JP7300440B2 - Solid electrolyte junction - Google Patents

Description

TECHNICAL FIELD The present invention relates to a solid electrolyte assembly having oxide ion conductivity. The solid electrolyte assembly of the present invention is used in various fields utilizing its oxygen ion conductivity.

Various oxide ion-conducting solid electrolytes are known. Such solid electrolytes are used in various fields, for example, as oxygen permeable elements, fuel cell electrolytes, and gas sensors. For example, in Patent Document 1, the general formula: La _1-X Sr _X Ga _{1-Y MgY} O ₃ (wherein X=0.05 to 0.3, Y=0.025 to 0.3) and an electrolyte membrane for an electrochemical cell comprising an oxide ion conductor having a perovskite crystal structure. This electrolyte membrane has a columnar crystal structure that grows vertically to the membrane surface and grows to the membrane surface. In the columnar crystal structure grown to the film surface, the 112 direction is oriented perpendicular to the film surface.

In Patent Document 2, apatite-type crystals are added near the bonding interface between a first layer containing La ₂ SiO ₅ as a main component and a second layer containing La ₂ Si ₂ O ₇ as a main component. A crystallographically oriented ceramic is described in which a lanthanum silicate having a structure is produced and the crystals of the lanthanum silicate are oriented along the direction perpendicular to the c-axis with respect to the original bonding interface.

Patent Document 3 describes an electrolyte-electrode assembly in which a solid electrolyte composed of an apatite-type composite oxide is interposed between an anode electrode and a cathode electrode. An intermediate layer exhibiting isotropic oxide ion conduction is interposed between the cathode-side electrode and the solid electrolyte. The intermediate layer consists of cerium oxide doped with samarium, yttrium, gadolinium or lanthanum. The solid electrolyte consists of La _x Si ₆ O _1.5X+12 (8≦X≦10). The document describes that the electrolyte-electrode assembly improves the power generation performance of the solid oxide fuel cell.

Japanese Patent Application Laid-Open No. 2008-10411 International Publication 2012/015061 Japanese Patent Application Laid-Open No. 2013-51101

As described in Patent Documents 1 to 3, various devices using oxide ion-conducting solid electrolytes have been proposed. It could not be said that sufficient conductivity was obtained.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a device that can fully utilize the oxide ion conductivity inherent in a solid electrolyte.

In order to solve the above-mentioned problems, the present inventors conducted intensive studies, and found that a solid electrolyte is inherently effective by bonding a material to an oxide ion-conducting solid electrolyte in a specific state to form a bonded body. It was found that the oxide ion conductivity that is required can be sufficiently brought out.

The solid electrolyte assembly of the present invention has been made based on the above findings, and includes a polycrystalline solid electrolyte having oxide ion conductivity, and a polycrystalline solid electrolyte having oxide ion conductivity and electronic conductivity, which is laminated in contact with the solid electrolyte. and a mixed conduction electrode layer having
Both the material forming the solid electrolyte and the material forming the mixed conducting electrode layer are uniaxially oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer. The above problems have been solved by providing such a solid electrolyte assembly.

FIG. 1 is a schematic cross-sectional view along the thickness direction showing one embodiment of a device using the solid electrolyte assembly of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on its preferred embodiments with reference to the drawings. As shown in FIG. 1, a solid electrolyte assembly 10 of the present invention includes a layer 11 made of a solid electrolyte (hereinafter referred to as "solid electrolyte layer"). The solid electrolyte layer 11 is made of a solid electrolyte having oxide ion conductivity at a predetermined temperature or higher. An electrode layer having mixed conductivity (hereinafter referred to as “mixed conduction electrode layer”) 12 is bonded to one surface of the solid electrolyte layer 11 so as to be in contact with the solid electrolyte layer 11 . In the embodiment shown in FIG. 1, the solid electrolyte layer 11 and the mixed conducting electrode layer 12 are in direct contact with each other without any other layer interposed therebetween. The mixed conducting electrode layer 12 is made of a material having oxide ion conductivity and electronic conductivity. A solid electrolyte assembly 10 is composed of the solid electrolyte layer 11 and the mixed conduction electrode layer 12 .

As shown in FIG. 1, a metal electrode 13 may be further arranged on the surface of the solid electrolyte layer 11 opposite to the surface on which the mixed conduction electrode layer 12 is arranged. In this case, the device 20 is constructed by arranging the solid electrolyte layer 11, the mixed conducting electrode layer 12 and the metal electrode 13 in this order. In the embodiment shown in FIG. 1, the solid electrolyte layer 11 and the metal electrode 13 are in direct contact with each other without any other layer interposed therebetween.

In FIG. 1, the solid electrolyte layer 11 and the mixed conduction electrode layer 12 are shown with different sizes, but the size relationship between the two is not limited to this. It can be size. The same applies to the solid electrolyte layer 11 and the metal electrode 13. Both may be of the same size, or the size of the solid electrolyte layer 11 may be larger than that of the metal electrode 13, for example.

As a result of studies by the present inventors, in the solid electrolyte assembly 10, by bonding the mixed conduction electrode layer 12 to the solid electrolyte layer 11, the electrical resistance between the solid electrolyte layer 11 and the mixed conduction electrode layer 12 is greatly reduced. It turned out to be possible. Moreover, in order to reduce the electrical resistance in the device 20, it is considered important to increase the oxide ion conductivity of the solid electrolyte layer 11. , the electrical resistance of the entire device 20 tends to increase. In particular, when a solid electrolyte layer containing lanthanum oxide, which is one of the materials with high oxide ion conductivity, is used as the solid electrolyte layer, the electrical resistance increases, and oxygen permeation through the solid electrolyte assembly 10 increases. It was found that the speed tends to decrease. The reason for this is not clear at present, but the present inventor believes that it is caused by the high electrical resistance at the interface between the solid electrolyte layer and the electrode or mixed conduction electrode layer arranged adjacent to it. thinking.

As a result of extensive studies by the present inventors in order to solve the problem of the increase in electrical resistance in the device 20 and the resulting decrease in oxygen transmission rate, it was found that the solid electrolyte layer 11, which is a layer having oxide ion conductivity, As a layer to be arranged, the mixed conduction electrode layer 12 having oxide ion conductivity and electron conductivity is adopted, and the material constituting the solid electrolyte layer 11 and the material constituting the mixed conduction electrode layer 12 It has also been found that it is effective to uniaxially align the solid electrolyte layer 11 and the mixed conduction electrode layer 12 along the stacking direction. This makes it possible to operate the device 20 at a low temperature, or obtain a device 20 having a high oxygen transmission rate. On the other hand, even if the material constituting the solid electrolyte layer 11 and/or the material constituting the mixed conduction electrode layer 12 is non-oriented, or the crystals of both layers are oriented, does not match the lamination direction, the electrical resistance at the interface between the solid electrolyte layer 11 and the mixed conduction electrode layer 12 increases, resulting in high oxide ion conductivity. It doesn't matter.

In order to uniaxially orient both the material forming the solid electrolyte layer 11 and the material forming the mixed conduction electrode layer 12 along the stacking direction, for example, the solid electrolyte layer 11 serving as the substrate is heated at 300° C. to 700° C. While heating to ° C., using a physical vapor deposition method, a chemical vapor deposition method, etc., in an atmosphere in which the oxygen partial pressure is controlled, a thin film of the mixed conduction electrode layer 12 is formed on the solid electrolyte layer 11, and locally Epitaxial growth is sufficient. Atomic layer deposition (ALD) can also be used to form a uniaxially oriented thin film of the mixed conducting electrode layer 12 on the solid electrolyte layer 11 . However, it is not limited to these methods.

Whether or not the material forming the solid electrolyte layer 11 and the material forming the mixed conduction electrode layer 12 are both uniaxially oriented can be determined by cross-sectional observation of the bonding interface with a TEM (transmission electron microscope). The lattice constants and interplanar spacings of the solid electrolyte layer 11 and the mixed conduction electrode layer 12 can be calculated from diffraction patterns obtained by performing X-ray diffraction measurement while vibrating.

From the viewpoint of obtaining a higher oxide ion conductivity, both the c-axis of the material forming the solid electrolyte layer 11 and the c-axis of the material forming the mixed-conducting electrode layer 12 are aligned with the solid electrolyte layer 11 and the mixed-conducting electrode layer 12. It is preferably oriented along the stacking direction with the electrode layer 12 . Here, the expression that the c-axis is oriented along the stacking direction means that the direction in which the c-axis extends in each crystal of the polycrystalline solid electrolyte matches the direction in which the layers are stacked. say.

The solid electrolyte layer 11 is a conductor in which oxide ions serve as carriers. A polycrystalline material is used as the solid electrolyte forming the solid electrolyte layer 11 . Examples of such materials include various materials hitherto known as materials having oxide ion conductivity. Examples include yttria-stabilized zirconium (YSZ) and lanthanum gallate (LaGaO ₃ ).

In particular, it is preferable to use a lanthanum oxide as the material for forming the solid electrolyte layer 11, because the oxide ion conductivity is further increased. Examples of lanthanum oxides include composite oxides containing lanthanum and gallium, composite oxides obtained by adding strontium, magnesium, cobalt, or the like to the composite oxides, and composite oxides containing lanthanum and molybdenum. In particular, it is preferable to use an oxide ion conductive material comprising a composite oxide of lanthanum and silicon because of its high oxide ion conductivity.

Examples of composite oxides of lanthanum and silicon include apatite-type composite oxides containing lanthanum and silicon. The apatite-type composite oxide contains lanthanum, which is a trivalent element, silicon, which is a tetravalent element, and O, and has a composition of La _x Si ₆ O _1.5x+12 (X is a number of 8 or more and 10 or less represents.) is preferable from the viewpoint of high oxide ion conductivity. When this apatite-type composite oxide is used as the solid electrolyte layer 11 , it is preferable to align the c-axis with the thickness direction of the solid electrolyte layer 11 . The most preferred composition of this apatite-type composite oxide is La _9.33 Si ₆ O ₂₆ . This composite oxide can be produced, for example, according to the method described in JP-A-2013-51101.

Another example of the material forming the solid electrolyte layer 11 is a composite oxide represented by the general formula (1): _A9.33+x [T6.00 _{- yMy} ] _O26.0+z . This composite oxide also has an apatite structure. A in the formula is one or more elements selected from the group consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Be, Mg, Ca, Sr and Ba. T in the formula is an element containing Si or Ge or both. M in the formula is one or more elements selected from the group consisting of B, Ge, Zn, Sn, W and Mo. From the viewpoint of enhancing c-axis orientation, M is preferably one or more elements selected from the group consisting of B, Ge and Zn.

From the viewpoint of increasing the degree of orientation and oxide ion conductivity, x in the formula is preferably −1.00 or more and 1.00 or less, more preferably 0.00 or more and 0.70 or less, and 0 0.45 or more and 0.65 or less is more preferable. In the formula, y is preferably 0.40 or more and 3.00 or less, more preferably 0.40 or more and 2.00 or less, from the viewpoint of filling the T element position in the apatite crystal lattice, and 0.40 or more and 3.00 or less. It is more preferably 40 or more and 1.00 or less. z in the formula is preferably -3.00 or more and 2.00 or less, and -2.00 or more and 1.50 or less from the viewpoint of maintaining electrical neutrality in the apatite crystal lattice. is more preferable, and more preferably -1.00 or more and 1.00 or less.

In the above formula, the ratio of the number of moles of A to the number of moles of M, in other words, (9.33+x)/y in the above formula is 3.00 or more 26 from the viewpoint of maintaining the spatial occupation rate in the apatite crystal lattice. 0.0 or less, more preferably 6.20 or more and 26.0 or less, and even more preferably 12.00 or more and 16.0 or less.

Among the composite oxides represented by the general formula (1), a composite oxide in which A is lanthanum, that is, a composite oxide represented by La _9.33+x [T _{6.00-y My} ]O _26.0+z Use is preferable from the viewpoint of further increasing the oxide ion conductivity. Specific examples of _the composite oxide represented by La9.33 _+x [ _{T6.00- yMy} ]O26.0 _+z include _La9.33+x ( _Si4.70B1.30 ) _O26.0+z , _La9.33+x ( _{Si4.70 Ge1.30} ) _O26.0+z , _La9.33+x ( _Si4.70Zn1.30 ) _O26.0+z , _{La9.33 +x} ( _Si4.70W1.30 ) _O26.0 + _z , _{La9.33+x ( Si4.70Sn1.30} )O26 _{. 0 +x} , La9.33 _+x ( _Ge4.70B1.30 ) _{O26.0+z ,} and the like. The composite oxide represented by the general formula (1) can be produced, for example, according to the method described in International Publication WO2016/111110.

From the viewpoint of effectively reducing the electrical resistance of the solid electrolyte assembly 10, the thickness of the solid electrolyte layer 11 is preferably 10 nm or more and 1000 μm or less, more preferably 50 nm or more and 700 μm or less, and 100 nm or more and 500 μm or less. is more preferable. The thickness of the solid electrolyte layer 11 can be measured using, for example, a stylus profilometer or an electron microscope.

The mixed conducting electrode layer 12 is made of a material having oxide ion conductivity and electronic conductivity. In particular, the mixed conduction electrode layer 12 is preferably made of a material having catalytic activity. The term "catalytic action" as used herein refers to the action of reducing oxygen molecules (O ₂ ) to oxide ions (O ²⁻ ) or the action of oxidizing oxide ions (O ²⁻ ) to oxygen molecules (O ₂ ). is. Examples _of such materials include (La,Sr)MnO ₃ , (La,Sr)CoO ₃ , (La,Sr) ₍ Co, Fe) _O3 and the like.

In the solid electrolyte assembly 10, both the material forming the mixed conducting electrode layer 12 and the material forming the above-described solid electrolyte layer 11 are aligned in the stacking direction of the solid electrolyte layer 11 and the mixed conducting electrode layer 12. The uniaxial orientation along the two layers 11 and 12 reduces the electrical resistance at the interface. From the viewpoint of making this advantage more conspicuous, it is advantageous to achieve lattice matching of the plane perpendicular to the orientation direction at the interface between both layers 11 and 12 . For example, when the c-axes of the materials forming the layers 11 and 12 are oriented along the stacking direction, it is preferable that lattice matching be achieved on the plane orthogonal to the c-axes. In this case, either the a-axis or b-axis lattice constant or the interplanar spacing of the mixed conduction electrode layer 12 should match that of the solid electrolyte layer 11 . Furthermore, even if the solid electrolyte layer 11 and the mixed conduction electrode layer 12 are not aligned, by heating the solid electrolyte assembly 10, a lattice orthogonal to the orientation direction of the solid electrolyte layer 11 can be obtained. Depending on the constant or spacing, the lattice constant or spacing of the mixed conducting electrode layer 12 can be matched, thereby allowing uniaxially oriented crystals to grow. From this point of view, when the lattice constant of the plane perpendicular to the c-axis of the material constituting the solid electrolyte layer 11 is a, and the interplanar spacing at (010) of the mixed conduction electrode layer 12 is d, a is 9.28 Å or more. It is preferably 9.84 Å or less. Further, d is preferably 4.54 Å or more and 5.04 Å or less, more preferably 4.60 Å or more and 4.97 Å or less, and even more preferably 4.64 Å or more and 4.92 Å or less.

The lattice constant and interplanar spacing d of the solid electrolyte layer 11 and the mixed conducting electrode layer 12 are the diffraction peaks obtained by performing X-ray diffraction measurement while shaking after bonding the mixed conducting electrode layer 12 to the solid electrolyte layer 11. calculated from The X-ray diffraction measurement conditions at that time were as follows: Cu-Kα ray, diffraction angle (2θ/θ) 10° to 140°, tilt angle (χ oscillation) −5° to 45°, in-plane rotation (φ oscillation ) was 0 to 360°.

Furthermore, if the type and composition ratio of the elements contained in the sample are known, the lattice constant a and interplanar spacing d can be calculated based on the diffraction data of standard materials such as ICSD (Inorganic Crystal Structure Database). can also For example, when the crystal form of the solid electrolyte layer 11 is hexagonal and the lattice constant a is 9.60 Å, the interplanar spacing between the (110) planes of the solid electrolyte layer 11 is 4.80 Å. When the (010) interplanar spacing of the mixed conducting electrode layer 12 is d=4.70 Å, the lattice mismatch of the plane perpendicular to the c-axis is as low as 2.2%. It is considered that the electrode layer 12 is epitaxially grown locally.

At the interface between the solid electrolyte layer 11 and the mixed conducting electrode layer 12, the material forming the mixed conducting electrode layer 12 is preferably a perovskite oxide from the viewpoint of achieving lattice matching of the plane perpendicular to the orientation direction. . In particular, when the material forming the solid electrolyte layer 11 is represented by the general formula (1) described above, and the material forming the mixed conducting electrode layer 12 is a perovskite-type oxide, the lattice matching is successful. can plan well. In this case, it is preferable that the space group of the perovskite-type oxide is R-3c, since lattice matching can be achieved more successfully.

In particular, it is preferable to use the material represented by the general formula (2): ABO ₃ as the material constituting the mixed conducting electrode layer 12 from the viewpoint of further improving the oxide ion conductivity. In the formula, A is preferably one or more metal elements selected from, for example, La, Sr, Ba, and Ca, and a particularly preferred metal element is at least one of La and Sr. For B, for example, one or more metal elements selected from Co, Ni, Mn, Cr, Ti, Fe, and Cu are preferably used, and particularly preferred metal elements are at least one of Co and Ni. Seeds. In particular, the material represented by general formula (2) is preferably a composite oxide containing La, Sr, Co and Ni.

Among the composite oxides represented by the general formula (2), those represented by La _0.6 Sr _0.4 Co _0.9 Ni _0.1 O _3-δ are particularly preferred.

The mixed conduction electrode layer 12 made of the composite oxide represented by the general formula (2) can be formed on one surface of the solid electrolyte layer 11 using various thin film formation methods, for example. Thin film formation methods include physical vapor deposition and chemical vapor deposition, among which physical vapor deposition can more successfully form mixed conduction electrode layer 12 . Among the physical vapor deposition methods, it is particularly preferable to use the PLD (Pulsed Laser Deposition) method.

As a result of studies by the present inventors, it has been found that the mixed conduction electrode layer 12 can effectively reduce the electric resistance with the solid electrolyte layer 11 if it has a predetermined thickness. Specifically, the thickness along the lamination direction of the mixed conduction electrode layer 12 joined to the solid electrolyte layer 11 is preferably 80 nm or more, more preferably 100 nm or more, and preferably 100 nm or more and 1000 nm or less. More preferred. The thickness of the mixed conduction electrode layer 12 can be measured with a stylus profilometer or an electron microscope.

The metal electrode 13 formed on the opposite side of the mixed conduction electrode layer 12 with the solid electrolyte layer 11 interposed therebetween has advantages such as being easy to form and having high catalytic activity. preferably configured. Examples of platinum group elements include platinum, ruthenium, rhodium, palladium, osmium and iridium. These elements can be used singly or in combination of two or more. A cermet containing a platinum group element can also be used as the metal electrode 13 .

The solid electrolyte assembly 10 and device 20 of the embodiment shown in FIG. 1 can be suitably manufactured, for example, by the method described below. First, the solid electrolyte layer 11 is manufactured by a known method. For production, for example, the methods described in the above-mentioned Japanese Patent Application Laid-Open No. 2013-51101 and International Publication WO2016/111110 can be adopted.

Next, a mixed conducting electrode layer 12 is formed on one of the two surfaces of the solid electrolyte layer 11 . For example, the PLD method described above can be used to form the mixed conduction electrode layer 12 . Specifically, the material constituting the solid electrolyte layer 11 and the material constituting the mixed conduction electrode layer 12 are both uniaxially oriented along the stacking direction of the solid electrolyte layer 11 and the mixed conduction electrode layer 12. In order to achieve this, the solid electrolyte layer 11 may be heated to a predetermined temperature when the mixed conduction electrode layer 12 is formed on one surface of the solid electrolyte layer 11 using the PLD method described above. It is preferable to set the heating temperature to, for example, 600° C. or higher and 700° C. or lower from the viewpoint of more successful uniaxial orientation.
After forming the mixed conducting electrode layer 12 in this manner, the metal electrode 13 is formed on the surface of the solid electrolyte layer 11 opposite to the surface on which the mixed conducting electrode layer 12 is formed. For forming the metal electrode 13, for example, a paste containing particles of a platinum group metal is used. The paste is applied to the surface of the solid electrolyte layer 11 to form a coating film, and the coating film is fired to form a porous electrode. The firing conditions can be a temperature of 600° C. or more and a time of 30 minutes or more and 120 minutes or less. The atmosphere can be an oxygen-containing atmosphere such as air.

The intended solid electrolyte assembly 10 and device 20 are obtained by the above method. The device 20 thus obtained is suitably used as, for example, an oxygen-permeable device, an oxygen sensor, or a solid electrolyte fuel cell by utilizing its high oxide ion conductivity. In whatever application the device 20 is used, it is advantageous to use the mixed conducting electrode layer 12 as the cathode, ie, as the pole where the reduction reaction of oxygen gas takes place. For example, when the device 20 is used as an oxygen permeable element, the metal electrode 13 is connected to the anode of a direct current power source, and the mixed conducting electrode layer 12 is connected to the cathode of the direct current power source. 13 is applied with a predetermined DC voltage. As a result, oxygen receives electrons on the mixed conduction electrode layer 12 side to generate oxide ions. The generated oxide ions move through the solid electrolyte layer 11 and reach the metal electrode 13 . The oxide ions reaching the metal electrode 13 release electrons and become oxygen gas. Such a reaction enables the solid electrolyte layer 11 to allow oxygen gas contained in the atmosphere on the side of the mixed conduction electrode layer 12 to permeate through the solid electrolyte layer 11 to the side of the electrode 13 . Note that, if necessary, a collector layer made of a conductive material such as platinum may be formed on at least one of the surface of the mixed conduction electrode layer 12 and the surface of the metal electrode 13 .

The voltage to be applied is preferably set to 0.1 V or more and 4.0 V or less from the viewpoint of increasing the permeation amount of oxygen gas. When a voltage is applied between both electrodes, it is preferable that the oxide ion conductivity of the solid electrolyte layer 11 is sufficiently high. For example, the oxide ion conductivity is preferably 1.0×10 ⁻³ S/cm or more in terms of conductivity. Therefore, it is preferable to keep the solid electrolyte layer 11 or the entire device 20 at a predetermined temperature. Although this holding temperature depends on the material of the solid electrolyte layer 11, it is generally preferable to set it in the range of 300° C. or higher and 600° C. or lower. By using the device 20 under this condition, the oxygen gas contained in the atmosphere on the side of the mixed conducting electrode layer 12 can permeate through the solid electrolyte layer 11 to the side of the metal electrode 13 .

When the device 20 is used as a limiting current oxygen sensor, the oxide ions generated on the mixed conduction electrode layer 12 side move through the solid electrolyte layer 11 to the metal electrode 13 side, resulting in current occurs. Since the current value depends on the oxygen gas concentration on the mixed conduction electrode layer 12 side, the oxygen gas concentration on the mixed conduction electrode layer 12 side can be measured by measuring the current value.

Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. For example, in the above-described embodiment, the mixed conduction electrode layer 12 is arranged only on one surface of the solid electrolyte layer 11, but instead of this, the mixed conduction electrode layer 12 is provided for the solid electrolyte layer 11 as described in the examples described later. A separate mixed conducting electrode layer 12 may be disposed on the surface facing 12 . When such a mixed conducting electrode layer 12 is arranged on the surface of the solid electrolyte layer 11 facing the mixed conducting electrode layer 12, each mixed conducting electrode layer 12 may be the same or different. good too. In this case, the material forming the solid electrolyte layer 11, the material forming one of the mixed conducting electrode layers 12, and the material forming the other mixed conducting electrode layer 12 are all arranged along the stacking direction. It is preferably uniaxially oriented.

EXAMPLES The present invention will be described in more detail below with reference to examples. However, the scope of the invention is not limited to such examples. "%" means "% by mass" unless otherwise specified.

[Example 1]
In this example, the solid electrolyte assembly 10 and the device 20 having the structure shown in FIG. 1 were manufactured according to the following steps (1) to (4).
(1) Production of Solid Electrolyte Layer 11 Powdered La ₂ O ₃ and powdered SiO ₂ were blended at a molar ratio of 1:1, ethanol was added, and the mixture was mixed in a ball mill. The mixture was dried, ground in a mortar, and fired at 1650° C. for 3 hours in an air atmosphere using a platinum crucible. Ethanol was added to this baked product, and the mixture was pulverized with a ball mill to obtain a baked powder. This sintered powder was placed in a molding machine of 20 mm in diameter and pressed from one direction for uniaxial molding. Furthermore, cold isostatic pressing (CIP) was performed at 700 MPa for 1 minute to form pellets. This pellet-shaped molded body was heated at 1600° C. for 3 hours in the atmosphere to obtain a pellet-shaped sintered body. When this sintered body was subjected to powder X-ray diffraction measurement and chemical analysis, it was confirmed to have a structure of La ₂ SiO ₅ .

800 mg of the obtained pellets and 140 mg of B ₂ O ₃ powder were placed in a sagger with a lid and heated in the air at 1550° C. (atmospheric temperature in the furnace) for 50 hours using an electric furnace. By this heating, B ₂ O ₃ vapor is generated in the sagger, and after the B ₂ O ₃ vapor and the pellet are reacted, annealing is further performed in the air at 1600° C. to form the desired solid electrolyte layer. 11 was obtained. In _La9.33+x [Si6.00 _{-yBy ]} O26.0 _+z , this solid electrolyte layer 11 has x=0.57, y=0.96, and z=0.37, and the molar ratio of La to B is was 10.03 (hereinafter, this compound is abbreviated as "LSBO"). The oxide ion conductivity at 500° C. was 4.22×10 ⁻² S/cm. The thickness of the solid electrolyte layer 11 was 350 μm. Observation with a polarizing microscope confirmed that the solid electrolyte layer 11 was composed of a polycrystal.

(2) Production of mixed conduction electrode layer 12 Mixed conduction electrode layer 12 was formed on one surface of solid electrolyte layer 11 produced in (1) by the following procedure.
The solid electrolyte layer 11 and target La _0.6 Sr _0.4 Co _0.9 Ni _0.1 O _3-δ (hereinafter this substance is abbreviated as “LSCNO”) are set in the chamber of the PLD device. Then, while evacuating the inside of the chamber, heating was performed in advance at 600°C. After that, oxygen is introduced into the chamber, the atmosphere is controlled to 5.5×10 ⁻⁴ torr, and then a KrF excimer laser is used to deposit evaporated particles generated by laser ablation on the solid electrolyte layer 11 . Thus, a mixed conduction electrode layer 12 was formed. TEM cross-sectional observation of the interface with the solid electrolyte layer 11 confirmed that the mixed conducting electrode layer 12 obtained in this way was composed of a polycrystalline material. In addition, the spacing between the (110) plane of the solid electrolyte layer 11 and the (010) plane of the mixed conduction electrode layer 12 is matched, and the c-axis of the material forming the solid electrolyte layer 11 and the mixed conduction electrode layer 12 are formed. It was confirmed that both the c-axes of the materials to be laminated are oriented along the stacking direction. As a result of X-ray diffraction measurement while rocking, it was confirmed that the mixed conducting electrode layer 12 was a perovskite-type oxide with a space group of R-3c. Furthermore, the interplanar spacing of the (110) plane of the solid electrolyte layer 11 calculated based on the lattice constant obtained from the diffraction pattern is 4.80 Å, and the interplanar spacing of the (010) plane of the mixed conduction electrode layer 12 is It was 4.68 Å. The lattice mismatch was 2.45%.

(3) Manufacture of Metal Electrode 13 A metal electrode 13 was formed on the surface of the solid electrolyte layer 11 manufactured in (1) opposite to the surface on which the mixed conduction electrode layer 12 was formed. A sputtering method using a platinum target was used to form the metal electrode 13 . A metal electrode 13 was obtained by annealing a platinum film formed on the surface of the solid electrolyte layer 11 opposite to the surface on which the mixed conduction electrode layer 12 was formed by sputtering at 600° C. for 1 hour. The thickness of the metal electrode 13 was 100 nm.

(4) Production of Collecting Layer A platinum paste was applied to the surfaces of the mixed conduction electrode layer 12 and the metal electrode 13 to form a coating film. These coating films were baked in the atmosphere at 600° C. for 1 hour to obtain current collecting layers.

[Example 2]
The step (2) of Example 1 was performed instead of the step (3) of Example 1 to obtain a device 20 in which the mixed conduction electrode layer 12 was arranged on each surface of the solid electrolyte layer 11 .

[Comparative Example 1]
In step (2) of Example 1, the mixed conduction electrode layer 12 was deposited at room temperature. A solid electrolyte assembly 10 and a device 20 were obtained in the same manner as in Example 1 except for this. In this solid electrolyte assembly 10, it was confirmed by X-ray diffraction measurement that the mixed conducting electrode layer 12 was not uniaxially oriented.

[Comparative Example 2]
In this comparative example, a paste containing LSCNO was applied to each surface of the solid electrolyte layer 11 obtained in the step (1) of Example 1 to form a coating film. By firing for a period of time, mixed conduction electrode layers 12 each having a thickness of 300 nm or more were formed.

[Comparative Example 3]
In this comparative example, the solid electrolyte layer 11 was formed by performing the step (1) of the first embodiment. Then, the step (3) of the same example was performed, and a metal electrode 13 made of platinum was formed on the solid electrolyte layer 11 instead of the mixed conduction electrode layer 12 of the first example. A metal electrode 13 made of platinum was also formed on the opposite surface. The thickness of the metal electrode 13 was 100 nm or more.

〔evaluation〕
The oxygen permeation rates of the devices obtained in Examples and Comparative Examples were measured by the following method. Also, the presence or absence of crystal orientation in the solid electrolyte layer 11 and the mixed conduction electrode layer 12 was confirmed by X-ray diffraction measurement. The results are shown in Table 1 below.

[Measurement of oxygen transmission rate]
Measurements were made at 600°C. Air is supplied to the mixed conduction electrode layer 12 side of the device, and N ₂ gas is supplied to the metal electrode 13 side at 200 ml/min, respectively, and a DC voltage of 1.0 V is applied between the mixed conduction electrode layer 12 and the metal electrode 13. bottom. An oxygen concentration meter was attached to the metal electrode 13 side, and the change in oxygen concentration in the atmosphere on the metal electrode 13 side before and after voltage application was measured to calculate the oxygen permeation rate (ml·cm ⁻² ·min ⁻¹ ). Further, the oxygen transmission efficiency was calculated by the formula [oxygen permeation amount measured with an oxygen concentration meter]/[oxygen permeation amount measured from the current density]×100.

As is clear from the results shown in Table 1, the solid electrolyte assembly and the device comprising the same obtained in each example have a high oxygen permeation rate and a high oxygen permeation efficiency.

According to the present invention, a solid electrolyte assembly having a high oxygen permeation rate is provided. By using this solid electrolyte assembly, low-temperature operation of the device and an increase in oxygen supply can be achieved.

Claims (10)

A polycrystalline solid electrolyte having oxide ion conductivity and a mixed conducting electrode layer laminated in contact with the solid electrolyte and having oxide ion conductivity and electronic conductivity are joined,
Both the c-axis of the material forming the solid electrolyte and the c-axis of the material forming the mixed conducting electrode layer are oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer. cage,
A solid electrolyte assembly, wherein the solid electrolyte is an apatite-type composite oxide . 2. The solid electrolyte assembly according to claim 1, wherein said mixed conducting electrode layer is polycrystalline. The solid electrolyte has the general formula: A _9.33+x [T _6.00−y M _y ]O _26.0+z (wherein A is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy , Be, Mg, Ca, Sr and Ba, wherein T is an element containing Si or Ge or both, and M in the formula is , B, Ge, Zn, Sn, W and Mo are one or two or more elements selected from the group consisting of), where x is a number of -1.00 or more and 1.00 or less , where y is a number of 0.40 or more and 3.00 or less, z in the formula is a number of -3.00 or more and 2.00 or less, and the number of moles of A to the number of moles of M 3. The solid electrolyte assembly according to claim 1, comprising a composite oxide having a ratio of 3.00 or more and 26.0 or less. A polycrystalline solid electrolyte having oxide ion conductivity and a mixed conducting electrode layer laminated in contact with the solid electrolyte and having oxide ion conductivity and electronic conductivity are joined,
Both the material forming the solid electrolyte and the material forming the mixed conducting electrode layer are uniaxially oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer,
A solid electrolyte assembly, wherein the (010) interplanar spacing of the mixed conduction electrode layer is 4.54 Å or more and 5.04 Å or less. A polycrystalline solid electrolyte having oxide ion conductivity and a mixed conducting electrode layer laminated in contact with the solid electrolyte and having oxide ion conductivity and electronic conductivity are joined,
Both the material constituting the solid electrolyte and the material constituting the mixed conducting electrode layer are uniaxially oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer,
the mixed conduction electrode layer is a perovskite oxide;
A solid electrolyte assembly, wherein the space group of the perovskite oxide is R-3c. A polycrystalline solid electrolyte having oxide ion conductivity and a mixed conducting electrode layer laminated in contact with the solid electrolyte and having oxide ion conductivity and electronic conductivity are joined,
Both the material forming the solid electrolyte and the material forming the mixed conducting electrode layer are uniaxially oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer,
A solid electrolyte assembly, wherein the mixed conducting electrode layer is a composite oxide containing La, Sr, Co and Ni. 7. The solid electrolyte assembly according to any one of claims 1 to 6 , wherein the thickness of said mixed conducting electrode layer joined to said solid electrolyte along said stacking direction is 100 nm or more. The solid electrolyte assembly according to any one of claims 1 to 7 , wherein a metal electrode is arranged on a surface of the solid electrolyte assembly opposite to the surface on which the mixed conduction electrode layer is arranged. A polycrystalline solid electrolyte having oxide ion conductivity and a mixed conducting electrode layer laminated in contact with the solid electrolyte and having oxide ion conductivity and electronic conductivity are joined,
Both the material forming the solid electrolyte and the material forming the mixed conducting electrode layer are uniaxially oriented along the stacking direction of the solid electrolyte and the mixed conducting electrode layer,
A solid electrolyte assembly, wherein a mixed conduction electrode layer that is the same as or different from the mixed conduction electrode layer is arranged on the surface opposite to the surface on which the mixed conduction electrode layer is arranged in the solid electrolyte assembly. 10. The solid electrolyte assembly according to any one of claims 1 to 9 , which is used as an oxygen permeation device, an oxygen sensor, or a solid electrolyte fuel cell.

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