JP2001089252A - Ceramic sheet and its production process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic sheet which is used as a constituent ceramic sheet of a ceramic stack formed by stacking up a number of ceramic sheets, that a large stacking load or thermal stress is applied to, such as electrolyte film for a platelike solid electrolyte type fuel cell, and in which cracks or flaws are hardly caused even when such a large stacking load or thermal stress is applied on it. SOLUTION: This ceramic sheet is provided on its surface with dimples each having a <=100 μm height measured by irradiating the surface of the ceramic sheet with a laser beam and subjecting the reflected beams to three- dimensional surface topographic analysis with a laser-optical three-dimensional surface topographic measurement instrument, and has excellent crack resistance and superior cleavage resistance with respect to a stacking load or thermal stress, applied on the sheet. The production process of the ceramic sheet is also disclosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sheet and a method for producing the same, and more particularly to a ceramic sheet and a flat solid electrolyte fuel cell, such as a solid electrolyte membrane, which are less susceptible to cracks and cracks and have a smooth surface. The present invention relates to a ceramic sheet having good quality and excellent stability, and a method for producing the same.

[0002]

2. Description of the Related Art The structure of a flat solid electrolyte fuel cell is as follows.
A cell stack is basically a cell stack in which an anode electrode and a cathode electrode are attached to both sides of a solid electrolyte, or a cell stack in which a large number of cells having an electrolyte and a counter electrode attached on the surface of the electrode are vertically stacked. Separators (interconnectors) are arranged between the cells so as to be arranged close to each other so that fuel gas and air do not mix, and the electrolyte membrane and the periphery of the cells and the separators are sealed and fixed. In addition, when a manifold is provided inside the battery cell, it is sealed and fixed at the peripheral portion thereof.

[0003] This separator is generally made of a heat-resistant alloy or ceramic having a large specific gravity, and has a considerable weight because it is in the form of a considerably thick sheet. Also,
It is desired that the ceramic sheet used as a constituent material of the fuel cell be relatively lightweight and thin. Further, the operating temperature of the solid oxide fuel cell is 800 to
Since the temperature is as high as about 1000 ° C., a large laminating load is applied to the constituent material and a considerable thermal stress is applied.

On the other hand, ceramic sheets such as zirconia sheets are hard and vulnerable to external forces in the bending direction. Therefore, irregularities, undulations, etc. are formed on the surface of ceramic sheets used as fuel cell constituent materials such as solid electrolyte membranes. If there is, the laminating load and the thermal stress concentrate at that point, causing cracks and cracks, and the power generation performance is rapidly reduced.

Accordingly, the present inventors have reduced cracks and cracks due to the above-mentioned loading load and thermal stress of a ceramic sheet used for a solid electrolyte membrane of a fuel cell and the like, with the aim of improving the performance and extending the life of the fuel cell. We have been conducting research for some time, and as a part of that research, we confirmed that if the amount of warpage and maximum undulation height of the sheet were suppressed to a predetermined value or less, the occurrence of cracks and cracks could be suppressed as much as possible,
As previously proposed (Japanese Unexamined Patent Publication Nos. 8-151270 and 8-51
No. 271).

With the ceramic sheet presented in the above publication, even a considerably large-sized sheet can withstand considerable lamination load and thermal stress, so that the power generation capacity as a fuel cell can be greatly increased. It is expected to be a very effective technology for industrial practical use of fuel cells.

However, as the present inventors proceed with further improvement research, the following facts have been gradually clarified. That is, even with the ceramic sheet having a small warpage or undulation disclosed in the above-mentioned publication, cracks and cracks may occur depending on the loading load and the degree of thermal stress, and the cause is a dimple existing on the surface of the ceramic green sheet. Has a significant effect.

In particular, when a ceramic sheet is put into practical use as the electrolyte membrane or the like, 50 sheets of the sheet are used.
Alternatively, a fuel cell is assembled by stacking about 100 or more sheets. If there are large dimples or undulations on the sheet, when the sheets are overlapped and assembled, a local internal part is formed at the dimple or undulation. When stress is generated and a load or thermal stress is applied during operation of the fuel cell, cracks and cracks are apt to occur at the corresponding location. Note that dimples are basically concave portions or convex portions formed solely on the sheet surface, and are distinguished from undulations continuously generated like waves, because the cause of generation is different.

In a general method of manufacturing a ceramic sheet, a slurry comprising a ceramic raw material powder, an organic binder, and a dispersion medium is formed into a sheet by a doctor blade method, a calender method, an extrusion method, or the like, which is dried and dried. Is volatilized to obtain a green sheet, which is punched into a predetermined shape and then fired to decompose and remove the organic binder and mutually sinter the ceramic powder. The green sheet has a length in the sintering process. About 70-90% in terms of area and about 50-80% in terms of area. Therefore, if the rate of decomposition and removal of the organic binder becomes uneven on the surface of the green sheet during the sintering, or if the shrinkage accompanying sintering becomes uneven on the surface of the sheet, large dimples and undulations occur on the surface of the obtained ceramic sheet. This is considered to be a cause and a product defect.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a large number of sheets, such as constituent materials used in a flat solid electrolyte fuel cell. For ceramic sheets that are subjected to large lamination loads and thermal stress in the state where they are stacked and assembled, even when subjected to large lamination loads and thermal stress,
An object of the present invention is to provide a ceramic sheet that is less likely to crack or crack and a method for producing the same.

[0011]

A ceramic sheet according to the present invention which can solve the above-mentioned problems is a laser optical three-dimensional shape measuring device, which irradiates a laser beam to the sheet surface and reflects the reflected light. The dimple height on the sheet surface determined by three-dimensional analysis of
It has a gist in the following places, and preferably, the dimple height is 100 μm or less and the undulation height is 100
μm or less.

Another aspect of the present invention is to specify a method by which the above-mentioned ceramic sheet can be industrially and efficiently produced. When a ceramic green sheet is fired to produce a ceramic sheet, the porosity is reduced. Is 15-8
The green sheet is sandwiched between 5% of the porous sheets so that the peripheral edge thereof does not protrude, and baked with a powder interposed between the porous sheet and the ceramic green sheet, or The point is that the porous sheet is placed on the green sheet so that the peripheral edge of the green sheet does not protrude, and firing is performed with a powder interposed between the porous sheet and the ceramic green sheet.

The ceramic sheet obtained by this method has extremely small dimples and undulations on the sheet surface, and is unlikely to cause cracks and cracks due to local concentration of stress as described above. Therefore, the ceramic sheet is used for a flat solid electrolyte fuel cell. Very useful as a ceramic sheet.

In particular, in the present invention, when the green sheet is fired, a porous sheet having a specified porosity is used to uniformly release the decomposition gas accompanying the thermal decomposition of the organic binder, Shrinkage of the green sheet during sintering by interposing powder between the sheet and the green sheet to prevent partial adhesion of the porous sheet and the green sheet, and to provide smooth sliding between the two sheets By smoothing the movement associated with, and preventing the local tensile or compressive force from acting on the sheet surface,
It is characterized in that dimples can be reduced as much as possible or undulations can be reduced as much as possible.

In order to effectively exert the function of such a porous sheet, the porous sheet must have a porosity of 15 to
It is preferable to use one having a range of 85%, more preferably 35 to 80%. In order to effectively exert the effect of the powder, the average particle diameter is 0.3 to 100 μm, more preferably 2 to 80 μm. It is desirable to use the one in the range. As the powder, any of organic and inorganic powders may be used, but preferred is a powder containing 50% by weight or more of an organic powder which is burned out by the time of sintering completion.
Among them, particularly preferred is a starchy powder in which the individual particles are substantially spherical and have an excellent sliding effect.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Under the above-mentioned problems, the inventors of the present invention have developed a ceramic sheet used as a constituent material of a flat solid electrolyte fuel cell. In order to suppress cracking, improve the performance of the fuel cell, and extend the service life,
I have been conducting research from various angles.

As a result, cracks and cracks generated in the sheet subjected to a large laminating load are greatly affected by the dimple height existing on the surface of the ceramic sheet.
00 μm or less, and preferably the swell height is 10
It has been confirmed that cracks and cracks can be suppressed as much as possible if the thickness is suppressed to 0 μm or less, and the present invention has been reached.

As described above, when large dimples are present on the surface of a ceramic sheet subjected to a large laminating load in a large number of layers when used for a fuel cell as described above, stress concentrates on the portion and directly leads to cracks and cracks. Accordingly, in the present invention, the maximum dimple height on the sheet surface is strictly defined as “100 μm or less”, and the undulation height on the sheet surface is further preferably suppressed to “100 μm or less”. Stipulates that By defining these heights, cracks and cracks caused by stress concentration when subjected to a laminating load or thermal stress due to a large number of laminations can be suppressed as much as possible. In addition, it is possible to improve the performance and greatly improve the life.

The dimple height and the undulation height are defined as “100 μm or less” under the following experimental conditions in consideration of the actual use conditions, which are requirements for suppressing the frequency of occurrence of cracks and cracks in the sheet. Stipulated.

That is, in the evaluation experiment, for various test sheets having different dimple heights and undulation heights, the ordinary stacking load of 0.1 to 0.5 kg / cm ² received when used as a constituent material of a fuel cell was used. In a loaded state, the operation of raising the temperature from room temperature to 1000 ° C. in 10 hours, maintaining the temperature at 1000 ° C. for 1 hour, and then lowering the temperature to room temperature was repeated 10 times. Then, the allowable limit of the dimple height is determined as described above, and the preferable allowable limit of the undulation height is also determined as described above.

In order to suppress cracks and cracks, the dimple height on the sheet surface is preferably 80 μm or less, more preferably 50 μm or less, particularly preferably 20 μm or less, and the preferred maximum undulation height is 80 μm or less.
More preferably 50 μm or less, particularly preferably 20 μm
It is as follows.

The height of the dimple defined in the present invention can be determined by irradiating a sheet surface with a laser beam using a laser optical three-dimensional shape measuring apparatus and analyzing the three-dimensional shape of the reflected light. . That is, the laser optical three-dimensional shape measuring apparatus, when irradiating a laser beam on the surface of the ceramic sheet to be measured to focus on the sheet surface, when the reflected light is uniformly imaged on the photodiode, the sheet Non-contact type micro tertiary system with a structure in which when the surface is displaced and the image becomes uneven, a signal is issued to immediately resolve the unevenness and the lens is controlled so that the objective lens is always focused on the sheet surface. This is an original shape analysis device, and by detecting the amount of movement, it is possible to detect irregularities on the sheet surface to be measured in a non-contact manner. The resolution is usually 1 μm or less, more preferably 0.1 μm.
Those having a thickness of 1 μm or less are used, and by using such an apparatus, the dimple height on the sheet surface can be accurately detected.

There are various possible causes for the height of the dimples on the sheet surface, but the largest cause is non-uniform firing (non-uniform rate of decomposition gas generation due to thermal decomposition of binder components) or sintering. Non-uniform sliding with the porous sheet surface at the time of the above-mentioned shrinkage accompanying the progress is exemplified.

Accordingly, in order to suppress the height of the dimples, the release rate of the pyrolysis gas during sintering is made uniform over the entire surface of the sheet, the adhesion to the porous sheet is prevented, or the porosity during shrinkage due to sintering is reduced. It is important to improve the slip with the quality sheet surface.

That is, the present inventors have confirmed by experiments that the porosity is in the range of 15 to 85%, more preferably 35 to 80% when firing the green sheet, and is the same as that of the green sheet. If a large-sized porous sheet is placed on or sandwiched between green sheets, the release of decomposition gas from the entire surface of the green sheet and sintering proceed uniformly due to the soaking effect and the weight effect, and the dimple height generated during firing You can make it smaller.

However, in order to surely obtain a ceramic sheet having a dimple height of the level specified in the present invention or a smoothness satisfying the undulation height, it is not enough to use only the porous sheet having the specified porosity. It was insufficient, and it was confirmed that the height of the dimples and the height of the undulations increased depending on the quality of the sliding at the interface between the porous sheet and the green sheet during sintering. This is considered as follows.

That is, the porous sheet interposed as a spacer during firing of the green sheet has already been fired and hardly shrinks in the sintering step of the green sheet, whereas the green sheet is not sintered as described above. In this case, the length of the sheet shrinks to about 70 to 90% and the area ratio to about 50 to 80%, so that a slippage occurs in the sintering process between both sheet surfaces, particularly on the outer peripheral side of the sheet. At this time, since both sheet surfaces are almost in close contact with each other, there is a possibility that local bonding may occur on the sheet surface under the sintering temperature condition. While a compressive force acts on the green sheet surface of a part, a tensile force acts on the vicinity thereof, and the movement amount of the green sheet material becomes uneven due to the local compressive force and tensile force, which becomes a dimple. It is thought to appear. Alternatively, if the ceramic green sheet develops adhesiveness due to heat due to the properties of the organic binder and plasticizer used for molding, there is a possibility that the green sheet may adhere to the porous sheet during firing, and the green It is considered that the movement amount of the sheet becomes uneven, and this appears as dimples. The non-uniformity of these movements is
The larger the load applied to the green sheet, and the more uneven the load applied to the green sheet, the more noticeable the appearance.

Therefore, as a result of researching to eliminate the cause of the generation of dimples due to such local bonding, powder having an average particle diameter of about 0.3 to 100 μm was interposed at the contact surface between the porous sheet and the green sheet. If this is done, the bonding is prevented by the powder and the slip between the sheet surfaces is improved, and the phenomenon of generating a local tensile force or a compressive force as described above on both sheet contact surfaces is suppressed. It has been confirmed that the dimples are suppressed as much as possible, and further the undulation is suppressed, together with the slip promoting action and the action of promoting the dissociation of the decomposition gas due to the increase in the gap between the sheet surfaces due to the presence of the powder. .

The powder used herein preferably has an average particle size in the range of 0.3 to 100 μm.
The powder having a particle diameter of less than 3 μm is so fine that the above-described bonding inhibiting action, slip promoting action and decomposition gas dispersing promoting action are not effectively exerted. It may adhere or fuse to the ceramic sheet, while coarse particles exceeding 100 μm will increase the dimples and surface roughness of the resulting ceramic sheet, making it useful for electrode printing, etc. when practically used for solid electrolyte membranes. There is a risk of adverse effects. In consideration of such advantages and disadvantages, the more preferable average particle diameter of the powder is 2 μm or more and 80 μm or less, and further preferably 5 μm.
Above, it is 60 μm or less. Particularly preferred as a powder is one having a small amount of coarse particles, wherein 90% by volume of the particles is 2%.
It is not more than 00 μm, more preferably not more than 100 μm.

The powder may be either organic or inorganic, and among them, organic powder is particularly preferred. However, the inorganic powder not only remains on the sheet surface after the sintering process, but may fuse to the ceramic sheet surface depending on its type, and removal after sintering may be complicated, This is because if the powder is used, it will be burned out under the sintering conditions, and therefore, the removal operation by post-processing is not required. At the time when the sintering of the ceramic sheet is completed, there is no longer a risk of joining the ceramic sheet with the porous sheet, and since the dispersion of the organic binder component has been completed, there is no problem even if the powder does not remain. However, depending on the type of the ceramic sheet, it is also effective to use a small amount of inorganic powder together with the organic powder and leave a small amount of powder until the end of sintering. Even when inorganic powders are used in combination, it is desirable that the amount of the organic powders used is preferably 50% by weight or more, more preferably 60% by weight or more, and further preferably 80% by weight or more.

The organic powder may be of any type as long as it can be burned off under the sintering conditions as described above, such as natural organic powder, acrylic resin powder, and sublimable resin powder such as melamine cyanurate. Among them, starch powders such as wheat flour, corn starch (corn starch), sweet potato starch, potato starch, tapioca starch and the like can be used.
The starchy powder is a fine powder having a substantially spherical shape and a uniform particle size, contains almost no impurities, and has a very excellent effect as a lubricant. These organic powders may be used alone or as needed.
More than one species can be used in combination as appropriate.

The type of the inorganic powder is not particularly limited, but is preferably a natural or synthetic oxide or non-oxide such as silica, alumina, zirconia, titania, mullite, boron nitride, silicon nitride, aluminum nitride, or the like. Silicon carbide, carbon, etc., which can be used alone or in combination of two or more if necessary, are preferably used depending on the material of the green sheet or porous sheet to be used. It is preferable to select and use a low inorganic powder.

The method of applying the powder is not particularly limited, but may be brush coating, buffing, a method of dispersing the powder in a dispersion medium and spraying, a method of shaking off the powder through a sieve, a method of coating the powder in a floating fluidized bed or on the surface of the powder reservoir. A method of passing a green sheet or a porous sheet is recommended as a preferable method.

The coating amount of these powders is not particularly limited. However, if the coating amount is too large, it becomes difficult to make the coating thickness uniform over the entire surface of the sheet, and the unevenness of the thickness tends to increase the undulation of the ceramic sheet. Is seen, conversely, when the coating amount is insufficient, it is difficult to sufficiently exert the action of promoting the slip and the emission of the decomposition gas during sintering by the powder,
There is a tendency for dimples to occur easily. Therefore, the coating amount of the powder is 0.0001 cc / cm ² or more, more preferably 0.0002 cc / cm ² or more per area of the ceramic green sheet to be sintered.
cc / cm ² or less, more preferably 0.02 cc / cm ²
It is desirable to make the following.

In firing the green sheets, a porous sheet can be placed on one green sheet and fired. However, a method in which a plurality of green sheets are alternately overlapped with the porous sheets and sintered simultaneously is used. Is advantageous because the sintering operation can be performed more efficiently. Also, increase the weight of the top porous sheet,
If firing is performed by placing a further weight on the porous sheet,
This is preferable because a ceramic sheet with even more smoothness and small dimples and undulations can be obtained in addition to the weight effect.

The ceramics used as the material of the ceramic sheet include various single, mixed or composite oxides such as zirconia, alumina, titania, aluminum nitride, borosilicate glass, cordierite, and mullite. The present invention is particularly effective. A solid electrolyte membrane and a sheet for an electrode of a plate-shaped solid oxide fuel cell are used in the present invention.
Zirconia-based ceramics are particularly preferable for the solid electrolyte membrane.
alkaline earth metal oxides such as aO, SrO, BaO,
Y ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , S
m ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , H
rare earth metal oxides such as o ₂ O ₃ , Er ₂ O ₃ and Yb ₂ O ₃ ;
Further, zirconia-based ceramics containing one or more stabilizers such as Sc ₂ O ₃ , Bi ₂ O ₃ , In ₂ O _{3 and the} like can be mentioned. Among them, other additives such as SiO ₂ , A
It may contain l ₂ O ₃ , Ge ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ , Nb ₂ O _5, and the like.

In addition, CeO_TwoOr Bi_TwoO_ThreeTo Ca
O, SrO, BaO, Y_TwoO_Three, La_TwoO _Three, Ce_TwoO_Three, P
r_TwoO_Three, Nd_TwoO_Three, Sm_TwoO_Three, Eu_TwoO_Three, Gd_TwoO_Three, T
b_TwoO_Three, Dr_TwoO_Three, Ho_TwoO_Three, Er_TwoO_Three, Yb_TwoO_Three, P
bO, WO_Three, MoO_Three, V_TwoO_Five, Ta_TwoO_Five, Nb_TwoO_Fiveetc
Ceria or bis with one or more of
Mass system, and LaGaO_ThreeGallate solid-state electricity
Degraded membranes are also exemplified as preferred.

Further, the constituent materials of the anode electrode sheet include Ni, Co, Fe or oxides thereof, and the like.
The cermets with zirconia and / or ceria, and cermets to which alkaline earth metal oxides such as MgO, CaO, SrO, and BaO, and MgAl ₂ O ₄ are added, and the like, and constituent materials of the cathode electrode sheet Is a lanthanum manganate or lanthanum cobaltate having a perovskite crystal structure, or a lanthanum is partially substituted with Ca, Sr or the like, or a manganese is partially substituted with Co, Fe, Cr or the like, Further, a part of lanthanum and cobalt is replaced with Ca, Sr, Co, F
Examples thereof include a composite oxide substituted with e and the like.

Since ceramic sheets used for a solid electrolyte membrane of a fuel cell require higher thermal, mechanical, electrical and chemical properties, it is necessary to satisfy these required properties. , Zirconium oxide (tetragonal and / or cubic zirconia) stabilized with yttrium oxide of 2 to 12 mol%, more preferably 2.5 to 10 mol%, and still more preferably 3 to 8 mol% Recommended as

When the zirconia sheet is put to practical use as a solid electrolyte membrane or a sheet for an electrode, particularly for a fuel cell, the sheet thickness should be 10 μm or more in order to satisfy the required strength and suppress the electric resistance as much as possible. More preferably 50μ
m or more and 500 μm or less, more preferably 300 μm
It is better to do the following.

The shape of the sheet may be any of a circle, an ellipse, a square, a square having an R (R), and the same circular, elliptical, square, R
It may have one or two or more holes, such as squares having a square. Further, the area of the sheet is 50 cm ² or more, preferably 100 cm ² or more. In addition, this area means the total area including the area of the hole when there is a hole in the sheet.

In the production of these ceramic sheets, a slurry containing a ceramic raw material powder, an organic or inorganic binder, a dispersion medium (solvent), and, if necessary, a dispersant and a plasticizer, is used in a usual manner by a doctor blade method, a calendar roll method, and an extrusion method. A green sheet is obtained by applying a suitable thickness on a smooth sheet, for example, a polyester sheet by a method or the like, drying and volatilizing and removing the dispersant, and punching the green sheet into an appropriate size. A porous sheet is placed on a shelf, or placed on a shelf sandwiched between porous sheets, and placed at a temperature of about 1,000 to 1,600 ° C.
A method of heating and firing for about 5 hours is employed.

At this time, in order to increase the surface uniformity of the finished sheet and to reduce dimples and undulations, the average particle diameter of the raw material powder for the ceramic sheet is 0.1 to 0.1.
It is preferable to use a powder having a size of 8 μm and having as uniform a particle size as possible (a particle having a small particle size distribution), specifically, a powder in which 90% by volume or more of the powder is 5 μm or less.

The kind of the binder used in the present invention is not particularly limited, and a conventionally known organic or inorganic binder can be appropriately selected and used. Examples of the organic binder include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, and celluloses such as ethyl cellulose.

Among these, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl are preferred from the viewpoints of green sheet moldability, punching workability, strength, and thermal decomposition during firing. Alkyl acrylates having an alkyl group having 10 or less carbon atoms such as acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2
-Alkyl methacrylates having an alkyl group having 20 or less carbon atoms such as ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, and cyclohexyl methacrylate; hydroxyalkyl groups such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate And hydroxyalkyl acrylates or hydroxyalkyl methacrylates, dimethylaminoethyl acrylate, aminoalkyl methacrylates such as dimethylaminoethyl methacrylate, and maleic acid half-esters such as (meth) acrylic acid, maleic acid and monoisopropyl maleate Such as carboxyl group-containing Obtained by polymerizing or copolymerizing at least one mer, the number average molecular weight of 2,000 to 200,000, more preferably 5,00
0-100,000 (meth) acrylate copolymers are recommended as preferred. These organic binders can be used alone or in combination of two or more as needed. Among them, particularly preferred is a copolymer of a monomer containing 60% by weight or more of isobutyl methacrylate and / or 2-ethylhexyl methacrylate.

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

The use ratio of the ceramic raw material powder and the binder is 5 to 30 parts by weight of the latter with respect to 100 parts by weight of the former.
More preferably, the range of 10 to 20 parts by weight is suitable,
When the amount of the binder used is insufficient, the strength and flexibility of the green sheet become insufficient.On the contrary, when the amount is too large, not only the viscosity of the slurry becomes difficult to adjust, but also the amount of decomposition and release of the binder component during firing is reduced. It becomes difficult and difficult to obtain a uniform sheet.

The dispersion medium used for producing the green sheet includes water, alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol, ketones such as acetone and 2-butanone, and pentane. And aliphatic hydrocarbons such as hexane, heptane and the like, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and acetates such as methyl acetate, ethyl acetate and butyl acetate. These dispersion media can be used alone, or two or more of them can be used by being appropriately mixed. The amount of the dispersing medium to be used is preferably adjusted appropriately in consideration of the viscosity of the slurry at the time of forming the green sheet.
It is good to adjust so as to be in the range of ~ 200 poise, more preferably 10 ~ 50 poise.

In preparing the above slurry, a polymer electrolyte such as polyacrylic acid or polyammonium polyacrylate is used to promote deflocculation and dispersion of the ceramic raw material powder.
A dispersant comprising an organic acid such as citric acid or tartaric acid, a copolymer of isobutylene or styrene and maleic anhydride and its ammonium salt or amine salt, a copolymer of butadiene and maleic anhydride and its ammonium salt, etc .; green Plasticizers such as dibutyl phthalate and dioctyl phthalate to provide flexibility to the sheet, glycols such as propylene glycol, and glycol ethers; and surfactants and defoamers. It can be added as needed.

Thus, according to the present invention, the height of the ceramic sheet, particularly the dimple height, is controlled to 100 μm or less, and more preferably, the undulation height is also controlled to 100 μm or less, so that the solid electrolyte membrane for a flat solid electrolyte fuel cell or the like can be obtained. It has excellent resistance to stacking load and heat stress as a constituent material of the product, and can minimize the occurrence of cracks and cracks during operation as much as possible, greatly extending its life, and adopting the method of the present invention. Then, a ceramic sheet having such shape characteristics can be manufactured with high productivity.

[0051]

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

In the following examples, the particle size of the organic powder and the inorganic powder was determined by suspending the sample powder in an aqueous solution of metaphosphoric acid using a laser diffraction particle size distribution analyzer “SALD-1100” manufactured by Shimadzu Corporation. Was measured by dispersing by applying ultrasonic wave for 1 minute.

Example 1 (Preparation of porous sheet) Low soda alumina powder having an average particle diameter of 55 μm (trade name “AL-13” manufactured by Showa Denko KK)
12 parts by weight of a binder composed of a methacrylate copolymer (average molecular weight: 30,000, glass transition temperature: 0 ° C., solid content concentration: 50% by weight) based on 100 parts by weight, 2 parts by weight of dibutyl phthalate as a plasticizer, Toluene / isopropyl alcohol (weight ratio = 3/2) as dispersion medium
30 parts by weight of the mixed solvent in a nylon pot charged with zirconia balls having a diameter of 10 mm,
For 40 hours to prepare a slurry. This slurry was concentrated and defoamed to adjust the viscosity to 80 poise, and was coated on a polyethylene terephthalate film by a doctor blade method to obtain a green sheet.

A blade was attached to this green sheet in a continuous die-punching machine (trade name “865B” manufactured by Sakamoto Zoki Co., Ltd.), and a press stroke: 40 mm and a press speed: 8
It was cut to predetermined dimensions at 0 spm. The cut green sheet is placed on an alumina plate having a polished surface,
After degreased at ℃, it was fired at 1550 ℃ for 2 hours to obtain a porous sheet. The thickness of the porous sheet was 0.4 mm, the porosity was 46%, and the weight per unit area was 0.09 g / cm ² .

(Preparation of Zirconia Green Sheet) Commercially available 3 mol% yttria-stabilized zirconia powder (trade name “HYS-3.0” manufactured by Daiichi Rare Element Co., average particle size: 0.7)
μm, 90% diameter: 1.9 μm) 100 parts by weight of a binder made of a methacrylate copolymer (molecular weight:
30,000, glass transition temperature: -8 ° C, solid content:
50 parts by weight), 30 parts by weight of dibutyl phthalate as a plasticizer, 50 parts by weight of a mixed solvent of toluene / isopropyl alcohol (weight ratio = 3/2) as a dispersion medium,
A slurry was prepared by placing the zirconia balls having a diameter of 10 mm in a nylon pot and kneading them at about 60 rpm for 40 hours.

The slurry was concentrated and defoamed to adjust the viscosity to 30 poise. Finally, the slurry was passed through a 200-mesh filter, and then coated on a polyethylene terephthalate film by a doctor blade method, to give a green sheet having a thickness of about 300 μm. Obtained.

The green sheet was attached to a continuous die-cutting machine (same as above) with a blade, and the press stroke was 40 m.
m, press speed: cut into predetermined dimensions and shape at 80 spm.

(Preparation of zirconia sheet)
Place a square porous sheet with a side of 42 cm on the shelf board,
Wheat flour (average particle diameter: 20 μm,
(90% diameter: 64 μm)
It was gone. The average coating amount of the flour is 0.0008 cc / c.
m ^TwoMet. On top of that, the 40 cm side positive
Square shaped zirconia green sheet, the periphery of which is porous
Layer so that it does not protrude from the quality sheet.
Sprinkle with flour and spread evenly.
The same porous sheet as above was placed, and this was placed in an electric furnace,
By sintering at 00 ° C for 2 hours, 30cm on each side, thickness
A 220 μm square zirconia sheet was obtained.

The obtained zirconia sheet was smooth and almost no undulation or dimple was observed.

Comparative Example 1 A zirconia sheet was produced in exactly the same manner as in Example 1 except that when the porous sheet and the zirconia green sheet were stacked and fired, no flour was applied. The obtained zirconia sheet had a gentle undulation and large dimples were observed at several places on the sheet surface.

Example 2 (Preparation of porous sheet) Except that the thickness at the time of coating was adjusted and the sintering temperature was changed to 1575 ° C., a side of 13.8 cm and a thickness of 0 0.3 mm, porosity 42
%, A square porous sheet having a weight per unit area of 0.07 g / cm ² was obtained.

(Preparation of Zirconia Sheet) The porous sheet obtained above was placed on a shelf plate, and corn starch (average particle size: 14 μm, 90% diameter: 22 μm) was sprinkled on the porous sheet and uniformly spread with a brush. (Coating amount: 0.0005cc
/ Cm ² ). A square zirconia green sheet having a side of 13.5 cm obtained in the same manner as in Example 1 is placed thereon, and corn starch is sprinkled thereon and spread evenly in the same manner as described above, and this operation is repeated five times. As a result, five porous sheets and five zirconia green sheets were alternately superimposed on each other via corn starch. Finally, the porous sheets are similarly stacked via corn starch, and placed in an electric furnace at 1400 ° C. for 2 hours.
By baking for 5 hours, five square zirconia sheets each having a side of 10 cm were obtained.

Each of the obtained five zirconia sheets was smooth and almost no undulations or dimples were observed.

Comparative Example 2 Five pieces of zirconia sheets were obtained by calcination in the same manner as in Example 2 except that no corn starch was interposed between the porous sheet and the zirconia green sheet. Among the obtained zirconia sheets, the zirconia sheet located at the bottom had cracks that appeared to be caused by adhesion to the porous sheet, and large dimples were observed at several places on the surface. .

Example 3 (Preparation of porous sheet) 68 parts by weight of a low-soda alumina powder having an average particle diameter of 55 μm (the same as above) and an average particle diameter of 0.
Same as Example 1 except that a total of 100 parts by weight of 16 parts by weight of 6 μm low soda alumina powder (trade name “AL-160SG” manufactured by Showa Denko KK) and 20 parts by weight of carbon black were used as a pore-forming agent. Performing the production and firing of a porous green sheet by the method, thickness 0.5mm,
Porosity 60%, weight 0.08 g / cm per unit area
² porous sheets were obtained.

(Production of Zirconia Green Sheet) Commercially available 8 mol% yttria-stabilized zirconia powder (trade name “HYS-8.
0 ”) and the thickness of the green sheet is about 200 μm
A green sheet having a thickness of about 200 μm was obtained in the same manner as in Example 1 except that the coating thickness was adjusted such that

(Preparation of Zirconia Sheet) The above-obtained square porous sheet having a side length of 28 cm was placed on a shelf plate.
Potato starch (average particle diameter: 41 μm,
A powder obtained by mixing 80% by weight (90% diameter: 71 μm) and 20% by weight of alumina powder having an average particle diameter of 55 μm was sprinkled and uniformly spread with a brush. The average coating amount of the mixed powder was 0.002 cc / cm ² . The above-obtained square zirconia green sheet having a side length of 26 cm is superimposed thereon, and the mixed powder is sprinkled on the green sheet in a similar manner and uniformly spread, and this operation is repeated four times to obtain four porous sheets. And four zirconia green sheets are stacked via the mixed powder, and finally, the porous sheets are also stacked via the mixed powder.
For 2 hours to obtain four square zirconia sheets each having a side of 20 cm.

The four zirconia sheets obtained were all smooth, and almost no undulations or dimples were observed.

Example 4 Instead of corn starch, alumina powder (average particle size: 5
A zirconia sheet was produced in exactly the same manner as in Example 2 except that 5 μm, 90% diameter: 100 μm) was used (the coating amount was about 0.01 cc / cm ² ).

Alumina powder adhered to the surface of the fired zirconia sheet, which required cleaning, but the sheet itself was smooth with small undulations and dimples.

Comparative Example 3 A zirconia sheet was produced in exactly the same manner as in Example 4 except that alumina powder having an average particle diameter of 0.21 μm and a 90% diameter of 0.9 μm was used. Alumina powder adhered strongly to the surface of the obtained zirconia sheet, and it was difficult to remove even by ultrasonic cleaning.

Comparative Example 4 A zirconia sheet was produced in exactly the same manner as in Example 4 except that alumina powder having an average particle diameter of 180 μm was used. On the surface of the obtained zirconia sheet, dimples and undulations were generated on the entire surface due to the presence of coarse alumina powder.

Comparative Example 5 The same procedure as in Example 4 was carried out except that the alumina powder was sprinkled on a porous sheet and a zirconia green sheet while applying vibration through a 200-mesh wire mesh (application amount: 0.2 cc / cm ² ). A ceramic sheet was produced. The obtained sheet showed dimples and large undulations, probably because the applied amount of the alumina powder at the time of firing was too large and the applied thickness became uneven.

Comparative Example 6 In carrying out Example 4, the alumina powder dusted on the surface of the porous sheet and the zirconia green sheet was blown off, and the applied amount was extremely small (0.00001 cc / c).
m ² ), and a zirconia sheet was prepared in the same manner as in Example 4, except that the sheets were superposed. The obtained zirconia sheet was partially bonded to the porous sheet, and large dimples were confirmed at several places.

Comparative Example 7 Wheat flour (same as above) was applied to a zirconia green sheet obtained in the same manner as in Example 1, and five sheets were laminated without interposing a porous sheet. The firing was performed under the same conditions. The obtained sintered sheets adhered to each other and could not be peeled off here.

Example 5 (Preparation of porous sheet) Low soda alumina powder having an average particle diameter of 0.6 μm (trade name “AL-160” manufactured by Showa Denko KK)
SG "), 100 parts by weight, 18 parts by weight of a binder composed of a methacrylate polymer (average molecular weight: 30,000, glass transition temperature: 0 ° C, solid content concentration: 50% by weight), 2 parts by weight of dibutyl phthalate as a plasticizer Of a mixed solvent of ethyl acetate / toluene (weight ratio = 3/2) as a dispersion medium is placed in a nylon pot into which a zirconia ball having a diameter of 10 mm is charged.
The mixture was kneaded for a time to prepare a slurry. The slurry was concentrated and defoamed to adjust the viscosity to 40 poise, and was coated on a polyethylene terephthalate film by a doctor blade method to obtain a green sheet.

The green sheet was cut into a square having a side of 17.5 cm in the same manner as in Example 1 to obtain a green sheet.
After degreasing at 0 ° C., the mixture was fired under the same conditions as in Example 1 to obtain a porous sheet. Since the porous sheet was slightly warped, it was sandwiched between polished dense alumina plates,
Re-baking was performed at ℃ for correcting the warpage. The size of the obtained porous sheet was a square having a side of 14.2 cm, the thickness was 0.2 mm, the porosity was 20%, and the weight per unit area was 0.06 g / cm ² .

(Preparation of Zirconia Sheet) A zirconia sheet was prepared in the same manner as in Example 3 except that the porous sheet obtained above was used. Each of the obtained four zirconia sheets was smooth with small undulations and dimples.

Comparative Example 8 Instead of the porous sheet used in Example 1, the weight was 2 g /
A zirconia sheet was produced in the same manner as in Example 1 except that a dense alumina sheet having a cm ² and a porosity of 1% or less was used.

The surface of the obtained zirconia sheet had countless small wrinkles, which were not practical.

Comparative Example 9 A zirconia sheet was produced in exactly the same manner as in Comparative Example 8 except that no flour was applied. The obtained sheet had cracks and was not practical.

Evaluation Test Example 1 For each of the 20 sheets obtained in Examples 1 to 5 and Comparative Examples 1, 4 to 6, and 8, a laser optical non-contact three-dimensional shape measuring apparatus (trade name “UBC” manufactured by UBM) was used. The surface was irradiated with laser light using a “-14” microfocus expert) and the reflected light was subjected to three-dimensional analysis to measure the height of each undulation and dimple. The light source is a semiconductor laser (780 nm), the spot diameter is 1 μm, the vertical resolution is 0.01 μm, and the dimple height is 0.1 m.
It was measured at a pitch of m.

Evaluation Test Example 2 Each of the sheets was placed on two alumina plates (trade name “SSA-S” manufactured by Nickart Company) with smooth surfaces and parallelism on an alumina base plate. After applying a load of 0.2 kg / cm ² over the entire surface of the sheet,
The operation of raising the temperature to 000 ° C. over 10 hours, maintaining the temperature at 1000 ° C. for 1 hour, and then lowering the temperature to room temperature was repeated 10 times, and the occurrence frequency of cracks was examined.

The results of evaluation tests 1 and 2 are summarized in Table 1.

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[Table 1]

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According to the present invention, the solid electrolyte for a plate-shaped solid electrolyte fuel cell is specified by specifying the height of the dimples of the ceramic sheet, preferably, and further suppressing the height of the undulation. It has excellent resistance to laminating load and heat stress as a constituent material such as a film, and can minimize the occurrence of cracks and cracks during operation as much as possible.
As a result, it is possible to provide, for example, a fuel cell having high performance and greatly improved durability life. Moreover, according to the method of the present invention, ceramic sheets having such shape characteristics can be industrially and efficiently produced.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor ▲ High ▼ ▲ Saki ▼ Eijiro 992, Nishioki, Okahama-ku, Abashiri-ku, Himeji-shi, Hyogo 1 Nippon Shokubai Co., Ltd. No. 1 Within Nippon Shokubai Co., Ltd. (72) Koji Nishikawa Inventor 992 Nishioki, Okihama-shi, Abashiri-ku, Himeji-shi, Hyogo AA51 BA02 CA08 GA11 GA14 GA16 GA17 GA20 PA22

Claims (7)

[Claims] 1. A dimple height on a sheet surface obtained by irradiating a laser beam onto a sheet surface using a laser optical three-dimensional shape measuring device and three-dimensionally analyzing the reflected light thereof is 100 μm or less. A ceramic sheet characterized by the following. 2. The ceramic sheet according to claim 1, wherein the undulation height of the sheet surface is 100 μm or less. 3. The ceramic sheet according to claim 1, which is used for a flat solid electrolyte fuel cell. 4. A porosity of 15 to 85% when a ceramic green sheet is fired to produce a ceramic sheet.
The ceramic sheet, characterized in that the green sheet is sandwiched between the porous sheets so that the peripheral edge thereof does not protrude, and is fired with a powder interposed between the porous sheet and the ceramic green sheet. Manufacturing method. 5. A porosity of 15 to 85% when firing a ceramic green sheet to produce a ceramic sheet.
Is placed on the green sheet so that the peripheral edge of the green sheet does not protrude, and is fired with a powder interposed between the porous sheet and the ceramic green sheet. Manufacturing method of ceramic sheet. 6. An average particle diameter of the powder is 0.3 to 100.
The method according to claim 4 or 5, wherein the particle size is μm. 7. The method according to claim 4, wherein the powder contains 50% by weight or more of an organic powder.