JP2012074207A - Fuel cell electrolyte sheet manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell electrolyte sheet manufacturing method which makes it possible to restrict the breakage of a sheet, as well as to reduce undulation or a warp occurring in the sheet.SOLUTION: The manufacturing method of the prevent invention includes a process (I) in which a ceramic porous spacer and a zirconia based green sheet are alternately stacked on a ceramic setter, with the spacer disposed in the bottom and the top layers, to dispose a laminate composed of the spacer and the green sheet; a process (II) in which a weight is placed on the laminate so that a load on the green sheet will be 0.1 to 3.0 g/cm, and the laminate is calcined at 1000 to 1300°C to prepare an electrolyte sheet precursor, and a process (III) in which, following the process (II), a weight is placed on the laminate so that a load on the electrotype sheet precursor will be 3.0 to 80.0 g/cm, and the electrotype sheet precursor is calcined at 1350 to 1500°C.

Description

  The present invention relates to an electrolyte sheet for a fuel cell, and more particularly to a method for producing an electrolyte sheet for a solid oxide fuel cell.

  In recent years, fuel cells have attracted attention as clean energy sources. Among fuel cells, solid oxide fuel cells that use solid ceramics as an electrolyte have advantages such as being able to use exhaust heat because of the high operating temperature, and obtaining power with high efficiency. It is expected to be used in a wide range of fields from household power supplies to large-scale power generation.

  A cell of a solid oxide fuel cell has a basic structure in which an electrolyte made of ceramic is disposed between a cathode (air electrode) and an anode (fuel electrode). For example, in a flat solid oxide fuel cell, a single cell is formed by superposing a cathode, an electrolyte sheet, and an anode, and a high output is obtained by stacking a plurality of single cells with an interconnector interposed therebetween. Thus, in the case of a structure in which a plurality of cathodes, electrolyte sheets, and anodes are stacked, the electrolyte sheet is required to have high flatness in order to prevent damage such as cracking of the electrolyte sheet.

  Zirconia-based ceramic materials such as yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) are preferably used for the electrolyte of the solid oxide fuel cell. Therefore, in order to obtain an electrolyte sheet, it is necessary to manufacture a highly flat sheet made of these zirconia ceramic materials.

  A sheet made of a ceramic material (ceramic sheet) is usually formed into a green sheet by forming a slurry obtained by mixing and pulverizing ceramic raw material powder, a binder, a solvent and the like into a sheet shape by a doctor blade method or the like. It can be produced by firing the sheet.

  However, the ceramic sheet obtained by such a method is prone to swell and warp, and there is a problem that it is difficult to obtain a highly flat sheet. Here, “swell” means two or more continuous mountain-shaped deformations (local deformation of the sheet) existing at the peripheral edge of the sheet, and “warp” means that the peripheral edge of the sheet warps. It is a deformation of the entire raised arcuate sheet. Hereinafter, in this specification, “swell” and “warp” are used in the same meaning.

  Conventionally, various techniques for suppressing the occurrence of waviness and warpage of a ceramic sheet have been proposed.

  For example, Patent Document 1 discloses a method in which main firing of a ceramic green sheet is performed at a temperature of 1600 to 1800 ° C., and then warp correction firing is performed at a temperature of 1400 to 1500 ° C. on a sintered sheet in which warpage has occurred. Has been.

  In Patent Document 2, a ceramic green sheet is sandwiched between a plurality of fire-resistant plates having a smooth surface and pre-fired at a temperature of 400 to 1000 ° C., and then the pre-fired sheet is formed into a plurality of fire-resistant plates. A method of firing at a temperature exceeding 1000 ° C. after removal from the steel is disclosed.

  In Patent Document 3, only ceramic green sheets are stacked in multiple stages and fired at a temperature lower than a predetermined temperature (original firing temperature), and then the obtained ceramic substrates are alternately stacked with setters and stacked in multiple stages. A method of firing at the predetermined temperature is disclosed.

In the method for producing a sheet-like zirconia sintered body disclosed in Patent Document 4, this green sheet is fired in a state where a weight is applied to the zirconia green sheet using a weight. At this time, the weight per unit area of the weight is W (g / cm ² ), the area of each weight is S (cm ² ), and the load applied per unit area of the green sheet is G (g / Cm ² ), S ≦ 200, G ≦ 5, and W / G ≧ 0.5.

In Patent Document 5, ceramic green sheets and ceramic porous spacers are alternately stacked on a ceramic setter to form a laminated body, and a static bending elastic modulus of 5 to 15 MPa is applied to the top of the laminated body as a weight. Porous firing jig whose material is alumina, zirconia, mullite and / or cordierite, bulk ratio 0.8-2, air permeability 0.01-0.1 cm ² , porosity 50-75% A method for producing a ceramic sheet is disclosed in which a ceramic sheet is placed and fired.

JP-A-5-136544 JP-A 63-295480 Japanese Patent Laid-Open No. 2-311370 JP-A-6-9268 JP 2007-302515 A

  However, in the method of firing in two stages as disclosed in Patent Documents 1 to 3, the effect of suppressing the occurrence of waviness and warpage was insufficient. For example, in the case of the method disclosed in Patent Document 1 in which correction firing is performed on a sintered sheet having warpage, it is very difficult to correct the warpage once generated in the sintered sheet by further firing. There is a problem that it is difficult, for example, it takes a long time for correction baking.

  Further, in the method of firing while applying a load as disclosed in Patent Documents 4 and 5, if a load is applied excessively in order to further reduce the occurrence of waviness and warpage, the sheet is cracked or cracked. Since the problem of entering would occur, it was difficult to further reduce waviness and warpage.

  Therefore, there is a demand for a method for manufacturing a ceramic sheet that can further reduce the occurrence of swell and warpage. In particular, since the electrolyte sheet used in the solid oxide fuel cell is made of a high-priced material such as ScSZ, it is necessary to further reduce the occurrence of swell and warp in order to reduce the cost.

  This invention makes it a subject to provide the manufacturing method of the electrolyte sheet for fuel cells which can reduce the wave | undulation and curvature which generate | occur | produce in a sheet | seat compared with the case where the conventional method is used, suppressing the breakage | damage of a sheet | seat.

  In order to solve the above-mentioned problems, the present inventor has studied the swell and warp generated in the electrolyte sheet, and the swell and warp (especially swell) are more than this when firing at the original firing temperature of the ceramic. It is easy to occur when heat treatment is performed in a temperature range lower than the temperature (for example, during the degreasing process of the green sheet), and further find out how to apply an effective load for reducing waviness and warpage. The production method was completed.

The method for producing an electrolyte sheet for a fuel cell according to the present invention includes:
(I) On the ceramic setter, the ceramic porous spacer and the zirconia green sheet are alternately stacked so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the ceramic porous spacer and the green sheet are stacked. A step of arranging a laminate comprising:
(II) On the ceramic porous spacer disposed in the uppermost layer of the laminate so that the load applied to the green sheet in the laminate is in the range of 0.1 to 3.0 g / cm ^2. Placing a weight, and firing the green sheet in the laminate at a temperature of 1000 to 1300 ° C. to produce an electrolyte sheet precursor;
(III) After the step (II), on the uppermost layer of the laminate so that the load applied to the electrolyte sheet precursor in the laminate is in the range of 3.0 to 80.0 g / cm ^2. Placing a weight on the disposed ceramic porous spacer and firing the electrolyte sheet precursor in the laminate at a temperature of 1350-1500 ° C .;
including.

  According to the method for producing an electrolyte sheet for a fuel cell of the present invention, it is possible to reduce waviness and warpage generated in the sheet as compared with the conventional method while suppressing damage to the sheet. That is, according to the method for producing an electrolyte sheet for fuel cells of the present invention, a high-quality electrolyte sheet can be provided while maintaining high productivity.

  Hereinafter, embodiments of the present invention will be specifically described.

The manufacturing method of the fuel cell electrolyte sheet in the present embodiment,
(I) On the ceramic setter, the ceramic porous spacer and the zirconia green sheet are alternately stacked so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the ceramic porous spacer and the green sheet are stacked. A step of arranging a laminate comprising:
(II) On the ceramic porous spacer disposed in the uppermost layer of the laminate so that the load applied to the green sheet in the laminate is in the range of 0.1 to 3.0 g / cm ^2. Placing a weight, and firing the green sheet in the laminate at a temperature of 1000 to 1300 ° C. to produce an electrolyte sheet precursor;
(III) After the step (II), on the uppermost layer of the laminate so that the load applied to the electrolyte sheet precursor in the laminate is in the range of 3.0 to 80.0 g / cm ^2. Placing a weight on the disposed ceramic porous spacer and firing the electrolyte sheet precursor in the laminate at a temperature of 1350-1500 ° C .;
including. Note that firing at a temperature of 1000 to 1300 ° C. in step (II) means that the maximum temperature during firing is in the range of 1000 to 1300 ° C., and at a temperature of 1350 to 1500 ° C. in step (III). Firing means that the maximum temperature during firing is in the range of 1350-1500 ° C.

First, the zirconia green sheet used in step (I) will be described. The zirconia green sheet used in the manufacturing method of the present embodiment is, for example, a binder and a solvent are added to the zirconia raw material powder, and a dispersant, a plasticizer, a lubricant, an antifoaming agent, etc. are added as necessary. It can be obtained by adding to prepare a slurry, molding the slurry into a sheet and drying. Examples of the zirconia-based raw material powder include alkaline earth metal oxides such as MgO, CaO, SrO and BaO; Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ and Nd ₂ O _3. Rare earth element oxides such as 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 and Yb ₂ O ₃ ; and Bi Examples thereof include zirconia powder containing one or more selected from oxides such as ₂ O ₃ and In ₂ O ₃ as a stabilizer. Further, as other additives, any oxide selected from SiO ₂ , Ge ₂ O ₃ , B ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ and Nb ₂ O ₅ may be contained. Among these, in order to ensure a higher level of oxygen ion conductivity, strength and toughness, at least one selected from the group consisting of scandia, yttria, ceria and ytterbia is included as a stabilizer. , Stabilized zirconia. The content of the stabilizer in the entire stabilized zirconia is 4 to 12 mol% for scandia, 3 to 10 mol% for yttria, 0.5 to 2 mol% for ceria, and 4 to 15 mol% for ytterbia. The crystal system may be a tetragonal system or a cubic system, but in the case of zirconia containing scandia, if the scandia content increases, the crystal system may transition to rhombohedral crystals. In order to stabilize the crystal system into a cubic system, ceria, alumina or the like may be added as a third component. Hereinafter, for example, zirconia stabilized with 4 mol% of scandia (meaning “zirconia containing 4 mol% of scandia as a stabilizer”. Hereinafter, the same expression is used in the same sense.) 4ScSZ, 10 Zirconia stabilized with mol% scandia and 1 mol% ceria is denoted as 10Sc1CeSZ, and zirconia stabilized with 8 mol% yttria is denoted as 8YSZ.

  The zirconia green sheet used in the present embodiment is produced using the zirconia raw material powder as described above, and is at least one selected from the group consisting of scandia, yttria, ceria, and yttria. A zirconia-based sheet containing seeds is preferable. In addition, since the manufacturing method of the present embodiment is easier to obtain effects on zirconia-based green sheets containing scandia (easily reduces swell and warpage), scandia-stabilized zirconia powder and scandia-ceria stabilization Zirconia powder or the like is preferably used as the zirconia-based raw material powder. For example, scandia-stabilized zirconia has an electrolyte sheet density measured by the Archimedes method with respect to the theoretical density of 98% or more even when the maximum temperature during firing is 20 to 60 ° C. lower than yttria-stabilized zirconia. Tend to be almost equivalent. From this, it is judged that scandia-stabilized zirconia has characteristics that are more sensitive to heat and more reactive than yttria-stabilized zirconia. For these reasons, it is presumed that the zirconia green sheet containing scandia is likely to be corrected for waviness and warpage by firing in step (III) in the production method of the present embodiment.

  There is no restriction | limiting in the kind of binder used for preparation of a green sheet, It can select suitably from the organic binders well-known with the manufacturing method of the conventional electrolyte sheet. Organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl acetal resins, vinyl formal resins, polyvinyl Examples include butyral resin, vinyl alcohol resin, celluloses such as ethyl cellulose, and waxes. Among these, green acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, and 2-ethylhexyl from the viewpoints of green sheet moldability and strength, especially thermal decomposability when mass-fired for mass production. Alkyl acrylates having an alkyl group having 10 or less carbon atoms such as acrylates; 20 or less carbon atoms such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, lauryl methacrylate Alkyl methacrylates having the following alkyl groups: hydroxyethyl acrylate, hydroxypropyl acrylate Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as relate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate; (meth) acrylic acid A polymer obtained by polymerizing or copolymerizing at least one of monomers containing a carboxyl group such as maleic acid half ester such as maleic acid and monoisopropylmalate is preferably used.

  There is no restriction | limiting in the kind of solvent used for preparation of a green sheet, It can select suitably from the solvents well-known with the manufacturing method of the conventional electrolyte sheet. For example, alkyl alcohols having 2 to 4 carbon atoms such as ethanol, isopropanol and n-butanol; alcohols such as 1-hexanol; ketones such as acetone and 2-butanone; aliphatic hydrocarbons such as pentane, hexane and heptane Solvents appropriately selected from: aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; acetic esters such as methyl acetate, ethyl acetate and butyl acetate can be used. These solvents may be used alone or in combination of two or more.

  Dispersants, plasticizers, lubricants and antifoaming agents used as necessary include known dispersants, plasticizers, lubricants and antifoaming agents used in the production of electrolyte sheets by conventional production methods. , Can be used respectively.

A slurry prepared by mixing zirconia-based raw material powder, a binder, a solvent, and the like is formed into a sheet shape by a normal method, for example, a doctor blade method, an extrusion molding method, or a calendar roll method, and dried to a predetermined shape. By cutting into zirconia, a zirconia green sheet can be produced. The size and thickness of the green sheet are determined from the size and thickness of the target electrolyte sheet and the shrinkage rate due to firing. The green sheet used in the manufacturing method of the present embodiment is sized so that the finally obtained electrolyte sheet has an area of 50 to 1000 cm ² and a thickness of 0.05 to 0.5 mm. And having a thickness.

  The shape of the green sheet is not particularly limited because it may be appropriately determined according to the shape of the solid oxide fuel cell to which the electrolyte sheet is applied.

  On the ceramic setter, the ceramic porous spacer and the green sheet produced as described above are alternately stacked so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the ceramic porous spacer and the green are stacked. A laminate composed of a sheet is disposed. The number of green sheets to be stacked is, for example, 2 to 20 sheets, preferably 4 to 12 sheets, depending on the dimensions. As the ceramic setter and the ceramic porous spacer, known ceramic setters and ceramic porous spacers that are generally used when producing an electrolyte sheet can be used.

  The ceramic porous spacer used in the manufacturing method of the present embodiment is preferably made of a porous body containing at least one selected from the group consisting of alumina, zirconia and mullite. This is because they are excellent in creep resistance and spalling resistance and have low reactivity with zirconia in a high temperature atmosphere.

  The porosity of the ceramic porous spacer is preferably 30% or more and 70% or less. When the ceramic porous spacer has such a porosity, when firing the zirconia green sheet in a state where the ceramic porous spacer and the zirconia green sheet are alternately stacked, a binder, a plasticizer, a dispersant, etc. This is because the gas component produced by the thermal decomposition of the organic component can be promptly released to the outside and the degreasing effect can be promoted. When a porous spacer having a porosity of less than 30% is used, combustion of organic components and release of organic component decomposition gas become insufficient due to a decrease in air permeability, and even if a weight is placed on the laminate, the electrolyte The height of waviness and warpage generated in the sheet is large and large, which causes cracks and cracks. On the other hand, when a porous spacer having a porosity of more than 70% is used, combustion of the organic component and efficient release of the organic component decomposition gas are performed to reduce the occurrence of swell and warp. Since the strength is insufficient, the handling property is remarkably lowered and it cannot be used multiple times, and the smoothness of the surface of the porous spacer is also deteriorated so that the electrolyte sheet is likely to be cracked or cracked. Arise. A more preferable porosity of the porous spacer is 35% or more and 65% or less, and a more preferable porosity is 40% or more and 60% or less.

In addition, the porosity here is the porosity calculated | required based on "The measuring method of the apparent porosity of a refractory brick" of JISR2205. The apparent porosity (P ₀ ) of the sample is expressed by the following formula (1) from the mass of the dry sample (W ₁ ), the mass of the saturated sample in water (W ₂ ), and the mass of the saturated sample (W ₃ ). Calculated.
P ₀ = {(W ₃ −W ₁ ) / (W ₃ −W ₂ )} × 100 (1)

  Also, if the thickness of the porous spacer is less than 100 μm, the handling strength of the porous spacer itself is not sufficient even if the porosity is within the above preferred range, while if the thickness exceeds 500 μm, the handling strength is Although sufficient, the organic component decomposition gas from the zirconia green sheet is less likely to be efficiently diffused, and undulation and warpage are likely to occur in the electrolyte sheet. A more preferable thickness of the porous spacer is 120 μm or more and 400 μm or less, and a more preferable thickness is 150 μm or more and 350 μm or less.

  The area and shape of the porous spacer are determined based on the area and shape of the zirconia green sheet specified from the area and shape of the target electrolyte sheet. Accordingly, the shape of the porous spacer is preferably similar to the shape of the green sheet to be fired, and may be any of a circular shape, an elliptical shape, a square shape, a square shape having R (R), and the like. It may have a hole such as a circle, an ellipse, a square, or a square having R (R).

Since the zirconia green sheets are fired in a state where they are alternately stacked with the porous spacers, it is necessary to make the load applied to the zirconia green sheets uniform. For this purpose, it is preferable that the area of the porous spacer is slightly larger than the area of the zirconia green sheet and that the zirconia green sheet does not protrude from the periphery of the porous spacer. Specifically, the dimension in which the porous spacer protrudes from the periphery of the zirconia green sheet is preferably in the range of 0.5 to 5 mm, more preferably in the range of 1 to 3 mm, and particularly preferably in the range of 1 to 2 mm. Preferred areas of porous spacers therefor is a 80 cm ² or more 500 cm ² or less, and more preferably the area is a 100 cm ² or more 400 cm ² or less. In addition, the area of a porous spacer means the area (area determined by the external shape) of the porous spacer surface including the area of the said hole, when the hole is provided in the spacer.

  The ceramic setter used in the manufacturing method of the present embodiment is generally a ceramic firing jig mainly used for firing electronic parts and glass, and is also called a shelf board or a floor board. The ceramic setter used in the present embodiment includes oxides such as alumina, silica, magnesia and zirconia, and / or composite oxides such as cordierite, zircon and mullite, and has a thickness of about 5 to 30 mm. A flat plate having a side of about 150 to 400 mm and a ceramic porous spacer placed thereon is preferable.

Next, pre-firing (firing in step (II)) is performed on the green sheet in the laminate disposed on the ceramic setter. At this time, a weight is placed on the ceramic porous spacer disposed in the uppermost layer of the laminate so that the load applied to the green sheet in the laminate is in the range of 0.1 to 3.0 g / cm ^2. Put. For the weight, for example, a plate-like or block-like porous ceramic is used. The load applied to the green sheet by the weight is appropriately adjusted in consideration of the load applied to the green sheet by the weight of the ceramic porous spacer. That is, the total of the load due to the ceramic porous spacer and the load due to the weight applied to the green sheet in the laminate is adjusted to be in the range of 0.1 to 3.0 g / cm ² . The firing temperature in the pre-firing is in the range of 1000 to 1300 ° C.

  By performing pre-baking under the above load conditions and temperature conditions, a zirconia-based electrolyte sheet precursor suitable for the load conditions of the subsequent main baking (firing in step (III)) is obtained. That is, in the subsequent main firing, in order to correct the waviness and warpage generated in the electrolyte sheet precursor in the pre-firing, and to suppress the occurrence of waviness and warpage due to the main firing, firing is performed under a high load. Even when it is carried out, an electrolyte sheet precursor having a strength capable of withstanding the high load can be obtained. Furthermore, by performing pre-baking under such load conditions and temperature conditions, cracking of the electrolyte sheet precursor and generation of cracks due to pre-baking are less likely to occur.

Load applied to the green sheet before the time of firing, preferably 0.15 g / cm ² or more, more preferably 0.2 g / cm ² or more, preferably 2.75 g / cm ² or less, more preferably 2. 5 g / cm ² or less. The firing temperature at the time of pre-baking is preferably 1020 ° C. or more, more preferably 1050 ° C. or more, and preferably 1280 ° C. or less, more preferably 1250 ° C. or less. By setting such a load condition and temperature condition, it is possible to more reliably suppress cracks and cracks generated in the electrolyte sheet precursor by pre-firing, and furthermore, undulation and warpage generated by pre-firing can be more reliably performed by subsequent post-firing. Can be corrected.

After pre-baking, main baking is performed with respect to the laminated body on a ceramic setter. The main firing is continuously performed while maintaining the laminated state from the pre-firing without changing the laminate at the time of pre-firing. However, the load applied to the electrolyte sheet precursor in the laminate is overlaid on the ceramic porous spacer disposed in the uppermost layer of the laminate so that the load is in the range of 3.0 to 80.0 g / cm ^2. Is placed. The firing temperature in the main firing is in the range of 1350 to 1500 ° C.

  By performing the main firing under such load conditions and temperature conditions, it is possible to correct the waviness and warpage generated in the electrolyte sheet precursor by the pre-firing, and to suppress the occurrence of waviness and warpage due to the main firing. Furthermore, by performing the main baking under such load conditions and temperature conditions, the electrolyte sheet obtained by the main baking is less likely to be cracked and cracked.

The load applied to the electrolyte sheet precursor during the main firing is preferably 5.3 g / cm ² or more, more preferably 6.0 g / cm ² or more, and preferably 70.0 g / cm ² or less, more preferably 60.0 g / cm ² or less. It is desirable that the load applied to the electrolyte sheet precursor during the main firing is higher than the load during the pre-firing. By setting the load at the time of pre-firing and the load at the time of pre-firing as such a relationship, the swell and warpage of the electrolyte sheet precursor generated by the pre-firing can be more effectively corrected by the main firing. The firing temperature at the time of pre-baking is preferably 1370 ° C. or more, more preferably 1390 ° C. or more, and preferably 1480 ° C. or less, more preferably 1450 ° C. or less. By setting it as such load conditions and temperature conditions, generation | occurrence | production of the crack of an electrolyte sheet obtained by this baking and a crack can be suppressed further, and the wave | undulation and curvature which arose by pre-baking can be corrected more reliably.

  The sintered sheet obtained after the main firing is a sheet having excellent flatness with reduced waviness and warpage, and is used as an electrolyte sheet for a solid oxide fuel cell.

  Next, the present invention will be specifically described using examples. In addition, this invention is not limited at all by the Example shown below.

<Production method of zirconia green sheet>
[Green sheet of scandia partially stabilized zirconia (4ScSZ)]
Commercially available scandia partially stabilized zirconia (4ScSZ) (hereinafter referred to as “4ScSZ”) powder (trade name “4ScSZ”, average particle size: 0.6 μm, manufactured by Daiichi Rare Element Chemical Co., Ltd.) 100 parts by mass On the other hand, a binder made of a methacrylate copolymer (molecular weight: 1000000, glass transition temperature: −8 ° C., solid content concentration: 50 mass%) is 15 mass parts in terms of solid content, and sorbitan acid trioleate 2 as a dispersant. 4 parts by weight of 3 parts by weight of dibutyl phthalate as a plasticizer and 50 parts by weight of a toluene / isopropanol mixed solvent (mass ratio: 3/2) as a solvent in a nylon pocket charged with zirconia balls and kneaded for 35 hours A slurry was prepared. The obtained slurry was transferred to a jacketed round bottom cylindrical vacuum depressurization vessel equipped with a bowl-shaped stirrer, and the jacket temperature was reduced to 30 ° C. while the stirrer was rotated at a speed of 30 rpm. The viscosity was adjusted to 5 Pa · s by concentration and defoaming at 21 kPa) to obtain a slurry for coating. This coating slurry is transferred to a slurry dam of a coating apparatus, coated on a polyethylene terephthalate (PET) film by a doctor blade method, and a drying section (3 zones at 50 ° C., 80 ° C. and 110 ° C.) following the coating portion. The 4ScSZ green sheet having a thickness of 180 μm was obtained by passing the dried part) at a rate of 0.4 m / min and drying. The green sheet was cut to obtain a circular 4ScSZ green sheet having a diameter of about 118 mm.

[Green sheet of yttria partially stabilized zirconia (8YSZ)]
Commercially available yttria partially stabilized zirconia (8YSZ) (hereinafter referred to as “8YSZ”) powder (Daiichi Rare Element Chemical Industries, Ltd., trade name “HSY-8”, average particle size: 0.4 μm) An 8YSZ green sheet was produced in the same manner as the 4ScSZ green sheet except that it was used. However, the thickness of the obtained 8YSZ green sheet was 325 μm.

[Scandia-ceria stabilized zirconia (10Sc1CeSZ) green sheet]
Commercially available scandia-ceria stabilized zirconia (10Sc1CeSZ) (hereinafter referred to as “10Sc1CeSZ”) powder (manufactured by Daiichi Rare Element Chemical Co., Ltd., trade name “10Sc1CeSZ”, average particle size: 0.5 μm) is used. A 10Sc1CeSZ green sheet was produced by the same method as that for the 4ScSZ green sheet except for the above. However, the thickness of the obtained 10Sc1CeSZ green sheet was 300 μm.

<Production of ceramic porous spacer>
12 parts by mass of the binder and the dispersant used in the production of the green sheet with respect to 100 parts by mass of commercially available low-soda alumina powder (manufactured by Showa Denko KK, trade name “AL-13”, average particle size: 55 μm) 1 part by mass, 2 parts by mass of the plasticizer and 35 parts by mass of the solvent were added, and 10 parts by mass of carbon black was added as a pore-forming agent to prepare an alumina slurry by the same method as that for producing the green sheet. The viscosity of the alumina slurry was adjusted to 10 Pa · s by the same method as that for producing the green sheet to obtain a coating slurry. This coating slurry was coated on a PET film by the same method as that for producing the green sheet, and further dried. However, the passing speed of the drying section was 0.8 m / min. Thereby, an alumina green sheet having a thickness of 200 μm was obtained. This alumina green sheet was cut to obtain a circular alumina green sheet having a diameter of about 130 mm.

  The cut circular alumina green sheet was placed on an alumina plate whose surface was polished, and corn starch was uniformly applied thereon using a brush. Further, a circular alumina green sheet was superposed thereon. The same operation was repeated, and a total of 10 alumina green sheets were superposed via corn starch. Furthermore, an alumina plate having a thickness of 1.5 mm (trade name “Y-1” manufactured by a company other than Mitsui Kinzoku Kogyo Co., Ltd., porosity: about 26%) was placed thereon. In this state, degreasing was performed at 500 ° C. in an air atmosphere, followed by firing at 1580 ° C. for 2 hours to obtain a ceramic porous spacer. The obtained spacer had a thickness of 180 μm, a diameter of 120 mm, a porosity of 55%, and a mass of 3.6 g.

<Pre-firing of zirconia green sheet (firing of step (II) in the present invention)>
On the 300 mm square ceramic setter, a laminate composed of the ceramic porous spacer and the 4ScSZ green sheet prepared by the above method was disposed. Specifically, four ceramic porous spacers were placed side by side on a 300 mm square ceramic setter, and a 4ScSZ green sheet was placed thereon. On each of these 4ScSZ green sheets, ceramic porous spacers and 4ScSZ green sheets are alternately stacked, and finally 6 ceramic porous spacers having ceramic porous spacers disposed in the lowermost layer and the uppermost layer are arranged. Four sets of laminates composed of spacers and five green sheets were placed on a ceramic setter. A porous block (porosity 52%) having a crystalline phase of mullite and alumina as a weight is mounted on the ceramic porous spacer located in the uppermost layer of the laminate so as to have the load shown in Table 1. I put it. 10 pieces of ceramic setters with a total of 40 sets (40 sets in total) are placed on a conveyor belt and degreased with a frontage of 340mm, a height of 20mm, and a front setting of about 500 ° C or less. The temperature shown in Table 1 is set to the maximum temperature in a tunnel furnace type continuous heating furnace, which is a firing zone where the temperature can be set below 1500 ° C at the back of the zone, at a running speed of 0.3 m / hour. Pre-baking was performed. The 8YSZ green sheet and the 10Sc1CeSZ green sheet were also pre-fired by the same method. By such pre-firing, an electrolyte sheet precursor was obtained.

<Main firing of electrolyte sheet precursor (firing of step (III) in the present invention)>
On the ceramic porous spacer located in the uppermost layer of the laminate composed of the 4ScSZ electrolyte sheet precursor and the ceramic porous spacer pre-fired as described above, the load due to the weight is as shown in Table 1. A porous block was added to the continuous heating furnace, and the continuous heating furnace was again charged at a running speed of 1.0 m / hour, and the main calcination was performed with the temperature shown in Table 1 as the maximum temperature. By this main firing, a circular 4ScSZ electrolyte sheet having an average thickness of 162 μm and a diameter of about 100 mm was obtained. The 8YSZ electrolyte sheet precursor and the 10Sc1CeSZ electrolyte sheet precursor were also pre-fired by the same method, respectively, and a circular 8YSZ electrolyte sheet having an average thickness of 299 μm and a diameter of about 100 mm and an average thickness A round 10Sc1CeSZ electrolyte sheet having a diameter of about 262 μm and a diameter of about 100 mm was obtained.

<Calculation of crack / crack occurrence rate, sheet breakage rate>
About the electrolyte sheet precursor after pre-baking and the electrolyte sheet after main baking, the presence or absence of cracks and cracks is visually observed, and the following formulas (2) to (4) are used for the crack / crack occurrence rate and sheet breakage rate. Respectively and calculated. The results are as shown in Table 1.
Cracking / crack rate after pre-firing (%)
= {(Number of cracks / cracks generated after pre-firing) / 200} × 100 (2)
Cracking / cracking rate after firing (%)
= {(Number of cracks / cracks generated after firing) / (200- (number of cracks / cracks generated after pre-firing)} × 100 (3)
Sheet breakage rate (%)
= {(Number of cracks / cracks generated after pre-firing + number of cracks / cracks generated after main firing) /
200} × 100 (4)

<Measurement of swell height and warp height>
The waviness height and warpage height of the pre-fired electrolyte sheet precursor and the post-fired electrolyte sheet are measured by a laser optical non-contact three-dimensional shape measuring device (trade name “UBM1-14 type micro focus” manufactured by UBM). “Expert”, light source: semiconductor laser (780 nm), spot diameter: 1 μm, vertical resolution: 0.01 μm). The surface of the electrolyte sheet precursor on which the swell and warpage are visually observed on the apparatus work table was irradiated with laser light, and was obtained from the difference between the maximum height position and the minimum height position measured by scanning. In the case of the measurement of the undulation height, the scanning direction is a direction passing through the ridge peak and valley bottom of the undulation, and when multiple undulations are observed in one electrolyte sheet precursor, the four directions are determined in the order determined to be larger. Scanned and measured. Further, the scan direction in the case of measuring the warp height is the diameter direction, and when a plurality of warps are observed in one electrolyte sheet precursor, the measurement was performed by scanning in four directions in the order judged to be large. The maximum one of the measured warp height and waviness height of the electrolyte sheet precursor after pre-baking is shown in Table 1 as “maximum warp height” and “maximum waviness height”. Also, the electrolyte sheet after the main firing was similarly measured for warp height and waviness height, and the maximum ones are shown in Table 1 as “maximum warp height” and “maximum waviness height”, respectively. Furthermore, the decrease in the maximum warp height of the electrolyte sheet precursor after the main firing relative to the maximum warp height of the electrolyte sheet precursor after the pre-firing from the maximum warp height of the electrolyte sheet precursor after the pre-firing The correction rate is shown in Table 1. Similarly, the decrease in the maximum waviness height of the electrolyte sheet precursor after the main firing relative to the maximum waviness height of the electrolyte sheet precursor after the prefiring is reduced from the maximum waviness height of the electrolyte sheet precursor after the prefiring. Table 1 shows the correction rate.

As shown in Table 1, after performing pre-baking within a range of a load per unit area of 0.1 to 3.0 g / cm ² and a baking temperature of 1000 to 1300 ° C., per unit area Test examples 1, 2, 5, 6, 7, 9, wherein the main firing was performed within a range of 3.0 to 80.0 g / cm ² and a firing temperature of 1350 to 1500 ° C. The sintered sheet obtained in No. 10 had a rate of correction of waviness height and warp height of 40% or more, while the damage rate due to firing was 5% or less. That is, in the sintered sheet obtained by the production method of the present invention, the occurrence of cracks and cracks was suppressed, and the waviness height and warpage height were reduced.

On the other hand, when the load at the time of pre-firing is larger than 3.0 g / cm ² as in Test Example 8, the rate of occurrence of cracks and cracks at the pre-firing stage has become very large. Therefore, it was found that the method of applying a large load at the time of pre-firing as in Test Example 8 is not appropriate without performing the main calcination.

As in Test Example 3, when the load during the main firing is less than 3.0 g / cm ² , the breakage rate can be reduced, but the undulation and warpage generated in the pre-firing are hardly corrected and the height is not corrected. The rate was 20% or less. When the load during the main firing was larger than 80.0 g / cm ² as in Test Example 4, the occurrence of cracks and cracks was very large, and the sheet breakage rate was increased to nearly 20%.

  In Test Example 11, the load conditions and temperature conditions in the main firing were the same as in Test Example 1, but no pre-firing was performed. Therefore, comparing Test Example 1 and Test Example 11, in Test Example 11, the sheet breakage rate exceeded 10%, and the sheet breakage rate was 2 times higher than Test Example 1. Furthermore, the sheet obtained in Test Example 11 had a maximum waviness height and a maximum warp height higher than those obtained in Test Example 1. From this result, in the one-step firing without pre-firing, when the main firing is performed with a higher load than before in order to suppress sheet waviness and warpage, the generated waviness and warpage can withstand that load. It is thought that it is easy to break without being damaged. Furthermore, from this result, it was also found that it is difficult to sufficiently suppress the undulation and warpage generated in the sheet only by increasing the load by one-step firing. That is, by pre-baking the green sheet under the load conditions and temperature conditions specified in the present invention, an electrolyte sheet precursor that can withstand a large load during the main baking can be obtained. By performing main firing with a large load applied to the precursor, an electrolyte sheet having a low sheet breakage rate and reduced waviness and warpage can be obtained.

Further, as in Test Example 12, in the one-stage firing without pre-firing, when the load is reduced to 1.8 g / cm ² in order to suppress breakage of the sheet, the breakage rate is lower than that in Test Example 11. The swell height and warpage height became very large. On the other hand, as in Test Example 13, when the load was 100.0 g / cm ² in one-stage firing, the bend height and the warp height could be made lower than in Test Example 11, but the breakage rate was It became very large and exceeded 40%.

  Test Examples 14 to 17 perform two-stage baking of pre-baking and main baking, and the load during pre-baking and the load during main baking are within the range specified in the present invention. This is a test example in which the temperature is outside the temperature range specified in the present invention. In Test Example 14, the temperature during the pre-firing was lower than 1000 ° C, and the temperature during the main firing was lower than 1350 ° C. In Test Example 14, the sheet breakage rate was very low at 1.0%, but the correction ratios for the waviness height and the warp height were as low as 15% or less. In Test Example 15 in which the temperature of the main baking exceeds 1500 ° C., cracks and crack generation rates in the main baking were large, and the sheet breakage rate was close to 30%. Further, in Test Example 16 in which the pre-baking temperature exceeds 1300 ° C. and the main-baking temperature is lower than 1350 ° C., the correction ratio of the swell height and the warp height is as low as 10% or less. . In Test Example 17 in which the pre-baking temperature exceeded 1300 ° C. and the main-baking temperature exceeded 1500 ° C., the sheet breakage rate exceeded 20%.

  Next, the finally obtained electrolyte sheets are compared between the same sheet materials. In Test Examples 1, 3, 5, 7, 9 to 14 and 16 using zirconia containing scandia as a sheet material, it was obtained by Test Examples 1, 5, 7, 9 and 10 satisfying the production method of the present invention. The maximum waviness height and the maximum warp height of the electrolyte sheet were lower than those of other test examples not satisfying the production method of the present invention. Among other test examples, Test Example 13 in which the maximum waviness height and the maximum warp height are relatively low has a very high sheet breakage rate, and is not considered suitable as a method for manufacturing an electrolyte sheet in terms of productivity. It was.

  As a result, it was found that according to the production method of the present invention, an electrolyte sheet satisfying both sheet productivity and sheet quality can be obtained.

  The method for producing an electrolyte sheet for a fuel cell according to the present invention can provide an electrolyte sheet having high flatness with high productivity. Therefore, even when the electrolyte sheet is made of a high-priced material, for example, it is suitable as a method for producing an electrolyte sheet. Available.

Claims (4)

(I) On the ceramic setter, the ceramic porous spacer and the zirconia green sheet are alternately stacked so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the ceramic porous spacer and the green sheet are stacked. A step of arranging a laminate comprising:
(II) On the ceramic porous spacer disposed in the uppermost layer of the laminate so that the load applied to the green sheet in the laminate is in the range of 0.1 to 3.0 g / cm ^2. Placing a weight, and firing the green sheet in the laminate at a temperature of 1000 to 1300 ° C. to produce an electrolyte sheet precursor;
(III) After the step (II), on the uppermost layer of the laminate so that the load applied to the electrolyte sheet precursor in the laminate is in the range of 3.0 to 80.0 g / cm ^2. Placing a weight on the disposed ceramic porous spacer and firing the electrolyte sheet precursor in the laminate at a temperature of 1350-1500 ° C .;
The manufacturing method of the electrolyte sheet for fuel cells containing this. The green sheet is a zirconia-based green sheet containing at least one selected from the group consisting of scandia, yttria, ceria and ytterbia.
The manufacturing method of the electrolyte sheet for fuel cells of Claim 1. 3. The method for producing an electrolyte sheet for a fuel cell according to claim 1, wherein the ceramic porous spacer is a porous body containing at least one selected from the group consisting of alumina, zirconia, and mullite. The electrolyte sheet for a fuel cell obtained by the manufacturing method has an area of 50 to 1000 cm ² and a thickness of 0.05 to 0.5 mm.
The manufacturing method of the electrolyte sheet for fuel cells of any one of Claims 1-3.