JP5797050B2 - Manufacturing method of ceramic sheet - Google Patents

Description

  The present invention relates to a method for producing a ceramic sheet.

  Ceramic sheets have excellent mechanical strength, electrical insulation, toughness, wear resistance, chemical resistance, corrosion resistance, etc., so they are used for various electronic materials, various structural materials, blades, firing setters, etc. Has been. Among them, ceramic sheets mainly composed of alumina have excellent electrical insulation, so that ceramic sheets mainly composed of aluminum nitride have excellent thermal conductivity and insulation as thick film printed boards and thin film circuit boards. Therefore, as a heat dissipation / insulation substrate and a circuit board for power modules, a ceramic sheet mainly composed of zirconia is used as an electrolyte membrane of a fuel cell because it has high oxygen ion conductivity.

  When a ceramic sheet is used as an electronic substrate, a conductor circuit is formed on the substrate or an electronic element is mounted. Therefore, the ceramic sheet serving as the substrate is warped or undulated, and has surface defects such as scratches. As a result, it becomes difficult to mount a conductor circuit or an electronic element.

  In recent years, fuel cells have attracted attention as clean energy sources. Among fuel cells, a solid oxide fuel cell (hereinafter referred to as SOFC) that uses a solid ceramic as an electrolyte can use exhaust heat because of its high operating temperature, and obtains electric power with higher efficiency. It is expected to be used in a wide range of fields from household power sources to large-scale power generation.

  The SOFC 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, a flat SOFC has a single cell in which a cathode, an electrolyte sheet, and an anode are stacked. High output can be obtained by stacking a plurality of the single cells with the interconnector interposed therebetween. Such an electrolyte sheet is required to have high dimensional accuracy, high flatness (suppression of warpage and undulation), and the like. Therefore, establishment of a manufacturing method capable of realizing high dimensional stability, suppressing the occurrence of warpage and waviness, and suppressing the occurrence of cracks and chipping, in order to reduce the production cost of the electrolyte sheet and improve the productivity. Is required.

  For the SOFC electrolyte, zirconia-based, ceria-based, and lanthanum gallate-based ceramic materials are preferably used. Examples of the zirconia ceramic material include yttria stabilized zirconia (YSZ) and scandia stabilized zirconia (ScSZ). Examples of the ceria-based ceramic material include ceria doped with yttria, samaria and / or gadria. As lanthanum gallate ceramic materials, lanthanum gallate and a part of lanthanum gallium and / or gallium are replaced with strontium, calcium, barium, magnesium, aluminum, indium, cobalt, iron, nickel, and / or copper, etc. Can be mentioned. Therefore, a sheet made of these ceramic electrolyte materials can be manufactured with a high yield by a method that can realize high dimensional stability, suppress the occurrence of warpage and waviness, and suppress the occurrence of cracks and chips. Desired.

  A ceramic sheet is usually formed into a tape shape by a slurry obtained by mixing and pulverizing ceramic raw material powder, a binder, a solvent and the like into a tape shape by a doctor blade method or the like, and the green tape is cut into a predetermined shape. It can be produced by firing a punched green sheet. Normally, when firing green sheets, ceramic porous spacers and green sheets are alternately stacked on the ceramic setter for the purpose of increasing productivity and realizing high flatness of the sheet. The green sheet is fired in the state of the laminate (see, for example, Patent Document 1).

JP 2007-302515 A Japanese Patent Laid-Open No. 3-16965 JP-A-8-290976

  However, the dimensional accuracy required for ceramic sheets, particularly electrolyte sheets for SOFC, is increasing. Therefore, in the conventional method, it has become difficult to produce a ceramic sheet satisfying such high requirements with a high yield.

  Then, this invention makes it a subject to provide the method which can manufacture a ceramic sheet, especially the electrolyte sheet for SOFC with a sufficient yield.

  In order to solve the above-mentioned problems, the present inventor has studied a lamination process and a firing process of a green sheet for a ceramic sheet, and problems when firing the green sheet in the state of the laminate and a ceramic to be manufactured I found out the relationship with the yield of seats. In order to improve productivity, the number of spacers and green sheets included in the laminate tends to increase. That is, the height of the laminate tends to increase. As a result, the laminated body is displaced or broken even by a small force, for example, a small force applied when moving to the firing furnace after the spacer and the green sheet are overlapped. When the present inventor fires a green sheet in a state in which the laminate is left displaced or collapsed, the produced ceramic sheet has abnormal dimensions, warpage and waviness, abnormal appearance (occurrence of scratches, etc.), cracks and It was found that chipping occurred and the yield decreased.

  For the production of an alumina substrate, a method of firing in a state where alumina green sheets are laminated is generally used. Therefore, various techniques for suppressing the deviation of the laminated green sheets have been proposed for a laminate of alumina green sheets (see Patent Documents 2 and 3). However, a ceramic sheet manufactured as an electrolyte sheet for SOFC needs to satisfy the very high requirements as described above. Therefore, if the conventional manufacturing method used for the alumina substrate is used as it is, problems such as dimensional anomalies, cracks and chips occur, and the yield is considered to decrease.

  Therefore, the present inventor has reached the following present invention in consideration of all the above points.

The method for producing the ceramic sheet of the present invention comprises:
(I) On the ceramic setter, the ceramic porous spacer and the green sheet for the ceramic sheet are alternately arranged so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the outer edge of the green sheet is Stacking the ceramic porous spacer and the green sheet so as to be positioned on the inner side within a range of 0.5 mm to 10.0 mm from the outer edge of the ceramic porous spacer; and
(II) fixing the entire multilayer body by bonding the ceramic porous spacers constituting the multilayer body with at least a part of the side end surfaces of the spacers;
(III) firing the green sheet in the state of the laminate;
including.

  In the manufacturing method of the present invention, in the step (II), the ceramic porous spacers constituting the laminated body are joined and fixed, so that the green sheet sandwiched therebetween is also fixed integrally with the spacer. . Therefore, the laminate does not shift or collapse. Further, in the step (I), the laminated body has the ceramic porous spacer and the green sheet positioned on the inner side in the range where the outer edge of the green sheet is 0.5 mm or more and 10.0 mm or less than the outer edge of the ceramic porous spacer. It is formed by being stacked. That is, the outer edge of the ceramic porous spacer constitutes the side end surface of the laminate. Therefore, even when a chemical substance such as an adhesive is used as a means for fixing the entire laminate, only the spacer contacts the means, and the green sheet itself does not contact the means. Therefore, the green sheet can be fired without being contaminated by any means used for fixing the laminate (for joining the separators). As a result, the ceramic sheet can be manufactured with a high yield.

It is sectional drawing which shows the laminated body which consists of a ceramic porous spacer and the green sheet for ceramic sheets produced in process (I) of the manufacturing method of this invention. In process (II) of the manufacturing method of this invention, it is sectional drawing which shows the state by which the side end surfaces of the ceramic porous spacer were mutually joined by the adhesive tape. (A)-(e) is a top view which shows the number of the adhesive tapes of the state seen from the ceramic porous spacer of the uppermost layer of the laminated body, or the lowest layer, respectively, and its position. It is a top view which shows the application | coating position of the wax of the state seen from the ceramic porous spacer of the uppermost layer or lowermost layer of a laminated body. In Example 3, it is a figure for demonstrating the position on the green sheet which adheres wax.

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

The method for producing the ceramic sheet of the present embodiment is as follows:
(I) On the ceramic setter, the ceramic porous spacer and the green sheet for the ceramic sheet are alternately arranged so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the outer edge of the green sheet is Stacking the ceramic porous spacer and the green sheet so as to be positioned on the inner side within a range of 0.5 mm to 10.0 mm from the outer edge of the ceramic porous spacer; and
(II) fixing the entire multilayer body by bonding the ceramic porous spacers constituting the multilayer body with at least a part of the side end surfaces of the spacers;
(III) firing the green sheet in the state of the laminate;
including.

  First, the ceramic sheet green sheet used in step (I) will be described by taking an SOFC electrolyte sheet as an example. The green sheet for the electrolyte sheet for SOFC used in the manufacturing method of the present embodiment includes, for example, a binder and a solvent added to the ceramic electrolyte raw material powder, and further, a dispersant, a plasticizer, and a lubricant as necessary. And an antifoaming agent or the like is added to prepare a slurry, and the green tape obtained by forming the slurry into a tape shape and drying it is cut and punched into a predetermined shape.

Examples of the ceramic electrolyte 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 , 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 ; Examples thereof include zirconia powder containing one or more selected from oxides such as Bi 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.

  As the ceramic electrolyte raw material powder, ceria-based ceramic material powder and lanthanum gallate-based ceramic material powder can also be used. Examples of the ceria-based ceramic material include ceria doped with yttria, samaria and / or gadria. As lanthanum gallate ceramic materials, lanthanum gallate and a part of lanthanum gallium and / or gallium are replaced with strontium, calcium, barium, magnesium, aluminum, indium, cobalt, iron, nickel, and / or copper, etc. Can be mentioned.

  The green sheet for the SOFC electrolyte sheet used in the present embodiment is produced using the ceramic electrolyte raw material powder as described above.

  The ceramic powders that are the main material of the ceramic sheet include alumina powder, titania powder, magnesia powder, aluminum nitride powder, borosilicate glass powder, cordierite powder, mullite powder, and these two types. A composite powder comprising the above can be mentioned. In addition, zirconia powder, ceria powder, and lanthanum gallate powder can be used as the ceramic powder.

Alumina-based powder is particularly preferable as a material for a ceramic sheet for an electronic substrate for forming a circuit or mounting an electronic element, and an aluminum nitride-based powder is particularly preferable as a heat dissipation / insulating substrate. Examples of the alumina-based powder include alumina alone, oxides of alkaline earth metals such as MgO, CaO, SrO and BaO, oxides of rare earth elements such as Y ₂ O ₃ , La ₂ O ₃ and CeO ₂ , Y ₂ Zirconia stabilized with oxides of rare earth elements such as O ₃ , La ₂ O ₃ and CeO ₂ , oxides such as SiO ₂ , K ₂ O and B ₂ O ₃ that easily form glass during sintering, Na Examples thereof include powders made of alumina ceramics containing one or more glass components such as ₂ O ₃ —SiO ₂ —MgO glass. Examples of the aluminum nitride powder include only aluminum nitride, oxides of alkaline earth metals such as MgO, CaO, SrO and BaO, oxides of rare earth elements such as Y ₂ O ₃ , La ₂ O ₃ and CeO ₂ May be a powder made of an aluminum nitride-based ceramic containing one kind or two or more kinds.

  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, 2-ethylhexyl from the viewpoint of green sheet moldability and strength, especially thermal decomposability when mass-baking 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 various alkyl groups; hydroxyethyl acrylate, hydroxypropyl acetate Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having a hydroxyalkyl group such as rate, 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 ceramic raw material powder, binder, solvent, etc., is formed into a tape shape by a usual method, for example, a doctor blade method, an extrusion molding method or a calender roll method, etc. The green sheet for ceramic sheets is producible by cut | disconnecting to the shape of this. In addition, the process of roughening the surface of a green sheet may be included as needed. The size and thickness of the green sheet are determined from the shape, size and thickness of the target ceramic sheet and the shrinkage rate due to firing.

In the case of an electrolyte sheet for SOFC, the green sheet used in the manufacturing method of the present embodiment is such that the finally obtained electrolyte sheet has an area of 50 to 1000 cm ² and 0.05 to 0.5 mm. It is preferred to have a size and thickness so as to have a thickness.

  The shape of the green sheet is not particularly limited because it may be appropriately determined according to the use, for example, in the case of an electrolyte sheet, according to the shape of the SOFC 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 such that the ceramic porous spacer is arranged 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. As shown in FIG. 1, the laminated body 1 is stacked so that the outer edge of the green sheet 11 is positioned inside the outer edge of the ceramic porous spacer 12 within a range of 0.5 mm to 10.0 mm. By forming the laminate 1 in this way, in the subsequent step, the ceramic porous spacers are joined to each other at least at a part of their side end faces, and the means for joining is fixed when fixing the entire laminate. It can suppress that (for example, an adhesive etc.) contaminates a green sheet. Therefore, the green sheet can be fired without being affected by the joining means, regardless of which joining means is used for fixing the laminate. As a result, problems (such as dimensional anomalies, cracks and chips) that occur in the resulting electrolyte sheet are suppressed, and the stability when stacking the ceramic porous spacer and the green sheet is improved. In order to obtain these effects more reliably, the outer edge of the green sheet 11 is preferably located on the inner side in the range of 1.0 to 8.0 mm than the outer edge of the ceramic porous spacer 12, More preferably, it is located on the inner side within a range of 6.0 mm.

  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 these are excellent in creep resistance and spalling resistance. Furthermore, since these have low reactivity with zirconia in a high temperature atmosphere, they are suitable as spacers when firing zirconia green sheets.

  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 the green sheet is fired in a state where the ceramic porous spacer and the green sheet are alternately stacked, the organic porous component such as a binder, a plasticizer, and a dispersing agent This is because the degreasing effect can be promoted by quickly releasing the gas component generated by the thermal decomposition to the outside. 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 green sheet is less likely to be efficiently diffused, and undulation and warpage tend 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 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).

  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, the ceramic porous spacer constituting the laminated body is bonded to each other at at least a part of the side end face of the spacer, thereby fixing the entire laminated body (step (II)). The means used for joining the ceramic porous spacers is not particularly limited. For example, a method of bonding ceramic porous spacers constituting a laminated body to each other using an adhesive tape at least at a part of the side end surface thereof, or a ceramic porous spacer constituting a laminated body on the side A method in which at least a part of the end faces are bonded to each other using wax can be suitably used.

  The case where ceramic porous spacers are joined to each other by using an adhesive tape at their side end surfaces will be described. As shown in FIG. 2, the adhesive tape 2 is, for example, from the upper surface 13 of the uppermost ceramic porous spacer 12 a of the laminate 1 to the lower surface of the lowermost ceramic porous spacer 12 b along the side end surface of the laminate 1. By passing up to 14, the side end surfaces of the ceramic porous spacer 12 can be joined to each other.

  There is no particular limitation on the number of pressure-sensitive adhesive tapes that are attached to bond the side end surfaces of the ceramic porous spacers to each other and the position where the pressure-sensitive adhesive tapes are attached. For example, when moving the laminated body to the firing furnace, the size of the laminated body (height and ceramic porous spacer) can be controlled so that the laminated body can be prevented from shifting or collapsing with a weak force applied to the laminated body. The number of adhesive tapes and the position of the adhesive tape may be appropriately determined in consideration of the area), the adhesive strength of the adhesive tape used, the material of the ceramic porous spacer, and the like. However, in consideration of work efficiency, it is preferable that the number of adhesive tapes to be attached is as small as possible. Therefore, the number of adhesive tapes is preferably determined in consideration of work efficiency.

  In the case where the ceramic porous spacer is rectangular, for example, an adhesive tape may be affixed to each corresponding position of a pair of opposing sides. Specifically, as shown in FIGS. 3A to 3D, two, four, six, or eight places of the ceramic porous spacer 12 may be fixed with the adhesive tape 2. Moreover, as shown in FIG.3 (e), it is also possible to affix the adhesive tape 2 in the position which respectively respond | corresponds about two sets of sides | sides which the ceramic porous spacer 12 opposes. When the ceramic porous spacer is circular, for example, one set or two or more sets of adhesive tapes may be affixed to opposing positions.

  The ratio of the total line width of the applied adhesive tape to the outer edge length of the ceramic porous spacer (total line width of the adhesive tape / outer edge length of the spacer) is in the range of 1/100 to 50/100. Is preferable, and the range of 4/100 to 20/100 is more preferable. By setting it as 1/100 or more, the fixing force of the whole laminated body can be sufficiently obtained. By setting it to 50/100 or less, it is possible to suppress a decrease in work efficiency, and it is also possible to suppress problems such as warping and cracking of the electrolyte sheet that occur when the entire laminate is too firmly fixed.

  For the base material of the adhesive tape, for example, cellophane, kraft paper, cloth, aluminum foil, polyester film, polyethylene and polyimide film can be used. As the adhesive of the adhesive tape, a rubber adhesive, an acrylic adhesive, and a silicone adhesive can be used. As an adhesive tape, the commercial adhesive tape which consists of these base materials and an adhesive is preferable from availability.

  Next, a case where ceramic porous spacers are bonded to each other using wax on the side end surfaces of the spacers will be described. As shown in FIG. 4, the side end surfaces of the ceramic porous spacer 12 are joined together by applying the wax 3 to the side end surfaces of the laminate 1. As described above, the outer edge of the green sheet is located 0.5 mm or more inside the side end surface of the laminate 1 formed by the side end surface of the ceramic porous spacer 12. With such a configuration, it is possible to prevent the wax 3 applied to the side end surface of the laminate 1 from contaminating the green sheet. The application position of the wax 3 is not limited to the position shown in FIG. 4 and may be appropriately selected so that the entire laminate can be firmly fixed to the extent that displacement and collapse do not occur.

  As the wax used here, a general wax can be used. Among these, the softening point by thermomechanical analysis (TMA) is preferably 30 to 100 ° C. (preferably 35 to 80 ° C., more preferably 40 to 40 ° C.) for fixing the laminate composed of the ceramic porous spacer and the green sheet. And a melt viscosity at 100 ° C. of 100 to 4000 mPa · s (preferably 300 to 3000 mPa · s, more preferably 500 to 2000 mPa · s). Wax having such characteristics melts quickly when the temperature inside the furnace reaches a desired temperature (a specific temperature at which the green sheet is fired) during firing of the laminate, but the laminate is strengthened until near the desired temperature. Can be fixed. Furthermore, the wax having a relatively high melt viscosity as described above is very unlikely to flow into the laminated body after fusing and contaminate the green sheet. For these reasons, a wax that satisfies the above characteristics is preferably used in the manufacturing method of the present embodiment. The molecular weight of the wax is preferably in the range of 1,000 to 100,000, more preferably in the range of 10,000 to 80,000, and still more preferably in the range of 20,000 to 60,000.

  Next, the green sheet is fired in the state of the laminate (step (III)). Specific firing conditions are not particularly limited. Therefore, it is possible to use a normal method for firing the green sheet. For example, in order to remove organic components such as a binder and a plasticizer from the green sheet, the treatment is performed at 150 to 600 ° C., preferably 250 to 500 ° C. for about 5 to 80 hours. Next, the ceramic sheet is obtained by firing at 1000 to 1800 ° C., preferably 1200 to 1600 ° C. for 2 to 10 hours in an oxidizing atmosphere or a non-oxidizing atmosphere.

  The ceramic sheet obtained by the manufacturing method of the present embodiment has strict demands as an electrolyte sheet for SOFC because the occurrence of dimensional abnormality, warpage and waviness abnormality, appearance abnormality (occurrence of scratches, etc.), cracking and chipping is suppressed. It satisfies. That is, the manufacturing method of the present embodiment is a method capable of manufacturing a ceramic sheet with a high yield.

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

Example 1
In Example 1, an example in which an adhesive tape is used for joining ceramic porous spacers will be described. In this example, a zirconia-based electrolyte sheet was manufactured as an SOFC electrolyte sheet.

(1) Manufacture of zirconia-based green sheet As raw material powder, it consists of a methacrylic copolymer with respect to 100 parts by mass of commercially available 8 mol% yttrium oxide-stabilized zirconia powder (d ₅₀ (average particle size): 0.5 μm). Binder (number average molecular weight: 100,000, glass transition temperature: −8 ° C.) 16 parts by mass in terms of solid content, 2 parts by mass of sorbitan acid trioleate as a dispersant, 3 parts by mass of dibutyl phthalate as a plasticizer, toluene as a solvent 50 parts by mass of a mixed solvent of / isopropanol (mass ratio = 3/2) was placed in a nylon mill charged with zirconia balls, and milled for 40 hours to prepare a slurry. The obtained slurry was transferred to a jacketed round bottom cylindrical vacuum degassing vessel equipped with a bowl-shaped stirrer and having an internal volume of 50 L. While rotating the stirrer at a speed of 30 rpm, the jacket temperature was reduced to 40 ° C. (about 4 ° C.). To 21 kPa), and the viscosity at 25 ° C. was adjusted to 3 Pa · s to obtain a coating slurry. The slurry for coating is continuously coated on a polyethylene terephthalate (PET) film by a doctor blade method, and then dried at 40 ° C., 80 ° C., and 110 ° C., thereby making untreated green for a long solid electrolyte. A body (green tape) was obtained. The green tape is peeled off from the PET film and 350 KN using a 1000 KN 4-column test press machine (manufactured by Osaka Jack Mfg. Co., Ltd.) equipped with a cardboard having an average surface roughness Ra of 3.5 μm and a thickness of 0.3 mm. For 2 seconds. Thereafter, this green tape was punched with a punching die to obtain a square green sheet having a side of 132 mm. The thickness of the obtained green sheet was 215 μm.

(2) Preparation of Ceramic Porous Spacer A square alumina spacer having a side of about 138 mm was used as the ceramic porous spacer. This alumina spacer had a thickness of 0.3 mm and a porosity of 45%.

(3) Production of Laminate 10 zirconia green sheets produced as described above and 11 alumina spacers were prepared. Alumina spacers and zirconia green sheets were alternately stacked so that the alumina spacers were disposed in the lower layer and the uppermost layer. At this time, the laminated body was produced by stacking the zirconia green sheet so that the outer edge of the zirconia-based green sheet was located approximately 3.0 mm inside the outer edge of the alumina spacer.

(4) Fixing of laminate A commercially available adhesive tape having a width of 24 mm and a commercially available adhesive tape having a width of 50 mm were prepared. Each of these was cut into a length of 30 mm and pasted at a predetermined position of the laminate obtained in the above (3) to fix the entire laminate. The fixed positions (positions where the tape is attached) are as shown in Table 1.

(5) Firing A 1.6 mm thick ceramic porous body (weight) was separately placed on the laminate fixed with a commercially available adhesive tape. This was placed on a 150 mm square alumina calcining setter and calcined at a maximum temperature of 1400 ° C. for 3 hours in a continuous tunnel calcining furnace having a continuous degreasing furnace.

  In addition, in a present Example, the width | variety of 1-1 to 1-4 manufactured on the mutually different conditions by changing the width | variety of the tape used for fixation, a fixing position, and the number of the weights at the time of baking. Four samples were obtained. Table 1 shows the width of the tape used for fixing, the fixing position, and the number of weights for the samples Nos. 1-1 to 1-4. Moreover, the sheet | seat (number 1-5) used as a comparative example was also produced in the same procedure as the numbers 1-1 to 1-4 except the point which did not fix with a tape.

Table 1 shows various test results and yields of the sheets obtained after firing. In this example, a dimensional inspection and a warpage inspection using a CCD inspection apparatus were performed as a jig inspection. Visual inspection was further performed on the sheet that passed the jig inspection. As an appearance inspection, each item shown in Table 2 was also inspected. The evaluation criteria for each item of appearance inspection are as follows.
Dimple / swell: 5% of the fired product (sheet) is extracted, and the thickness about 15 mm inside from the outer edge of the sheet is measured at two points to determine the average thickness of the sheet. A gap was set to this average thickness +20 μm, and a sheet was inserted into the gap, and if the sheet could be inserted into the gap, the test was accepted.
Cracks, chips, cracks: Accepted unless visually recognized.
Scratches / spots / adherents: Accepted unless visually recognized. However, below the limit sample was allowed.

  The ratio of the number of acceptable appearance inspections to the number of fired sheets was calculated, and the obtained value was taken as the overall yield.

  As shown in Tables 1 and 2, when the laminate was fixed using tapes having a tape width of 24 mm and 50 mm, both were compared with the comparative example (No. 1-5) in which the laminate was not fixed. The dimensional pass rate, warpage pass rate, and appearance pass rate of the obtained sheet were all equal or higher. From this result, it was confirmed that the yield is improved by fixing the entire laminate with the tape.

(Example 2)
In Example 2, as in Example 1, an example in which an adhesive tape is used for joining ceramic porous spacers will be described. In this example, a lanthanum gallate electrolyte sheet was manufactured as an electrolyte sheet for SOFC.

(1) Production of lanthanum gallate green sheet La _0.9 Sr _0.1 Ga _0.8 Mg _0.2 O _3-δ powder (average particle size: 0.7 μm, specific surface area: 10 m ² / g, hereinafter referred to as LSGM as electrolyte powder) .) 100 parts by mass of a binder comprising a methacrylate copolymer (number average molecular weight: 80,000, glass transition temperature: −15 ° C., solid content concentration: 50% by mass) in terms of solid content is 20 parts by mass. Then, 2.2 parts by mass of dibutyl phthalate and 50 parts by mass of a mixed solvent of toluene / isopropanol (mass ratio: 3/2) were added as a plasticizer, and a coating slurry was prepared in the same manner as in Example 1. The slurry for coating is continuously coated on a polyethylene terephthalate (PET) film by a doctor blade method, and then dried at 40 ° C., 80 ° C., and 110 ° C., thereby making untreated green for a long solid electrolyte. A body (green tape) was obtained. This green tape is peeled off from the PET film and 150 KN using a 1000 KN 4-column test press machine (manufactured by Osaka Jack Mfg. Co., Ltd.) equipped with a thick paper having an average surface roughness Ra of 5.3 μm and a thickness of 0.4 mm. For 1 second. Thereafter, this green tape was punched with a punching die to obtain a square green sheet having a side of 132 mm. The thickness of the obtained green sheet was 300 μm.

(2) Preparation of Ceramic Porous Spacer A square alumina spacer having a side of about 138 mm was used as the ceramic porous spacer. This alumina spacer had a thickness of 0.3 mm and a porosity of 50%.

(3) Production of Laminate Eight lanthanum gallate green sheets produced as described above and nine alumina spacers were prepared. Alumina spacers and lanthanum gallate green sheets were alternately stacked so that the alumina spacers were arranged in the lower layer and the uppermost layer. At this time, the lanthanum gallate green sheet was stacked so that the outer edge of the lanthanum gallate green sheet was located approximately 3.0 mm inside the outer edge of the alumina spacer, thereby producing a laminate.

(4) Fixing of laminate A commercially available adhesive tape having a width of 24 mm and a commercially available adhesive tape having a width of 50 mm were prepared. Each of these was cut into a length of 30 mm and pasted at a predetermined position of the laminate obtained in the above (3) to fix the entire laminate. The fixed positions (positions where the tape is attached) are as shown in Table 3.

(5) Firing A 1.6 mm thick ceramic porous body (weight) was separately placed on the laminate fixed with a commercially available adhesive tape. This was placed on a 150 mm square alumina calcining setter and calcined at a maximum temperature of 1480 ° C. for 3 hours in a continuous tunnel calcining furnace having a continuous degreasing furnace.

  In addition, in a present Example, the width | variety of the tape used for fixation, a fixing position, and the number of the weights at the time of baking were changed, and the numbers 2-1 to 2-4 manufactured on the mutually different conditions Four samples were obtained. Table 3 shows the width of the tape used for fixing, the fixing position, and the number of weights for the samples of numbers 2-1 to 2-4. Moreover, the sheet | seat (number 2-5) used as a comparative example was also produced in the procedure similar to number 2-1 to 2-4 except the point which did not fix with a tape.

  The sheet obtained after firing was inspected in the same manner as in Example 1, and various inspection results and yields are shown in Table 3. Table 4 shows the results of the appearance inspection.

  As shown in Tables 3 and 4, when the laminate was fixed using tapes having a tape width of 24 mm and 50 mm, both were compared with the comparative example (No. 2-5) in which the laminate was not fixed. The dimensional pass rate, warpage pass rate, and appearance pass rate of the obtained sheet were all equal or higher. From this result, it was confirmed that the yield is improved by fixing the entire laminate with the tape.

(Example 3)
In Example 3, the effect of these waxes on the green sheet was examined using various waxes.

  First, a zirconia green sheet was prepared in the same manner as in Example 1. Also, as wax, “Paraffin Wax No. 155” manufactured by Nippon Seiki Co., Ltd., “Microcrystalline Wax 1045” manufactured by the same company, “Microcrystalline Wax 2045” manufactured by the same company, and “Polymer Wax” manufactured by Nippon Shokubai Co., Ltd. ST-100 "was prepared. The characteristics of each wax are as shown in Table 5.

  As shown in FIG. 5, four waxes were prepared by attaching wax to nine locations A to I on the surface of the green sheet 11 as shown in FIG. These four sheets were stacked on top of each other, and a ceramic porous body (weight) having a thickness of 1.6 mm was placed on the top and fired at 1400 ° C. About the item shown in Table 6, it evaluated visually about the sheet | seat after baking. The criteria for evaluation of each item are the same as those in Example 1.

  From the above results, “Polymer Wax ST-100” of No. 3-4 having a softening point in the range of 30 to 100 ° C. and a melt viscosity at 100 ° C. in the range of 100 to 4000 mPa · s. However, the effect on the green sheet was the smallest, and it was confirmed that the wax is optimum as the wax used in the production method of the present invention.

Example 4
In Example 4, an example in which wax is used for bonding ceramic porous spacers will be described. In Example 4, a wax (“Polymer Wax ST-100” manufactured by Nippon Shokubai Co., Ltd.) obtained with good results in Example 3 was used.

  “Manufacture of zirconia green sheet”, “Preparation of ceramic porous spacer”, and “Preparation of laminate” were the same as those in Example 1, and thus description thereof is omitted here.

  As shown in FIG. 4, “Polymer Wax ST-100” manufactured by Nippon Shokubai Co., Ltd. was applied to four locations on the side end face of the laminate. Specifically, a wax having a temperature of 60 ° C. to 76 ° C. was included in a kitchen sponge, and the wax was applied to the laminated body by pressing the sponge against four locations on the side end surface of the laminated body for several seconds. . In this way, 12 laminates coated with wax were prepared. The twelve laminates were assigned numbers 4-1-1 to 4-1-12, respectively, and the weight of the applied wax was measured. The results are as shown in Table 7.

  Moreover, the laminated body (number 4-2) as a comparative example which is the same as the laminated body of number 4-1-1 to 4-1-12 except the point to which the wax is not apply | coated was also prepared. The laminates of numbers 4-1-1 to 4-1-12 and 4-2 were fired under the following conditions.

  A ceramic porous body (weight) having a thickness of 1.6 mm was separately placed on the laminate fixed with the polymer wax. This was placed on a 150 mm square alumina calcining setter and calcined at a maximum temperature of 1400 ° C. for 3 hours in a continuous tunnel calcining furnace having a continuous degreasing furnace.

  About the sheet | seat obtained by baking, the jig | tool test | inspection (dimension test | inspection) and the external appearance inspection by visual observation were performed. Table 8 shows the inspection results, and Table 9 shows the detailed results of the appearance inspection. The criteria for evaluation of each item are the same as those in Example 1.

  From the above results, it was confirmed that the yield in producing the electrolyte sheet was improved by fixing the entire laminate using an adhesive tape or wax as in the production method of the present invention.

  Since the method for producing an electrolyte sheet for SOFC of the present invention can produce a good quality electrolyte sheet with a good yield, it can be suitably used for producing an electrolyte sheet made of a particularly expensive material.

DESCRIPTION OF SYMBOLS 1 Laminated body 2 Adhesive tape 3 Wax 11 Green sheet 12 Ceramic porous spacer 12a Top layer ceramic porous spacer 12b Bottom layer ceramic porous spacer 13 Upper surface of top layer ceramic porous spacer 14 Bottom layer ceramic porous spacer Underside of

Claims (3)

(I) On the ceramic setter, the ceramic porous spacer and the green sheet for the ceramic sheet are alternately arranged so that the ceramic porous spacer is disposed in the lowermost layer and the uppermost layer, and the outer edge of the green sheet is Stacking the ceramic porous spacer and the green sheet so as to be positioned on the inner side within a range of 0.5 mm to 10.0 mm from the outer edge of the ceramic porous spacer; and
(II) fixing the entire multilayer body by bonding the ceramic porous spacers constituting the multilayer body with at least a part of the side end surfaces of the spacers;
(III) firing the green sheet in the state of the laminate;
A method for producing a ceramic sheet, comprising: In the step (II), the ceramic porous spacers constituting the laminated body are joined to each other by using an adhesive tape at at least a part of the side end surfaces of the spacers.
The method for producing a ceramic sheet according to claim 1. In the step (II), the ceramic porous spacers constituting the laminate are joined to each other using wax at at least a part of the side end surfaces of the spacers,
The method for producing a ceramic sheet according to claim 1.

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