JP2003212653A - Oxide ion conductor and solid oxide type fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compound which has high electrical conductivity and excellent durability, and is useful as an oxide ion conductor, and to provide a solid oxide type fuel cell which is provided with the above compound as an electrolyte. <P>SOLUTION: The compound is expressed by the general formula (1) of Ba<SB>2</SB>(In<SB>1-x-y</SB>L<SB>x</SB>M<SB>y</SB>)<SB>2</SB>O<SB>5</SB>[wherein, L is at least one kind selected from the group consisting of tervalent cations whose ion radius in 6 coordination number is >0.8 Å; M is at least one kind selected from the group consisting of tervalent cations whose ion radius in 6 coordination number is <0.8 Å; the weighted mean ion radius of L and M is 0.785 to 0.805 Å; x is 0.05 to 0.5; y is 0.05 to 0.5; and x+y≤0.6]. The oxide ion conductor consists of the above compound, and the solid oxide type fuel cell is provided with the above oxide ion conductor as the electrolyte. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a Ba ₂ In ₂ O ₅ type compound, and more particularly to a compound useful as an oxide ion conductor. The present invention also relates to a solid oxide fuel cell including the above compound as an electrolyte.

[0002]

2. Description of the Related Art High conductivity is one of the important characteristics required for electrolytes used in solid oxide fuel cells and the like. At present, as solid electrolytes having high conductivity, compounds having a fluorite structure such as zirconia and ceria-based oxides; compounds having a structure similar to a perovskite structure are known. For example, as one of the perovskite-type structural analogs, Ba ₂ I
n ₂ O ₅ can be exemplified, and this compound has a structure in which oxygen is regularly depleted from the perovskite type structure (defective perovskite type structure). Ba ₂ In ₂ O ₅ is 930
Since it has good conductivity at high temperatures above about ℃,
It can be used as an electrolyte of a solid oxide fuel cell.

However, Ba ₂ In ₂ O ₅ undergoes a phase transition at around 930 ° C., and at about 930 ° C. or lower, it becomes a brown millerite-type oxide in which oxygen vacancies existing in the crystal are ordered. The conductivity drops sharply due to the ordered arrangement of oxygen vacancies. Therefore, the solid oxide fuel cell using Ba ₂ In ₂ O ₅ cannot be operated at a temperature lower than 930 ° C.

The present inventors have conducted intensive studies to develop an oxide ion conductor having high conductivity and useful as a solid electrolyte material. As a result, one of In in Ba ₂ In ₂ O ₅ Part 3
It has been found that by substituting with a valent cation, a rapid decrease in conductivity due to a phase transition does not occur even in a low temperature region (JP-A-11-240717).

The compounds described in the above publications show higher oxide ion conductivity as the weighted average ionic radius increases. However, there is a problem that as the weighted average ionic radius increases, the strain in the crystal increases and the durability decreases.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the problems of the prior art, and has high conductivity and excellent durability, and is used as an oxide ion conductor. It is a main object to provide a useful compound and a solid oxide fuel cell provided with the compound as an electrolyte.

[0007]

The present inventors have developed Ba ₂ In ₂ O ₅ in order to develop oxide ion conductors with higher performance.
Attention was paid to the cations substituting In in the system compounds. Therefore, as a result of extensive studies, the present inventor has combined a trivalent cation having a larger ionic radius than In and a trivalent cation having a smaller ionic radius, and has a weighted average ionic radius close to that of In. It has been found that when the value is set to a value, the conductivity is improved and the durability is excellent, and the present invention has been completed.

That is, the present invention relates to the following compounds, conductors, and solid oxide fuel cells provided with the conductors. 1. Formula _{(1): Ba 2 (In} 1-xy L x M y) 2 O 5 (1) [ wherein, L is selected from the group of 6 coordination ion radius is 0.8 greater than the trivalent cation Represents at least one, M represents at least one selected from the group consisting of trivalent cations having a hexacoordinated ionic radius of less than 0.8, and L and
The weighted average ion radius of M is 0.785 to 0.805Å, and x is
0.05 to 0.5, y is 0.05 to 0.5, and x + y ≦ 0.6
The compound represented by. 2. L is a trivalent cation of at least one element selected from the group consisting of Group IIIa elements and Group IIIb elements, and M is selected from the group consisting of Group IIIa elements, Group IIIb elements and transition metal elements 3 of at least one element
The compound according to 1 above, which is a valent cation. 3. The ionic radius of L 6 is larger than 0.8Å
It is less than 1.1Å, and the ionic radius of M in 6-coordinate is 0.
The compound according to 1 or 2 above, which is 5 Å or more and less than 0.8 Å. 4. L is at least one selected from the group consisting of Yb ³⁺ , Y ³⁺ , Gd ³⁺ and Sm ³⁺ , and M is Ga ³⁺ and / or Al ³⁺ . Compound. 5. 1 in which x is 0.05 to 0.3 and y is 0.05 to 0.3
5. The compound according to any one of to 4. 6. The compound according to any one of 1 to 5 above, which does not exhibit a phase change at 500 to 1000 ° C. 7. An oxide ion conductor comprising the compound according to any one of 1 to 6 above. 8. Logarithm of conductivity value (σ ₁₀₀₀ ) at ₁₀₀₀ ℃ (log
sigma ₁₀₀₀₎ is not less -2.5 or more, the oxide ion conductor according to claim 7 is the logarithm (logσ ₅₀₀₎ is -4.5 or more of electric conductivity at 500 ° C. The value (σ _500). 9. 9. A solid oxide fuel cell comprising the oxide ion conductor described in 7 or 8 as an electrolyte.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The compound of the present invention has the following general formula:
It is indicated by (1).

Ba ₂ (In _1-xy L _x M _y ) ₂ O ₅ (1) [wherein L is at least one selected from the group consisting of trivalent cations having a hexacoordinated ionic radius larger than 0.8] , M represents at least one selected from the group consisting of trivalent cations having a hexacoordinated ionic radius of less than 0.8, and L and
The weighted average ion radius of M is 0.785 to 0.805Å, x
Is 0.05 to 0.5, y is 0.05 to 0.5, and x + y ≦
Is 0.6]

The ionic radius in the present invention is an effective ionic radius systematically summarized from the results of crystal structure analysis of known compounds. For example, reference: RD Shannon and C.
The value is described in T. Prewitt, Acta. Cryst., B25, 925 (1969).

L in the general formula (1) is a trivalent cation and is not particularly limited as long as the ionic radius in hexacoordinate is larger than 0.8. The upper limit of the ionic radius of L in the 6-coordinate is not particularly limited, but is usually about 1.1 Å or less. Examples of L include Y ³⁺ , Ce ³⁺ , Pr ³⁺ , Nd ³⁺ , Pm
³⁺ , Sm ³⁺ , Eu ³⁺ , Gd ³⁺ , Tb ³⁺ , Dy ³⁺ , Ho ³⁺ , Er ³⁺ , T
Examples include trivalent cations of Group IIIa elements such as m ³⁺ , Yb ³⁺ , La ³⁺ , Cm ³⁺ , Bk ³⁺ , Cf ^3+, and trivalent cations of Group IIIb elements such as Tl ^3+. can do. Among these, Y
³⁺ , Ce ³⁺ , Pr ³⁺ , Nd ³⁺ , Sm ³⁺ , Eu ³⁺ , Gd ³⁺ , Tb ³⁺ , E
r ³⁺ , Yb ³⁺ and La ³⁺ are preferable, and Y ³⁺ , Sm ³⁺ , Gd ³⁺ and Yb ³⁺ are particularly preferable.

M in the general formula (1) is a trivalent cation and is not particularly limited as long as the ionic radius in hexacoordinate is smaller than 0.8. The lower limit of the ionic radius in the hexacoordinate of M is not particularly limited, but is usually about 0.5Å or more. Examples of M include trivalent cations of IIIa group elements such as Sc ^{3 +} ; trivalent cations of IIIb group elements such as Al ³⁺ and Ga ³⁺ ; Ti ³⁺ , Cr ³⁺ , Mn ³⁺ , Ni ³⁺ , Fe ³⁺ , Co ³⁺ , Ru ³⁺ , Rh
Examples thereof include trivalent cations of transition metals such as ³⁺ . As the trivalent cation of the group IIIb element, Ga ³⁺
Is preferred. The transition metal trivalent cation is T
i ³⁺ , Cr ³⁺ , Mn ³⁺ , Ni ³⁺ , Fe ³⁺ , Co ³⁺ are preferable. As M, Ga ³⁺ and Al ³⁺ are preferable, and Ga ³⁺ is particularly preferable.

X in the general formula (1) corresponds to the replacement ratio of In with L. The upper limit of x is usually about 0.5 or less,
It is preferably about 0.3 or less, more preferably about 0.25 or less. The lower limit of x is usually about 0.05 or more,
It is preferably about 0.08 or more, more preferably about 0.1 or more.

Y in the general formula (1) corresponds to the substitution ratio of In with M. The upper limit of y is usually about 0.5 or less,
It is preferably about 0.3 or less, more preferably about 0.25 or less. The lower limit of y is usually about 0.05 or more,
It is preferably about 0.08 or more, more preferably about 0.1 or more.

The value of x + y is usually about 0.6 or less, preferably about 0.5 or less. The lower limit of x + y is not particularly limited, but is usually about 0.1 or more, preferably about 0.2 or more.

If the value of x or y is too large, the second phase tends to appear. The appearance of the second phase lowers the conductivity, which is not preferable. If the value of x or y is too small, the crystal structure tends to be a brown millerite structure. That is, it becomes difficult to form a defect perovskite structure in a low temperature region, and a phase transition tends to occur easily with a change in temperature. When the phase transition occurs, the conductivity sharply decreases, which is not preferable.

In the present invention, the weighted average ion radius of L and M is a value defined by the following formula.

[0019]

[Formula 1]

The weighted average ionic radius in the general formula (1) is set so as to be close to the value of the hexagonal ionic radius of In ³⁺ (0.80Å), and is usually about 0.785 to 0.805Å, It is preferably about 0.79 to 0.804 Å, more preferably 0.7
It is about 95 to 0.803Å.

The compounds of the present invention, in the Ba ₂ In ₂ O _5, In
Trivalent cation with a larger ionic radius: L and trivalent cation with a smaller ionic radius than In: M, so that the weighted average ionic radius is close to the In ³⁺ hexacoordinate value. Has been replaced. The compound of the present invention can maintain a defect perovskite structure in which oxygen vacancies in a Ba ₂ In ₂ O ₅ crystal are disordered to improve symmetry to a low temperature, and at the same time, minimize distortion of the crystal structure. Therefore, it is possible to suppress a rapid decrease in conductivity due to the phase transition.

The compound of the present invention exhibits high conductivity and is useful as an oxide ion conductor. Logarithm of the conductivity of the compounds of the present invention (S / cm) is not particularly limited, the conductivity at 1000 ° C. the value (σ ₁₀₀₀₎ (logσ ₁₀₀₀₎ is usually -
It is about 2.5 or more, preferably about -1.5 or more. l
The upper limit of og σ ₁₀₀₀ is not particularly limited, but is usually about −0.5 or less. Log (logσ ₅₀₀₎ of the value of the conductivity (sigma ₅₀₀₎ at 500 ° C. is usually about -4.5 or more, preferably
-3.5 or more. The upper limit of log σ ₅₀₀ is not particularly limited, but is usually about −2 or less. The value of the conductivity in the present invention is obtained by grinding the compound (sintered body) to a thickness of 2 mm,
After polishing the surface, apply platinum paste on both sides and
After performing electrode baking treatment at 00 ℃ for 3 hours, AC 2 terminal method (applied AC voltage: 100 mV, frequency: 10 MHz to 100 Hz,
It is a value obtained by measuring the complex impedance using (in air).

The compounds of the present invention are useful as oxide ion conductors, particularly those in which the crystalline phase is substantially a single phase. Further, the lower limit of the temperature at which a defect perovskite type crystal structure is exhibited is about 500 ° C. or less, preferably 6
A compound having a temperature of about 00 ° C. or lower is particularly useful as an oxide ion conductor.

The oxide ion conductor comprising the compound of the present invention is useful as an electrolyte material provided in solid oxide fuel cells, oxygen sensors, oxygen pumps and the like. Particularly, the compound of the present invention showing no phase transition at about 500 to 1000 ° C. is particularly useful as an electrolyte material provided in a solid oxide fuel cell, an oxygen sensor, an oxygen pump, etc., which can be used in these temperature ranges. Is.

The compound of the present invention can form a cermet with Ni or the like. The cermet containing the compound of the present invention can be used, for example, as a composite electrode material for solid oxide fuel cells.

The method for producing the compound of the present invention is not particularly limited, and the compound can be produced, for example, by the method described below. (1) Solid phase reaction method: The compound of the present invention can be produced by an ordinary solid phase reaction method by appropriately selecting raw materials and the like so as to obtain a desired composition. For example, as raw materials, oxides of each constituent cation (BaO, In ₂ O ₃ , L ₂ O ₃ , M ₂
O _{3 and the} like), compounds capable of forming these oxides by firing (eg, carbonate, etc.) in a predetermined molar ratio so as to have a composition satisfying the general formula (1), and the like. it can. In the solid-phase reaction method, the raw material is fired in an oxidizing atmosphere such as air.

If desired, the raw material may be calcined at a temperature lower than the firing temperature for a predetermined time before being fired and then pulverized. By calcination, a compound having a more uniform composition can be easily produced. The degree of pulverization is not particularly limited, but normally pulverization may be performed until the particle size of the secondary particles becomes about 250 μm or less.

The firing temperature is not particularly limited and may be appropriately set depending on the composition of the raw material, etc., but is usually 1300 ° C.
That's about it. The upper limit of the firing temperature is not particularly limited as long as the raw material does not melt, and is usually about 1600 ° C or lower. The firing time is usually about 5 hours or more, and can be set to about 24 hours or less. If the firing temperature is too low, sintering is difficult to proceed, densification becomes insufficient, and voids are likely to be left in the sintered body. The voids left behind increase the resistance at the grain boundary, and as a result, the conductivity of the sintered body decreases, which is not preferable. On the other hand, if the firing temperature is too high, the grain growth becomes violent, and the pores tend to be left in the grains, resulting in a decrease in the conductivity of the sintered body, which is not preferable.

The calcination temperature is not particularly limited as long as the solid phase reaction proceeds sufficiently, but it is usually about 900 ° C. or higher. The upper limit of the calcination temperature is not particularly limited as long as it is lower than the calcination temperature, and can be appropriately set according to the composition of the raw material and the like. The upper limit of the calcination temperature is usually about 1250 ° C or lower. The calcination time can be, for example, about 4 hours or more and about 20 hours or less. If the calcination temperature is low, the solid-phase reaction tends to be difficult to proceed. If the calcination temperature is high, the sintering tends to proceed excessively and a large number of pores are likely to be formed, and the conductivity of the sintered body tends to be lowered.

If necessary, the raw material may be pressure-molded at a predetermined temperature for a predetermined time before being calcined or fired. The pressure molding method of the raw material or the raw material calcined and crushed is
A known method can be used without particular limitation,
For example, a method of molding with a die press at a pressure of about 40 to 150 MPa can be exemplified. If necessary, it can be further molded by an isotropic hydrostatic press at a pressure of about 100 to 350 MPa.

(2) Thin film forming method: The compound of the present invention is used as a thin film in a known method for precipitating a metal oxide thin film from a gas phase by appropriately selecting raw materials so as to obtain a desired composition. It can be manufactured. The thin film of the compound of the present invention is, for example, a vacuum vapor deposition method, a sputtering method,
PVD method such as ion plating method, thermal CVD method, plasma
It can be manufactured by a CVD method such as a CVD method or a laser CVD method, or a thin film forming method such as a thermal spraying method.

By using the oxide ion conductor comprising the compound of the present invention as the electrolyte, it is possible to provide a solid oxide fuel cell which can operate in a wide temperature range.

The solid oxide fuel cell comprises an electrolyte and electrodes (anode and cathode) placed in contact with the electrolyte. By supplying fuel (for example, hydrogen, natural gas, methanol, coal gasification gas, etc.) to the anode side of the electrolyte and supplying air (oxygen) to the cathode side, the oxygen supplied to the cathode side is converted into electrons from the cathode. To become oxide ions, the oxide ions diffuse in the electrolyte, reach the anode side, and react with the fuel supplied to the anode side. At this time, electrons leave the oxide ions, pass through the load of the external circuit, and reach the cathode.

As the solid oxide fuel cell, for example,
A flat-plate solid oxide fuel cell, which has a structure in which an anode layer is formed on one side of a flat electrolyte layer and a cathode layer is formed on the other side, and is used by forming a stack that is sequentially laminated with a separator, cylindrical A cylindrical solid oxide fuel cell or the like having a structure in which a cathode layer, an electrolyte layer and an anode layer are sequentially formed on the cylindrical surface of the supporting tube and are laminated can be exemplified. The oxide ion conductor of the present invention can be used as an electrolyte of any type of solid oxide fuel cell.

The thickness of the electrolyte layer depends on the characteristics required for the solid oxide fuel cell, the mechanical strength required for the electrolyte layer,
It can be appropriately selected in consideration of the conductivity of the oxide ion conductor used as the electrolyte and is not particularly limited, but is generally about 1 mm or less, preferably about 5 μm or more. When the oxide ion conductor of the present invention is used as an electrolyte, it may be formed into a layer, for example. As a method for forming the electrolyte layer, for example, a sheet forming sintering method which is a known ceramic process can be exemplified. More specifically, the slurry obtained by mixing the raw materials and the solvent is spread into a sheet shape, dried, and then, if necessary, molded using a cutter knife or the like and baked. Known additives such as a binder, a plasticizer, and a dispersant may be added to the slurry, if necessary. Conditions such as molding and firing can be appropriately set according to the composition of the raw material. Alternatively, the electrolyte layer can be formed on a gas permeable porous substrate by a thin film forming method such as a PVD method, a CVD method, or a thermal spraying method.

As the parts other than the electrolyte such as the anode and the cathode, known ones can be used. The anode may be, for example, a porous material having a porosity of about 30% and an electron conductor material stable in fuel. As the cathode, for example, a porous material having a porosity of about 30% and an electron conductor material stable in air can be exemplified. By using a porous body as the electrode, the reaction can be carried out at the three-phase interface of electrolyte / electrode / gas phase (fuel, oxygen). Also, 3
The reaction field can be increased by increasing the area of the phase interface.

As the anode, for example, a composite material of Ni and Y ₂ O ₃ stabilized ZrO ₂ (Ni-YSZ cermet), Ni and Sm ₂ O _{3 are used.}
A composite material with added CeO ₂ (Ni-SDC cermet) or the like can be used. As the cathode, for example, (LaS
Materials such as r) MnO ₃ series and (LaSr) CoO ₃ series can be used.

[0038]

Industrial Applicability The compound of the present invention does not cause a sharp decrease in conductivity due to a phase transition even in a low temperature range, and has good conductivity in a wide temperature range as an oxide ion conductor.

Further, the compound of the present invention has excellent durability.

The oxide ion conductor comprising the compound of the present invention is useful as an electrolyte of a solid oxide fuel cell which can be operated in a wide temperature range, and can also be utilized as an oxygen sensor, an oxygen pump, and the like. it can.

[0041]

EXAMPLES Examples of the present invention will be given below together with comparative examples.
The present invention will be described more specifically. The present invention is not limited to the examples below.

Examples 1 to 3 (Ba ₂ (In _1-xy Yb _x Ga _y ) ₂ O ₅ ) B so that the composition of the obtained compound becomes the composition shown in Table 1
aCO ₃ (purity 99.99%), In ₂ O ₃ (purity 99.9%), Yb ₂ O ₃ (purity 99.9%) and Ga ₂ O ₃ (purity 99.99%) were weighed and mixed in ethanol by a ball mill for 5 hours. After that, ethanol was removed by filtration, and the obtained powder was dried at 100 ° C. This raw material mixed powder was pressure-molded at a pressure of 127 MPa, then calcined at 1200 ° C. for 10 hours, further crushed and pressure-molded (12
7 MPa) was followed to obtain a sintered body for 20 hours baking at 1400 ° C. the _{(Ba 2 (In 1-xy} Yb x Ga y) 2 O 5).

[0043]

[Table 1]

Examples 4 to 6 (Ba ₂ (In _1-xy Y _x Ga _y ) ₂ O ₅ ) B so that the composition of the obtained compound becomes the composition shown in Table 2
aCO ₃ (Purity 99.99%), In ₂ O ₃ (Purity 99.9%), Y ₂ O ₃ (Purity
99.9%) and Ga ₂ O ₃ (purity 99.99%)
According to the same method as in Example 1, the sintered body (Ba ₂ (In _1-xy Y _x
Was obtained Ga _{y) 2} O _5).

[0045]

[Table 2]

Examples 7 to 9 (Ba ₂ (In _1-xy Gd _x Ga _y ) ₂ O ₅ ) BaCO ₃ (purity 99.99%), so that the composition of the obtained compound is as shown in Table 3. In ₂ O ₃ (purity 99.9%), Gd ₂ O ₃
(Purity 99.9%) and Ga ₂ O ₃ (purity 99.99%) were weighed, and the sintered body (Ba ₂ (In
_{1-xy Gd x Ga y)} 2 O 5) was obtained.

[0047]

[Table 3]

Examples 10 to 12 (Ba ₂ (In _1-xy Sm _x Ga _y ) ₂ O ₅ ) B so that the composition of the obtained compound is the composition shown in Table 4
aCO ₃ (purity 99.99%), In ₂ O ₃ (purity 99.9%), Sm ₂ O ₃ (purity 99.9%) and Ga ₂ O ₃ (purity 99.99%) were weighed in the same manner as in Example 1. According to the sintered body (Ba ₂ (In _1-xy Sm _x G
a _y ) ₂ O ₅ ) was obtained.

[0049]

[Table 4]

Comparative Example 1 (Ba₂In₂O_Five) The composition of the obtained compound is Ba₂In₂O_FiveSo BaCO₃
(Purity 99.99%) and In₂O₃(Purity 99.9%) is weighed and
After mixing in ethanol for 5 hours with a mill, filter
Ethanol was removed with and the resulting powder was dried at 100 ° C.
Dried This raw material mixed powder was pressure-molded at a pressure of 127 MPa.
After calcination at 1000 ℃ for 24 hours, crushing and pressure molding
(127MPa), then calcination at 1300 ℃ for 20 hours to sinter
Body (Ba₂In₂O _Five) Got.

Comparative Examples 2 and 3 (Ba ₂ (In _1-xy Yb _x Ga _y ) ₂
O ₅ ), so that the composition of the obtained compound becomes the composition shown in Table 5,
BaCO ₃ (purity 99.99%), In ₂ O ₃ (purity 99.9%), Yb ₂ O ₃ (purity 99.9%) and Ga ₂ O ₃ (purity 99.99%) were weighed in the same manner as in Example 1. According to the sintered body (Ba ₂ (In
_{1-xy Yb x Ga y)} 2 O 5) was obtained.

[0052]

[Table 5]

Comparative Examples 4 and 5 (Ba ₂ (In _1-xy Y _x Ga _y ) ₂ O ₅ ) Ba so that the composition of the obtained compound becomes the composition shown in Table 6
CO ₃ (Purity 99.99%), In ₂ O ₃ (Purity 99.9%), Y ₂ O ₃ (Purity 9
9.9%) and Ga ₂ O ₃ (purity 99.99%)
According to the same method as in Example 1, the sintered body (Ba ₂ (In _1-xy Y _x Ga
_y ) ₂ O ₅ ) was obtained.

[0054]

[Table 6]

Comparative Examples 6 and 7 (Ba ₂ (In _1-xy Gd _x Ga _y ) ₂ O ₅ ), so that the composition of the obtained compound is as shown in Table 7.
BaCO ₃ (purity 99.99%), In ₂ O ₃ (purity 99.9%), Gd ₂ O ₃ (purity 99.9%) and Ga ₂ O ₃ (purity 99.99%) were weighed in the same manner as in Example 1. According to (Ba ₂ (In _{1-xy
Gd x Ga y) 2 O 5} ) was obtained.

[0056]

[Table 7]

Comparative Examples 8 and 9 (Ba ₂ (In _1-xy Sm _x Ga _y ) ₂ O ₅ ) Ba so that the composition of the obtained compound is the composition shown in Table 8
CO ₃ (purity 99.99%), In ₂ O ₃ (purity 99.9%), Sm ₂ O ₃ (purity
99.9%) and Ga ₂ O ₃ (purity 99.99%)
According to the same method as in Example 1, the sintered body (Ba ₂ (In _1-xy Sm _x G
a _y ) ₂ O ₅ ) was obtained.

[0058]

[Table 8]

Example 13 (Measurement of Electrical Conductivity) The sintered bodies obtained in Examples 1 to 12 were ground to a thickness of 2 mm, surface-polished, and then platinum paste was applied to both surfaces thereof to 1000 ° C.
After conducting electrode baking treatment for 3 hours, the complex impedance was measured at various temperatures by the AC two-terminal method (applied AC voltage: 100 mV, frequency: 10 MHz to 100 Hz, in air), and the total conductivity was obtained.

Comparative Example 10 (Measurement of Electrical Conductivity) The total electrical conductivity was obtained by the same method as in Example 13 except that the sintered bodies obtained in Comparative Examples 1 to 9 were used.

The results of Examples 1 to 3 and Comparative Example 1 are shown in FIG.
The results of Examples 4 to 6 and Comparative Example 1 are shown in FIG. 2, the results of Examples 7 to 9 and Comparative Example 1 are shown in FIG. 3, and Examples 10 to 12 and Comparative Example are shown.
The result of 1 is shown in FIG. In addition, Example 3 and Comparative Examples 1 to
The results of 3 in Figure 5, the results of Example 6 and Comparative Examples 1, 4, 5 in Figure 6, the results of Example 9 and Comparative Examples 1, 6, 7 in Figure 7, Example 12 and Comparative Examples The results of 1, 8, and 9 are shown in FIG.

“9-YSZ” in the figure is Y-stabilized zirconia (Y ₂ O ₃ ) _0.09 (Z
rO ₂ ) shows a temperature change of the conductivity of _0.91 "13-CSZ" is Ca-stabilized zirconia (Ca-stabilized zirconia) (CaO)
The temperature change of the conductivity of _0.13 (ZrO ₂ ) _0.87 is shown.

As is clear from FIGS. 1 to 4, while Ba ₂ In ₂ O ₅ (Comparative Example 1) shows a rapid change in conductivity due to a phase transition, Ba ₂ (In _1-xy L _x Ga) _y ) ₂ O ₅ (L is any of Yb, Y, Gd, and Sm, Examples 1 to 12) has a slightly lower conductivity than Ba ₂ In ₂ O ₅ (Comparative Example 1) in the high temperature region, , No change in conductivity due to phase transition was observed, and high conductivity was exhibited even in the low temperature region.

As is clear from FIG. 5, the value of Yb is larger than that of the case where the weighted average ion radii of ions larger than In (Yb) and small ions (Ga) are outside the predetermined range (Comparative Examples 2 and 3).
When the weighted average ion of Ga was almost equal to the ion radius of In (Example 3), excellent conductivity was exhibited. Figure 6 ~
A similar tendency was confirmed in No. 8.

Further, the compounds of Examples are excellent in durability as compared with the compounds having a weighted average ionic radius outside the predetermined range.

[Brief description of drawings]

FIG. 1 shows Ba ₂ (In) produced in Comparative Example 1 and Examples 1 to 3.
Is a graph showing the temperature dependence of the _1-xy Yb _x Ga _y) conductivity of ₂ O _5. In Examples 1 to 3, the weighted average ion radius was set to fall within a predetermined range, and the value of x + y was changed. The symbols in the figure are as follows. ○: Example 1, △: Example
2, □: Example 3, solid line: Comparative Example 1.

FIG. 2 shows Ba ₂ (In) produced in Comparative Example 1 and Examples 4 to 6.
Is a graph showing the temperature dependence of the _1-xy Y _x Ga _y) conductivity of ₂ O _5. In Examples 4 to 6, the weighted average ion radius was set within a predetermined range, and the value of x + y was changed. The symbols in the figure are as follows. ◯: Example 4, Δ: Example
5, □: Example 6, solid line: Comparative Example 1.

FIG. 3 shows the Ba ₂ (In) produced in Comparative Example 1 and Examples 7 to 9.
It is a graph showing the temperature dependence of the _1-xy Gd _x Ga _y) conductivity of ₂ O _5. In Examples 7 to 9, the weighted average ion radius was set within a predetermined range, and the value of x + y was changed. The symbols in the figure are as follows. ◯: Example 7, Δ: Example 8, □: Example 9, solid line: Comparative Example 1.

FIG. 4 shows Ba ₂ (In) produced in Comparative Example 1 and Examples 10-12.
Is a graph showing the temperature dependence of the _1-xy Sm _x Ga _y) conductivity of ₂ O _5. In Examples 10 to 12, the weighted average ion radius was set to be within a predetermined range, and the value of x + y was changed. The symbols in the figure are as follows. ◯: Example 10, Δ: Example 11, □: Example 12, solid line: Comparative Example 1.

FIG. 5: Ba ₂ (In) produced in Comparative Examples 1 to 3 and Example 3
Is a graph showing the temperature dependence of the _1-xy Yb _x Ga _y) conductivity of ₂ O _5. The ratio of x and y was changed with x + y = 0.3. The symbols in the figure are as follows. ◯: Comparative example 2, Δ: Comparative example 3,
□: Example 3, solid line: Comparative example 1.

6] Ba ₂ (In produced in Comparative Examples 1, 4, 5 and Example 6
Is a graph showing the temperature dependence of the _1-xy Y _x Ga _y) conductivity of ₂ O _5. The ratio of x and y was changed with x + y = 0.3. The symbols in the figure are as follows. ◯: Comparative example 4, Δ: Example 6,
□: Comparative example 5, solid line: Comparative example 1.

FIG. 7: Ba ₂ (In prepared in Comparative Examples 1, 6, and 7 and Example 9)
It is a graph showing the temperature dependence of the _1-xy Gd _x Ga _y) conductivity of ₂ O _5. The ratio of x and y was changed with x + y = 0.3. The symbols in the figure are as follows. ◯: Comparative example 6, Δ: Example 9,
□: Comparative example 7, solid line: Comparative example 1.

FIG. 8: Ba ₂ (I prepared in Comparative Examples 1, 8 and 9 and Example 12)
_{n 1-xy Sm x Ga y} ) is a graph showing the temperature dependence of the electrical conductivity of ₂ O _5. The ratio of x and y was changed with x + y = 0.3. The symbols in the figure are as follows. ◯: Comparative example 8, Δ: Example 1
2, □: Comparative example 9, solid line: Comparative example 1.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4G030 AA10 AA11 AA12 AA34 AA36                       BA03                 5G301 CA02 CA12 CA15 CA26 CD01                 5H026 AA06 CX05 HH00 HH06 HH08

Claims (9)

[Claims] 1. A general formula _{(1): Ba 2 (In} 1-xy L x M y) 2 O 5 (1) [ wherein, L is the ionic radius greater than 0.8 trivalent 6 coordinating cations At least one selected from the group consisting of M, at least one selected from the group consisting of trivalent cations having a hexacoordinated ionic radius of less than 0.8, and L and
The weighted average ion radius of M is 0.785 to 0.805Å, and x is
0.05 to 0.5, y is 0.05 to 0.5, and x + y ≦ 0.6
The compound represented by. 2. L is a trivalent cation of at least one element selected from the group consisting of group IIIa elements and group IIIb elements, and M is group IIIa element, group IIIb element and transition metal element. The compound according to claim 1, which is a trivalent cation of at least one element selected from the group consisting of: 3. The ionic radius in 6-coordinate of L is larger than 0.8 Å and 1.1 Å or less, and the ionic radius in 6-coordinate of M is 0.5 Å or more and smaller than 0.8 Å. The described compound. 4. L is at least one selected from the group consisting of Yb ³⁺ , Y ³⁺ , Gd ³⁺ and Sm ³⁺ , and M is Ga ^3+.
The compound according to claim 1, which is and / or Al ³⁺ . 5. The compound according to any one of claims 1 to 4, wherein x is 0.05 to 0.3 and y is 0.05 to 0.3. 6. The compound according to any one of claims 1 to 5, which exhibits no phase change at 500 to 1000 ° C. 7. An oxide ion conductor comprising the compound according to any one of claims 1 to 6. Logarithm of the conductivity at 8. _{1000 ℃ (σ 1000) (logσ} 1000) is not less -2.5 or more, the logarithm of the conductivity at 500 ° C. The value (σ ₅₀₀₎ (logσ ₅₀₀₎ is -4.5 or more 8. The oxide ion conductor according to claim 7, which is 9. A solid oxide fuel cell comprising the oxide ion conductor according to claim 7 or 8 as an electrolyte.