JP2014191944A - Thin-film electrolytic sheet for solid oxide fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin-film electrolytic sheet for a solid oxide fuel battery which enables the reduction in occurrence of fracture or crack when a thin-film electrolytic sheet is exposed to oxidative and reducing atmospheres repeatedly or exposed to an oxidative atmosphere abruptly as an electrolyte-support type cell, and which is uniform in thickness in a range of 50-180 μm, and has at least one hole in a sheet plane, and whose crystal structure is mainly of a cubic zirconia, and to provide a cell for a solid oxide fuel battery including such an electrolytic sheet.SOLUTION: An electrolytic sheet for a solid oxide fuel battery has at least one hole in a sheet plane. The electrolytic sheet is uniform in thickness in a range of 50-180 μm. The crystal structure of the sheet is mainly of a cubic zirconia. At least a part of a peripheral portion of the sheet is mainly of a tetragonal zirconia.

Description

  The present invention relates to a thin film electrolyte sheet for a solid oxide fuel cell, in particular, at least one in the plane of the sheet having a uniform thickness in a range of 50 μm or more and 180 μm or less suitable as a solid electrolyte membrane of an electrolyte supporting cell. The present invention relates to a thin film electrolyte sheet having the above holes and whose crystal structure is mainly cubic zirconia.

  Conventionally, zirconia stabilized with yttria, which is an oxygen ion conductor, has been widely used as a solid electrolyte of a solid oxide fuel cell (hereinafter also referred to as SOFC). In particular, an electrolyte-supporting cell (hereinafter sometimes referred to as ESC) is based on a three-layer structure in which a fuel electrode is formed on one surface of an electrolyte membrane and an air electrode is formed on the other surface. Since the strength for holding the cell itself is required, a tetragonal zirconia sheet having excellent strength characteristics is preferable as the electrolyte membrane. However, since tetragonal zirconia has lower oxygen ion conductivity than cubic zirconia, cell power generation performance tends to be inferior.

  On the other hand, since cubic zirconia has inferior strength characteristics to tetragonal zirconia, cell strength is maintained by making cubic zirconia thick. However, when the electrolyte is thick, there is a problem that the resistance in the electrolyte increases and the cell power generation performance decreases. Therefore, a thin-film cubic zirconia sheet having excellent strength characteristics is required as an electrolyte for ESC.

  In addition, the SOFC system is repeatedly activated and deactivated, and an oxidizing gas may flow into the fuel electrode due to an emergency shutdown, etc., which may lead to a decrease in the power generation performance or damage to the ESC. .

  Since Ni zirconia cermet is widely used as a fuel electrode material, normally, reducing gas such as hydrogen, hydrocarbons and ammonia is always supplied to the fuel electrode side during power generation. Exists in the state of metallic Ni. However, it is considered that when the fuel electrode side is exposed to an oxidizing gas atmosphere, stress is applied to the electrolyte sheet due to volume expansion accompanying Ni in the cermet being oxidized to NiO. This problem of breakage is a major problem in cubic zirconia sheets having poor strength characteristics.

  However, with regard to increasing the strength of the cubic zirconia sheet, there is a study of a method for producing a scandia-stabilized zirconia sheet (Patent Document 1) that reduces the residual pores in the sheet and densifies it to increase the mechanical strength of the electrolyte sheet. However, there has been almost no study on thinning a cubic zirconia sheet with a thickness of 200 μm or less.

  In place of the ESC, a fuel electrode support type cell (hereinafter also referred to as ASC) in which the electrolyte membrane is made an ultra-thin film of, for example, 30 μm or less and the cell strength is maintained by the fuel electrode support substrate has been developed. Since the constituent material of this fuel electrode support substrate is almost the same as that of the above fuel electrode material, it may be alternately exposed to an oxidizing atmosphere and a reducing atmosphere in the same manner as described above, such as oxidation / reduction of a composition such as Ni. A fuel electrode support substrate (Patent Document 2) that suppresses the occurrence of cracks and cracks as much as possible has been disclosed, but a thin-film electrolyte sheet for ESC has hardly been studied.

JP 2011-204398 A JP 2005-327512 A

  In general, the bending strength of a cubic zirconia sheet is mostly in the range of 0.3 to 0.4 GPa regardless of the thickness of the sheet when measured according to JIS standard (JIS R1601). The maximum load value when the sheet breaks greatly varies depending on the thickness of the sheet, and is inversely proportional to the square of the thickness of the sheet.

Therefore, in a thin-film cubic zirconia sheet having a thickness of 50 μm or more and 180 μm or less, cracking or chipping occurs only when a small external force is applied to the sheet in the ESC, for example, stress due to volume expansion due to Ni oxidation of the fuel electrode. Therefore, there is a big problem related to a decrease in the power generation performance of the ESC and the life of the ESC. In particular, in ESC using a thin-film cubic zirconia sheet with a sheet area of 50 cm ² or more and a hole in the sheet surface, it is difficult to break even when exposed to an oxidizing / reducing atmosphere or an oxidizing atmosphere. It must be operated and maintained (for example, when non-oxidizing gas is introduced at the time of operation stop or emergency shutdown), and the operability and cost performance of the SOFC system are reduced.

  The present invention has been made in view of the above circumstances, and is a thin-film cubic zirconia sheet having a denseness (relative density of 99% or more) and a thickness of 50 μm or more and 180 μm or less, which is repeatedly oxidized and reduced as ESC, An object of the present invention is to provide a thin film electrolyte sheet for a solid oxide fuel cell in which cracks and occurrence of cracks are reduced even if the sheet is rapidly exposed to an oxidizing atmosphere. It is another object of the present invention to provide a solid oxide fuel cell including such an electrolyte sheet.

  The inventor of the present invention is an ESC in which a thin film cubic zirconia sheet having a hole in a sheet plane is used as an electrolyte membrane, a fuel electrode is formed on one surface of the electrolyte, and an air electrode is formed on the other surface, and one of the electrolytes The electrolyte-supported half-cell (hereinafter sometimes referred to as ESHC) obtained without forming the fuel electrode on the other side and the air electrode on the other side is rapidly exposed to repeated exposure to an oxidizing / reducing atmosphere. The occurrence of cracks and cracks in the zirconia sheet when exposed to an oxidizing atmosphere was observed.

  As a result, cracks and cracks in the thin film cubic zirconia sheet tend to occur at the peripheral edge of the sheet, in particular, it tends to occur near the peripheral edge of the hole in the sheet surface, The present invention was completed by finding that cracking and crack generation were suppressed by forming at least one part of the peripheral portion into a frame mainly of tetragonal zirconia having excellent strength characteristics.

  The solid oxide fuel cell of the present invention that has solved the above problems, has a uniform thickness in the range of 50 μm to 180 μm, and has at least one hole in the plane of the sheet, The electrolyte sheet whose crystal structure is mainly cubic zirconia is a thin film electrolyte sheet for a solid oxide fuel cell, characterized in that at least a part of the peripheral edge of the sheet is mainly tetragonal zirconia.

  The region that is mainly tetragonal zirconia of the sheet is a region that is at most 10 mm inward from the peripheral edge and the peripheral edge in at least one sheet plane, and the region that is mainly tetragonal zirconia of the sheet, In at least one cross section in the thickness direction, an area in the range of 50% to 100% of the uniform thickness further suppresses the generation of cracks and cracks and improves the reliability of the ESC cell.

  Further, the positions of all the holes in the sheet plane are at least 4 mm from the periphery of the sheet, and the total area of all the holes in the sheet plane is equal to all the holes in the sheet. It is preferable that it is 10% or less of the plane area to be included, since the generation of cracks and cracks from the hole peripheral portion is further suppressed.

  The cubic zirconia is made of stabilized zirconia containing 7 to 15 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium and ytterbium as a stabilizer, The tetragonal zirconia is preferably composed of stabilized zirconia containing 3 to 6 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium and ytterbium as a stabilizer.

  The solid oxide fuel cell including the thin-film cubic zirconia sheet of the present invention and the solid oxide fuel cell including the cell greatly improve the reliability as the SOFC and also have a cost performance. Improved.

  According to the present invention, an electrolyte sheet having at least one or more holes in the sheet surface is cracked or cracked even under conditions where the electrolyte-supported cell is repeatedly exposed to an oxidizing / reducing atmosphere or rapidly exposed to an oxidizing atmosphere. It is possible to provide a thin film cubic zirconia sheet capable of suppressing the generation. Furthermore, the electrolyte support type cell excellent in the reliability using the said sheet | seat can be provided.

Schematic diagram of electrolyte sheet with holes Schematic diagram of electrolyte-supported cell with holes Schematic diagram of electrolyte-supported half cell with holes Schematic diagram and cross-sectional view of an electrolyte sheet (corresponding to As) according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Bs) according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Cs) according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Ds) according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Es) according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Fs) according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet (corresponding to Gs) according to an embodiment of the present invention Schematic diagram and sectional view of an electrolyte sheet (corresponding to Hs) according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic diagram and cross-sectional view of an electrolyte sheet according to an embodiment of the present invention Schematic of an electrolyte-supported half-cell evaluation test apparatus using the electrolyte sheet of the present invention

A: Electrolyte sheet B: Hole C: Electrolyte support type (half) cell D: Fuel electrode E: Air electrode F: Mainly cubic zirconia G: Mainly tetragonal zirconia H: Upper manifold I: Lower manifold J: Gas Introduction pipe K: Gas discharge pipe

  The thin film electrolyte sheet for a solid oxide fuel cell of the present invention has at least one or more holes in the plane of the sheet, and the sheet thickness is a uniform thickness in the range of 50 μm to 180 μm, The crystal structure of the sheet is mainly cubic zirconia, and at least a part of the peripheral portion of the sheet is mainly tetragonal zirconia. Hereinafter, the thin film electrolyte sheet will be described in detail.

  The outline of typical embodiment of the electrolyte sheet (FIG. 1) of this invention is shown to FIGS. The electrolyte sheet is mainly composed of cubic zirconia (F), but at least a part of the peripheral portion of the sheet is mainly tetragonal zirconia (G) having a frame shape. The peripheral edge of the electrolyte sheet of the present invention is an inner peripheral edge around a hole in the sheet surface and an outer peripheral edge on the outer side of the sheet, and the peripheral edge has a sheet plane direction and a sheet thickness direction, respectively. There is no surface.

As a specific sheet form,
1) An electrolyte sheet (FIGS. 4, 5, and 6) in which all inner peripheral edge portions and all outer peripheral edge portions are mainly tetragonal zirconia in a ring shape,
2) An electrolyte sheet in which all inner peripheral edge portions and all outer peripheral edge portions in one planar direction are mainly tetragonal zirconia (FIG. 7).
3) Electrolyte sheet in which all inner peripheral edge portions and all outer peripheral edge portions in both plane directions are mainly tetragonal zirconia (FIG. 8).
4) Electrolyte sheet in which all inner peripheral edge portions and some outer peripheral edge portions in the planar direction are mainly tetragonal zirconia (FIG. 9).
5) Electrolyte sheet in which all the inner peripheral edge is mainly tetragonal zirconia (FIG. 10).
6) Electrolyte sheet in which only all inner peripheral edges in both planar directions are mainly tetragonal zirconia (FIG. 11).
7) Electrolyte sheet in which all inner peripheral edge portions in one plane direction and all outer peripheral edge portions are mainly tetragonal zirconia (FIG. 12).
8) An electrolyte sheet in which all inner peripheral edge portions in one plane direction and all outer peripheral edge portions in one plane direction are mainly tetragonal zirconia (FIGS. 13 and 14).
9) Electrolyte sheet in which all inner peripheral edge portions in one planar direction and some outer peripheral edge portions in the planar direction are mainly tetragonal zirconia (FIG. 15)
10) Electrolyte sheet in which all inner peripheral edge portions in both planar directions and all outer peripheral edge portions are mainly tetragonal zirconia (FIG. 16)
11) Electrolyte sheet in which all inner peripheral edges in both plane directions and all outer peripheral edges in both plane directions are mainly tetragonal zirconia (FIG. 17).
12) Electrolyte sheet in which all inner peripheral edges in both planar directions and some outer peripheral edges in the planar direction are mainly tetragonal zirconia (FIG. 18).
13) Electrolyte sheet in which all outer peripheral edges are mainly tetragonal zirconia (FIG. 19)
Etc.

  Among these, in both the planar direction and the thickness direction of the inner peripheral edge of the hole in the sheet plane, only the inner peripheral edge or only a part of the inner peripheral edge is tetragonal zirconia. It is preferable because the generation of cracking cracks can be suppressed, and it is more preferable that all of the inner peripheral edge portion is tetragonal zirconia.

  Further, all of the inner peripheral edge and the outer peripheral edge, or part of the inner peripheral edge and one of the outer peripheral edges in both the planar direction and the thickness direction of the inner peripheral edge and the outer peripheral edge of the hole in the sheet plane. A form in which only the portion is tetragonal zirconia is further preferable, and a form in FIG. 4 in which all inner peripheral edges and all outer peripheral edges are mainly tetragonal zirconia in a ring shape is particularly preferable.

  In the case of a sheet having a plurality of holes in a plane, the electrolyte sheet of the above-described form in which the peripheral part of at least one hole is mainly tetragonal zirconia may be used. In order to suppress the occurrence of cracks from the peripheral edge when repeatedly exposed to the atmosphere, it is preferable that all of the plurality of holes have the above-described form.

  The peripheral edge of the sheet includes the peripheral edge in the sheet plane direction of the outer peripheral edge and the inner peripheral edge, the area surface in the range 10 mm inside from the peripheral edge, and the entire area surface in the sheet thickness direction of the outer peripheral edge and the inner peripheral edge. It refers to the combined area surface, that is, the surface portion of the sheet periphery (edge).

  The gist of the present invention is that at least a part of the peripheral portion is mainly made of tetragonal zirconia. That is, tetragonal zirconia is the entire region in the range 10 mm inside from the peripheral edge and the peripheral edge in the planar direction, or a partial region in the inner range at most less than 10 mm from the peripheral edge and the peripheral edge. Also good. Further, even in the entire region of the cross section in the thickness direction of the outer peripheral edge and the inner peripheral edge of the sheet, 50% to 100% of the thickness in the cross section in the thickness direction of the outer peripheral edge and the inner peripheral edge. The range may be less than%.

  When the area mainly composed of tetragonal zirconia exceeds 10 mm from the peripheral edge, the plane area of cubic zirconia is reduced, so that the handling strength of the thin film electrolyte sheet is improved. The power generation performance tends to decrease. More preferably, the peripheral edge and the area in the range of at least 8 mm inside from the peripheral edge, more preferably the area in the range of at least 6 mm inward from the peripheral edge and the peripheral edge, particularly preferably at least 5 mm inward from the peripheral edge and the peripheral edge. It is the area of the range.

  In addition, the region mainly composed of tetragonal zirconia in the sheet is a region in the range of 50% to 100% of the uniform sheet thickness in at least one cross section in the thickness direction. When the thickness is less than 50% of the uniform thickness, the area of cubic zirconia in the peripheral thickness direction increases, and cracking from the peripheral edge tends to increase when repeatedly exposed to an oxidizing / reducing atmosphere. Become. More preferably 60% or more of the sheet thickness, further preferably 80% or more of the sheet thickness, particularly preferably 100% of the sheet thickness, that is, the cross-sectional area in the thickness direction is all tetragonal zirconia. .

When the ESC cell is stacked, the hole in the plane of the seat is an introduction path for a reducing gas such as hydrogen or hydrocarbon, or an oxidizing gas such as air, or a combustion exhaust gas, an unburned gas or an unburned gas. It forms a discharge path for the oxidizing gas used, and in many cases, at least one or more holes whose positions and areas are defined from the design of the SOFC stack system, and in many cases one to four Two holes are designed in the electrolyte sheet surface. The shape of the holes is circular, oval, rectangular, it may be any polygon with R and the like, one hole in the area range of 0.5cm ² ~10cm ^2, preferably in the range of ^{1 cm} 2 to 5 cm ² is there.

  In the electrolyte sheet of the present invention, the positions of all the holes in the sheet plane are at least 4 mm from the periphery of the sheet, that is, the shortest distance between the outer periphery of the sheet and the inner periphery of the hole is 4 mm or more. If it is less than 4 mm, cracks and cracks are likely to occur during the manufacturing process of the electrolyte sheet. In order to prevent cracking and cracking of the electrolyte sheet during the production process, the thickness is more preferably 6 mm or more, further preferably 8 mm or more, and particularly preferably 10 mm or more.

  In addition, the electrolyte sheet whose crystal structure of the present invention is mainly cubic zirconia is mainly composed of a peak due to cubic zirconia among the diffraction peak intensities of the electrolyte sheet obtained by the X-ray diffraction method. It is zirconia. Specifically, each peak intensity is obtained from the X-ray diffraction pattern of the zirconia crystal in the zirconia sheet, a cubic ratio (%) is obtained from each intensity value and the following formula, and the cubic ratio is 80% or more. Preferably, it is 90% or more, more preferably 95% or more. The reason why the cubic crystal ratio is set to 80% or more is that if it is less than 80%, the oxygen ion conductivity and bending strength of the obtained zirconia sheet tend to be impaired.

Cubic crystal ratio (%) = (100−monoclinic crystal ratio) × (c (400)) ÷ (t (400) + t (004) + c (400)).
Monoclinic crystal ratio (%) = (m (111) + m (−111)) ÷ (m (111) + m (−111) + tc (111)) × 100 Equation 2
(Where c (400) indicates the peak intensity of the cubic (400) plane, t (400) and t (004) indicate the peak intensity of the tetragonal (400) plane and (004), and m (111 ) And m (-111) indicate the peak intensities of the monoclinic (111) plane and (-111) plane, and tc (111) indicates the peak intensity of the (111) plane of the superimposed tetragonal and cubic crystals. .)
Further, that at least one part of the peripheral edge of the sheet is mainly tetragonal zirconia is zirconia mainly composed of a peak due to tetragonal zirconia in the intensity of the diffraction peak at the peripheral edge of the sheet. Specifically, each peak intensity is obtained from the X-ray diffraction pattern, and a tetragonal crystal ratio (%) is obtained from each intensity value and the following formula, and the tetragonal crystal ratio is preferably 80% or more, preferably 90% or more. More preferably, it is more preferably 95% or more. The reason why the tetragonal ratio is set to 80% or more is that when it is less than 80%, the resulting zirconia sheet tends to effectively suppress cracking and cracking when exposed to an oxidizing / reducing atmosphere. It is.

Tetragonal crystal ratio (%) = (100−monoclinic crystal ratio) × (t (400)) + t (004)) ÷ (t (400) + t (004) + c (400)).
Furthermore, the cubic zirconia sheet of the present invention has a uniform thickness in the range of 50 μm to 180 μm. A more preferable thickness as the thin film sheet is in the range of 60 μm to 150 μm, more preferably in the range of 70 μm to 130 μm, and particularly preferably in the range of 80 μm to 120 μm. The above-mentioned sheet thickness is a total of 15 locations including the thickness of any 5 locations on the periphery of the sheet measured with a micrometer of both spherical surfaces and the thickness of any 10 locations in a single region of cubic zirconia other than the periphery. It means the average value.

  Moreover, uniform thickness means that the measured value of each said place enters into the range within +/- 10% of the said average value. Here, it is specified that it is within ± 10%. Ceramic sheets are formed by sintering ceramic powders, but generally, individual ceramic powders are not monophysical and have shrinkage due to sintering. This is because the thickness of the sheet inevitably causes a flare within ± 10%. More preferably, it is within ± 8%, further preferably within ± 7%, and particularly preferably within ± 6%. If the measured value is more than ± 10% even at one location relative to the average value of the sheet thickness, use of the sheet as an ESC electrolyte sheet will hinder mass production of ESC. . Furthermore, stress is likely to be applied to the peak portions of the unevenness of the electrolyte sheet, resulting in a serious problem that the ESC is likely to be cracked or cracked.

The cubic zirconia is a stabilized zirconia containing 7 to 15 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium and ytterbium as a stabilizer. Among these, in the case of scandia-stabilized zirconia (hereinafter sometimes referred to as “ScSZ”), the content of scandia is 7 to 12 mol%, preferably 8 to 11 mol%, and scandia ceria-stabilized zirconia. (Hereinafter sometimes referred to as “ScCeSZ”), the content of scandia and ceria is 7 to 12 mol% of scandia 0.5 to 3 mol% of ceria, preferably 8 to 11 mol% of scandia, and ceria 1 ~ 2 mol%. In the case of yttria stabilized zirconia (hereinafter sometimes referred to as “YSZ”), the yttria content is 7 to 12 mol%, preferably 8 to 10 mol%. In the case of “YbSZ”), the ytterbia content is 8 to 15 mol%, preferably 9 to 12 mol%. A cubic system in which 0.02 to ₃ mol% of Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , In ₂ O _{3 and the} like are added together with these stabilizers. It may be zirconia.

The tetragonal zirconia is a stabilized zirconia containing 3 to 7 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, and ytterbium as a stabilizer, and among these, ScSZ In this case, the scandia content is 3 to 7 mol%, preferably 4 to 6 mol%. In the case of YSZ, the yttria content is 2 to 6 mol%, preferably 3 to 5 mol%. In the case of YbSZ, the ytterbia content is 3 to 7 mol%, preferably 4 to 6 mol%. is there. In addition, 0.03 to ₃ mol% of Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , In ₂ O ₃ , CeO _{2 and the} like are added together with these stabilizers, or Cubic zirconia to which the above-mentioned cubic zirconia is added up to 20 mol%, preferably up to 10 mol%, may be used.

The shape of the zirconia sheet of the present invention may be any of a circle, an ellipse, a square, a square having R (R), etc., and a similar circle, an ellipse, a square, a square having R, etc. in these sheet planes. It has one or more holes. Further, the size of the sheet is 50 cm ² or more, more preferably 70 cm ² or more, more preferably 90 cm ² or more, particularly as an electrolyte suitable for a SOFC system with a power generation amount of 0.5 kW level or more. Preferably it is 100 cm ² or more. The plane area of the sheet is 900 cm ² or less, more preferably 600 cm ² or less, further preferably 500 cm ² or less, and particularly preferably 400 cm ² or less. In this case, the area of the hole in the sheet plane is also included in the sheet plane area.

  The total area of all the holes in the sheet plane is 10% or less of the plane area including all the holes of the sheet. If it exceeds 10% of the plane area, the electrode effective area of the ESC decreases, and the power generation performance per ESC decreases. The total area of the holes is more preferably 8% or less, further preferably 6% or less, and particularly preferably 5% or less.

  The method for producing the electrolyte sheet of the present invention is not particularly limited, and can be produced by a conventional doctor blade method, a screen printing method, or a combination thereof.

  Below, the manufacturing method of ESC and ESHC using the electrolyte sheet of this invention and the said electrolyte sheet is illustrated according to process. Moreover, the evaluation method of ESHC is also illustrated.

1. Preparation of slurry In this step, a slurry is prepared by mixing cubic zirconia powder or tetragonal zirconia powder, a solvent, a binder, and, if necessary, a plasticizer or a dispersant with a ball mill or a bead mill.

As the zirconia powder, a powder having a BET specific surface area of 5 m ² / g or more and 15 m ² / g or less and a 50 volume% diameter (D ₅₀ ) of 0.25 μm or more and 0.8 μm or less is used.

  The cubic zirconia powder is a zirconia powder mainly composed of cubic crystals among the intensities of diffraction peaks obtained by the powder X-ray diffraction method. Specifically, each peak intensity is obtained from the X-ray diffraction pattern of the zirconia crystal in the zirconia powder, a cubic ratio (%) is obtained from each intensity value and the above formula (1), and the cubic ratio is 80% or more. It is preferably 90% or more, more preferably 95% or more. The reason why the cubic crystal ratio is set to 80% or more is that if it is less than 80%, the oxygen ion conductivity and bending strength of the obtained zirconia sheet tend to be impaired. Similarly, the tetragonal zirconia powder is a zirconia powder mainly composed of tetragonal crystals. Specifically, each peak intensity is obtained from the X-ray diffraction pattern of the zirconia crystal in the zirconia powder, a cubic ratio (%) is obtained from each intensity value and the above formula (3), and the cubic ratio is 70% or more. It is preferably 80% or more, more preferably 90% or more. The reason why the tetragonal ratio is set to 70% or more is that cracking from the periphery of the sheet framed with tetragonal zirconia in an oxidizing / reducing atmosphere repeatedly exposed as ESC of the zirconia sheet obtained when the ratio is less than 70%. This is because the effect of suppressing the occurrence of cracks tends to be reduced.

The cubic zirconia powder having the above crystal structure is 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 as stabilizers. Rare earth metal oxides such as ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ ; alkalis such as MgO, CaO, SrO, BaO An earth metal oxide is used. In particular, a stabilized zirconia powder containing 7 to 15 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium, and ytterbium is preferable.

Among these, in the case of ScSZ powder, the content of scandia is 7 to 12 mol%, preferably 8 to 11 mol%, and in the case of ScCeSZ powder, the content of scandia and ceria is 7 to 12 mol% of scandia. Ceria is 0.5 to 3 mol%, preferably scandia is 8 to 11 mol%, and ceria is 1 to 2 mol%. In the case of YSZ powder, the yttria content is 7 to 12 mol%, preferably 8 to 10 mol%. In the case of YbSZ powder, the ytterbia content is 8 to 15 mol%, preferably 9 to 12 mol%. %. In addition, it is also possible to add 0.03 to ₃ mol% of Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , In ₂ O _{3 and the} like together with these stabilizers. is there.

Further, the tetragonal zirconia powder having the crystal structure is 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 as a stabilizer. , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O _{3 and} other rare earth metal oxides; MgO, CaO, SrO, BaO, etc. In particular, a stabilized zirconia powder containing 3 to 6 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium and ytterbium is preferable.

Among these, in the case of ScSZ powder, the content of scandia is 3 to 6 mol%, preferably 4 to 6 mol%, and in the case of YSZ powder, the yttria content is 3 to 6 mol%, preferably Is 3 to 5 mol%, and in the case of YbSZ powder, the ytterbia content is 3 to 6 mol%, preferably 4 to 6 mol%. In addition, it is also possible to add 0.03 to ₃ mol% of Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , TiO ₂ , Bi ₂ O ₃ , In ₂ O _{3 and the} like together with these stabilizers. is there.

The cubic zirconia powder and tetragonal zirconia powder have a BET specific surface area of 3 m ² / g or more, preferably 4 m ² / g or more, more preferably 5 m ² / g or more. Moreover, it is 15 m < ² > / g or less, Preferably it is 12 m < ² > / g or less, More preferably, 10 m < ² > / g or less is preferable. If the BET specific surface area is within the above range, the necessary amount of binder for green tape molding is reduced, so that the residual pores in the thin zirconia sheet obtained by increasing the powder filling rate in the green sheet can be further reduced. A dense sheet having a relative density of 99% or more, preferably 99.3% or more can be obtained.

The 50 volume% diameter (D ₅₀ ) of the cubic zirconia powder and the tetragonal zirconia powder is 0.25 μm or more and 0.8 μm or less. If D ₅₀ exceeds 0.8 [mu] m, the aggregate of the zirconia powder is increased, the strength of the resulting thin film zirconia sheet is lowered. On the other hand, when D ₅₀ is less than 0.25 μm, the amount of nano-sized fine particles increases in the zirconia powder, so that a large amount of binder is required, and when the integrated green sheet is fired as described above, the sheet is large. Warp and large burrs are likely to occur at the periphery of the sheet. The D ₅₀ is more preferably 0.3 μm or more, further preferably 0.35 μm or more, particularly preferably 0.4 μm or more, more preferably 0.7 μm or less, still more preferably 0.65 μm or less, particularly preferably 0. .6 μm or less.

  In the present invention, the 50 volume% diameter is measured by a laser diffraction / scattering particle size distribution measuring apparatus (trade name “LA-920”, manufactured by Horiba, Ltd.), and the particle volume is integrated from the smaller particle diameter. The particle diameter is 50% by volume with respect to the total particle volume.

Incidentally, the green sheet cubic zirconia powder and tetragonal zirconia powder used in the present invention is commercially available powder is used, the specific surface area and particle size distribution (D ₅₀ and D ₉₀₎ are integrated differs greatly When the material is fired, there is a tendency that the sheet is greatly warped and burrs generated at the periphery of the sheet are large, and the thickness becomes non-uniform. Therefore, in order to adjust the firing shrinkage rate in the X direction, Y direction, and Z direction of the green sheet to produce an electrolyte sheet having a uniform thickness, a commercially available zirconia powder is heat treated at 1000 to 1400 ° C. and then pulverized. Therefore, it is necessary to make the specific surface area and particle size distribution (D ₅₀ and D ₉₀ ) of the cubic zirconia powder and the tetragonal zirconia powder as uniform as possible. Therefore, a product obtained by pulverizing a fired body obtained by heat treatment by calcining or sintering after molding a commercially available zirconia powder can be used alone or mixed with a commercially available zirconia powder.

  To the slurry raw material powder, ceramic powder made of alumina, titania, silica, niobium oxide, thallium oxide or the like may be added in addition to the cubic stabilized zirconia powder to the extent that the effects of the present invention are not impaired. The amount of the ceramic powder used is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 3% by mass or less with respect to the total of the raw material powders.

  The kind in particular of binder used for a slurry is not restrict | limited, A conventionally well-known organic binder can be selected suitably and can be used. Examples of organic binders include ethylene copolymers, styrene copolymers, (meth) acrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, celluloses such as ethyl cellulose, and the like.

  Among these, from the viewpoint of suppressing the moldability, punching processability, strength, and shrinkage ratio variation during firing of the zirconia green sheet, it is thermoplastic and has a number average molecular weight of 20000 to 250,000, more preferably 50000 to 200000 (meta ) Acrylate copolymers are recommended as preferred.

  The amount of the binder used varies depending on the particle size and particle size distribution of the cubic zirconia powder in the raw material and / or slurry, but is preferably 5 parts by mass or more, more preferably 7 parts by mass or more with respect to 100 parts by mass of the raw material powder. More preferably, it is 8 mass parts or more, 16 mass parts or less are preferable, More preferably, it is 15 mass parts or less, More preferably, it is 14 mass parts or less. If the amount of the binder used is insufficient, the moldability of the zirconia green sheet is lowered, and the strength and flexibility may be insufficient. On the other hand, if the amount is too large, not only will it be difficult to adjust the viscosity of the slurry, but there will be a lot of decomposition and release of the binder component during degreasing and sintering, and the linear shrinkage will vary in the X, Y, and Z directions. And the sheet has a non-uniform thickness that differs greatly between the peripheral edge and the center.

  Solvents for slurry include water; 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 Aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and acetates such as methyl acetate, ethyl acetate, and butyl acetate, and the like. These solvents can be used alone or in combination of two or more. The amount of these solvents to be used is preferably adjusted in consideration of the viscosity of the slurry and the solid content concentration at the time of forming the zirconia green sheet.

  The viscosity of the slurry is adjusted to a range of 1 Pa · s to 50 Pa · s, more preferably 2 Pa · s to 20 Pa · s. The solid content concentration is adjusted to a range of 60 to 90% by mass, more preferably 70% by mass or more, further preferably 75% by mass, and particularly preferably 80% by mass or more. By adjusting the viscosity and solid content concentration of the slurry to the above range, the amount of solvent in the green tape is reduced while maintaining the fluidity of the slurry, the powder packing density of the green tape is increased, and the zirconia sheet after firing The thickness can be reduced non-uniformly. In addition, solid content concentration said by this invention is represented by a following formula.

  Solid content concentration (%) = (mass of zirconia powder + mass of binder solid content) ÷ mass of total composition × 100.

  In preparing the slurry, it is preferable to use a dispersant in order to promote dispersion of the zirconia raw material powder. Dispersants include polyelectrolytes such as polyacrylic acid and ammonium polyacrylate; partial esters of α-olefin / maleic anhydride copolymers; organic acids such as citric acid and tartaric acid; isobutylene or styrene and maleic anhydride And a copolymer of butadiene and maleic anhydride and an ammonium salt thereof.

  Moreover, it is preferable to add a plasticizer in order to improve the moldability of the slurry. Examples of plasticizers include phthalates such as dibutyl phthalate and dioctyl phthalate; glycols such as propylene glycol and glycol ethers; polyesters such as phthalic polyester, adipic acid polyester, and sebacic acid polyester. be able to. Furthermore, a surfactant, an antifoaming agent, etc. can be added as needed.

  Moreover, in the manufacturing method of this invention, it is also a preferable aspect to use the collection body green body containing the stabilized zirconia powder as a slurry raw material. Since the cubic stabilized zirconia powder is expensive, it is indispensable to use the recovered green body in the actual manufacturing process in order to reduce the cost of the raw material.

  The amount of the recovered green body used is preferably 5% by mass or more in the total stabilized zirconia powder contained in the slurry in terms of the mass of the stabilized zirconia powder contained in the recovered green body, and more preferably. Is 10% by mass or more, more preferably 15% by mass or more, and preferably 50% by mass or less, more preferably 50% by mass or less, and still more preferably 40% by mass or less.

  The slurry is prepared by mixing appropriate amounts of the above components. At that time, in order to make each particle finer and to make the particle diameter uniform, the particles may be mixed while being pulverized by a ball mill or a bead mill. Moreover, the order of addition of each component is not particularly limited, and may be according to a conventional method.

2. Production of Green Sheet Next, a process for producing a green sheet using the slurry obtained above will be described. In the production method of the present invention, the obtained slurry is continuously coated on a polymer film in a tape shape by a tape casting method, and dried to obtain a green tape.

  Here, the tape casting method is a method in which a slurry containing raw material powder is applied in a sheet form, and examples thereof include a doctor blade method. In the doctor blade method, in general, a raw material slurry is supplied into a slurry tank, pressure is applied to the slurry, and the slurry is transported to a coating dam via a pipe. It coats on a polymer film so that it may become. The material of the polymer film is not particularly limited, and a conventionally known plastic film can be used. The polymer film is required to have not only flexibility but also sufficient rigidity and strength as a support for the green tape. Therefore, it is preferable to use a PET film having a thickness of 50 μm to 180 μm made of polyethylene terephthalate.

  Thereafter, the slurry coated on the carrier film is dried to obtain a tape-shaped molded product, that is, a green tape. Drying conditions are not particularly limited, and for example, drying may be performed at a constant temperature of room temperature to 150 ° C., or heating may be performed by sequentially raising the temperature sequentially such as 50 ° C., 80 ° C., and 120 ° C. The thickness of the green tape after drying is 10 μm or more, more preferably 20 μm or more, more preferably 60 μm or more, 210 μm or less, more preferably 180 μm or less, further preferably 150 μm or less, particularly preferably 130 μm or less. Adjusted.

Next, the obtained green tape is punched and cut into a predetermined shape to obtain a green sheet. The punching / cutting is not particularly limited, and is performed in a known manner using a mold, a laser, a Thomson blade or the like. After cutting, the green sheet may have any shape such as a circle, ellipse, square, square with R (R), donut shape, ring shape, bow shape, etc. It has a green sheet having one or two or more holes such as a circle, an ellipse, a square, and a square having an R shape. The plane area is 1 cm ² or more, more preferably 2 cm ² or more, further preferably 3 cm ² or more, and is adjusted to a range of 1000 cm ² or less, more preferably 700 cm ² or less, and even more preferably 600 cm ² or less. The plane area including the hole of the cubic zirconia green sheet forming the main body of the electrolyte sheet of the present invention is 60 cm ² or more, more preferably 70 cm ² or more, more preferably 100 cm ² or more, more preferably 1000 cm ² or less. Is adjusted to a range of 700 cm ² or less, more preferably 600 cm ² or less.

3. Production of integrated green sheet In order to produce the electrolyte sheet of the present invention, the cubic zirconia green sheet and tetragonal zirconia green sheet of the predetermined shape obtained above are arranged as shown in FIGS. Then, it is processed into an integrated green sheet having a uniform thickness by pressurization, bonding, fusion, or the like. Further, the tetragonal zirconia green sheet can be formed as a tetragonal zirconia green layer by applying a slurry containing tetragonal zirconia powder by screen printing or the like.

  In order to prevent the interface between the cubic zirconia green sheet and the tetragonal zirconia green sheet from peeling off, the integrated green sheet is held at a temperature range of room temperature to 80 ° C, preferably 30 to 60 ° C. However, the pressure is applied in the range of 10 to 150 MPa, preferably 20 to 120 MPa for 1 to 180 seconds, preferably 2 to 120 seconds. At this time, in order to maintain the shape of the integrated green sheet and make the thickness uniform without bubbles or the like entering the interface between the cubic layer and the tetragonal layer, a type made of Teflon, a type coated with Teflon, It is preferable to place and pressurize the integrated green sheet while reducing the pressure on a mold or the like on which a polymer film made of polyethylene terephthalate (PET) or the like having been subjected to a mold release treatment is attached.

4). Firing of the integrated green sheet The integrated green sheet produced as described above is fired to obtain the thin film cubic zirconia sheet of the present invention.

  The method for firing the integrated green sheet is not particularly limited, and a conventionally known method can be employed. For example, integrated green sheets can be placed and fired on a shelf board one by one, but for the purpose of mass production, a stack of alternately stacked integrated green sheets and porous spacer sheets is placed on a shelf. It is preferable to place it on a plate and sinter.

  The structure of the laminate consists of a spacer sheet placed at the bottom, an integrated green sheet and a spacer sheet stacked alternately, and a spacer sheet placed on the top. The lowermost spacer sheet prevents the integrated green sheet and the shelf board from being joined, and the uppermost spacer sheet serves as a weight to reduce sheet warpage and undulation.

  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 integrated green sheet, the treatment is performed at 100 ° C. to 400 ° C., preferably 150 ° C. to 300 ° C. for about 2 hours to 50 hours. Subsequently, the zirconia powder is sintered by holding and firing at 1300 ° C. to 1600 ° C., preferably 1350 ° C. to 1550 ° C. for 2 hours to 10 hours, and the electrolyte sheet of the present invention is obtained.

  Further, the thin film cubic zirconia sheet produced by the method of the present invention has a uniform thickness in the range of 50 μm or more and 180 μm or less, and the relative density (density / theoretical density measured by Archimedes method) is 99% or more. More preferably, it is a dense body of 99.3% or more.

5. Preparation of Electrolyte-Supported Cell and Electrolyte-Supported Half Cell Conventional methods can be used to obtain an SOFC-supported cell for SOFC using the cubic zirconia sheet of the present invention as an electrolyte. That is, a fuel electrode is formed on one surface of the zirconia sheet, an air electrode is formed on the other surface, and, if necessary, in order to prevent a reaction between the electrolyte material and the fuel electrode material or the air electrode material, An intermediate layer is formed on one or both sides. Therefore, in order to increase the bonding strength between the electrolyte sheet and the fuel electrode, air electrode, or intermediate layer and prevent peeling from the electrolyte, it is preferable to provide the surface of the electrolyte sheet with an appropriate surface roughness that imparts an anchor effect.

  As the fuel electrode material, generally, cermets of Ni, Co, Ru, etc., stabilized zirconia, and ceria oxide are preferably used. Particularly preferred is a cermet comprising Ni and 9 to 12 mol% scandia-stabilized zirconia. These fuel electrode materials are kneaded with a binder such as ethyl cellulose and a solvent such as α-terpineol to form a fuel electrode paste, or milled to form a fuel electrode slurry, which is coated and dried by a screen printing method, a coating method, or the like. Then, it bakes at 1200-1400 degreeC, a fuel electrode is formed on one surface of an electrolyte sheet, and an electrolyte support type half cell is produced.

As an air electrode material, a perovskite structure oxide having a basic structure of LaMnO ₃ , LaCoO ₃ or LaFeO ₃ , and a mixture obtained by adding stabilized zirconia and / or ceria oxide to these perovskite structure oxides are used. Can be mentioned. Particularly preferably, a mixture obtained by adding 9 to 12 mol% ScSZ to La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ or LaNi _0.6 Fe _0.4 O ₃ is suitably used. . As in the case of the fuel electrode, an air electrode paste or an air electrode slurry is prepared, and the surface opposite to the fuel electrode of the electrolyte-supporting half cell is coated and dried by a screen printing method, a coating method, etc., and then 900 to 1350 An electrolyte-supported cell is fabricated by firing at 0 ° C. to form an air electrode.

  The order of formation of the fuel electrode and the air electrode is not particularly limited. Further, an intermediate layer made of the above ceria oxide may be formed between the solid electrolyte and the air electrode in order to prevent these solid phase reactions. Furthermore, a fuel electrode contact layer may be formed on the fuel electrode, and an air electrode contact layer may be formed on the air electrode.

6). Evaluation Test of Electrolyte-Supported Half Cell It is preferable that the oxidation / reduction test and the oxidation test of the electrolyte-supported cell (ESC) using the electrolyte sheet of the present invention are carried out in a stack power generator of an actual machine level in which ESCs are stacked. . However, in the present invention, the other surface on which the occurrence of cracks / cracks in the electrolyte sheet can be confirmed more accurately than the ESC in which the fuel electrode is formed on one surface of the electrolyte sheet and the air electrode is formed on the other surface. An electrolyte-supported half cell (ESHC) that remained as a zirconia sheet was substituted. In addition, the oxidation / reduction test and the oxidation test are preferably performed under conditions suitable for the actual machine of the SOFC system, but it is preferable to select conditions that can promote the influence on the electrolyte sheet by more severe conditions by a simple method. Therefore, the ESHC used for evaluation is not a small test piece for evaluation, but has a size of an actual machine level.

  As a specific test method, it is possible to repeatedly expose the fuel electrode to an oxidizing atmosphere and a reducing atmosphere while maintaining the ESHC of the actual machine level at 700 to 900 ° C., and to rapidly expose the fuel electrode to the oxidizing atmosphere of FIG. A method of incorporating a half cell into a manifold as shown in the schematic diagram of the test apparatus, introducing hydrogen or the like into the fuel electrode and exposing it to a reducing atmosphere, and then introducing air or the like and exposing it to an oxidizing atmosphere is exemplified. In this case, it is preferable to exhaust by introducing an inert gas such as nitrogen or reducing the pressure so that hydrogen or the like does not directly mix with air or the like.

  Further, it is not necessary to introduce gas to the side where the air electrode is not formed, and the upper manifold (H) shown in FIG. The above test was conducted for each of five ESHCs, and the state of occurrence of cracks / cracks in the electrolyte sheet after each test was determined by dividing the surface of the electrolyte sheet on which the air electrode was not formed, particularly the peripheral part into an inner peripheral edge and an outer peripheral edge. Those that were observed visually or by a dyeing test and were found to be cracked or cracked even at one location were judged to have an ESHC cracked or cracked.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples, and may be appropriately modified and implemented within a range that can meet the purpose described above and below. All of which are within the scope of the present invention.

(I) Preparation of zirconia green sheet (production of cubic zirconia green sheet)
A commercially available ScCeSZ powder stabilized with 1 mol% scandia 1 mol% ceria (manufactured by Daiichi Elemental Chemicals, trade name “10Sc1CeSZ”, specific surface area: 11 m ² / g, D ₅₀ : 0.6 μm) After heat-treating at a temperature of 1200 ° C. using a rotary kiln made of alumina, a ScCeSZ powder having a specific surface area of 9 m ² / g and D _{50 of} 0.5 μm was prepared.

  A mixture of 60 parts by mass of toluene as a solvent and 1.5 parts by mass of a sorbitan fatty acid ester surfactant as a dispersant was mixed with 100 parts by mass of the ScCeSZ powder as a raw material powder while being pulverized by a ball mill. To the mixture, a methacrylate copolymer (number average molecular weight: 55000, glass transition temperature: −8 ° C., solid content concentration: 50 mass%) as a binder is 14 mass parts as a solid content concentration, and dibutyl phthalate is 2 mass as a plasticizer. Part was added and mixed with a ball mill for 20 hours to form a slurry. By concentrating and defoaming the obtained slurry, the viscosity at 25 ° C. was adjusted to 2 to 13 Pa · s to obtain a coating slurry.

  Each of the coating slurries was coated on a PET film running at a speed of 0.2 m / min by the doctor blade method. The PET film is passed through a dryer having three temperature ranges of 50 ° C., 80 ° C., and 110 ° C., and then cut with a slitter. The width is 150 mm, the length is 60 m, and the thickness is about 40, 80 μm and 120 μm. The long green tape was obtained.

  The obtained green tape is formed into a predetermined shape of cubic zirconia so that an integrated green sheet having an outer diameter of about 120 mm, an inner diameter of about 20 μm, and a thickness of 120 μm can be formed. Cubic zirconia green sheets were prepared by cutting.

(Preparation of tetragonal zirconia green sheet)
Using a commercially available 3 mol% YSZ powder (manufactured by Daiichi rare element chemical industry, trade name “HSY-3”, specific surface area: 9 m ² / g, D ₅₀ : 0.5 μm), the cubic zirconia green sheet In the same manner as in the preparation of the above, slurry preparation and tape molding were performed to obtain long green tapes having a width of 150 mm, a length of 40 m, and a thickness of about 40, 80 μm and 120 μm.

  Further, the green tape obtained in the same manner as the production of the cubic zirconia green sheet is tetragonal so that an integrated green sheet having an outer diameter of about 120 mm, an inner diameter of about 20 μm and a thickness of 120 μm can be formed. A tetragonal zirconia green sheet was produced by cutting the zirconia into a predetermined shape of zirconia into a ring shape or an arc shape using a mold.

(Ii) Production of integrated green sheet (production of integrated green sheet in FIG. 4)
Thickness cut into a ring shape with an outer diameter of about 120 mm and an inner diameter of about 110 μm on the outer peripheral edge of a cubic zirconia green sheet having an outer diameter of about 110 mm and an inner diameter of about 30 μm cut into a donut shape. A 120 μm tetragonal zirconia green sheet and a tetragonal zirconia green sheet with an outer diameter of about 30 mm and an inner diameter of about 20 mm cut into a ring shape on the inner periphery are fitted into a ring shape, and release treatment is performed on the upper and lower surfaces thereof. The PET film was placed and placed in a mold having an outer diameter of 120 mm and an inner diameter of 20 mm and held at a temperature range of 35 ° C., and was pressed at 40 MPa for 20 seconds to produce an integrated green sheet Ag having the configuration of FIG. .

(Production of integrated green sheet in FIG. 7)
The outer diameter is about 110 mm and the inner diameter is about 30 mm so that the center point coincides with one surface of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 30 mm, and a thickness of about 80 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. This green sheet has a ring-shaped tetragonal zirconia green sheet with an outer diameter of about 120 mm, an inner diameter of about 110 mm and a thickness of about 40 μm, and an inner circumference with an outer diameter of 30 mm and an inner diameter of about 20 mm. A ring-shaped tetragonal zirconia green sheet having a diameter of 40 μm is fitted, and PET films are arranged on the upper and lower surfaces in the same manner as described above, put into a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to form 2 in the configuration of FIG. An integrated green sheet Dg having a layer structure was produced.

(Preparation of integrated green sheet in FIG. 8)
The outer diameter is about 110 mm and the inner diameter is about 30 mm so that the center point coincides with both faces of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 30 mm and a thickness of about 40 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. A ring-shaped tetragonal zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 110 mm, and a thickness of about 40 μm on the outer peripheral edges of both sides of the green sheet, and an inner diameter of about 30 mm and an inner diameter of about 20 mm. A ring-shaped tetragonal zirconia green sheet having a thickness of about 40 μm is fitted, and PET films are arranged on the upper and lower surfaces in the same manner as described above, placed in a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to obtain the one shown in FIG. An integrated green sheet Eg having a three-layer structure was produced.

(Production of integrated green sheet in FIG. 9)
There are arc-shaped cuts with an outer diameter of about 120 mm and four arcs with a width of about 10 mm, and the outer periphery of the doughnut-shaped cubic zirconia green sheet with an inner diameter of about 30 mm and a thickness of about 120 μm A tetragonal zirconia green sheet with a diameter of about 120 mm, an inner diameter of about 110 μm, and a thickness of about 120 μm, and an inner periphery with an outer diameter of about 30 mm, an inner diameter of about 20 mm, and a thickness of about 120 μm. The tetragonal zirconia green sheet was inserted, and the PET film subjected to the mold release treatment was placed on the upper and lower surfaces thereof, placed in a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and kept at a temperature range of 35 ° C. The integrated green sheet Fg of the structure of FIG. 9 was produced by pressurizing for 2 seconds.

(Preparation of integrated green sheet in FIG. 12)
Thickness with an outer diameter of about 110 mm and an inner diameter of about 30 mm so that the center point coincides with one surface of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 110 mm, an inner diameter of about 20 mm, and a thickness of about 80 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. A ring-shaped tetragonal zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 110 mm, and a thickness of about 120 μm at the outer peripheral edge of the green sheet, and an outer diameter of about 30 mm and an inner diameter of about 20 mm at the inner peripheral edge. A ring-shaped tetragonal zirconia green sheet having a diameter of about 40 μm is fitted, and a PET film is arranged on the upper and lower surfaces in the same manner as described above, put into a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to form the structure shown in FIG. An integrated green sheet Ig having a two-layer structure was produced.

(Preparation of integrated green sheet in FIG. 13)
Thickness with an outer diameter of about 110 mm and an inner diameter of about 30 mm so that the center point coincides with one surface of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 20 mm, and a thickness of about 80 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. This green sheet has a ring-shaped tetragonal zirconia green sheet with an outer diameter of about 120 mm, an inner diameter of about 110 mm and a thickness of about 40 μm, and an inner circumference with an outer diameter of about 30 mm and an inner diameter of about 20 mm. A ring-shaped tetragonal zirconia green sheet of about 40 μm is fitted, and PET films are arranged on the upper and lower surfaces thereof in the same manner as described above, put in a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to form the structure shown in FIG. An integrated green sheet Jg having a two-layer structure was produced.

(Preparation of integrated green sheet in FIG. 16)
The outer diameter is about 110 mm and the inner diameter is about 30 mm so that the center point coincides with both faces of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 110 mm, an inner diameter of about 20 mm, and a thickness of about 40 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. This green sheet has a ring-shaped tetragonal zirconia green sheet with an outer diameter of about 120 mm, an inner diameter of about 110 mm and a thickness of about 40 μm, and an inner circumference with an outer diameter of about 30 mm and an inner diameter of about 20 mm. A ring-shaped tetragonal zirconia green sheet having a diameter of about 40 μm is fitted, and PET films are arranged on the upper and lower surfaces in the same manner as described above, put into a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to form the structure shown in FIG. An integrated green sheet Mg having a three-layer structure was produced.

(Preparation of integrated green sheet in FIG. 17)
The outer diameter is about 110 mm and the inner diameter is about 30 mm so that the center point coincides with both faces of a doughnut-shaped cubic zirconia green sheet having an outer diameter of about 120 mm, an inner diameter of about 20 mm, and a thickness of about 40 μm. A doughnut-shaped cubic zirconia green sheet having a thickness of about 40 μm was arranged. This green sheet has a ring-shaped tetragonal zirconia green sheet with an outer diameter of about 120 mm, an inner diameter of about 110 mm and a thickness of about 40 μm, and an inner circumference with an outer diameter of about 30 mm and an inner diameter of about 20 mm. A ring-shaped tetragonal zirconia green sheet having a diameter of about 40 μm is fitted, and a PET film is arranged on the upper and lower surfaces thereof in the same manner as described above, placed in a mold having an outer diameter of 120 mm and an inner diameter of 20 mm, and pressurized to form the structure shown in FIG. An integrated green sheet Ng having a three-layer structure was produced.

(Iii) Integrated green sheet firing Two sheets of 150 mm square alumina porous sheets (porosity: 45%, thickness: 0.2 mm) are stacked on top of each other, and the integrated green sheets Ag ~ One piece of Ng was placed thereon, and a porous sheet was placed thereon as a spacer, and three integrated green sheets and porous sheets were alternately stacked to form a laminate. Four sets of this laminate are placed on a baking shelf (thickness 20 mm, 400 mm × 400 mm), and a mullite / alumina weight jig (porosity: 60%) is placed on the top of each laminate. , Bulk specific gravity: 1.3). Cubic zirconia having an outer diameter of about 100 mm, an inner diameter of about 18 mm, and a thickness of about 100 μm, at least one part of which is mainly tetragonal zirconia by sintering in air at 1420 ° C. for 3 hours. 64 thin film electrolyte sheets As to Ns were prepared.

  In addition, a cubic zirconia green sheet Rg having an outer diameter of about 120 mm and an inner diameter of about 20 μm cut into a donut shape is fired in the same manner, and a thin film cubic zirconia sheet containing no tetragonal zirconia Thirty-two Rs were produced.

(Iv) Physical Properties of Cubic Zirconia Thin Film Electrolyte Sheets Cubic Zirconia Thin Film Electrolyte Sheets As to Ns in which at least one part of the peripheral edge of the present invention is mainly tetragonal zirconia, and comparative cubic zirconia The relative density and thickness of the thin film electrolyte sheet Rs were measured. The relative density was calculated from the theoretical density of 3YSZ and 10Sc1CeSZ by measuring the density of any 10 sheets by the Archimedes method.

  Further, for any 10 sheets whose relative density was measured, the length of the region in the plane direction of cubic zirconia and tetragonal zirconia and the length of the region in the thickness direction of the cross section were measured with a micrometer. The average value of the ratio was calculated. In addition, the length of the region in the planar direction and the region in the thickness direction of the tetragonal zirconia are indicated by a groove-like mark at the interface between the cubic zirconia green sheet and the tetragonal zirconia green sheet in the integrated green sheet. The position of the groove observed in the zirconia sheet after the baking was defined as the boundary between cubic zirconia and tetragonal zirconia. The results are shown in Table 1.

(V) Production of Electrolyte-Supported Half Cell Using the electrolyte sheets As to Ns and Rs, a fuel electrode was formed on one surface of each electrolyte sheet to produce 20 electrolyte-supported half cells (ESHC). Specifically, on one surface of each electrolyte sheet, 60 parts by mass of nickel oxide powder having an average particle size of 0.9 μm obtained by thermally decomposing basic nickel carbonate and a commercially available 8YSZ-based powder (manufactured by Daiichi Rare Element Co., Ltd.) A fuel electrode paste composed of 40 parts by mass was applied by screen printing except for a peripheral part having a width of 5 mm from the outer peripheral edge and a peripheral edge of 5 mm from the inner peripheral edge, and dried. Next, it was calcined at 1350 ° C. for 2 hours to produce 32 pieces of ESHC (Ahc to Nhc, Rhc) each having a fuel electrode layer thickness of about 40 μm. Further, on the surface of the ESHC electrolyte sheet, from 80 parts by mass of commercially available strontium-doped lanthanum manganate (La _0.6 Sr _0.4 MnO ₃ ) powder and 20 parts by mass of commercially available 20 mol% gadolinia-doped ceria powder. The resulting air electrode paste was applied by screen printing in the same manner as the fuel electrode paste, and dried. Subsequently, it fired at 1300 degreeC for 3 hours, and produced each 16 pieces of ESC whose thickness of an air electrode layer is about 30 micrometers.

(Vi) Oxidation / Reduction Test of Electrolyte-Supported Half Cell Using the ESHC (Ahc to Nhc, Rhc), the cell can be held horizontally as shown in the schematic diagram of the oxidation / reduction test and oxidation test apparatus in FIG. The peripheral edge of the electrolyte was fixed to the lower manifold (I) made of alumina so that the fuel electrode was below, and the upper manifold (H) was mounted. While introducing 750 mL / min of hydrogen from the gas inlet pipe (J) of the lower manifold, the temperature was raised to 800 ° C. and the fuel electrode was held in a reducing atmosphere for 1 hour. Then, the hydrogen was stopped and air of 1500 mL / min was supplied. The fuel electrode was introduced and held in an oxidizing atmosphere for 1 hour. This oxidation / reduction test was repeated 5 times in total using 5 ESHCs. Nitrogen was flown at the time of gas switching between air and hydrogen so that air and hydrogen were not mixed directly. Then, after cooling to room temperature, the upper manifold (H) was removed, and the occurrence of cracks / cracks in the electrolyte sheet on the upper surface side of the half cell was confirmed by visual observation. The peripheral edge of the electrolyte was fixed to the lower manifold using a heat-resistant silicone adhesive sealant (manufactured by ThreeBond). The results are shown in Table 1.

(Vii) Oxidation test of electrolyte-supported half-cell Using ESHC (Ahc to Nhc, Rhc), the periphery of the electrolyte was fixed to the lower manifold in the same manner as in the oxidation / reduction test. A manifold was placed. While introducing 750 mL / min of hydrogen from the gas inlet pipe (J) of the lower manifold, the temperature was raised to 800 ° C. and the fuel electrode was held in a reducing atmosphere for 1 hour, after which hydrogen was stopped and the pressure in the lower manifold was reduced. Then, after the hydrogen was quickly discharged from the gas discharge pipe (K), an oxidation test was performed using five ESHCs by introducing 1500 mL / min of air and holding the fuel electrode in an oxidizing atmosphere for 1 hour. In addition, after stopping hydrogen, it cooled to room temperature after that, the upper manifold (H) was removed, and the cracking state of the electrolyte sheet on the upper surface side of the half cell was confirmed by visual observation. The results are shown in Table 1.

  From Table 1, ESHC of actual machine level using the thin film electrolyte sheet of the present invention is repeatedly exposed to an oxidizing / reducing atmosphere, or cracks and cracks are generated even under severe setting conditions where it is rapidly exposed to an oxidizing atmosphere. Has been reduced. On the other hand, almost all ESHC cracks were observed in the ESHC using a simple cubic zirconia sheet whose peripheral part was not framed with tetragonal zirconia.

  The thin-film cubic zirconia sheet for solid oxide fuel cells of the present invention responds to market demands for thin films, particularly when an electrolyte-supported cell is repeatedly exposed to an oxidizing / reducing atmosphere or suddenly. Since the occurrence of cracks and cracks is reduced even when exposed to an oxidizing atmosphere, a cubic zirconia sheet having a thickness of 50 μm or more and 180 μm or less and excellent reliability is provided.

Claims (5)

An electrolyte sheet for a solid oxide fuel cell,
Having at least one hole in the sheet plane;
The sheet thickness is a uniform thickness in the range of 50 μm to 180 μm,
A thin film electrolyte sheet for a solid oxide fuel cell, wherein the crystal structure of the sheet is mainly cubic zirconia, and at least a part of the peripheral edge of the sheet is mainly tetragonal zirconia. The region of the sheet that is primarily tetragonal zirconia,
In at least one sheet plane, it is a region in the range of at least 10 mm inside from the peripheral edge and the peripheral edge, and at least one cross section in the thickness direction of the outer peripheral edge and the inner peripheral edge is 50% to 100% of the thickness The thin film electrolyte sheet according to claim 1, wherein the thin film electrolyte sheet is in a range of%.   The positions of all the holes in the plane of the sheet are arranged at least 4 mm from the peripheral edge of the sheet, and the total area of all the holes in the sheet surface The thin film electrolyte sheet according to claim 1 or 2, which is 10% or less of a planar area to be included.   The cubic zirconia is a stabilized zirconia containing 7 to 15 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium, cerium and ytterbium as a stabilizer, and the square The crystalline zirconia is a stabilized zirconia containing 3 to 6 mol% of an oxide of at least one element selected from the group consisting of scandium, yttrium and ytterbium as a stabilizer. The thin film electrolyte sheet according to item.   The cell for solid oxide fuel cells containing the electrolyte sheet of any one of Claims 1-4.

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