JP5412390B2 - Method for producing scandia-stabilized zirconia sheet for solid oxide fuel cell and scandia-stabilized zirconia sheet for solid oxide fuel cell - Google Patents

Description

  The present invention relates to a method for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell, a scandia-stabilized zirconia slurry and a scandia-stabilized zirconia green sheet used in the method, and a solid oxide form produced by the method The present invention relates to a scandia-stabilized zirconia sheet for a fuel cell and a solid oxide fuel cell having the scandia-stabilized zirconia sheet for a solid oxide fuel cell as a solid electrolyte membrane.

  Fuel cells are attracting attention as a clean energy source. Improvements and practical application studies are being rapidly promoted mainly for household power generation, commercial power generation, and automobile power generation. Among such fuel cells, a solid oxide fuel cell is expected as a power source for home use and business use because of its high power generation efficiency and excellent long-term stability.

  In this solid oxide fuel cell, a ceramic sheet is used as a solid electrolyte membrane. Ceramics are superior in electrical properties and magnetic properties in addition to mechanical properties such as heat resistance. Among them, ceramic sheets mainly composed of zirconia have excellent oxygen ion conductivity, heat resistance, corrosion resistance, toughness, etc., so zirconia sheets are mainly used as solid electrolyte membranes for solid oxide fuel cells. Yes.

  Various additives are added to zirconia as a raw material for the zirconia sheet in order to control the crystal form. As such additives, oxides such as Sc, Y, Yb, Ca, Mg, Er, Dy, Gd, Eu, Al, Hf, and Ce are often used. Generally, zirconia to which these additives are added is called stabilized zirconia.

  Among these stabilized zirconia, scandia-stabilized zirconia is particularly excellent in oxygen ion conductivity. Therefore, a sheet made of scandia-stabilized zirconia is used as a solid electrolyte membrane of a solid oxide fuel cell. However, a sheet made of stabilized zirconia having a high scandia content is excellent in oxygen ion conductivity but poor in mechanical strength, and thus has to be thick. In addition, there is a problem that the occurrence rate of defective shape is high during sintering. In particular, as a form defect having a high occurrence frequency, there is a wavy undulation generated at the end.

  The scandia-stabilized zirconia sheet with ungelli cannot be screen printed accurately. Further, due to undulation, the contact area with the current collector is reduced. In addition, in a solid oxide fuel cell using a scandia-stabilized zirconia sheet with ungeli as a solid electrolyte membrane, the load due to cell stacking and the stress due to volume change during power generation are concentrated on the undulation, which is the starting point. Therefore, there is a problem that the solid electrolyte membrane is broken and the battery life is shortened. Therefore, the scandia-stabilized zirconia sheet having undele cannot be used as a solid electrolyte membrane. In recent years, the practical use of fuel cells has progressed, and the production of scandia-stabilized zirconia sheets as solid electrolyte membranes has also increased. Therefore, technology for suppressing undulation has become extremely important in reducing costs. Yes.

  However, the technology for reducing the undulation of the scandia-stabilized zirconia sheet has not been sufficiently studied so far. Therefore, there is no prior art document regarding the undulation of scandia-stabilized zirconia sheet. Similarly, there is no prior art document relating to improvement of underi for yttria-stabilized zirconia sheets. However, regarding the yttria-stabilized zirconia sheet, there are some findings regarding the tensile properties of the green sheet that is the precursor.

For example, in Patent Document 1, in order to increase the mechanical strength of the ceramic sheet and reduce the distortion of the shape, the tensile fracture elongation of the green sheet is set to 20 to 500%, and the tensile yield strength is set to 20 to 200 kgf / cm ² ( The manufacturing method adjusted to about 1.96-19.6 MPa is described. Since the distortion of the shape is mainly caused when the green sheet is cut, it is preferable that the above condition is satisfied at the time of cutting. Therefore, in order to suppress the strain at the time of cutting, the tensile fracture elongation (elongation rate at the maximum stress load) is set to a very large value of 20 to 500%.

  Patent Document 2 also describes a technique for setting the breaking strength of the green sheet in the cutting step to 300 to 1000 MPa and the maximum elongation at the time of cutting to 5 to 35%. In this technology, the breaking strength of the green sheet is set in a very high range in order to suppress distortion during cutting and burrs on the cut end face.

In addition, solid oxide membranes for solid oxide fuel cells are not oriented, they are used as parts for ion flow control heads and high-precision electric field shutters, and are composed of partially stabilized zirconia, etc., and a very thin ceramic there is intended for the manufacture of a sheet, but the tensile strength of the green sheet 10 kgf / cm ² or more, 200 kgf / cm ² or less (about 0.98MPa or more, less 19.6 MPa), elongation 0.5 mm ³ / kgf or more Patent Document 3 discloses a technique of 25.0 mm ³ / kgf or less. However, the purpose of this technology is specialized in suppressing the occurrence of cracks and the deterioration of the position accuracy of fine through-holes. Therefore, the specified range of tensile strength and elongation is very wide, but the through-holes should be formed well. Although the elongation is low, the tensile strength is high, or the tensile strength is low, but the elongation is high, or both are only moderately low green sheets, and both the tensile strength and elongation are high. A production example is not described.

Japanese Patent Laid-Open No. 11-207723 JP 2001-205607 A Japanese Patent Laid-Open No. 10-138226

  As described above, a technique that has been conventionally used as a solid electrolyte membrane of a solid oxide fuel cell and has been studied mainly for the purpose of reducing undulation of a sheet made of stabilized zirconia has not been sufficient.

  Therefore, the present invention has an object of providing a method for producing a scandia-stabilized zirconia sheet used as a solid electrolyte membrane of a solid oxide fuel cell while suppressing generation of undulation. Further, in the present invention, a scandia-stabilized zirconia slurry and a scandia-stabilized zirconia green sheet used in the method, and the scandia-stabilized zirconia sheet for a solid oxide fuel cell produced by the method and suppressed in undulation. Another object of the present invention is to provide a solid oxide fuel cell having the scandia-stabilized zirconia sheet for the solid oxide fuel cell as a solid electrolyte membrane.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, the occurrence of undulation in the scandia-stabilized zirconia sheet after firing has a high correlation with the maximum stress during the tensile test of the green sheet and the elongation at the maximum stress load, and the maximum stress and the maximum stress load. The present invention has been completed by finding that it can be remarkably suppressed by appropriately controlling the elongation at time.

  The method for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell according to the present invention is obtained by forming a slurry containing scandia-stabilized zirconia particles into a sheet and then drying it, and the maximum stress is 5.0 MPa or more and 20.0 MPa. And a step of producing a green sheet having an elongation rate of 5.0% or more and less than 20.0% at the maximum stress load; and firing the obtained green sheet to have a thickness of more than 100 μm and 300 μm or less Including a step of forming a zirconia sheet.

  As the plasticizer to be blended in the raw slurry of the scandia-stabilized zirconia green sheet used in the production method according to the present invention, it is preferable to use an oligomer plasticizer having a number average molecular weight of 500 or more and 8000 or less. If such an oligomer plasticizer is used, the shine of the green sheet can be suppressed.

  As the binder to be blended in the raw slurry of the scandia-stabilized zirconia green sheet used in the production method according to the present invention, the acid value is 0.1 or more and 60 or less, the amine value is 0 or more and 60 or less, and the hydroxyl value is 0 or more. And those composed of an acrylate copolymer of 60 or less are preferred. If such a binder is used, the slurry can be prepared well, and the peelability of the green sheet from the resin film can be enhanced.

  In the manufacturing method according to the present invention, when the elongation rate under maximum stress loading is x% and the maximum stress is yMPa, 7 ≦ x <20, y ≦ −0.25x + 14, and y ≧ −0. It is preferable to produce a scandia-stabilized zirconia green sheet that satisfies the relationship of 25x + 10. When a green sheet satisfying such a regulation is fired, the rate of occurrence of undulation can be reduced to 30% or less, and an efficient production of a scandia-stabilized zirconia sheet becomes possible.

  The scandia content in the scandia-stabilized zirconia particles is preferably 5 mol% or more. If the said content rate is 5 mol% or more, oxygen ion conductivity will improve remarkably.

  In preparing the scandia-stabilized zirconia green sheet, the drying temperature is 80 ° C. or higher and 120 ° C. or lower, or the ratio of the binder in the raw material slurry is 10 parts by mass or more with respect to 100 parts by mass of the scandia-stabilized zirconia particles. The average secondary particle size of the scandia-stabilized zirconia particles in the slurry is preferably 0.2 μm or more and 0.5 μm or less. By satisfying any one or more of these conditions, it becomes easy to produce a green sheet in which the above-mentioned maximum stress, etc., in particular during the tensile test satisfies the above-mentioned regulations, and as a result, the scandia stability for solid oxide fuel cells in which undulation is suppressed. It becomes possible to manufacture a zirconia sheet more efficiently.

  In the method of the present invention, the green sheet is preferably stored for 2 weeks or more before firing. The reason is not necessarily clear, but when stored for 2 weeks or more, undulation after firing is clearly reduced.

  The scandia-stabilized zirconia slurry according to the present invention is used in the above-described method of the present invention, and includes scandia-stabilized zirconia particles and an oligomer plasticizer having a number average molecular weight of 500 or more and 8000 or less. .

  The slurry further preferably contains a binder made of an acrylate copolymer having an acid value of 0.1 or more and 60 or less, an amine value of 0 or more and 60 or less, and a hydroxyl value of 0 or more and 60 or less. . Such a slurry is more easily prepared, and the green sheet obtained from the slurry is easily peeled from the resin film.

  The scandia-stabilized zirconia green sheet according to the present invention is obtained by molding and drying the slurry of the present invention, and has a maximum stress of 5.0 MPa or more and 20.0 MPa or less and elongation under maximum stress load. The rate is 5.0% or more and less than 20.0%.

  The scandia-stabilized zirconia sheet for a solid oxide fuel cell of the present invention is produced by the above-described method of the present invention, and has a feature that the difference in height of the undulation at the end is 20 μm or less.

  The solid oxide fuel cell of the present invention is characterized by having the scandia-stabilized zirconia sheet for a solid oxide fuel cell according to the present invention as a solid electrolyte membrane.

  According to the present invention, it is possible to efficiently manufacture a sheet made of scandia-stabilized zirconia and having significantly reduced undulation. Such scandia-stabilized zirconia sheet of the present invention can screen-print the electrode satisfactorily because undulation is reduced. In addition, since the location where the stress generated by the load generated when the cells are stacked and the volume change during power generation is concentrated is reduced, the solid oxide using the scandia-stabilized zirconia sheet according to the present invention as the solid electrolyte membrane The fuel cell has a long life. Therefore, the present invention makes it possible to mass-produce a sheet made of scandia-stabilized zirconia at low cost, and is very useful industrially as it can further promote the practical application of solid oxide fuel cells. It is.

  Hereinafter, the method of the present invention will be described in the order of execution.

(1) Slurry preparation step In the present invention, scandia-stabilized zirconia particles are used as raw material particles. In the present invention, undulation of the sheet made of scandia-stabilized zirconia is suppressed, stress concentration in the case of a solid oxide electrolyte film is eliminated, durability is improved, and a contact area with the current collector is improved.

Stabilized zirconia includes alkaline earth metal oxides such as MgO, CaO, SrO, BaO; Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , _{eu 2 O 3, Gd 2 O} 3, Tb 2 O 3, Dy 2 O 3, Ho 2 O 3, Er 2 O 3, Yb 2 O 3 rare earth element oxides such _{as; Sc 2 O 3, Bi 2} O 3 Examples thereof include zirconia containing one or more oxides such as In ₂ O ₃ as a stabilizer. Further, as other additives, SiO ₂ , Ge ₂ O ₃ , B ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ , Nb ₂ O _{5 and the} like may be contained. Among them, stabilized zirconia containing scandia or yttria as a stabilizer is preferable in order to ensure a higher level of oxygen ion conductivity and strength and toughness, and in particular, oxygen ion conductivity is more excellent. Therefore, stabilized zirconia containing scandia is preferred.

  The amount of metal oxide for converting zirconia to stabilized zirconia varies depending on the type. For example, as the stabilized zirconia used in the present invention, zirconia containing 4 mol% or more of scandia can be mentioned, and zirconia containing 5 mol% or more of scandia is preferable. On the other hand, even if the amount of scandia is too large, the performance reaches its peak, so from the economical viewpoint, the amount of scandia is preferably 12 mol% or less. In addition, since the crystal system may become rhombohedral when the amount of scandia increases, ceria, alumina, or the like may be added as a third component in order to stabilize the crystal system into a cubic system. Since the content of scandium contained in scandia can be measured using ICP analysis, X-ray fluorescence analysis, EPMA, etc., the mol% of scandia contained in stabilized zirconia should be calculated from the measured value. Can do.

  In the method of the present invention, first, a slurry containing scandia-stabilized zirconia particles is prepared. The slurry includes a scandia-stabilized zirconia particle, a solvent, a binder, a plasticizer, a dispersant, and the like.

  Solvents used for slurry preparation include alcohols such as methanol, ethanol, 2-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; acetic acid esters such as methyl acetate, ethyl acetate, and butyl acetate can be exemplified, and these are appropriately selected and used. These solvents can be used alone or in combination of two or more. The amount of these solvents to be used should be appropriately adjusted in consideration of the viscosity of the slurry during green sheet molding, preferably the slurry viscosity is 1 Pa · s or more, 20 Pa · s or less, more preferably 1 Pa · s or more, It is good to adjust so that it may become the range of 5 Pa.s or less.

  The type of binder used when producing the slurry is not particularly limited as long as it is decomposed by firing or removed by burning, and a conventionally known organic binder is appropriately selected and used. be able to. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, polyvinyl butyral resins, vinyl acetal resins, Examples thereof include vinyl formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose.

  Among these, from the viewpoints of green sheet moldability and strength, thermal decomposability during firing, and the like, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc. Alkyl acrylates having the following alkyl groups: alkyl groups having 20 or less carbon atoms such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, and cyclohexyl methacrylate Alkyl methacrylate having hydroxyethyl acrylate, hydroxypropyl acrylate Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as hydroxyethyl methacrylate, 2-hydroxy-1-methylethylacrylic acid and hydroxypropyl methacrylate; aminoalkyl such as dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate Acrylate or aminoalkyl methacrylates; Polymer obtained by polymerizing or copolymerizing at least one of carboxyl group-containing monomers such as maleic acid half ester such as (meth) acrylic acid, maleic acid and monoisopropylmalate Are preferably used.

  Among these, a (meth) acrylate copolymer having a number average molecular weight of 5,000 or more and 200,000 or less, and more preferably 10,000 or more and 50,000 or less is particularly preferable. These organic binders can be used alone or in combination of two or more as necessary. Particularly preferable is a polymer of a monomer containing 60% by mass or more of n-butyl methacrylate, isobutyl methacrylate and / or 2-ethylhexyl acrylate.

  Moreover, as a binder used by this invention, a thing with an appropriate acid value, an amine value, and a hydroxyl value is preferable.

  The acid value is expressed in mg of potassium hydroxide required to neutralize 1 g of binder. The acid value is preferably 0.1 or more and 60 or less, more preferably 0.2 or more and 40 or less, further preferably 0.3 or more and 20 or less, and further preferably 0.5 or more and 15 or less. By controlling the acid value within the above range, the stabilized zirconia particles in the slurry can be sufficiently dispersed, and the fluidity of the slurry can be maintained well. The acid value can usually be measured by a titration method.

  The amine value is represented by the number of mg of potassium hydroxide equivalent to the amount of hydrochloric acid necessary to neutralize 1 g of the binder. The amine value is preferably 0 or more, preferably 60 or less, more preferably 50 or less, and still more preferably 40 or less. By controlling the amine value within the above range, the green sheet can be made more flexible and easily peeled from the PET film. The amine value can usually be measured by a titration method.

  The hydroxyl value is represented by the number of mg of potassium hydroxide necessary for acetylating the hydroxyl group contained in 1 g of the binder. The hydroxyl value is preferably 0 or more, preferably 60 or less, more preferably 40 or less, further preferably 30 or less, and further preferably 20 or less. By controlling the hydroxyl value within the above range, a uniform slurry can be easily obtained. The hydroxyl value can be usually measured by a titration method.

  When the binder is dissolved in the solvent, the acid value, amine value, and hydroxyl value of the binder in the present invention are numerical values converted per solid content.

  Although the usage-amount of a binder should just be adjusted suitably, about 2 mass parts or more and about 40 mass parts or less are preferable with respect to 100 mass parts of scandia stabilization zirconia particles. If the said ratio is 2 mass parts or more, a green sheet can be produced by combining scandia-stabilized zirconia particles. On the other hand, since the binder is removed by firing, the ratio is preferably limited to 40 parts by mass or less. The proportion is more preferably 5 parts by mass or more and 30 parts by mass or less, and particularly preferably 10 parts by mass or more and 20 parts by mass or less. In particular, by setting the ratio to 20 parts by mass or less, the green sheet can have a relatively high hardness, and generation of undulation during firing can be suppressed.

  The plasticizer used in the present invention is added to impart flexibility to the ceramic green sheet.

  Examples of the plasticizer include a low molecular plasticizer, a co-oligomer plasticizer, and a high molecular plasticizer. Examples of the low molecular plasticizer include phthalic acid esters such as dibutyl phthalate and dioctyl phthalate.

Examples of the co-oligomer plasticizer and the polymer plasticizer include polyesters, and a compound represented by the following general formula (1) is particularly preferable.
R- (A-G) _n- A-R (1)
[In the formula, A represents a dibasic acid residue, R represents a monohydric alcohol residue, G represents a glycol residue, and n represents the degree of polymerization.]

  Here, examples of the dibasic acid include phthalic acid, adipic acid, and sebacic acid. Examples of the monohydric alcohol include methanol, propanol, butanol, neopentyl alcohol, tridecyl alcohol, isononyl alcohol, 2-ethylhexyl alcohol and the like. Examples of glycols include 1,4-butanediol, 1,3-propylene glycol, ethylene glycol, 1,6-hexanediol, 2-methyl-1,3-propylene glycol, neopentyl glycol, and other glycols; Glycol ethers; and polyethylene glycol derivatives. The degree of polymerization is preferably adjusted so that the number average molecular weight of the plasticizer is 500 or more and 8000 or less.

  As the plasticizer used in the method of the present invention, an oligomer plasticizer having a number average molecular weight of 500 or more and 8000 or less is particularly suitable. Generally, the green sheet is wound up in a long length and stored before cutting and firing. At that time, a relatively low-molecular plasticizer may float on the surface of the sheet, and this may cause shine on a part of the surface of the sheet. Therefore, in the method of the present invention, an oligomer plasticizer having a number average molecular weight of 500 or more is used. On the other hand, if the number average molecular weight is too large, the number average molecular weight is preferably 8000 or less because it may not be able to dissolve quickly in the solvent or the viscosity of the slurry may become too high.

  The blending amount of the plasticizer is preferably 0.5 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the scandia-stabilized zirconia particles, although it depends on the glass transition temperature of the binder to be used. This is because if the ratio is less than 0.5 parts by mass, sufficient effects may not be exhibited. On the other hand, if it exceeds 10 parts by mass, the plasticity becomes too strong, and thermal decomposition at the time of firing is also caused. This is because it can have an adverse effect. More preferably, they are 2 mass parts or more and 8 mass parts or less, Most preferably, they are 2 mass parts or more and 6 mass parts or less.

  In preparing the slurry, a dispersant may be added to promote peptization and dispersion of the zirconia raw material powder, increase the fluidity of the slurry, and suppress sedimentation of the zirconia raw material powder in the slurry. Examples of the dispersant include anionic dispersants such as KD-4, 9 manufactured by Uniqema, Floren G700 and G900 manufactured by Kyoei Chemical Industry, BYK-220S manufactured by BYK Chemie, and KD-1 manufactured by Uniqema. Cationic dispersants such as DOPA-22, Disperbyk 108, 112, 116 manufactured by Big Chemie; Nonionic dispersants such as Naraxel FM-1D manufactured by Daicel, B246SF manufactured by Uniqema, NC-500 manufactured by Kyoei Chemical Co., Ltd. Can be mentioned. Furthermore, a surfactant, an antifoaming agent, etc. can be added as needed. It is desirable that the amount of water in the slurry is as small as possible.

The average secondary particle diameter (D ₅₀ ) of the scandia-stabilized zirconia particles in the slurry according to the present invention is preferably 0.08 μm or more and 0.8 μm or less. By using relatively fine scandia-stabilized zirconia particles having an average secondary particle size of 0.8 μm or less, the amount of binder used can be reduced, and a green sheet with high hardness can be obtained. As a result, a zirconia sheet with less undulation Is obtained. On the other hand, if it is too fine, the necessary amount of a dispersant and the like increases, so that it is preferably 0.08 μm or more. The average secondary particle diameter is more preferably about 0.2 μm or more and 0.5 μm or less.

In addition, the average secondary particle diameter (D ₅₀ ) of the solid matter in the slurry is preferably 0.08 μm or more and 0.8 μm or less, more preferably 0.2 μm or more and 0.5 μm or less. The volume% diameter (D ₉₀ ) is 2 μm or less, more preferably 0.8 μm or more and 1.5 μm or less. When a slurry having such a particle size structure is used, fine and uniform pores are easily formed between solid particles in the drying step after forming into a sheet shape, and coarse pores are combined with moderate pressure. The fine pores disappear by sintering and become a high-density sintered body. In addition, the coefficient of variation of the crystal grain size is suppressed as small as possible, and as a result, a sintered body sheet having a high level of fracture toughness value and a small coefficient of variation can be obtained.

  The particle size of the solid component in the slurry may be controlled before mixing and may be mixed as it is with a ball mill or the like. In addition, before mixing with a ball mill or the like, at least a dispersant, a solvent, and scandia-stabilized zirconia particles may be preliminarily dispersed with a disper or the like and then mixed while being pulverized with a ball mill or the like to obtain a desired particle size.

The particle size constitution of the solid component in the raw material powder or slurry refers to a value measured by the following method. As the measuring device, a particle size distribution measuring device such as a laser diffraction particle size distribution measuring device “LA-920” manufactured by HORIBA, Ltd. is used. The particle size composition of the raw material powder is as follows. First, an aqueous solution obtained by adding 0.2% by mass of sodium metaphosphate in distilled water is used as a dispersion medium, and 0.01 to 1% by mass of the raw material powder is added to 100 mL of the dispersion medium for 3 minutes. Sonicate and disperse and measure. Moreover, the particle size constitution of the solid component in the slurry uses a solvent having the same composition as the solvent in the slurry as a dispersion medium, and adds each slurry to 0.01 to 1% by mass in 100 mL of the dispersion medium, Similarly, it is a measured value after being sonicated for 3 minutes and dispersed. The average secondary particle size (D ₅₀ ) is the particle size when it corresponds to 50% of the total solid content in the particle size distribution curve, and the 90 volume% size (D ₉₀ ) is the particle size distribution curve. Is the particle size when it corresponds to 90% from the fine particle side in the total volume of solid content.

(2) Green sheet forming step Next, the obtained slurry is formed into a sheet. The molding method is not particularly limited, and a conventional method such as a doctor blade method or a calendar roll method is used. Specifically, the raw material slurry is transported to a coating dam, cast on a polymer film so as to have a uniform thickness by a doctor blade, and dried to obtain a green sheet.

  An object of the present invention is to obtain a zirconia sheet having a thickness of more than 100 μm and not more than 300 μm. Accordingly, the thickness of the green sheet after drying is preferably about 100 μm or more and 500 μm or less, more preferably about 110 μm or more and 400 μm or less in consideration of the sheet thickness after the firing step.

  The shape and size of the green sheet may be determined according to the desired shape and size of the zirconia sheet, but it is usually a long length of about 5 cm to 200 cm.

  The green sheet drying conditions may be adjusted as appropriate according to the type of solvent used, but are usually 40 ° C. or higher, more preferably 80 ° C. or higher and about 120 ° C. or lower. Drying may be performed at a constant temperature, or may be performed by heating by successively raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C.

  In the present invention, the drying temperature of the zirconia sheet is particularly preferably 80 ° C. or higher. By drying at a relatively high temperature, a green sheet with high hardness can be obtained, and finally, a zirconia sheet with little undulation can be produced even after firing. On the other hand, if the drying temperature is too high, the green sheet may become too hard, or the polymer film may be deformed to cause an abnormal appearance of the zirconia sheet.

  The obtained green sheet may be further cut into a desired shape and size, but is usually wound up in a long form and stored once. In the method of the present invention, it is preferable to store the green sheet at a temperature of normal temperature to 50 ° C. for 2 weeks or more and 3 months or less before firing. The reason is not clear, but when the green sheet is stored for 2 weeks or more and then fired, undulation after firing is clearly suppressed. Although there is no particular condition for such a storage period, it is preferably within 3 months from the viewpoint of productivity. Further, if the storage temperature is too high, for example, even if a co-oligomer plasticizer or a polymer plasticizer is used, bleeding occurs and causes shine. Therefore, the storage temperature is preferably 50 ° C. or lower, more preferably 40 ° C. or lower. 30 ° C. or lower is more preferable. Moreover, you may preserve | save at normal temperature. Here, shine is a phenomenon in which part of the surface of the green sheet becomes more glossy than the other part, and when such a green sheet is baked into a zirconia sheet, a pattern appears on the surface and the appearance deteriorates. Say. The green sheet may be stored as it is long or after it has been cut into a desired shape, but it is preferable to store the green sheet as it is due to the problem of storage space.

  Preferably, the green sheet is stored in a long shape and then cut into a desired shape. Specifically, for example, the Thomson blade body portion embedded in a green sheet punch has a shore strength of 40 or more and 70 or less, and / or the edge shore portion has a shore strength of 70 or more and 80 or less. Or a green sheet cutting mold. The shape of the sheet is not particularly limited, and may be any of a circle, an ellipse, a square with R (R), etc., and the sheet has holes such as a circle, an ellipse, and a square with R. May be.

In addition, as an example of the mold for cutting the green sheet, there are four molds including an upper center mold, a lower center mold, an upper square mold, and a lower square mold. The thing which consists of a combination can be mentioned. In this example, the green sheet is fixed by the upper center mold and the lower center mold. Next, the upper B-shaped mold is lowered, and this cuts the green sheet, and at the same time, the lower B-shaped mold descends in conjunction with it. Next, the upper and lower B-shaped molds and the upper center mold rise, and the green sheet whose peripheral edge is cut by the B-shaped molds is sent to the next process by hand or a robot arm. The cut peripheral edge is removed by continuous winding. The material used for the cutting surface of the cutting die is not particularly limited, but in view of durability, die steel, high-speed steel, more preferably cemented carbide is used. In addition, the cutting die is provided with one or more air ejection holes, and after the cutting processing into a desired shape, air is fed from the air ejection holes to easily peel the die from the green sheet having the desired shape. Can do. The diameter of the air ejection holes provided in the cutting mold is about 0.1 mm or more and 1 mm or less, the number of air ejection holes is 1 or more and 80 or less, and the pressure of the air fed from the air ejection holes is , 0.1 kgf / cm ² or more, by a 1 kgf / cm ² or less, can be favorably peeled and cut mold and green sheet. The shape of the mold may be any of a circle, an ellipse, a square with R (R) according to the desired cutting shape of the green sheet, and a circle, an ellipse, a square with R (R) in these sheets, etc. A cutting die for forming a hole may be used.

  The present invention provides a green sheet having a maximum stress of 5.0 MPa or more and 20.0 MPa or less during a tensile test and an elongation rate of 5.0% or more and less than 20.0% when the maximum stress is applied. And According to the experimental facts found by the present inventors, when the green sheet within the range in which the maximum stress and the elongation rate at the maximum stress load are within the range is fired to form a scandia-stabilized zirconia sheet, the undulation is clearly Reduced. The reason for this is not necessarily clear, but if the maximum stress of the green sheet and the elongation at the maximum stress load are within this range, the shrinkage of the green sheet due to degreasing will be uniform, and further when cutting or handling the green sheet It is considered that the undulation is suppressed because the residual stress at is reduced.

  From the viewpoint of reducing undulation, it is advantageous that the green sheet is harder, that is, the maximum stress is larger than the above range and the elongation at the time of the maximum stress load is smaller. However, the sheet becomes brittle and frequent birds are generated. Can do. Further, when the green sheet is softer, that is, when the maximum stress is smaller than the above range and the elongation at the time of the maximum stress load is further larger, undulation is frequently generated. On the other hand, assuming that the residual stress at the time of cutting is the cause of undulation, if the stress and elongation at the yield point are appropriate, the stress at the time of cutting will be difficult to appear as undulation, and the degreasing process It is thought that the shrinkage of the green sheet when the organic matter decomposes becomes uniform, and undulation is difficult to occur.

  In order to measure the maximum stress and the elongation at the time of the maximum stress load, first, a tensile stress is applied to the green sheet sample using a tensile tester, and the SS curve (stress) is measured by measuring the stress and strain. And a graph showing the relationship between strain and strain. Next, from the obtained SS curve, the maximum stress that is applied until the green sheet sample breaks is the maximum stress, and the elongation rate of the green sheet sample at the point where the maximum stress is applied is the elongation rate at the maximum stress load. Ask.

  In the present invention, when the elongation rate at the maximum stress load is x% and the maximum stress is yMPa, the green satisfies the relationship of 7 ≦ x <20, y ≦ −0.25x + 14, and y ≧ −0.25x + 10. It is particularly preferable to produce a sheet. A green sheet satisfying such requirements can remarkably suppress the occurrence rate of undulation, and has flexibility and strength that are very easy to handle in operations involving punching and firing.

  The maximum stress of the green sheet and the elongation at the maximum stress load depend on the drying temperature of the green sheet, binder content, average secondary particle size of scandia-stabilized zirconia particles, storage time, plasticizer content, solvent content, etc. Can be controlled.

  More specifically, when the drying temperature is increased, the maximum stress increases, and the elongation at the time of maximum stress load decreases. However, if the drying temperature is too high, the organic film may be decomposed or the resin film may be deformed during coating. When the binder content is reduced, the maximum stress increases and the elongation at the maximum stress load decreases. When the average secondary particle diameter of the zirconia particles is reduced, the maximum stress increases and the elongation at the maximum stress load decreases. Moreover, although the amount of required binder can be reduced, when the said particle diameter is too small, slurry viscosity will become high too much and the handleability of a slurry will worsen. If the amount of the solvent is increased in order to solve such a problem, the drying time must be lengthened. Further, the longer the storage time of the green sheet, the greater the maximum stress.

  When the plasticizer content is reduced, the maximum stress increases and the elongation at the maximum stress load decreases. Further, when the solvent content is reduced, the maximum stress increases and the elongation at the maximum stress load decreases.

  As described above, the maximum stress of the green sheet and the elongation at the time of maximum stress loading can be adjusted by the drying temperature of the green sheet, etc., but the above adjustment factors may be related to each other. And the quality of the zirconia sheet. Therefore, in the present invention, preliminary experiments and small-scale production and measurement of the maximum stress of the green sheet and the elongation at the maximum stress load are repeated, and the conditions such as the drying time are adjusted as described above to obtain the desired maximum What is necessary is just to determine the conditions which can obtain the green sheet which shows the elongation rate at the time of stress and the maximum stress load.

(3) Firing step Next, the obtained green sheet is fired to obtain a zirconia sheet having a thickness of more than 100 μm and not more than 300 μm.

  Firing conditions may be adjusted as appropriate. For example, firing is performed at 1200 ° C. or higher and 1500 ° C. or lower. If fired at 1200 ° C. or higher, a sufficient firing effect is obtained, and a tough zirconia sheet is obtained. However, if the firing temperature is too high, the crystal grain size of the sheet becomes excessive and the toughness may be reduced, so the upper limit is set to 1500 ° C.

  The heating rate up to the firing temperature may be adjusted as appropriate, but can usually be about 0.05 ° C./min to 4 ° C./min.

  Preferably, it is held at a firing temperature range of 1200 ° C. or more and 1500 ° C. or less, and is held at a temperature 20 ° C. or more and 100 ° C. or less lower than the sintering temperature. The holding time is preferably about 10 minutes to 5 hours. Under the conditions, the temperature distribution in the firing furnace becomes small, and the sinterability of the sheet becomes uniform. As a result, the sintered density becomes uniform, and the difference in the fracture toughness value depending on the position inside the sheet and the coefficient of variation thereof are suppressed.

  Furthermore, in the present invention, in order to suppress the coefficient of variation of the fracture toughness value of the sheet, the temperature distribution in the firing furnace is preferably adjusted to ± 15% or less, and more preferably ± 10% or less.

  In the zirconia sheet obtained by the method of the present invention, undulation is suppressed. For example, even if undulation is present, the generation rate can be reduced to 30% or less. Therefore, since the location where the stress generated by the load generated when the cells are stacked and the volume change during power generation is concentrated is reduced, the solid oxide form using the scandia-stabilized zirconia sheet according to the present invention as the solid electrolyte membrane Fuel cells have a long life.

  In the present invention, the term “unery” means that the unevenness in the height direction of the end of the scandia-stabilized zirconia sheet (the portion corresponding to the side in the case of a rectangle) is continuous in two or more locations in the concave direction or in two or more locations in the convex direction. It is assumed that the maximum height difference is more than 20 μm. The height difference can be measured with a laser displacement meter.

  In order to produce a solid oxide fuel cell using the scandia-stabilized zirconia sheet according to the present invention as a solid electrolyte membrane, a conventional method may be used. A brief description is given below.

(4) Formation of intermediate layer An intermediate layer may be formed on the scandia-stabilized zirconia sheet obtained above. The intermediate layer is formed particularly for suppressing the reaction between the solid electrolyte membrane and the air electrode. Examples of components of the air electrode include ceria doped with one or more metals selected from the group consisting of Y, Sm, Gd, Nd, Pr, Sc, Ga, and Al. Is Ce _1-z M _z O _2-w (wherein, M represents one or more metals selected from the group consisting of Y, Sm, Gd, Nd, Pr, Sc, Ga, Al; 0.05 ≦ z ≦ 0.4; 0 ≦ w <0.5)).

  The intermediate layer may be formed by a conventional method. For example, a binder, a solvent, a plasticizer, and a dispersant, an antifoaming agent, a surfactant, a bonding aid, an antifoaming agent, a leveling improver, a rheology adjusting agent, etc. In addition, a paste is prepared by mixing. The viscosity of the obtained paste may be adjusted so as to be suitable for printing. After the viscosity is adjusted, for example, it is coated on the solid electrolyte by a bar coater, a spin coater, a dipping device or the like, or formed into a thin film by a screen printing method, and then a temperature of 40 to 150 ° C., for example, 50 ° C., 80 C., 120.degree. C., or successively heated up and dried by heating. Next, the intermediate layer may be baked at a temperature of 900 to 1300 ° C., preferably 950 to 1250 ° C., more preferably 1000 to 1200 ° C.

(5) Formation of fuel electrode A fuel electrode is formed on the surface on which the intermediate layer of the scandia-stabilized zirconia sheet according to the present invention is formed or on the surface opposite to the surface to be formed. The order of formation of the intermediate layer and the fuel electrode is not particularly limited, and the intermediate layer and the fuel electrode are formed by applying and drying the intermediate layer paste and the fuel electrode paste on each surface of the solid electrolyte membrane, followed by sintering. May be formed simultaneously.

  Examples of the material of the fuel electrode include ceria doped with NiO and at least one oxide of an element selected from yttrium, samarium, and gadolinium, and / or an oxide of an element selected from yttrium, scandium, and ytterbium. And zirconia stabilized with at least one of the above. More specific fuel electrode materials include, for example, a mixed powder of NiO: 50 to 70% by mass and 10 mol% scandia 1 mol% ceria stabilized zirconia: 30 to 50% by mass.

  The fuel electrode paste may be kneaded by adding the above materials to a solvent together with a binder or the like. Moreover, you may add a plasticizer, a dispersing agent, a pore making agent, etc. to a fuel electrode paste as needed.

  The fuel electrode paste application method, drying conditions, firing conditions, and the like can be implemented in the same manner as in the intermediate layer forming step.

(6) Formation of air electrode After forming an intermediate | middle layer and a fuel electrode in each surface of a solid electrolyte membrane, it is set as a cell by apply | coating and drying an air electrode paste on the said intermediate | middle layer, and baking.

As an air electrode material, a material made of a perovskite oxide which is excellent in electronic conductivity and stable even in an oxidizing atmosphere is generally used. Specifically, La _0.8 Sr _0.2 MnO ₃ , La _0.6 Sr _0.4 CoO ₃ , La _0.6 Sr _0.4 FeO ₃ , La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O _3, etc., lanthanum manganite in which part of lanthanum is substituted with strontium Lanthanum ferrite, lanthanum cobaltite and the like are preferable as the air electrode material. In addition, in order to impart oxygen ion conductivity to the air electrode, ceria doped with rare earth or the like can be appropriately mixed.

  Similarly to the intermediate layer paste, the air electrode paste can be prepared by adding the above materials to a solvent together with a binder and the like, and further adding a dispersant as necessary. Furthermore, the air electrode paste application method, drying conditions, firing conditions, and the like can be implemented in the same manner as in the intermediate layer forming step.

  Cells manufactured as described above can be laminated by a conventional method to obtain a solid oxide fuel cell. At this time, the scandia-stabilized zirconia sheet obtained by the method of the present invention has a reduced rate of undulation, reducing the concentration of stress caused by the load generated when the cells are stacked and the volume change during power generation. Therefore, the solid oxide fuel cell using the zirconia sheet according to the present invention as a solid electrolyte membrane has a long life.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Examples 1 to 9, Reference Example, Examples 11 to 16, and Comparative Example 1
Slurries were prepared with the compositions shown in Tables 1 to 3. The plasticizer other than P is a polyester obtained by polymerizing a dibasic acid and a diol and esterifying a terminal with a monohydric alcohol. The values in Table 2 are mol%.

The obtained slurry was applied onto a PET film by a doctor blade method and dried at 96 ° C. to obtain a long green sheet having a thickness of 270 μm and a width of 160 mm. Only the reference example was dried in two stages of 76 ° C. and 96 ° C. Further, in Examples 11 to 13, the sample was stored at 25 ° C. for 1 day, 2 weeks, and 10 weeks before being dried and then fired.

Using a super dumbbell cutter SDK-200, which is an SD-type lever type sample cutter made by Dumbbell, a test piece having the following size was obtained from each long green sheet, and the SS curve was measured under the following conditions.
Measuring instrument: manufactured by Instron Japan Co., Ltd., universal material testing machine type 4301 Measurement temperature: 23 ° C
Humidity during measurement: 60%
Test piece: Sample length: 100 mm, parallel part (maximum detail width): 10 mm, grip part width: 25 mm
Gripper spacing: 70mm
Tensile speed: 10 mm / min

  The green sheet was placed in the test room for 1 hour or more before measurement to adjust the temperature and humidity. From the obtained SS curve, the maximum stress applied until the green sheet sample broke was determined as the maximum stress, and the elongation rate of the green sheet sample at the point where the maximum stress was applied was determined as the elongation rate at the maximum stress load. .

  Further, 100 green sheets each having a size of 135 mm × 135 mm were cut out from each long green sheet using a cutting die, and fired at 1400 ° C. for 3 hours to obtain a scandia-stabilized zirconia sheet. By touching the edges of each zirconia sheet with the hand and observing it visually, and measuring the height difference with a displacement meter, the number of zirconia sheets in which undulation with an elevation difference of 20 μm or more is obtained is obtained. Calculated. Table 4 shows the maximum stress of each green sheet, the elongation at the time of maximum stress loading, and the occurrence rate of undulation.

  As in Examples 1 to 7, by changing the type and amount of the plasticizer, the maximum stress and the elongation at the time of the maximum stress load could be adjusted within the specified range of the present invention.

  A comparison between Example 8 and Example 9 shows that when raw material zirconia particles having a small average secondary particle diameter are used, the required amount of binder can be reduced, and the maximum stress is large and the green sheet has a small elongation at the maximum stress load. Was found to be obtained.

A comparison between Example 8 and the reference example showed that a green sheet having a large maximum stress and a small elongation at the maximum stress load can be obtained by adjusting the drying temperature of the green sheet.

  As shown in Examples 11 to 13, when the green sheet was stored after being dried and then fired, it was found that the longer the storage period, the larger the maximum stress and the smaller the elongation at the maximum stress load.

  As in Examples 14 to 15, it was found that when the amount of the binder was decreased, the maximum stress was increased and the elongation at the maximum stress load was decreased.

Examples 1 9, when comparing the Reference Example and Examples 11 to 15 and Example 16, the shine on the part of the low molecular weight plasticizer Example 16 In a green sheet of zirconia sheet surface using occur On the other hand, no shine was generated in Examples 1 to 9, Reference Example and Examples 11 to 15 using a co-oligomer plasticizer.

Moreover, in Comparative Example 1 in which the elongation rate at the maximum stress load of the green sheet was larger than the range of the present invention, the undulation rate of the zirconia sheet by firing exceeded 30%. On the other hand, in Examples 1 to 9 and Examples 11 to 16 in which the maximum stress and the elongation at the time of the maximum stress load are within the scope of the present invention, the undulation rate could be remarkably reduced. As described above, it was proved that the method of the present invention is very useful as contributing to mass production of a scandia-stabilized zirconia sheet useful as a solid electrolyte membrane of a solid oxide fuel cell.

Examples 17-19 and Comparative Examples 2-4
In Example 1 above, the stabilized zirconia sheet was prepared in the same manner except that the type and ratio of the zirconia stabilizer was changed as shown in Table 5 and the amount of the binder was adjusted as necessary. The strength was measured as follows.

Measurement of electric conductivity The electric conductivity of each stabilized zirconia sheet was measured by a DC four-terminal method. That is, each zirconia sheet was cut into a width of about 5 mm and a length of about 4 cm with a high-speed cutter, applied with a platinum paste at positions 1.5 cm on both sides from the center in the length direction, dried at 100 ° C., and then from the center. Platinum wires were placed in the width direction at a total of four locations, 0.5 cm on both sides and 1.5 cm, and a weight of about 150 g was placed on the four platinum wires. Current was passed from a DC stabilized power supply adjusted to about 3 V using two ends of the platinum wire as current terminals. The middle two platinum wires were used as potential difference measuring terminals.

  The sheet was put into an electric furnace, heated to 1000 ° C. while flowing current, then held at 950 ° C. and 750 ° C. during cooling for 30 minutes, and when it was stable, the conductivity was measured for about 10 minutes. The average value was calculated from the numerical values.

Measurement of strength The strength of each stabilized zirconia sheet was measured by a three-point bending method. That is, each zirconia sheet was cut into a width of about 5 mm and a length of about 4 cm with a high-speed cutter. The obtained sample was placed on a three-point bending jig with a span of 20 mm, and a load was applied at a crosshead speed of 0.5 mm / min using a universal material testing machine model 4301 manufactured by Instron Japan. Recorded. From the obtained numerical value, the strength was determined according to JIS R1601. Table 5 shows the results.

  As shown in the above results, the scandia-stabilized zirconia sheet is relatively inferior in strength, but not so much when 4 mol% of scandia is included, but it is very excellent in conductivity when 6 mol% or more of scandia is included. I understood. Therefore, since the conductivity in such an experiment has a correlation with the oxygen ion conductivity, the scandia-stabilized zirconia sheet containing 5 mol% or more of scandia must be a relatively thick film in terms of strength, It was found to be useful as an electrolyte membrane for a fuel cell.

Examples 1 to 9, Reference Example, Examples 11 to 16, Examples 20 to 21, Comparative Example 1 and Comparative Examples 5 to 7
(1) Preparation of binders Monomers were copolymerized at the ratios shown in Table 6 to prepare binders V and W. The values in Table 6 are mol%.

(2) Measurement of acid value, amine value, hydroxyl value In addition to binders X to Z used in Examples 1 to 9, Reference Example, Examples 11 to 16 and Comparative Example 1, acid values of the binders V to W were used. The amine value and the hydroxyl value were measured by an indicator titration method. The results are shown in Table 7.

(3) Production of green sheet and measurement of physical properties (3-1) Example 20
A green sheet was produced in the same manner as in Example 1 except that the binder Y was used.

(3-2) Example 21
A green sheet was produced in the same manner as in Example 4 except that the binder Y was used.

(3-3) Comparative Example 5
A green sheet was produced in the same manner as in Example 6 except that the binder V was used and the binder amount was 18.5 parts by mass. However, after drying, it was torn when it was peeled off from the PET film and could not be made into a zirconia sheet. However, a test piece was cut out from a portion that was not torn, and the maximum stress of the green sheet and the elongation rate under the maximum stress load were measured.

(3-4) Comparative Example 6
In the above Comparative Example 5, the green sheet was prepared in the same manner except that the amount of the plasticizer was 9.0 parts by mass in order to make it easy to peel the green sheet from the PET film, and the maximum stress and the maximum stress load elongation were obtained. The rate of occurrence was measured, and the occurrence rate of ungeli in the zirconia sheet obtained by further firing was determined.

(3-5) Comparative Example 7
A slurry was prepared in the same manner as in Example 6 except that the binder W was used. However, the slurry was solidified in a gel state and did not become a uniform slurry.

The above results are shown in Table 8 together with the results of Examples 1 to 9, Reference Example, Examples 11 to 16, and Comparative Example 1 already shown.

  As described above, when a binder having an excessively high amine value is used, the flexibility of the green sheet is lowered and it is difficult to peel from the PET film. In that case, naturally the maximum stress at the time of a tensile test and the elongation rate at the time of a maximum stress load will become low. Therefore, if the amount of the plasticizer is increased in order to increase the flexibility, the flexibility becomes excessively high and the elongation rate at the maximum stress load becomes too large. On the other hand, when the acid value and the hydroxyl value of the binder are too large, the fluidity of the slurry is deteriorated, and a uniform slurry cannot be obtained.

  On the other hand, it became clear that when a binder having an appropriate acid value, amine value, and hydroxyl value was used, a slurry could be prepared well and the green sheet according to the present invention could be easily obtained.

Claims (11)

A method for producing a zirconia sheet for a solid oxide fuel cell, comprising:
A slurry containing scandia-stabilized zirconia particles is formed into a sheet and then dried. The maximum stress is 5.0 MPa or more and 20.0 MPa or less, and the elongation at the maximum stress load is 5.0% or more and 20.0%. A step of producing a green sheet that is less than the above; and a step of firing the obtained green sheet to obtain a zirconia sheet having a thickness of more than 100 μm and not more than 300 μm;
Only including,
In said green sheet preparation process, drying temperature shall be 80 degreeC or more and 120 degrees C or less, or the ratio of the binder to a slurry is 10 mass parts or more and 20 mass parts or less with respect to 100 mass parts of scandia stabilization zirconia particles. Or an average secondary particle size of scandia-stabilized zirconia particles in the slurry is 0.2 μm or more and 0.5 μm or less, or any one of the conditions is satisfied For producing a scandia-stabilized zirconia sheet for a fuel cell.   The method for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell according to claim 1, wherein an oligomer plasticizer having a number average molecular weight of 500 or more and 8000 or less is blended in the slurry.   3. The binder comprising an acrylate copolymer having an acid value of 0.1 or more and 60 or less, an amine value of 0 or more and 60 or less, and a hydroxyl value of 0 or more and 60 or less is blended in the slurry. Of producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell.   Claims for producing a green sheet satisfying the relationship of 7 ≦ x <20, y ≦ −0.25x + 14, and y ≧ −0.25x + 10, where x% is the elongation at maximum stress loading and yMPa is the maximum stress. Item 4. A process for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell according to any one of Items 1 to 3.   The method for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell according to any one of claims 1 to 4, wherein a scandia content in the scandia-stabilized zirconia particles is 5 mol% or more. The method for producing a scandia-stabilized zirconia sheet for a solid oxide fuel cell according to any one of claims 1 to 5 , wherein the green sheet is stored for 2 weeks or more before firing. A slurry used in the process according to any one of claims 1 to 6 and scandia-stabilized zirconia particles, the number average molecular weight of 500 or more, scandia-stabilized, characterized in that it comprises 8000 following oligomer plasticizer Zirconia slurry. The scandia-stable composition according to claim 7 , further comprising a binder comprising an acrylate copolymer having an acid value of 0.1 to 60, an amine value of 0 to 60, and a hydroxyl value of 0 to 60. Zirconia slurry. A scandia-stabilized zirconia green sheet obtained by molding and drying the scandia-stabilized zirconia slurry according to claim 7 or 8 , wherein the maximum stress is 5.0 MPa or more and 20.0 MPa or less and when the maximum stress is applied. The scandia-stabilized zirconia green sheet is characterized by having an elongation percentage of 5.0% or more and less than 20.0%. A solid oxide fuel cell scandia-stabilized zirconia sheet produced by the method according to any one of claims 1 to 6 , wherein a difference in the height of the undulation at the end is 20 µm or less. Scandia-stabilized zirconia sheet for oxide fuel cells. A solid oxide fuel cell comprising the scandia-stabilized zirconia sheet for a solid oxide fuel cell according to claim 10 as a solid electrolyte membrane.