia is 6.03 to 6.09 g / cm 3, the theoretical density of cubic zirconia is 5.98 to 6.04 g / cm 3, and the theoretical density of monoclinic zirconia is 5.65 to 5.75 g / cm 3. The strength of the sintered compact and the variation in the strength greatly depend on the porosity, but also on the size of the pores. This is because the presence of pores causes stress concentration in that part. When the porosity exceeds 0.6% or the pore size exceeds 0.1 µm, the strength decrease and the variation in strength of the sintered body rapidly increase. Therefore, in the present invention, the porosity is limited to 0.6% or less, and the pore size is limited to 0.1 µm, preferably 0.05 µm or less, so that the sintered body does not have the above-described defects. Preferable porosity of a sintered compact is 0.4% or less, More preferably, it is 0.3% or less. In this field, Weibull modulus is used to represent the statistical deviation of the intensity. The larger the Weibull coefficient, the smaller the variation in strength of the sintered compact, and the higher the reliability of the sintered compact. This Weibull coefficient is defined as When the distribution function expressed by the Weibull coefficient is applied to the strength distribution of the sintered body, the following equation is established.

P _s (V) = exp (-V (σ-σ _U ) / σ _O ) ^m

From here,

P _s (V) is the stress σ applied, and represents the probability that the sintered body having the volume V will not be broken.

σ _O is the normalization parameter

σ _U is the stress at failure probability 0

m is the Weibull coefficient

The Weibull coefficient is regarded as the sintered body constant showing the strength deviation of the sintered body. The larger the value of m, the smaller the intensity deviation.

Next, in the sintered compact according to the present invention, the pores of the sintered compact exist mainly at triple points of the grain boundaries of zirconia. When observing a thinly cut sample (thickness 400-500 Pa or less) with a transmission electron microscope, the point where three or more crystal grains are connected to each other is called "triple point." The expression 'mainly at the triple point of the pore' is defined as follows. First, the structure of the sintered body was observed at a magnification of 20,000 to 40,000 times using a transmission electron microscope, and 50 crystal grains were appropriately selected from one observation field. The number, the number of pores present in the grain boundary, and the number of pores present in the triple point are measured. Four different viewing fields were then selected to measure the number of pores from each of the 50 particles as described above. As a result, the number of pores (N) and the number of pores (N _t ) present at triple points were measured from five observation fields. If N _t / N is greater than or equal to 0.8, this state is defined as that the pore is mainly in the triple point. It is preferable that the ratio of N _t / N is 0.9 or more. Here, the observation field having 5 or more pores localized in some particles was excluded from the measurement. If necessary, the magnification of the electron microscope may be increased to 100,000 to 200,000 times when the number of pores and the size of the pores are measured.

In measuring the pore size, 250 particles are selected as described above. In the present invention, the pore size of the sintered compact is substantially 0.1 µm or less. Substantially 0.1 μm or less is defined as 80% or more of the pores present at the triple point N _t having a pore size of 0.1 μm or less. Preferably, at least 90% of the pores present in the triple point have a pore size of 0.1 μm or less, and more preferably, the pore size is substantially 0.05 μm or less. In this case, substantially 0.05 μm or less may be defined as described above.

Generally, the pores appear in the particles, at grain boundaries or in triplets. The pores present in the particles and grain boundaries appear when the sintered compact is not dense enough or the crystal grains do not sufficiently grow. Such pores greatly reduce the strength of the sintered compact. The pore present at the triple point also lowers the strength of the sintered body, but the degree of deterioration is not so high that these pores do not reduce the bonding force between the particles. Therefore, when pores exist in the triple point, the strength of the sintered compact is sufficiently maintained to show the required strength.

The sintered compact which concerns on this invention has an average reflection coefficient of about 0.2-0.6, is transparent, and has a depth in hue. The average reflection coefficient is measured as follows.

That is, using a spectrometer, and using the white alumina sintered body as a standard sample, the spectral reflectance R of the sintered compact and the spectral reflectance R ₀ of the standard sample were obtained for a wavelength of 400 to 700 nm, and from them, respectively, The spectral reflection coefficient r _λ for the wavelength of is obtained.

r _λ = -Log (R / R ₀ )

Moreover, the average reflection coefficient r _m is calculated | required by integrating the spectral reflection coefficient calculated | required by said formula from wavelength 400nm to 700nm, and dividing it by a wavelength space | interval. In other words,

Here, the integrating sphere uses a diameter of 60 cm. In the measurement, the reflectance of the alumina sintered body which is a standard sample is assumed to be 100%. Moreover, the sample grinds the surface of a sintered compact with # 400 emery paper, and provides the grinding | polishing surface for a measurement.

In the sintered compact according to the present invention, the sintered compact may include a third component other than yttrium oxide. When the third component additionally contains 0.1 to 1% by weight of at least one metal oxide and chromium oxide selected from the group consisting of aluminum, titanium, copper, nickel, iron, cobalt, and the like, Strength and toughness are further increased. The preferred amount of the third component is 0.2 to 0.5% by weight.

Moreover, when colored sinter is needed, you may contain 0.01-2 weight% of coloring agents. For example, when 0.05 to 0.7% by weight of chromium oxide or 0.05 to 0.2% by weight of copper oxide is added, the sintered compact has brown or green color. In addition, it is preferable to add 0.05-2 weight% of erbium oxide to pink, and 1 to 2 weight% cerium oxide or 0.05-2 weight% vanadium to yellow. In addition, it is preferable to add 0.5 to 2% by weight of neodymium oxide or 0.05 to 0.3% by weight of cobalt oxide, and orange to 0.05 to 0.5% by weight of iron oxide, and a plurality of colorants may be used together.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

An aqueous solution containing zirconium chloride with a purity of 99.9% and an aqueous solution containing yttrium chloride with a purity of 99.9% are mixed so that the amount of yttrium oxide in the sintered compact is 1.5 mol%.

Next, the above aqueous solution was gradually heated to about 100 ° C, held at that temperature for about 150 hours to evaporate water, and then heated to about 900 ° C at a temperature increase rate of about 100 ° C / hr, and at about 3 ° C. Maintained for a time to obtain a powder (calcined powder). Further, this small component powder was ground with a bowl mill containing polyurethane, thereby obtaining a raw powder having an average particle diameter of about 0.07 µm.

Next, a green body was obtained from the raw material powder using a rubber press method. The pressing force at the time of shaping | molding was 4000 kg / cm <2>.

Thereafter, the above-mentioned molded product was put into a heating furnace, and the temperature was raised to about 1200 ° C. at a rate of 50 ° C./hour up to about 900 ° C., and more than about 40 ° C./hour, and then maintained at that temperature for about 2 hours. The preform was obtained having a bulk density of about 98% of the theoretical density.

Next, the preliminary sintered body was sintered using the HIP method. That is, using a platinum heater, the pre-sintered body was heated up to about 1200 ° C at a rate of about 450 ° C / hr under an oxidizing atmosphere in which oxygen was about 3% and the remainder was argon gas, and at the same time, the gas pressure was 2000 kg / cm 2. The pressure was increased so as to be maintained for about 1.5 hours, and then cooled at a rate of about 400 ° C to obtain a sintered compact.

For the sintered body described above, the amount of tetragonal zirconia, porosity and pore size, pore position, presence of carbon, bending strength and fracture toughness, the Weibull coefficient, and the air were maintained at 1000 ° C. for 100 hours. The subsequent bending strength (hereinafter referred to as high temperature strength) was measured. In addition, for the measurement of the size and position of the pores, the microstructure of the thin film sintered body prepared by cutting the sintered body with a microtome and thinning it by Ar ion impact was used for transmission electron microscope (TEM, manufactured by Hitachi, Output: 200 (Iii) was used. Bending strength σ _f is calculated by the following equation.

Where P is the breaking load, L is the span length (= 20 mm), b is the width of the sample, and d is the thickness.

For the measurement of fracture toughness, the IM method (Indentation Microfracture method) was applied.

This method is based on the cracks formed radially around the indentation under the beakers arm vortex load exceeding the critical load P _c required for cracking. The test piece is polished on the optical surface. The length of Palmgvist cracks and indentations produced on the samples subjected to a 20 kg beakers indentation load was measured by an optical microscope. Then, fracture toughness was obtained from the following formula developed by Niihara et al.

Where K _1C is the fracture toughness, E is the Young's modulus (~ 200GPa), H is the beaker hardness (MPa), ψ is the constraint factor (˜3), a is 1/2 of the diagonal of the beaker compression, c is the radius of the surface crack measured from the center of the indentation to the end of the crack.

The Weibull coefficient was obtained by measuring 20 times.

The measurement results were as follows.

Amount of tetragonal zirconia: 88 mol%

Porosity: 0.6%

Pore size: 0.1㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1,000MPa

Fracture Toughness: 16MPa√m

Waibull Coefficient: 14

High temperature strength: 980 MPa

The microstructure of the sintered compact is a transmission electron microscope (TEM, manufactured by Hitachi, Power: 200) as shown in FIG. 1a (magnification: 132,000 times) on a thin film prepared by cutting the sintered compact into microtomes and thinning by Ar ion impact. Measured by vi). In Fig. 1B, reference numeral 1a denotes zirconia crystal grains, and reference numeral 2a denotes pores. The pores 2a exist at triple points.

Example 2

The amount of yttrium oxide was made 3 mol% in the sintered compact. Presintering temperature was 1,450 ℃ and HIP temperature was 1400 ℃. Other conditions are the same as in Example 1. The obtained sintered compact was measured in the same manner as in Example 1. The measurement results are as follows.

Amount of tetragonal zirconia: 92 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.700MPa

Fracture Toughness: 7.0MPa√m

Waibull Coefficient: 15

High temperature strength: 1650 MPa

Figure 2a (micrograph, magnification: 170,000) shows the microstructure of the sintered body. FIG. 2B is a schematic diagram drawn along FIG. 2A. In Fig. 2b, reference numeral 1b denotes zirconia crystal grains, and reference numeral 2b denotes pores. The pores 2b are at double points.

Example 3

The amount of yttrium oxide was made 5 mol% in the sintered compact. Other conditions are the same as in Example 2. The measurement results are as follows.

Amount of tetragonal zirconia: 55 mol%

Porosity: 0.1%

Pore size: 0.02㎛ or less

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.350MPa

Fracture Toughness: 5.2MPa√m

Waibull Coefficient: 12

High temperature strength: 1340 MPa

FIG. 3A (micrograph, magnification: 132,000) shows the microstructure of the sintered body. FIG. 3b is a schematic diagram taken along FIG. 3a. In Fig. 3B, reference numeral 1c denotes zirconia crystal grains. Although no pores appeared in this micrograph, the pores were measured in other observation fields under a microscope.

Example 4

NiCl ₂ having a purity of 99.5% was added to the aqueous solution in order to obtain 0.3 wt% NiO as the colorant of the sintered compact. Other conditions are the same as in Example 3. The obtained sintered body was measured in the same manner as in Example 1, and the tristimulus values Y (brightness) and x, y (chromatic coordinates) of the sintered body were measured using CIE (a colorimeter manufactured by Suga Shikenki Co., Ltd.). Commission Infer national de eclairage (1931).

The colorimeter consists of a light emitter, a lens system, a color filter, a light receiver holding an optical system, and a measuring unit for indicating and calculating data. The colorimetric method is performed according to the above-described reflection method. First, the sintered body is cut out to a size of 5 mm x 5 mm or more (preferably 20 mm x 20 mm or more, thickness 3 to 5 mm), and the surface of the sample is polished with # 400 measuring abrasive paper, and then the surface thereof. Was polished in order using abrasive paper of # 600, # 800, # 1000, and finally the surface was finished by lapping with diamond paste having an average particle diameter of 3.0㎛. A colorimeter is placed on the obtained sample, and light from the light emitter is irradiated onto the sample surface. The light reflected from the sample is integrated by using the integrating sphere, and is received by the light receiver through a color filter installed in the integrating sphere corresponding to the three stimulus values X, Y and Z. An electrical signal corresponding to the tristimulus values X, Y, and Z from the light receiver is measured by the measurement unit and calculated by the predetermined colorimetric system (Y, x, y). Based on the CIE 1931 system, each of the color filters X (red), Y (green), and Z (blue) can obtain X, Y, and Z values from the system. Using X, Y, and Z, the chromaticity coordinates (x, y) are obtained from the following equation.

x = X / (X + Y + Z)

y = Y / (X + Y + Z)

Y represents lightness, white at 100% and black at 0%. The measurement results are as follows.

Amount of tetragonal zirconia: 53 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.300 MPa

Fracture Toughness: 5.0MPa√m

YB coefficient: 11

High temperature strength: 1280 MPa

3 stimulus value: Y = 3.4, x = 0.22,

y = 0.40

(Color: Nile green)

Example 5

CeCl ₃ having a purity of 99.5% was added to obtain 1.0% by weight of CeO ₂ as a colorant for the sintered body.

The other conditions are the same as in Example 3. The measurement results measured in the same manner as in Example 4 are as follows.

Amount of tetragonal zirconia: 54 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.280MPa

Fracture Toughness: 5.0MPa√m

Waibull Coefficient: 12

High temperature strength: 1250MP

3 Stimulus value: Y = 10.3, x = 0.28,

y = 0.45

(Color: light yellow)

Example 6

VCl ₂ having a purity of 99.5% was added to the aqueous solution to obtain 0.5% by weight of V ₂ O ₅ as a colorant for the sintered body.

The other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 52 mol%

Porosity: 0.5%

Pore size: 0.04㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.150MPa

Fracture Toughness: 5.1MPa√m

Waibull Coefficient: 10

High temperature strength: 1,120 MPa

3 stimulus value: Y = 606, x = 0.38,

y = 0.45

(Color: yellow)

Example 7

CrCl ₃ having a purity of 99.5% was added to the aqueous solution to obtain 0.2% by weight of Cr ₂ Cl ₃ as a colorant of the sintered compact. Other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 55 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.300 MPa

Fracture Toughness: 5.1MPa√m

YB coefficient: 11

High temperature strength: 1280 MPa

3 stimulus value: Y = 5.66, x = 0.48,

y = 0.30

(Color: brown)

Example 8

CrCl ₃ having a purity of 99.5% was added to the aqueous solution so as to obtain 0.2% by weight of Cr ₂ O ₃ as a colorant of the sintered compact. Other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 52 mol%

Porosity: 0.3%

Pore size: 0.03㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.250MPa

Fracture Toughness: 5.0MPa√m

Waibull Coefficient: 10

High temperature strength: 1,220MPa

3 stimulus value: Y = 6.3, x = 0.24,

y = 0.42

(Color: green)

Example 9

ErCl ₃ having a purity of 99.5% was added to the aqueous solution to obtain 0.5% by weight of Er ₂ O ₃ as a colorant for the sintered compact. The other conditions are the same as in Example 3, and the measurement process is the same as in Example 4.

Amount of tetragonal zirconia: 55 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.320MPa

Fracture Toughness: 5.0MPa√m

YB coefficient: 11

High temperature strength: 1,300MPa

3 Stimulus value: Y = 12.0, x = 0.42,

y = 0.24

(Color: pink)

Example 10

ErCl ₃ having a purity of 99.5% was added to the aqueous solution to obtain 0.2% by weight of CuO as a colorant for the sintered body. The other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 52 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.280MPa

Fracture Toughness: 5.5MPa√m

Waibull Coefficient: 12

High temperature strength: 1230 MPa

3 stimulus value: Y = 9.9, x = 0.26,

y = 0.28

(Color: blue)

Example 11

FeCl ₂ having a purity of 99.5% was added to the aqueous solution to obtain 0.5% by weight of Fe ₂ O ₃ as a colorant for the sintered compact. The other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 56 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.330MPa

Fracture Toughness: 5.3 MPa√m

Waibull Coefficient: 13

High temperature strength: 1,310MPa

3 stimulus value: Y = 7.6, x = 0.47,

y = 0.33

(Color: orange)

Example 12

CoCl ₂ having a purity of 99.5% was added to the aqueous solution to obtain 0.1% by weight of CoO as a colorant for the sintered body. Other conditions are the same as in Example 3, and the measurement process is the same as in Example 4. The measurement results were as follows.

Amount of tetragonal zirconia: 53 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.310MPa

Fracture Toughness: 5.1MPa√m

Waibull Coefficient: 12

High temperature strength: 1280 MPa

3 Stimulus value: Y = 1.30, x = 0.30,

y = 0.20

(Color: dark purple)

Comparative Example 1

The amount of yttrium oxide was made 1.2 mol% in the sintered compact. Other conditions are the same as in Example 1. The measurement procedure is the same as in Example 1. The measurement results are as follows. However, the size and position of the pores could not be measured because too many cracks exist due to the transformation from the tetragonal system to the monoclinic system, and the pores and the cracks cannot be distinguished.

Amount of tetragonal zirconia: 62 mol%

Porosity: 7%

Carbon: Not Detected

Bending Strength: 320MPa

Fracture Toughness: 4.3MPa√m

Waibull Coefficient: 5

High temperature strength: 100 MPa

Comparative Example 2

The amount of yttrium oxide was set to 5.5 mol% in the sintered compact. Other conditions were the same as in Example 3. The measurement procedure was the same as in Example 1. The measurement results are as follows.

Amount of tetragonal zirconia: 40 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 600MPa

Fracture Toughness: 4.5MPa√m

YB coefficient: 11

High temperature strength: 590MPa

Comparative Example 3

The pressure at the time of shaping a molded object was set to about 1,000 kg / cm <2>. Other conditions were the same as in Example 2. The measurement results are as follows.

Amount of tetragonal zirconia: 90 mol%

Porosity: 0.6%

Pore size: 0.12㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 1.350MPa

Fracture Toughness: 7.1MPa√m

Waibull Coefficient: 7

High temperature strength: 1,300MPa

Figure 4a (micrograph, magnification: 6,000 times) shows the microstructure of the sintered body. FIG. 4B is a schematic diagram taken along FIG. 4A. In FIG. 4B, reference 1d denotes zirconia crystal grains, and reference 2d denotes pores. The pores are present in the particles, grain boundaries, and triple points.

[Comparative Example 4]

The pressure at the time of shaping a molded object was set to about 2000 kg / cm <2>, and the presintering temperature was set to about 1450 degreeC. VHIP was performed at about 1400 degreeC using carbon heater and in argon gas atmosphere. Other conditions are the same as in Example 2. The measurement procedure was the same as in Example 1. Although the presence of carbon was recognized by laser Raman spectroscopy, the absolute amount of carbon cannot be measured by infrared absorption spectroscopy. Therefore, the amount is considered to be very small. The measurement results are as follows.

Amount of tetragonal zirconia: 94 mol%

Porosity: 0.05%

Pore size: 0.02㎛

Location of pore: mainly triple point

Bending Strength: 1.650MPa

Fracture Toughness: 6.5 MPa√m

Waibull Coefficient: 14

High temperature strength: 500MPa

[Comparative Example 5]

A sintered compact was obtained under the same conditions as in Comparative Example 2. However, the temperature at the time of obtaining a molded object was about 1500 degreeC, the pressure was about 2000 kg / cm <2>, and the main sintering temperature was about 1,400 degreeC. The measurement procedure was the same as in Example 1. The measurement results are as follows.

Amount of tetragonal zirconia: 32 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Not Detected

Bending Strength: 600MPa

Fracture Toughness: 5.1MPa√m

Waibull Coefficient: 12

High temperature strength: 590MPa

Comparative Example 6

Carbon heater was used for the HIP method, and HIP method was performed under Ar gas atmosphere after presintering. Other conditions were the same as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 53 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Detected by laser Raman spectroscopy

Bending Strength: 1.320MPa

Fracture Toughness: 5.1MPa√m

Waibull Coefficient: 10

High temperature strength: 400MPa

3 Stimulus value: Y = 0.10, x = 0.31,

y = 0.34

(Color: dark blue)

Comparative Example 7

Carbon heater was used for the HIP method, and after preliminary sintering, the HIP method was performed under an Ar gas atmosphere. Other conditions were the same as in Example 5. The measurement results are as follows.

Amount of tetragonal zirconia: 54 mol%

Porosity: 0.1%

Pore size: 0.02㎛

Location of pore: mainly triple point

Carbon: Detected by laser Raman spectroscopy

Bending Strength: 1.270MPa

Fracture Toughness: 5.5MPa√m

Waibull Coefficient: 12

High temperature strength: 380 MPa

3 Stimulus value: Y = 0.23, x = 0.32,

y = 0.35

(Color: dark yellow)

Comparative Example 8

Carbon heater was used for the HIP method, and after preliminary sintering, the HIP method was performed under an Ar gas atmosphere. Other conditions were the same as in Example 6. The measurement results are as follows.

Amount of tetragonal zirconia: 52 mol%

Porosity: 0.5%

Pore size: 0.04㎛

Location of pore: mainly triple point

Carbon: Detected by laser Raman spectroscopy

Bending Strength: 1.160 MPa

Fracture Toughness: 5.1MPa√m

YB coefficient: 11

High temperature strength: 320MPa

3 Stimulus value: Y = 0.15, x = 0.36,

y = 0.36

(Color: dark brown)

Comparative Example 9

Carbon heater was used for the HIP method, and after preliminary sintering, the HIP method was performed under an Ar gas atmosphere. Other conditions were the same as in Example 8. The measurement results are as follows.

Amount of tetragonal zirconia: 52 mol%

Porosity: 0.3%

Pore size: 0.03㎛

Location of pore: mainly triple point

Carbon: Detected by laser Raman spectroscopy

Bending Strength: 1.250MPa

Fracture Toughness: 5.0MPa√m

YB coefficient: 11

High temperature strength: 360MPa

3 Stimulus value: Y = 0.08, x = 0.32,

y = 0.36

(Color: dark green)

As shown in Comparative Examples 6 to 9 described above, the sintered body obtained by the HIP method under Ar gas atmosphere using a carbon heater was colored with a black system, so that a beautiful and colorful color could not be obtained.

Comparative Example 10

In Example 4, after the rubber pressing, the temperature increase rate of about 50 ° C / hr was heated to about 900 ° C, and then heated again to 1450 ° C at a temperature raising rate of 40 ° C / hr, and maintained at that temperature for 2 hours. The obtained sintered compact was obtained. This sintered compact was measured in the same manner as in Example 4. The measurement results are as follows.

Amount of tetragonal zirconia: 43 mol%

Porosity: 1.6%

Pore size: 0.2㎛

Pore location: exists in the particle and grain boundary.

Carbon: Not Detected

Bending Strength: 500MPa

Fracture Toughness: 5.5MPa√m

Waibull Coefficient: 10

High temperature strength: 480 MPa

3 Stimulus value: Y = 26.5, x = 0.30, y = 0.37 (color: light white green)

Comparative Example 11

In Example 5, after rubber pressing, the substrate was heated to about 900 ° C. at a rate of about 50 ° C./hour, then heated again to 1450 ° C. at a rate of 40 ° C./hour, held at that temperature for 2 hours, and sintered body Got. This sintered body was measured in the same manner as in Example 5. The measurement results are as follows.

Amount of tetragonal zirconia: 48 mol%

Porosity: 1.8%

Pore size: 0.2㎛

Pore location: exists in the particle and grain boundary.

Carbon: Not Detected

Bending Strength: 480 MPa

Fracture Toughness: 5.6MPa√m

YB coefficient: 11

High temperature strength: 460 MPa

3 Stimulus value: Y = 80.1, x = 0.31, y = 0.38 (color: white)

Comparative Example 12

In Example 6, after rubber pressing, the substrate was heated to about 900 ° C at a rate of about 50 ° C / hour, then heated again to 1450 ° C at a rate of 40 ° C / hour, held at that temperature for 2 hours, and sintered body Got. This sintered compact was measured in the same manner as in Example 6. The measurement results are as follows.

Amount of tetragonal zirconia: 45 mol%

Porosity: 2.0%

Pore size: 0.3㎛

Pore location: exists in the particle and grain boundary.

Carbon: Not Detected

Bending Strength: 430MPa

Fracture Toughness: 4.9MPa√m

Waibull Coefficient: 9

High temperature strength: 400MPa

3 Stimulus value: Y = 50.8, x = 0.35, y = 0.37 (color: pale yellow)

Comparative Example 13

In Example 8, after rubber pressing, the substrate was heated to about 900 ° C at a rate of about 50 ° C / hour, then heated again to 1450 ° C at a rate of 40 ° C / hour, held at that temperature for 2 hours, and sintered body Got. This sintered compact was measured in the same manner as in Example 8. The measurement results are as follows.

Amount of tetragonal zirconia: 49 mol%

Porosity: 1.7%

Pore size: 0.2㎛

Pore location: exists in the particle and grain boundary.

Carbon: Not Detected

Bending Strength: 480 MPa

Fracture Toughness: 5.2MPa√m

YB coefficient: 11

High temperature strength: 450 MPa

3 Stimulus value: Y = 71.6, x = 0.30, y = 0.39 (pale green)

Comparative Example 14

Cr ₂ Ol ₃ having a purity of 99.5% was added to the aqueous solution to obtain 3.0 wt% CrCl ₃ as a colorant for the sintered body. The production conditions for molding the molded body were the same as in Example 3. It heated to about 900 degreeC at the speed | rate of about 50 degreeC / hour, then heated again to 1450 degreeC at the speed | rate of 40 degreeC / hour, hold | maintained at that temperature for 2 hours, and obtained the sintered compact. This sintered compact was measured in the same manner as in Example 8. The measurement results are as follows.

Amount of tetragonal zirconia: 48 mol%

Porosity: 1.9%

Pore size: 0.2㎛

Pore location: exists in the particle and grain boundary.

Carbon: Not Detected

Bending Strength: 410MP

Fracture Toughness: 5.0MPa√m

Waibull Coefficient: 10

High temperature strength: 360MPa

3 Stimulus value: Y = 9.9, x = 0.28, y = 0.42 (Color: Slightly dark green)

As shown in the above Comparative Examples 10 to 14 compared with the sintered bodies obtained in Examples 4 to 8, each of the sintered bodies obtained by adding a colorant and sintering in the air does not have light transmittance. Since the color of a sintered compact becomes white and bright hue, even if it adds the same amount of coloring agents in Examples 4-8, there is no depth. One of the reasons is that the porosity and pore size are very large. In the present invention, the sintered compact can have a dark and deep color by suppressing the porosity to 0.6% or less and the pore size to 0.1 µm or less.

As described above, the zirconia sintered body according to the present invention has at least 50 mol% of tetragonal zirconia and 1.5-5 mol% of yttrium oxide, having a porosity of 0.6% or less, a pore size of 0.1 μm or less, and pores. Mainly present in the triple point, the strength and toughness of the sintered body can be increased, and the deviation is very small. Since the sintered body also contains substantially no carbon, the drop in strength can be almost prevented even when used under high temperature conditions of 600 ° C or higher.

In addition, the zirconia sintered body according to the present invention has a translucent and deep color tone. Therefore, it can be used for various uses. A usage example is shown below.

A. Exhaust chambers, turbochargers, stop caps, cylinders, cylinder liners, plate exhaust valve heads, gas turbine blades, combustors, warhead cones, insulation, and exhaust valves for valves (valve, valve body and Some materials of internal combustion engines such as valve boxes.

B. Dies, nozzles, capillaries, blocks or gauges for detailed surveys, rings, heating cylinders, insulation spacers, insulation sleeves, mechanical seals, plunger pumps, punches, springs, coil springs, bearing bowls, grinder bowls, Guide rollers, roller grinders with rollers, pump impellers for slurry, screws, sleeves, valves, orifices, tiles, sleeves for wire sheaths, drivers, and thread guides. Stuff for some.

C. Cutting materials such as cutters (slots, circular shears) or high temperature bearings for textiles, paper, film or tin tape, razor blades, barber blades, scissors, knives and kitchen knives.

D. Materials for medical instruments or materials such as surgical knives, tweezers, rooted teeth, crowns of teeth, materials for joint and bone fixation, etc.

E. Materials for jewelry or substitutes, such as jewelry, seals, tie pins, cufflinks and parts for watches.

F. Materials for sports or leisure equipment such as golf clubs and fishing line guides.

G. Ingredients for tableware such as spoons, forks and plates.

H. Materials for writing instruments such as balls for ballpoint pens and tips of pens.

Although only a few of the above-described embodiments of the present invention have been described in detail, it will be understood by those skilled in the art that there are many variations and modifications that can be made in specific embodiments that do not depart significantly from the novel methods and advantages of the present invention. Can be.

It is therefore to be understood that all such modifications and variations are intended to be included within the scope of this invention as defined in the following claims.

Claims (41)

Consists of a sintered body containing at least 50 mol% of zirconia having a tetragonal crystal structure, 1.5-5 mol% of yttrium oxide, and substantially free of carbon, and having a porosity of 0.6% or less The sintered compact has a pore size of 0.1 µm or less, and the pores mainly exist at the triple point of the zirconia grain boundary. The zirconia sintered compact according to claim 1, wherein the sintered compact contains 70 mol% or more of zirconia having a tetragonal crystal structure. The zirconia sintered compact according to claim 2, wherein the sintered compact contains 80 mol% or more of zirconia having a tetragonal crystal structure. The zirconia sintered compact according to claim 1, wherein the amount of zirconia having a monoclinic crystal structure in the sintered compact is 10 mol% or less. The zirconia sintered compact according to claim 1, wherein the sintered compact further contains zirconia having a cubic crystal structure. The zirconia sintered compact according to claim 1, wherein the sintered compact contains 1.75 to 4.5 mol% yttrium oxide. The zirconia sintered body according to claim 1, wherein the porosity of the sintered compact is 0.4% or less. The zirconia sintered compact according to claim 7, wherein the porosity of the sintered compact is 0.3% or less. The zirconia sintered body according to claim 1, wherein the pore size is 0.05 µm or less. The zirconia sintered body according to claim 1, wherein at least 80% of the pores of the sintered compact have a size of 0.1 µm or less. The zirconia sintered body according to claim 10, wherein at least 90% of the pores of the sintered compact have a size of 0.1 µm or less. The zirconia sintered body according to claim 1, wherein at least 80% of the pores of the sintered compact are present in triplet between particles. 13. A zirconia sintered body according to claim 12, wherein at least 90% of the pores of the sintered compact are present in the triplet between particles. 2. The sintered compact according to claim 1, wherein the sintered compact additionally contains 0.1 to 1% by weight as a third component of at least one metal oxide selected from the group consisting of aluminum, titanium, copper, nickel, iron, cobalt, chromium oxide, and the like. Zirconia sintered body, characterized in that. The zirconia sintered compact according to claim 14, wherein the third component is present in an amount of 0.2 to 0.5 wt%. The sintered compact according to claim 1, wherein the sintered compact is 0.05 to 0.7% by weight of chromium oxide, 0.05 to 0.2% by weight of copper oxide, 0.05 to 2% by weight of erbium oxide, 1 to 2% by weight of cerium oxide, and 0.05 to 2% by weight of acid. Zirconia sintered body further comprising at least one colorant selected from the group consisting of vanadium, 0.5-2 wt% neodymium, 0.05-3 wt% cobalt oxide, 0.05-0.5 wt% iron oxide and the like. . (a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder; (b) calcining the powder after firing the above-mentioned zirconia powder at 800 to 1000 DEG C. A process of producing a raw zirconia powder formed of a solid solution, (c) compressing the raw zirconia powder to form a molded body, and (d) pre-sintering the molded body to obtain a pre-sintered body having a bulk density of 95% or more of the theoretical density. A process for producing and (e) a method for producing a zirconia sintered body comprising the step of sintering the presintered body by hot hydrostatic pressure method under an oxidizing atmosphere. (a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder; (b) calcining the powder after firing the above-mentioned zirconia powder at 800 to 1000 DEG C. A process for producing a raw zirconia powder formed of a solid solution, (c) compressing the raw zirconia powder to form a molded body, and (d) pre-sintering by hot hydrostatic pressurization under the oxidation atmosphere by encapsulating the molded body in a capsule. The manufacturing method of a zirconia sintered compact comprised by the process of sintering. (a) preparing a zirconia powder containing 1.5 to 5 mol% of yttrium powder; (b) calcining the powder after firing the above-mentioned zirconia powder at 800 to 1000 DEG C. A process for producing a raw zirconia powder formed of a solid solution, and (c) filling the above-mentioned raw zirconia powder into a capsule, and then pre-sintering and sintering the raw zirconia powder by solidifying the raw zirconia powder directly using a hot hydrostatic pressure method under an oxidizing atmosphere. The manufacturing method of a zirconia sintered compact comprised by the process of doing. 18. The method for producing a zirconia sintered body according to claim 17, wherein an electric powder is prepared from an aqueous solution containing zirconium chloride having a purity of 99.9% or more and an aqueous solution containing yttrium chloride of 99.5% or more. 18. The method for producing a zirconia sintered body according to claim 17, wherein the powder obtained is prepared from an aqueous solution containing zirconium nitride having a purity of 99.9% or more and an aqueous solution containing yttrium nitride of 99.5% or more. 18. The method for producing a zirconia sintered body according to claim 17, wherein the powder obtained by zirconia powder having a purity of 99.9% or higher and yttrium oxide powder having a purity of 99.9% or higher is prepared. 18. The method for producing a zirconia sintered body according to claim 17, wherein the firing temperature is 850 to 950 캜. 18. The method according to claim 17, wherein the raw material zirconia powder additionally contains 0.1 to 1% by weight as a third component of at least one metal oxide selected from the group consisting of aluminum, titanium, copper, nickel, iron, cobalt and chromium oxides. Method for producing a zirconia sintered body characterized in that. The method for producing a zirconia sintered body according to claim 24, wherein the third component is contained in an amount of 0.2 to 0.5% by weight. 18. The method according to claim 17, wherein the raw zirconia powder is 0.05 to 0.7 wt% chromium oxide, 0.05 to 0.2 wt% copper oxide, 0.05 to 2 wt% erbium oxide, 1 to 2 wt% cerium oxide, 0.05 to 2 wt% Zirconia further comprising at least one colorant selected from the group consisting of vanadium oxide, 0.5-2% by weight neodymium oxide, 0.05-0.3% by weight cobalt oxide and 0.05-0.5% by weight iron oxide. Method for producing sintered body. 18. The method for producing sintered zirconia according to claim 17, wherein the oxygen concentration in the oxidation atmosphere is 0.1 to 25%. 28. The method for producing a zirconia sintered body according to claim 27, wherein the oxygen concentration is 1 to 20%. 29. The method for producing a zirconia sintered body according to claim 28, wherein the oxygen concentration is 3 to 10% by volume. 18. The method for producing a zirconia sintered body according to claim 17, wherein the oxidation atmosphere has a gas pressure of 1,000 to 2,200 kg / cm 2. The method for producing a zirconia sintered body according to claim 30, wherein the gas pressure is 1,500 to 2,000 kg / cm 2. 18. The method for producing a zirconia sintered body according to claim 17, wherein the bulk density of the presintered body is 97.5% or more of the theoretical density. 33. The method of claim 32, wherein the bulk density of the presintered body is at least 99% of the theoretical density. 18. The molded article according to claim 17, wherein the molded body is first heated to 850 to 1000 DEG C at a rate of 20 to 100 DEG C / hour, and then again heated to 1150 to 1550 DEG C at a rate of 30 to 50 DEG C / hour, and then maintained at that temperature. Method for producing a sintered sintered body, characterized in that to prepare a pre-sintered body. The method for producing a zirconia sintered body according to claim 34, wherein the temperature increase rate of the first heating is 30 to 70 deg. The method for producing a zirconia sintered body according to claim 35, wherein the temperature increase rate of the first heating is 30 to 50 ° C / hour. The method for producing a zirconia sintered body according to claim 34, wherein the temperature of the molded body after the first heating is 900 to 950 ° C. The method for producing a zirconia sintered body according to claim 34, wherein the temperature of the molded body after the second heating is 1,200 to 1,450 ° C. 18. The method for producing a zirconia sintered body according to claim 17, wherein the pre-sintered body is heated to 1150 to 1500 ° C, maintained at that temperature, and then cooled at a cooling rate of 200 to 600 ° C to carry out the main sintering. 40. The method for producing a zirconia sintered body according to claim 39, wherein the sintering temperature is 1,300 to 1,400 占 폚. A method for producing a zirconia sintered body according to claim 39, wherein the cooling rate is 300 to 500 deg.

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