JP4038628B2 - Oxide ion conductor, method for producing the same, and solid oxide fuel cell - Google Patents

Description

【図面の簡単な説明】
【図１】 実施例２、４及び５並びに比較例１及び２で製造した酸化物の焼結体の粉末Ｘ線回折測定の結果を示すチャートである。
【図２】 実施例１〜３の酸化物：(ＣｅＯ₂)_0.8(ＳｍＯ_1.5)_0.19(ＧａＯ_1.5)_0.01及び比較例２〜４の酸化物：(ＣｅＯ₂)_0.8(ＳｍＯ_1.5)_0.2についての焼成温度と焼結体の平均粒径との関係を示すグラフである。
【図３】 実施例２、４及び５並びに比較例１〜３の酸化物についてのガリウムの添加モル％（一般式（１）中のｙの値）と平均粒径との関係を示すグラフである。
【図４】 実施例２、４及び５並びに比較例１〜３の酸化物についてのガリウムの添加モル％（一般式（１）中のｙの値）と焼結体の絶対密度及び気孔率との関係を示すグラフである。
【図５】 実施例２、４及び５並びに比較例１〜３の酸化物についてのガリウムの添加モル％（一般式（１）中のｙの値）と焼結体の800℃での導電率との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel oxide and a method for producing the same, and more particularly to a novel ceria-based oxide useful as an oxide ion conductor and a method for producing the same.
[0002]
The present invention relates to an oxide ion conductor and a solid oxide fuel cell, and more particularly, to an oxide ion conductor useful as an electrolyte material for a solid electrolyte fuel cell, an oxygen sensor, an oxygen pump, and the like, and the oxide ion The present invention relates to a solid oxide fuel cell using a conductor as an electrolyte.
[0003]
[Prior art]
A ceria-based composite oxide having a trivalent rare earth element other than Ce and Ce (for example, Sm) as a constituent element (cation) is used for a solid oxide fuel cell, oxygen, because of its excellent oxide ion conductivity. In recent years, it has attracted attention as an electrolyte material for sensors and oxygen pumps. In particular, the excellent conductive properties of ceria-based composite oxides are expected to be effective in reducing the operating temperature of the battery, which is one of the important issues for putting solid oxide fuel cells into practical use. Yes.
[0004]
However, conventional ceria-based composite oxides generally have low sinterability, and when they are produced by solid phase reaction, the raw materials must be fired at a high temperature of around 1600 ° C. Problems such as an increase in the cost required for firing and a decrease in the purity of the sintered body due to the progress of side reactions during the solid-phase reaction have been a major obstacle to the practical application of ceria-based composite oxides.
[0005]
[Problems to be solved by the invention]
The present invention overcomes the drawbacks in the production of such conventional ceria-based composite oxides, and can be produced under milder conditions without deteriorating the properties of the oxide ion conductor. An object of the present invention is to provide a novel ceria-based oxide. An object of the present invention is to provide a method for producing a novel ceria-based oxide useful as an oxide ion conductor under mild conditions.
[0006]
An object of the present invention is to provide an oxide ion conductor that exhibits high oxide ion conductivity even at a relatively low temperature (for example, 900 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower). An object of the present invention is to provide a solid oxide fuel cell that can be effectively operated even at a relatively low temperature (eg, 900 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower).
[0007]
[Means for Solving the Problems]
In order to develop a method for producing an oxide ion conductive property equivalent to or better than that of a conventional ceria-based composite oxide and useful as an oxide ion conductor under milder conditions, the present inventor As a result of intensive studies, the addition of a specific amount of Ga as a constituent element (cation) to a ceria-based oxide containing Ce and a trivalent rare earth element other than Ce as a constituent element (cation) It was found that the oxide can be produced under milder conditions and that the resulting oxide has good characteristics as an oxide ion conductor, and the present invention has been completed.
[0008]
That is, the present invention relates to an oxide ion conductor made of an oxide represented by the general formula (1): (CeO ₂ ) _1-x (LnO _1.5 ) _xy (GaO _1.5 ) _y . Ln is one or more selected from trivalent rare earth elements other than Ce (preferably a group consisting of Y, La, Pr, Nd, Sm and Gd). x is a value satisfying 0.05 ≦ x ≦ 0.4. y is a value satisfying 0 <y <0.05.
[0009]
The present invention provides a method for producing a ceria-based oxide, characterized in that a mixed powder of CeO ₂ , Ln ₂ O ₃ and Ga ₂ O ₃ is sintered at 1400 to 1600 ° C. to obtain any one of the above oxides. Related. In the present invention, the powder obtained by calcining a mixed powder of CeO ₂ , Ln ₂ O ₃ and Ga ₂ O ₃ at 1000 to 1300 ° C. and then pulverizing is sintered at 1400 to 1600 ° C. The present invention relates to a method for producing a ceria-based oxide.
[0010]
The present invention resides in an oxide ion conductor comprising any one of the above oxides. The present invention relates to a solid oxide fuel cell using the oxide ion conductor as an electrolyte.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Oxide of the present invention (oxide oxide conductor)
A composite oxide containing Ce and a trivalent rare earth element (Ln) other than Ce as a constituent element (cation), that is, a part of Ce in ceria is replaced with a trivalent rare earth element (Ln) other than Ce. The oxide has a fluorite-type crystal structure corresponding to the crystal structure in which oxygen defects are generated in the crystal structure of ceria, and is considered to exhibit oxide ion conductivity by the action of the oxygen defects. .
[0012]
Examples of trivalent rare earth elements (Ln) other than Ce include Sc, Y, La, and lanthanide elements (Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, etc. ) And Ac or the like. There are one or more trivalent rare earth elements selected from the group consisting of Ac and the like. In a preferred embodiment, one or more selected from the group consisting of Y, La, Pr, Nd, Sm, and Gd is used as the trivalent rare earth element (Ln) other than Ce.
[0013]
The upper limit of the value of x in the general formula (1) corresponding to the substitution rate of Ce with trivalent rare earth elements (Ln) other than Ce with respect to ceria is 0.4 or less, preferably 0.3 or less, more preferably 0.299 or less, It is preferably 0.29 or less, more preferably 0.27 or less, particularly preferably 0.25 or less, still more preferably 0.23 or less. The lower limit of the value of x is 0.05 or more, preferably 0.1 or more, more preferably 0.15 or more. When the value of x exceeds 0.4, the conductivity tends to decrease rapidly.
[0014]
When the oxide of the present invention, which is a complex oxide containing Ce, a trivalent rare earth element (Ln) other than Ce and Ga as a constituent element (cation), is produced from a raw material mixed powder by a solid phase reaction, for example. When a dense ceria-based composite oxide is formed by a sintering reaction that proceeds simultaneously with the solid-phase reaction, it is considered that Ga acts to increase the grain growth rate.
[0015]
The upper limit of the value of y in the general formula (1) corresponding to the substitution ratio of Ce with Ga for ceria is less than 0.05, preferably 0.049 or less, more preferably 0.04 or less, still more preferably 0.03 or less, and particularly preferably 0.02 or less. To do. The lower limit of the value of y is more than 0, preferably 0.001 or more, more preferably 0.004 or more, and still more preferably 0.07 or more. If the value of y is 0.05 or more, a side reaction between trivalent rare earth elements (Ln) other than Ga and Ce proceeds during production, and impurities (for example, a garnet-type compound represented by Ga ₅ Ln ₃ O ₁₂ ) Phase is generated and the crystal structure does not become a fluorite-type single phase, and as a result, grain growth is suppressed and conductivity tends to decrease.
[0016]
The oxide of the present invention is useful as an oxide ion conductor. The oxide of the present invention having an electric conductivity at 1000 ° C. of 0.15 S / cm or more, preferably 0.18 S / cm or more, more preferably 0.2 S / cm or more is specifically used as an oxide ion conductor. It is particularly useful as an electrolyte material for an electrolyte fuel cell.
[0017]
The oxide of the present invention having a conductivity at 800 ° C. of 0.075 S / cm or more, preferably 0.08 S / cm or more, more preferably 0.085 S / cm or more, and still more preferably 0.09 S / cm or more is an oxide ion conductivity. Specifically, it is particularly useful as an electrolyte material for a solid oxide fuel cell that operates at a relatively low temperature (for example, 900 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower).
[0018]
The oxide of the present invention having an absolute density (at 25 ° C.) by Archimedes method of 6.6 or more, preferably 6.7 or more, more preferably 6.8 or more, 7 or less, preferably 6.99 or less, more preferably 6.98 or less. Are particularly useful as oxide ion conductors.
[0019]
The oxide of the present invention having a relative density of 97% or more is particularly useful as, for example, an electrolyte material for a solid oxide fuel cell because it has high density and low oxygen gas permeability. Here, the relative density is a relative value obtained by dividing the absolute density (25 ° C.) by the Archimedes method by the theoretical density calculated from the lattice constant.
[0020]
The oxidation according to the present invention having a porosity of 10% or less, preferably 8% or less, more preferably 6% or less, more preferably 5.5 or less (usually 0.5% or more, further 1% or more, particularly 1.5% or more). Since the material has high density and low oxygen gas permeability, it is particularly useful, for example, as an electrolyte material for a solid oxide fuel cell.
[0021]
Here, the porosity is three electron micrographs obtained using a sample in which a mirror-polished surface of the oxide of the present invention is subjected to thermal etching and then coated with a thin film of a conductive material (for example, Pt—Pd). It can be obtained by preparing, drawing a grid thereon (normal number of grid points: 357 points per picture), counting the intersection of grid points and pores and dividing by the total number of grid points.
[0022]
Whether the oxide is dense or not can be determined, for example, by assembling a solid oxide fuel cell using the oxide as an electrolyte material and measuring the open circuit voltage. For example, if the oxide used as the electrolyte material is not dense enough, oxygen and hydrogen are short-circuited in the electrolyte, so there is no theoretical electromotive force.
[0023]
The oxide of the present invention having an average particle size of 2 μm or more, preferably 4 μm or more, more preferably 6 μm or more, more preferably 8 μm or more (usually 30 μm or less, further 25 μm or less, particularly 20 μm or less) It is particularly useful as an ionic conductor.
[0024]
Here, the average particle diameter is three electron micrographs obtained using a sample in which a mirror-polished surface of the oxide of the present invention is subjected to thermal etching and then coated with a thin film of a conductive material (for example, Pt—Pd). Prepare at least 10 straight lines with a length of about 70μm in any position and direction on each photo, measure the length of each straight line that crosses the grain one by one, and multiply all values by 1.5 Then, it can be obtained by averaging.
[0025]
The absolute density, relative density, porosity, average particle diameter, and the like of the oxide of the present invention depend on the type of trivalent rare earth element (Ln) other than Ce, for example, x and y in the general formula (1). It can be controlled by adjusting the value and by adjusting the production conditions (for example, in the case of production by a solid phase reaction method, the firing temperature and the like).
[0026]
Production Method of Oxide of the Present Invention (1) Solid Phase Reaction Method The oxide of the present invention can be produced based on a solid phase reaction method. For example, an oxide of each constituent cation (CeO ₂ , Ln ₂ O ₃ , Ga ₂ O _3, etc.) or an oxide (for example, carbonate etc.) that can form these oxides by firing satisfies the general formula (1). The oxide of the present invention can be produced by firing a raw material mixture mixed at a predetermined molar ratio so as to have a composition to be fired at a predetermined temperature for a predetermined time.
[0027]
By calcining for a predetermined time at a temperature lower than the firing temperature before firing the mixed raw material, an oxide having a more uniform composition can be easily produced. The raw material mixture can be calcined or fired after the powder is pressure-formed at a predetermined temperature for a predetermined time. When the raw material mixture is calcined, the calcined raw material mixture can be pulverized and subjected to pressure molding at a predetermined temperature for a predetermined time, followed by firing.
[0028]
The calcination temperature is, for example, 1300 ° C. or higher, preferably 1400 ° C. or higher, and is usually not higher than the temperature at which melting is not complete, specifically 1600 ° C. or lower, preferably 1500 ° C. or lower. The firing time can be, for example, 5 hours or longer, preferably 10 hours or longer, more preferably 15 hours or longer, and usually 30 hours or shorter, preferably 24 hours or shorter.
[0029]
When the firing temperature is low (for example, lower than 1400 ° C., particularly lower than 1300 ° C.), sintering is difficult to proceed, densification is insufficient, and pores tend to be left behind in the sintered body. If pores are left in the sintered body, the left pores are not preferable because they increase the resistance at the grain boundaries of the crystal grains and consequently lower the conductivity of the sintered body.
[0030]
Conversely, when the firing temperature is high (for example, higher than 1500 ° C., particularly higher than 1600 ° C.), it tends to cause severe grain growth and tends to leave a large amount of pores at the grain boundary, leaving a large amount of pores. And the density of a sintered compact falls, and since the electrical conductivity of a sintered compact falls as a result, it is not preferable.
[0031]
The calcination temperature can be, for example, 900 ° C. or higher, preferably 1000 ° C. or higher, and usually 1400 ° C. or lower, preferably 1300 ° C. The calcination time can be, for example, 12 hours or more, preferably 18 hours or more, usually 48 hours or less, preferably 36 hours or less, and specifically about 24 hours.
[0032]
When the calcination temperature is low (for example, lower than 1000 ° C., particularly lower than 900 ° C.), the solid-phase reaction tends to be difficult to proceed, and when it is high (for example, higher than 1400 ° C., particularly higher than 1300 ° C.) There is a tendency that sintering proceeds too much and many pores are formed. If many pores are formed, it is easy to cause a decrease in the conductivity of the sintered body, which is not preferable.
[0033]
The pressure forming method of the raw material mixture or the calcined and pulverized raw material mixture is not particularly limited, and a known method can be used. For example, the raw material mixture is formed at a pressure of 500 to 1500 kgf / cm ² by a die press. Moreover, it can shape | mold by the pressure of about 2000-3000Kgf / cm < ² > by an isostatic isostatic press as needed.
[0034]
(2) Thin film formation method The oxide of this invention can be manufactured as a thin film by the well-known method for depositing a metal oxide thin film from a gaseous phase. The oxide thin film of the present invention is formed by, for example, a vacuum deposition method, a sputtering method, a PVD method such as an ion plating method, a thermal CVD method, a plasma CVD method, a CVD method such as a laser CVD method, or a thin film formation method such as a thermal spraying method. Can be manufactured.
[0035]
Solid electrolyte fuel cell Solid oxide fuel cell that can be operated even in a relatively low temperature range by using the oxide ion conductor made of the oxide of the present invention as an electrolyte of a solid electrolyte fuel cell. A fuel cell can be provided.
[0036]
A solid oxide fuel cell has an electrolyte and an electrode (anode and cathode) installed in contact with the electrolyte as main components, and fuel (for example, hydrogen, natural gas, methanol, coal gas) on the anode side of the electrolyte. By supplying and supplying air (oxygen) to the cathode side, the oxygen supplied to the cathode side receives electrons from the cathode and becomes oxide ions, and these oxide ions diffuse in the electrolyte and reach the anode side. Reacts 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.
[0037]
Examples of the solid oxide fuel cell include a cylindrical solid electrolyte fuel cell having a structure in which a cathode layer, an electrolyte layer, and an anode layer are sequentially formed and stacked on a cylindrical surface of a cylindrical support tube, There is a flat-type solid electrolyte fuel cell that has a structure in which an anode layer is formed on one of both surfaces of an electrolyte layer and a cathode layer is formed on the other, and is used by forming a stack that is sequentially stacked via a separator. The oxide ion conductor of the present invention can be used as an electrolyte for any type of solid oxide fuel cell.
[0038]
The thickness of the electrolyte layer should be selected appropriately in consideration of the characteristics required for the solid oxide fuel cell, the mechanical strength required for the electrolyte layer, the conductivity of the oxide ion conductor used as the electrolyte, etc. Although there is no particular limitation, it is generally 1 mm or less, preferably 500 μm or less, more preferably 200 μm or less, still more preferably 100 μm or less, usually 5 μm or more, preferably 10 μm or more, more preferably 30 μm or more, More preferably, it can be 50 μm or more.
[0039]
The electrolyte layer made of the oxide ion conductor of the present invention can be formed, for example, by a sheet forming and sintering method which is a conventional ceramic process, or by a thin film forming method such as a PVD method, a CVD method or a thermal spraying method. For example, it can be formed on a gas permeable porous substrate. Since the oxide (oxide ion conductor) of the present invention can be produced by a sintering method at a relatively low temperature (for example, 1600 ° C. or less, particularly 1500 ° C. or less), co-sintering with an electrode material It can also be manufactured by law.
[0040]
As the anode and the cathode, for example, a porous body having a porosity of about 30% and an electron conductive material that is stable in fuel and air can be used. By using a porous body as an electrode, a reaction can be performed at the electrolyte / electrode / gas phase (fuel, air) three-phase interface, and by increasing the area of the three-phase interface, the reaction field is increased. can do.
[0041]
As the anode, for example, a composite material of Ni and Y ₂ O ₃ stabilized ZrO ₂ (Ni—YSZ cermet) can be used. As the cathode, for example, a (LaSr) MnO ₃ -based material can be used.
[0042]
【The invention's effect】
The oxide of the present invention can be produced by solid phase reaction by adding a small amount of trivalent gallium (Ga ³⁺ ) oxide as the third component cation to the ceria oxide solid phase reaction system. Since grain growth is remarkably promoted, a dense sintered body can be obtained even under mild conditions with a reduced firing temperature.
[0043]
The oxide of the present invention has sufficiently good ionic conductivity as an electrolyte for a solid oxide fuel cell even at relatively low temperatures (eg, 900 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower). Therefore, it is useful as an electrolyte of a solid oxide fuel cell that can be operated even at a relatively low temperature (for example, 900 ° C. or lower, preferably 850 ° C. or lower, more preferably 800 ° C. or lower). It can also be used as an oxygen sensor and oxygen pump.
[0044]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these.
[0045]
Examples 1 to 5 [Ln: Sm, y: 0.002 to 0.01 , firing temperature: 1400 to 1600 ° C.]
CeO ₂ (Shin-Etsu Chemical Co., Ltd., purity 99.99%), Sm ₂ O ₃ (Shin-Etsu Chemical Co., Ltd., purity 99.9%) and Ga ₂ O ₃ (High Purity Chemical Laboratory, purity 99.99%) powder Were weighed and mixed so as to have the composition shown in Table 1. The obtained raw material mixture was mixed and ground for 24 hours with a ball mill in ethanol, ethanol was removed, and the mixture was dried at 100 ° C.
[0046]
The obtained raw material mixed powder was transferred to a crucible, calcined at 1000 ° C. for 18 hours in an electric furnace in an air atmosphere, pulverized, pressed (500 kgf / cm ² ) and isotropic isostatic press (3000 kgf / cm ^2). ) To obtain a green body before firing. The obtained pre-fired shaped body was fired at the firing temperature shown in Table 1 for 24 hours to obtain a sintered body (oxide of the present invention).
[0047]
The obtained sintered body was identified by powder X-ray diffraction measurement. FIG. 1 shows the results (chart) of the powder X-ray diffraction measurement for the sintered bodies (Examples 2, 4 and 5) obtained by firing at 1500 ° C.
[0048]
From the scanning electron microscope (SEM) photograph of the sample obtained by applying the Pt-Pd coating after performing thermal etching at a temperature lower than the firing temperature after mirror polishing the surface of the obtained sintered body, The average particle size was measured. The results are shown in Table 1. FIG. 2 shows the relationship between the firing temperature and the average particle diameter of the sintered body (Examples 1 to 3) of y: 0.01. FIG. 3 shows the relationship between the value of y and the average particle diameter of the sintered bodies (Examples 2, 4 and 5) obtained by firing at 1500 ° C. A scanning electron microscope (SEM) photograph of the sintered body obtained in Example 2 is shown in the reference photograph.
[0049]
The density of the obtained sintered body was determined by the Archimedes method. The results are shown in Table 1. FIG. 4 shows the relationship between the value of y and the density of the sintered bodies (Examples 2, 4 and 5) obtained by firing at 1500 ° C.
[0050]
After winding the obtained sintered body and applying surface polishing to a 3mm x 3mm x 20mm rectangular parallelepiped sample, four platinum wires were wound around it, and platinum paste was applied and fixed. Using a sample prepared by baking for 30 minutes, the electrical conductivity was measured at 800 ° C. in air by the direct current four-terminal method. The results are shown in Table 1. FIG. 5 shows the relationship between the value of y and the electrical conductivity of sintered bodies (Examples 2, 4 and 5) obtained by firing at 1500 ° C.
[0051]
Example 6 [Ln: Gd, y: 0.01 , firing temperature: 1500 ° C.]
Example 2 was repeated except that Gd ₂ O ₃ (manufactured by Shin-Etsu Chemical Co., Ltd., purity 99.9%) was used in place of the Sm ₂ O ₃ powder. The results are shown in Table 1.
[0052]
Example 7 [Ln: Y, y: 0.01 , firing temperature: 1500 ° C.]
The same procedure as in Example 2 was performed except that Y ₂ O ₃ (manufactured by Japan Yttrium Co., Ltd., purity 99.9%) powder was used instead of the Sm ₂ O ₃ powder. The results are shown in Table 1.
[0053]
Comparative Example 1 [Ln: Sm, y: 0.05 , firing temperature: 1500 ° C.]
CeO ₂ (Shin-Etsu Chemical Co., Ltd., purity 99.99%), Sm ₂ O ₃ (Shin-Etsu Chemical Co., Ltd., purity 99.9%) and Ga ₂ O ₃ (High Purity Chemical Laboratory, purity 99.99%) powder Was used in the same manner as in Example 2 except that a raw material mixture obtained by weighing and mixing so as to have the composition shown in Table 1 was used. The results are shown in Table 1 and FIGS. 1, 3, 4 and 5. In FIG. 1, the diffraction peak considered to be attributed to Ga ₅ Sm ₃ O ₁₂ appears for the sintered body of Comparative Example 1.
[0054]
Comparative Examples 2 to 4 [Ln: Sm, y: 0, firing temperature: 1500 to 1700 ° C.]
Raw material mixture in which CeO ₂ (Shin-Etsu Chemical Co., Ltd., purity 99.99%) and Sm ₂ O ₃ (Shin-Etsu Chemical Co., Ltd., purity 99.9%) powders were weighed and mixed to have the composition shown in Table 1. The same procedure as in Examples 1 to 5 except that the firing temperature was 1500-1700 ° C. The results are shown in Table 1, FIGS.
[0055]
Comparative Examples 5 and 6 [Ln: Gd, y: 0, firing temperature: 1500 to 1600 ° C.]
Raw material mixture in which CeO ₂ (Shin-Etsu Chemical Co., Ltd., purity 99.99%) and Gd ₂ O ₃ (Shin-Etsu Chemical Co., Ltd., purity 99.9%) powders were weighed and mixed to have the composition shown in Table 1. The same procedure as in Examples 1 to 5 except that the firing temperature was 1500-1700 ° C. The results are shown in Table 1.
[0056]
[Table 1]

[Brief description of the drawings]
1 is a chart showing the results of powder X-ray diffraction measurement of oxide sintered bodies produced in Examples 2, 4 and 5 and Comparative Examples 1 and 2. FIG.
FIG. 2 shows the oxides of Examples 1-3: (CeO ₂ ) _0.8 (SmO _1.5 ) _0.19 (GaO _1.5 ) _0.01 and Comparative Examples 2-4: (CeO ₂ ) _0.8 (SmO _1.5 ) _0.2 It is a graph which shows the relationship between a calcination temperature and the average particle diameter of a sintered compact.
FIG. 3 is a graph showing the relationship between the added mol% of gallium (value of y in general formula (1)) and the average particle diameter for the oxides of Examples 2, 4, and 5 and Comparative Examples 1 to 3. is there.
FIG. 4 is a graph showing the addition of mol% of gallium (value of y in the general formula (1)), absolute density and porosity of sintered bodies for the oxides of Examples 2, 4 and 5 and Comparative Examples 1 to 3. It is a graph which shows the relationship.
FIG. 5 shows the mol% of gallium (value of y in the general formula (1)) and the conductivity of sintered bodies at 800 ° C. for the oxides of Examples 2, 4 and 5 and Comparative Examples 1 to 3. It is a graph which shows the relationship.

Claims (13)

General formula (1): Oxide ion conductor composed of an oxide represented by (CeO ₂ ) _1-x (LnO _1.5 ) _xy (GaO _1.5 ) _y [Ln is selected from trivalent rare earth elements other than Ce Or one or more elements, 0.05 ≦ x ≦ 0.4, 0 <y <0.05]. y is 0 <Y ≦ 0.04 The oxide ion conductor according to claim 1. y is 0 <Y ≦ 0.03 The oxide ion conductor according to claim 1. The oxide ion conductor according to any one of claims 1 to 3 , wherein Ln is one or more elements selected from the group consisting of Y, La, Pr, Nd, Sm and Gd. The oxide ion conductor according to claim 1, wherein the crystal structure is a fluorite type. The oxide ion conductor according to any one of claims 1 to 5 , which has a conductivity at 1000 ° C of 0.15 S / cm or more. The oxide ion conductor according to any one of claims 1 to 6 , wherein the conductivity at 800 ° C is 0.075 S / cm or more. The oxide ion conductor according to any one of claims 1 to 7, which has an absolute density at 25 ° C of 6.6 to 7 . The oxide ion conductor according to any one of claims 1 to 8 , having a relative density of 97% or more. The sintered body comprising a granular material of an oxide ion conductor according to any one of claims 1 to 9 , wherein the average particle size is 2 µm or more. Ceria, characterized in that obtaining an oxide ion conductor according to any one of claims 1 to 10 by sintering a mixed powder of CeO _2, Ln ₂ O ₃ and Ga ₂ O ₃ at 1400 to 1600 ° C. A method for producing an oxide ion conductor made of an oxide . The powder obtained by calcining a mixed powder of CeO ₂ , Ln ₂ O ₃ and Ga ₂ O ₃ at 1000-1300 ° C and then pulverizing the powder is sintered at 1400-1600 ° C to claim 1-10. method of manufacturing an oxide ion conductor comprising a ceria-based oxide, characterized in that to obtain an oxide ion conductor according. A solid oxide fuel cell comprising the oxide ion conductor according to claim 1 as an electrolyte.

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