Laminate

Abstract

To improve an oxide ion conductivity in a device having a solid electrolyte.SOLUTION: A laminate 10 includes an anode 13, a cathode 12 and a solid electrolyte layer 11 positioned therebetween. The laminate further includes a cathode side interlayer 15 between the cathode 12 and the solid electrolyte layer 11. In a material composing the cathode side interlayer 15, if an electric field of 1.0×107 to 1.0×108 V / m is applied between the anode 13 and the cathode 12 under a temperature condition of 600°C, a lattice volume increments by a range of 0.3% to 2.0% in comparison to a case when no electric field is applied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate having a solid electrolyte. The laminate of the present invention is used in various fields by utilizing its ionic conductivity. [Background technology]

[0002] Various oxide-ion conductive solid electrolytes are known. Such solid electrolytes are used in various fields, for example, as oxygen permeation elements, electrolytes for fuel cells, and gas sensors. In particular, there is an increasing need for oxygen concentrators that can supply high-concentration oxygen on-site in preparation for emergencies such as natural disasters and infectious disease pandemics. To achieve this, it is necessary to further improve the oxide-ion conductivity between the solid electrolyte and the electrode assembly and to improve the performance of the device. For example, Patent Documents 1 and 2 describe electrolyte-electrode assemblies that use apatite-type oxide as the electrolyte. The electrolyte is a single crystal or c-axis oriented La X SiO 1.5X+12 The electrode is made of a composite oxide of lanthanum and silicon, represented by the formula: X Sr 1-X Co Y Fe 1-Y O α Ya, Ba X Sr 1-X Co Y Fe 1-Y O α Ya, Sm X Sr 1-X CoO α An intermediate layer is provided between the electrode and the electrolyte. The intermediate layer is made of cerium oxide in which samarium, yttrium, gadolinium, or lanthanum is dissolved.

[0003] Patent Documents 3 and 4 describe techniques for disposing an intermediate layer between the solid electrolyte and the anode or cathode in a laminate. Patent Document 3 describes the intermediate layer as being made of cerium oxide containing lanthanum and a rare earth metal (excluding lanthanum and cerium). Patent Document 4 describes the intermediate layer as being made of cerium oxide containing one or more elements selected from the group consisting of samarium, yttrium, gadolinium, and lanthanum, or bismuth oxide or a composite oxide of bismuth, lanthanum, gadolinium, or yttrium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-176675 [Patent Document 2] US Patent Application Publication No. 2010 / 0285391 [Patent Document 3] International Publication No. 2019 / 203219 Brochure [Patent Document 4] International Publication No. 2019 / 235383 Brochure Summary of the Invention [Problem to be solved by the invention]

[0005] Although various devices using oxide-ion conductive solid electrolytes have been proposed as described in Patent Documents 1 to 4, there is a demand for further improving the oxide-ion conductivity of the entire device. In particular, as described in Patent Documents 3 and 4, it is necessary to further improve the oxide-ion conductivity of the intermediate layer in order to smoothly exchange oxide ions between the solid electrolyte and the electrodes in the laminate.

[0006] Therefore, an object of the present invention is to further improve the oxide ion conductivity of a device including a solid electrolyte. [Means for solving the problem]

[0007] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that a laminate having an intermediate layer, which exhibits specific behavior in response to the application of an electric field, disposed between a solid electrolyte and an electrode can improve the ionic conductivity of the entire device. In particular, it has been found that the intermediate layer disposed on the cathode side of the laminate significantly contributes to the improvement of ionic conductivity.

[0008] The present invention has been made based on the above findings, and provides a laminate including a solid electrolyte layer, a cathode disposed on one surface of the solid electrolyte layer, an anode disposed on the other surface of the solid electrolyte layer, and an intermediate layer disposed between the solid electrolyte layer and the cathode, The material constituting the intermediate layer is 1.0×10 7 V / m or more 1.0×10 8 The above-mentioned problem has been solved by providing a laminate in which, when an electric field of 1000 V / m or less is applied, the lattice volume increases by 0.3% to 2.0% compared to when no electric field is applied. In this specification, if the increase rate of the lattice volume measured under any electric field strength condition in the above range falls within the above range, it is considered to fall within the scope of claim 1. [Effects of the Invention]

[0009] According to the present invention, the ionic conductivity of a device including a solid electrolyte is improved. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a cross section along the thickness direction showing one embodiment of a laminate of the present invention. [Figure 2] FIG. 2 is a graph showing the relationship between current density and lattice constant in the cathode-side intermediate layer of the laminate obtained in Example 2. [Figure 3] FIG. 3 is a graph showing the relationship between the applied voltage and the current density measured for the laminates obtained in Example 2 and Comparative Example 2. [Figure 4] FIG. 4 is a graph showing the relationship between the current density and the oxygen transmission rate in the laminate obtained in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described below based on preferred embodiments with reference to the drawings. FIG. 1 shows one embodiment of a laminate of the present invention. The laminate 10 shown in the figure includes a solid electrolyte layer 11. The solid electrolyte layer 11 is made of a material having ion conductivity. In particular, the solid electrolyte layer 11 is preferably made of a material having oxide ion conductivity at a predetermined temperature or higher. The solid electrolyte layer 11 is located between two electrodes, namely, a cathode 12 and an anode 13. The cathode 12 and the anode 13 are preferably arranged, for example, at positions facing each other with the solid electrolyte layer 11 interposed therebetween. The cathode 12 can be electrically connected to the negative electrode of a DC power supply (not shown), while the anode 13 can be electrically connected to the positive electrode of a DC power supply (not shown). Therefore, a DC voltage is applied between the cathode 12 and the anode 13.

[0012] A cathode-side intermediate layer 15 is disposed between the cathode 12 and the solid electrolyte layer 11. In Fig. 1, the cathode 12 and the cathode-side intermediate layer 15 are shown to have different sizes, but the size relationship between them is not limited to this, and for example, the cathode 12 and the cathode-side intermediate layer 15 may be the same size. Furthermore, in Fig. 1, the cathode-side intermediate layer 15 and the solid electrolyte layer 11 are shown to have the same size, but the size relationship between them is not limited to this, and for example, the solid electrolyte layer 11 and the cathode-side intermediate layer 15 may be different sizes. Furthermore, in this embodiment, an anode-side intermediate layer (not shown) may be provided between the anode 13 and the solid electrolyte layer 11. That is, an intermediate layer and an electrode may be formed on both sides of the solid electrolyte layer 11.

[0013] 1 , the cathode-side intermediate layer 15 is in direct contact with the cathode 12 and the solid electrolyte layer 11. Therefore, no layer is interposed between the cathode-side intermediate layer 15 and the cathode 12. The cathode-side intermediate layer 15 is also in direct contact with the solid electrolyte layer 11, with no layer being interposed between them. The same applies when an optional anode-side intermediate layer is provided between the anode 13 and the solid electrolyte layer 11, and the anode-side intermediate layer is in direct contact with the solid electrolyte layer 11 and the anode 13.

[0014] The cathode-side intermediate layer 15 is used to improve ion conductivity, particularly oxide ion conductivity, between the solid electrolyte layer 11 and the cathode 12 in the laminate 10. Regarding oxide ion conductivity, increasing the oxide ion conductivity of the solid electrolyte layer 11 is important for reducing the electrical resistance of the laminate 10. However, even if the solid electrolyte layer 11 is formed using a material with high oxide ion conductivity, if the oxide ion conductivity between the solid electrolyte layer 11 and the cathode 12 is low, there is a limit to how much the oxide ion conductivity of the laminate 10 as a whole can be improved. After extensive research into this issue, the present inventors have found that disposing a cathode-side intermediate layer 15 between the solid electrolyte layer 11 and the cathode 12, which exhibits specific behavior in response to the application of an electric field, can improve the oxide ion conductivity of the laminate 10 as a whole. Specifically, in the present invention, a material whose lattice volume increases when an electric field is applied, is used as the material for forming the cathode-side intermediate layer 15. The solid electrolyte layer 11 and the cathode-side intermediate layer 15 will be described below.

[0015] The solid electrolyte layer 11 is preferably an oxide ion conductor in which oxide ions serve as carriers. A single crystal or polycrystalline material is used as the solid electrolyte constituting the solid electrolyte layer 11. Using lanthanum oxide as the material constituting the solid electrolyte layer 11 is preferable because it further increases the oxide ion conductivity. Examples of lanthanum oxide include composite oxides containing lanthanum and gallium, composite oxides in which strontium, magnesium, cobalt, or the like is added to such composite oxides, and composite oxides containing lanthanum and molybdenum. In particular, it is preferable to use an oxide ion conductive material made of a composite oxide of lanthanum and silicon because of its high oxide ion conductivity.

[0016] The composite oxide of lanthanum and silicon includes, for example, an apatite-type composite oxide 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 SiO 1.5x+12 (X represents a number of 8 or more and 10 or less) is preferred from the viewpoint of high oxide ion conductivity. When this apatite-type composite oxide is used as the solid electrolyte layer 11, it is preferred that the c-axis coincides with the thickness direction of the solid electrolyte layer 11. The most preferred composition of this apatite-type composite oxide is La 9.3 SiO 26 This composite oxide can be produced, for example, according to the method described in JP-A-2013-51101.

[0017] Another example of the material for forming the solid electrolyte layer 11 is a material represented by the formula (1): A 9.3+x [T 6.0-y M y ]O 26.0+zExamples of suitable composite oxides include those represented by the formula: These composite oxides also have an apatite structure. In the formula, A represents one or more elements selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Be, Mg, Ca, Sr, and Ba. In the formula, T represents an element containing Si or Ge, or both. In the formula, M represents one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Y, Zr, Ta, Nb, 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, more preferably at least one element selected from B and Zn, and even more preferably B.

[0018] In formula (1), x is preferably -1.4 or more and 1.5 or less, more preferably 0.0 or more and 0.7 or less, and even more preferably 0.4 or more and 0.6 or less, from the viewpoint of increasing the degree of orientation and oxide ion conductivity. In formula (1), y is preferably 0.0 or more and 3.0 or less, more preferably 0.4 or more and 2.0 or less, and even more preferably 0.4 or more and 1.0 or less, from the viewpoint of filling the T element position in the apatite-type crystal lattice. In formula (1), z is preferably -5.0 or more and 5.2 or less, more preferably -2.0 or more and 1.5 or less, and even more preferably -1.0 or more and 1.0 or less, from the viewpoint of maintaining electrical neutrality in the apatite-type crystal lattice.

[0019] In the above formula, the ratio of the number of moles of A to the number of moles of T, in other words, (9.3+x) / (6.0-y) in the above formula, is preferably 1.3 or more and 3.7 or less, more preferably 1.4 or more and 3.0 or less, and even more preferably 1.5 or more and 2.0 or less, from the viewpoint of maintaining the spatial occupancy rate in the apatite-type crystal lattice. 9.3+x [T 6.0-y M y ]O 26.0+zIn the formula (9.3+x) / (6.0-y), when both T and M contain only Ge, y=0.

[0020] Among the composite oxides represented by the above formula, composite oxides in which A is lanthanum, i.e., La 9.3+x [T 6.0-y M y ]O 26.0+z It is preferable to use a composite oxide represented by the formula: La 9.3+x [T 6.0-y M y ]O 26.0+z Specific examples of composite oxides represented by the formula include La 9.3+x (Si 4.7 B 1.3 )O 26.0+z , La 9.3+x (Si 4.7 Ge 1.3 )O 26.0+z , La 9.3+x (Si 4.7 Zn 1.3 )O 26.0+z , La 9.3+x (Si 4.7 W 1.3 )O 26.0+z , La 9.3+x (Si 4.7 Sn 1.3 )O 26.0+x , La 9.3+x (Ge 4.7 B 1.3 )O 26.0+z The composite oxide represented by the above formula can be produced, for example, according to the method described in International Publication WO2016 / 111110.

[0021] As another example of the material constituting the solid electrolyte layer 11, it is also preferable to use at least one material selected from the group consisting of yttrium-stabilized zirconia (hereinafter referred to as "YSZ"), samarium-doped ceria (hereinafter referred to as "SDC"), gadolinium-doped ceria (hereinafter referred to as "GDC"), lanthanum gallate, and yttrium-doped bismuth oxide (hereinafter referred to as "YBO").

[0022] As the YSZ, it is preferable to use one in which the ratio of the number of moles of yttrium to the total number of moles of zirconium (Zr) and yttrium (Y) (Y / (Zr+Y)) is 0.05 or more and 0.15 or less. As the SDC, it is preferable to use one in which the ratio of the number of moles of samarium to the total number of moles of cerium (Ce) and samarium (Sm) (Sm / (Ce+Sm)) is 0.10 or more and 0.25 or less. As the GDC, it is preferable to use one in which the ratio of the number of moles of gadolinium to the total number of moles of cerium (Ce) and gadolinium (Gd) (Gd / (Ce+Gd)) is 0.10 or more and 0.25 or less. As the YBO, it is preferable to use one in which the ratio of the number of moles of yttrium to the total number of moles of bismuth (Bi) and yttrium (Y) (Y / (Bi+Y)) is 0.10 or more and 0.30 or less.

[0023] The thickness of 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 even more preferably 100 nm or more and 500 μm or less, from the viewpoint of effectively reducing the electrical resistance of laminate 10. The thickness of solid electrolyte layer 11 can be measured using, for example, a stylus profilometer or an electron microscope.

[0024] Next, the cathode-side intermediate layer 15 will be described. As described above, the cathode-side intermediate layer 15 is used for the purpose of improving oxide ion conductivity between the solid electrolyte layer 11 and the cathode 12. As a result of investigations by the present inventors, it has been found that the oxide ion conductivity is improved when a material constituting the cathode-side intermediate layer 15 is used whose lattice volume increases when an electric field is applied to the material. The increase in lattice volume is caused by an increase in the lattice constant. In other words, it is believed that the lattice constant of the material constituting the cathode-side intermediate layer 15 increases when an electric field is applied to it, which in turn improves the oxide ion conductivity.

[0025] The lattice volume is measured under a temperature condition of 600° C. Specifically, the laminate 10 is placed in an air atmosphere at 600° C., the cathode 12 of the laminate 10 is connected to a negative DC power supply, and the anode 13 is connected to a positive DC power supply, and a lattice volume of 1.0×10 7 V / m or more 1.0×10 8 When an electric field of 1.1 × 10 V / m or less is applied, 7 V / m or more 3.0×10 7 V / m or less, more preferably 1.5×10 7 V / m or more 2.1×10 7 High-temperature X-ray diffraction measurement is performed with an electric field of 0.1 V / m or less applied to measure the lattice constant of the material constituting the cathode-side intermediate layer 15. Based on the measured lattice constant value, the lattice volume V E Furthermore, the laminate 10 is placed in an air atmosphere at 600°C, and high-temperature X-ray diffraction measurement is performed without applying an electric field to the laminate 10 to measure the lattice constant of the material constituting the cathode-side intermediate layer 15. Based on the measured lattice constant value, the lattice volume V0 is calculated. Then, the lattice volume V with an electric field applied is calculated. E The volume increase rate (%) is used to evaluate the extent to which the lattice volume V0 has increased compared to the lattice volume V0 when no electric field is applied. E The volume increase rate is defined as (-V0) / (V0) × 100. A laminate 10 having a cathode-side intermediate layer 15 made of a material with a volume increase rate of 0.3% or more will have high oxide ion conductivity as a whole. To make this advantage even more pronounced, the volume increase rate is preferably 0.5% or more, and more preferably 0.7% or more. The value of the electric field is determined by applying a DC voltage between the cathode 12 and the anode 13 as V DC (V), and the thickness of the cathode side intermediate layer 15 is T C (m), V DC / T C is defined as: The upper limit of the volume increase rate is preferably 2.0% or less, more preferably 1.9% or less, and even more preferably 1.8% or less, from the viewpoint of maintaining the crystal structure of the material constituting the cathode-side intermediate layer 15 and maintaining the oxide ion conductivity and the laminate interface of the entire laminate 10. Considering the above, the volume increase rate of the material constituting the cathode side intermediate layer 15 is 0.3% to 2.0%, preferably 0.5% to 1.9%, and more preferably 0.7% to 1.8%.

[0026] The volume increase rate may be satisfied within any of the ranges of the electric field, and it is not necessary that the volume increase rate be satisfied within the entire range of the electric field.

[0027] From the viewpoint of achieving the above-mentioned volume increase rate, it is preferable to use a material that has a fluorite crystal structure as the material that constitutes the cathode-side intermediate layer 15. Furthermore, from the viewpoint of achieving the above-mentioned volume increase rate, it is also preferable that the material constituting the cathode-side intermediate layer 15 contains a rare earth element in addition to having the above-mentioned crystal structure. In particular, it is preferable that the material constituting the cathode-side intermediate layer 15 is composed of cerium oxide containing lanthanum and a rare earth element (excluding lanthanum and cerium; hereinafter also referred to as "Ln") (hereinafter also referred to as "La-LnDC").

[0028] In La-LnDC, lanthanum and rare earth elements other than cerium are contained in the matrix cerium oxide (CeO2) in a solid solution (doped) form. The doped rare earth elements usually exist in the cerium oxide crystal lattice by substituting for the cerium site. Lanthanum exists in the cerium oxide solid solution form. That is, lanthanum can exist in the cerium oxide crystal lattice by substituting for the cerium site, or it can exist at the grain boundaries of the rare earth-doped cerium oxide.

[0029] In La-LnDC, examples of rare earth elements doped into cerium oxide include samarium, gadolinium, yttrium, erbium, ytterbium, and dysprosium. These rare earth elements may be used singly or in combination. In particular, the cathode-side intermediate layer 15 preferably contains cerium oxide containing lanthanum and samarium or gadolinium, since this can further enhance the oxide ion conductivity of the entire laminate 10.

[0030] Lanthanum is contained in La-LnDC for the purpose of improving the oxide ion conductivity of the entire laminate 10. For this purpose, it is preferable that the value of La / Ce, which is the atomic ratio of La to Ce in La-LnDC, is 0.3 to 1.2, because this makes it easier for the lattice volume of the cathode-side intermediate layer 15 to change when an electric field is applied, thereby improving the oxide ion conductivity of the entire laminate 10. To further enhance this effect, the value of La / Ce in La-LnDC is more preferably 0.35 to 1.18, even more preferably 0.40 to 1.15, even more preferably 0.45 to 1.13, and particularly preferably 0.50 to 1.10.

[0031] The La / Ce value is measured by energy dispersive X-ray spectroscopy (EDS), electron probe microanalyzer (EPMA), etc. Furthermore, the presence of a rare earth element in cerium oxide as a solid solution can be confirmed by X-ray diffraction.

[0032] Furthermore, in the La-LnDC constituting the cathode-side intermediate layer 15, the lattice constant of La-LnDC tends to decrease as the amount of the doping element Ln increases. A smaller lattice constant of La-LnDC may hinder the improvement of the volume increase rate described above. Therefore, in the present invention, the Ln / Ce value, which is the atomic ratio of cerium to rare earth elements, is preferably 0.001 or more but less than 0.10, more preferably 0.01 or more but 0.08 or less, and even more preferably 0.02 or more but 0.06 or less. By controlling both the La / Ce value and the Ln / Ce value, the volume increase rate described above can be more easily achieved. As a result, the oxide ion conductivity of the laminate 10 as a whole can be further improved. The Ln / Ce value, like the La / Ce value, is measured by energy dispersive X-ray spectroscopy (EDS), electron probe microanalyzer (EPMA), or the like.

[0033] The inventors have found through their investigations that the thickness of the cathode-side intermediate layer 15, if it is at least a certain thickness, can effectively improve the oxide ion conductivity between the solid electrolyte layer 11 and the cathode 12. Specifically, the thickness of the cathode-side intermediate layer 15 is preferably 1 nm or more and 400 nm or less, and more preferably 5 nm or more and 350 nm or less. The thickness of the cathode-side intermediate layer 15 can be measured using a stylus profilometer or an electron microscope.

[0034] The volume change rate of the lattice volume of the cathode-side intermediate layer 15 is as described above. Regarding the lattice constant, when the material constituting the cathode-side intermediate layer 15 is a fluorite-type cubic crystal, under a temperature condition of 600°C and with no electric field applied between the cathode 12 and the anode 13, the lattice constant L0 is preferably 5.50 Å or more and 5.60 Å or less, more preferably 5.501 Å or more and 5.599 Å or less, and even more preferably 5.502 Å or more and 5.598 Å or less. On the other hand, under the temperature condition of 600°C, 1.0 × 10 6 V / m or more 2.0×10 7 Lattice constant L when an electric field of V / m or less is appliedE The degree of increase in lattice constant (L E Expressed as -L0) / L0)×100, it is preferably 0.1% or more and 1.0% or less, more preferably 0.11% or more and 0.8% or less, and even more preferably 0.12% or more and 0.5% or less.

[0035] Next, the cathode 12 and the anode 13 will be described. The cathode 12 and the anode 13 can be made of, for example, a metal material or a mixed conductive oxide having oxide ion conductivity and electronic conductivity. When the cathode 12 and the anode 13 are made of a metal material, the metal material preferably contains a platinum group element, gold, or silver, because of advantages such as high catalytic activity. Examples of platinum group elements include platinum, palladium, iridium, ruthenium, rhodium, and osmium. These elements can be used alone or in combination of two or more. Alternatively, the cathode 12 and the anode 13 can each independently be made of a cermet containing a platinum group element and an oxide having oxide ion conductivity.

[0036] On the other hand, when either the cathode 12 or the anode 13 is made of a mixed conducting oxide having oxide ion conductivity and electronic conductivity, the mixed conducting oxide is preferably ABO 3-δ Preferably, a material having a perovskite structure represented by the formula: In the formula, A represents an alkaline earth metal element, B represents a transition metal element, such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, and W, and δ is a fraction resulting from the valence and amount of A, B, and O. ABO 3-δ Various oxides having a perovskite structure represented by the formula (I) are known, and it is known that such oxides have various crystal systems, such as cubic, tetragonal, rhombohedral, and orthorhombic. Among these crystal systems, ABO oxides having a cubic perovskite structure are 3-δIt is preferable to use an oxide of this type as the cathode 12 and / or the anode 13. By forming the laminate 10 from the cathode 12 and / or the anode 13 made of such an oxide and the cathode-side intermediate layer 15 made of the above-mentioned material, the oxide ion conductivity of the laminate 10 as a whole can be further increased.

[0037] The inventors have found through their investigations that if the cathode 12 and the anode 13 have a predetermined thickness, the oxide ion conductivity of the entire laminate 10 can be more effectively increased. Specifically, the thickness of the cathode 12 and the anode 13 is preferably 100 nm or more, more preferably 500 nm or more, and even more preferably 1000 nm or more and 30000 nm or less. The thicknesses of the cathode 12 and the anode 13 can be measured using a stylus profilometer or an electron microscope.

[0038] 1 has an anode-side intermediate layer, the above description of the cathode-side intermediate layer 15 applies appropriately to details of the anode-side intermediate layer. Although the present invention does not preclude the provision of an anode-side intermediate layer in the laminate 10, providing an anode-side intermediate layer is not essential for achieving the object of the present invention.

[0039] The laminate 10 having the above configuration exhibits a high oxygen permeation rate as a whole due to the high oxide ion conductivity of the cathode-side intermediate layer 15. Specifically, the oxygen permeation rate of the laminate 10 is 3.1 ml cm at a temperature of 600°C. -2 min -1 More than 6.0ml cm -2 min -1 Preferably, it is less than 3.2 ml cm -2 min -1 More than 5.5ml cm -2 min -1 It is more preferable that the value is 3.3 ml cm or less. -2 min -1 More than 5.2ml cm -2 min -1It is more preferable that the oxygen transmission rate is as follows: The method for measuring the oxygen transmission rate will be explained in the examples below.

[0040] The laminate 10 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 the manufacturing, for example, the methods described in the above-mentioned JP 2013-51101 A and WO 2016 / 111110 can be adopted.

[0041] Next, the cathode-side intermediate layer 15 is formed on one side of the solid electrolyte layer 11. The cathode-side intermediate layer 15 can be formed by, for example, sputtering. The target used for sputtering can be manufactured, for example, by the following method: Powder of an oxide of a rare earth element (excluding lanthanum and cerium) and powder of cerium oxide are mixed using a mixer such as a mortar or a ball mill, and then fired in an oxygen-containing atmosphere to obtain raw material powder. This raw material powder is molded into the shape of a target and hot-press sintered. The sintering conditions can be a temperature of 1000°C to 1400°C, a pressure of 20 MPa to 35 MPa, and a time of 60 minutes to 180 minutes. The atmosphere can be an inert gas atmosphere such as nitrogen gas or a rare gas. The sputtering target obtained in this manner is composed of cerium oxide doped with a rare earth element (excluding lanthanum and cerium) (hereinafter also referred to as "LnDC"). The method for producing a sputtering target is not limited to this, and for example, a target-shaped compact may be fired in the air or in an oxygen-containing atmosphere. Furthermore, even when an anode-side intermediate layer is formed on the other side of the solid electrolyte layer 11, the sputtering target can be produced in the same manner as described above.

[0042] Using the target obtained in this manner, a sputtering layer is formed on one surface of the solid electrolyte layer 11 by, for example, radio frequency sputtering. The substrate temperature may be raised in advance to a range of 300 to 500°C, and sputtering may be performed while maintaining this temperature. The sputtering layer is made of LnDC. When an anode-side intermediate layer is to be formed in addition to the cathode-side intermediate layer 15, a sputtering layer may be formed on each surface of the solid electrolyte layer 11.

[0043] After sputtering is completed, the sputtered layer is annealed. The annealing is performed to thermally diffuse the lanthanum contained in the solid electrolyte layer 11 into the sputtered layer, thereby incorporating lanthanum into the LnDC that constitutes the sputtered layer. For this purpose, the annealing conditions can be a temperature of 1300°C to 1600°C for a time of 10 to 120 minutes, more preferably a temperature of 1400°C to 1600°C for a time of 10 to 90 minutes. The atmosphere can be an oxygen-containing atmosphere such as air. Other deposition methods that can be used include atomic layer deposition, ion plating, pulsed laser deposition, plating, and chemical vapor deposition.

[0044] The above-described annealing process yields a cathode-side intermediate layer composed of lanthanum-containing LnDC (La-LnDC). The cathode 12 and anode 13 are then formed, respectively. When the cathode 12 and / or anode 13 are metal electrodes, a paste containing particles of a platinum group metal, for example, can be used to form the metal electrodes. The paste is applied to the other surface of the cathode-side intermediate layer 15 and the solid electrolyte layer 11 to form a coating film, which is then fired to form the porous metal cathode 12 and anode 13. The firing conditions can be a temperature of 600°C to 900°C for a time of 30 to 120 minutes. The firing atmosphere can be an oxygen-containing atmosphere, such as air.

[0045] On the other hand, when the cathode 12 and / or the anode 13 are made of an oxide having oxide ion conductivity, for example, the above-mentioned ABO3-δ In the case of an oxide having a cubic perovskite structure represented by the formula (I), a method can be employed in which a slurry containing powder of the oxide is applied to the surface of the intermediate layer to form a coating film, and the coating film is then fired. The slurry can be obtained, for example, by adding powder of the oxide to a binder prepared by dissolving ethyl cellulose in α-terpineol, and adjusting the concentration. The concentration of the oxide powder in the slurry can be, for example, 10% by mass to 40% by mass. The firing conditions for the coating film formed by applying this slurry can be, for example, an oxygen-containing atmosphere such as air, or an inert gas atmosphere such as nitrogen gas or argon gas. The firing temperature is preferably 700°C to 1200°C, more preferably 800°C to 1100°C, and even more preferably 900°C to 1000°C. The firing time is preferably 1 hour to 10 hours, more preferably 3 hours to 8 hours, and even more preferably 5 hours to 7 hours.

[0046] The desired laminate 10 can be obtained by the above method. The laminate 10 thus obtained is suitable for use as, for example, an oxygen permeation element, a gas sensor, or a solid oxide electrolyte cell (SOEC) due to its high oxide ion conductivity. Regardless of the application of the laminate 10, it is advantageous to use La-LnDC as the cathode-side intermediate layer 15 on the cathode 12 side, where the reduction reaction of oxygen gas occurs. When the laminate 10 is used, an electric field is applied between the cathode 12 and the anode 13, changing the lattice volume of the cathode-side intermediate layer 15. This improves the oxide ion conductivity, enabling the fabrication of high-performance devices even at low temperatures below 600°C. For example, when the laminate 10 is used as an oxygen permeation element, the cathode 12 is connected to the negative electrode of a DC power supply, and the anode 13 is connected to the positive electrode of the DC power supply, and a predetermined DC voltage is applied between the cathode 12 and the anode 13. As a result, oxygen accepts electrons on the cathode 12 side, generating oxide ions. The generated oxide ions move through solid electrolyte layer 11 and reach anode 13. Upon reaching anode 13, the oxide ions release electrons and become oxygen gas. This reaction enables solid electrolyte layer 11 to allow oxygen gas contained in the atmosphere on the cathode 12 side to pass through solid electrolyte layer 11 to the anode 13 side.

[0047] The applied electric field is set to 1.0×10 7 V / m or more 1.0×10 8 V / m or less, especially 1.1×10 7 V / m or more 3.0×10 7 It is preferable to set it to 1.5×10 V / m or less. 7 V / m or more 2.1×10 7 It is more preferable to set the value to be equal to or less than V / m. When an electric field is applied between the cathode 12 and the anode 13, it is preferable that the oxide ion conductivity of the solid electrolyte layer 11 is sufficiently high. For example, the oxide ion conductivity is set to be 1.0×10 -3It is preferable that the electrical conductivity of the solid electrolyte layer 11 is 300°C or more. For this purpose, it is preferable to maintain the solid electrolyte layer 11 at a predetermined temperature. This maintained temperature depends on the material of the solid electrolyte layer 11, but is generally preferably set in the range of 300°C or more and 600°C or less. By using the laminate 10 under these conditions, oxygen gas contained in the atmosphere on the cathode 12 side can be transmitted through the solid electrolyte layer 11 to the anode 13 side.

[0048] When the laminate 10 is used as a limiting current oxygen sensor, a current is generated when oxide ions generated on the cathode 12 side move to the anode 13 side via the solid electrolyte layer 11. Since the current value depends on the oxygen gas concentration on the cathode 12 side, the oxygen gas concentration on the cathode 12 side can be measured by measuring the current value. [Example]

[0049] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0050] Example 1 In this example, the laminate 10 shown in FIG. 1 was manufactured according to the following steps (1) to (4). (1) Manufacturing of the solid electrolyte layer 11 La2O3 powder and SiO2 powder were blended in a molar ratio of 1:1, and ethanol was added and mixed in a ball mill. This mixture was dried, crushed in a mortar, and fired in a platinum crucible at 1650°C for 3 hours in an air atmosphere. Ethanol was added to this fired material, and it was then crushed in a planetary ball mill to obtain fired powder. This fired powder was placed in a 20 mm diameter molding machine and pressed from one direction to perform uniaxial molding. Further, cold isostatic pressing (CIP) at 600 MPa for 1 minute was performed to form pellets. This pellet-shaped compact was then heated in air at 1600°C for 3 hours to obtain a sintered pellet. X-ray diffraction measurement and chemical analysis of this sintered compact confirmed that it had a La2SiO5 structure.

[0051] 800 mg of the obtained pellets and 140 mg of B2O3 powder were placed in a sagger with a lid and heated in the air at 1550°C (furnace atmosphere temperature) for 50 hours using an electric furnace. This heating generated B2O3 vapor in the sagger and caused the B2O3 vapor to react with the pellets, resulting in the desired solid electrolyte layer 11. This solid electrolyte layer 11 contained La 9.3+x [Si 6.0-y B y ]O 26.0+z In this compound, x = 0.50, y = 1.17, z = 0.16, and the molar ratio of La to B was 8.43 (hereinafter, this compound will be abbreviated as "LSBO"). The oxide ion conductivity of LSBO at 600°C was 3.5 × 10 -2 The solid electrolyte layer 11 had a thickness of 350 μm.

[0052] (2) Manufacturing the Cathode-Side Intermediate Layer 15 Sm 0.2 Ce 1.8 O2 powder was placed in a 50 mm diameter molding machine and pressed from one direction to form a uniaxial compaction, followed by hot-press sintering. The sintering conditions were a nitrogen gas atmosphere, a pressure of 30 MPa, a temperature of 1200°C, and 3 hours. In this way, a sputtering target was obtained. Using this target, one side of the solid electrolyte layer 11 made of LSBO was sputtered by radio-frequency sputtering to form a sputtering layer of samarium-doped cerium oxide (hereinafter also referred to as "SDC"). The sputtering conditions were an RF power of 30 W and an argon gas pressure of 0.8 Pa. After sputtering, the mixture was annealed in air at 1500°C for 1 hour, thermally diffusing the lanthanum contained in LSBO into the sputtering layer, thereby incorporating lanthanum into the SDC. In this way, a cathode-side intermediate layer 15 made of lanthanum-doped SDC (hereinafter also referred to as "La-SDC") was produced. The cathode-side intermediate layer 15 had a thickness of 300 nm. Quantitative analysis by energy dispersive X-ray spectroscopy (EDS) revealed that the atomic ratio (at %) of La / Ce in the cathode-side intermediate layer 15 was 1.0, and the atomic ratio (at %) of Sm / Ce was 0.04.

[0053] (3) Fabrication of the cathode 12 and anode 13 A 100 nm platinum film was formed by DC sputtering on the other surface of the cathode-side intermediate layer 15 and the solid electrolyte layer 11, and then a platinum paste was applied to form a coating. These coatings were fired at 900°C for 1 hour in an air atmosphere to obtain a cathode 12 and an anode 13 made of platinum. The thickness of the cathode 12 and the anode 13 was both 20,000 nm. In this manner, the laminate 10 was produced.

[0054] Example 2 The cathode-side intermediate layer 15 was formed so that the atomic ratio of La / Ce and the atomic ratio of Sm / Ce were the values ​​shown in the following Table 1. A laminate 10 was obtained in the same manner as in Example 1 except for this.

[0055] Example 3 The cathode-side intermediate layer 15 was formed so as to have a thickness as shown in the following Table 1. Other than this, the laminate 10 was obtained in the same manner as in Example 1.

[0056] Example 4 The cathode-side intermediate layer 15 was formed so as to have a thickness as shown in the following Table 1. Other than this, the laminate 10 was obtained in the same manner as in Example 1.

[0057] Comparative Example 1 In Example 1, the annealing in step (2) was performed at 1300°C for 1 hour. Except for this, the laminate 10 was obtained in the same manner as in Example 1. The atomic ratios of La / Ce and Sm / Ce in the cathode-side intermediate layer 15 are as shown in Table 1 below.

[0058] Comparative Example 2 In this comparative example, the cathode-side intermediate layer 15 was not formed. Except for this, a laminate was obtained in the same manner as in Example 1.

[0059] [Rating 1] The laminates obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to X-ray diffraction measurement to identify the crystal structure. Furthermore, the lattice constant at 600°C was measured by high-temperature X-ray diffraction measurement. The X-ray diffraction measurement device used was a Rigaku Smart Lab. A high-temperature unit was used, and the sample temperature was set to 600°C. A graphite dome was used as the heat shield for the high-temperature unit. Platinum wires were fixed to the cathode 12 and anode 13 with platinum paste and connected to a potentiostat. A DC voltage ranging from 0.5 V to 4.7 V was applied between the cathode 12 and anode 13. The conditions for the X-ray diffraction measurement were: Cu Kα radiation (λ = 1.5418 Å), tube voltage 40 kV, tube current 30 mA, scanning method 2θ / θ, measurement range 2θ = 15° to 80°, sampling width = 0.02°, scanning speed 20° / min, collimator φ 0.2 mm, 1 measurement / 0.5 V. The same measurement as above was also carried out without applying an electric field. 7 V / m~2.1×10 7 The lattice constants of La-SDC under an applied electric field of 1000 V / m were refined from four peaks (111, 200, 220, and 311 reflections) in the XRD pattern. Furthermore, the lattice volume and volume change rate were calculated based on the lattice constant values. The lattice constant was determined using analytical software PDXL2 manufactured by Rigaku. These results are shown in Table 1.

[0060] [Rating 2] For the laminates obtained in Example 2 and Comparative Example 2, a DC voltage of 0.5 V to 6.5 V was applied in the air to measure the current density. In Example 2 and Comparative Example 2, the measurement was carried out at 600°C. A graph showing the relationship between current density and lattice constant for Example 2 is shown in Figure 2. A graph showing the relationship between applied voltage and current density for Example 2 and Comparative Example 2 is shown in Figure 3.

[0061] [Rating 3] The oxygen transmission rates of the laminates obtained in Examples 1 to 4 and Comparative Examples 1 and 2 were measured. Measurements were performed at 600°C (all Examples and Comparative Examples) and 500°C (Example 1 only). Air was supplied to the cathode side of the laminate, and nitrogen gas was supplied to the anode side. The supply rates were both 200 ml / min. Furthermore, a DC voltage of 0.5 V to 8.5 V was applied between the cathode and anode. An oxygen concentration meter was attached to the anode 13 side to measure the change in oxygen gas concentration in the atmosphere on the anode side before and after voltage application, and the oxygen permeation rate (ml cm -2 min -1 ) was calculated. The results are shown in Table 1. Furthermore, for Example 2, the relationship between the oxygen transmission rate and the current density is shown in FIG. 4, based on the measurement results of the oxygen transmission rate and the graph shown in FIG.

[0062] [Table 1]

[0063] As is clear from the results shown in Table 1, the laminates obtained in each Example exhibited a higher oxygen transmission rate at a high temperature (600°C) than those in Comparative Examples 1 and 2. Furthermore, in Example 1, a high oxygen transmission rate was obtained even at a low temperature (500°C). In other words, in Examples 1 to 4, the laminates had high oxide ion conductivity as a whole, and the electrical resistance of the laminates was reduced. In other words, when the laminates of the present invention are used, high-performance devices can be obtained even at temperatures of 600°C or lower.

[0064] 2, it can be seen that there is a correlation between the oxide ions conducted throughout the laminate 10 (i.e., the current density value) and the lattice constant of La-SDC. Specifically, the lattice constant tends to increase as the current density value increases.

[0065] 3, it can be seen that the measurement results of the oxygen transmission rate at 600°C are higher in Example 2 than in Comparative Example 2. In addition, as shown in FIG. 4, it can be seen that values ​​close to the theoretical values ​​of the current density and oxygen transmission rate according to Faraday's law are obtained in Example 2. From the above results, it can be seen that the behavior of the current density with respect to the electric field strength shown in FIG. 3 reflects the behavior of the oxide ion conduction of the laminate. [Explanation of symbols]

[0066] 10 Laminate 11 Solid electrolyte layer 12 cathode 13 Anode 15 Cathode side intermediate layer

Claims

1. A laminate including a solid electrolyte layer, a cathode disposed on one surface of the solid electrolyte layer, an anode disposed on the other surface of the solid electrolyte layer, and an intermediate layer disposed between the solid electrolyte layer and the cathode, The material constituting the intermediate layer is It has a fluorite structure, containing lanthanum, one or more rare earth elements Ln selected from samarium, gadolinium, yttrium, erbium, ytterbium, and dysprosium, and cerium oxide; The value of Ln / Ce, which is the atomic ratio of Ln to Ce, is 0.001 or more and 0.08 or less, and Under a temperature condition of 600°C, a 1.0 × 10 ７ Above 1.0 x 10 ８ A laminate in which, when an electric field of 100 V / m or less is applied, the lattice volume increases in the range of 0.3% to 2.0% compared to when no electric field is applied.

2. The laminate of claim 1, wherein the rare earth element Ln is samarium or gadolinium.

3. 3. The laminate according to claim 1, wherein the lattice constant of the material constituting the intermediate layer is 5.50 Å or more and 5.60 Å or less under a temperature condition of 600°C and in a state where no electric field is applied between the cathode and the anode.

4. 3. The laminate according to claim 1, wherein the solid electrolyte layer is an oxide ion conductor.

5. The solid electrolyte layer is a compound represented by the formula (1): A ９．３＋ｘ [T ６．０－ｙ M ｙ ]O ２６．０＋ｚ 3. The laminate according to claim 1, comprising a composite oxide represented by the formula: (in the formula, A is one or more elements selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Be, Mg, Ca, Sr, and Ba; T is an element containing Si or Ge, or both; M is one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Y, Zr, Ta, Nb, B, Ge, Zn, Sn, W, and Mo; x is a number of -1.4 or more and 1.5 or less; y is a number of 0.0 or more and 3.0 or less; and z is a number of -5.0 or more and 5.2 or less; and a ratio of the number of moles of A to the number of moles of T is 1.3 or more and 3.7 or less).

6. A laminate according to claim 1 or 2, wherein the value of La / Ce, which is the atomic ratio of La to Ce, is 0.3 or more and 1.2 or less.

7. The laminate according to claim 1, wherein the atomic ratio of Ln to Ce, Ln / Ce, is 0.02 or more and 0.06 or less.

8. The oxygen permeation rate of the solid electrolyte layer is 3.1 ml cm under a temperature condition of 600°C. －２ ・min －１ 6.0ml / cm or more －２ ・min －１ 3. The laminate according to claim 1 or 2, wherein:

9. 3. The laminate according to claim 1, wherein a material constituting the cathode and / or the anode contains one or more elements selected from the group consisting of Pt, Pd, Au, Ir, Ru, Rh, and Ag.

10. The laminate according to claim 1 or 2, further comprising an intermediate layer disposed between the solid electrolyte layer and the anode.

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