JP5571648B2 - Zirconia sheet - Google Patents

Description

  The present invention relates to a zirconia sheet and a method for producing the same, and more particularly, to an improved zirconia sheet and a method for producing the same so that adhesion between the sheet and the electrode can be improved in the case where electrodes are formed on both sides by screen printing or the like. .

  Ceramics are used in many fields because they have excellent electrical and magnetic properties in addition to mechanical properties such as heat resistance and wear resistance. Among these, ceramic sheets mainly composed of zirconia have excellent oxygen ion conductivity, heat resistance / corrosion resistance, toughness, chemical resistance, etc., so that solid electrolyte membranes for sensor parts such as oxygen sensors and humidity sensors, It is used as a solid electrolyte membrane for fuel cells.

  By the way, a general method for producing a zirconia sheet is to form a slurry comprising a zirconia raw material powder, an organic binder and a dispersion medium into a sheet shape by a doctor blade method, a calendering method, an extrusion method, etc., and then drying the slurry to volatilize the dispersion medium. Thus, a green sheet is obtained, and the green sheet is fired after being adjusted to an appropriate size by cutting, punching or the like, and the organic binder is decomposed and removed, and the ceramic powder is sintered together.

  On the other hand, when a zirconia sheet is put into practical use, for example, for a solid electrolyte membrane of a fuel cell, electrode printing is performed on both sides of the sheet by screen printing or the like to form a fuel electrode or an oxygen electrode, and in a multilayer with separators, interconnectors, etc. Since they are stacked and assembled, a large stacking load is also applied to the electrodes formed on both surfaces of the solid electrolyte membrane. In addition, since it is exposed to a high temperature of 800 to 1000 ° C. during operation, the electrode layer easily peels from the zirconia sheet due to a slight difference in thermal expansion coefficient between the zirconia sheet and the electrode layer, and in producing a solid electrolyte membrane, The adhesion of the electrode to the zirconia sheet is extremely important.

  That is, when the adhesion of the electrode formed by screen printing or the like on both sides of the zirconia sheet to the zirconia sheet is insufficient, the electrode peels off from the zirconia sheet when it is put to practical use as a fuel cell, and the fuel The performance as a battery is drastically reduced, leading to inoperability. Therefore, for example, in a zirconia sheet used for a solid electrolyte membrane of a fuel cell, it is extremely important to improve the adhesion with a printed electrode in order to extend the life of the fuel cell.

  Therefore, in order to prevent the electrode peeling problem as described above as much as possible, in the screen printing technology, prior to electrode formation by printing or coating method, along with degreasing treatment, ceramic sheet, PET film, acrylic plate, Pre-treatment such as corona discharge treatment, flame treatment, anchor treatment (formation of thin paint film by ravia coating) or roughening of the surface to enhance the adhesion of ink to the printed material such as aluminum plate However, such pre-processing is cumbersome and time-consuming, which causes a significant reduction in productivity.

  The problem of adhesion of electrodes and the like to the zirconia sheet is very important not only for solid electrolyte membranes for fuel cells but also for thick film substrates and thin film substrates for hybrid ICs, solid electrolyte membranes for sensor and sensor substrates, etc. Become.

  The present invention has been made paying attention to the above-mentioned circumstances, and its purpose is that electrode printing or the like is performed on both sides like a solid electrolyte membrane, the bulk density with respect to the theoretical density is 97% or more, Another object of the present invention is to provide a technique capable of strongly bonding electrode printing or the like with high adhesion to a surface of a dense zirconia sheet having substantially zero gas permeability.

  The zirconia sheet according to the present invention that has solved the above problems is a sheet-like zirconia sintered body, and the surface roughness of both sides of the sheet is 0.3 to 3 μm at the maximum height (Ry). It has a gist where it has an arithmetic mean roughness (Ra) of 0.02 to 0.3 μm.

  In the zirconia sheet of the present invention, in addition to the maximum height (Ry) and arithmetic average roughness (Ra) of the individual surfaces, the other side with respect to one side surface (the surface with the smaller Ry and Ra) of the sheet The surface roughness ratio of the side surface (the surface having the larger Ry and Ra) is 1 to 5 in terms of the maximum height ratio (Ry ratio), and 1 to 10 in terms of the arithmetic average roughness ratio (Ra ratio). A high degree of adhesion can be given to both surfaces, and peeling of the electrode film and the like during operation can be more effectively suppressed, which is preferable.

Further, the zirconia sheet has a thickness of 10 μm or more, more preferably 30 μm or more, further preferably 50 μm or more, 500 μm or less, more preferably 300 μm or less, particularly preferably from the viewpoint of enhancing practicality as a solid electrolyte membrane or the like. Is preferably 200 μm or less. Preferable zirconia constituting the sheet includes alkaline earth metal oxides such as MgO, CaO, SrO and BaO, Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , Nd ₂ O ₃ and Sm. Rare earth element oxides such as ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Sc ₂ O ₃ , Examples include zirconia containing one or more stabilizers such as Bi ₂ O ₃ and In ₂ O ₃ , and other additives include SiO ₂ , Al ₂ O ₃ , Ge ₂ O ₃ , and B ₂ O _3. , SnO ₂ , Ta ₂ O ₅ , Nb ₂ O _5, etc. may be included.

  Among them, in order to ensure higher thermal, mechanical, electrical, and chemical characteristics, tetragonal and / or cubic structure zirconium oxide stabilized with 2 to 7 mol% yttrium oxide is preferable. The zirconia sheet can be used particularly effectively for a solid electrolyte membrane, particularly for a solid electrolyte membrane of a fuel cell.

  And the manufacturing method of this invention provides the method of obtaining the zirconia sheet which satisfy | fills the above surface properties reliably, The structure is an average of a slurry solid component as a slurry used for manufacture of a green sheet. A slurry having a particle diameter (50 volume% diameter) of 0.05 to 0.5 μm, a 90 volume% diameter of 0.5 to 2 μm, and a critical particle diameter (100 volume% diameter) of 5 μm or less is used as a sheet. It has a gist in that it is molded into a shape and then sintered.

  The present invention is configured as described above, and by specifying the surface roughness of both surfaces of the zirconia sheet, even when electrode printing is performed on both surfaces as in the case of a solid electrolyte membrane, the unevenness due to the uneven thickness of the electrode printing is achieved. The electrode can be strongly bonded with a high degree of adhesion without causing problems such as poor electrical conduction, and partial peeling during electrode formation and electrode peeling during operation are suppressed as much as possible. In particular, when used for a fuel cell, the power generation characteristics and durability of the fuel cell can be greatly extended.

  Under the above-described problems, the present inventors have made extensive studies to make it possible to form electrode printing or the like on both surfaces of a zirconia sheet with high adhesion. As a result, the surface roughness of both sides of the sheet is extremely important for improving the adhesion, and the surface roughness is within a specific range in terms of maximum roughness (Ry) and arithmetic average roughness (Ra). What was adjusted is that the adhesion to electrode printing or the like is surely improved, and the present invention has been conceived.

  That is, when applying or coating an electrode on a zirconia sheet by screen printing or the like, it is necessary to make the surface roughness of both surfaces of the sheet within an appropriate range in order to improve the adhesion between the sheet and the electrode printing. The surface roughness is within the range of 0.3 to 3 μm at the maximum height (Ry) and 0.02 to 0.3 μm at the arithmetic average roughness (Ra). It was confirmed that high adhesion was exhibited at the interface.

  That is, when the surface of the sheet is too smooth, specifically, when Ry is less than 0.3 μm and / or Ra is less than 0.02 μm, the line width or pitch is narrow and the high density used substantially at room temperature. It can be put to practical use as a wiring board without any problem, but when it is sintered after electrode formation, when it is used for a long time at high temperature, or when it is repeatedly subjected to thermal history between room temperature and high temperature, Peeling easily occurs between electrode surfaces. Therefore, in order to avoid such a problem, a complicated surface roughening treatment or the like is required prior to the electrode coating formation. However, when the surface roughness of the sheet is too large, specifically, when Ry exceeds 3 μm and / or Ra exceeds 0.3 μm, it is difficult to form an electrode having a uniform thickness, and further, a zirconia sheet. The adhesion of the will decrease.

  Incidentally, as a method for forming a zirconia sheet, a slurry composed of a zirconia raw material powder, an organic binder, and a dispersion medium is generally used as described above by a doctor blade method, a calendar method, an extrusion method, or the like. It is spread on a film and formed into a sheet shape, which is dried and the dispersion medium is volatilized to obtain a green sheet, which is then cut to a suitable size by punching or the like and then fired to decompose and remove the organic binder. In addition, the surface in contact with the support plate and the carrier film becomes smooth while the surface side that is open to the atmosphere during drying is rougher than the surface in contact with the carrier film. In the present invention, it is necessary to provide excellent electrode adhesion on both sides of the film. Since, both the surfaces of the surface roughness is defined as fall within the aforementioned range.

  In addition, the said surface roughness as used in the field of this invention means the value measured based on JIS B-0601 revised in 1994, and the measuring instrument used is "Surfcom 1400A" by Tokyo Seimitsu Co., Ltd.

That is, when measuring Ry, if Ry is in the range of more than 0.3 μm to 0.5 μm, the reference length l is 0.25 mm, the evaluation length l _n is 1.25 mm, and Ry exceeds 0.5 μm. In the case of less than 3, the measurement is performed with the reference length l being 0.8 mm and the evaluation length l _n being 4 mm.

In the measurement of Ra, when Ra is over 0.02 μm and 0.1 μm or less, the cutoff value λc is 0.25 mm, the evaluation length l _n is 1.25 mm, and Ra is over 0.1 μm and 0 for .3μm below is a value obtained by measuring the cut-off value [lambda] c 0.8 mm, evaluation length l _n as 4 mm.

  And when the surface roughness of both sides of the sheet required by this method falls within the above range, an electrode having a uniform thickness can be easily applied and formed on both sides of the sheet, and a high level of adhesion can be obtained by an appropriate anchor effect. It is possible to prevent electrode film peeling as much as possible during electrode firing or during operation exposed to high temperatures, and even when subjected to thermal history that is repeatedly exposed to conditions from low to high temperatures. It becomes.

  More preferable surface roughness considering both the formability and adhesion of the electrode film is Ry of 0.35 μm or more, more preferably 0.5 μm or more, 2 μm or less, more preferably 1.5 μm or less, Ra 0.025 μm or more and 0.1 μm or less.

  When a zirconia sheet is used as an electrolyte membrane, the electrode is basically not in a fine state where a circuit is formed with a fine line width, such as a conductor of an electronic material substrate such as a hybrid IC, and the periphery of the sheet Ry is more important than Ra as a surface roughness factor, particularly by making Ry in the range of 0.3 to 3 μm. Even when repeatedly exposed to a temperature range from room temperature to a high temperature around 1000 ° C., peeling between the zirconia sheet and the electrode layer hardly occurs for a long time.

  In the present invention, in order to enable the electrode film to be formed on both sides of the sheet with high adhesion, the other side surface (the surface having the larger Ry and Ra) relative to the one side surface (the surface having the smaller Ry and Ra) is formed. ) Has a maximum height ratio (Ry ratio) of 1 or more and 5 or less, more preferably 1 or more and 4 or less, and an arithmetic average roughness ratio (Ra ratio) of 1 or more and 10 or less. More preferably, it is in the range of 1 or more and 5 or less.

  By the way, if the Ry ratio or Ra ratio exceeds the above preferred range, the surface roughness on both sides is too different, so that the peeling of the zirconia sheet and the electrode layer tends to occur intensively on the one with poor printability or adhesion. Overall quality is poor.

  The production method of the zirconia sheet satisfying the above surface roughness is not particularly limited, and according to a conventional method, a slurry containing a zirconia raw material powder, an organic or inorganic binder, a dispersion medium (solvent), and if necessary, a dispersant or a plasticizer, a doctor blade method The green sheet is obtained by applying a suitable thickness on a smooth substrate such as a polyester sheet by a calender roll method, an extrusion method, etc., and drying to remove the dispersant by volatilization. Then, the method of mounting on the porous setter on a shelf board and heat-baking for about 2 to 5 hours at the temperature of about 1400-1600 degreeC is employ | adopted.

  At this time, it is the grain size composition of the zirconia raw material powder that most affects the surface roughness of the finished sheet. When a coarser one is used, the surface roughness becomes relatively rougher, and when a finer one is used, the surface roughness becomes larger. The thickness becomes relatively small. And in order to obtain more efficiently the zirconia sheet of the surface roughness range intended in the present invention, the average particle size is in the range of 0.1 to 0.8 μm as the raw material powder to be used, and the particle size is as uniform as possible. It is desirable to use those having a small particle size distribution, specifically, 90% by volume or more of the powder is 5 μm or less.

  However, when the present inventors have further researched, what is more important in securing the surface roughness defined in the present invention is not the particle size configuration of the raw material powder itself as described above, but in the form of a sheet. The particle size constitution of the solid component contained in the slurry at the time of coating, and the particle size constitution is 0.05 μm or more, 0.5 μm or less in average particle diameter (50 vol% diameter), and 0 in 90 vol% diameter. It is confirmed that a zirconia sheet satisfying the requirements for the surface roughness can be obtained more reliably by using a slurry satisfying the requirements of 5 μm or more and 2 μm or less and a critical particle size (100 volume% diameter) of 5 μm or less. ing.

  More preferable particle size constitution of the solid component contained in the slurry is 0.1 μm or more and 0.5 μm or less in terms of average particle size (50% by volume), 0.8 μm or more and 1.5 μm or less in terms of 90% by volume, The limit particle diameter (100 volume% diameter) is 3 μm or less.

  Incidentally, in the preparation of the slurry, a method of uniformly kneading and crushing the suspension of the raw material mixture including the raw material powder by using a ball mill or the like is employed. However, the kneading conditions (the type of dispersant and the addition of the dispersant) Depending on the amount, the raw material powder may cause secondary agglomeration in the slurry preparation step, or a part of the raw material powder may be further crushed. Is not the same. Therefore, when producing the zirconia sheet of the present invention, as the most influential factor on the surface roughness of the sheet, the particle size constitution of the solid component contained in the slurry before coating into a sheet is within the above preferred range. It can be said that it is a more reliable method to adjust so that it is inside.

  The particle size constitution of the raw material powder and the solid component in the slurry is a value measured by the following method. That is, the particle size composition of the raw material powder is a laser diffraction particle size distribution analyzer “SALD-1100” manufactured by Shimadzu Corporation, and an aqueous solution in which 0.2 wt% sodium metaphosphate is added as a dispersant in distilled water. Is a measurement value after adding 0.01 to 1% by weight of raw material powder in 100 cc of the dispersion medium and dispersing by sonication for 1 minute, and the particle size constitution of the solid component in the slurry is Using a solvent having the same composition as the solvent as a dispersion medium, each slurry was added to 100 cc of the dispersion medium so as to be 0.01 to 1% by weight, and similarly subjected to ultrasonic treatment for 1 minute for dispersion. Value.

  Of course, the zirconia sheet of the present invention may be composed essentially only of zirconium oxide. However, for example, a sheet used for a solid electrolyte membrane of a fuel cell has a higher degree of thermal, mechanical, Since electrical and chemical characteristics are required, in order to satisfy these required characteristics, oxidation of 2 to 7 mol%, more preferably 2.5 to 6 mol%, still more preferably 3.5 to 5 mol% is required. Zirconium oxide (tetragonal and / or cubic zirconia) stabilized with yttrium is recommended as a more preferred one.

  Further, when the zirconia sheet is put into practical use particularly for a solid electrolyte membrane of a fuel cell, in order to suppress the current loss as much as possible while satisfying the required strength, the sheet thickness is 10 μm or more, more preferably 50 μm or more, The thickness is 500 μm or less, more preferably 300 μm or less.

In addition, the sheet may have any shape such as a circle, an ellipse, or a square having an R (R), and the sheets may have similar circular, oval, or square holes having an R. May be. Furthermore, the area of the sheet is 50 cm ² or more, preferably 100 cm ² or more. In addition, this area means the area of the outer periphery including the area of this hole, when there exists a hole in a sheet | seat.

  There is no particular limitation on the type of binder used in the present invention, and conventionally known organic or inorganic binders can be appropriately selected and used. Examples of organic binders 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, celluloses such as ethyl cellulose, and the like.

  Among these, from the viewpoints of green sheet moldability and strength, thermal decomposability during firing, and the like, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, and the like. Alkyl acrylates having the following alkyl groups, and alkyl groups having 20 or less carbon atoms such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc. Alkyl methacrylates, hydroxyethyl acrylate, hydroxypropylene having 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 The number average molecular weight obtained by polymerizing or copolymerizing at least one monomer containing a carboxyl group such as maleic acid half ester such as maleic acid and monoisopropylmalate is 20,000 to 200,000, more preferably 50,000-100,000 (meth) acrylate copolymers are recommended as preferred. These organic binders can be used alone or in combination of two or more as necessary. Particularly preferred is a monomer polymer 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 admixture of two or more.

  The use ratio of the zirconia raw material powder and the binder is preferably in the range of 5 to 30 parts by weight, more preferably 10 to 20 parts by weight with respect to 100 parts by weight of the former. Insufficient strength and flexibility of the sheet, conversely, if too much, not only is it difficult to adjust the viscosity of the slurry, but the decomposition and release of the binder component during firing is large and intense, making it difficult to obtain a homogeneous sheet. Become.

  Examples of the solvent used for the production of the green sheet include water, alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol, ketones such as acetone and 2-butanone, pentane, hexane and heptane. Aliphatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and other aromatic hydrocarbons, and acetates such as methyl acetate, ethyl acetate, and butyl acetate are appropriately selected and used. These solvents can also be used alone, or two or more of them can be appropriately mixed and used. The amount of these solvents used should be appropriately adjusted in consideration of the viscosity of the slurry at the time of forming the green sheet, and preferably the slurry viscosity is in the range of 10 to 200 poise, more preferably 10 to 50 poise. It is good to adjust.

  In preparing the slurry, in order to promote peptization and dispersion of the zirconia raw material powder, polymer electrolytes such as polyacrylic acid and ammonium polyacrylate, organic acids such as citric acid and tartaric acid, isobutylene or styrene and maleic anhydride And a dispersant comprising a copolymer of styrene and an ammonium salt or an amine salt thereof, a copolymer of butadiene and maleic anhydride and an ammonium salt thereof; dibutyl phthalate or dioctyl phthalate for imparting flexibility to a green sheet Plasticizers made of glycols such as phthalic acid esters such as propylene glycol and glycol ethers, and the like; and surfactants and antifoaming agents can be added as necessary.

  A slurry composed of the above raw material blend is formed into a sheet by the method as described above, dried to obtain a zirconia green sheet, and then heated and fired to obtain the zirconia sheet of the present invention. In this firing step, as a means for obtaining a ceramic sheet having a high flatness without causing warping or undulation, the shrinkage rate due to heating until the firing temperature of the green sheet has an area larger than the green sheet. Is 5% or less, and the green sheet is sandwiched and fired between porous sheets having a bulk density of 5 to 60% of the theoretical density so that the peripheral edge does not protrude, or the porous sheet It is desirable to perform firing after placing the sheet so that the periphery of the green sheet does not protrude.

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

Example 1
Commercially available 3 mol% yttria-stabilized zirconia powder (trade name “HSY-3.0” manufactured by Daiichi Rare Element Co., Ltd., 100 parts by weight, a binder made of a methacrylic copolymer (molecular weight: 30000, glass transition temperature: −8 15 ° C.), 2 parts by weight of dibutyl phthalate as a plasticizer, 50 parts by weight of a mixed solvent of toluene / isopropanol (weight ratio = 3/2) as a dispersion medium, into a nylon pot charged with zirconia balls having a diameter of 5 mm The slurry was kneaded at about 60 rpm, which is 70% of the critical speed, for 40 hours to prepare a slurry.

  A part of this slurry was sampled, diluted with a mixed solvent of toluene / isopropanol (weight ratio = 3/2), and the particle size distribution measuring device “SALD-1000” manufactured by Shimadzu Corporation was used to measure the solid components in the slurry. When the particle size distribution was measured, it was confirmed that the average particle diameter (50 volume% diameter) was 0.35 μm, the 90 volume% diameter was 0.85 μm, and the critical particle diameter (100 volume% diameter) was 1.95 μm. .

  The slurry was concentrated and degassed to adjust the viscosity to 30 poise (23 ° C.), and finally passed through a 200 mesh filter and coated on a polyethylene terephthalate (PET) sheet by a doctor blade method to obtain a green sheet. It was. This green sheet was cut into squares, degreased by sandwiching the top and bottom with a 99.5% alumina porous plate (porosity: 30%) with a maximum height of 10 μm, and then heated and fired at 1480 ° C. for 3 hours. A 3 mol% yttria-stabilized zirconia sheet having a size of about 100 mm square and a thickness of 0.1 mm was obtained.

  The glossy surface (PET surface) that was in contact with the PET film and the surface that was exposed to the air on the opposite side (Air surface) of the obtained green sheet were each equally divided into 10 mm squares by 100, The surface roughness was measured at a measuring speed of 0.30 mm / sec using a surface roughness meter “Surfcom 1400A” manufactured by Tokyo Seimitsu Co., Ltd. for the divided surfaces of both surfaces 200 in total. In the measurement, the JIS B-0601 regulations revised in 1994 were applied to the analysis parameters. The results are shown in Table 1.

Example 2
A slurry was prepared in exactly the same manner as in Example 1 except that the zirconia raw material powder was replaced with a commercially available 4.5 mol% yttria-stabilized zirconia powder (trade name “HSY-4.5” manufactured by Daiichi Rare Element Co., Ltd.). did. A part of the slurry was sampled, and the particle size distribution of the solid component was measured in the same manner as in the above example. As a result, the average particle size was 0.28 μm, the 90 volume% size was 0.79 μm, and the critical particle size was 1. It was confirmed to be 54 μm.

  Using this slurry, a 4.5 mol% yttria-stabilized zirconia sheet having a size of about 100 mm square (thickness: about 0.2 mm) was produced in the same manner as described above, and the surface roughness was measured in the same manner.

Example 3
A slurry was prepared in exactly the same manner as in Example 1 except that the zirconia raw material powder was replaced with a commercially available 6 mol% yttria-stabilized zirconia powder (trade name “HSY-6.0” manufactured by Daiichi Rare Element Co., Ltd.). A part of the slurry was sampled and the particle size distribution of the solid component was measured in the same manner as in Example 1. As a result, the average particle size was 0.43 μm, the 90 volume% size was 1.65 μm, and the critical particle size was 2. Confirmed to be 21 μm.

  Using this slurry, a 6 mol% yttria stabilized zirconia sheet having a diameter of 100 mm (thickness of about 0.25 mm) was produced in the same manner as described above, and the surface roughness was measured in the same manner.

Example 4
Instead of the zirconia raw material powder, 100 parts by weight of a commercially available 8 mol% yttria-stabilized zirconia powder (trade name “HSY-8.0” manufactured by Daiichi Rare Element Co., Ltd.) and high-purity alumina powder (trade name “TMDAR manufactured by Daimei Chemical Co., Ltd.) ]) A slurry was prepared in exactly the same manner as in Example 1 except that 0.5 parts by weight of the mixed powder was used. A part of the slurry was sampled, and the particle size distribution of the solid component was measured in the same manner as in Example 1. As a result, the average particle size was 0.12 μm, the 90% by volume diameter was 0.88 μm, and the limit particle size was 2. It was confirmed to be 1 μm.

  Using this slurry, an 8 mol% yttria-stabilized zirconia sheet having a diameter of 100 mm (thickness: about 0.3 mm) was produced in the same manner as described above, and the surface roughness was measured in the same manner.

Comparative Example 1
The same slurry raw material as used in Example 1 above was placed in a nylon pot charged with nylon resin balls having a diameter of 15 mm, and kneaded at about 40 rpm, which is 50% of the critical speed, for 40 hours to form a green sheet. A slurry was prepared. A part of the slurry was sampled and the particle size distribution of the solid component was measured in the same manner as in the above examples. The average particle size (50% by volume) was 0.71 μm, the 90% by volume was 1.96 μm, It was confirmed that the critical particle diameter (100 volume% diameter) was 3.68 μm.

  Using this slurry, a 3 mol% yttria-stabilized zirconia sheet of about 100 mm square (thickness: about 0.1 mm) was produced in the same manner as described above, and the surface roughness was measured in the same manner.

Comparative Example 2
To 100 parts by weight of 6 mol% yttria-stabilized zirconia powder (same as above), 50 parts by weight of a toluene / isopropanol (3/2) mixed solvent as a dispersion medium and 1 part by weight of sorbitan acid as a dispersant are added, and the diameter is 3 mm. Using a ball mill charged with zirconia balls, mixing was performed in the same manner as in Example 1. Next, 15 parts by weight of a binder made of a methacrylic acid copolymer and 2 parts by weight of dibutyl phthalate as a plasticizer were added, and further kneaded in a ball mill for 20 hours to prepare a green sheet forming slurry. A part of the slurry was sampled and the particle size distribution of the solid component was measured in the same manner as in the above example. The average particle size was 0.10 μm, the 90 volume% size was 0.48 μm, and the critical particle size was 1. It was confirmed to be 75 μm.

  Using this slurry, a 6 mol% yttria-stabilized zirconia sheet having a diameter of 100 mm (thickness: about 0.3 mm) was produced in the same manner as in Example 3, and the surface roughness was measured in the same manner.

[Performance evaluation test]
Each of the zirconia sheets obtained in Examples 1 to 4 and Comparative Examples 1 and 2 was immersed in a 5% aqueous sodium hydroxide solution, and the surface of the sheet was degreased by applying ultrasonic waves for 3 minutes. , A paste containing nickel oxide powder / zirconium oxide powder combined with a zirconia sheet and a thermal expansion coefficient is screen-printed on one side, dried at 100 ° C. and then heated and fired at 1300 ° C. for 1 hour, and then lanthanum, strontium, Manganate (La _0.8 Sr _0.2 MnO ₃ ) powder-containing paste was screen-printed on the other side and fired at 1000 ° C. for 1 hour to obtain a zirconia sheet with double-sided electrodes.

  While visually observing the surface property of each obtained sheet, the interface of the electrode print layer in each sheet was observed with an SEM photograph, and the interface property was visually evaluated. The results are shown in Table 2. In Table 1, the particle size constitution of the solid component in the slurry used for the production of each zirconia sheet is also shown.

  As is clear from Tables 1 and 2, in Examples 1 to 4 where the surface roughness on both sides of the zirconia sheet satisfies the prescribed requirements of the present invention, the surface properties of the sheet are both good and have a substantially uniform thickness. However, when the surface roughness on one side of the sheet is too rough (Comparative Example 1), the surface properties are uneven and partial peeling of the electrode is observed. If the sheet is too smooth (Comparative Example 2), the sheet has good surface properties and a uniform thickness, but the adhesion with the electrode is poor and peeling occurs.

Claims (4)

  It consists of a sheet-like zirconia sintered body, and the surface roughness of both surfaces of the sheet is 0.3 to 3 μm at the maximum height (Ry) and 0.02 to 0.02 in terms of arithmetic average roughness (Ra). A zirconia sheet characterized by being 3 μm.   The surface roughness ratio of the other side surface (the surface having the larger Ry and Ra) to the one side surface (the surface having the smaller Ry and Ra) of the sheet is 1 to 5 in terms of the maximum height ratio (Ry ratio). The zirconia sheet according to claim 1, wherein the arithmetic average roughness ratio (Ra ratio) is 1 to 10.   The zirconia sheet according to claim 1 or 2, wherein the zirconia sintered body is composed of zirconium oxide stabilized with 2 to 7 mol% of yttrium oxide.   The zirconia sheet according to any one of claims 1 to 3, which is used as a solid electrolyte membrane.