JP5746399B2 - Solid oxide fuel cell - Google Patents

Description

  The present invention relates to a solid oxide fuel cell including a barrier layer.

  A solid oxide fuel cell generally includes a porous fuel electrode, a dense solid electrolyte layer, and a porous air electrode.

  Conventionally, a method of interposing a porous barrier layer between a solid electrolyte layer and an air electrode has been proposed in order to suppress the formation of a high resistance layer between the solid electrolyte layer and the air electrode (patent) Reference 1). In Patent Document 1, by setting the porosity of the porous barrier layer to 10 to 80%, the components of the air electrode are trapped in the voids in the porous barrier layer, so that it is possible to suppress a decrease in power generation performance. ing.

JP 2010-3478 A

  However, in Patent Document 1, since the porosity of the porous barrier layer is high, the constituent components of the solid electrolyte layer and the air electrode are easily diffused into the porous barrier layer. Therefore, there is a limit in suppressing the decrease in power generation performance.

  The present invention has been made in view of the above-described situation, and an object thereof is to provide a solid oxide fuel cell capable of suppressing a decrease in power generation performance.

  The solid oxide fuel cell according to the present invention includes a fuel electrode, an air electrode, a solid electrolyte layer, a barrier layer, and an air electrode. The solid electrolyte layer is disposed between the fuel electrode and the air electrode. The barrier layer is disposed between the solid electrolyte layer and the air electrode, and contains a ceria-based material as a main component. The porosity of the barrier layer is less than 10%. The barrier layer has a plurality of closed spaces formed at the grain boundaries of the plurality of barrier layer particles constituting the barrier layer.

  ADVANTAGE OF THE INVENTION According to this invention, the solid oxide fuel cell which can suppress the fall of electric power generation performance can be provided.

Enlarged sectional view showing the structure of a solid oxide fuel cell Sectional view schematically showing the cross section near the interface between the barrier layer and the air electrode STEM image in which the cross section near the interface between the barrier layer and the air electrode is magnified 30,000 times

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Configuration of Solid Oxide Fuel Cell 10)
A configuration of a solid oxide fuel cell (SOFC) 10 will be described with reference to the drawings. FIG. 1 is an enlarged cross-sectional view showing a configuration of a solid oxide fuel cell 10.

  The solid oxide fuel cell 10 is a vertical, horizontal, fuel electrode support, electrolyte flat plate, or cylindrical fuel cell. As shown in FIG. 1, the solid oxide fuel cell 10 includes a fuel electrode 20, a solid electrolyte layer 30, a barrier layer 40, and an air electrode 50.

  The fuel electrode 20 functions as an anode of the solid oxide fuel cell 10. As illustrated in FIG. 1, the fuel electrode 20 includes a fuel electrode current collecting layer 21 and a fuel electrode active layer 22.

  The anode current collecting layer 21 is a porous plate-like fired body. The anode current collecting layer 21 may contain nickel (Ni) and an oxygen ion conductive material as main components. The anode current collecting layer 21 may contain Ni as NiO. When the anode current collecting layer 21 contains NiO, NiO may be reduced to Ni by hydrogen gas during power generation. Examples of the oxygen ion conductive material include yttria stabilized zirconia (3YSZ, 8YSZ, 10YSZ, etc.), scandia stabilized zirconia (ScSZ), and the like. In the anode current collecting layer 21, the volume ratio of Ni and / or NiO can be 35 to 65% by volume in terms of Ni, and the volume ratio of the oxygen ion conductive material can be 35 to 65% by volume. . The porosity of the anode current collecting layer 21 during reduction is preferably 15% or more and 50% or less. The thickness of the anode current collecting layer 21 can be set to 0.2 mm to 5.0 mm.

  In the present embodiment, “the composition A contains the substance B as a main component” preferably means that the content of the substance B in the composition A is 60% by weight or more, and more preferably, It means that the content of the substance B in the composition A is 70% by weight or more.

  The anode active layer 22 is disposed between the anode current collecting layer 21 and the solid electrolyte layer 30. The anode active layer 22 is a porous plate-like fired body. The anode active layer 22 contains Ni and oxygen ion conductive material as main components. The anode active layer 22 may contain Ni as NiO. When the anode active layer 22 contains NiO, NiO may be reduced to Ni by hydrogen gas during power generation. Examples of the oxygen ion conductive material include yttria stabilized zirconia (3YSZ, 8YSZ, 10YSZ, etc.), scandia stabilized zirconia (ScSZ), and the like. In the anode active layer 22, the volume ratio of Ni and / or NiO can be 25 to 50% by volume in terms of Ni, and the volume ratio of the oxygen ion conductive material can be 50 to 75% by volume. The porosity of the fuel electrode active layer 22 at the time of reduction is preferably 15% or more and 50% or less. The thickness of the anode active layer 22 can be 5.0 μm to 30 μm.

  The solid electrolyte layer 30 is disposed between the fuel electrode 20 and the barrier layer 40. The solid electrolyte layer 30 is co-fired with the fuel electrode 20 and the barrier layer 40. The solid electrolyte layer 30 has a function of transmitting oxygen ions generated at the air electrode 50. Examples of the material of the solid electrolyte layer 30 include 3YSZ, 8YSZ, 10YSZ, and ScSZ. The thickness of the solid electrolyte layer 30 can be 3 μm to 30 μm. The solid electrolyte layer 30 is dense, and the porosity of the solid electrolyte layer 30 is preferably 10% or less.

The barrier layer 40 is disposed between the solid electrolyte layer 30 and the air electrode 50. The barrier layer 40 is co-fired with the fuel electrode 20 and the solid electrolyte layer 30. The barrier layer 40 suppresses the formation of a high resistance layer between the solid electrolyte layer 30 and the air electrode 50. The barrier layer 40 contains a ceria-based material in which ceria (CeO ₂ ) or a rare earth metal oxide is dissolved in CeO ₂ as a main component. Such ceria-based materials, such as gadolinium doped ceria (GDC: (Ce, Gd) O 2) or samarium-doped ceria (SDC: (Ce, Sm) O 2) , and the like. The barrier layer 40 may contain zirconium (Zr), yttrium (Y), scandium (Sc), Ca (calcium), or an oxide thereof. The barrier layer 40 is dense, and the porosity of the barrier layer 40 is less than 10%. The porosity of the barrier layer 40 is a volume ratio of pores (including voids and a closed space described later) to the total volume of the barrier layer 40. The thickness of the barrier layer 40 can be 3 μm to 20 μm. The fine structure inside the barrier layer 40 will be described later.

  As shown in FIG. 1, the barrier layer 40 forms an interface P <b> 1 with the air electrode 50. The interface P1 is formed by the surface of the barrier layer 40 on the air electrode 50 side. The interface P1 is defined by a line in which the concentration distribution changes abruptly when mapping the component concentrations of the barrier layer 40 and the air electrode 50, or a line in which the porosity changes abruptly between the barrier layer 40 and the air electrode 50. be able to.

  As shown in FIG. 1, the barrier layer 40 forms an interface P <b> 2 with the solid electrolyte layer 30. The interface P2 is formed by the surface of the barrier layer 40 on the solid electrolyte layer 30 side. For the interface P2, the concentration distribution of the main component (for example, cerium) of the barrier layer 40 and the main component (for example, zirconium) of the solid electrolyte layer 30 is line-analyzed in the thickness direction by an electron probe microanalyzer (EPMA). In some cases, each density can be defined as a matching line.

The air electrode 50 is disposed on the barrier layer 40. The air electrode 50 functions as a cathode of the solid oxide fuel cell 10. The air electrode 50 is a porous plate-like fired body. The air electrode 40 is represented by the general formula ABO ₃ and contains a perovskite complex oxide containing at least one of La and Sr at the A site as a main component. Examples of such perovskite complex oxides include lanthanum strontium cobalt ferrite (LSCF: (La, Sr) (Co, Fe) O ₃ ), lanthanum strontium ferrite (LSF: (La, Sr) FeO ₃ ), and lanthanum strontium. Examples thereof include cobaltite (LSC: (La, Sr) CoO ₃ ), lanthanum strontium manganite (LSM: (La, Sr) MnO ₃ ), and samarium strontium cobaltite (SSC: (Sm, Sr) CoO ₃ ). . The porosity of the air electrode 50 can be set to 25% to 50%. The thickness of the air electrode 50 can be 3 μm to 600 μm.

(Microstructure inside the barrier layer 40)
The microstructure inside the barrier layer 40 will be described with reference to the drawings. FIG. 2 is a cross-sectional view schematically showing the microstructure inside the barrier layer 40.

  The barrier layer 40 has a plurality of convex portions 41. The center part of the convex part 41 protrudes to the air electrode 50 side. As shown in FIG. 2, the convex portion 41 is formed by particles (hereinafter referred to as “barrier layer particles”) 40 a constituting the barrier layer 40. Of the barrier layer particles 40a, the convex portions 41 are formed in a cone shape. The surface of the convex portion 41 is formed in a curved surface shape. Therefore, the cross section of the convex portion 41 protrudes so as to curve toward the air electrode 50 side.

  The plurality of convex portions 41 are arranged in a matrix, and the surface of the barrier layer 40 on the air electrode 50 side is thereby formed. That is, the interface P is formed by connecting the surfaces of the barrier layer particles 40a and has a periodic uneven shape. Thus, the interface P has a periodic uneven shape, so that the contact area between the barrier layer 40 and the air electrode 50 is increased.

  The average equivalent circle diameter of the barrier layer particles 40a can be not less than 0.5 μm and not more than 3 μm. The average equivalent circle diameter of the barrier layer particles 40a is an arithmetic average value of the diameters of circles having the same cross-sectional area as the barrier layer particles 40a. In the present embodiment, “average” means an arithmetic average of measured values for each barrier layer particle 40a. When determining the average value, the number of samples of the barrier layer particles 40a is preferably 10 or more. However, since the barrier layer particle 40a having an equivalent circle diameter of 0.05 μm or less has a small contribution to the increase in the contact area, when calculating the average equivalent circle diameter, the barrier layer particle 40a having an equivalent circle diameter of 0.05 μm or less. Is preferably excluded.

  The average width W of the convex portion 41 can be 0.1 μm or more and 2 μm or less. The average width W of the convex portions 41 is preferably 0.3 μm or more and 1.5 μm or less. The average width W of the convex portion 41 corresponds to the average shortest distance between both ends of the convex portion 41 as shown in FIG.

  The average height H of the convex portions 41 can be 0.01 μm or more and 1 μm or less. The average height H of the convex portions 41 is preferably 0.03 μm or more and 0.5 μm or less. The average height H of the convex portion 41 corresponds to the average shortest distance between the straight line connecting both ends of the convex portion 41 and the top PP, as shown in FIG.

  Further, the ratio of the average height H to the average width W of the convex portions 41 (hereinafter referred to as “height-width ratio”) H / W is 0.05 or more. As the height-width ratio H / W is larger, the convex portion 41 has a steeper shape, and the contact area between the barrier layer 40 and the air electrode 50 can be further increased. The height-width ratio H / W is preferably 0.4 or less.

  The first radius of curvature CR1 at the top PP of the convex portion 41 is preferably 3.5 μm or less. Since the convex portion 41 becomes steeper as the first radius of curvature CR1 is smaller, the barrier layer 40 exhibits an anchor effect. The first radius of curvature CR1 is more preferably 0.3 μm or more.

  It is preferable that the second radius of curvature CR2 at the deepest portion DP between two adjacent convex portions 41 is 2.0 μm or less. The second curvature radius CR2 is more preferably 0.8 μm or more. The deepest portion DP is a region including a grain boundary between two adjacent barrier layer particles 40a. As the second curvature radius CR2 is smaller, the deepest portion DP is cut off, so that the air electrode 50 that has entered the deepest portion DP exhibits an anchor effect.

Moreover, the barrier layer 40 has a plurality of closed spaces 42 as shown in FIG. The closed space 42 is disposed at the grain boundary of the barrier layer particles 40a. When the cross section of the barrier layer 40 is observed with a STEM (Scanning Transmission Electron Microscope (STEM)) of 30,000 magnifications, it is preferable that one or more closed spaces 42 are formed per 10 μm ² . That is, the existence ratio of the closed space 42 in the cross section of the barrier layer 40 is preferably 1/10 μm ² or more In the present embodiment, the fact that the barrier layer 40 has the closed space 42 means that the closed space 42 in the cross section. It means that the abundance ratio is 1/10 μm ² or more.

  At least some of the components of the air electrode 50 may be accumulated in at least some of the closed spaces 42. In addition, at least some of the constituent components of the solid electrolyte layer 30 may be accumulated in at least some of the plurality of closed spaces 42. Further, even if at least a part of the plurality of closed spaces 42 includes a composite oxide including a part of the constituent components of the air electrode 50 and a part of the constituent components of the solid electrolyte layer 30. Good.

Examples of the component of the air electrode 50 accumulated in the closed space 42 include Sr and La, but are not limited thereto. Examples of the constituent component of the solid electrolyte layer 30 accumulated in the closed space 42 include, but are not limited to, Zr. Examples of the composite oxide accumulated in the closed space 42 include, but are not limited to, SrZrO ₃ and La ₂ Zr ₂ O ₇ .

  The components of the air electrode 50, the components of the solid electrolyte layer 30, and these composite oxides (hereinafter collectively referred to as “accumulated substances”) may be mixed in the same closed space 42. The accumulation material may be filled in the entire closed space 42 or may be disposed only in a part of the closed space 42.

  Here, the constituent components of the air electrode 50 and the solid electrolyte layer 30 may be diffused into the barrier layer 40 not only when the molded body of each layer is fired but also when the fuel cell is operating at a high temperature. is there. Accordingly, the accumulated material may be already accumulated in the closed space 42 when the fuel cell is completed, or may be gradually accumulated in the closed space 42 during use of the fuel cell. Thus, by disposing a plurality of closed spaces 42 at the grain boundaries of the barrier layer particles 40a, it is possible to trap diffusion components that move through the grain boundaries of the barrier layer particles 40a during firing and use.

  The average equivalent circle diameter of the closed space 42 can be 10 nm or more and 100 nm or less. The average equivalent circle diameter of the closed space 42 is preferably 20 nm or more. The average equivalent circle diameter of the closed space 42 is an arithmetic average value of the diameters of circles having the same cross-sectional area as the closed space 42. In the present embodiment, “average” means an arithmetic average of measured values for each closed space 42. When obtaining the average value, the number of samples in the closed space 42 is preferably 10 or more. However, since the closed space 42 with an equivalent circle diameter of 3 nm or less has a small contribution to the accumulation of the components of the air electrode, the closed space 42 with an equivalent circle diameter of 3 nm or less is excluded when calculating the average equivalent circle diameter. It is preferable to do.

(Method for Manufacturing Solid Oxide Fuel Cell 10)
Next, an example of a method for manufacturing the solid oxide fuel cell 10 will be described. However, various conditions such as the material, particle size, temperature, and coating method described below can be changed as appropriate.

  First, a molded body of the anode current collecting layer 21 is formed by molding an anode current collecting layer powder by a die press molding method.

  Next, PVA (polyvinyl butyral) is added as a binder to a mixture of the fuel electrode active layer powder and a pore-forming agent (for example, PMMA) to prepare a slurry. Subsequently, the slurry is printed on the molded body of the anode current collecting layer 21 by a printing method or the like to form the molded body of the anode active layer 22.

  Next, water and a binder are mixed with the solid electrolyte layer powder to prepare a slurry. Subsequently, the slurry is applied onto the molded body of the fuel electrode 20 by a coating method or the like to form the molded body of the solid electrolyte layer 30.

  Next, water and a binder are mixed with the barrier layer powder (for example, GDC) to prepare a slurry. Subsequently, the slurry is applied onto the molded body of the solid electrolyte layer 30 by a coating method or the like to form the molded body of the barrier layer 40.

At this time, the number and size of the closed spaces 42 in the barrier layer 40 can be adjusted by controlling at least one of the three factors listed below.
-The amount and size of the pore former added to the slurry using the barrier layer powder-The powder filling rate of the molded body of the barrier layer 40-The amount and size of impurities (for example, Zr) added to the barrier layer powder

  Next, the laminate of the molded body is co-sintered at 1300 to 1600 ° C. for 2 to 20 hours to form a co-fired body of the fuel electrode 20, the solid electrolyte layer 30, and the barrier layer 40.

At this time, the shape and size of the protrusion 41 in the barrier layer 40 can be adjusted by using at least one of the following two conditions.
The firing start temperature is in the order of the fuel electrode 20 <solid electrolyte layer 30 <barrier layer 40. The firing shrinkage ratio is in the order of the solid electrolyte layer 30 <barrier layer 40 <fuel electrode 20 and the barrier layer 40. The firing shrinkage ratio of the solid electrolyte layer 30 should be larger than the firing shrinkage ratio by about 0.5% to 3.5%.

  Next, water and a binder are mixed with air electrode material powder (for example, LSCF, LSF, LSC, LSM-8YSZ, etc.) to prepare a slurry. And the slurry is apply | coated on the barrier layer 40 using the apply | coating method etc., and the molded object of the air electrode 50 is formed.

  Next, the co-fired body and the molded body of the air electrode 50 are sintered at 900 to 1100 ° C. for 1 to 20 hours.

(Function and effect)
In this embodiment, the porosity of the barrier layer 40 is less than 10%. Therefore, when the barrier layer is porous, that is, compared with the case where voids (including pores) are formed inside the barrier layer, the components of the air electrode 50 and the solid electrolyte layer 30 are formed inside the barrier layer 40. Can be prevented from diffusing.

  The barrier layer 40 has a plurality of closed spaces 42 formed at the grain boundaries of the barrier layer particles 40a. Therefore, the constituent components of the air electrode 50 and the solid electrolyte layer 30 that move through the grain boundaries of the barrier layer particles 40 a can be accumulated in the closed space 42.

  As described above, according to the solid oxide fuel cell 10 according to the present embodiment, the constituents of the air electrode 50 and the solid electrolyte layer 30 are prevented from diffusing into the barrier layer 40, and the barrier layer particles 40a. A very small amount of diffusion component moving through the grain boundary can be accumulated in the closed space 42. As a result, it is possible to prevent the power generation performance of the solid oxide fuel cell 10 from being lowered.

(Other embodiments)
The present invention is not limited to the embodiment described above, and various modifications or changes can be made without departing from the scope of the present invention.

  For example, in the above embodiment, the air electrode 50 has a porous single layer structure, but may have a porous multilayer structure. Specifically, the air electrode 50 may have an active layer formed on the barrier layer 40 and a current collecting layer formed on the active layer. The active layer can be composed of a mixed conductive material having both oxygen ion conductivity and electron conductivity.

  Moreover, in the said embodiment, although the air electrode 50 was arrange | positioned on the barrier layer 40, it is not restricted to this. A porous barrier layer having a higher porosity than the barrier layer 40 may be interposed between the barrier layer 40 and the air electrode 50. Such a porous barrier layer can be formed by applying a slurry using the same material as that of the barrier layer 40 onto the co-fired barrier layer 40 and then firing (1200 to 1500 ° C. for 1 to 20 hours). . The porosity of the porous barrier layer is preferably 15% or more. The thickness of the porous barrier layer can be 1 to 50 μm. Note that the interface between the barrier layer 40 and the porous barrier layer can be defined as a line in which the porosity rapidly changes.

  Examples of the cell according to the present invention will be described below. However, the present invention is not limited to the examples described below.

[Production of Sample No. 1]
Sample No. 1 was produced as follows.

  First, a mixed powder of NiO and 8YSZ was molded by a die press molding method to form a molded body of a fuel electrode current collecting layer.

  Next, PVA was added to a mixture of NiO, 8YSZ, and PMMA to prepare a slurry. Subsequently, this slurry was printed on a molded body of the anode current collecting layer to form a molded body of the anode active layer.

  Next, 8YSZ was mixed with water and a binder to prepare a slurry. Subsequently, this slurry was applied on the molded body of the fuel electrode active layer to form a molded body of the solid electrolyte layer.

  Next, a slurry was prepared by mixing water and a binder with GDC. Subsequently, this slurry was applied onto the solid electrolyte layer compact to form a barrier layer compact.

  Next, the laminates of the molded bodies of the fuel electrode, the solid electrolyte layer, and the barrier layer were co-fired (1400 ° C., 5 hours) to produce a co-fired body of the fuel electrode, the solid electrolyte layer, and the barrier layer.

  Next, water and a binder were mixed with LSCF to prepare a slurry. Subsequently, this slurry was applied onto the barrier layer to form an air electrode molded body.

  Next, the air electrode compact was fired at 1050 ° C. for 5 hours to produce an air electrode.

[Production of sample Nos. 2 to 6]
In Sample Nos. 2 to 6, a plurality of closed spaces were formed at the grain boundaries of the barrier layer particles constituting the barrier layer by adding a pore former to the GDC slurry of the barrier layer. At this time, the average equivalent circle diameter of the closed space was changed as shown in Table 1 by adjusting the size of the pore former.

  In sample Nos. 2 to 6, the firing start temperature of the co-fired body is in the order of fuel electrode <solid electrolyte layer <barrier layer, and the firing shrinkage is in the order of solid electrolyte layer <barrier layer <fuel electrode. Thus, as shown in Table 1, the shape and size of the protrusions of the barrier layer were adjusted.

  The other steps are the same as the sample No. Same as 1.

[Observation of microstructure inside barrier layer]
The cross section of each sample was imaged with a STEM of 30,000 magnifications to obtain a STEM image as shown in FIG.

  Next, in the STEM image, the presence / absence of a closed space formed at the grain boundary of the barrier layer particles was confirmed, and the average equivalent circle diameter of the closed space was measured. Further, in the STEM image, the size of GDC particles (barrier layer particles) and the shape of the convex portions of the barrier layer in the vicinity of the interface between the barrier layer and the air electrode were observed. Table 1 shows the results of confirming the presence or absence of the closed space, the measurement result of the average equivalent circle diameter of the closed space, the measurement result of the average equivalent circle diameter of the GDC particles, and the observation result of the shape of the convex portion.

[Identification of substance in closed space]
Regarding Sample Nos. 1 to 6, the substances accumulated in the closed space were identified by an element such as EPMA or EDX, and the structural analysis of the reaction product was identified by STEM electron diffraction. As a result, it was confirmed that SrZrO ₃ , which is a complex oxide of Sr, which is a component of the air electrode, and Zr, which is a component of the solid electrolyte layer, is formed in the closed space.

[Power generation test]
Reducing sample Nos. 1-6 by supplying hydrogen gas to the fuel electrode for 3 hours after raising the temperature to 800 ° C. while supplying air to the air electrode side while supplying nitrogen gas to the fuel electrode side Processed. Then, about sample No. 1-6, the cell voltage fall rate (rate of change of the cell voltage of 1000 hours) was measured on constant current conditions (current density: 0.3 A / cm < ² >). The measurement results are summarized in Table 1.

[Presence or absence of peeling]
By observing the cross section of sample Nos. 2 to 6 after firing with a microscope, the frequency (number of occurrences) of peeling at the interface between the barrier layer and the air electrode was confirmed. The confirmation results are summarized in Table 1. In Table 1, a sample in which peeling was confirmed was evaluated as “x”, a sample in which peeling was confirmed only at one place was evaluated as “◯”, and a sample in which peeling was not confirmed was evaluated as “” ”.

[Peeling after thermal cycle test]
Next, with respect to Sample Nos. 3 to 6, while maintaining the reducing atmosphere, the cycle of raising the temperature from room temperature to 800 ° C. in 30 minutes and then lowering to room temperature in 1 hour was repeated 10 times. Then, the presence or absence of peeling at the interface between the barrier layer and the air electrode was confirmed by observing the cross section of each sample with a microscope. The confirmation results are summarized in Table 1. In Table 1, a sample in which peeling was confirmed was evaluated as “x”, and a sample in which peeling was not confirmed was evaluated as “◎”.

  As can be seen from Table 1, in Sample Nos. 2 to 6 where a closed space exists in the barrier layer, the cell voltage drop rate could be suppressed. This is because an increase in the electrical resistance of the barrier layer can be suppressed by trapping the constituent components of the air electrode and the solid electrolyte layer that have diffused into the barrier layer in the closed space. Since it was difficult to stably produce a closed space having an average equivalent circle diameter of less than 10 nm, Sample Nos. 2 to 6 produced closed spaces having an average equivalent circle diameter of 10 nm or more. In consideration of the risk of cracking during the thermal cycle test, Samples Nos. 2 to 6 produced closed spaces with an average equivalent circle diameter of 100 nm or less.

  Further, as can be seen from Table 1, in sample Nos. 3 to 6, in which the average equivalent circle diameter of the barrier layer particles is 0.5 μm or more and 3 μm or less, and the height-width ratio H / W is 0.05 or more, The occurrence frequency of peeling at the time after firing could be suppressed. This is because the bonding area between the barrier layer and the air electrode can be increased.

  Moreover, in sample No. 3-6 whose curvature radius of a top part is 3.5 micrometers or less, peeling was not observed after the thermal cycle test.

  Further, in Sample Nos. 3 to 6 in which the curvature radius of the deepest part was 2 μm or less, the occurrence frequency of peeling could be suppressed even after the thermal cycle test.

DESCRIPTION OF SYMBOLS 10 Fuel cell 20 Fuel electrode 30 Solid electrolyte layer 40 Barrier layer 40a Barrier layer particle | grains 41 Convex part 42 Closed space 50 Air electrode PP Top part DP Deepest part

Claims (7)

An anode,
The air electrode,
A solid electrolyte layer disposed between the fuel electrode and the air electrode;
A barrier layer disposed between the solid electrolyte layer and the air electrode and containing a ceria-based material as a main component;
With
The porosity of the barrier layer is less than 10%;
The barrier layer has a plurality of closed spaces formed at grain boundaries of a plurality of barrier layer particles constituting the barrier layer.
Solid oxide fuel cell. The average equivalent circle diameter of the plurality of closed spaces is 10 nm or more and 100 nm or less.
The solid oxide fuel cell according to claim 1. In the closed space, a composite oxide containing constituent components of the air electrode and the solid electrolyte layer is disposed.
The solid oxide fuel cell according to claim 1 or 2. The existence ratio of the plurality of closed spaces in the cross section of the barrier layer is 1 piece / 10 μm ² or more.
The solid oxide fuel cell according to any one of claims 1 to 3. The fuel electrode, the solid electrolyte layer, and the barrier layer are co-fired,
The barrier layer has a plurality of protrusions protruding to the air electrode side,
Each of the plurality of convex portions is formed by barrier layer particles constituting the barrier layer,
The average equivalent circle diameter of the barrier layer particles is 0.5 μm or more and 3 μm or less,
When the interface between the barrier layer and the air electrode is viewed in cross section, the ratio of the average height to the average width of the plurality of convex portions is 0.05 or more and 0.4 or less .
The solid oxide fuel cell according to any one of claims 1 to 4. The curvature radius at the top of each of the plurality of convex portions is 3.5 μm or less.
The solid oxide fuel cell according to claim 5. The radius of curvature at the deepest portion between the plurality of convex portions is 2 μm or less.
The solid oxide fuel cell according to claim 5 or 6.