JP6371216B2 - Electrolyte sheet for solid oxide fuel cell - Google Patents

Description

  The present invention provides an electrolyte sheet for a solid oxide fuel cell, a single cell for a solid oxide fuel cell including the electrolyte sheet for a solid oxide fuel cell, and an electrolyte sheet for the solid oxide fuel cell. And a method for producing the electrolyte sheet for a solid oxide fuel cell.

  Fuel cells are attracting attention as a clean energy source. Improvements and practical application studies are being rapidly promoted mainly for household power generation, commercial power generation, and automobile power generation. Among such fuel cells, a solid oxide fuel cell (hereinafter sometimes abbreviated as “SOFC”) has high power generation efficiency and excellent long-term stability, and is expected as a power source for home use and business use. ing.

  In this SOFC, a ceramic sheet is generally used as a solid electrolyte. Ceramics are superior in electrical properties and magnetic properties in addition to mechanical properties such as heat resistance. Among them, a ceramic sheet mainly composed of zirconia is used as a solid electrolyte of SOFC because it has excellent oxygen ion conductivity, heat resistance, corrosion resistance, toughness and the like.

  SOFC solid electrolytes have been studied to increase the surface area from the viewpoint of improving power generation performance and improving adhesion to electrode layers. For example, Patent Document 1 describes a method of roughening the surface of a solid electrolyte sheet by blasting or etching. Patent Document 2 discloses a method of obtaining a ceramic sheet having a roughened surface by pressing a metal mesh against the surface of a green sheet and then roughening the metal sheet. Patent Document 3 describes a method of obtaining a surface roughened ceramic sheet by pressing a green sheet sandwiched between roughening sheets, transferring the roughened surface, and firing. Patent Document 4 discloses a method of obtaining a surface roughened ceramic sheet by firing a green sheet obtained by casting a slurry containing an electrolyte material on a roughened polymer film.

  However, the above technique has a problem that the ceramic sheet is cracked or the mechanical strength is lowered. Therefore, the present inventors have developed a method of manufacturing a SOFC electrolyte sheet having a similar depression or protrusion by pressing a stamper having a depression or protrusion having a specific shape against the green sheet (Patent Document 5). .

JP-A-1-227362 Japanese Patent Laid-Open No. 9-55215 JP 2007-313650 A JP 2002-42831 A International Publication No. 2010/110395 Pamphlet

  As described above, the present inventors have developed a high-performance SOFC electrolyte sheet having a relatively large surface area and also having a stable mechanical strength.

  However, we found room for improvement in production efficiency. Specifically, the SOFC electrolyte sheet is manufactured by pressing a stamper having a specific shape of depression or protrusion onto the green sheet, but the stamper may not be quickly peeled off from the green sheet after pressing. In such a case, the manufacturing efficiency may be reduced, for example, the manufacturing must be temporarily stopped in continuous mass production.

  Accordingly, the present invention provides an electrolyte sheet for a solid oxide fuel cell that has a relatively large surface area, excellent power generation performance and adhesion to an electrode layer, has a relatively high mechanical strength, and has a high production efficiency. The purpose is to provide. Another object of the present invention is to provide a stamper for producing the solid oxide fuel cell electrolyte sheet and a method for producing the same.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it was found that the surface roughness at the bottom of the depression or the top of the protrusion has a great influence on the releasability during the production of the SOFC electrolyte sheet having a depression or protrusion having a specific shape. The present invention has been completed.

  Hereinafter, the present invention will be described.

[1] having at least two depressions and / or protrusions on at least one side;
The basal plane shape of the depressions and protrusions is a circle, an ellipse, or a rounded polygon in which the shape of the apex is a curve having a curvature radius of 0.1 μm or more, and / or the three-dimensional shape thereof is a hemisphere , A semi-elliptical sphere, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a curvature radius of 0.1 μm or more,
The average equivalent circle diameter of the basal plane of the depression and protrusion is 0.5 μm or more and 250 μm or less,
The average depth of the depression and the average height of the protrusions are 0.3 μm or more and 50 μm or less,
The surface roughness Ra of the depressions and protrusions is 0.01 μm or more and 3 μm or less, and
An electrolyte sheet for a solid oxide fuel cell, having an average thickness of 30 μm to 400 μm.

[2] The electrolyte sheet for a solid oxide fuel cell according to the above [1], wherein the depressions and / or protrusions are 500 / cm ² or more and 500,000 / cm ² or less.

[3] At least one surface has a region having the above-described depression and / or protrusion of 500 / cm ² or more and less than 50,000 / cm ² and 50,000 / cm ² or more and 500,000 / cm ² or less. The electrolyte sheet for a solid oxide fuel cell according to the above [1], having a region.

  [4] A unit cell for a solid oxide fuel cell, comprising the electrolyte sheet for a solid oxide fuel cell according to any one of [1] to [3].

[5] A stamper for forming depressions and / or protrusions on the electrolyte green sheet,
Have two or more depressions and / or protrusions,
The basal plane shape of the depressions and protrusions is a circle, an ellipse, or a rounded polygon in which the shape of the apex is a curve having a curvature radius of 0.1 μm or more, and / or the three-dimensional shape thereof is a hemisphere , A semi-elliptical sphere, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a curvature radius of 0.1 μm or more,
The average equivalent circle diameter of the basal plane of the depression and protrusion is 0.8 μm or more and 380 μm or less,
The average depth of the depression and the average height of the protrusions are 1.1 μm or more and 186 μm or less, and
A stamper having a surface roughness Ra of the depressions and protrusions of 0.01 μm or more and 10 μm or less.

[6] The stamper according to the above [5], wherein the depressions and / or protrusions are 500 / cm ² or more and 500,000 / cm ² or less.

[7] It has a region having the above depressions and / or protrusions of 500 / cm ² or more and less than 50,000 / cm ^{2 and} a region having 50,000 / cm ² or more and 500,000 / cm ² or less. The stamper according to [5] above.

[8] A method for producing an electrolyte sheet for a solid oxide fuel cell,
Obtaining a surface-modified electrolyte green sheet in which depressions and / or protrusions are formed by pressing the stamper according to any one of the above [5] to [7] on one or both surfaces of the electrolyte green sheet; and
A method comprising firing the surface-modified electrolyte green sheet.

  Since the electrolyte sheet for a solid oxide fuel cell according to the present invention has a plurality of depressions and / or protrusions having a specific shape on at least one surface, the surface area is relatively large. Moreover, when an electrode layer is formed on the electrolyte sheet, the adhesiveness with the electrode layer is high. Therefore, the solid oxide fuel cell unit cell according to the present invention including the solid oxide fuel cell electrolyte sheet according to the present invention has a large area for electrode reaction, and thus has excellent power generation performance and durability. Is also expensive. Furthermore, since the depression and / or protrusion has a specific shape, the solid oxide fuel cell electrolyte sheet according to the present invention has high mechanical strength. In addition, in the case where depressions and / or protrusions are formed in the electrolyte green sheet using a stamper, since the mold release property is excellent, the production efficiency of the electrolyte sheet for a solid oxide fuel cell according to the present invention is high. Therefore, the present invention is extremely useful industrially as being suitable for industrial mass production of electrolyte sheets for solid oxide fuel cells.

It is a schematic diagram which shows an example of the electrolyte sheet which concerns on this invention. It is a schematic diagram which shows the state which pressed the stamper to the electrolyte green sheet.

  The present invention is described in detail below, but is not limited to the following unless it is contrary to the gist of the present invention. Hereinafter, the electrolyte sheet for a solid oxide fuel cell according to the present invention will be described first.

1. Electrolyte sheet for solid oxide fuel cell The electrolyte sheet for solid oxide fuel cell according to the present invention (hereinafter simply referred to as “electrolyte sheet”) has at least two depressions and / or protrusions on one side. And the basal plane shape of the depression and protrusion is a circle, an ellipse, or a rounded polygon in which the shape of the apex is a curve having a curvature radius of 0.1 μm or more, and / or the three-dimensional shape thereof is A hemispherical shape, a semi-elliptical sphere shape, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a radius of curvature of 0.1 μm or more, and the average equivalent circle diameter of the basal plane of the above-described depression and protrusion is 0.5 μm or more and 250 μm or less. And the average depth of the depressions and the average height of the protrusions are 0.3 μm or more and 50 μm or less, the surface roughness Ra of the depressions and protrusions is 0.01 μm or more and 3 μm or less, and the average thickness Saga 3 And wherein the at μm or 400μm or less. By forming the depressions and / or protrusions in the electrolyte sheet, the electrolyte sheet has a large interface area with the electrode layer, high adhesion with the electrode layer, excellent mechanical strength, and excellent manufacturing efficiency. Become.

  The electrolyte sheet according to the present invention has two or more depressions and / or protrusions on at least one side thereof.

  Here, “at least one side” means one side or both sides of the electrolyte sheet. Preferably, the electrolyte sheet has two or more depressions and / or protrusions on both sides thereof. Generally, in a single cell for a solid oxide fuel cell, a fuel electrode layer is formed on one side of an electrolyte sheet, and an air electrode layer is formed on the other side. Therefore, by forming depressions and / or protrusions on both sides, In addition, the contact area with each electrode is increased, and as a result, the power generation performance and the adhesion with the electrode are improved.

  The electrolyte sheet according to the present invention may have both the depression and the protrusion, but preferably has one of the depression or the protrusion, and more preferably has only the depression.

  More specifically, as an aspect of the electrolyte sheet of the present invention, an aspect having a plurality of depressions on one side; an aspect having a plurality of protrusions on one side; an aspect having a plurality of depressions and protrusions on one side; An embodiment having a plurality of depressions and projections on both sides; and an embodiment having a plurality of depressions and projections on both sides. Among these, a mode having a plurality of depressions on one or both sides is preferable, and a mode having a plurality of depressions on both sides is more preferable.

  The three-dimensional shape of the depressions and protrusions is a hemisphere, a semi-elliptical sphere, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a curvature radius of 0.1 μm or more.

In the present invention, “hemisphere” and “semi-elliptical sphere” are a shape in which a sphere and an ellipsoid are cut by a cross section including the center, or a shape that does not include the center among the sections cut by a cross section perpendicular to a line passing through the center. Say. That is, the “hemisphere” and “semi-elliptical sphere” are not limited to a sphere and a shape obtained by cutting an ellipsoid in half, and also include a substantially hemispherical shape and a substantially semi-elliptical spherical shape. In the present invention, the term “ellipsoid” means x ² / a ² + y ² / b ² + z ² / c ² = 1 [where a, b and c are the x-axis, y-axis and z-axis directions, respectively. It corresponds to a half length of the diameter of] and is a solid surrounded by an ellipsoid.

  In the present invention, “a polyhedron whose cross-sectional shape of a vertex and a ridge is a curve having a curvature radius of 0.1 μm or more” is a polyhedron such as a cylinder, a cone, a truncated cone, a prism, a pyramid, a combination of these, or the like as a basic shape. The cross-sectional shape of the apex portion and the ridge portion of the polyhedron is formed into a shape represented by a curve having a curvature radius of 0.1 μm or more. In addition, when employ | adopting the said polyhedral shape, it is preferable that the cross-sectional shape of all the vertices and ridges which the polyhedron has is formed in the shape represented by the curve with a curvature radius of 0.1 micrometer or more. The occurrence of cracks in the electrolyte sheet can be further reduced by making the three-dimensional shape of depressions and protrusions into a shape having no corners.

  In the above-mentioned hemispherical shape, semi-elliptical spherical shape, or polyhedron whose apex and ridge cross-section is a curve having a curvature radius of 0.1 μm or more, the cross-sectional area of the basal plane is the largest, and the cross-sectional area is toward the bottom of the depression or the top of the protrusion Gradually becomes smaller. The three-dimensional shape is preferably a hemispherical shape or a semi-elliptical spherical shape, and more preferably a hemispherical shape.

  The basal plane shape of the depressions and protrusions is a circle, an ellipse, or a rounded polygon that is a curve having a radius of curvature of 0.1 μm or more at the apex. Here, the circular and elliptical shapes include so-called substantially circular and substantially elliptical shapes. In addition, “a rounded polygon whose shape of the vertex is a curve having a curvature radius of 0.1 μm or more” is a basic shape of a convex polygon or a concave polygon, and the vertex portion of the polygon has a curvature radius of 0. .Those formed in a shape represented by a curve of 1 μm or more. In addition, when employ | adopting the said rounded polygon, it is preferable that all the vertex parts which the polygon has are formed in the shape represented by the curve with a curvature radius of 0.1 micrometer or more. The occurrence of cracks in the electrolyte sheet can be further reduced by making the basal plane shape of the depressions and protrusions into a shape having no corners. The basal plane shape is preferably a circle or an ellipse, and more preferably a circle. The basal plane shape is the boundary between the base line and the depression or protrusion on the surface of the electrolyte sheet, that is, the outermost contour of the depression or protrusion, and can be confirmed using a laser microscope. Also, for example, when the depression is formed using a stamper as described later, the base line is the highest position of the stamper's imprint, and when the protrusion is formed using the stamper. The lowest position of the stamper stamp may be the baseline.

  The average equivalent circular diameter of the basal plane of the depression and protrusion is preferably 0.5 μm or more and 250 μm or less. When the average equivalent circle diameter is less than 0.5 μm, the adhesion with the electrode is deteriorated, and the electrode is liable to be peeled off during long-term use. On the other hand, when the average equivalent circle diameter exceeds 250 μm, the strength decreases as compared with an electrolyte sheet in which no depression or protrusion is formed. The average equivalent circle diameter is more preferably 5 μm or more, further preferably 15 μm or more, more preferably 200 μm or less, and further preferably 150 μm or less. In the present invention, the “average equivalent circle diameter” refers to the diameter of a circle having the same area as the area of the basal plane shape of the depression or protrusion. Specifically, the average equivalent circle diameter is a region of 5 μm or more and 2 mm or less on the electrolyte sheet surface and includes at least the center of the electrolyte sheet surface, and there are at least 50 depressions or protrusions. For the region, the basal plane shape area is measured for all the depressions and protrusions existing in the region, and the average area is obtained, and is the equivalent circle diameter calculated from the average area.

The value of the variation in equivalent circle diameter of the basal plane of the depression and protrusion, that is, the value of (standard deviation of equivalent circle diameter) / (average equivalent circle diameter) is preferably 0.25 or less, more preferably 0. .20 or less, more preferably 0.15 or less. If the variation value is within the above range, the average strength and the Weibull coefficient of the electrolyte sheet can be increased, and interfacial peeling from the electrolyte sheet of the electrode formed on the electrolyte sheet surface can be further suppressed. . The lower limit value of the variation value is 0. Here, the standard deviation of the equivalent circle diameter can be obtained by the following equation. In the formula, σ is the standard deviation, x is the equivalent circle diameter of the base shape of each depression or protrusion, x _ave is the average equivalent circle diameter, and n is the number of depressions and protrusions measured.

  The average depth of the depression and the average height of the protrusion are preferably 0.3 μm or more and 50 μm or less. When the average depth or average height is less than 0.3 μm, the adhesion with the electrode is deteriorated, and the electrode is liable to be peeled off during long-term use. On the other hand, when the average depth or average height exceeds 50 μm, the strength is reduced as compared with an electrolyte sheet in which no depressions and protrusions are formed. The average depth or average height is more preferably 1 μm or more, further preferably 3 μm or more, more preferably 40 μm or less, and further preferably 30 μm or less. In the present invention, the “average depth of depression” is an area of 5 μm or more and 2 mm or less on the surface of the electrolyte sheet and includes at least the center of the surface of the electrolyte sheet, and there are at least 50 depressions or protrusions. This is an average value calculated from these values by measuring the depth of all depressions existing in the region. The “depth of depression” is the distance from the baseline to the lowest position. In the present invention, the “average height of protrusions” is an average value calculated from these values by measuring the height of all protrusions existing in the area. Further, the “projection height” is the distance from the baseline to the highest position.

  The average depth of the depressions and the average height of the protrusions on one side is preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, and 33 or less as a ratio with respect to the sheet thickness of 100. Preferably, it is 25 or less, more preferably 20 or less. By setting the ratio of the average depth of the depression or the average height of the protrusion to the sheet thickness within the above range, the average strength and the Weibull coefficient of the electrolyte sheet can be increased, and the ratio is formed on the surface of the electrolyte sheet. Interfacial peeling from the electrolyte sheet of the electrode can be further suppressed.

  The value of the variation in the depth of the depression, that is, the value of (standard deviation of depth) / (average depth), and the value of the variation in the average height of the protrusion, ie, (standard deviation of height) / ( The value of (average height) is preferably 0.25 or less, more preferably 0.20 or less, and still more preferably 0.15 or less. If the variation value is within the above range, the average strength and Weibull coefficient of the electrolyte sheet can be increased, and interfacial peeling from the electrolyte sheet of the electrode formed on the electrolyte sheet surface can be further suppressed. . Note that the lower limit value of the variation value is zero. Here, the standard deviation of the depression depth and the standard deviation of the protruding height can be obtained in the same manner as the standard deviation of the equivalent circle diameter.

  The ratio of the average depth of the depression to the average equivalent circle diameter, that is, the value of (average depth) / (average equivalent circle diameter), and the ratio of the average height of the protrusion to the average equivalent circle diameter, ie The value of (average height) / (average equivalent circle diameter) is preferably 0.05 or more, more preferably 0.10 or more, still more preferably 0.15 or more, and preferably 0.5 or less, More preferably, it is 0.45 or less, More preferably, it is 0.40 or less. When the ratio is within the above range, the average strength and the Weibull coefficient of the electrolyte sheet can be increased, and interfacial peeling of the electrode formed on the electrolyte sheet surface from the electrolyte sheet can be further suppressed.

  The interval between the depression and the protrusion may be constant or indefinite, but is preferably constant. The said space | interval means the space | interval of the adjacent lowest point of the said depression and / or the vertex of a protrusion. In consideration of the average equivalent circle diameter of the depressions or protrusions, it is preferable that the intervals do not overlap each other. Therefore, the difference between the interval and the average equivalent circle diameter of the depression or protrusion, that is, the value of (interval) − (average equivalent circle diameter) is preferably 0.1 μm or more, more preferably 0.5 μm or more, More preferably, it is 1 μm or more, preferably 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less.

  The depressions and protrusions on the surface of the electrolyte sheet according to the present invention may be arranged irregularly or may be arranged regularly. In order to make the surface roughness of the electrolyte sheet more uniform, the depressions and protrusions are preferably arranged regularly. In this case, examples of the arrangement of the depressions and protrusions include a lattice shape and a staggered shape.

  The surface roughness Ra of the depressions and protrusions is 0.01 μm or more and 3 μm or less. If the Ra value is 3 μm or less, when the stamper is pressed against the electrolyte green sheet that is the precursor of the electrolyte sheet to form a depression or protrusion, the releasability of the electrolyte green sheet with respect to the stamper increases, and the electrolyte sheet Productivity is improved. On the other hand, if the Ra value is too low, when an electrode is formed on the surface to form a single cell for SOFC, the adhesion between the electrolyte and the electrode may be lowered. Therefore, the Ra value is 0.01 μm or more. It is preferable to do. The Ra value is preferably 0.03 μm or more, more preferably 0.05 μm or more, further preferably 0.08 μm or more, particularly preferably 0.1 μm or more, and preferably 2.5 μm or less, more preferably 2 μm or less. 1.5 μm or less is more preferable, and less than 0.5 μm is particularly preferable.

  Ra means arithmetic average roughness and may be determined based on JIS B 0601-2001. Specifically, the Ra value can be obtained by calculating a roughness curve using a surface roughness measuring instrument at a portion below the baseline in the depression or a portion above the baseline in the protrusion. It is obtained by the vessel.

  The maximum height Rz of the depressions and protrusions is preferably 0.1 μm or more and 15 μm or less from the viewpoint of releasability of the stamper from the electrolyte green sheet, for the same reason as the numerical value range of Ra. The Rz value is preferably 0.3 μm or more, more preferably 0.5 μm or more, further preferably 1 μm or more, particularly preferably 2 μm or more, more preferably 12 μm or less, more preferably 10 μm or less, and further preferably 8 μm or less. Particularly preferred is less than 5 μm. The maximum height Rz refers to the distance in the height direction from the highest peak to the lowest valley in the roughness curve. The Rz value is obtained by a surface roughness measuring device in the same manner as Ra.

  In addition, when forming depressions in the electrolyte sheet, the average peak-to-peak distance obtained from the roughness curve obtained using a laser optical non-contact three-dimensional shape measuring apparatus is 0.1 μm or more and 30 μm or less, and the average valley bottom depth is 0. It is preferable that the thickness is not less than 0.05 μm and not more than 20 μm, and the tip of the recess in the depression is not an acute angle in the roughness curve.

  By forming a plurality of depressions on the surface of the electrolyte sheet to form recesses, and forming the recesses, particularly the individual recess tips (valley bottoms) in a specific shape, it is possible to prevent cracks due to stress concentration at the tips of the recesses. An electrolyte sheet having an appropriate surface roughness that contributes to an increase in area and prevention of interfacial delamination of electrodes can be obtained.

  The “distance between peaks” is a distance between two adjacent tips (peaks) recognized by a roughness curve. Further, the “valley bottom depth” is a distance from the intersection of a line connecting two adjacent convex portion tips (peaks) and a normal passing through the concave tip (valley bottom) to the concave tips. When the shape of the tip of the recess is defined, a case where the distance between the peaks is not less than 0.1 μm and not more than 30 μm and the depth of the valley is not less than 0.05 μm and not more than 20 μm is treated as depression.

  In the present invention, the recess tip shape of the depression of the electrolyte sheet is confirmed using a roughness curve defined in JIS B 0601: 2001 obtained by measuring the electrolyte sheet surface with a laser optical non-contact three-dimensional shape measuring apparatus. . The apparatus used for measuring the roughness curve of the present invention is a laser optical non-contact three-dimensional shape measuring apparatus (trade name: Microfocus Expert, model number: UBC-14 system, manufactured by UBM). The measuring method is to focus a 1 μm diameter on the electrolyte sheet surface from a semiconductor laser light source of 780 nm through a movable objective lens. At this time, specularly reflected light returns the same optical path and is evenly distributed on four photodiodes via a beam slitter. Since the image is formed, the uneven measurement electrolyte sheet surface is displaced and non-uniformity occurs in the image. A signal is immediately generated to cancel the lens, and the lens is controlled so that the objective lens is always focused on the electrolyte sheet surface. By detecting the amount of movement at the time of reading with a light barrier measurement mechanism, highly accurate measurement can be performed. The specifications are a spot diameter of 1 μm, a vertical resolution of 0.01 μm, and line profile analysis can be performed at a pitch of 0.1 mm.

  In the present invention, the nine roughness points obtained by measuring the roughness curve of the electrolyte sheet at a scan length of 4 mm using a laser optical non-contact three-dimensional shape measuring device at nine locations in the electrolyte sheet. The distance between peak summits and the depth of valley bottom were measured for all depressions observed in the depth curve, and the average values were calculated as the average distance between peak peaks and the average valley depth.

  The measurement point of the laser optical non-contact three-dimensional shape measuring apparatus includes one point of the center of gravity of the electrolyte sheet, one straight line passing through the center of gravity of the electrolyte sheet, and 45 ° with the straight line passing through the center of gravity. The electrolyte sheet is divided into 8 by a straight line having an angle of 90 ° and 135 °, and a total of 9 locations, one in each divided region. In addition, although a measurement location should just be changed suitably according to the magnitude | size and shape of an electrolyte sheet, the edge part of an electrolyte sheet should be avoided like the specific example in the case of the rectangular shape and circular shape mentioned later.

  In the electrolyte sheet of the present invention, the average peak-to-peak distance is preferably 0.1 μm or more and 30 μm or less, and the average valley bottom depth is preferably 0.05 μm or more and 20 μm or less. When the average peak-to-peak distance is less than 0.1 μm or the average valley depth is less than 0.05 μm, it is difficult to stably produce the depression. On the other hand, when the average peak-to-peak distance is more than 30 μm or the average valley depth is more than 20 μm, the electrolyte sheet strength is lowered and the Weibull coefficient is inferior.

  The average peak-to-peak distance is preferably 0.2 μm or more, more preferably 0.3 μm or more, further preferably 0.5 μm or more, preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less. . The average valley depth is preferably 0.1 μm or more, more preferably 0.2 μm or more, further preferably 0.3 μm or more, preferably 10 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. .

  Whether or not the tip of the concave portion in the depression is not an acute angle in the roughness curve is confirmed as follows. Hereinafter, a method for confirming the concave tip shape will be described. First, a scale adjustment roughness curve is prepared by adjusting the scales of the horizontal axis (length direction) and the vertical axis (peak height direction and valley depth direction) of the roughness curve to be the same. That is, in the scale adjustment roughness curve, for example, when the scale on the vertical axis is 1 scale (1 μm) = 1 mm, the scale on the horizontal axis is also 1 scale (1 μm) = 1 mm.

  In the obtained scale adjustment roughness curve, the shape of the recess (valley) is observed, and a line X (dashed line) passing through the tip of the recess (valley bottom) P and parallel to the horizontal axis is created. Next, normal lines Y1 and Y2 (two-dot chain lines) are drawn from a point at a distance of 0.1 μm from the left and right sides of the recess tip P on the parallel line X to obtain respective intersections Q and R with the roughness curve. Then, an angle θ formed by a line PQ connecting the intersection point Q and the recess tip P and a line PR connecting the intersection point R and the recess tip P is measured, and the angle θ is 90 ° or more, and the scale adjustment roughness curve Is a continuous curve from Q to R, and a shape having no inflection point is called a shape without an acute angle portion. The roughness curve is a continuous curve, that is, it can be differentiated at any point between Q and R.

The number of depressions and protrusions formed on the electrolyte sheet according to the present invention may be adjusted as appropriate, but is preferably 500 / cm ² or more and 500,000 / cm ² or less. When the ratio is 500 cells / cm ² or more, effects such as improvement in power generation performance and improvement in adhesion to electrodes when a single cell for SOFC is obtained can be obtained more reliably. On the other hand, if the number is too large, it may be difficult to peel the stamper from the electrolyte green sheet during the formation of the depressions and protrusions in spite of the adjustment of the surface roughness. 000 pieces / cm ² or less is preferable. The number is preferably 1,000 pieces / cm ² or more, more preferably 3,000 pieces / cm ² or more, more preferably 400,000 pieces / cm ² or less, and 300,000 pieces / cm ² or less. Is more preferable.

Further, on at least one side, a region having the above-described depression and / or protrusion of 500 / cm ² or more and less than 50,000 / cm ² (hereinafter sometimes referred to as “region A”), 50,000 It is also preferable to provide a region having / cm ² or more and 500,000 pieces / cm ² or less (hereinafter sometimes referred to as “region B”). In such a case, generation of warpage, undulation, and burrs can be further suppressed. Specifically, stress is applied to the electrolyte green sheet due to the formation of depressions and protrusions, and this stress also remains on the electrolyte sheet, warps to one side of the sheet, sea urchins on both sides of the sheet, and burrs at the periphery of the sheet. May occur. However, for example, by setting the peripheral edge of the sheet as the region A and the other region as the region B, the residual stress can be reduced, and the occurrence of warpage, undulation, and burrs can be suppressed.

  About the ratio of the said area | region A and the area | region B, it is preferable that the ratio of the said area | region A is 5% or more and 50% or less, and the ratio of the said area | region B is 50% or more and 95% or less in total 100%.

  As described above, it is preferable that the position of the region A (or region B) is a part of the electrolyte sheet. The “peripheral edge” of the sheet here means an area having a predetermined width including the peripheral edge of the sheet plane, and means a set of points whose distance from the peripheral edge of the sheet plane is a predetermined value or less. And The width of the peripheral portion is preferably 1.0 mm or more, more preferably 1.2 mm or more, further preferably 1.5 mm or more, more preferably 5.0 mm or less, more preferably 4.8 mm or less. 5 mm or less is more preferable. Further, the “circumferential end” of the seat plane means the outer periphery of the seat plane as shown in FIG.

  The average thickness of the electrolyte sheet is 30 μm or more and 400 μm or less. When the average thickness of the electrolyte sheet is less than 30 μm, the mechanical strength of the electrolyte sheet is weakened, handling is lowered, and cracking is likely to occur during cell formation. On the other hand, if it exceeds 400 μm, the ionic conductivity of the electrolyte sheet itself is lowered, so that the power generation performance when it is made into a cell deteriorates. In the present invention, the thickness of the electrolyte sheet is the distance between the base line on the front surface and the base line on the back surface. The average thickness of the electrolyte sheet is preferably 50 μm or more, more preferably 80 μm or more, and preferably 300 μm or less, more preferably 200 μm or less.

The area of the electrolyte sheet of the present invention is preferably 50 cm ² or more, more preferably 100 cm ² or more, preferably 1000 cm ² or less, more preferably 600 cm ² or less. The technique of the present invention is more effective in a large-sized and thin electrolyte sheet having an area of 50 cm ^{2 to} 1000 cm ² and a thickness of 30 μm to 400 μm.

  The material constituting the electrolyte sheet of the present invention is not particularly limited as long as it is a ceramic having oxygen ion conductivity, but is preferably at least one selected from the group consisting of zirconia, ceria and lanthanum gallate oxide. That is, the electrolyte sheet of the present invention preferably contains at least one element selected from the group consisting of zirconium, cerium, lanthanum and gallium.

  When using zirconia, zirconia stabilized with scandium oxide, yttrium oxide, cerium oxide, ytterbium oxide, etc .; when using ceria, ceria doped with yttria, samaria, gadolinia, etc .; lanthanum gallate oxide Lanthanum gallate perovskite structure oxide in which a part of lanthanum gallate lanthanum or gallium is substituted with strontium, calcium, barium, magnesium, aluminum, indium, cobalt, iron, nickel, copper, etc. Can be used.

  In particular, zirconia stabilized with 3 mol% to 10 mol% yttrium oxide, zirconia stabilized with 4 mol% to 12 mol% scandium oxide, and 4 mol% to 15 mol% ytterbium oxide. It is preferable to use stabilized zirconia. A material obtained by adding alumina, silica, titania or the like as a sintering aid or a dispersion strengthening agent to these stabilized zirconia can also be suitably used.

  Next, the manufacturing method of the electrolyte sheet according to the present invention will be described.

2. Production method of electrolyte sheet for solid oxide fuel cell Although not particularly limited, the electrolyte sheet according to the present invention is, for example,
A step of obtaining a slurry by mixing at least an electrolyte sheet material powder, a solvent and a binder,
A step of obtaining an electrolyte green sheet by drying after forming the slurry into a sheet,
Obtaining a surface-modified electrolyte green sheet having depressions and / or protrusions formed by pressing a stamper on one or both sides of the electrolyte green sheet; and
The surface-modified electrolyte green sheet can be manufactured by a method including a step of firing. Hereinafter, each process will be described.

(1) Slurry preparation process As electrolyte sheet material powder, the powder of electrolyte sheet material mentioned above can be used. If the desired composition of the electrolyte sheet is determined, the electrolyte sheet material powder is a conventional method such as a coprecipitation method, a uniform precipitation method, a sol-gel method, a spray pyrolysis method, a citric acid dissolution method, and a powder mixing method. Can be manufactured.

  There is no restriction | limiting in particular as a binder, The organic binder conventionally known can be selected suitably and can be used. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and / or methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetals. Examples thereof include cellulosic resins, vinyl formal resins, vinyl alcohol resins, waxes, and cellulose resins such as ethyl cellulose. These binders may be used independently and may use 2 or more types together. Among these, from the viewpoints of processability for forming depressions and protrusions on the surface of the green sheet, green sheet moldability, thermal decomposability during firing, etc., it is thermoplastic and has a number average molecular weight of 20,000. A (meth) acrylate copolymer having a glass transition temperature of −40 ° C. or higher and 20 ° C. or lower is recommended as a preferable value. Such a number average molecular weight can be measured by a conventional method. However, if there is a catalog value for a commercially available binder, it may be referred to.

  The usage ratio of the electrolyte sheet material and the binder is preferably 15 parts by mass or more, more preferably 16 parts by mass or more, and preferably 30 parts by mass or less, more preferably 24 parts by mass with respect to 100 parts by mass of the electrolyte sheet material. It is as follows. When the amount of the binder used is insufficient, the green sheet moldability is lowered, and the strength and flexibility are insufficient. Conversely, if the amount of binder used is too large, not only will it be difficult to adjust the viscosity of the slurry, but there will be a large amount of decomposition and release of the binder component during firing, resulting in large variations in shrinkage rate. Tends to remain as residual carbon.

  Solvents include alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol; ketones such as acetone and 2-butanone; aliphatic hydrocarbons such as pentane, hexane and heptane; benzene and toluene And aromatic hydrocarbons such as xylene; and acetates such as methyl acetate, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. The amount of the solvent used should be appropriately adjusted in consideration of the viscosity of the slurry at the time of forming the electrolyte green sheet, preferably the slurry viscosity is 1 Pa · s to 50 Pa · s, more preferably 2 Pa · s to 20 Pa · s. It is good to adjust so that it may become the range below s.

  Components other than the electrolyte sheet material powder, the solvent and the binder may be appropriately blended in the slurry. Examples of other components include a dispersant, a plasticizer, a surfactant, and an antifoaming agent.

  Examples of the dispersant include polyelectrolytes such as polyacrylic acid and ammonium polyacrylate; organic acids such as citric acid and tartaric acid; copolymers of isobutylene or styrene and maleic anhydride and ammonium salts or amine salts thereof; butadiene A copolymer with maleic anhydride and its ammonium salt can be used. By using the dispersant, it is possible to promote peptization and dispersion of the electrolyte sheet material.

  Plasticizers include phthalates such as dibutyl phthalate, dioctyl phthalate and ditridecyl phthalate; glycols such as propylene glycol and glycol ethers; phthalic polyesters, adipic acid polyesters, sebacic acid polyesters, etc. Polyesters can be used. By using a plasticizer, the processability of the electrolyte green sheet is improved, and depressions and protrusions are easily formed.

  What is necessary is just to mix said each component by a conventional method. For example, when a raw material powder having a desired secondary particle size is obtained in advance, it may be mixed using a disper or the like under a condition that is not further pulverized. When the secondary particle diameter of the raw material powder is not adjusted in advance, it may be pulverized and mixed until a desired secondary particle diameter is obtained using a ball mill or the like.

(2) Electrolyte green sheet manufacturing process Next, the slurry is formed into a sheet and then dried to obtain an electrolyte green sheet.

  The method for forming the slurry into a sheet is not particularly limited, and a conventional method such as a doctor blade method or an extrusion method may be used. For example, first, a slurry formed into a sheet is dried to obtain a long electrolyte green tape.

  The drying conditions may be appropriately adjusted according to the type of solvent used, but are usually 40 ° C. or higher, more preferably 80 ° C. or higher and about 150 ° C. or lower. Drying may be performed at a constant temperature, or may be performed by heating by successively raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C.

  The thickness of the electrolyte green tape may be adjusted as appropriate, but is preferably 40 μm or more and 500 μm or less in consideration of the desired thickness of the electrolyte sheet.

  Next, the electrolyte green tape may be punched or cut into an appropriate size by an arbitrary method to form an electrolyte green sheet. The preferred size of the electrolyte green sheet is 50 mm square or more and 400 mm square or less in the case of a square, and 50 mmφ or more and 400 mmφ or less in the case of a circle.

As the properties of the electrolyte green sheet, the tensile elongation at break in a tensile test at a temperature when pressing the stamper is preferably 20% or more, more preferably 25% or more, and further preferably 30% or more. It is preferably 500% or less, more preferably 400% or less, and still more preferably 300% or less. Further, the tensile yield strength in the tensile test at the temperature when pressing the stamper is preferably 1.96 MPa (20 kgf / cm ² ) or more, more preferably 2.45 MPa (25 kgf / cm ² ) or more. preferably 19.6MPa (200kgf / cm ²⁾ or less, more preferably 17.6MPa (180kgf / cm ²⁾ or less, more preferably from 14.7MPa (150kgf / cm ^2). Here, the tensile fracture elongation is the elongation corresponding to the tensile stress at the moment when the test piece breaks. Tensile yield strength is the tensile stress at the first point on the load-elongation curve when the specimen is pulled with a tensile load, where an increase in elongation is observed without increasing the load, that is, the tensile load applied to the specimen. Is a value obtained by dividing by the original cross-sectional area between test specimen markings.

  Moreover, as a characteristic of the electrolyte green sheet, the maximum stress at the time of a tensile test at a temperature of 23 ° C. is preferably 3.0 MPa or more, more preferably 4.0 MPa or more, still more preferably 5.0 MPa or more. 0 MPa or less is preferable, more preferably 18.0 MPa or less, and still more preferably 15.0 MPa or less. Further, the elongation at the time of maximum stress load at a temperature of 23 ° C. is preferably 5.0% or more, more preferably 7.0% or more, further preferably 10.0% or more, and less than 30.0%. Preferably, it is 25.0% or less, more preferably 20.0% or less.

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

  In order to produce a green sheet having the above physical properties, a (meth) acrylate copolymer having a number average molecular weight of 50,000 to 200,000 and a glass transition temperature of −30 ° C. to 10 ° C. as the binder. It is particularly preferable to use Moreover, it is preferable that content of the said copolymer as a binder shall be 12 to 30 mass parts with respect to 100 mass parts of said electrolyte sheet material in conversion of solid content.

(3) Manufacturing process of surface-modified electrolyte green sheet Next, a surface-modified electrolyte green sheet in which depressions and / or protrusions are formed is obtained by pressing a stamper on one or both surfaces of the electrolyte green sheet.

  The stamper used in this step has protrusions and / or depressions on the surface of the electrolyte green sheet to form the desired depressions and / or protrusions, and the surface of the stamper is predetermined by pressing the electrolyte sheet. Depressions and / or protrusions can be formed.

  The stamper according to the present invention has two or more depressions and / or protrusions, and the basal plane shape of the depressions and protrusions is a curve having a radius of curvature of 0.1 μm or more. It is a rounded polygon and / or a three-dimensional shape of a hemisphere, a semi-elliptical sphere, or a polyhedron whose cross-sectional shape of a vertex and a ridge is a curve having a curvature radius of 0.1 μm or more, The average equivalent circle diameter of the basal plane of the protrusion is 0.8 μm or more and 380 μm or less, the average depth of the depression and the average height of the protrusion are 1.1 μm or more and 186 μm or less, and the depression and protrusion The surface roughness Ra is 0.01 μm or more and 10 μm or less.

  The number of depressions and protrusions in the stamper, the definition of the wording that defines the stamper, the preferred mode, and the like can be the same as described above for the electrolyte sheet.

  The equivalent circle diameter of the base surface of the protrusions and depressions in the stamper is 0.8 μm or more and 380 μm or less, preferably 8 μm or more, more preferably 25 μm or more, and preferably 320 μm or less, more preferably 240 μm or less. is there. If the equivalent circle diameter is within the above range, a depression or a protrusion having a basal plane shape having a desired average equivalent circle diameter can be easily formed in the electrolyte sheet. The protrusions and depressions may have a plurality of types having different equivalent circle diameters, but it is preferable that all the protrusions and depressions have the same equivalent circle diameter.

  The height of the protrusion and the depth of the depression in the stamper is preferably 1.1 μm or more, more preferably 4 μm or more, further preferably 11 μm or more, preferably 186 μm or less, more preferably 150 μm or less, still more preferably Is 110 μm or less. If the height of the protrusion and the depth of the depression are within the above ranges, the depression or protrusion having a desired depth or height can be easily formed in the electrolyte sheet. The protrusions or depressions may have a plurality of types having different heights or depths, but it is preferable that all the protrusions or depressions have the same height or depth.

  The surface roughness Ra of the depression and protrusion of the stamper is 0.01 μm or more and 10 μm or less. If the Ra value is within the range, depressions and protrusions having an appropriate surface roughness can be formed on the electrolyte green sheet, and consequently the surface roughness of the depressions and protrusions of the electrolyte sheet is within a predetermined range. Can be adjusted within. The Ra value is preferably 0.1 μm or more, more preferably 0.3 μm or more, more preferably 8 μm or less, and even more preferably 6 μm or less.

  Further, the maximum height Rz of the depressions and protrusions is preferably 0.2 μm or more and 25 μm or less for the same reason as the numerical value range of Ra. The Rz value is preferably 0.5 μm or more.

  Note that the surface roughness of the stamper depressions and protrusions can be adjusted by surface processing such as polishing, coating with Teflon (registered trademark), etching, blasting, or the like.

  The distance between the protruding vertices of the stamper, that is, the distance between two adjacent protruding vertices, or the distance between the lowest points of the depressions, that is, the distance between the two adjacent lowest points of the depressions is constant or indefinite. However, it is preferable that the interval is constant. It is preferable that the above intervals take into consideration the average equivalent circle diameter of the depressions or protrusions so that the depressions or protrusions do not overlap. Therefore, the difference between the interval and the average equivalent circle diameter of the depression or protrusion (interval-average equivalent circle diameter) is preferably 0.2 μm or more, more preferably 1.0 μm or more, and preferably 50 μm or less, more Preferably it is 30 micrometers or less. Furthermore, it is preferable that a taper is provided in the vicinity of the basal plane of the protrusion or depression in the radially outward direction because of excellent mold releasability.

  As a method for forming the protrusion or depression in the stamper, any method can be used as long as the protrusion or depression can be formed in the metal material or the resin material, but an optical information recording medium is preferable. A stamper manufacturing method for transferring a fine pattern used for manufacturing an optical disk or a magneto-optical disk can be applied as it is. That is, it can be easily produced by photolithography and electroforming technology used for producing an optical disk or the like. The stamper is preferably made of metal or resin. Moreover, you may be comprised from the combination of metal material and resin material, or the same material. Further, as shown in FIG. 2, the stamper 3 may be configured by a substrate portion 3 </ b> A and a pressing portion 3 </ b> B formed with protrusions and / or depressions. In this case, the substrate part and the pressing part may be made of different materials or may be made of the same material.

  Examples of the metal material include metal materials such as cemented carbide tungsten, stainless steel, stellite, nickel-based metal, nickel-based alloy, special steel, and cemented carbide. In addition, as resin materials, engineering plastics such as polyacetal, polyamide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyimide, polyetherimide, Fluorine resins such as polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, polyvinylidene fluoride, polychlorotrifluoroethylene, and tetrafluoroethylene perfluoroalkyl biether copolymer can be exemplified. Among these, nickel-based metals are suitable when a stamper is manufactured by photolithography and electroforming technology.

  The method for pressing the stamper against the electrolyte green sheet is not particularly limited, and a stamper attached to a known press machine may be pressed against the electrolyte green sheet. Specifically, the electrolyte green sheet is sandwiched between two stampers, or the electrolyte green sheet is placed on the stamper, and these are placed on the lower stage of the press machine and added from the upper stage. The depressions and / or protrusions are formed by pressing. Here, the stage is preferably a heating stage capable of heating the electrolyte green sheet to 30 ° C. or more and 100 ° C. or less. At this time, the depth of the depression formed in the electrolyte green sheet, the equivalent circle diameter, the height of the protrusion, and the equivalent circle diameter can be adjusted by the pressing force, pressing time, pressing temperature, green sheet temperature, and the like. That is, as the pressing force is higher, the pressing time is longer, and the pressing temperature is higher, the depression and / or protrusion of the green sheet can be easily formed.

The pressing force for pressing the stamper is preferably 1.96 MPa (20 kgf / cm ² ) or more, more preferably 2.94 MPa (30 kgf / cm ² ) or more, further preferably 9.81 MPa (100 kgf / cm ² ) or more, 49.0MPa (500kgf / cm ²⁾ or less, and more preferably 39.2MPa (400kgf / cm ^2), more preferably not more than 29.4MPa (300kgf / cm ^2). The pressing time when pressing the stamper is preferably 0.5 seconds or more, more preferably 1 second or more, still more preferably 2 seconds or more, preferably 300 seconds or less, more preferably 180 seconds or less, still more preferably 120 seconds. When the pressing force is 1.96 MPa or more and the pressing time is 0.5 seconds or more, the depression or the like can be sufficiently formed in the electrolyte green sheet. Further, if the pressing force is 49.0 MPa or less and the total pressing time is 300 seconds or less, there is little waste of energy and time, and the electrolyte green sheet in which depressions and / or protrusions are formed after the pressing process cannot be peeled from the stamper. It is difficult to cause the problem. Furthermore, if the pressing process is performed in such a range, there is also an advantage that it is easy to adjust the roughness of the green sheet obtained according to the pressing force or pressing time, respectively. In addition, when pressing the stamper which has a protrusion, it is preferable that only the protrusion of the pressing portion 3B is pressed against the electrolyte green sheet 4 as shown in FIG.

  In addition, the higher the electrolyte green sheet temperature when pressing the stamper is, the more flexible the green sheet is, and the depressions and / or protrusions are more easily transferred to the shape. However, the adjustment of the roughness by temperature control not only requires a temperature control means, but if the temperature is raised too much, the stamper is adhered to the green sheet and it becomes difficult to peel off the stamper from the green sheet after pressing. May be difficult. Therefore, the temperature of the electrolyte sheet during pressing is preferably 20 ° C or higher, more preferably 30 ° C or higher, preferably 80 ° C or lower, more preferably 60 ° C or lower.

  By sandwiching an electrolyte green sheet sandwiched between stampers with an acrylic plate, a wooden plate, a metal plate, etc., and stacking them, a plurality of electrolyte green sheets can be pressed simultaneously. In addition, there is no restriction | limiting in particular in the kind of press machine to be used, Press machines, such as 1 axis | shaft, 2 axes | shafts, 4 axes | shafts, are used, However, A 4 axis press machine is easy to apply a uniform pressing force to a green sheet, and is preferable.

  After the pressing treatment, peeling of the electrolyte green sheet from the stamper is preferably performed within 3 hours, more preferably within 1 hour, and even more preferably within 10 minutes. If left unnecessarily longer, peeling may not be possible.

(4) Firing step Next, the electrolyte sheet according to the present invention can be obtained by firing the surface-modified electrolyte green sheet formed with depressions and / or protrusions obtained as described above.

  Specific firing conditions are not particularly limited, and may be based on a conventional method. For example, in order to remove organic components such as a binder and a plasticizer from the electrolyte green sheet, the treatment is performed at 150 ° C. to 600 ° C., preferably 250 ° C. to 500 ° C. for about 5 hours to 80 hours. Next, by holding and baking at 1000 ° C. or more and 1600 ° C. or less, preferably 1200 ° C. or more and 1500 ° C. or less for 2 hours or more and 10 hours or less, an electrolyte sheet in which depressions and / or protrusions are formed is obtained.

3. Next, a single cell for a solid oxide fuel cell will be described. A cell for a solid oxide fuel cell according to the present invention includes the electrolyte sheet according to the present invention as a solid electrolyte.

  The electrolyte sheet of the present invention has depressions and / or protrusions having a predetermined size and shape on the surface thereof. Therefore, when the electrolyte sheet of the present invention is used as an electrolyte membrane of a solid oxide fuel cell single cell, since the contact area with the electrode is large, efficient power generation is possible, and adhesion with the electrode is high. Therefore, long-term stable power generation becomes possible. Furthermore, since there are few locations where cracks are generated, the sheet strength and its Weibull coefficient are also increased, and the reliability of the electrolyte sheet is improved.

  The solid oxide fuel cell unit cell of the present invention can be obtained by forming a fuel electrode on one surface of an electrolyte sheet and forming an air electrode on the other surface by screen printing or the like. Here, the order of formation of the fuel electrode and the air electrode is not particularly limited, but after forming an electrode having a low firing temperature on the electrolyte sheet and firing it, the other electrode is formed and fired. Alternatively, the fuel electrode and the air electrode may be fired simultaneously. In addition, a ceria intermediate layer as a barrier layer may be formed between the electrolyte sheet and the air electrode in order to prevent generation of a high resistance component due to a solid phase reaction between the electrolyte sheet and the air electrode. In this case, the fuel electrode is formed on the surface on which the intermediate layer is formed or the surface opposite to the surface to be formed, and the air electrode is formed on the intermediate layer. Here, the order in which the intermediate layer and the fuel electrode are formed is not particularly limited, and the intermediate layer and the fuel electrode are formed by applying and drying the intermediate layer paste and the fuel electrode paste on each surface of the electrolyte sheet and then sintering. May be formed simultaneously.

  The material for the fuel electrode and the air electrode, further the intermediate layer material, and the paste application method, drying conditions, and firing conditions for forming them can be implemented in accordance with conventionally known methods.

  Here, in the solid oxide fuel cell, oxygen that permeates the electrolyte causes an electrode reaction at the three-phase interface (electrolyte sheet / electrode / gas phase). Therefore, the power density of the fuel cell can be improved by increasing the surface area of the electrolyte sheet and increasing the number of contacts with the electrode material. Therefore, when a depression is formed in the electrolyte sheet for a solid oxide fuel cell and the fuel electrode and / or the air electrode are directly formed on the electrolyte sheet for the solid oxide fuel cell, the fuel electrode or air It is preferable that at least one of the electrode particles constituting the pole has an average particle diameter of 1/10 or less of the average equivalent circle diameter of the depression. By carrying out like this, a some electrode particle can enter in the depression formed in the electrolyte sheet, and the contact of an electrolyte sheet and an electrode particle can be increased more. The average particle diameter of the electrode particles is more preferably 1/20 or less, and still more preferably 1/30 or less of the average equivalent circle diameter of the depression.

  The solid oxide fuel cell unit cell according to the present invention in which the fuel electrode, the air electrode, and the intermediate layer are formed on the electrolyte sheet has a large contact area between the electrolyte and the electrode or the intermediate layer. Very good. Therefore, the present invention can contribute to the practical use of a fuel cell as an electrolyte sheet that can be used as an electrolyte membrane of a solid oxide fuel cell having excellent performance.

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

Example 1
(1) Production of stamper A stamper was produced by photolithography and electroforming technology used for production of music CDs and the like. Specifically, a photo-curable photoresist was applied on a clean glass substrate, covered with a photomask having about 62,000 circles per cm ² prepared in advance, and exposed. After development, the uncured resist was poured out, and then etched to remove the corners of the resist. Subsequently, a Ni plating layer having a thickness of 0.3 mm was formed by electroforming, the Ni plate was peeled off from the glass substrate, and the photoresist was removed to remove the photoresist. 1 was obtained.

The obtained stamper No. In No. 1, the pressing portion and the substrate portion were made of Ni alloy, the protruding shape was hemispherical, the protruding height was 15 μm, the protruding diameter was 30 μm, and the interval between adjacent protruding vertices was 40 μm. The surface roughness Ra of the protrusions was 1.5 μm, and Rz was 4.8 μm. The number of protrusions per 1 cm ² was about 62,000.

(2) Production of electrolyte sheet 6 mol% scandium stabilized zirconia powder (Daiichi Rare Element Co., Ltd., trade name “6ScSZ”, specific surface area: 11 m ² / g, average particle size: 0.5 μm) (hereinafter, 6 mol) % Scandium-stabilized zirconia is referred to as “6ScSZ” and 100 parts by mass. A methacrylate copolymer (number average molecular weight: 100,000, glass transition temperature: −8 ° C., solid content concentration: 50% by mass). 17 parts by weight of a binder consisting of 3 parts by weight and 3 parts by weight of dibutyl phthalate as a plasticizer are put into a nylon pot together with a mixed solvent of toluene / isopropanol (mass ratio: 3/2) and milled at 60 rpm for 20 hours. A raw material slurry was prepared. This slurry was transferred to a vacuum degassing vessel, and the pressure was reduced to 3.99 kPa to 21.3 kPa (30 Torr to 160 Torr), followed by concentration and defoaming to obtain a coating slurry having a viscosity of 2.5 Pa · s.

The obtained slurry for coating is transferred to a slurry dam of a coating apparatus, and continuously applied onto a PET film by a doctor blade of the coating part, and 0.15 m in a drying furnace at 110 ° C. following the coating part. A long 6ScSZ green tape having a thickness of about 180 μm was formed by allowing the solvent to evaporate by drying at a rate of / min and drying. The obtained green tape was 13.9 MPa (142 kgf / cm ² ) by a tensile test at 23 ° C., and the elongation at the maximum stress load was 34%.

The 6ScSZ green tape is cut into an approximately 12 cm square green sheet, which is placed on a heating table. 1 was stacked to form a laminate. This laminate was placed on the press part of a compression molding machine (manufactured by Shinfuji Metal Industry Co., Ltd., model “S-37.5”), pressing temperature 25 ° C., pressing force 22.5 MPa (230 kgf / cm ² ), pressing time. Pressurization was performed for 2 seconds. The stamper was peeled from the green sheet to obtain a 6ScSZ green sheet in which a recessed hole was formed.

  The green sheet was fired at 1400 ° C. for 3 hours to obtain a 6ScSZ electrolyte sheet having a depression of 10 cm square and a thickness of 160 μm.

  The obtained 6ScSZ electrolyte sheet was measured for average equivalent-circle diameter, average depth of depression, and surface roughness Ra. These results are shown in Table 1. The tips of the recesses in the depression found in the roughness curve of the obtained 6ScSZ electrolyte sheet were not acute angles.

Example 2
In Example 1 (1) above, the stamper No. was similarly changed except that the size of the circle of the photomask was increased and the number of circles was about 8000 per 1 cm ² . 2 was produced. The stamper No. The surface roughness Ra of the protrusion 2 was 3.1 μm and Rz was 14.2 μm. Stamper No. No. 1 A 6ScSZ electrolyte sheet having a 10 cm square and a thickness of 160 μm was obtained in the same manner as in Example 1 (2) except that 2 was used. All the tips of the recesses in the depressions found in the roughness curve of the obtained 6ScSZ electrolyte sheet were not acute angles.

Comparative Example 1
The above stamper No. 1 is roughened by blasting to adjust the surface roughness of Ra to 11.6 μm and Rz to 25.8 μm. 3 was obtained. Stamper No. No. 1 A 6ScSZ electrolyte sheet having a 10 cm square and a thickness of 160 μm was obtained in the same manner as in Example 1 (2) except that 3 was used. The tip of some of the recesses in the depression found in the roughness curve of the obtained 6ScSZ electrolyte sheet had an acute angle.

  The results are summarized in Table 1.

  As shown in Table 1, when the Ra of the protruding portion of the stamper is excessively large (Comparative Example 1), the Ra of the electrolyte sheet becomes as large as 4.9 μm, possibly due to the problem of releasability. The shape of the top of the depression did not become a rounded polygon. On the other hand, in the electrolyte sheet (Examples 1 and 2) in which Ra of the projecting portion of the stamper is moderate and Ra of the depressed portion is in the range of 0.01 μm to 3 μm, the radius of curvature of the apex shape of the depressed portion Was 0.1 μm or more. As described above, it has been found that the surface roughness Ra of the depression of the electrolyte sheet greatly affects the production efficiency of the electrolyte sheet.

  1: electrolyte sheet, 1A: electrolyte sheet peripheral edge, 2: depression, 3: stamper, 3A: base part, 3B: pressing part, 4: electrolyte green sheet

Claims (8)

Having at least two depressions and / or protrusions on at least one side;
The basal plane shape of the depressions and protrusions is a circle, an ellipse, or a rounded polygon in which the shape of the apex is a curve having a curvature radius of 0.1 μm or more, and / or the three-dimensional shape thereof is a hemisphere , A semi-elliptical sphere, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a curvature radius of 0.1 μm or more,
The average equivalent circle diameter of the basal plane of the depression and protrusion is 0.5 μm or more and 250 μm or less,
The average depth of the depression and the average height of the protrusions are 0.3 μm or more and 50 μm or less,
The surface roughness Ra of the depressions and protrusions is 0.01 μm or more and 3 μm or less, and
An electrolyte sheet for a solid oxide fuel cell, having an average thickness of 30 μm to 400 μm. 2. The electrolyte sheet for a solid oxide fuel cell according to claim 1, wherein the depressions and / or protrusions are 500 / cm ² or more and 500,000 / cm ² or less. At least one surface has a region having the above depression and / or protrusion of 500 / cm ² or more and less than 50,000 / cm ^{2 and} a region having 50,000 / cm ² or more and 500,000 / cm ² or less. The electrolyte sheet for a solid oxide fuel cell according to claim 1.   A single cell for a solid oxide fuel cell, comprising the electrolyte sheet for a solid oxide fuel cell according to claim 1. A stamper for forming depressions and / or protrusions in the electrolyte green sheet,
Have two or more depressions and / or protrusions,
The basal plane shape of the depressions and protrusions is a circle, an ellipse, or a rounded polygon in which the shape of the apex is a curve having a curvature radius of 0.1 μm or more, and / or the three-dimensional shape thereof is a hemisphere , A semi-elliptical sphere, or a polyhedron whose cross-sectional shape of the apex and ridge is a curve having a curvature radius of 0.1 μm or more,
The average equivalent circle diameter of the basal plane of the depressions and protrusions is 0.8 μm or more and 380 μm or less,
The average depth of the depression and the average height of the protrusions are 1.1 μm or more and 186 μm or less, and
A stamper having a surface roughness Ra of the depressions and protrusions of 0.01 μm or more and 10 μm or less. 6. The stamper according to claim 5, wherein the depressions and / or protrusions are 500 pieces / cm ² or more and 500,000 pieces / cm ² or less. 6. A region having the depression and / or protrusion of 500 / cm ² or more and less than 50,000 / cm ^{2 and} a region having 50,000 / cm ² or more and 500,000 / cm ² or less. The stamper described in 1. A method for producing an electrolyte sheet for a solid oxide fuel cell, comprising:
A step of obtaining a surface-modified electrolyte green sheet in which depressions and / or protrusions are formed by pressing the stamper according to any one of claims 5 to 7 on one side or both sides of the electrolyte green sheet; and
A method comprising firing the surface-modified electrolyte green sheet.