Ceramic sheet

Abstract

A ceramic sheet according to the present invention has a first main surface and a second main surface, and the arithmetic mean roughness of each of the first main surface and the second main surface is 0.01 to 1.0 μm. When each of the first main surface and the second main surface is measured with a laser microscope, the average value of the difference between the highest point and the lowest point at any 10 sections is 1.0 to 4.0 μm on at least one of the first main surface and the second main surface, the coefficient of variation of the difference is 0.05 to 0.3, the cumulative relative frequency where the slope of the approximate straight line calculated per 1.314 μm is -0.1 to 0.1 is 20% to 70%, the cumulative relative frequency where the slope of the approximate straight line is -0.3 to 0.3 is 85% to 100%, and the cumulative relative frequency where the slope of the approximate straight line is -1.5 to 1.5 is 99.9% or more.

Description

ceramic sheet

[0001] The present disclosure relates to ceramic sheets.

[0002] Ceramics are widely used in many fields because they have excellent mechanical properties such as heat resistance and wear resistance, as well as electrical and magnetic properties, and even biocompatibility. Among these, ceramics based on zirconia have excellent oxygen ion conductivity. Therefore, a sheet-shaped molded product (ceramic sheet) of this ceramic is sometimes used as a solid electrolyte for solid oxide fuel cells (SOFCs). For example, Patent Document 1 below discloses a method for manufacturing an electrolyte sheet for solid oxide fuel cells.

[0003] JP 2012-79506 A

[0004] In order to improve the efficiency of conveyance, multiple ceramic sheets may be placed in a state where they are directly stacked on top of each other. When only the topmost ceramic sheet in such a stack of multiple ceramic sheets is adsorbed and conveyed, the ceramic sheet in close contact with the topmost ceramic sheet may also be conveyed at the same time. In other words, when adsorbing and conveying ceramic sheets, double picking of sheets may occur unintentionally.

[0005] In order to prevent the above-mentioned double-sheet cutting, it is conceivable to roughen the surface of the ceramic sheet, but simply roughening the surface of the ceramic sheet results in a problem of a decrease in the strength of the ceramic sheet.

[0006] An object according to one aspect of the present disclosure is to provide a ceramic sheet that can prevent double-sheeting while maintaining the strength of the ceramic sheet.

[0007] One aspect of the present disclosure provides a ceramic sheet according to the following [1] to [9]: [1] A ceramic sheet having a first main surface and a second main surface, wherein the arithmetic mean roughness of each of the first main surface and the second main surface is 0.01 μm or more and 1.0 μm or less, and when the first main surface and the second main surface are each measured with a laser microscope, on at least one of the first main surface and the second main surface, the average value of the difference between the highest point and the lowest point in any 10 sections (150 μm per section) is 1.0 μm or more and 4.0 μm or less, the coefficient of variation of the difference between the highest point and the lowest point in the any 10 sections is 0.05 or more and 0.3 or less, the cumulative relative frequency of the slope of an approximate straight line calculated every 1.314 μm being -0.1 or more and 0.1 or less is 20% or more and 70% or less, and the cumulative relative frequency of the slope of the approximate straight line being -0.3 or more and 0.3 or less is 85% or more and 100% or less, [2] The ceramic sheet according to [1], wherein the cumulative relative frequency when the slope of the approximate straight line is -1.5 or more and 1.5 or less is 99.9% or more and 100% or less. [3] The ceramic sheet according to [1] or [2], wherein the cumulative relative frequency when the slope of the approximate straight line is -1.0 or more and 1.0 or less is 99.0% or more and 100% or less. [4] The ceramic sheet according to any of [1] to [3], wherein, on both the first main surface and the second main surface, the cumulative relative frequency when the slope of the approximate straight line is -0.3 or more and 0.3 or less is 85% or more and 100% or less, and the cumulative relative frequency when the slope of the approximate straight line is -1.5 or more and 1.5 or less is 99.9% or more and 100% or less. [5] The ceramic sheet according to any one of [1] to [4], further comprising a side surface connecting the first main surface and the second main surface, and the grain size of at least one of the first main surface and the second main surface is 90% to 130% of the grain size of the side surface. [6] The ceramic sheet according to any one of [1] to [4], further comprising a thickness of 30 μm to 200 μm, and an area of ​​each of the first main surface and the second main surface is 100 cm ２ More than 400cm ２ Below, the weight is 0.015 g / cm ２ 0.15g / cm or more ２[7] The ceramic sheet according to any one of [1] to [5], wherein the average value of kurtosis (Rku) of at least one of the first main surface and the second main surface is less than 3. [8] The ceramic sheet according to any one of [1] to [7], which is a zirconia sheet containing at least one rare earth element selected from the group consisting of scandium, yttrium, and cerium in a proportion of 3 mol % to 15 mol % in total, calculated as oxides. [9] The ceramic sheet according to any one of [1] to [8], which is an electrolyte sheet for a solid oxide fuel cell.

[0008] Another aspect of the present disclosure provides a method for manufacturing a ceramic sheet according to the following

[10] to

[15] .

[10] The method for manufacturing a ceramic sheet according to any one of [1] to [9], comprising: a first step of preparing a slurry by mixing a ceramic powder, a binder, and a solvent; a second step of applying the slurry to a surface of a substrate film to be coated to form a green sheet; a third step of degreasing the green sheet to form a degreased body of the green sheet; and a fourth step of firing the degreased body to form the ceramic sheet, wherein in the third step, the green sheet is heat-treated at a heat treatment temperature of 100°C or higher and 450°C or lower, and in the fourth step, the degreased body is fired at a firing temperature of 1200°C or higher and 1600°C or lower.

[11] The method for producing a ceramic sheet according to

[10] , wherein the surface to be coated has been surface-treated with an alkaline chemical solution, the heat treatment temperature is 370°C or higher and 450°C or lower, and the firing temperature is 1350°C or higher and 1450°C or lower.

[12] The method for producing a ceramic sheet according to

[10] or

[11] , wherein the arithmetic mean roughness of the surface to be coated is 0.2 μm or higher and 0.7 μm or lower.

[13] The method for producing a ceramic sheet according to

[10] or

[11] , wherein the arithmetic mean roughness of the surface to be coated is 0.3 μm or higher and 0.6 μm or lower.

[14] The method for producing a ceramic sheet according to any of

[10] to

[13] , wherein the ceramic powder is a zirconia-based powder.

[15] The method for producing a ceramic sheet according to any of

[10] to

[14] , wherein the second step is a step of forming a green sheet by applying the slurry to the surface to be coated of a substrate film in the form of a sheet by a doctor blade method.

[0009] According to one aspect of the present disclosure, it is possible to provide a ceramic sheet that can prevent double-sheeting while maintaining the strength of the ceramic sheet.

[0010] FIG. 1 is a schematic cross-sectional view of a ceramic sheet according to one embodiment. FIG. 2 is a graph showing the results of shape analysis of the surface profile of an arbitrary section of the first main surface using a laser microscope. FIG. 3 is a graph showing an enlargement of a portion of FIG. 2. FIG. 4(a) is a sheet surface image of the PET surface of Example 1, and FIG. 4(b) is a measurement result of the surface shape profile of the PET surface of Example 1. FIG. 5(a) is a sheet surface image of the PET surface of Example 2, and FIG. 5(b) is a measurement result of the surface shape profile of the PET surface of Example 2. FIG. 6(a) is a sheet surface image of the PET surface of Comparative Example 1, and FIG. 6(b) is a measurement result of the surface shape profile of the PET surface of Comparative Example 1. FIG. 7(a) is a sheet surface image of the air surface of Comparative Example 1, and FIG. 7(b) is a measurement result of the surface shape profile of the air surface of Comparative Example 1. (a) of Fig. 8 is a sheet surface image of the PET surface of Comparative Example 2, and (b) of Fig. 8 is the measurement result of the surface shape profile of the PET surface of Comparative Example 2. (a) of Fig. 9 is a sheet surface image of the PET surface of Comparative Example 4, and (b) of Fig. 9 is the measurement result of the surface shape profile of the PET surface of Comparative Example 4. (a) of Fig. 10 is a sheet surface image of the PET surface of Comparative Example 5, and (b) of Fig. 10 is the measurement result of the surface shape profile of the PET surface of Comparative Example 5. (a) of Fig. 11 is a sheet surface image of the PET surface of Comparative Example 6, and (b) of Fig. 11 is the measurement result of the surface shape profile of the PET surface of Comparative Example 6.

[0011] An embodiment of the present disclosure will be described in detail below, but the present disclosure is not limited thereto.

[0012] A ceramic sheet according to an embodiment will be described in detail below with reference to FIG. 1 . FIG. 1 is a schematic cross-sectional view of the ceramic sheet according to an embodiment. The ceramic sheet according to an embodiment is a solid electrolyte (solid oxide fuel cell electrolyte sheet) for a solid oxide fuel cell (hereinafter referred to as "SOFC"), but the ceramic sheet of the present disclosure is not limited to solid electrolytes for SOFCs. In one example, the ceramic sheet is a zirconia sheet primarily made of stabilized zirconia powder. From the viewpoint of electrical conductivity (ionic conductivity) as an electrolyte sheet, the content of zirconia-based oxide in the zirconia sheet is, for example, 80% by mass or more relative to 100% by mass of the zirconia sheet. The content may be 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more. The stabilized zirconia powder may be a cubic zirconia powder or a tetragonal zirconia powder. In this case, the cubic crystal ratio (%) measured by X-ray diffraction measurement of the ceramic sheet may be 50% or more, and the tetragonal crystal ratio (%) may be 50% or more. In this disclosure, the term "stabilized" includes "partially stabilized." Therefore, stabilized zirconia can also be interpreted as "partially stabilized zirconia."

[0013] As a raw material for the ceramic sheet of the present disclosure, for example, a known stabilized zirconia powder can be used. ２ Ceria-based oxides such as Bi ２ O ３ Bismuth oxides such as CaO, SrO, BaO, Y ２ O ３ , La ２ O ３ , Ce ２ O ３ , Pr ２ O ３ , Nd ２ O ３ , Sm ２ O ３ , Eu ２ O ３ , Gd ２ O ３ , Tb ２ O ３ , Dy ２ O３ , Ho ２ O ３ , Er ２ O ３ , Yb ２ O ３ , PbO, WO ３ , MoO ３ , V ２ O ５ , Ta ２ O ５ and Nb ２ O ５ At least one selected from the following may be added to the powder: LaGaO ３ Gallate-based oxides such as may also be included.

[0014] In one embodiment, the ceramic powder comprises a powdered zirconia-based ceramic (zirconia-based powder). The zirconia-based ceramic is, for example, zirconia containing a stabilizer. The stabilizer may be an alkaline earth metal oxide such as MgO, CaO, SrO, or BaO; Sc ２ O ３ , Y ２ O ３ , La ２ O ３ , CeO ２ , Pr ２ O ３ , Nd ２ O ３ , 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 rare earth element oxides such as Bi; ２ O ３ and In ２ O ３ The zirconia-based ceramic contains at least one oxide selected from the group consisting of Al, AlN, AlNb, AlNbO ... ２ O３ , SiO ２ , Ge ２ O ３ , B ２ O ３ , SnO ２ , Ta ２ O ５ and Nb ２ O ５ Oxides such as may be included.

[0015] From the viewpoints of oxygen ion conductivity, strength, toughness, etc., the zirconia-based ceramic may be a zirconia powder containing at least one rare earth element selected from the group consisting of scandium, yttrium, cerium, gadolinium, and ytterbium in a total amount of 0.5 mol % to 20 mol %, or 3 mol % to 15 mol %, calculated on oxides. In this case, the ceramic sheet of the present disclosure may be a zirconia sheet containing at least one rare earth element selected from the group consisting of scandium, yttrium, cerium, gadolinium, and ytterbium in a total amount of 0.5 mol % to 20 mol %, or 3 mol % to 15 mol %, calculated on oxides. The zirconia-based ceramic may be a zirconia powder containing at least one rare earth element selected from the group consisting of scandium, yttrium, and cerium in a total amount, calculated on oxide, of 0.5 mol% to 20 mol%, 0.5 mol% to 15 mol%, 3 mol% to 20 mol%, or 3 mol% to 15 mol%. In this case, the ceramic sheet of the present disclosure may be a zirconia sheet containing at least one rare earth element selected from the group consisting of scandium, yttrium, and cerium in a total amount, calculated on oxide, of 0.5 mol% to 20 mol%, 0.5 mol% to 15 mol%, 3 mol% to 20 mol%, or 3 mol% to 15 mol%.

[0016] When scandium is included as a rare earth element, the stabilized zirconia-based ceramic may be referred to as scandia-stabilized zirconia (ScSZ). When yttrium is included as a rare earth element, the stabilized zirconia-based ceramic may be referred to as yttria-stabilized zirconia (YSZ). When scandium and cerium are included as rare earth elements, the stabilized zirconia-based ceramic may be referred to as scandia-ceria-stabilized zirconia (ScCeSZ). The stabilized zirconia-based ceramic can be obtained, for example, by heat-treating a mixture of commercially available zirconia powder and a powdered rare earth element, followed by pulverizing the mixture. The heat-treated mixture may be a calcined or sintered compact of commercially available zirconia powder and a powdered rare earth element.

[0017] The stabilized zirconia powder may be a cubic stabilized zirconia powder or a tetragonal stabilized zirconia powder. Cubic zirconia powder is a powder containing cubic zirconia as a zirconia-based oxide as the main component (main crystalline phase). Cubic zirconia is a substance in which a line peak attributed to cubic zirconia is observed by X-ray diffraction. Tetragonal zirconia powder is a powder containing tetragonal zirconia as a zirconia-based oxide as the main component (main crystalline phase). Tetragonal zirconia is a substance in which a line peak attributed to tetragonal zirconia is observed by X-ray diffraction.

[0018] In one embodiment, a cubic zirconia powder or a tetragonal zirconia powder satisfying a specific particle size distribution may be used as the raw zirconia powder. When a cubic zirconia powder is used as the raw zirconia powder, the cubic crystal ratio (%) of the powder is, for example, 50% or more. The cubic crystal ratio may be 60% or more, 80% or more, 90% or more, or 95% or more. When a tetragonal zirconia powder is used as the raw zirconia powder, the tetragonal crystal ratio (%) of the powder is, for example, 50% or more. The tetragonal crystal ratio may be 60% or more, 80% or more, 90% or more, or 95% or more. The average primary particle diameter of the cubic zirconia powder or the tetragonal zirconia powder is, for example, 0.003 μm or more and 0.2 μm or less, and may be 0.005 μm or more and 0.15 μm or less. The average primary particle size is calculated, for example, from the results of measurement using a transmission electron microscope. When the raw zirconia powder is a cubic zirconia powder or a tetragonal zirconia powder, the raw zirconia powder may contain a stabilizer or the like, as necessary.

[0019] The ceramic powder may contain, in addition to zirconia powder, powders of alumina, ceria, titania, silica, niobium oxide, thallium oxide, mullite, cordierite, spinel, forsterite, anorthite, celsian, enstatite, aluminum nitride, silicon nitride, etc., within a range that does not impair the desired effect. The content of the powder may be, for example, 0.01% by mass or more and 5% by mass or less, or 0.05% by mass or more and 3% by mass or less, relative to the total amount of the raw material powders.

[0020] The 50 volume % diameter (D50) of the ceramic powder is, for example, 0.05 μm or more and 0.8 μm or less, and the 90 volume % diameter (D90) is, for example, 0.3 μm or more and 1.5 μm or less. Having a D90 of 1.5 μm or less prevents excessively large aggregates of the ceramic powder. Therefore, the resulting ceramic sheet is well densified. On the other hand, having a D90 of 0.3 μm or more improves the dispersibility of the ceramic powder during slurry preparation. The D90 may be 0.5 μm or more, 0.6 μm or more, 1.0 μm or less, or 0.8 μm or less. The 10 volume % diameter (D10) of the ceramic powder is, for example, 0.03 μm or more and 0.6 μm or less. In this case, the small number of fine particles in the ceramic powder reduces the occurrence of localized sintering, non-uniform sintering, etc. D10 may be 0.06 μm or more, 0.1 μm or more, 0.6 μm or less, 0.5 μm or less, or 0.4 μm or less.

[0021] The 50% by volume diameter (D50) is measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., product name "LA-920") and is the particle diameter value at 50% by volume of the total particle volume when the particle volumes are integrated from the smallest particle diameter. Similarly, the 90% by volume diameter and the 10% by volume diameter are the particle diameter values ​​at 90% by volume and 10% by volume of the total particle volume when the particle volumes are integrated from the smallest particle diameter. The particle size distribution of the ceramic powder can be adjusted by a combination of pulverization using a ball mill, bead mill, planetary mill, jet mill, etc., and classification using a cyclone classifier, etc. Alternatively, a commercially available product having the desired particle size distribution may be used.

[0022] As shown in FIG. 1 , the ceramic sheet 1 has a first main surface 1a, a second main surface 1b, and a side surface 1c. Each of the first main surface 1a and the second main surface 1b intersects the thickness direction of the ceramic sheet 1, and a thin film such as a conductive layer for an electrode may be formed on each of the first main surface 1a and the second main surface 1b. In one embodiment, the first main surface 1a and the second main surface 1b each have a square shape, but this is not limited thereto. Each of the first main surface 1a and the second main surface 1b may have a circular shape, an elliptical shape, or a polygonal shape such as a triangular shape or a rectangular shape. The side surface 1c is a surface connecting the first main surface 1a and the second main surface 1b. In one embodiment, the ceramic sheet 1 has four quadrangular side surfaces 1c, but this is not limited thereto. For example, when the first main surface 1a and the second main surface 1b each have a circular shape, the ceramic sheet 1 has one ring-shaped side surface 1c.

[0023] In one embodiment, the area of ​​each of the first main surface 1a and the second main surface 1b is 100 cm ２ More than 400cm ２ The thickness of the ceramic sheet 1 is 30 μm or more and 200 μm or less, and the weight per unit area of ​​the main surface of the ceramic sheet 1 is 0.015 g / cm ２ 0.15g / cm or more ２ In this case, it can be said that the ceramic sheet 1 is relatively large and the weight of the ceramic sheet 1 is relatively small.

[0024] In one embodiment, at least one of the first main surface 1a and the second main surface 1b is a roughened surface. In other words, at least one of the first main surface 1a and the second main surface 1b is roughened. The roughening treatment of the ceramic sheet 1 is performed, for example, during the production of a green sheet, which is the raw material for the ceramic sheet 1. In one example, the roughening treatment is performed by applying a slurry to a film on which a predetermined unevenness has been formed in advance and drying it to form a green sheet. In this case, unevenness reflecting the predetermined unevenness is formed on the surface of the green sheet that contacts the film. Alternatively, the roughening treatment may be performed by contacting and pressurizing a material having a predetermined unevenness with the surface of the green sheet. Alternatively, the roughening treatment may be performed by chemically etching the green sheet. In this case, the conditions for the roughening treatment are appropriately adjusted. The film on which the predetermined unevenness is formed is, for example, a film that has been chemically etched in advance, but is not limited thereto. However, when a film or paper provided with a coating layer containing a filler is used as the film on which the predetermined irregularities are formed, the ceramic sheet 1 tends to fail to satisfy any of the parameters described below. The film is, for example, a resin film such as polyethylene terephthalate (PET) film that has a predetermined thickness and exhibits flexibility.

[0025] In one embodiment, the arithmetic mean roughness (Ra) of each of the first main surface 1a and the second main surface 1b is 0.01 μm or more and 1.0 μm or less. The arithmetic mean roughness may be 0.01 μm or more and 0.7 μm or less, 0.01 μm or more and 0.5 μm or less, 0.01 μm or more and 0.4 μm or less, 0.1 μm or more and 1.0 μm or less, 0.1 μm or more and 0.7 μm or less, 0.1 μm or more and 0.5 μm or less, 0.1 μm or more and 0.4 μm or less, or 0.15 μm or less. The surface roughness (arithmetic mean roughness) of each of the first main surface 1 a and the second main surface 1 b is measured, for example, by a known surface roughness measuring device.

[0026] In one example, the kurtosis (Rku) of at least one of the first main surface 1a and the second main surface 1b is, for example, less than 3. Kurtosis refers to kurtosis, a measure of surface sharpness. A surface with a kurtosis greater than 3 tends to have sharp recesses and protrusions. A surface with a kurtosis less than 3 tends to have a flattened height distribution of the irregularities. Therefore, it can be said that sharp recesses and protrusions are less likely to exist on at least one of the first main surface 1a and the second main surface 1b. This reduces the likelihood of localized stress concentration in the ceramic sheet 1, i.e., of crack initiation points in the ceramic sheet 1. The kurtosis of each of the first main surface 1a and the second main surface 1b is measured, for example, using a known contact surface roughness measuring device such as a stylus-type or a non-contact surface roughness measuring device such as a laser microscope. The kurtosis may be 3.46 or less or 2.39 or less.

[0027] In one example, the grain size of at least one of the first and second principal surfaces 1a and 1b is 90% to 130% of the grain size of the side surface 1c. In this case, the variation between grains within the ceramic sheet 1 is small, and the ceramic sheet 1 can be evaluated as having high quality. The grain size of at least one of the first and second principal surfaces 1a and 1b may be 90% to 115.1%, 107.1% to 115.1%, or 107.1% to 130% of the grain size of the side surface 1c. Each grain size corresponds to the average particle diameter obtained, for example, by image analysis of a 3000x magnification photograph taken with a scanning electron microscope. In one example, the area of ​​each grain in the photograph is first calculated using image analysis software, and then the average area of ​​the grains is calculated. Next, assuming the shape of the grain is circular, the diameter calculated from the average area using the formula for the area of ​​a circle is treated as the grain size. The grain size of at least one of the first and second principal surfaces 1a and 1b and the grain size of the side surface 1c are, for example, 0.3 μm to 5.0 μm, but are not limited thereto. Generally, when depressions smaller than the grain size are formed on the surface of a ceramic sheet, grain growth on the surface tends to be inhibited, resulting in a smaller grain size on the surface. Therefore, the grain size on the surface with the relatively small irregularities tends to be significantly different from the grain size on the other surfaces.

[0028] In one embodiment, when first main surface 1a and second main surface 1b are each measured with a laser microscope, the average value of the difference between the highest point and the lowest point in any 10 sections on at least one of first main surface 1a and second main surface 1b is 1.0 μm or more and 4.0 μm or less. A surface for which this average value falls within the above numerical range can be evaluated as a surface on which recesses are formed to an appropriate depth and / or protrusions are formed to an appropriate height. In other words, a surface for which the above average value is 1.0 μm or more and 4.0 μm or less can be evaluated as not being a smooth surface, and as not having excessively large irregularities formed on the surface. The average value may be 1.0 μm or more and 3.0 μm or less, 1.0 μm or more and 2.5 μm or less, 1.0 μm or more and 2.0 μm or less, 1.2 μm or more and 4.0 μm or less, 1.2 μm or more and 3.0 μm or less, 1.2 μm or more and 2.5 μm or less, 1.2 μm or more and 2.0 μm or less, 1.5 μm or more and 4.0 μm or less, 1.5 μm or more and 3.0 μm or less, 1.5 μm or more and 2.5 μm or less, or 1.5 μm or more and 2.0 μm or less. The average value may be obtained, for example, by performing shape analysis of the surface profile using a laser microscope. When calculating the average value of the differences between the highest and lowest points in any 10 sections on each of the first main surface 1a and the second main surface 1b, the standard deviation of the differences between the highest and lowest points in any 10 sections may also be calculated. The standard deviation of the differences between the highest and lowest points in any 10 sections on at least one of the first main surface 1a and the second main surface 1b is, for example, 0.10 or more and 1.0 or less, but is not limited to this. The standard deviation of the differences between the highest and lowest points in any 10 sections on at least one of the first main surface 1a and the second main surface 1b can be calculated using a known method.

[0029] Here, referring to FIG. 2 , an example of a method for calculating the difference between the highest point and the lowest point in an arbitrary section on the first principal surface 1a will be described. The aforementioned arbitrary section corresponds to a 150 μm long section arbitrarily extracted from an area obtained by photographing a portion of the first principal surface 1a with a 100x objective lens. FIG. 2 is a graph showing the results of shape analysis of the surface profile of an arbitrary section on the first principal surface 1a using a laser microscope. In FIG. 2 , the vertical axis represents height, and the horizontal axis represents the measurement distance. In graph 10 shown in FIG. 2 , line 11 represents the highest point in the arbitrary section, line 12 represents the lowest point in the arbitrary section, and arrow 13 represents the difference between the highest point and the lowest point in the arbitrary section. By performing shape analysis of the surface profile of an arbitrary section on the first principal surface 1a in this manner, the difference between the highest point and the lowest point in the arbitrary section can be calculated. Using a similar method, the differences between the highest point and the lowest point in any nine sections of the first principal surface 1a other than the aforementioned arbitrary section can be calculated, thereby calculating the average value of the differences between the highest point and the lowest point in any ten sections. In one example, the arbitrary 10 sections are sections extracted from the same first main surface 1a. In this case, at least one of the arbitrary 9 sections may be a section extracted from an area where the above-mentioned portion of the first main surface 1a is photographed, but this is not limited to this. Each of the arbitrary 10 sections on the first main surface 1a may be a section extracted from a different photographed area. In another example, each of the arbitrary 10 sections is a section extracted from a different first main surface 1a. That is, the arbitrary 10 sections are extracted from 10 ceramic sheets 1. Note that the average value of the differences between the highest and lowest points of the arbitrary 10 sections on the second main surface 1b is also calculated using the above method. The arbitrary 10 sections on the second main surface 1b may be extracted from one ceramic sheet 1 or from multiple ceramic sheets 1.

[0030] The coefficient of variation (Cv value) of the difference between the highest point and the lowest point in any of the 10 sections described above is, for example, 0.05 or more and 0.3 or less. A surface whose coefficient of variation falls within the above numerical range can be evaluated as a surface on which unevenness tends to be uniformly formed. The coefficient of variation may be 0.05 or more and 0.20 or less, 0.05 or more and 0.15 or less, 0.05 or more and 0.13 or less, 0.09 or more and 0.3 or less, 0.09 or more and 0.2 or less, 0.09 or more and 0.15 or less, 0.09 or more and 0.13 or less, 0.10 or more and 0.3 or less, 0.10 or more and 0.20 or less, 0.10 or more and 0.15 or less, or 0.10 or more and 0.13 or less. The coefficient of variation of the difference between the highest point and the lowest point of any 10 sections on the first main surface 1a corresponds to the value obtained by dividing the standard deviation of the difference by the average value (standard deviation of the difference / average value).

[0031] For example, the first average value is the average of the differences between the highest and lowest points in any 10 sections on the first main surface 1a, the second average value is the average of the differences between the highest and lowest points in any 10 sections on the second main surface 1b, the first coefficient of variation is the coefficient of variation of the differences between the highest and lowest points in any 10 sections on the first main surface 1a, and the second coefficient of variation is the coefficient of variation of the differences between the highest and lowest points in any 10 sections on the second main surface 1b. In this case, in one embodiment, the difference between the first average value and the second average value may be 0.1 μm or more and less than 0.8 μm, and the difference between the first coefficient of variation and the second coefficient of variation may be 0 or more and 0.1 or less. In this case, a decrease in strength of the ceramic sheet 1 due to at least one of the surface shapes of the first main surface 1a and the second main surface 1b is less likely to occur. In addition, between two adjacent ceramic sheets 1, the first main surface 1a or the second main surface 1b of one ceramic sheet 1 is less likely to adhere to the first main surface 1a or the second main surface 1b of the other ceramic sheet 1. Therefore, when the ceramic sheets 1 are stacked together, the phenomenon in which the two adjacent ceramic sheets 1 adhere to each other and are difficult to peel off, and the phenomenon of the above-mentioned double-sheeting of the ceramic sheets 1, are less likely to occur.

[0032] In one embodiment, when each of the first major surface 1a and the second major surface 1b is measured using a laser microscope, the cumulative relative frequency of an approximate line calculated every 1.314 μm on at least one of the first major surface 1a and the second major surface 1b, where the slope of the approximate line is -0.1 to 0.1, is 20% to 70%; the cumulative relative frequency of an approximate line where the slope of the approximate line is -0.3 to 0.3 is 85% to 100%; and the cumulative relative frequency of an approximate line where the slope of the approximate line is -1.5 to 1.5 is 99.9% to 100%. A surface where the approximate line satisfies all of the above numerical ranges can be evaluated as a surface with relatively few smooth portions, where smooth concave and convex portions account for the majority, and where large concave and convex portions are almost absent. The cumulative relative frequency of an approximate line where the slope of the approximate line is -0.1 to 0.1 may be 20% to 60.3% or 20% to 48.9%. The cumulative relative frequency when the slope of the approximation curve is -0.3 or more and 0.3 or less may be 94.2% or more and 100% or less, or 97.2% or more and 100% or less. The cumulative relative frequency when the slope of the approximation curve is -1.5 or more and 1.5 or less may be 100%. The cumulative relative frequency when the slope of the approximation line is -1.0 or more and 1.0 or less may be 99.0% or more and 100% or less, or 99.9% or more and 100% or less. The cumulative relative frequency when the slope of the approximation line is -0.5 or more and 0.5 or less may be 99.0% or more and 100% or less, or 99.1% or more and 100% or less, or 99.8% or more and 100% or less. On both the first main surface 1a and the second main surface 1b, the cumulative relative frequency when the slope of the approximate straight line is -0.3 or more and 0.3 or less may be 85% or more and 100% or less, and the cumulative relative frequency when the slope of the approximate straight line is -1.5 or more and 1.5 or less may be 99.9% or more and 100% or less, or the cumulative relative frequency when the slope of the approximate straight line is -0.3 or more and 0.3 or less may be 94.2% or more and 100% or less, and the cumulative relative frequency when the slope of the approximate straight line is -1.5 or more and 1.5 or less may be 99.9% or more and 100% or less, or the cumulative relative frequency when the slope of the approximate straight line is -0.3 or more and 0.3 or less may be 97.2% or more and 100% or less, and the cumulative relative frequency when the slope of the approximate straight line is -1.5 or more and 1.5 or less may be 99.9% or more and 100% or less.

[0033] The slope of the approximate line on the first principal surface 1a can be calculated from the results of shape analysis of the surface profile of any one section of the first principal surface 1a using a laser microscope. Similarly, the slope of the approximate line on the second principal surface 1b can be calculated from the results of shape analysis of the surface profile of any one section of the second principal surface 1b using a laser microscope. Here, with reference to FIG. 3, an example of a method for calculating the slope of the approximate line calculated every 1.314 μm of any one section of the first principal surface 1a will be described. FIG. 3 is a graph that enlarges a portion of FIG. 2. In FIG. 3, the vertical axis represents height and the horizontal axis represents measurement distance. Graph 20 shown in FIG. 3 is formed from a large number of plots. These plots represent surface shape profiles acquired at 0.146 μm intervals. Therefore, the slope of the approximate line can be calculated by creating an approximate line using 10 consecutive plots, including the starting point of any one section, from the large number of plots described above.

[0034] In one embodiment, the slope of the approximate line is calculated each time the starting point is shifted by one point. This calculates the slopes of approximate lines 21-24, etc., shown in FIG. 3 . This calculation of the slopes of the approximate lines is repeated until the slope of the approximate line formed by the plot of 10 points, including the end point of the arbitrary section, is calculated. In this manner, the slopes of multiple approximate lines are calculated for the arbitrary section on the first major surface 1a. Furthermore, using a similar method, the slopes of multiple approximate lines are calculated for each of nine arbitrary sections on the first major surface 1a other than the arbitrary section. Then, the slopes of all the approximate lines obtained for the arbitrary ten sections are classified into classes. This process obtains the cumulative relative frequency when the slopes of the approximate lines calculated every 1.314 μm on the first major surface 1a fall into a predetermined class (e.g., a slope of −0.1 or greater and 0.1 or less). The cumulative relative frequency of the gradient of the approximate line calculated every 1.314 μm on the second main surface 1b is also calculated by the same method as for the first main surface 1a.

[0035] In one embodiment, the three-point bending strength of the ceramic sheet 1 is, for example, 400 MPa or more, and the Weibull modulus of the ceramic sheet 1 is, for example, 9.0 or more. In this case, the strength of the ceramic sheet 1 tends to be comparable to the strength of a ceramic sheet that has not been subjected to a roughening treatment. The three-point bending strength may be 410 MPa or more, or 430 MPa or more. The three-point bending strength of the ceramic sheet 1 is measured, for example, by a method in accordance with JIS R 1601:2008. The Weibull modulus is obtained from the results of measuring the three-point bending strength of multiple ceramic sheets 1.

[0036] An example of a method for manufacturing a ceramic sheet 1 according to one embodiment will be described below. First, a slurry is prepared by mixing the ceramic powder, solvent, and binder (first step). In the first step, the ceramic powder, solvent, and binder are mixed using a milling device such as a ball mill, bead mill, planetary mill, or jet mill. For example, the ceramic powder, solvent, and binder are mixed in the milling device for 10 minutes to 5,000 minutes. In preparing the slurry, the milling time for the ceramic powder may be, for example, 30 minutes or less, 25 minutes or less, or 20 minutes or less. In addition, in the first step, a degassing treatment of the slurry may be performed using a known method. Agglomerated particles of the ceramic powder, such as the stabilized zirconia powder, may be present in the slurry. In other words, the slurry may be prepared so that the agglomerated particles are present.

[0037] The type of solvent contained in the slurry is not limited and can be appropriately selected from solvents used in conventional ceramic sheet production. Examples of solvents include water; alcohols such as ethanol, 2-propanol, 1-butanol, and 1-hexanol; ketones such as acetone and 2-butanone; aliphatic hydrocarbons such as pentane, hexane, and heptane; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and acetate esters such as methyl acetate, ethyl acetate, and butyl acetate. The above solvents may be used alone or in combination. The content of the solvent relative to the total mass of the slurry is, for example, 20% by mass or more and 90% by mass or less.

[0038] The type of binder used in the slurry is not limited and can be appropriately selected from organic binders and inorganic binders used in conventional ceramic sheet production. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl acetal resins, vinyl formal resins, polyvinyl butyral resins, vinyl alcohol resins, celluloses such as ethyl cellulose, and waxes. Examples of inorganic binders that can be used include at least one selected from zirconia sol, silica sol, alumina sol, and titania sol.

[0039] The mass ratio of the ceramic powder to the binder in the slurry is not particularly limited. For example, the binder may be 5 to 30 parts by mass, or 10 to 20 parts by mass, per 100 parts by mass of the ceramic powder. The content of the binder in the slurry is appropriately selected taking into consideration the particle size of the ceramic powder and the strength and flexibility required for the ceramic sheet to be manufactured. Furthermore, the slurry may further contain known dispersants, plasticizers, lubricants, surfactants, and / or antifoaming agents, etc., as necessary.

[0040] Next, the slurry is coated in a sheet form and then dried to form a green sheet (second step). In the second step, the slurry is first coated onto a substrate film (on the surface of the substrate film to be coated). The coated slurry is then dried to form a green sheet on the substrate film. Examples of methods for coating the slurry onto the substrate film in a sheet form include tape casting and doctor blade methods. In the second step, screen printing may be performed, or a slot die coater, lip coater, gravure coater, or the like may be used.

[0041] In one embodiment, the surface of the substrate film to be coated is surface-treated with an alkaline chemical solution. Examples of surface treatment methods using an alkaline chemical solution include etching the surface of the substrate film using an alkaline chemical solution such as a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, or an ammonia aqueous solution. The concentration of the alkaline chemical solution may be, for example, 0.5% by mass or more and 50% by mass or less. In one embodiment, the surface of the substrate film to be coated may be surface-treated using plasma or an ion beam. Examples of surface treatment methods using plasma or an ion beam include dry etching using plasma or an ion beam. The surface of the substrate film to be coated may be subjected to a single surface treatment from the above-mentioned surface treatments, or multiple surface treatments. The arithmetic mean roughness of the surface of the substrate film to be coated is 0.2 μm or more and 0.7 μm or less. The arithmetic mean roughness may be 0.2 μm or more and 0.6 μm or less, 0.3 μm or more and 0.7 μm or less, or 0.3 μm or more and 0.6 μm or less. The arithmetic mean roughness is measured, for example, by a known surface roughness measuring device. By applying the slurry to the substrate film (the surface to be coated of the substrate film), the contact surface of the green sheet that comes into contact with the substrate film (the surface that corresponds to the first main surface 1 a of the ceramic sheet 1) has an arithmetic mean roughness that reflects the predetermined arithmetic mean roughness.

[0042] In one embodiment, a resin film having a predetermined unevenness is used as the substrate film, and by applying a slurry onto the resin film, unevenness reflecting the predetermined unevenness is formed on the contact surface of the green sheet that comes into contact with the resin film (the surface that will later correspond to the first main surface 1 a of the ceramic sheet 1).

[0043] Next, the green sheet is degreased to form a degreased body of the green sheet (step 3). In step 3, the green sheet is first peeled from the base film. Subsequently, the green sheet is heat-treated to form a degreased body from which organic components (binders and other organic additives) have been removed. The heat treatment is not particularly limited, and a conventionally known method can be used. The heat treatment conditions in step 3 are also not particularly limited, and are set to known conditions, for example. For example, the degreased body is formed by heating the green sheet at a heat treatment temperature of 100°C to 450°C for a heat treatment time of approximately 2 hours to 50 hours. The degreased body formed in step 3 is an intermediate ceramic sheet and corresponds to a sheet-like member from which organic components have been removed from the green sheet. The heat treatment temperature in step 3 may be 370°C to 450°C, 400°C to 450°C, or even 400°C. Here, the heat treatment temperature refers to the maximum temperature in the heat treatment, and the heat treatment time refers to the time maintained at the heat treatment temperature.

[0044] In the third step, multiple green sheets may be heat-treated while stacked on top of each other. In this case, a spacer such as an alumina sheet may or may not be provided between two adjacent green sheets. If unevenness is formed on the contact surfaces of the green sheets in the second step, a laminate consisting of only multiple green sheets may be heat-treated in the third step. In this case, the unevenness formed on the contact surfaces of each green sheet reduces the contact area between two adjacent green sheets. Therefore, adhesion between the green sheets and between the degreased sheets can be prevented in the third step. Here, an organic powder may be sprinkled between the two adjacent green sheets to effectively prevent adhesion between the green sheets. The organic powder may be, for example, a natural organic powder such as edible cornstarch, or a synthetic organic resin powder such as a sublimable resin powder such as melamine cyanurate. The amount of organic powder used is, for example, 0.005 mg / cm relative to the area of ​​the green sheets. ２ 2mg / cm or more ２ The number of green sheets to be stacked depends on the area of ​​the green sheets, but is, for example, 2 to 40 sheets.

[0045] Next, the degreased body is fired to form a ceramic sheet (step 4). In step 4, the degreased body is fired at a high temperature to form a sintered ceramic sheet. The firing conditions in step 4 are not particularly limited and are set to known conditions, for example. The sintering temperature (firing temperature) in step 4 is, for example, 1200°C to 1600°C, 1200°C to 1500°C, 1200°C to 1450°C, 1300°C to 1600°C, 1300°C to 1500°C, 1300°C to 1450°C, 1350°C to 1600°C, 1350°C to 1500°C, or 1350°C to 1450°C. The heating time from the heat treatment temperature (e.g., 400°C, 450°C, etc.) to the sintering temperature is, for example, 8 hours to 30 hours. The fourth step is carried out, for example, in an air atmosphere or a low-oxygen atmosphere. In the fourth step, the plurality of degreased bodies may be fired in a stacked state, as in the third step. In this case, the resting state of the plurality of degreased bodies is the same as the resting state of the plurality of green sheets in the third step, but is not limited to this.

[0046] In the ceramic sheet 1 according to the embodiment described above, the arithmetic mean roughness of each of the first principal surface 1a and the second principal surface 1b is 0.1 μm to 1.0 μm. When the first principal surface 1a and the second principal surface 1b are measured with a laser microscope, the average value of the difference between the highest point and the lowest point in any 10 sections on at least one of the first principal surface 1a and the second principal surface 1b is 1.0 μm to 4.0 μm, the coefficient of variation of the difference between the highest point and the lowest point in any 10 sections is 0.05 to 0.3, the cumulative relative frequency of the approximate line with a slope of −0.1 to 0.1 calculated every 1.314 μm is 20% to 70%, the cumulative relative frequency of the approximate line with a slope of −0.3 to 0.3 is 85% to 100%, and the cumulative relative frequency of the approximate line with a slope of −1.5 to 1.5 is 99.9% to 100%. As a result, at least one of the first and second main surfaces 1a and 1b of the ceramic sheet 1 is not a smooth surface, but rather has relatively few large irregularities, is relatively smooth, and is mostly composed of smooth depressions and protrusions. In other words, at least one of the first and second main surfaces 1a and 1b of the ceramic sheet 1 has smooth undulations throughout its surface, with few large depressions or protrusions. This reduces the likelihood of a decrease in strength of the ceramic sheet 1 due to the surface shape of the first and / or second main surfaces 1a and 1b. Additionally, at least one of the first and / or second main surfaces 1a and 1b of the ceramic sheet 1 is less likely to adhere to the first and / or second main surfaces 1a and 1b of another ceramic sheet 1. Therefore, according to one embodiment, a ceramic sheet 1 can be provided that can prevent double-cutting while maintaining the strength of the ceramic sheet 1.

[0047] In one embodiment, the cumulative relative frequency when the slope of the approximate line is between -1.0 and 1.0 may be between 99.0% and 100%, and the cumulative relative frequency when the slope of the approximate line is between -0.5 and 0.5 may be between 99.0% and 100%. In these cases, at least one of the first main surface 1a and the second main surface 1b can be said to be a surface that is almost free of even relatively large recesses and protrusions. Therefore, a decrease in strength of the ceramic sheet 1 due to the surface shape of at least one of the first main surface 1a and the second main surface 1b is unlikely to occur.

[0048] In one embodiment, the cumulative relative frequency of the approximate straight lines with a slope of -0.3 to 0.3 on both the first and second main surfaces 1a and 1b may be 85% to 100%, and the cumulative relative frequency of the approximate straight lines with a slope of -1.5 to 1.5 may be 99.9% to 100%. In this case, most of the recesses and protrusions formed on both the first and second main surfaces 1a and 1b can be considered smooth. Therefore, a decrease in the strength of the ceramic sheet 1 due to the surface shapes of the first and second main surfaces 1a and 1b is unlikely to occur.

[0049] In one embodiment, the ceramic sheet 1 has a side surface 1c connecting the first main surface 1a and the second main surface 1b, and the grain size of at least one of the first main surface 1a and the second main surface 1b may be 90% to 130% of the grain size of the side surface 1c. In this case, at least one of the first main surface 1a and the second main surface 1b is free of grain growth suppression due to the formation of depressions, i.e., it can be said that the surface is free of residual stress resulting from the suppression of grain growth on the roughened surface after sintering. Therefore, a decrease in strength of the ceramic sheet 1 due to the surface shape of at least one of the first main surface 1a and the second main surface 1b is unlikely to occur.

[0050] The above-mentioned double-sheet ceramic sheet taking-up is more likely to occur as the area of ​​the main surface of the ceramic sheet increases and as the ceramic sheet becomes lighter. Therefore, in one embodiment, the thickness of the ceramic sheet 1 is 30 μm or more and 200 μm or less, and the area of ​​each of the first main surface 1 a and the second main surface 1 b is 100 cm ２ More than 400cm ２Hereinafter, the weight of the ceramic sheet 1 is 0.015 g / cm ２ 0.15g / cm or more ２ or less. In this case, the ceramic sheet 1 is relatively large, and the weight per unit area of ​​the main surface of the ceramic sheet 1 is relatively small. Here, the surface shape of the present disclosure is imparted to the ceramic sheet 1. Therefore, when only the uppermost ceramic sheet 1 in a stack in which multiple ceramic sheets 1 are directly stacked on top of each other is adsorbed and transported, it is possible to prevent two ceramic sheets 1 from being taken up.

[0051] In one embodiment, the first average value is the average of the differences between the highest and lowest points in any 10 sections on the first main surface 1 a, the second average value is the average of the differences between the highest and lowest points in any 10 sections on the second main surface 1 b, the first coefficient of variation is the coefficient of variation of the differences between the highest and lowest points in any 10 sections on the first main surface 1 a, and the second coefficient of variation is the coefficient of variation of the differences between the highest and lowest points in any 10 sections on the second main surface 1 b. In this case, the ceramic sheet 1 is less likely to have a strength reduction due to at least one of the surface shapes of the first main surface 1 a and the second main surface 1 b. In addition, between two adjacent ceramic sheets 1, it becomes difficult for the first main surface 1a or second main surface 1b of one ceramic sheet 1 to adhere well to the first main surface 1a or second main surface 1b of the other ceramic sheet 1.

[0052] In one embodiment, the average value of the kurtosis (Rku) of at least one of the first main surface 1 a and the second main surface 1 b may be less than 3. In this case, the ceramic sheet 1 is less likely to have locations where stress is locally concentrated, i.e., locations that can become crack initiation points.

[0053] In one embodiment, the ceramic sheet 1 may be a zirconia sheet containing at least one rare earth element selected from the group consisting of scandium, yttrium, and cerium in a total amount of 3 mol % to 15 mol % calculated as oxides, which allows the ceramic sheet 1 to function well as a solid electrolyte for an SOFC.

[0054] The method for producing the ceramic sheet 1 according to the embodiment described above includes a first step of preparing a slurry by mixing ceramic powder, a binder, and a solvent, a second step of forming a green sheet by applying the slurry to the surface of a substrate film to be coated, a third step of degreasing the green sheet to form a degreased body of the green sheet, and a fourth step of firing the degreased body to form a ceramic sheet, wherein in the third step, the green sheet is heat-treated at a heat treatment temperature of 100° C. to 450° C., and in the fourth step, the degreased body is fired at a firing temperature of 1200° C. to 1600° C. This provides a method for producing the ceramic sheet 1 that can prevent double-cutting while maintaining the strength of the ceramic sheet 1.

[0055] In one embodiment, the surface to be coated may be surface-treated with an alkaline chemical solution, the heat treatment temperature may be 370°C or higher and 450°C or lower, and the firing temperature may be 1350°C or higher and 1450°C or lower. In this case, the ceramic sheet 1 can be more suitably produced. Here, the arithmetic mean roughness of the surface to be coated of the substrate film may be 0.2 μm or higher and 0.7 μm or lower, or 0.3 μm or higher and 0.6 μm or lower. In these cases, the appropriate surface roughness is transferred to the surface of the green sheet in contact with the surface to be coated, thereby forming the ceramic sheet 1 with the appropriate surface roughness. Therefore, it is possible to successfully produce a ceramic sheet 1 that can prevent double-cutting while maintaining the strength of the ceramic sheet 1.

[0056] In one embodiment, the ceramic powder may be a zirconia-based powder, in which case a ceramic sheet 1 that can function well as a solid electrolyte for an SOFC can be produced.

[0057] In one embodiment, the second step may be a step of forming a green sheet by applying the slurry to the surface of a substrate film by a doctor blade method, which facilitates the production of a ceramic sheet 1 having an arithmetic mean roughness of 0.01 μm or more and 1.0 μm or less on each of the first and second principal surfaces.

[0058] The above embodiment describes one aspect of the present disclosure, and therefore the present disclosure may be modified without being limited to the above embodiment.

[0059] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0060] Example 1: A stabilized zirconia powder containing 10 mol% scandium oxide and 1 mol% cerium oxide as a solid solution (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., product name "10Sc1CeSZ", D50: approximately 0.5 μm) was prepared as a raw material powder. Next, 100 parts by mass of the raw material powder, 3.5 parts by mass of a dispersant (a commercially available polycarboxylic acid ester-type polymer dispersant), and 50 parts by mass of a toluene / ethyl acetate (mass ratio = 1:1) mixed solvent were placed in a nylon mill charged with zirconia balls. The raw material powder, dispersant, and mixed solvent were milled for 1 hour to prepare Slurry I. Next, 18.5 parts by mass (solids equivalent) of a binder made of a methacrylic copolymer (number average molecular weight: 100,000, glass transition temperature: 0°C) and 1.5 parts by mass of dibutyl phthalate as a plasticizer were added to the nylon mill containing Slurry I, and milled again for 20 hours to prepare Slurry II. The obtained slurry II was transferred to a jacketed, round-bottomed, cylindrical vacuum degassing vessel equipped with an anchor-shaped stirrer, and concentrated and degassed under reduced pressure at a jacket temperature of 40°C while rotating the stirrer at a speed of 30 rpm, and the viscosity at 25°C was adjusted to 3 Pa s to obtain a raw material slurry for coating.

[0061] Next, the raw material slurry was applied to a substrate film in a coating device to form a coating film. Here, the raw material slurry was continuously applied by a doctor blade method. A PET film (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.45 μm) that had been surface-treated with an alkaline chemical solution was used as the substrate film, and the raw material slurry was applied to the surface-treated side (the surface to be coated) of the PET film. Subsequently, the coating film on the substrate film was dried at 100°C in the coating device for about 1 hour to obtain a long solid electrolyte green sheet with a thickness of about 0.12 mm. Next, the long green sheet was punched out using a Thomson blade with sides of about 200 mm and peeled off from the PET film to obtain a roughly square green sheet. Hereinafter, the surface of the green sheet that was in contact with the PET film, which is the base film (i.e., the contact surface of the green sheet), may be referred to as the "PET surface," and the surface opposite the PET surface that was not in contact with the base film (i.e., the exposed surface of the green sheet) may be referred to as the "air surface."

[0062] Next, two 200 mm square alumina porous sheets (porosity: 20%, thickness: 0.2 mm) were stacked on a firing shelf. The above green sheet was then placed on top of the two stacked alumina porous sheets. At this time, the green sheet was placed on top of the alumina porous sheet so that the air side faced the alumina porous sheet. Thereafter, the above green sheets and the above alumina porous sheets were alternately stacked, using the alumina porous sheets of the above dimensions as spacer sheets. Finally, another alumina porous sheet of the above dimensions was placed on top of the topmost alumina porous sheet to form a laminate. Then, 20 similar laminates were prepared. Here, each laminate contained five green sheets.

[0063] Next, the temperature was raised from room temperature to 400°C over 30 hours in a batch-type hot air circulation electric furnace, and each green sheet in the laminate was degreased. Next, 20 sets of laminates containing the degreased bodies were transferred to a batch-type firing furnace, where the temperature was raised from room temperature to 400°C over 3 hours, and then from 400°C to 1430°C over 24 hours. The laminates were then held at 1430°C for 3 hours and cooled to 900°C over 6 hours. The sheets were then allowed to cool to room temperature in the firing furnace, producing 100 ceramic sheets with sides of approximately 150 mm and a thickness of 90 μm. (a) in FIG. 4 is an image of the sheet surface of the PET side of Example 1.

[0064] Example 2 A green sheet with a side length of approximately 140 mm was produced in the same manner as in Example 1, except that a PET film (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.35 μm) that had been surface-treated with an alkaline chemical solution was used as the base film and the thickness of the green sheet was 160 μm.

[0065] Next, two 200 mm square alumina porous sheets (porosity: 20%, thickness: 0.2 mm) were stacked on a firing shelf. The above green sheet was then placed on top of the two stacked alumina porous sheets. At this time, the green sheet was placed on top of the alumina porous sheets so that the air side faced the alumina porous sheets. Next, commercially available food-grade cornstarch was sprinkled on the PET side of the green sheet placed on the alumina porous sheet, and the food-grade cornstarch was spread almost evenly with a brush. Furthermore, commercially available food-grade cornstarch was sprinkled on the PET sides of another nine green sheets, and the food-grade cornstarch was spread almost evenly with a brush. Next, nine green sheets were successively stacked on top of the green sheet placed on the alumina porous sheet, with the PET side sprinkled with food-grade cornstarch facing up. Next, one alumina porous sheet of the above dimensions was placed on top of the ten stacked green sheets to form a laminate. Then, 10 sets of laminates were prepared.

[0066] Next, the temperature was raised from room temperature to 400°C over 30 hours in a batch-type hot air circulation electric furnace, and each green sheet in the laminate was degreased. Next, 10 sets of laminates containing the degreased bodies were transferred to a batch-type firing furnace, where the temperature was raised from room temperature to 400°C over 3 hours, and then from 400°C to 1390°C over 24 hours. The laminates were then held at 1390°C for 3 hours and cooled to 900°C over 6 hours. The sheets were then allowed to cool to room temperature in the firing furnace, producing 100 ceramic sheets with sides of approximately 105 mm and thicknesses of 120 μm. (a) in FIG. 5 is an image of the sheet surface of the PET side of Example 2.

[0067] Example 3 A long green sheet was obtained in the same manner as in Example 1. Next, the long green sheet located on the base film was cut into a roughly square with a side of approximately 220 mm using a rotary cutter. As a result, a green sheet (green sheet with base film) located on the base film cut out with a side of approximately 220 mm was obtained. Next, a PET film (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.45 μm, same film as the base film) that had been surface-treated with an alkaline chemical solution was superimposed on the surface of the green sheet with base film that was exposed from the base film (exposed surface). At this time, the surface-treated surface of the PET film contacted the exposed surface of the green sheet with base film. This formed a green sheet sandwiched between a pair of films. Next, the green sheet sandwiched between a pair of PET films was placed in the press section of a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd., model "S-37.5"), and a pressing temperature of 25°C and a pressing force of 25.0 MPa (256 kgf / cm ２ ), and a pressing time of 20 seconds. After the pressing, the PET film in contact with the exposed surface was peeled off from the green sheet, and then the green sheet with the base film was punched out using a Thomson blade with a side length of approximately 200 mm. The base film was then peeled off from the green sheet to obtain a substantially square green sheet. 100 substantially square green sheets with a side length of approximately 200 mm were obtained by the same procedure.

[0068] Next, the green sheets were degreased and fired in the same manner as in Example 1 to produce 100 ceramic sheets each having a side of approximately 150 mm and a thickness of 90 μm.

[0069] Example 4 A long green sheet was obtained in the same manner as in Example 2. Next, the long green sheet located on the base film was cut into a roughly square with a side of approximately 220 mm using a rotary cutter. As a result, a green sheet (green sheet with base film) located on the base film cut out with a side of approximately 220 mm was obtained. Next, a PET film (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.35 μm, same film as the base film) that had been surface-treated with an alkaline chemical solution was superimposed on the surface of the green sheet with base film that was exposed from the base film (exposed surface). At this time, the surface-treated surface of the PET film contacted the exposed surface of the green sheet with base film. This formed a green sheet sandwiched between a pair of films. Next, the green sheet sandwiched between a pair of PET films was placed in the press section of a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd., model "S-37.5"), and a pressing temperature of 25°C and a pressing force of 25.0 MPa (256 kgf / cm ２ ), and a pressing time of 20 seconds. After the pressing, the PET film in contact with the exposed surface was peeled off from the green sheet, and then the green sheet with the base film was punched out using a Thomson blade with a side length of approximately 140 mm. The base film was then peeled off from the green sheet to obtain a substantially square green sheet. 100 substantially square green sheets with a side length of approximately 140 mm were obtained by the same procedure.

[0070] Next, the green sheets were degreased and fired in the same manner as in Example 2 to produce 100 ceramic sheets each having a side of approximately 105 mm and a thickness of 120 μm.

[0071] <Comparative Example 1> One hundred ceramic sheets were produced in the same manner as in Example 1, except that a commercially available non-surface-treated PET film (film thickness: 125 μm, arithmetic mean roughness (Ra): 0.07 μm) was used as the base film. Note that (a) in FIG. 6 is a sheet surface image of the PET side of Comparative Example 1, and (a) in FIG. 7 is a sheet surface image of the air side of Comparative Example 1.

[0072] <Comparative Example 2> One hundred ceramic sheets were produced in the same manner as in Example 1, except that a commercially available PET film coated with a filler-containing resin (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.39 μm) was used as the base film. Note that (a) in FIG. 8 is a sheet surface image of the PET side of Comparative Example 2.

[0073] Comparative Example 3 One hundred ceramic sheets were produced in the same manner as in Example 2, except that a commercially available PET film coated with a filler-containing resin (film thickness: 100 μm, arithmetic mean roughness (Ra): 0.89 μm) was used as the base film.

[0074] Comparative Example 4 A long green sheet was obtained in the same manner as in Example 1. This long green sheet was punched out with a Thomson blade having a side length of approximately 180 mm, and peeled off from the PET film to obtain a substantially square green sheet.

[0075] (Paste Preparation and Printing) 8.2 g of ethyl cellulose (approximately 49% ethoxy) 10 (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 73.8 g of α-terpineol (manufactured by Kanto Chemical Co., Ltd.) to prepare a binder solution for the paste. 40 g of Eposter MA1002 organic particles (manufactured by Nippon Shokubai Co., Ltd., average particle size: 2 μm) was added to 82 g of the resulting binder solution and mixed with a spatula to obtain an organic particle paste. Next, using a screen printer (manufactured by Newlong Precision Industry Co., Ltd.: LS-150 model) and a printing plate (screen mesh: Tetron, #500) with a roughly square pattern with sides of approximately 155 mm, the organic particle paste was printed on the PET side of a green sheet. The organic particle paste was then air-dried to form a green sheet with a printed layer. Next, using a Thomson blade, a roughly square green sheet with a printed layer with sides of approximately 150 mm was cut out. By the same procedure, 100 green sheets with a printed layer and a roughly square shape with each side being about 150 mm were obtained.

[0076] (Degreasing and Firing) Commercially available food-grade cornstarch was sprinkled onto each of the ten green sheets with approximately square printed layers (on the PET side), and the cornstarch was spread almost uniformly with a brush. Next, ten green sheets with the cornstarch sprinkled on them and the PET side facing up were stacked in a row. Each green sheet was placed on two stacked alumina porous sheets (one side: approximately 200 mm, porosity: approximately 20%, thickness: 0.2 mm). Next, one alumina porous sheet (one side: approximately 160 mm, porosity: approximately 20%, thickness: 0.2 mm) was placed on top of the ten stacked green sheets to form a laminate. Ten sets of laminates were prepared.

[0077] Next, the temperature was raised from room temperature to 400°C over 30 hours in a batch-type hot air circulation electric furnace, and each green sheet in the laminate was degreased. Next, 10 sets of laminates containing the degreased bodies were transferred to a batch-type firing furnace, where the temperature was raised from room temperature to 400°C over 3 hours, and then from 400°C to 1390°C over 24 hours. The laminates were then held at 1350°C for 3 hours and cooled to 900°C over 6 hours. The sheets were then allowed to cool to room temperature in the firing furnace, producing 100 ceramic sheets with sides of approximately 115 mm and a thickness of 90 μm. (a) in Figure 9 is an image of the sheet surface of the PET side of Comparative Example 4.

[0078] Comparative Example 5: A long green sheet was obtained in the same manner as in Example 1. This long green sheet was punched out using a Thomson blade with sides of approximately 160 mm and peeled off from the PET film to obtain a substantially square green sheet. Next, the green sheet was placed on a heating table. At this time, the air side of the green sheet faced the heating table. Next, a stamper was placed on the PET side of the green sheet. This formed a laminate in which the heating table, green sheet, and stamper were stacked in this order. Here, the pressing portion and substrate portion of the stamper were made of resin, and the shape of the protrusions included in the pressing portion was hemispherical. The height of the protrusions was set to 25 μm, the diameter of the protrusions was set to 50 μm, and the distance between the apexes of two adjacent protrusions was set to 100 μm. The pressing portion was also coated with a fluororesin.

[0079] Next, the laminate was placed in the press section of a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd., model "S-37.5"), and the pressing temperature was 25°C and the pressing force was 22.5 MPa (230 kgf / cm ２ ), and a pressing time of 2 seconds. After the pressing, the stamper was peeled off from the green sheet to obtain a green sheet with numerous depressions. 100 roughly square green sheets with sides of approximately 160 mm were obtained by the same procedure.

[0080] Two 200 mm square alumina porous sheets (porosity: 20%, thickness: 0.2 mm) were stacked on a firing shelf. Next, the above green sheet was placed on the two stacked alumina porous sheets. At this time, the green sheet was placed on the alumina porous sheet so that the air side faced the alumina porous sheet. Thereafter, the above green sheets and the above alumina porous sheets were stacked alternately, using the alumina porous sheets of the above dimensions as spacer sheets. Finally, another alumina porous sheet of the above dimensions was placed on the topmost alumina porous sheet to form a laminate. Then, 20 sets of similar laminates were prepared. Here, the number of green sheets included in each laminate was 5.

[0081] Next, the temperature was raised from room temperature to 400°C over 30 hours in a batch-type hot air circulation electric furnace, and each green sheet in the laminate was degreased. Next, 10 sets of laminates containing the degreased bodies were transferred to a batch-type firing furnace, where the temperature was raised from room temperature to 400°C over 3 hours, and then from 400°C to 1430°C over 24 hours. The laminates were then held at 1410°C for 3 hours and cooled to 900°C over 6 hours. The sheets were then allowed to cool to room temperature in the firing furnace, producing 100 ceramic sheets with sides of approximately 120 mm and a thickness of 90 μm. (a) in Figure 10 is an image of the sheet surface of the PET side of Comparative Example 5.

[0082] Comparative Example 6 A long green sheet was obtained in the same manner as in Example 1. This long green sheet was punched out using a Thomson blade with a side length of approximately 160 mm and peeled off from the PET film to obtain a roughly square green sheet. Next, the obtained green sheet was sandwiched between two sheets of roughened paper for surface roughening (arithmetic mean roughness (Ra): 3.1 μm, thickness: 0.335 mm) and subjected to a pressure treatment using a compression molding machine (manufactured by Shinto Metal Industries Co., Ltd., model "S-37.5"). The pressure treatment conditions were a pressure temperature of 25°C, a press pressure of 273 kN, and a pressure holding time of 15 seconds. The green sheet was rotated 90° each time the pressure treatment was performed, for a total of four pressure treatments. After the pressure treatment, the two sheets of roughened paper were peeled off from the green sheet to form a roughened green sheet. Then, 100 roughened green sheets were obtained using the same method.

[0083] Two 200 mm square alumina porous sheets (porosity: 20%, thickness: 0.2 mm) were stacked on a firing shelf. Subsequently, the roughened green sheet was placed on top of the two stacked alumina porous sheets. At this time, the roughened green sheet was placed on top of the alumina porous sheet so that the air side faced the alumina porous sheet. Thereafter, the above green sheets and the above alumina porous sheets were stacked alternately, using the alumina porous sheets of the above dimensions as spacer sheets. Finally, another alumina porous sheet of the above dimensions was placed on top of the topmost alumina porous sheet to form a laminate. Then, 20 similar laminates were prepared. Here, each laminate contained five green sheets.

[0084] Next, the temperature was raised from room temperature to 400°C over 30 hours in a batch-type hot air circulation electric furnace, and each green sheet in the laminate was degreased. Next, 10 sets of laminates containing the degreased bodies were transferred to a batch-type firing furnace, where the temperature was raised from room temperature to 400°C over 3 hours, and then from 400°C to 1430°C over 24 hours. The laminates were then held at 1410°C for 3 hours and cooled to 900°C over 6 hours. The sheets were then allowed to cool to room temperature in the firing furnace, producing 100 ceramic sheets with sides of approximately 120 mm and a thickness of 90 μm. (a) in Figure 11 is an image of the sheet surface of the PET side of Comparative Example 6.

[0085] (Surface Roughness) The arithmetic mean roughness (Ra) of each of the ceramic sheets of Examples 1 to 4 and Comparative Examples 1 to 6 was measured using a stylus surface roughness meter ("Surftest SJ-201" manufactured by Mitutoyo Corporation, standard: JIS B0601:2001). The surface roughness of each of Examples 1 to 4 and Comparative Examples 1 to 6 is shown in Table 1 below.

[0086] (Surface Shape and Height Difference) First, 10 ceramic sheets were randomly selected from the 100 ceramic sheets produced in each of Examples 1 to 4 and Comparative Examples 1 to 6. Next, a laser microscope (Lasertec Corporation, OPTELICS (registered trademark) HYBRID+) was used to extract a random section from the surface of each ceramic sheet, and the surface shape profile of that section was analyzed. Specifically, a 150 μm long surface shape profile was measured in a random section of a sheet surface image captured with a 100x objective lens. The highest and lowest points were determined from the surface shape profile, and the difference between the highest and lowest points was defined as the height difference. This resulted in the calculation of the height difference for a total of 10 sections (150 μm per section) obtained from the random 10 sheets in each of Examples 1 to 4 and Comparative Examples 1 to 6. The average value, standard deviation, and coefficient of variation of the height difference were then calculated. The average value and coefficient of variation of the height difference for each of Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 1 below.

[0087] FIG. 4(b) shows the measurement results of the surface shape profile of the PET surface of Example 1, FIG. 5(b) shows the measurement results of the surface shape profile of the PET surface of Example 2, FIG. 6(b) shows the measurement results of the surface shape profile of the PET surface of Comparative Example 1, FIG. 7(b) shows the measurement results of the surface shape profile of the air surface of Comparative Example 1, FIG. 8(b) shows the measurement results of the surface shape profile of the PET surface of Comparative Example 2, FIG. 9(b) shows the measurement results of the surface shape profile of the PET surface of Comparative Example 4, FIG. 10(b) shows the measurement results of the surface shape profile of the PET surface of Comparative Example 5, and FIG. 11(b) shows the measurement results of the surface shape profile of the PET surface of Comparative Example 6. In each of FIGS. 4(b) to 11(b), the horizontal axis indicates the measurement distance, and the vertical axis indicates the height. In each of FIGS. 4(b) to 11(b), the surface shape profiles of any five sections are shown. To improve readability, the initial height of each surface shape profile is shifted in each of FIGS. 4(b) to 11(b).

[0088] (Surface Shape Slope) The surface shape slope was calculated from the surface shape profile. Specifically, the surface shape profile was composed of points acquired at 0.146 μm intervals, and the slope of an approximated line drawn between 10 adjacent points (length: 1.314 μm) was calculated. This calculation of the slope of the approximated line was repeated until the slope of the approximated line formed by plotting 10 points including the end point of the arbitrary section was calculated. The calculation of the slope of the approximated line described above was performed for each of the arbitrary 10 ceramic sheets. Then, the cumulative relative frequency was calculated by calculating the frequency for each class for the obtained slope data for all 10 sections. The cumulative relative frequencies of the slopes of the approximated lines for Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 2 below.

[0089] (Three-Point Bending Strength) Three-point bending strength measurements were performed on each of the ceramic sheets of Examples 1 to 6 and Comparative Examples 1 to 4 using a method conforming to JIS R 1601:2008. For the three-point bending strength measurement of Example 1, 20 test pieces (length: 60 mm, width: 4 mm, thickness: 100 μm) fabricated using the method described in Example 1 were prepared. Then, the PET side of all test pieces was faced downward, and the three-point bending strength was measured at room temperature. The average value of the three-point bending strength measurement results for the 20 test pieces was taken as the three-point bending strength of the ceramic sheet of Example 1. Furthermore, the Weibull coefficient was calculated from the measured three-point bending strength. For each of Examples 2 to 4 and Comparative Examples 1 to 6, the three-point bending strength was measured and the Weibull coefficient was calculated using the same method as in Example 1. The three-point bending strengths and Weibull coefficients for Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 3 below.

[0090] (Frequency of Double-Piece Pickup) One hundred ceramic sheets were stacked in each of Examples 1 to 6 and Comparative Examples 1 to 4. The ceramic sheets were stacked with the air side facing upward. This resulted in a stack consisting of 100 overlapping ceramic sheets. Next, using four suction pads as a suction conveyor, a sheet conveyance test was conducted as described in (1) to (4) below. The four suction pads were positioned at the vertices of a 5-cm square. (1) The air side of the top ceramic sheet in the stack was vacuum-sucked by the four suction pads, and the ceramic sheet was lifted vertically 10 cm. (2) After (1), the ceramic sheet was moved horizontally 50 cm. (3) After (2), the ceramic sheet was lowered, the suction was released, and the sheet was allowed to rest. (4) Steps (1) to (3) were repeated 100 times.

[0091] In the above (1), there are cases where the top sheet is lifted together with the sheet below it (double-sheet taking). The number of times double-sheet taking occurred was counted by visual observation to determine the double-sheet taking frequency. The double-sheet taking frequency in each of Examples 1 to 4 and Comparative Examples 1 to 6 is shown in Table 3 below.

[0092] (Grain Size) Photographs of the PET surface and side surface of each ceramic sheet produced in Examples 1 to 4 and Comparative Examples 1 to 6 were taken at 3000x magnification using a scanning electron microscope. Next, each photograph was analyzed using image analysis software to calculate the area of ​​each grain in the photograph. Next, assuming that the shape of the grain was circular, the diameter calculated from the average area using the formula for the area of ​​a circle was used as the grain size. From the above, the ratio of the grain size on the PET surface to the grain size on the side surface was calculated for each of Examples 1 to 6 and Comparative Examples 1 to 4. The ratios of the grain size on the PET surface to the grain size on the side surface for each of Examples 1 to 4 and Comparative Examples 1 to 6 are shown in Table 3 below.

[0093] (Kurtosis) The kurtosis of the PET surface of any five of the ceramic sheets produced in each of Examples 1 and 2 and Comparative Examples 1 to 6 was measured using a laser microscope (OPTELICS (registered trademark) HYBRID+, manufactured by Lasertec Corporation). The kurtosis of the air surface of any five of the ceramic sheets produced in Comparative Example 1 was also measured using the same method. The kurtosis of the five sheets measured in each of Examples 1 and 2 and Comparative Examples 1 to 6, as well as the average value, standard deviation, and coefficient of variation of the kurtosis of the five sheets, are shown in Table 4 below.

[0094]

[0095]

[0096]

[0097]

[0098] 1...ceramic sheet, 1a...first main surface, 1b...second main surface, 1c...side surface.

Claims

1. A ceramic sheet having a first main surface and a second main surface, wherein the arithmetic mean roughness of each of the first main surface and the second main surface is 0.01 μm or more and 1.0 μm or less, and when each of the first main surface and the second main surface is measured with a laser microscope, on at least one of the first main surface and the second main surface, the average value of the difference between the highest point and the lowest point in any 10 sections (150 μm per section) is 1.0 μm or more and 4.0 μm or less, the coefficient of variation of the difference between the highest point and the lowest point in the any 10 sections is 0.05 or more and 0.3 or less, the cumulative relative frequency of the slope of the approximated line calculated every 1.314 μm being -0.1 or more and 0.1 or less is 20% or more and 70% or less, and the cumulative relative frequency of the slope of the approximated line being -0.3 or more and 0.3 or less is 85% or more and 100% or less, A ceramic sheet, wherein the cumulative relative frequency of the slope of the approximation line being equal to or greater than −1.5 and equal to or less than 1.5 is 99.9% or more.

2. The ceramic sheet according to claim 1, wherein the cumulative relative frequency of the slope of the approximation line between -1.0 and 1.0 is 99.0% or more and 100% or less.

3. The ceramic sheet according to claim 2, wherein the cumulative relative frequency of the approximate straight line having a gradient of -0.5 or more and 0.5 or less is 99.0% or more and 100% or less.

4. A ceramic sheet according to any one of claims 1 to 3, wherein, on both the first main surface and the second main surface, the cumulative relative frequency at which the slope of the approximate straight line is -0.3 or more and 0.3 or less is 85% or more and 100% or less, and the cumulative relative frequency at which the slope of the approximate straight line is -1.5 or more and 1.5 or less is 99.9% or more and 100% or less.

5. A ceramic sheet according to any one of claims 1 to 3, further having a side surface connecting the first main surface and the second main surface, and the grain size of at least one of the first main surface and the second main surface is 90% or more and 130% or less of the grain size of the side surface.

6. The thickness is 30 μm or more and 200 μm or less, and the area of ​​each of the first main surface and the second main surface is 100 cm ２ More than 400cm ２ Below, the weight is 0.015 g / cm ２ 0.15g / cm or more ２ The ceramic sheet according to any one of claims 1 to 3, wherein:

7. A ceramic sheet according to any one of claims 1 to 3, wherein the average value of kurtosis (Rku) of at least one of the first main surface and the second main surface is less than 3.

8. The ceramic sheet according to any one of claims 1 to 3, which is a zirconia sheet containing at least one rare earth element selected from the group consisting of scandium, yttrium, and cerium in a total amount calculated on oxides of 3 mol % to 15 mol %.

9. The ceramic sheet according to any one of claims 1 to 3, which is an electrolyte sheet for a solid oxide fuel cell.

10. A method for producing a ceramic sheet according to any one of claims 1 to 3, comprising: a first step of preparing a slurry by mixing ceramic powder, a binder, and a solvent; a second step of forming a green sheet by applying the slurry to the surface of a substrate film to be coated; a third step of degreasing the green sheet to form a degreased body of the green sheet; and a fourth step of firing the degreased body to form the ceramic sheet, wherein in the third step, the green sheet is heat-treated at a heat treatment temperature of 100°C or higher and 450°C or lower, and in the fourth step, the degreased body is fired at a firing temperature of 1200°C or higher and 1600°C or lower.

11. The method for manufacturing a ceramic sheet according to claim 10, wherein the surface to be coated is surface-treated with an alkaline chemical solution, the heat treatment temperature is 370°C or higher and 450°C or lower, and the firing temperature is 1350°C or higher and 1450°C or lower.

12. The method for producing a ceramic sheet according to claim 10, wherein the arithmetic mean roughness of the surface to be coated is 0.2 μm or more and 0.7 μm or less.

13. The method for producing a ceramic sheet according to claim 11, wherein the arithmetic mean roughness of the surface to be coated is 0.3 μm or more and 0.6 μm or less.

14. The method for producing a ceramic sheet according to claim 10, wherein the ceramic powder is a zirconia-based powder.

15. A method for producing a ceramic sheet as described in claim 10, wherein the second step is a step of forming a green sheet by applying the slurry in sheet form onto the surface to be coated of a base film by a doctor blade method.

Images