JP2002145663A - Zirconia-based ceramic and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zirconia-based ceramic which has excellent high temperature strength and high temperature durability and a stable and high ionic conductivity and exhibits excellent performance, e.g., when it is used as a solid electrolyte membrane for a fuel cell, and to provide a method of producing the same. SOLUTION: The zirconia-based ceramic contains 2.8 to 4.5 mol% yttria and shows XRD diffraction peaks of tetragonal zirconium oxide, described in the JPCDS card (17-0923), XRD diffraction peaks of monoclinic zirconium oxide, described in the JPCDS card (13-307), and XRD diffraction peaks of yttrium.zirconium oxide, described in the JPCDS card (30-1468).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zirconia ceramic and a method for producing the same, which is excellent in high-temperature strength and high-temperature durability, has a stable high ionic conductivity, and is excellent, for example, for a solid electrolyte membrane of a fuel cell. The present invention relates to a zirconia ceramic having excellent performance and a method for producing the same.

[0002]

2. Description of the Related Art Zirconia ceramics partially stabilized with 2.8 to 4.5 mol% of yttria are zirconia obtained by stabilizing a tetragonal crystal, which is a high-temperature stable phase, at room temperature, and 6 to 12 mol%. It is considered to be very excellent in mechanical strength at room temperature and its toughness as compared with cubic crystal fully stabilized zirconia-based ceramics containing yttria.

[0003] However, the ionic conductivity at high temperatures is inferior to cubic zirconia ceramics than to cubic zirconia ceramics, because tetragonal zirconia ceramics have a higher oxygen conductivity in the bulk. This is probably because the number of vacancies is small and the grain boundary length between the grains is long.

[0004] Therefore, when used at a high temperature, the ionic conductivity is lower than that of cubic zirconia, but tetragonal zirconia is converted to a solid electrolyte membrane by taking advantage of the excellent mechanical strength and toughness of tetragonal zirconia. It is being considered for use. However, there are few examples of examining the ionic conductivity over time.

As an example of a study on the stability of ionic conductivity, there is an example in which the change with time in the conductivity of yttria-stabilized zirconia (YSZ) of 3Y, 8Y, and 10Y doped with yttria is studied up to 3,000 hours. Yes (Elec
trochemical Proceedings, vol. 97-18, p. 135).

According to this document, 3YSZ has an initial conductivity of about 0.055 S / cm,
It has been found that about 30% after 0 hour and about 33% after 3,000 hours, the reduction rate is 8YS.
Although it is less than the change with time of Z, it is difficult to say that the stability of the ionic conductivity is sufficient.

Japanese Patent Application Laid-Open No. 6-64969 discloses that, for the purpose of reducing the change with time in the electrical conductivity when the current is continuously supplied, yttria is dissolved in a solid solution in an amount of 2 to 12 mol% and alumina is added in an amount of 0.1 to 0.2 mol%. A zirconia-based solid electrolyte membrane containing 0.1 to 2% by mass is disclosed. However, this is a study of the change with time up to 8 hours. For example, since the durability life of 40,000 hours or more when practically used for a fuel cell is required, the change with time of 8 hours is used for evaluating the start level. It must be said that it is insufficient to evaluate the practical durability.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and the object thereof is to provide 2.8 to 2.8.
It is an object of the present invention to provide a zirconia ceramic containing 4.5 mol% of yttria, having stable oxygen ion conductivity, and having excellent strength and durability even at high temperatures, and a method for producing the same.

[0009] More specifically, the durability of the fuel cell system is set as one standard of 40,000 hours. In order to meet such a target, the rate of decrease in the amount of power generated per 1,000 hours is 1 hour. % Or less, preferably 0.5% or less, more preferably 0.1% or less.
It can guarantee 15% or less in the reduction rate in 000 hours,
An object of the present invention is to provide a zirconia ceramic and a method for producing the same.

[0010]

The zirconia-based ceramic according to the present invention, which can solve the above-mentioned problems, contains 2.8 to 4.5 mol% of yttria and has a JPCDS (Joint Committee on Power). Diffr
XRD diffraction peak of tetragonal zirconium oxide described in action standard) card (17-0923),
XRD diffraction peak of monoclinic zirconium oxide described in JPCDS card (13-307), and JPC
Yttrium zirconium oxide (Y _0.15 Zr) described in DS card 1988 edition (30-1468)
_The gist lies in that it is made of a zirconia ceramic having an XRD diffraction peak of _0.85 O _1.93 ).

The preferred thickness of the ceramic is 0.01
It is in the form of a thin film sheet having a thickness of about 0.5 mm. Such a zirconia ceramic in the form of a thin film sheet can be used very effectively for a solid electrolyte membrane used in a fuel cell or the like.

Further, the production method of the present invention is positioned as a method for industrially efficiently producing a zirconia-based ceramic having the XRD diffraction peak characteristic described above. The gist lies in the fact that a powder obtained by adding 0.1 to 1.8 mol% of a yttrium oxide powder to a zirconia-based powder containing 0 mol% is used as a raw material, which is molded and then sintered.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, in the present invention, 2.8 to 2.8 are used.
It contains 4.5 mol% of yttria and has the XRD diffraction peak of tetragonal zirconium oxide described in JPCDS card (17-923) together with the JPCDS card (13).
X of the monoclinic zirconium oxide described in -307)
RD diffraction peak and JPCDS card (30-146)
Research has been conducted on zirconia-based ceramics having an XRD diffraction peak of yttrium / zirconium oxide described in 8) from various angles in order to further improve the stability of conductivity.

As a result, as a zirconia ceramic, X described in JPCDS card (17-923) was used.
Diffraction described on a JPCDS card (17-923), with a tetragonal zirconium oxide having an RD diffraction peak as the main, together with a monoclinic zirconium oxide having an XRD diffraction peak described on a JPCDS card (13-307). JPCDS card (30-14) which appears as a diffraction peak larger than the peak by about 0.2 to 0.4 ° in plane spacing.
It has been found that those having the yttrium / zirconium oxide having the XRD diffraction peak described in (68) coexist with them are very excellent in the stability of ionic conductivity, that is, the conductivity with time.

First, the present invention is directed to a partially stabilized zirconia-based ceramic of the tetragonal type containing 2.8 to 4.5 mol% of yttria for the following reasons.

That is, the content of yttria is 2.8 mol%
If less than 1, the monoclinic proportion in the crystal structure of the sintered body increases, the zirconia stabilization becomes insufficient, and although the ionic conductivity changes little with time, its initial value is significantly lower, and Satisfactory high-temperature durability cannot be obtained.

On the other hand, the content of yttria is 4.5 mol%
Exceeds, the cubic proportion in the crystal structure of the sintered body increases, the initial value of the ionic conductivity increases, but the change with time increases, and the particle size increases and the distribution also increases. As a result, sufficient high-temperature strength cannot be obtained.

In order to effectively exert the effect of stabilizing the ionic conductivity by an appropriate amount of yttria, and to minimize the particle size and distribution of the sintered body as much as possible to enhance the high-temperature strength, the more preferable yttria content is 3. It is 0 mol% or more, more preferably 3.1 mol% or more, and 4.0 mol% or less, and further preferably 3.8 mol% or less.

The main component of the zirconia-based ceramics according to the present invention is tetragonal, but the partial mixture of cubic and monoclinic greatly contributes to the stability of conductivity.
It was confirmed that the presence of cubic and monoclinic crystal systems was necessary. However, the proportion of monoclinic exceeds 2%,
Alternatively, if it is 0%, the phase change from tetragonal to monoclinic when exposed to high temperature for a long time is promoted, and as a result, the change with time of the conductivity becomes large and the durability at high temperature strength is poor. Become.

The monoclinic fraction is calculated by the following equation (1) (M) = m (1,1, -1) ÷ [t (1,1,1) + c (1,1,1)] ... X-ray diffraction peak intensity m (1,1, -1) measured with CuKα on monoclinic (1,1, -1) plane determined by (1), tetragonal (1,1,1)
From the peak intensity t (1,1,1) of the plane and the peak intensity c (1,1,1) of the cubic (1,1,1) plane of zirconia or yttrium / zirconium oxide, the peak intensity ratio is used. And expressed simply.

The proportion (M) of the monoclinic crystal calculated by the above formula (1) is preferably more than 0% and 2% or less, more preferably 0.05% or more and 1% or less.

When the crystal phase is observed over time, the phase change to monoclinic tends to be smaller when the monoclinic fraction (M) is contained at 0.05% or more than at 0%. This is expected to have a favorable effect on the stability of ionic conductivity and high-temperature durability.

The XRD diffraction peak identified as the cubic yttrium / zirconium oxide described in the JPCDS card (30-1468) is in the vicinity of the tetragonal XRD diffraction peak which is the main component of the zirconia-based ceramic according to the present invention. , And also located near the diffraction peak described in the JPCDS card (27-997) of cubic zirconia of the same crystal system, so that the XRD diffraction peak is hard to be clearly distinguished from its component ratio, In most cases, it is only recognized as a shoulder. Therefore, whether or not the cubic yttrium / zirconium oxide is present is determined by determining the (002) plane and the (200) plane of the plane spacing d observed in the region of 2.7 to 2.4 °. Depending on whether or not a peak of the (200) plane of cubic yttrium / zirconium oxide is observed between the peak of the (002) plane and the peak of the (200) plane of tetragonal zirconia by multiple peak separation. Was.

Even if only a diffraction peak identified as cubic zirconia is observed in the zirconia-based ceramics, it is difficult to obtain the stability of ionic conductivity as intended in the present invention. When the diffraction peak identified as zirconium oxide is not observed, the stability of the ionic conductivity and the high-temperature durability are insufficient, so the presence of the cubic yttrium / zirconium oxide indicates that the ionic conductivity is low. It is judged that this has a favorable effect on stability and high-temperature durability.

At this time, the JPCDS card (30-146)
The ratio of the XRD diffraction peak identified as cubic yttrium zirconium oxide described in 8) does not have a significant effect, and the fraction of the cubic crystal is not particularly limited.

In the present invention, in order to further enhance the room-temperature strength and the high-temperature strength, an appropriate amount of the above-mentioned yttria is contained, and a dispersion-strengthened oxide selected from oxides of 4A, 5A, 3B and 4B elements is used. At least one of 0.
It is also effective to contain about 1 to 2% by mass. Thus, at least one of the above dispersion-strengthened oxides is converted into (zirconia +) in zirconia partially stabilized with yttria.
0.1 to 100% by mass of the total of yttria)
When contained in an amount of 2% by mass, the dispersion-strengthened oxide is present near the grain boundary in the zirconia-based ceramics and prevents coarsening due to sintering of the particles when exposed to a high temperature for a long time. In addition, it is considered that the crystal phase transition from tetragonal to monoclinic or cubic is prevented.

The content of the dispersion-enhanced oxide is more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, in order to effectively exert the function of the dispersion-enhanced oxide. It is at most 1.0% by mass, more preferably at most 1.0% by mass.

As the dispersion-strengthened oxide, Group 4A,
Oxides of elements of 5A group, 3B group and 4B group,
Specifically, Ti, V, Nb, Ta, Al, Ga, I
Oxides of n, Ge, Sn, and Pb may be mentioned, and among these, titanium oxide, niobium oxide and aluminum oxide are particularly preferable.

The preferred particle size (grain particle size) of the zirconia-based ceramics according to the present invention has an average value of 0.1.
It is preferable that the conductivity is 0.4 to 0.8 μm, the maximum diameter is 0.4 to 0.8 μm, and the coefficient of variation is 30% or less in order to increase the stability of the conductivity with time.

Incidentally, those having an average particle diameter of less than 0.1 μm and a maximum diameter of less than 0.4 μm have a tendency that the interface resistance increases due to the increase in the particle interface and the conductivity decreases, while the average particle diameter decreases. Is over 0.4μm and maximum diameter is 0.8
If the particle size exceeds μm, the particle interface decreases, the interface resistance decreases and the conductivity increases, but the strength and high-temperature durability tend to decrease.

Here, the particle size of the sintered body is determined by scanning the surface of the zirconia-based ceramic with a scanning electron microscope (10.0
(0000 to 20,000 times), and based on the value obtained by measuring the total particle diameter of the visual field in the photograph with a vernier caliper, individual data are totaled, and the average particle diameter, maximum particle diameter, and minimum particle diameter of all particles are obtained. ,
The standard deviation and coefficient of variation were determined. When measuring the particle size with a vernier caliper, particles located at the edge of the photographic visual field, where the entire particle does not appear, are excluded from the measurement target.For particles having different vertical and horizontal dimensions, the longer diameter is used. The average value of the minor axis was directly used as the particle diameter.

Thus, the zirconia-based ceramics of the present invention are extremely excellent in all of the stability of ionic conductivity, the strength at normal temperature and the durability at high temperature, and therefore, for example, a solid electrolyte membrane for a fuel cell and a ferrule of an optical fiber. (Connectors), zirconia substrates for various printers, media for ball mills, etc.

Among them, the zirconia-based ceramics of the present invention using titanium oxide, niobium oxide or aluminum oxide as the dispersion-strengthened oxide has excellent conductivity, and has a fine and uniform particle diameter as described above. Thus, a thin sheet having a high degree of flatness with little undulation or warpage can be easily obtained, and its high-temperature strength and high-temperature durability are also extremely excellent.
By forming a thin film sheet having a thickness of about 0.5 mm, extremely excellent performance is exhibited as a solid electrolyte membrane for a fuel cell.

The method for producing the zirconia-based ceramic of the present invention having such excellent characteristics is not particularly limited, but a ceramic satisfying the above characteristics can be easily obtained by employing the following method.

The manufacturing method is a method in which a powder obtained by adding 0.1 to 1.8 mol% of yttrium oxide powder to zirconia powder containing 2.7 to 3.0 mol% of yttria is used as a raw material, and the resultant is molded. And then sintering.

The obtained sintered body is 2.8 to 4.0 as yttria based on the total amount of (zirconia + yttria).
The content of 5 mol% makes it possible to effectively exhibit the features of the present invention.

However, for example, in a method in which a predetermined amount of zirconia powder containing 3 mol% of yttria and zirconia powder containing 8 mol% of yttria are mixed, and then molded and sintered, tetragonal zirconia having small particles of a sintered body is used. Because of the large cubic zirconia mixture, the distribution of the particle size is widened, and the stability of conductivity and the durability of high-temperature strength as intended in the present invention cannot be obtained.

Further, the particle size of the finally obtained ceramics is affected to some extent by the particle size composition of the raw material powder to be used. The use of a material makes the particle size relatively small.

In order to efficiently obtain the zirconia-based ceramics having the above preferred particle size configuration, the zirconia powder containing 2.7 to 3.0 mol% of yttria used has an average particle size of 0.1 to 0.5 μm. A powder having a uniform particle size as small as possible (with a small particle size distribution), specifically, a powder in which 90% by volume or more of the powder is 1 μm or less, and an average particle diameter of yttrium oxide powder of 0.1 μm or less. 5-
In the range of 2.5 μm and as uniform as possible in particle size (particle size distribution is small), specifically, 90 μm of the powder
It is preferable to use one having a volume percentage of 5 μm or less.

In particular, the zirconia powder need not be a special product containing 2.7 to 3.0 mol% of yttria, but a powder containing 3 mol% of yttria which is a commercially available standard product (3Y product) And these are also preferable in terms of versatility and price.

However, the commercially available standard 3Y powder does not contain 3 mol% of yttria, and in the determination of yttrium by fluorescent X-ray analysis or ICP analysis, it is determined as 2.36%.
Since most of them contain only 8 to 2.95 mol%, it is desirable to add a predetermined amount of yttrium oxide powder in consideration of the fact that the amount does not reach 3 mol%.

However, the present inventors have further studied and found that what is more important in securing the above-mentioned particle size specified in the present invention is not the particle size composition of the raw material powder itself as described above, but the firing. This is the particle size composition of the solid component contained in the slurry when the ceramic molded body as the binding raw material is obtained, and the particle size composition is 0.05 μm in average particle diameter (50% by volume diameter).
m or more, 0.5 μm or less, 0.5 μm or more at 90% by volume diameter, 2 μm or less, 3 μm at the critical particle diameter (100% by volume diameter)
It has been confirmed that the use of a slurry satisfying the requirement of not more than m can more reliably provide a zirconia ceramic satisfying the requirement of the particle size.

A more preferred particle size composition of the solid component contained in the slurry is 0.1 μm or more and 0.4 μm or less in average particle diameter (50 volume% diameter) and 0.1 μm in 90 volume% diameter.
6 μm or more and 1.5 μm or less.

For the preparation of the slurry, a method of uniformly kneading and crushing a suspension of the raw material mixture including the raw material powder using a ball mill or the like is adopted.
Depending on the kneading conditions (including the type and amount of the dispersant), a part of the raw material powder undergoes secondary agglomeration or a part of the raw material powder is further crushed during the slurry preparation process. Is not necessarily the same as the particle size configuration of the solid component in the slurry. Therefore, when producing the zirconia-based ceramics of the present invention, the most influential factor on the particle size of the ceramics is the particle size composition of the solid component contained in the slurry before being formed into an unfired zirconia-based formed body. However, it is important to adjust so as to fall within the above preferable range.

The particle size composition of the solid components in the raw material powder and the slurry is a value measured by the following method.
That is, the particle size of the raw material powder was determined using a laser diffraction particle size distribution analyzer “SALD-1100” manufactured by Shimadzu Corporation, and an aqueous solution in which 0.2% by mass of sodium metaphosphate was added as a dispersant in distilled water was used as a dispersion medium. And the measured value after adding 0.01 to 0.5% by mass of the raw material powder in about 100 cm ^{3 of the} dispersion medium and ultrasonically dispersing for 1 minute to disperse;
The particle size composition of the solid components in the slurry is such that a solvent having the same composition as the solvent in the slurry is used as a dispersion medium, and each slurry is added in an amount of 0.1 to 1% by mass in 100 cm ^{3 of the} dispersion medium. Similarly, it is a measured value after being dispersed by ultrasonic treatment for 1 minute.

As a method of forming the zirconia sheet of the present invention, a slurry comprising the above-mentioned ceramic raw material powder, a binder and a dispersion medium is coated on a support plate or a carrier film by a doctor blade method, a calendar method, an extrusion method or the like. It is spread and formed into a sheet, dried, and the dispersion medium is volatilized to obtain a green sheet, which is cut, punched, etc., and arranged in an appropriate size, and then placed on a porous setter on a shelf board. 1300-16
A method of heating and firing at a temperature of about 00 ° C. for about 1 to 5 hours is employed.

The sheet-shaped zirconia-based ceramic has high thermal, mechanical, electrical and chemical properties, and is used, for example, for a solid electrolyte membrane of a fuel cell. When practically used for solid electrolyte membranes, the sheet thickness should be 0.01 mm or more, more preferably 0.02 mm or more, and 0.5 mm or less, in order to minimize the conduction loss while satisfying the required strength. More preferably, it is good to be 0.2 mm or less.

The type of the binder used here is not particularly limited, and a conventionally known organic or inorganic binder can be appropriately selected and used. As the organic binder, for example, an ethylene copolymer,
Styrene-based copolymer, acrylate-based and methacrylate-based copolymer, vinyl acetate-based copolymer, maleic acid-based copolymer, vinyl butyral-based resin, vinyl acetal-based resin, vinyl formal-based resin, vinyl alcohol-based resin, wax And celluloses such as ethylcellulose.

Among these, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, and the like, from the viewpoints of moldability and strength when obtaining an unfired zirconia-based molded article, and thermal decomposability upon firing. Alkyl acrylates having an alkyl group having 10 or less carbon atoms such as 2-ethylhexyl acrylate, and methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl 20 carbon atoms such as methacrylate
Alkyl methacrylates having the following alkyl groups,
Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate and hydroxypropyl methacrylate; aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate Having a number average molecular weight of 20,000 to 200, obtained by polymerizing or copolymerizing at least one kind of a carboxyl group-containing monomer such as maleic acid half ester such as (meth) acrylic acid, maleic acid and monoisopropyl malate. 000, more preferably 5
000-100,000 (meth) acrylate copolymers are recommended as preferred. These organic binders can be used alone or, if necessary,
More than one species can be used in appropriate combination. Particularly preferred is a polymer of a monomer containing 60% by mass or more of isobutyl methacrylate and / or 2-ethylhexyl methacrylate.

As the inorganic binder, zirconia sol, silica sol, alumina sol, titania sol and the like can be used alone or in combination of two or more.

The ratio of the binder used to the total powder of the zirconia-based raw material powder and the yttrium oxide powder is such that the binder is 5 to 3 in terms of solid content based on 100 parts by mass in total.
The amount is preferably 0 parts by mass, more preferably 10 to 20 parts by mass. When the amount of the binder used is insufficient, the strength and flexibility of the molded product become insufficient, and when the amount is too large, the viscosity of the slurry is increased. Not only the adjustment becomes difficult, but also the decomposition and release of the binder component during firing are large and intense, making it difficult to obtain a homogeneous sintered body.

The solvent used for producing the green zirconia compact is water, methanol, ethanol,
-Alcohols such as propanol, 1-butanol and 1-hexanol; ketones such as acetone and 2-butanone; aliphatic hydrocarbons such as pentane, hexane and heptane; aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene. Hydrogens, acetates such as methyl acetate, ethyl acetate, butyl acetate and the like are appropriately selected and used.
These solvents can be used alone or in combination of two or more. The amount of these solvents used is
The viscosity of the slurry at the time of forming the green sheet may be appropriately adjusted in consideration of the viscosity of the slurry, but is preferably adjusted so that the slurry viscosity is in the range of 1 to 10 Pa · s, more preferably 2 to 5 Pa · s. .

In preparing the slurry, a polymer electrolyte such as polyacrylic acid and ammonium polyacrylate, an organic acid such as citric acid and tartaric acid, isobutylene or styrene are used to promote deflocculation and dispersion of the zirconia-based raw material powder. A dispersant comprising a copolymer of styrene and maleic anhydride and its ammonium salt or amine salt, a copolymer of butadiene and maleic anhydride and its ammonium salt, etc .; phthalate for imparting flexibility to the green compact Plasticizers such as phthalic acid esters such as dibutyl acid and dioctyl phthalate, glycols such as propylene glycol, and glycol ethers; and surfactants and defoamers can be added as necessary.

The slurry composed of the above raw materials is formed by the above-described method and dried to obtain a zirconia-based green body, which is then fired to obtain the zirconia-based ceramic of the present invention.

In this firing step, as a means for obtaining a thin sheet-like sintered body having a high flatness without causing deformation such as warpage or undulation, it has an area larger than that of the green sheet and conforms to JIS K7125 (1987). )), A porous sheet having a static friction coefficient of 1.5 or less and a gas permeability of 0.0005 m / s · kPa or more measured in accordance with the “Test method for friction coefficient of plastic films and sheets”. It is preferable that the green sheet is sandwiched and fired so that the peripheral edge thereof does not protrude, or that the porous sheet is placed so that the peripheral edge of the green sheet does not protrude before firing.

[0056]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples, and the scope of the present invention can be adapted to the above and following points. It is also possible to carry out the present invention with appropriate modifications, all of which are included in the technical scope of the present invention.

Example 1 2.93 mol% yttria partially stabilized zirconia powder (manufactured by Sumitomo Osaka Cement: trade name "OZC-3YD")
And yttrium oxide powder (trade name: “high-purity yttrium oxide” manufactured by Santoku Metal Industry Co., Ltd.) so as to be 0.57 mol% as yttria, and a total of 100 parts by mass and 60 parts by mass of isopropyl alcohol A mixture obtained by adding titanium isopropoxide to titanium oxide in an amount of 0.3 parts by mass was added, isopropyl alcohol was distilled off under reduced pressure by a rotary evaporator, and further dried under reduced pressure, and then calcined at 800 ° C. to obtain titanium oxide. Is 0.3
3.5% by weight of yttria-partially stabilized zirconia powder equivalent to 3.5% by mole dispersed in mass% was obtained.

100 parts by mass of the obtained powder was mixed with a binder (molecular weight: 3) comprising a methacrylic acid ester copolymer.
0000, glass transition temperature: -8 ° C, solid content: 5
(0% by mass), 14 parts by mass of dibutyl phthalate as a plasticizer, 50 parts by mass of a mixed solvent of toluene / isopropyl alcohol (mass ratio = 3/2) as a dispersion medium, and zirconia balls having a diameter of 5 mm were charged. Put in a nylon pot and set to 70% of the critical speed at about 60 rpm.
The mixture was kneaded for 0 hour to prepare a slurry.

A part of this slurry was sampled, and toluene /
After diluting with a mixed solvent of isopropyl alcohol (mass ratio: 3/2) and measuring the particle size distribution of solid components in the slurry using a laser diffraction particle size distribution analyzer “SALD-1000” manufactured by Shimadzu Corporation, Average particle size (50
Volume% diameter) 0.61 μm, 90 volume% diameter 1.63 μm
m and the critical particle size (diameter of 100% by volume) were confirmed to be 3.2 μm.

The slurry is concentrated and defoamed to a viscosity of 3P.
a.s (23 ° C.), finally passed through a 200-mesh filter, and then coated on a polyethylene terephthalate (PET) film by a doctor blade method.
A green sheet having a thickness of about 0.26 mm was obtained.

This green sheet is cut, and a 99.5% alumina porous plate having a maximum swelling height of 10 μm (static friction coefficient: 0.97, air permeability: 0.003 m / s) is cut above and below the green sheet.
After defatting by sandwiching at kPa), the mixture is heated and baked at 1425 ° C. for 3 hours, and is a square having a side of about 100 mm square and a thickness of 3.5 mol% yttria containing 0.3 mass% of titanium oxide having a thickness of 0.2 mm. A partially stabilized zirconia sheet was obtained.

The surface of the obtained zirconia sheet piece was carbon-deposited to a film thickness of 150 ° by an ion sputtering method, and a scanning electron microscope “S-
570 type ", the particle diameter of all the particles in the visual field of the 15,000-fold photograph was measured with a vernier caliper, and the average particle diameter, maximum particle diameter and variation coefficient of the grain particles were determined based on the measured values. Was.

At this time, the particles located at the edges in the photographic visual field, in which the whole particles do not appear, are excluded from the object of measurement, and the particles having different vertical and horizontal dimensions are averaged of the major axis and minor axis. The value was taken as the particle size.

Also, a test piece of 8 × 50 mm square was prepared from the obtained zirconia sheet, and the three-point bending strength was measured at room temperature in accordance with J1S R1601, and was further measured at 950 ° C. for 1,000 hours or more in an electric furnace. The strength after holding was similarly measured at room temperature, and the high-temperature durability was determined from the ratio of the initial strength and the strength after a predetermined time by the following formula, and the results shown in Table 1 were obtained.

High-temperature durability: (strength after holding at 950 ° C. for a predetermined time) / (initial strength at 950 ° C.) Furthermore, a platinum wire having a diameter of 0.2 mm was wound around test pieces of the same dimensions at four locations at intervals of 1 cm. After applying a platinum paste, the coating was dried and fixed at 100 ° C., and the conductivity was measured by a DC four-terminal method using current and voltage terminals.

A zirconia sheet on which a platinum wire is wound so that the platinum wire is in close contact with the sample is sandwiched between alumina plates on both sides, and a load of about 500 g is applied from above to the zirconia sheet at 1,000 ° C. in an air atmosphere. After holding for a while, 0.
A constant current of 1 mA is passed, and the voltage of the two inner terminals is measured using a digital multimeter (trade name: TR684 manufactured by Advantest).
5 ").

Further, a test piece of 20 × 50 mm square was prepared at the same time, and further placed in an electric furnace at room temperature and 950 ° C.
The sheet held at 0 ° C. for 1,000 hours was subjected to CuK using an X-ray diffractometer “RU-300” manufactured by Rigaku Corporation.
α1 (50kV / 300mA) X-ray, wide angle goniometer, curved crystal monochromator, 2θ from 26 ° to 33
°, the (1,1, -1) plane of monoclinic zirconia observed near d = 3.16, and the (1) plane of tetragonal zirconia observed near d = 2.96. (1,1,1) plane, d = 2.9
From the respective peak intensities of the (1,1,1) plane of cubic zirconia observed near 7, the ratio (M) of the single crystal was calculated by the above formula (1).

Whether or not cubic yttrium / zirconium oxide is present is determined by determining that the plane distance d is 2.7 to
Due to the multiple peak separation of each (002) plane and (200) plane observed in the area of 2.4 °, a cubic crystal was formed between the (002) plane peak and the (200) plane peak of tetragonal zirconia. It depends on whether the peak of the (200) plane of the yttrium-zirconium oxide can be confirmed.

Example 2 2.96 mol% yttria partially stabilized zirconia powder (trade name “HSY-3.O” manufactured by Daiichi Rare Element Co., Ltd.) and yttrium oxide so as to have a yttria content of 1.04 mol% Powder (manufactured by Santoku Metal Industry Co., Ltd .: trade name "high-purity yttrium oxide"), and a total of 100 parts by mass thereof,
Aluminum oxide powder (trade name: T
M-DAR ") was added and mixed to obtain a partially stabilized zirconia powder equivalent to 4.0 mol% of yttria in which 1.0 mass% of aluminum oxide was dispersed.

Using this powder, a green sheet having a thickness of about 0.18 mm was obtained in the same manner as in Example 1, and a circular sheet having a diameter of about 100 mm was obtained using this green sheet in the same manner as in Example 1. A 4.0 mol% yttria partially stabilized zirconia sheet containing 1.0% by mass of aluminum oxide having a thickness of 0.15 mm was obtained.

Using this sheet, the grain size, maximum particle size, coefficient of variation, high temperature durability, monoclinic crystal ratio, determination of the presence of zirconium / yttrium oxide, and ionic conductivity were performed in the same manner as in Example 1 above. Was obtained, and the results shown in Table 1 were obtained.

Example 3 2.93 mol% yttria partially stabilized zirconia powder (manufactured by Sumitomo Osaka Cement Co., Ltd., trade name “OZC-3.0Y”)
C ") and yttrium oxide powder (manufactured by Santoku Kinzoku Kogyo Co., Ltd .: trade name" high-purity yttrium oxide ") so as to have a yttria concentration of 0.27 mol%, and 3.2 mol% of yttria partially stable Zirconia powder was obtained.

Using this powder, a green sheet having a thickness of about 0.2 mm was obtained in the same manner as in Example 1. Using this green sheet, a green sheet having a diameter of about 100 mm was obtained in the same manner as in Example 1.
A 3.2 mol% yttria partially stabilized zirconia sheet having a circular shape of 0.1 mm and a thickness of 0.18 mm was obtained.

Using this sheet, in the same manner as in Example 1, the grain particle diameter, the maximum particle diameter, the coefficient of variation, the high-temperature durability, the monoclinic crystal ratio, the determination of the presence of zirconium / yttrium oxide, and the ionic conductivity Was obtained, and the results shown in Table 1 were obtained.

Comparative Example 1 3.16 mol% yttria partially stabilized zirconia powder (manufactured by Sumitomo Osaka Cement Co., Ltd .: trade name “OZC-3.2Y”)
C)) and a thickness of about 0.2 m in the same manner as in Example 1.
m, and a 3.16 mol% yttria partially stabilized zirconia sheet having a diameter of about 100 mm and a thickness of 0.17 mm was obtained in the same manner as in Example 1 using this green sheet. .

Using this sheet, the grain size, maximum particle size, coefficient of variation, high temperature durability, monoclinic crystal ratio, determination of the presence of zirconium / yttrium oxide, and ionic conductivity were performed in the same manner as in Example 1 above. Was obtained, and the results shown in Table 1 were obtained.

Comparative Example 2 2.93 mol% yttria partially stabilized zirconia powder (manufactured by Sumitomo Osaka Cement Co., Ltd., trade name “OZC-3.0Y”)
C ") 94.6 parts by mass, and 5.4 parts by mass of 7.90 mol% yttria fully stabilized zirconia powder (trade name" OZC-8.0YC "manufactured by Sumitomo Osaka Cement Co., Ltd.)
Yttria-stabilized zirconia powder equivalent to 3.2 mol% was obtained.

Using this powder, a green sheet having a thickness of about 0.2 mm was obtained in the same manner as in Example 1, and using this green sheet, a green sheet having a diameter of about 100 mm was obtained in the same manner as in Example 1.
A 3.2 mol% yttria partially stabilized zirconia sheet having a circular shape of 0.1 mm and a thickness of 0.17 mm was obtained.

Using this sheet, in the same manner as in Example 1, the grain particle size, maximum particle size, variation coefficient, high-temperature durability, monoclinic crystal ratio, determination of the presence of zirconium / yttrium oxide, and ionic conductivity Was obtained, and the results shown in Table 1 were obtained.

[0080]

[Table 1]

[0081]

The present invention is configured as described above, and improves the lack of strength lacking in tetragonal partially stabilized zirconia-based ceramics containing a dispersion-strengthened oxide, and provides excellent high-temperature strength and high-temperature durability. Thus, it has become possible to provide a zirconia-based ceramic having high ionic conductivity and having a high level of ionic conductivity.

Further, according to the production method of the present invention, the above characteristics can be obtained by using a raw material powder having a final yttria content adjusted by mixing a predetermined amount of yttrium oxide with a zirconia-based powder containing a specific amount of yttria. Zirconia-based ceramics can be manufactured.

This zirconia ceramic is
Utilizing its excellent high-temperature strength, high-temperature durability, and stable ionic conductivity, it can be effectively used as a solid electrolyte membrane for fuel cells, ferrules (connectors) for optical fibers, zirconia substrates for various printers, media for ball mills, and the like. .

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masatoshi Shimomura 992, Nishioki, Okihama-shi, Aboshi-ku, Himeji-shi, Hyogo F-term (reference) in Nippon Shokubai Co., Ltd. BB08 EE11 EE12 HH05

Claims (3)

[Claims] An XRD diffraction peak of tetragonal zirconium oxide described in JPCDS card (17-923) containing 2.8-4.5 mol% of yttria, and a JPCDS card (13-307). XRD diffraction peak of the monoclinic zirconium oxide described in
A zirconia-based ceramic having an XRD diffraction peak of yttrium / zirconium oxide described in PCDS Card (30-1468). 2. The zirconia-based ceramic according to claim 1, which is used for a solid electrolyte membrane. 3. A zirconia-based powder containing 2.7 to 3.0 mol% of yttria and 0.1% of yttrium oxide powder.
A method for producing a zirconia-based ceramic, comprising obtaining a zirconia-based ceramic according to any one of claims 1 to 2, by using a powder to which 1 to 1.8 mol% is added as a raw material, and molding and sintering the powder.