JP2012146671A - Solid electrolyte fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the low-temperature characteristics of an air electrode for an SOFC by solving the problem of reaction deterioration which arises when a perovskite oxide having a lanthanoid element at A sites and a cobalt element at B sites is used for an air electrode, and by reducing the coefficient of thermal expansion to some extent.SOLUTION: A solid electrolyte fuel cell comprises a fuel electrode, a solid electrolyte, and an air electrode laminated in the order presented above. The air electrode comprises an active layer containing a rare-earth-added ceria and a perovskite oxide (ABO) at a ratio of 10 wt%:90 wt% to 60 wt%:40 wt%, and a collector layer formed on the active layer. The active layer is disposed between the collector layer and the solid electrolyte, and the perovskite oxide has a lanthanoid element at A sites and a cobalt element at B sites, and has a divalent metallic element only at B sites.

Description

  The present invention relates to a SOFC (Solid Oxide Fuel Cell).

  In recent years, interest in SOFCs using oxygen ion conductors is increasing. In particular, from the viewpoint of effective use of energy, solid fuel cells are not subject to the restrictions of Carnot efficiency, so they have inherently high energy conversion efficiency and have excellent features such as better environmental conservation. (Refer nonpatent literature 1).

  This SOFC (also referred to as a solid oxide fuel cell) initially had a high operating temperature of 900 ° C. to 1000 ° C., and all members were made of ceramic. Therefore, it is difficult to reduce the manufacturing cost of the cell stack. Here, if the operating temperature can be reduced to 800 ° C. or lower, a heat-resistant alloy material can be used for the interconnector, and the manufacturing cost can be reduced. However, as the operating temperature decreases, the electrochemical resistance at the air electrode, that is, the overvoltage, increases rapidly, leading to a decrease in output voltage.

The perovskite oxide used in the SOFC air electrode has a composition of ABO _3. The A site contains a lanthanoid metal element, and the B site contains a rare earth metal element having a smaller ionic radius than the A site. Perovskite oxides containing iron and cobalt at the B site, such as La _0.8 Sr _0.2 Fe _0.8 Co _0.2 O _3, are known to be suitable for air electrodes for low-temperature operation because of high electrode activity (Non-patent Document 2). reference). However, perovskite oxide containing iron and cobalt at the B site is liable to cause reaction deterioration with the zirconia solid electrolyte, and a non-conductive layer such as La ₂ Zr ₂ O ₇ or SrZrO ₃ is formed in the zirconia system during firing of the air electrode. It forms at the interface with the solid electrolyte. Therefore, by providing an intermediate layer of rare earth-added ceria or by providing an active layer in a mixture with rare earth-added ceria adjacent to the electrolyte, the formation of the above-described non-conductive layer is suppressed. However, when a long-term operation is performed, Sr added to the A site gradually reacts with ceria to generate SrCeO ₃ , causing a decrease in air electrode characteristics. However, when Sr is not added to the A site, the electrical conductivity is remarkably low and the electrode characteristics are lowered.

By the way, a perovskite oxide containing cobalt at the B site, such as La _0.8 Sr _0.2 CoO _3, has higher activity than the iron-cobalt system, but has a significantly higher coefficient of thermal expansion than the above materials. The difference in expansion is large, and the air electrode is easily peeled off. When Sr or the like is not added, the electrical conductivity does not decrease so much, but the thermal expansion coefficient further increases. For this reason, reliability is still lower.

N. Q. Minh, J. Am. Ceram. Soc., 76, 563 (1993) Hiroaki Tagawa, “Solid Oxide Fuel Cell and Global Environment”, Agne Jofusha, 1998

  The present invention solves the problem of reaction deterioration when a perovskite oxide having a lanthanoid element at the A site and a cobalt element at the B site is used for the air electrode, and further reduces the thermal expansion coefficient to some extent, The purpose is to improve the low temperature characteristics of the air electrode.

The present invention is a solid oxide fuel cell in which a fuel electrode, a solid electrolyte, and an air electrode are laminated in this order,
An active layer in which the air electrode contains rare earth-doped ceria and perovskite oxide (ABO ₃ ) in a ratio of 10 wt%: 90 wt% to 60 wt%: 40 wt%, and a current collecting layer formed on the active layer And
The active layer is disposed between the current collecting layer and the solid electrolyte;
The perovskite oxide has a lanthanoid element at the A site, a cobalt element at the B site, and a divalent metal element only at the B site, and is a solid oxide fuel cell.

  According to the present invention, it is possible to solve the problem of reaction deterioration when a perovskite oxide having a lanthanoid element at the A site and a cobalt element at the B site is used for the air electrode, and further to reduce the thermal expansion coefficient to some extent. The low temperature characteristics of the SOFC air electrode can be improved.

It is typical sectional drawing which shows the structure at the time of generating electric power with the solid oxide fuel cell produced in the Example. It is a typical perspective view which shows the state of the solid electrolyte in the solid oxide fuel cell of FIG. 1, and the electrode formed on it.

In an air electrode using a perovskite oxide having a lanthanoid element at the A site and a cobalt element at the B site, La, which is an example of a lanthanoid element, takes a trivalent state, but is dissolved in ceria and the like. It does not make a specific compound and the diffusion of La into ceria is very slow. In contrast, Sr added to the A site from the viewpoint of electrical conductivity takes a divalent state and reacts with tetravalent ceria to produce SrCeO ₃ which is a perovskite oxide. This reaction results in loss of the A site and excess of the B site, so that the transition metal at the B site diffuses into ceria, and Sr easily reacts with ceria. The above reaction proceeds at an operating temperature of 800 ° C.

Therefore, in the present invention, an air electrode is formed of a perovskite oxide (ABO ₃ ) having a lanthanoid element at the A site, a cobalt element at the B site, and a divalent metal element only at the B site. By adding a divalent metal element to the B site instead of adding Sr to the A site, the same effect can be expected from the viewpoint of electrical conductivity. In addition, these metal elements diffuse to some extent in ceria, but do not make specific compounds. Furthermore, even if the concentration of the B site is decreased, the A site of ABO ₃ does not change, so the B site does not become excessive. Therefore, the reaction in which the element at the B site decreases is less likely to occur, and the progress of the reaction between ceria and the B site element is hindered. From the above, the reaction between ceria and the transition metal at the B site hardly proceeds.

  As the lanthanoid element at the A site, La is usually used. The B site mainly uses cobalt element, or iron element and cobalt element. And as a bivalent metal element added to B site, a metal element with a small ionic radius is preferable, for example, Ni, Cu, and Mg are suitable.

Such a perovskite oxide is represented by LaFe ₁ -YX Co _Y Ni _X O ₃ (0.05 ≦ X ≦ 0.22, 0.10 ≦ Y ≦ 0.30) in which Ni is added to the B site. Iron-cobalt-nickel-based perovskite oxide, LaFe ₁ -YX Co _Y Cu _X O ₃ (0.05 ≦ X ≦ 0.20, 0.15 ≦ Y ≦ 0.30) with Cu added to the B site ) -Iron _- cobalt-copper perovskite oxide, LaFe _{1 -YX} Co _Y Mg _X O ₃ (0.05 ≦ X ≦ 0.10, 0.15 ≦ Y ≦) with Mg added to the B site iron represented by 0.30) - cobalt - magnesium-based perovskite-type _{oxide, LaCo 1-x Ni X O} 3 (0.05 ≦ X ≦ 0.25) nickel represented - cobalt perovskite oxide Is mentioned.

The air electrode may be formed using only the perovskite oxide, but may be formed of a mixture of the perovskite oxide and a rare earth-added ceria such as Ce _0.9 Gd _0.1 O ₂ (GDC). Good. It is known that rare earth-added ceria, which is also one of solid electrolyte materials, does not easily react with the perovskite oxide, and an inconvenient product is not formed even when exposed to high temperatures during firing. This is because even if La diffuses into ceria, a compound that becomes a nonconductor is not formed. Therefore, by mixing rare earth-doped ceria with a thermal expansion coefficient of 1.2 × 10 ⁻⁵ (1 / K) that is not so large with the perovskite oxide, the thermal expansion coefficient of the mixed layer can be increased according to the amount of the mixture. Can be reduced. The mixing amount and the difference in thermal expansion coefficient show a substantially linear relationship, and the specific gravity of both oxides is almost equal to 7 g / cm ³ , so when the mixing amount is 50 wt%, the thermal expansion coefficient is the same as that of the rare earth added ceria and the above It is an intermediate value with the perovskite oxide. Since the adhesion between the rare earth-added ceria and the solid electrolyte is good, the use of this mixed layer improves the adhesion with the solid electrolyte, and can be expected to suppress peeling due to thermal cycling.

  A larger amount of rare earth-added ceria is advantageous from the viewpoint of thermal expansion coefficient. However, from the viewpoint of electrical conductivity, the mixing amount of the rare earth-added ceria is preferably 60 wt% or less. When it exceeds 60 wt%, the perovskite oxide is divided and isolated by rare earth-doped ceria, and the electric conductivity tends to decrease. From the balance between electrical conductivity and thermal expansion coefficient, the mixing ratio of the rare earth-added ceria and the perovskite oxide is preferably 10 wt%: 90 wt% to 60 wt%: 40 wt%, 30 wt%: 70 wt% to 50 wt%: 50 wt% is more preferable.

  At this time, the air electrode preferably has an active layer containing rare earth-doped ceria and the perovskite oxide in a desired ratio, and a current collecting layer formed on the active layer. That is, by disposing the layer containing the perovskite oxide as an active layer only in a portion close to the solid electrolyte and providing a current collecting layer on which the thermal expansion coefficient is not significantly different from that of the solid electrolyte, there is a mismatch in thermal expansion coefficient. It is possible to minimize the stress generated from the current and suppress the ohmic loss associated with current collection.

  Therefore, the thickness of the active layer is preferably thinner, for example, 1 to 15 μm. Since the particle size of the material forming the active layer is usually 0.5 to 1.5 μm, the lower limit of the thickness of the active layer is usually about 1 μm. Moreover, the thickness which can be apply | coated by the screen printing method etc. is 1 micrometer or more normally. When the thickness of the active layer exceeds 15 μm, peeling at the interface with the solid electrolyte tends to occur due to the stress generated by the difference in TEC. The thickness of the active layer is more preferably 1 to 10 μm, and further preferably 2 to 5 μm.

The current collecting layer is preferably formed of a material whose thermal expansion coefficient is not significantly different from that of the solid electrolyte. Since a zirconia-based solid electrolyte is suitably used as the solid electrolyte, the current expansion coefficient of the current collecting layer is preferably 1.0 to 1.3 × 10 ⁻⁵ (1 / K). For example, the above conditions can be satisfied by forming the current collecting layer with LNF, (LaSr) MnO ₃ (LSM). It can also be formed of the perovskite oxide contained in the active layer. The thickness of the current collecting layer is preferably 20 to 100 μm, and more preferably 30 to 80 μm.

  Note that the coefficient of thermal expansion referred to here is the rate at which the volume of an object expands with an increase in temperature of 1K, and can be measured, for example, with a dilatometer (manufactured by Rigaku Electric Co., Ltd.).

The air electrode having the above-described configuration is laminated in the order of the fuel electrode, the solid electrolyte, the intermediate layer, and the air electrode in the solid electrolyte fuel cell. That is, when a divalent metal element is added to the B site, the stability of the perovskite-based oxide tends to be reduced. When in direct contact with a zirconia-based solid electrolyte, a non-conductor such as La ₂ Zr ₂ O _{7 is used} during firing. In order to form a layer, an intermediate layer is provided between the solid electrolyte and the air electrode. The intermediate layer can be formed of rare earth-doped ceria such as GDC.

  The thickness of the intermediate layer is preferably 1 to 20 μm. When the intermediate layer is less than 1 μm, it is difficult to completely prevent the diffusion of zirconia atoms from the zirconia solid electrolyte. If the intermediate layer is too thick, ohmic loss tends to increase.

  The above-described method using the air electrode having the active layer containing the perovskite oxide and the rare earth-added ceria and the current collecting layer can be expected to have substantially the same effect. This is because the rare earth-added ceria enters between the zirconia-based solid electrolyte and the perovskite oxide and functions in the same manner as the intermediate layer. Therefore, in this case, the intermediate layer is unnecessary, the fuel electrode, the solid electrolyte, and the air electrode are laminated in this order, and the active layer is disposed between the current collecting layer and the solid electrolyte.

  As the fuel electrode and the solid electrolyte, those used in ordinary solid oxide fuel cells can be used. The air electrode as described above is suitable for a solid oxide fuel cell using a rare earth-doped zirconia solid electrolyte or a lanthanum gallate solid electrolyte as the solid electrolyte.

  A solid oxide fuel cell can be configured by electrically connecting a plurality of the solid oxide fuel cells by an interconnector.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. Of the fuel cells produced in the following experiments 1 to 6, cells # 1-0-1 to # 1-0-9, cells # 2-0-1 to # 2-0-5, cell # 3 -0-1 to # 3-0-4, cells # 4-0-1 to # 4-0-5, cells # 5-0-1 to # 5-0-5, and cell # 6-0-1 # 6-0-5 are comparative examples of the present invention, and other cells are examples of the present invention. The average particle size of the powder used was measured by a laser diffraction method or a scanning electron microscope.

<Experiment 1>
First, a 0.2 mm-thick solid electrolyte made of Sc ₂ O ₃ and Al ₂ O ₃ -added zirconia SASZ (0.89ZrO ₂ -0.10Sc ₂ O ₃ -0.01Al ₂ O ₃ ) fired by a doctor blade method On one side of the substrate, NiO-8YSZ (0.92ZrO ₂ -0.08Y ₂ O ₃ ) slurry (8 mol% Y ₂ O ₃ -added zirconia powder having an average particle diameter of about 0.3 μm is 40 wt%, and the average particle diameter is (Approx. 0.8 μm NiO powder is 60 wt%) is applied by screen printing, and a platinum mesh current collector is placed thereon and fired at 1400 ° C. for 8 hours in air, thereby producing a fuel electrode ( A thickness after firing of 60 μm) was formed. Next, Ce _0.9 Gd _0.1 O ₂ (GDC) powder having an average particle size of 0.1 μm serving as an intermediate layer was applied to the back surface of the solid electrolyte substrate by a screen printing method. Next, on the intermediate layer, La _1-X Sr _X Fe _0.80 Co _0.20 O ₃ (X = 0.05, 0.10, 0.15, _0.20, 0.22) having an average particle diameter of 1.0 μm. (LSFC) A slurry of powder is applied by a screen printing method and fired at 1100 ° C. for 2 hours in air, so that an intermediate layer (thickness after firing is 3 μm) and an air electrode (thickness after firing) 60 μm) was formed. Finally, a platinum paste is attached to a mesh current collector made of an iron-chromium heat-resistant alloy (ZMG232), placed on the air electrode, fired in air at 800 ° C. for 2 hours, and then fuel cell (cell # 1- 0-1 to # 1-0-5) were prepared. The fuel electrode and the air electrode have a diameter of 10 mm.

  FIG. 1 shows the structure when power is generated by the obtained fuel cell, and FIG. 2 shows the state of the solid electrolyte and the electrode formed thereon. That is, the fuel electrode 2 and the air electrode 3 are formed at the center of each surface of the solid electrolyte 1. A platinum mesh current collector 4 is disposed on the fuel electrode 2, and an iron-chromium heat-resistant alloy mesh current collector 5 is disposed on the air electrode 3, and a platinum terminal 6 is connected to each. Moreover, in order to isolate | separate and measure the interface resistance value of an air electrode so that it may mention later, the reference electrode 7 is formed in the outer periphery of the solid electrolyte 1, and the platinum terminal is connected similarly. Electric power can be generated by disposing a manifold 9 made of alumina via a gas seal 8 and introducing gas into the fuel electrode 2 and the air electrode 3 respectively.

Next, instead of LSFC, LaFe _0.80-X Co _0.20 Ni _x O ₃ (X = 0.05, 0.10, 0.15, _0.20, 0.22) (LFCN) was used for the air electrode. Cells # 1-1-1 to # 1-1-5 were produced. In cells # 1-1-1 to # 1-1-5, instead of Sr added to the A site in cells # 1-0-1 to # 1-0-5, Ni of the same molar concentration was used. Is added to the B site.

A power generation test was performed using the obtained cell. In this test, room temperature humidified hydrogen gas was used as the fuel electrode side gas, and oxygen was used as the air electrode side gas. In any cell, an open electromotive force of 1.13 V or higher was obtained at 800 ° C. In addition, the interfacial resistance, which is an index of electrode performance, was measured by the AC impedance method. Here, by taking the reference electrode as shown in FIGS. 1 and 2, the interface resistance value of the air electrode was separated and measured. That is, a minute alternating current is applied between the fuel electrode and the air electrode so that a voltage of about 5 mV is applied, and the voltage response appearing between the air electrode and the reference electrode is input to the impedance measuring instrument. The interface resistance value was determined. Here, the atmosphere of the reference electrode was the same oxygen as the air electrode side gas. Note that the interface electrode resistance value at the open electromotive force condition after energization for 24 hours and after energization for 1000 hours was measured with an impedance measuring instrument with a constant current value (200 mA / cm ² ). And the interfacial resistance value was compared and the time-dependent change of the air electrode was evaluated. The results are shown in Table 1. The cells # 1-1-1 to # 1-1-5 had the same initial characteristics and excellent temporal stability compared to the cells # 1-0-1 to # 1-0-5.

Next, the fuel cell (cell # 1-) in which the composition of the air electrode was changed to La _0.80 Sr _0.20 Fe _1-X Co _X O ₃ (X = 0.10, 0.15, 0.25, 0.30). 0-6 to # 1-0-9), and LaFe _0.80-X Co _X Ni _0.20 O ₃ (X = 0.10, 0.15, 0.25, 0.30) # 1-1-6 to # 1-1-9) were produced. Then, a power generation test was performed in the same manner. The results are shown in Table 1. Cells # 1-1-6 to # 1-1-9 had the same initial characteristics and superior temporal stability as compared to cells # 1-0-6 to # 1-0-9.

Next, the fuel cell (cell # 1-2-1 to # 1) in which the composition of the air electrode was changed to LaFe _0.80-X Co _0.20 Cu _X O ₃ (X = 0.05, 0.10, _0.20 ). -2-3), and fuel cells (cells # 1-2-4 to # 1-) changed to LaFe _0.90-X Co _X Cu _0.10 O ₃ (X = 0.15, 0.25, 0.30) 2-6) was produced. Then, a power generation test was performed in the same manner. The results are shown in Table 1. In all cases, the initial characteristics were the same as those of the cells # 1-0-1 to # 1-0-9, and the stability over time was excellent.

Next, the composition of the air electrode _{LaFe 0.80-X Co 0.20 Mg X} O 3 (X = 0.05,0.08,0.10) to change fuel cell (cell # 1-3-1～ # 1 3-3), and fuel cells (cells # 1-2-4 to # 1-) changed to LaFe _0.92-X Co _X Mg _0.08 O ₃ (X = 0.15, 0.25, _0.30 ) 2-6) was produced. Then, a power generation test was performed in the same manner. The results are shown in Table 1. In all cases, the initial characteristics were the same as those of the cells # 1-0-1 to # 1-0-9, and the stability over time was excellent.

<Experiment 2>
The intermediate layer made of GDC in Experiment 1 was not provided, but instead a slurry in which air electrode material and GDC were mixed by 50 wt% was applied by screen printing, and further, the slurry made of air electrode material was applied thereon by screen printing. Thickly applied. As the air electrode material, one having the composition shown in Table 2 was used. The fuel cell (cell #) in which the active layer (thickness after firing is 3 μm) and the current collecting layer (thickness after firing is 30 μm) is formed by firing at 1100 ° C. for 2 hours in air. 2-0-1 to # 2-0-5, cells # 2-1-1 to # 2-1-5, cells # 2-2-1 to # 2-2-3, cell # 2-3-1 To # 2-3-3). Note that cells # 2-0-1 to # 2-0-5 are cells in which an active layer having a composition containing Sr is formed at the A site, and for the portion excluding GDC, cells # 1-0-1 It is the same composition as the air electrode of # 1-0-5.

  A power generation test was performed in the same manner as in Experiment 1 using the obtained cell. The results are shown in Table 2. Cells # 2-1-1 to # 2-1-5, cells # 2-2-1 to # 2-2-3, and cells # 2-3-1 to # 2-3-3 are connected to cell # 2- Compared with 0-1 to # 2-0-5, the initial characteristics were equivalent and the stability over time was excellent.

<Experiment 3>
The mixing ratio of GDC to the active layer in cells # 2-0-4 and # 2-1-4 of Experiment 2 was changed to 10 wt%, 20 wt%, 30 wt%, and 60 wt%, and the active layer and the SASZ solid electrolyte substrate The fuel cells (cells # 3-0-1 to # 3-0-4, cells # 3-1-1 to # 3-1-4) provided with the intermediate layer made of GDC in Experiment 1 are manufactured. did. Note that cells # 3-1-1 to # 3-1-4 have the same molar concentration of Ni instead of Sr added to the A site in cells # 3-0-1 to # 3-0-4. Is added to the B site.

  A power generation test was performed in the same manner as in Experiment 1 using the obtained cell. The results are shown in Table 3. Cells # 3-1-1 to # 2-1-4 had the same initial characteristics and superior temporal stability compared to cells # 3-0-1 to # 2-0-4.

<Experiment 4>
The mixing ratio of GDC into the active layer in Experiment 2 was changed to 30 wt%, an intermediate layer made of GDC in Experiment 1 was provided between the active layer and the SASZ solid electrolyte substrate, and the air electrode material had the composition shown in Table 4 Fuel cells (cells # 4-0-1 to # 4-0-5, cells # 4-1-1 to # 4-1-5, cells # 4-2-1 to # 4-2) -3, cells # 4-3-1 to # 4-3-3) were produced.

  A power generation test was performed in the same manner as in Experiment 1 using the obtained cell. The results are shown in Table 4. Cells # 4-1-1 to # 4-1-5, cells # 4-2-1 to # 4-2-3, and cells # 4-3-1 to # 4-3-3 are connected to cell # 4- Compared with 0-1 to # 4-0-5, the initial characteristics were equivalent and the stability over time was excellent.

<Experiment 5>
The SASZ solid electrolyte substrates in # 4-0-1 to # 4-0-5 and cells # 4-1-1 to # 4-1-5 in Experiment 4 are lanthanum gallate type (La _0.8 Sr _0.2 Ga _0.8 Mg _0.2 O ₃ ) Fuel cell (cell # 5-0-1 to # 5-0-5, cell # 5-1) in which the solid electrolyte substrate was changed and the firing temperature of the fuel electrode was changed to 1250 ° C. -1 to # 5-1-5 were produced.

  A power generation test was performed in the same manner as in Experiment 1 using the obtained cell. The results are shown in Table 5. Cells # 5-1-1 to # 5-1-5 have better characteristics after 1000 hours and are more stable over time than cells # 5-0-1 to # 5-0-5. It was.

<Experiment 6>
The fuel cell (cell # 6-0-1 to cell # 6-0-1) formed by changing the air electrode material in Experiment 4 to one having the composition shown in Table 6 and forming the current collecting layer using a paste containing LiNi _0.60 Fe _0.40 O ₃ powder. # 6-0-5 and cells # 6-1-1 to # 6-1-5) were prepared.

  A power generation test was performed in the same manner as in Experiment 1 using the obtained cell. The results are shown in Table 6. Cells # 6-1-1 to # 6-1-5 were superior in initial characteristics and stability over time as compared to cells # 6-0-1 to # 6-0-5.

  As described above, in a perovskite oxide having a lanthanoid element at the A site and a cobalt element at the B site, Ni is added to the B site instead of adding a divalent metal element having a large ion radius such as Sr to the A site. By adding a divalent metal element having a small ionic radius, such as Cu, Mg, etc., and using it for the air electrode, we succeeded in improving electrical conductivity and reducing reaction deterioration with rare earth-added ceria. The present invention greatly contributes to high reliability and high efficiency of SOFC.

DESCRIPTION OF SYMBOLS 1 Solid electrolyte 2 Fuel electrode 3 Air electrode 4 Iron-chromium heat-resistant alloy mesh current collector 5 Platinum mesh current collector 6 Platinum terminal 7 Reference electrode 8 Gas seal 9 Manifold

Claims (6)

A solid oxide fuel cell in which a fuel electrode, a solid electrolyte, and an air electrode are laminated in this order,
An active layer in which the air electrode contains rare earth-doped ceria and perovskite oxide (ABO ₃ ) in a ratio of 10 wt%: 90 wt% to 60 wt%: 40 wt%, and a current collecting layer formed on the active layer And
The active layer is disposed between the current collecting layer and the solid electrolyte;
A solid oxide fuel cell, wherein the perovskite oxide has a lanthanoid element at the A site, a cobalt element at the B site, and a divalent metal element only at the B site. The perovskite oxide is represented by LaFe ₁ -YX Co _Y Ni _X O ₃ (0.05 ≦ X ≦ 0.22, 0.10 ≦ Y ≦ 0.30). A solid oxide fuel cell as described in 1. The perovskite oxide is represented by LaFe ₁ -YX Co _Y Cu _X O ₃ (0.05 ≦ X ≦ 0.20, 0.15 ≦ Y ≦ 0.30). A solid oxide fuel cell as described in 1. The perovskite oxide is represented by LaFe _{1 -YX} Co _Y Mg _X O ₃ (0.05 ≦ X ≦ 0.10, 0.15 ≦ Y. ≦ 0.30). 2. The solid oxide fuel cell according to 1. 2. The solid oxide fuel cell according to claim 1, wherein the perovskite oxide is represented by LaCo _1-x Ni _x O ₃ (0.05 ≦ X ≦ 0.25).   6. The solid electrolyte fuel cell according to claim 1, wherein the solid electrolyte is a rare earth-added zirconia-based solid electrolyte or a lanthanum gallate-based solid electrolyte.

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