JP2012198990A - Electrode material and fuel battery cell including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel electrode material that can be used at high temperature atmosphere, a fuel battery cell manufactured utilizing the electrode material, and a method for manufacturing the fuel battery cell.SOLUTION: The novel electrode material contains a component expressed by LaANiCuFeBO(where, A and B independently represent at least one element selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La, and x>0, y>0, x+y+z<1, 0≤s≤0.05 and 0≤z≤0.05 are satisfied). The material exhibits relatively high conductivity at high temperature, and has the advantage of combination with other materials in relation to coefficient of thermal expansion.

Description

  The present invention relates to an electrode material and a fuel cell including the same.

  A solid oxide fuel cell (SOFC) has a plurality of cells including a fuel electrode, an electrolyte layer, an air electrode, and a current collecting layer. In SOFC, cells are stacked via separators and interconnectors. The current collecting layer is provided in order to reduce electrical resistance in connection between the air electrode and the separator or the interconnector.

The SOFC described in Patent Document 1 has a connection layer disposed between the air electrode and the separator. In Patent Document 1, Pt paste and conductive metal oxide powder are cited as materials for the connection layer. Patent Document 1, as the conductive metal oxide _{powder, LaNi 1-x Fe x O} 3, La 1-x Sr x CoO 3 , etc. are mentioned.

Patent Document 2, as an air electrode _{material, LaNi 1-x Fe x O} 3 are cited.

JP 2009-277411 A Japanese Patent No. 3414657

  Since Pt is expensive, it is not suitable as a general-purpose material.

Also, if using the _{La 1-x} Sr x CoO ₃ as the current collector layer material, the thermal expansion coefficient of the current collecting layer material (thermal expansion coefficient) is 18~20ppm / K, for example, the air electrode material is La ₁ If a _{-y Sr y Co 1-z Fe} z O 3, much larger than the thermal expansion coefficient 12.5 ppm / K of cathode material. As described above, when the difference in coefficient of thermal expansion between the air electrode material and the current collecting layer material is large, problems such as separation of the current collecting layer from the air electrode and generation of cracks in the current collecting layer occur.

LaNi _1-x Fe _x O ₃ has a thermal expansion coefficient of about 13.4 to 9.8 ppm / K, but has a low conductivity of 700 S / cm or less in the atmosphere and 600 to 1000 ° C. Therefore, a new electrode material that can be used in a high-temperature atmosphere is demanded.

  An object of the present invention is to provide a material suitable for both the thermal expansion coefficient and the conductivity as a material that can be used for an electrode of a fuel cell or the like.

Electrode material according to the first aspect of the present _{invention, La 1-s A s Ni} 1-x-y-z Cu x Fe y B z O 3-δ ( However, A and B are each independently an alkali It is at least one element selected from the group consisting of earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La, and x> 0, y> 0, x + y + z <1, 0 ≦ s ≦ 0.05 and 0 ≦ z ≦ 0.05).

  According to this electrode material, the coefficient of thermal expansion can be kept relatively small, and high conductivity can be obtained even at high temperatures.

  This electrode material is suitable as an electrode material for fuel cells, and particularly suitable as a material for the current collecting layer. Since this electrode material has high conductivity, when applied to the current collecting layer, the electrical resistance in the connection between the air electrode and the separator or interconnector can be reduced. In addition, since the difference in the coefficient of thermal expansion between the air electrode and the current collecting layer is kept small, peeling or cracking is unlikely to occur between the air electrode and the current collecting layer.

  The electrode material according to the present invention exhibits conductivity and a coefficient of thermal expansion suitable as a material that can be used for an electrode used at high temperature and in the atmosphere.

It is sectional drawing of an example of a fuel cell. It is an XRD result of the sample obtained in Example E1. It is a composition figure of Examples E1-E12 and Comparative Examples A1-A6, and the thermal expansion coefficient of the sample in each example and the electrical conductivity in 750 degreeC are shown collectively in the figure. It is a composition figure of Examples F1-F9 and Comparative Examples D1-D6, and the thermal expansion coefficient of the sample in each example and the electrical conductivity in 750 degreeC are shown collectively in the figure.

<1. Electrode material>
Electrode material of the present _invention contains a component represented by _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ.

  However, A and B are each independently at least one element selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La, s, x, y, and z satisfy x> 0, y> 0, x + y + z <1, 0 ≦ s ≦ 0.05, and 0 ≦ z ≦ 0.05. Examples of alkaline earth metal elements include Ca and Sr. Examples of the transition metal element include Sc, Ti, Cr, Mn, Co, Y, Zr and the like. Examples of rare earth elements include Ce, Pr, Gd and the like.

  A is at least one element selected from the group consisting of alkaline earth metal elements and rare earth elements excluding La, and B is at least one element selected from transition metal elements excluding Fe, Ni, and Cu. It may be a seed element.

The electrode _material as _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ other than compounds may contain elements A and / or B. At that time, the ratio of A, B, La, Ni, Cu and Fe in the electrode material is La: A: Ni: Cu: Fe: B = 1-s: s: 1-xyz: x : Y: z, and when s, z, x, and y satisfy the ranges described in this specification, good conductivity and thermal expansion coefficient are realized.

  This material can achieve both high conductivity and low coefficient of thermal expansion. Specifically, the electrical conductivity of the material when fired in an oxygen atmosphere may be 800 S / cm or more, 850 S / cm or more, or 880 S / cm or more at 750 ° C. May be. The coefficient of thermal expansion of the material when fired in an oxygen atmosphere may be 14.0 or less, or 13.5 ppm / K or less. Further, when baked in an air atmosphere, the conductivity of this material at 750 ° C. may be 800 S / cm or more, 850 S / cm or more, or 880 S / cm or more. . Further, the coefficient of thermal expansion of the material when fired in an air atmosphere is preferably 14.5 ppm / K or less.

  In order to realize such conductivity and coefficient of thermal expansion, x ≧ 0.05, x ≦ 0.5, 0.05 ≦ x ≦ 0.5 may be satisfied. It may be 0.1 ≦ x ≦ 0.5. Further, y ≧ 0.03, y ≦ 0.3, 0.03 ≦ y ≦ 0.3, or 0.03 ≦ y ≦ 0.2 may be satisfied. May be. Further, δ ≦ 0.4 is preferable, δ ≧ 0.0 is preferable, and 0.0 ≦ δ ≦ 0.4 is more preferable.

  When x ≧ 0.05, higher conductivity can be obtained. When x ≦ 0.5, higher conductivity can be obtained.

  Moreover, it is y> = 0.03, and a thermal expansion coefficient is restrained low. When y ≦ 0.3, high conductivity can be obtained.

  Further, when δ ≦ 0.4, higher conductivity can be obtained. Although δ <0.0 may be sufficient, it is more preferable that δ ≧ 0.0 because it is necessary to increase the oxygen partial pressure at the time of production and cost is increased.

  Moreover, favorable electrical conductivity and a thermal expansion coefficient are implement | achieved because s and z are the above-mentioned ranges. Furthermore, at least one of s> 0 and z> 0 may be satisfied, at least one of s ≧ 0.005 and z ≧ 0.005 may be satisfied, or s ≧ 0.01 and z ≧ At least one of 0.01 may be satisfied.

  Since it has both a high conductivity and a low coefficient of thermal expansion, this material is suitable as a material used for fuel cells, and particularly as a material for forming electrodes of fuel cells. The “electrode” is a concept including a current collecting layer as well as an air electrode and a fuel electrode.

  Further, this material does not contain an expensive raw material such as Pt as an essential component. Therefore, it can be used as an inexpensive electrode material.

  Further, the crystal phase of this material preferably contains a perovskite crystal phase, and is preferably a perovskite single phase. This achieves higher conductivity.

Usually, all the Ni in LaNiO ₃ is trivalent. However, some Ni may be divalent. The heterogeneous phase derived from divalent Ni is represented by the general formula La _{n + 1} Ni _n O _{3n + 1} (where n is 1, 2 or 3). For example, if n = 3, the heterogeneous phase is represented by La ₄ Ni ₃ O ₁₀ and includes 4 La ³⁺ +2 Ni ³⁺ +1 Ni ²⁺ . Higher conductivity can be obtained when there is no heterogeneous phase in the electrode material or when the abundance ratio is smaller. The heterogeneous phase shows a peak at 31.2 ° to 32.3 ° in XRD (X-ray diffraction). Therefore, it is preferable for realizing high conductivity that the peak at this position is not observed or the peak is small.

Since x> 0 and y> 0, LaNiO ₃ is simultaneously substituted with Cu and Fe in the electrode material. By this simultaneous substitution, both high conductivity and low coefficient of thermal expansion are compatible, so that further element addition is permitted. Further, the conductivity and the thermal expansion coefficient can be further controlled by the amount of the element added. In addition, when this electrode material is applied to an electrode of a fuel cell, the element contained in the layer in contact with the electrode material layer is contained in the electrode material layer, so that the interface interface between the layers is improved.

When applied to the air electrode, the electrode material may be mixed with rare earth doped ceria such as Ce _0.9 Gd _0.1 O ₂ (GDC). It is known that rare earth-added ceria, which is also one of solid electrolyte materials, hardly reacts with perovskite-based oxides, and a high-resistance compound is not formed even when exposed to high temperatures during firing. By mixing rare earth-doped ceria having a thermal expansion coefficient of not so large of 12 ppm / K with LaNi _1-xy Cu _x Fe _y O _{3 -δ} , the thermal expansion coefficient of the mixed layer can be increased according to the amount of the mixture. Further reduction can be achieved. Since the adhesion between the rare earth-added ceria and the solid electrolyte is good, it can be expected that by using this mixed layer, the adhesion with the solid electrolyte is improved and the effect of suppressing peeling due to thermal cycling is increased.

<2. Fuel cell>
<1. The material in the> column is used for forming the electrode. Hereinafter, a fuel cell in which this material is used as a current collecting layer will be described.

  The fuel cell according to the present embodiment includes the fuel cell 1 shown in FIG. 1 (hereinafter simply referred to as “cell”) and an interconnector (not shown). The plurality of cells 1 are stacked, and the interconnector is disposed between the cells 1. The cells 1 are electrically connected to each other by an interconnector.

  The cell 1 is a ceramic thin plate having a thickness of about 0.5 to 5 mm. As shown in FIG. 1, the fuel cell 1 according to this embodiment includes a fuel electrode 11, an electrolyte layer (solid electrolyte layer) 12, an air electrode 13, and a current collection layer 14.

  Examples of the material of the fuel electrode 11 include NiO-YSZ. Specifically, the thickness of the fuel electrode 11 is about 0.5 to 5 mm. The fuel electrode 11 containing NiO acquires conductivity by being subjected to a reduction process.

  The electrolyte layer 12 is provided between the air electrode 13 and the fuel electrode 11. Examples of the material of the electrolyte layer 12 include ceria-based materials composed of ceria and rare earth elements dissolved in ceria. Examples of the ceria-based material include GDC (gadonium doped ceria), SDC (samarium doped ceria), and the like. The rare earth element concentration in the ceria-based material is preferably 5 to 20 mol%. Rare earth stabilized zirconia is also conceivable.

  Moreover, the thickness of the electrolyte layer 12 is 20 micrometers or less, for example.

  Examples of the material of the air electrode 13 include LSCF (lanthanum strontium cobalt ferrite). The thickness of the air electrode 13 is, for example, about 5 to 50 μm.

  The current collecting layer 14 includes the electrode material described above. The thickness of the current collection layer 14 is, for example, about 5 to 200 μm. The current collecting layer 14 is produced, for example, by firing a molded body obtained by pressure-bonding the above-described electrode material processed into a sheet shape onto the air electrode 13.

  The cell 1 may further include components such as other layers, and the shape, material, dimensions, and the like of each component can be changed.

<3. Method for producing electrode material>
<1. The manufacturing method of the electrode material in the column> includes La, Ni, Cu and Fe, and the molar ratio of La, Ni, Cu and Fe is La: Ni: Cu: Fe = 1: (1-xy): x : The raw material which is y may be baked at the temperature of 1200 degrees C or less (baking process). This manufacturing method may include preparing a raw material containing La, Ni, Cu, and Fe in this ratio.

In the firing step, the molded body of the mixture containing La, Ni, Cu and Fe in the above ratio and the layer containing element A and / or element B can be fired adjacent to each other. This can by diffusing an element A and / or the element B in the fired body _to obtain a _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ.

The layer containing the element A and / or the element B may be a SOFC solid electrolyte, an air electrode, an interconnector, or the like. In particular, alkaline earth metal _{elements, La 1-x Sr x CoO} 3 and _{La 1-x Sr x Co 1} -y Fe y O 3 or the like of the air electrode _material, La _1-x Ca _x interconnector material of CrO or the like include. The rare earth elements are contained in electrolyte materials such as air electrode materials, interconnector materials, and GDC (gadolinium doped ceria). Transition metal elements are included in air electrode materials, interconnector materials, electrolyte materials such as YSZ (yttria stabilized zirconia), and fuel electrode materials.

  In addition, the above <1. The manufacturing method of the electrode material in the column> La, Ni, Cu, Fe, element A and element B, La: Ni: Cu: Fe: A: B = 1-s: (1-xys) It may include a firing step of firing the raw material containing at a molar ratio of: x: y: s: z at a temperature of 1200 ° C. or lower.

  The raw material used in the firing step may be obtained by mixing the above-described metal oxide powder and / or hydroxide powder, or a coprecipitation method or liquid using a metal alkoxide or metal nitrate as a starting material. It may be obtained by a phase synthesis method.

  The preferred ranges of x, y and δ are as described above. That is, the raw material has a molar ratio of La, Ni, Cu and Fe of La: Ni: Cu: Fe = 0.95 to 1: 0.15 to 0.92: 0.05 to 0.5: 0.03. It is preferable to prepare so that it may become 0.3. The range of s and z is also as described above. Ni and Cu are likely to be reduced in the air and at high temperatures. Therefore, in the production of this substance, in order to adjust δ to a suitable range, the firing step is preferably performed at 1200 ° C. or lower, and the firing step is more preferably performed in an oxygen atmosphere and at 1200 ° C. or lower. preferable.

  Moreover, a baking process may be regarded as one process and may include the 2 or more heat processing from which temperature conditions differ. In at least one of these processes, the above-mentioned raw material may be heat-treated at a temperature of 1100 ° C. or higher. The firing step may include a heat treatment in which the temperature condition is set to less than 1100 ° C. In any heat treatment, the temperature condition can be set to 1200 ° C. or less. Fe has a relatively low reactivity, but a single-phase perovskite structure is easily obtained by heat-treating the raw material at 1100 ° C. or higher.

  Moreover, the calcining process of calcining the raw material at 1100 ° C. or higher may be performed before the calcining process. When the calcination treatment is performed, the temperature in the firing step may be less than 1100 ° C. Further, the calcination step may be performed at 1200 ° C. or less.

  In addition, when baking the raw material containing element A and B, also when baking the raw material containing element A and B adjacent to the raw material containing La, Ni, Cu, and Fe, a baking process and calcination The temperature conditions of the process are as described above.

  However, depending on the particle size of the raw material and other conditions, the temperature condition of firing, the time taken for firing, and the like are changed.

[Preparation of sample and measurement of properties]
i. Examples E1-E12 (oxygen atmosphere firing)
In LaNiO _{3 -δ} , simultaneous substitution using Fe and Cu was performed. The characteristics of the obtained samples were examined by changing the ratio of Cu element and Fe element.

(I-1) Preparation of Sample After drying lanthanum hydroxide, nickel oxide, copper oxide, and iron oxide powder at 110 ° C. for 12 hours, they were weighed at a predetermined molar ratio shown in Table 1.

  These were wet mixed in an aqueous medium and then dried. Then, mixed powder was produced by passing through a sieve.

  Next, after the mixed powder is put in an alumina crucible with a lid, a solid phase reaction is performed by heat treatment in an oxygen atmosphere and at a predetermined calcining temperature shown in Table 1 for each of the perovskite phase calcined powders. Obtained. The XRD of the calcined powder in Example 1 is shown in FIG.

  After calcining the calcined powder and performing uniaxial pressing, a molded body was obtained by CIP (Cold Isostatic Press).

  Next, after allowing the molded body to stand in an alumina sheath with a lid, a fired body was obtained by heat treatment in an oxygen atmosphere and at a predetermined firing temperature shown in Table 1 for 12 hours (Examples E1 to E12).

(I-2) Measurement of characteristics (Density)
The density of the fired body was calculated from the dimensions and density. The results were as shown in Table 1.

(conductivity)
A test piece of 3 × 4 × 40 mm was cut out from the fired body, and the electrical conductivity of the fired body at 600 to 900 ° C. was measured in the air by a direct current four-terminal method. The electrical conductivity depends not only on the composition ratio of the fired body but also on the density. Based on the equation of Meredith et al., Reference to “Resources and Materials” vol119, No1, p1-8 (2003) by Goro Yamada. The portion depending on the density of the measured value was corrected by the following formula (1) derived as described above.
Formula (1): λe = ((2 + 0.5φv) × (2-0.5φv)) / ((2-φv) × (2-2φv)) × λc
Measured value = λc,
Conductivity after correction = λe,
(1-density) = φv
The corrected conductivity was as shown in Table 1.

(Coefficient of thermal expansion)
A test piece of 3 × 4 × 20 mm was cut out from the fired body, and the thermal expansion coefficient of the fired body at 40 to 1000 ° C. was measured in the air using a thermal expansion coefficient measuring device. The results were as shown in Table 1.

(Oxygen non-stoichiometric amount)
In some examples, a part of the fired body was pulverized in a mortar and subjected to chemical analysis. The molar ratio of the constituent elements and the oxygen nonstoichiometric amount δ were calculated from the weight ratio of the obtained elements. The results were as shown in Table 7.

ii. Comparative Examples A1 to A6
LaNiO _{3 -δ was} substituted with Fe or Cu and baked in an oxygen atmosphere. That is, the ratio of Cu element and Fe element was set so that x or y would be 0 (zero), unlike the example.

  Specifically, the above-mentioned i., Except that the raw material ratio and other conditions were as shown in Table 2. The same operation as in the column (oxygen atmosphere) was performed to obtain a sample, and its characteristics were measured. The results are shown in Table 2.

iii. Comparative examples B1-B3
In the following comparative examples, a fired body was obtained using Co (cobalt) and Fe in simultaneous substitution. In this comparative example, the composition of the sample is represented by LaNi _1-ab Fe _a Co _b O _{3 -δ} .

  Specifically, the above-mentioned i., Except that lanthanum hydroxide, nickel oxide, cobalt oxide and iron oxide powder were used as raw materials and the raw material ratio and other conditions were as shown in Table 3. By the same operation as the column (oxygen atmosphere firing), a sample was obtained and its characteristics were measured. The results are shown in Table 3.

iv. Comparative Examples C1-C4
In the following comparative examples, fired bodies were obtained using Sr (strontium) and Fe, which are alkaline earth metal elements, in simultaneous substitution. The composition of the resulting fired body _is represented by _{La 1-c Sr c Ni 1} -a-b Fe a Co b O 3-δ.

  Specifically, the above-mentioned i., Except that lanthanum hydroxide, strontium carbonate, nickel oxide, cobalt oxide and iron oxide powder were used and the raw material ratio and other conditions were as shown in Table 4. By the same operation as the column (oxygen atmosphere firing), a sample was obtained and its characteristics were measured. The results are shown in Table 4.

v. Examples F1 to F9 (air atmosphere firing)
Using lanthanum hydroxide, nickel oxide, copper oxide, and iron oxide powder, the raw material ratio and other conditions were as shown in Table 5, and a sample was obtained and its characteristics were measured. In particular, in these examples, firing was performed by heat treatment in an air atmosphere at a predetermined firing temperature shown in Table 5 for 1 hour. Except for the conditions shown in Table 5, i. The same operation as in column (oxygen atmosphere firing) was performed. The results are shown in Table 5.

vi. Comparative Examples D1-D6
Similarly to Examples F1 to F9, LaNiO _{3 -δ was} subjected to simultaneous substitution using Fe and Cu and baked in the air atmosphere. Unlike the examples, the ratio of Cu element and Fe element was set so that x or y was 0 (zero). Specifically, the above-mentioned i., Except that the raw material ratio and other conditions were as shown in Table 6. The same operation as in the column (oxygen atmosphere firing) was performed to obtain a sample, and the characteristics thereof were measured. The results are shown in Table 6.

vii. Examples G1-G3
(Example G1)
A calcined powder was obtained by the operation of Example E1. After pulverizing the calcined powder, uniaxial press molding was performed at 200 kgf / cm ² to obtain a molded body. The molded body was allowed to stand in an alumina sheath with a lid and heat-treated at 1000 ° C. for 12 hours in an air atmosphere to obtain a fired body.

(Examples G2 and G3)
A fired body was obtained by the same operation as in Example G1 except that powders of lanthanum hydroxide, nickel oxide, copper oxide, iron oxide, and cobalt oxide were used as raw materials in the ratios shown in Table 8.

  About the obtained sintered body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 8.

viii. Examples H1-H5
(Example H1)
A calcined powder was obtained by the same operation as in Example G1, except that lanthanum hydroxide, nickel oxide, copper oxide, iron oxide, and zirconium oxide powders were used as raw materials in the ratios shown in Table 9. After the calcined powder was pulverized, terpineol as a solvent and ethyl cellulose as a binder were added and mixed to obtain a paste. A layer was formed by printing on a YSZ fired body, which is one type of SOFC electrolyte layer material, using a paste. The laminated body thus obtained was dried and heat-treated at 1000 ° C. for 1 hour in the air to obtain a laminated fired body.

  About the obtained laminated fired body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 9.

(Example H2)
A calcined powder was obtained by the same operation as in Example G1, except that lanthanum hydroxide, nickel oxide, copper oxide, iron oxide, and manganese oxide powders were used as raw materials in the ratios shown in Table 9. A paste was obtained from the calcined powder in the same manner as in Example H1. A layer was formed by printing on a LaSrMnO ₃ fired body, which is one of SOFC air electrode materials, using a paste. The laminated body thus obtained was dried and heat-treated in the same manner as in Example H1 to obtain a laminated fired body.

  About the obtained laminated fired body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 9.

However, the conductivity was obtained as follows. Both the LaSrMnO ₃ fired body as the substrate and the layer formed by printing (hereinafter referred to as “LaNiCuFeO ₃ layer”) have conductivity. Therefore, first, the conductivity of the entire laminated fired body is determined by the above i. Obtained in the same manner as the column. The conductivity, assuming a conductivity obtained for the parallel resistance of LaSrMnO ₃ and LaNiCuFeO ₃ layer formed by printing, and conductivity of the whole laminated fired body, LaSrMnO ₃ single conductive which is separately measured From the rate, the conductivity of the LaNiCuFeO ₃ layer was calculated.

(Example H3)
A calcined powder was obtained in the same manner as in Example G1, except that lanthanum oxide, nickel oxide, copper oxide, iron oxide, and gadolinium powder were used as raw materials in the ratios shown in Table 9. A paste was obtained from the calcined powder in the same manner as in Example H1. Using the paste, a layer was formed by printing on a GDC fired body, which is one of SOFC electrolyte materials. The laminated body thus obtained was dried and heat-treated in the same manner as in Example H1 to obtain a laminated fired body.

  About the obtained laminated fired body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 9.

(Example H4)
A calcined powder was obtained in the same manner as in Example G1 except that powders of lanthanum oxide, nickel oxide, copper oxide, iron oxide, and calcium carbonate were used in the ratios shown in Table 9. After pulverizing the calcined powder, a paste was obtained from the calcined powder in the same manner as in Example H1. Using the paste, a layer was formed by printing on a LaCaCrO ₃ fired body, which is one type of SOFC interconnector material. The laminated body thus obtained was dried and heat-treated in the same manner as in Example H1 to obtain a laminated fired body.

About the obtained laminated fired body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 9. However, since the LaCaCrO ₃ fired body, which is the substrate, also has conductivity, the measurement of conductivity was performed in the same manner as in Example H2.

(Example H5)
A calcined powder was obtained in the same manner as in Example G1, except that powders of lanthanum hydroxide, nickel oxide, copper oxide, iron oxide, strontium carbonate, and zirconium oxide were used in the ratios shown in Table 9. A paste was obtained from the calcined powder in the same manner as in Example H1. A layer was formed by printing on the LaSrCoFeO ₃ fired body, which is the SOFC air electrode material, using the paste. The laminated body thus obtained was dried and heat-treated in the same manner as in Example H1 to obtain a laminated fired body.

About the obtained laminated fired body, the above i. The characteristics were measured by the same operation as in the column. The results are shown in Table 9. However, since the LaSrCoFeO ₃ fired body as the substrate also has conductivity, the measurement of conductivity was performed in the same manner as in Example H2.

[result]
As shown in FIG. 2, the crystal phase of the fired body of Example E1 was a perovskite single phase. Moreover, although not shown in figure, also in any Example E1-E12 and F1-F9, Comparative example A1-A6, B1-B3, C1-C4, and D1-D6, the crystal phase was a perovskite single phase.

  As shown in Table 1, in Examples E1 to E12 fired in an oxygen atmosphere, a relatively large conductivity of 680 S / cm or more was obtained even at a high temperature of 900 ° C., and in particular, a conductivity of 800 S / cm or more was obtained at 750 ° C. The rate was realized. In Examples E1 to E12, a coefficient of thermal expansion of 13.5 ppm / K or less, particularly 13.4 ppm / K or less was realized.

  Next, the results of Comparative Examples A1 to A6, B1 to B3, and C1 to C4 are referred to (Tables 2 to 4). These comparative examples were fired in an oxygen atmosphere as in Examples E1 to E12. However, unlike Examples E1-E12, Comparative Examples A1-A6 are single substitutions of Cu or Fe, and no simultaneous substitution of Cu and Fe.

As shown in Table 2, LaNiO _3-δ containing neither Cu nor Fe had low conductivity and a high coefficient of thermal expansion (Comparative Example A1).

  Moreover, according to Cu substitution alone (Comparative Examples A4 to A6, FIG. 3), as shown in Table 2, a relatively high conductivity was obtained at 0.05 ≦ x ≦ 0.2, but the coefficient of thermal expansion was it was high. Further, at x = 0.5, the conductivity was remarkably small and the thermal expansion coefficient was further increased. The cause of this decrease in conductivity is that oxygen escapes from the sample, the mobility of the carrier decreases, and a lot of Cu becomes divalent due to the loss of oxygen in the sample. It is considered that the carrier concentration has decreased. The reason why the coefficient of thermal expansion has increased is considered to be that oxygen escaped at a high temperature and the volume increased.

  According to Fe substitution alone (Comparative Examples A2 to A3, FIG. 3), as shown in Table 2, the thermal expansion coefficient was kept low when 0.3 ≦ y ≦ 0.5. However, the greater the amount of substitution, the lower the conductivity. This decrease in conductivity is thought to be due to a decrease in carrier concentration due to the absence of Cu only by Fe substitution, or a decrease in carrier mobility, or both.

  As shown in Table 3, with the simultaneous substitution of Fe and Co (Comparative Examples B1 to B3), almost no improvement in conductivity was observed. Moreover, in these comparative examples, the coefficient of thermal expansion was large, and favorable characteristics as an electrode material were not obtained.

  As shown in Table 4, in the simultaneous substitution of Sr, Fe, and Co (Comparative Examples C1 to C4), the electrical conductivity was very low and the thermal expansion coefficient was high.

  As described above, in Examples E1 to E12 fired in an oxygen atmosphere, single substitution of Fe or Cu (Comparative Examples A1 to A6), Fe and Co (Comparative Examples B1 to B3), Fe, Co, and Compared with simultaneous replacement with Sr (Comparative Examples C1 to C4), a substance suitable as an electrode material in terms of both conductivity and thermal expansion coefficient could be obtained.

  Next, a sample fired in an air atmosphere will be examined.

  As shown in Table 5, in Examples F1 to F9 fired in the air atmosphere, a relatively large conductivity of 680 S / cm or more was obtained even at a high temperature of 900 ° C., and in particular, a conductivity of 800 S / cm or more was obtained at 750 ° C. The rate was realized. Further, in Examples F1 to F9, the thermal expansion coefficient was 14.5 ppm / K or less, particularly 14.4 ppm / K or less.

On the other hand, as shown in Table 6, the conductivity of LaNiO _{3 -δ} containing neither Cu nor Fe was reduced by firing in an air atmosphere (Comparative Example D1).

  Further, according to Cu substitution alone (Comparative Examples D4 to D6, FIG. 4), as shown in Table 6, the conductivity was significantly lowered when fired in the air atmosphere. This decrease in conductivity is considered to be due to the fact that the sample oxygen escapes during firing because Fe is not contained, and the carrier concentration and carrier mobility are reduced.

  It should be noted that Examples F1 to F9 baked in the atmosphere have conductivity or Fe or Co (Comparative Examples B1 to B3) and even if compared with simultaneous replacement with Fe, Co and Sr (Comparative Examples C1 to C4). It exhibited excellent characteristics as an electrode material in terms of both thermal expansion coefficient, conductivity and thermal expansion coefficient.

As is apparent from the above description, the composition is _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ material (Example E1 to E12, F1 to F9, G1 to G3, H1 to H5) showed good characteristics as electrode materials used in fuel cells. That is, by the simultaneous replacement with Cu and Fe, favorable characteristics as an electrode material of a fuel cell were obtained in both thermal expansion coefficient and conductivity.

  The reason why such excellent characteristics are obtained will be discussed.

_Perhaps, the _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ, the carrier concentration by the Ni is replaced with a more electronic-rich trivalent Cu increases, It is thought that the conductivity is improved.

In general, it is considered that it is difficult to sufficiently increase the carrier concentration by simply substituting with Cu because oxygen in the sample is released in a high temperature atmosphere and Cu becomes divalent. However, since the Gibbs energy of Fe substituted at the same time is lower than the Gibbs energy of Ni or Cu, it is considered that simultaneous substitution with Fe suppresses the escape of oxygen from the sample. _Therefore, in _{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ is considered to be possible to replace more trivalent Cu and Ni.

  In general, in an electrode material having a perovskite-type crystal structure, electrons move through oxygen. Therefore, there is a concern that if a defect is generated when oxygen is released, the mobility of carriers decreases. . In the material system of the examples, the mobility of carriers is probably maintained by suppressing the escape of oxygen by simultaneous substitution of Fe, so that oxygen escapes particularly in the atmosphere and at high temperatures. It is considered that the decrease in conductivity under easy conditions is suppressed.

  A material having a perovskite crystal structure is expected to expand in volume due to an increase in the distance between atoms constituting the material when oxygen deficiency is generated. In the material system of the examples, the result of reducing the amount of oxygen entering / exiting between the sample and the outside world is probably due to the suppression of oxygen release under high-temperature conditions, particularly in the atmosphere where oxygen easily escapes, It is thought that the coefficient of thermal expansion decreases.

  In addition, it is considered that as δ representing the oxygen non-stoichiometric amount is smaller, trivalent Cu is generated, thereby increasing the carrier concentration and increasing the conductivity. In addition, it is considered that the mobility of carriers in the sample increases and the conductivity increases as the crystal becomes closer to a perfect crystal without the defects of the atoms constituting the perovskite.

DESCRIPTION OF SYMBOLS 1 Fuel cell 11 Fuel electrode 12 Electrolyte layer 13 Air electrode

Electrode material according to the first aspect of the present invention, the fuel electrode of the fuel cell, an electrode material of the air electrode or collector _{layer, La 1-s A s Ni} 1-xyz Cu x Fe y B z O 3- _δ (where A and B are each independently at least one element selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La) Yes, x> 0, y> 0, x + y + z <1, 0.0 ≦ δ ≦ 0.4, 0 ≦ s ≦ 0.05, and 0 ≦ z ≦ 0.05, provided that s> 0 and z> 0 satisfying at least one.) contains a component represented by, for have a perovskite-type crystal phase.

<1. Electrode material>
Electrode material of the present invention, the fuel electrode of the fuel cell, an electrode material of the air electrode or collector layer, represented by _{La 1-s A s Ni 1} -xyz Cu x Fe y B z O 3-δ It contains components, which have a perovskite-type crystal phase.

However, A and B are each independently at least one element selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La, s, x, y, z and δ are x> 0, y> 0, x + y + z <1, 0.0 ≦ δ ≦ 0.4, 0 ≦ s ≦ 0.05 and 0 ≦ z ≦ 0.05 . . However, at least one of s> 0 and z> 0 is satisfied. Examples of alkaline earth metal elements include Ca and Sr. Examples of the transition metal element include Sc, Ti, Cr, Mn, Co, Y, Zr and the like. Examples of rare earth elements include Ce, Pr, Gd and the like.

In order to realize such conductivity and coefficient of thermal expansion, x ≧ 0.05, x ≦ 0.5, 0.05 ≦ x ≦ 0.5 may be satisfied. It may be 0.1 ≦ x ≦ 0.5. Further, y ≧ 0.03, y ≦ 0.3, 0.03 ≦ y ≦ 0.3, or 0.03 ≦ y ≦ 0.2 may be satisfied. May be. Also , 0 . 0 ≦ [delta] ≦ Ru 0.4 der.

Further, it is [delta] ≦ 0.4, high Ishirube conductivity is obtained. The [delta] <0.0, because it is expensive should the oxygen partial pressure at the time of producing the high pressure, Ru [delta] ≧ 0.0 der.

Moreover, favorable electrical conductivity and a thermal expansion coefficient are implement | achieved because s and z are the above-mentioned ranges. Furthermore , at least one of s ≧ 0.005 and z ≧ 0.005 may be satisfied, or at least one of s ≧ 0.01 and z ≧ 0.01 may be satisfied.

The crystal phase of this material contains a perovskite-type crystal phase is preferably a perovskite single phase. This achieves higher conductivity.

An electrode material according to a first aspect of the present invention is an electrode material of a fuel electrode, an air electrode, or a current collecting layer of a fuel cell, and has a perovskite-type crystal phase La _{1- s As} Ni _1-xyz Cu _x Fe _y B _z O ₃ -δ (where A and B are each independently selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La) At least one element, x> 0, y> 0, x + y + z <1, 0.0 ≦ δ ≦ 0.4, 0 ≦ s ≦ 0.05, and 0 ≦ z ≦ 0.05, provided that s> 0 and z> 0 for satisfying at least one.) that Yusuke contains a component represented by.

<1. Electrode material>
The electrode material of the present invention is an electrode material of a fuel electrode, an air electrode, or a current collecting layer of a fuel cell, and has La _{1- s As} Ni _1-xyz Cu _x Fe _y B _z O ₃ having a perovskite crystal phase. _- a component represented by δ that Yusuke free.

Claims (12)

_{La 1-s A s Ni 1} -x-y-z Cu x Fe y B z O 3-δ
(However, A and B are each independently at least one element selected from the group consisting of alkaline earth metal elements, transition metal elements excluding Fe, Ni and Cu, and rare earth elements excluding La. X> 0, y> 0, x + y + z <1, 0 ≦ s ≦ 0.05, 0 ≦ z ≦ 0.05)
The electrode material containing the component represented by these. A is at least one element selected from the group consisting of alkaline earth metal elements and rare earth elements excluding La;
B is at least one element selected from transition metal elements other than Fe, Ni, and Cu.
The electrode material according to claim 1.   The electrode material according to claim 1, which has a perovskite crystal phase.   The electrode material according to claim 1, wherein x ≧ 0.05.   The electrode material according to claim 1, wherein x ≦ 0.5.   The electrode material according to claim 1, wherein y ≧ 0.03.   It is y <= 0.3, The electrode material of any one of Claims 1-6.   The electrode material according to claim 1, wherein δ ≧ 0.0.   The electrode material according to claim 1, wherein δ ≦ 0.4.   The electrode material according to any one of claims 1 to 9, wherein the conductivity at 750 ° C is 800 S / cm or more.   The electrode material according to any one of claims 1 to 10, which has a coefficient of thermal expansion of 14.5 ppm / K or less. An anode,
The air electrode,
A solid electrolyte layer provided between the fuel electrode and the air electrode;
A current collecting layer provided on the opposite side of the solid electrolyte on the air electrode, and comprising the electrode material according to claim 1,
A fuel cell comprising: