Solid electrolyte junction and electrochemical device including the same

Abstract

This solid electrolyte assembly (10) is obtained by sequentially superposing, on one surface of a substrate (11), a first electrode layer (12) and a solid electrolyte layer (13) in this order. The first electrode layer (12) contains platinum or the like, and a metal oxide that has ion conductivity. The substrate (11) has a plurality of through holes (hole parts (14)) which extend in a direction that intersects with the surface facing the first electrode layer (12). It is preferable that the metal oxide has oxide ion conductivity. It is also preferable that the metal oxide contains one or more rare earth elements.

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte junction and an electrochemical device including the same. [Background technology]

[0002] In the technical field of solid oxide fuel cells, a technique is known in which a solid electrolyte membrane and an electrode membrane are formed on a substrate having a plurality of through-holes penetrating in the thickness direction, as described in, for example, Patent Document 1 and Non-Patent Document 1. By providing such through-holes, it is possible to further improve gas permeability, such as oxygen permeability, in the electrochemical element.

[0003] As shown in Patent Document 1 and Non-Patent Document 1, a solid electrolyte membrane-electrode membrane laminate for a solid oxide fuel cell is produced by a method in which a support for the solid electrolyte is produced on a substrate having through-holes, and an electrode is formed on the surface of the solid electrolyte. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2007 / 084776 Pamphlet [Non-patent literature]

[0005] [Non-Patent Document 1] Journal of Power Sources 206 (2012) 84-90 Summary of the Invention

[0006] However, the solid electrolyte membrane-electrode membrane laminate in such a solid oxide fuel cell is generally formed thin in order to increase the oxide ion conductivity, and as a result, it cannot be said to have high mechanical strength. In a solid oxide fuel cell having the above-mentioned structure, the solid electrolyte layer located above the through-hole does not have a member to support it, and therefore is prone to deformation or damage due to the action of external forces, such as forces caused by expansion and contraction, or the release of stress that the solid electrolyte receives from the substrate when the through-hole is formed in the substrate, which may interfere with stable operation of the fuel cell. Therefore, an object of the present invention is to provide a solid electrolyte junction and an electrochemical device that can overcome the above-mentioned drawbacks of the prior art.

[0007] The present invention provides a solid electrolyte junction including a first electrode layer and a solid electrolyte layer stacked in this order on one surface of a substrate, the first electrode layer contains at least one of a platinum group element, gold, and an alloy containing any of them, and an ion-conductive metal oxide; The above-mentioned object is achieved by providing a solid electrolyte junction in which the substrate has a plurality of through-holes extending in a direction intersecting the surface facing the first electrode layer.

[0008] The present invention also provides an electrochemical device including the solid electrolyte junction. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the structure of one embodiment of a solid electrolyte joined body of the present invention. [Figure 2] FIG. 2 is an enlarged view of a main part of the solid electrolyte bonded body shown in FIG. 1, as viewed from the substrate side. [Figure 3] FIG. 3 is an enlarged schematic view showing a main part of another embodiment of the solid electrolyte joined body of the present invention. [Figure 4] FIG. 4 is an optical microscope image of the solid electrolyte assembly of Example 1. As shown in FIG. [Figure 5]FIG. 5 is an optical microscope image of the solid electrolyte assembly of Example 3. As shown in FIG. [Figure 6] FIG. 6 is an optical microscope image of the solid electrolyte assembly of Comparative Example 1. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. One embodiment of a solid electrolyte joint of the present invention has a structure shown in Figure 1. The solid electrolyte joint 10 shown in the figure is configured by laminating a first electrode layer 12 and a solid electrolyte layer 13 in this order on one surface of a substrate 11.

[0011] Substrate 11 is primarily used as a support for first electrode layer 12 and solid electrolyte layer 13, which will be described later. Substrate 11 is a plate-like body having two opposing main surfaces 11a and 11b. There are no particular limitations on the shape of substrate 11 in a plan view, and it may have any shape, such as a polygonal shape such as a rectangle, a circle, or an ellipse.

[0012] A plurality of holes 14 are formed in the substrate 11. The holes 14 extend along a direction intersecting a surface of the substrate 11 facing the first electrode layer 12, i.e., a main surface 11a shown in FIG. 1 . The holes 14 generally extend along a direction perpendicular to the surface of the substrate 11 facing the first electrode layer 12. The holes 14 extend so as to penetrate between the two main surfaces 11a, 11b of the substrate 11, and are open in each of the main surfaces 11a, 11b. In other words, the holes 14 are through-holes. The holes 14 are formed for the purpose of improving gas supply, such as supply of oxygen gas, to the first electrode layer 12, when an electrochemical device including the solid electrolyte joint 10 is used.

[0013] 2 is an enlarged view of a main portion of the main surface 11b, which is the exposed surface of the two main surfaces of the substrate 11. As shown in the figure, the holes 14 are open on the main surface 11b. The shape of the holes 14 opening on the main surface 11b may be, for example, circular, as shown in the figure. However, the shape of the holes 14 is not limited to this and may be other shapes, such as polygons such as triangles or rectangles, or ellipses, or combinations of these shapes. In particular, a circle or a regular polygon is preferable.

[0014] The holes 14 may be formed over the entire opposing region between the substrate 11 and the first electrode layer 12, or may be formed in at least a part of the opposing region. In the embodiment shown in Fig. 1, the holes 14 are formed in an inner region 11d of the opposing region between the substrate 11 and the first electrode layer 12, which is located more inward than the peripheral region 11c of the substrate 11.

[0015] As shown in FIG. 2, the holes 14 opening on the main surface 11b are regularly arranged. There are no particular limitations on the arrangement pattern of the holes 14, and various arrangement patterns can be adopted as long as gas is smoothly supplied to the first electrode layer 12 through the holes 14. FIG. 2 shows the holes 14 arranged in a staggered pattern. Furthermore, the shortest distance between the outer peripheries of adjacent holes 14 in a plan view is preferably 3 μm to 50 μm on average, more preferably 4 μm to 40 μm, and even more preferably 5 μm to 20 μm, from the viewpoint of increasing the area of ​​the first electrode layer 12 in contact with the supply gas through the holes 14. Increasing the area of ​​the first electrode layer 12 in contact with the supply gas can reduce the electrical resistance of the solid electrolyte assembly 10. For example, when the solid electrolyte assembly 10 is used in a solid oxide fuel cell, the output can be improved.

[0016] The hole 14 extends linearly between the two main surfaces 11a and 11b of the substrate 11. The cross-sectional shape of the hole 14 is the same at any position between the two main surfaces 11a and 11b of the substrate 11. For example, if the cross-sectional shape of the hole 14 is circular as shown in FIG. 2, the hole 14 may be a cylindrical space. Alternatively, the cross-sectional shape of the hole 14 may be varied depending on the position between the two main surfaces 11a and 11b of the substrate 11. For example, the opening area of ​​the exposed surface of the substrate 11 (i.e., the main surface 11b) may be larger than the opening area of ​​the surface of the substrate 11 facing the first electrode layer 12 (i.e., the main surface 11a). For example, as shown in FIG. 3, the hole 14 may be a space having a truncated cone shape. In this case, as shown in the same figure, the portion corresponding to the bottom surface of the truncated cone corresponds to the opening in the main surface 11b, and the portion corresponding to the top surface of the truncated cone corresponds to the opening in the main surface 11a. By shaping the holes 14 in this way, it is possible to further improve the gas supplyability, such as the supply of oxygen gas, to the first electrode layer 12 when using an electrochemical device including the solid electrolyte joint 10. In this case, when the opening area of ​​the holes 14 on the main surface 11a side is S1 and the opening area of ​​the holes 14 on the main surface 11b side is S2, the value of S2 / S1 is preferably 1 or more and 50 or less, more preferably 2 or more and 25 or less, and even more preferably 5 or more and 15 or less, from the viewpoint of further improving the gas supplyability to the first electrode layer 12.

[0017] From the viewpoint of maintaining the strength of the first electrode layer 12, the solid electrolyte layer 13, and the second electrode layer described later, the opening area of ​​each hole in the surface of the substrate 11 facing the first electrode layer 12 (i.e., the main surface 11a) is set to 300 μm 2 More than 71000μm 2 Preferably, it is less than 700 μm 2 More than 8000μm 2 More preferably, it is 1200 μm or less. 2 More than 4000μm 2 It is even more preferred that:

[0018] In relation to the opening area of ​​the above-mentioned hole 14, from the viewpoint of increasing the area of ​​the first electrode layer 12 that comes into contact with the supply gas through the hole 14, the ratio of the total opening area of ​​the hole 14 that is open on the surface of the substrate 11 facing the first electrode layer 12 (i.e., the main surface 11a) to the area of ​​the region in which the hole 14 is formed is preferably 20% or more and 80% or less, more preferably 40% or more and 70% or less, and even more preferably 50% or more and 60% or less.

[0019] The thickness of substrate 11 is preferably 10 μm or more and 1000 μm or less, more preferably 100 μm or more and 650 μm or less, and even more preferably 250 μm or more and 350 μm or less. By setting the thickness of substrate 11 within this range, substrate 11 can function sufficiently as a support for first electrode layer 12, solid electrolyte layer 13, and a second electrode layer described later, and the time required for the etching process of substrate 11 described later can be reduced. The thickness of substrate 11 can be measured using, for example, a vernier caliper or a digital thickness gauge.

[0020] The material for the substrate 11 is not particularly limited, as long as it does not inhibit the electrochemical reaction of the solid electrolyte junction 10. From the viewpoint of successfully forming the holes 14, it is advantageous to form the holes 14 by an etching method. From this viewpoint, the material for the substrate 11 is preferably made of a material that can be dry-etched or wet-etched. Examples of etchable materials include silicon and its compounds, semiconductors such as gallium arsenide, glass such as quartz, metals such as aluminum, copper, and nickel and their alloys, and ceramics such as strontium titanate and magnesia. Of these materials, silicon is particularly preferred from the viewpoints of mass productivity and etching. Dry etching can be performed by reactive ion etching (RIE) using fluorocarbon or halogen gas. Among RIE methods, deep etching (DRIE) is preferred, which alternates between an etching process using sulfur hexafluoride (SF6) and a passivation process using a fluoroalkane gas such as octafluorocyclobutane (C4F8). Wet etching can be isotropic etching using hydrofluoric acid, nitric acid, sulfuric acid, phosphoric acid, etc., or anisotropic etching using alkaline solutions such as KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), and EDP (ethylenediamine pyrocatechol).

[0021] In the solid electrolyte junction 10 shown in FIG. 1, a solid electrolyte layer 13 is disposed on a substrate 11 via a first electrode layer 12. The solid electrolyte layer 13 generally has a certain thickness and is made of a solid material containing a material having ion conductivity. A material having oxide ion conductivity is typically used for the solid electrolyte layer 13, but other materials having anion conductivity, such as carbonate ion conductivity or halide ion conductivity, cation conductivity, or proton conductivity, may also be used depending on the specific application of the solid electrolyte junction 10. Examples of materials having cation conductivity include Li5La3Ta2O 12 (LLT) and Li7La3Zr2O 12Examples of materials with lithium ion conductivity include BaZrO3 and BaZrCeO3.

[0022] When the solid electrolyte layer 13 has oxide ion conductivity, the solid electrolyte layer 13 is 1 , M 2 It is preferable that the solid electrolyte layer 13 is made of a compound containing M and O. By using such a compound, it is possible to further increase the oxide ion conductivity of the solid electrolyte layer 13. 1 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, Y, Ba and Bi. 2 is one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Ta, Nb, B, Si, Ge, Zn, Sn, W, and Mo. The compound preferably has an apatite-type crystal structure.

[0023] In particular, the solid electrolyte layer 13 is a compound represented by the formula (1)M 1 9.33+x [T 6.00-y M 2 y ]O 26.0+z In order to further enhance the oxide ion conductivity of the solid electrolyte layer 13, it is preferable to include a composite oxide represented by the formula: 1 As described above, 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, Y, Ba, and Bi. T is an element containing Si or Ge, or both. M 2 is one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Ta, Nb, B, Zn, Sn, W, and Mo. x is a number between -1.33 and 1.50. y is a number between 0.00 and 3.00. z is a number between -5.00 and 5.20. The ratio of M to the number of moles of T 1The molar ratio of these is 1.33 to 3.61. The composite oxide preferably has an apatite-type crystal structure.

[0024] In formula (1), M 1 The elements listed above, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Be, Mg, Ca, Sr, Y, Ba, and Bi, are lanthanides or Group 2 elements that can form positively charged ions and form an apatite-type hexagonal crystal structure. Among these, from the viewpoint of further improving oxide ion conductivity, a combination of one or more elements selected from the group consisting of La, Nd, Ba, Sr, Ca, Y, Bi, and Ce is preferred, and in particular, a combination of La or one of Nd, or La with one or more elements selected from the group consisting of Nd, Ba, Sr, Ca, Y, Bi, and Ce is preferred. Furthermore, T in formula (1) may be an element containing Si or Ge, or both.

[0025] M in Equation (1) 2 Preferred examples of the element include one or more elements selected from the group consisting of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Zr, Ta, Nb, B, Zn, Sn, W, and Mo. Among these, B, Zn, and W are particularly preferred in terms of increasing oxide ion conductivity.

[0026] In formula (1), x is preferably a number of -1.33 to 1.50, more preferably -1.00 to 1.00, and more preferably 0.00 to 0.70, and even more preferably 0.45 to 0.65, from the viewpoint of filling the T element position in the apatite-type crystal lattice and enhancing oxide ion conductivity. y in formula (1) is preferably a number of 0.00 to 3.00, even more preferably 0.40 to less than 1.00, and even more preferably 0.40 to 0.90, and even more preferably 0.80 to 0.70, particularly preferably 0.50 to 0.70. From the viewpoint of maintaining electrical neutrality within the apatite-type crystal lattice, z in formula (1) is preferably a number of −5.00 or more and 5.20 or less, more preferably −3.00 or more and 2.00 or less, and particularly preferably −2.00 or more or 1.50 or less, and most preferably −1.00 or more or 1.00 or less.

[0027] In formula (1), M relative to the number of moles of T 1 The ratio of the number of moles of (9.33+x) / (6.00-y), in other words (9.33+x) / (6.00-y), is preferably 1.33 or more and 3.61 or less, more preferably 1.40 or more and 3.00 or less, and even more preferably 1.50 or more and 2.00 or less, from the viewpoint of maintaining the spatial occupancy rate in the apatite-type crystal lattice.

[0028] Among the composite oxides represented by formula (1), M 1 The composite oxide in which the lanthanum is 9.33+x [T 6.00-y M 2 y ]O 26.0+z It is preferable to use a composite oxide represented by the formula: La 9.33+x [T 6.00-y M 2 y ]O 26.0+z Specific examples of composite oxides represented by the formula include La 9.33+x (Si 5.30 B0.70 )O 26.0+z , La 9.33+x (Si 4.70 B 1.30 )O 26.0+z , La 9.33+x (Si 4.70 Ge 1.30 )O 26.0+z , La 9.33+x (Si 4.70 Zn 1.30 )O 26.0+z , La 9.33+x (Si 4.70 W 1.30 )O 26.0+z , La 9.33+x (Si 4.70 Sn 1.30 )O 26.0+z , La 9.33+x (Ge 4.70 B 1.30 )O 26.0+z Among the composite oxides represented by formula (1), M 1 Particularly preferred is a composite oxide in which L is lanthanum and T is Si, that is, a composite oxide containing La and Si. The composite oxide represented by formula (1) can be produced, for example, according to the method described in International Publication WO2016 / 111110.

[0029] When the solid electrolyte layer 13 has oxide ion conductivity, the solid electrolyte layer 13 is preferably not only a composite oxide containing La and Si, but also at least one selected from the group consisting of yttrium-stabilized zirconia (YSZ), samarium-doped ceria (SDC), gadolinium-doped ceria (GDC), and yttrium-doped bismuth oxide (YBO).

[0030] 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.

[0031] The thickness of the solid electrolyte layer 13 is preferably 10 nm or more and 1000 nm or less, more preferably 30 nm or more and 500 nm or less, and even more preferably 50 nm or more and 300 nm or less, from the viewpoint of effectively reducing the electrical resistance of the solid electrolyte assembly 10. The thickness of the solid electrolyte layer 13 can be measured by cross-sectional observation using a stylus step gauge or an electron microscope.

[0032] In the solid electrolyte junction 10 shown in FIG. 1 , a first electrode layer 12 is disposed between a substrate 11 and a solid electrolyte layer 13. The first electrode layer 12 functions as an electrode for the solid electrolyte layer 13. For this purpose, the first electrode layer 12 is composed of metal elements having oxygen reduction catalytic activity, namely, elements including at least one of platinum group elements, gold, and alloys containing these elements (hereinafter, these elements are collectively referred to as “platinum, etc.”). The first electrode layer 12 also contains a metal oxide having ion conductivity (hereinafter, also referred to as “ion-conductive metal oxide”). Platinum, etc., is preferably present in the first electrode layer 12 in the form of a simple metal. In this specification, “platinum group elements” refers to any of the elements Pt, Pd, Rh, Ir, Ru, and Os. An alloy containing a platinum group element or gold refers to an alloy containing at least a platinum group element or gold. Examples of alloy constituent elements other than platinum group elements and gold include transition metal elements such as Ni and Fe. As the platinum or the like used in the first electrode layer, it is desirable to use Pt in order to enhance the oxygen reduction catalytic activity of the electrode.

[0033] The first electrode layer 12 also functions as a support for the solid electrolyte layer 13. Specifically, a region of the first electrode layer 12 (region designated by reference numeral 12a in FIG. 1 ) in the portion of the substrate 11 where the hole 14 is formed is not supported by the substrate 11. Hereinafter, the region designated by reference numeral 12a will also be referred to as the "unsupported region." The solid electrolyte layer 13 located directly above the unsupported region 12a is supported only by the unsupported region 12a. Therefore, if the unsupported region 12a does not provide sufficient support, it becomes difficult for the solid electrolyte layer 13 to maintain its layer structure. Therefore, in the solid electrolyte assembly 10 of this embodiment, the first electrode layer 12 is provided between the substrate 11 and the solid electrolyte layer 13, thereby reliably maintaining the layer structure of the solid electrolyte layer 13, particularly in the portion of the first electrode layer 12 corresponding to the unsupported region 12a.

[0034] From the viewpoint of more reliably maintaining the layer structure of the solid electrolyte layer 13 and from the viewpoint of reducing the electrical resistance of the solid electrolyte assembly 10, in the first electrode layer 12 containing platinum or the like and an ion-conductive metal oxide, the platinum or the like and the ion-conductive metal oxide preferably form a so-called cermet. For example, in the first electrode layer 12, the ion-conductive metal oxide and the platinum or the like preferably have a co-continuous structure. To make the first electrode layer 12 have such a co-continuous structure, the first electrode layer 12 may be formed by, for example, a method described below. Whether the first electrode layer 12 has a co-continuous structure can be confirmed by, for example, cross-sectional observation using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) or energy dispersive X-ray spectroscopy (EDS).

[0035] The proportion of the ion-conductive metal oxide in first electrode layer 12, expressed in terms of volume calculated from the deposition rate of a single film of platinum or the like and the deposition rate of the ion-conductive oxide, is preferably 1 vol% to 50 vol%, more preferably 2 vol% to 40 vol%, and even more preferably 3 vol% to 30 vol%. Setting the proportion of the ion-conductive metal oxide in first electrode layer 12 within this range is advantageous from the viewpoints of first electrode layer 12 functioning satisfactorily as an electrode for solid electrolyte layer 13 and first electrode layer 12 functioning satisfactorily as a support for solid electrolyte layer 13 and the second electrode layer.

[0036] From a similar viewpoint, the proportion of platinum or the like in first electrode layer 12, expressed in terms of volume calculated from the film formation rate of a single film of platinum or the like and the film formation rate of the ion-conductive oxide, is preferably 50 vol% or more and 99 vol% or less, more preferably 60 vol% or more and 98 vol% or less, and even more preferably 70 vol% or more and 97 vol% or less.

[0037] The proportions of the ion-conductive metal oxide and the platinum, etc. in first electrode layer 12 can be measured by the following method. Films of the ion-conductive metal oxide and the platinum, etc. are separately formed on a substrate, and the thicknesses of each are measured using a stylus profilometer, allowing the proportions of each to be calculated when the ion-conductive metal oxide and the platinum, etc. are simultaneously formed. Alternatively, the proportions can be measured by EDS measurement using an SEM or TEM, and quantitative analysis is performed by converting the atomic ratio of each element in the film into a volume using the density.

[0038] First electrode layer 12 is preferably porous, which allows gas supplied through holes 14 formed in substrate 11 to diffuse within first electrode layer 12, facilitating the electrochemical reaction. From this perspective, first electrode layer 12 preferably has an average porosity of 2% or more and 15% or less, and more preferably 4% or more and 10% or less.

[0039] The average porosity is measured, for example, by the following method. First, a secondary electron image of the surface of the first electrode layer 12 is obtained using an SEM at an acceleration voltage of 5 kV and a magnification of 5000 times, in which the cermet and voids can be clearly distinguished. The image contrast is appropriately adjusted so that the cermet and voids can be distinguished by brightness. A 23 μm × 17 μm area of ​​the obtained image is binarized using Image-Pro (registered trademark) (manufactured by Media Cybernetics) to separate the bright areas consisting of the cermet and the dark areas consisting of voids, and the area ratio is measured to determine the average porosity.

[0040] The thickness of first electrode layer 12 is preferably 50 nm or more and 1000 nm or less, more preferably 100 nm or more and 500 nm or less, and even more preferably 200 nm or more and 400 nm or less. By setting the thickness of first electrode layer 12 within this range, first electrode layer 12 functions sufficiently as an electrode for solid electrolyte layer 13, and first electrode layer 12 functions sufficiently as a support for solid electrolyte layer 13. The thickness of first electrode layer 12 can be measured by cross-sectional observation using a stylus profilometer or an electron microscope.

[0041] The ion-conductive metal oxide, which is one of the components constituting the first electrode layer 12, has ion conductivity as described above. The ion-conductive metal oxide typically has oxide ion conductivity, but may have other anion conductivity, such as carbonate ion conductivity or halide ion conductivity, or cation conductivity such as lithium ion conductivity, depending on the specific application of the solid electrolyte joint 10. The ion conductivity of the ion-conductive metal oxide is preferably the same as the ion conductivity of the solid electrolyte layer 13 described above, from the viewpoint of fully exhibiting the functions of the solid electrolyte joint 10. For example, when the solid electrolyte layer 13 has oxide ion conductivity, it is preferable that the ion-conductive metal oxide also has oxide ion conductivity.

[0042] When the ion-conductive metal oxide has oxide-ion conductivity, it is preferable to use, for example, a metal oxide containing one or more rare earth elements. Examples of such metal oxides include at least one selected from the group consisting of a composite oxide containing lanthanum and silicon, yttrium-stabilized zirconia, samarium-doped ceria, gadolinium-doped ceria, and yttrium-doped bismuth oxide. Details of these metal oxides are as described above for the materials constituting the solid electrolyte layer 13.

[0043] In particular, it is preferable that the ion-conductive metal oxide is a mixed conductor having both ion conductivity and electronic conductivity, since this can further improve the performance of the solid electrolyte assembly 10. When the solid electrolyte layer 13 has oxide ion conductivity, it is preferable that the ion-conductive metal oxide is a mixed conductor having both oxide ion conductivity and electronic conductivity.

[0044] As a mixed conductor having both oxide ion conductivity and electron conductivity, for example, ABO 3-δPreferably, a perovskite structure represented by the formula is used. In the formula, A represents a rare earth element, an alkaline earth metal element, an alkali metal element, a Group 14 element, or a Group 15 element. B represents a transition metal element or a Group 13 element, such as Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, In, and W. δ is a fraction resulting from the valence and amount of A, B, and O, and can be either positive or negative. 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-δ It is preferred to use metal oxides of the type.

[0045] ABO 3-δ In the oxide represented by the formula (I), B, which is a transition metal element or a Group 13 element, is preferably one or more elements selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Ta, In, and W, from the viewpoint of further improving the oxide ion conductivity and the electron conductivity. 3-δ It is also advantageous that the B site of the oxide represented by the formula (I) is partly occupied by cobalt and nickel.

[0046] From the viewpoint of increasing the oxide ion conductivity of the solid electrolyte assembly 10 as a whole, ABO 3-δIt is advantageous for the oxide represented by the formula (I) to contain lanthanum in part of the A site. Hereinafter, this oxide will also be referred to as "oxide a." The content of lanthanum in oxide a, expressed as the atomic ratio of lanthanum to all elements located at the A site, is preferably 0.05 to 0.8, more preferably 0.15 to 0.70, and even more preferably 0.15 to 0.60. Although the reason why the use of oxide a increases oxide ion conductivity is unclear, the present inventors believe that the inclusion of lanthanum in part of the A site increases the electronic conductivity of oxide a and reduces the resistance at the interface between the solid electrolyte and the electrode.

[0047] ABO 3-δ Whether lanthanum is located in part of the A site in an oxide represented by the formula (I) and the atomic ratio of lanthanum to all elements located in the A site can be determined by structural analysis using X-ray diffraction or the like and composition analysis using energy dispersive X-ray spectroscopy (EDS), electron probe microanalyzer (EPMA), ICP optical emission spectroscopy, or the like.

[0048] ABO 3-δ From the viewpoint of enhancing the oxide ion conductivity of the solid electrolyte assembly 10 as a whole, it is preferable that the alkaline earth metal element occupying the A site in the oxide represented by the formula (I) is one or more elements selected from the group consisting of barium and strontium.

[0049] ABO 3-δ The oxide represented by the formula (I) is preferably a composite oxide containing La, Sr, Co, and Ni. By using such a composite oxide, the oxide ion conductivity of the solid electrolyte joint 10 as a whole can be further improved. Specific examples of such composite oxides include La, 0.8 Sr 0.2 Co 0.5 Ni 0.5 O 3-δ , La 0.6 Sr 0.4 Co 0.8 Ni 0.2 O 3-δ , La 0.6Sr 0.4 Co 0.2 Fe 0.78 Ni 0.02 O 3-δ , etc.

[0050] Although not shown, a layer of a compound containing an element constituting the substrate 11 or an element constituting the first electrode layer 12 may be present on the surface of the substrate 11 facing the first electrode layer 12, i.e., the main surface 11a. For example, if the substrate 11 is made of silicon, a layer of a compound containing silicon, such as a SiO2 layer, may be formed on the main surface 11a. Alternatively, if the first electrode layer 12 contains SDC, a material having oxide ion conductivity, an SDC layer (an SDC layer not containing platinum or the like) may be formed on the main surface 11a. Because SiO2 and SDC are materials with low electronic conductivity, forming a SiO2 layer or an SDC layer on the main surface 11a has the advantage of suppressing current leakage to the substrate 11, even if the substrate 11 is made of a material with high electronic conductivity (e.g., silicon).

[0051] After the through-holes 14 are formed in the substrate 11, it is preferable to remove the layer of a compound containing the elements constituting the substrate 11 or the elements constituting the first electrode layer 12 on the through-holes 14 by reactive ion etching (RIE) in order to ensure sufficient gas supply to the first electrode layer 12.

[0052] In the solid electrolyte junction 10 of the embodiment shown in FIG. 1 , a second electrode layer (not shown) may be disposed on the surface of the solid electrolyte layer 13 opposite the surface facing the first electrode layer 12. The provision of the second electrode layer can impart additional functions to the solid electrolyte junction 10. The material constituting the second electrode layer is not particularly limited as long as it functions as an electrode for the solid electrolyte layer 13, and can be selected depending on the application of the electrochemical device. Examples of materials contained in the second electrode layer include metals such as Ni, Zn, Sn, Li, Au, Ag, Pt, Rh, and Pd, alloys and metal oxides containing these elements, carbonates such as lithium carbonate and barium carbonate, mixed conductors containing elements such as La, Sr, and Co and having both oxide ion conductivity and electronic conductivity, and zinc tungstate, and composites of these materials are also possible. Alternatively, the material contained in the second electrode layer may be the same as the material constituting the first electrode layer 12.

[0053] The second electrode layer preferably has a bicontinuous structure in which metal oxides are bonded by platinum or the like, similar to the first electrode layer 12 described above. The thickness of the second electrode layer can be the same as that of the first electrode layer 12.

[0054] Next, a preferred method for producing the solid electrolyte assembly 10 of the embodiment shown in FIG. 1 will be described. The production of the solid electrolyte assembly 10 includes a step of forming the first electrode layer 12, and a subsequent step of forming the solid electrolyte layer 13 and the second electrode layer. Each step will be described below.

[0055] In the step of forming the first electrode layer 12, first, a substrate 11 is prepared, and the first electrode layer 12 is formed on one surface of the substrate 11. Various thin film formation methods are used to form the first electrode layer 12. Specifically, the first electrode layer 12 can be formed by physical vapor deposition (PVD) methods such as evaporation, sputtering, and ion plating, or chemical vapor deposition (CVD). Of these various methods, sputtering is preferably used because it is easy to form the first electrode layer 12 having a co-continuous structure in which ion-conductive metal oxides are bonded by platinum or the like, and because it is suitable for mass production.

[0056] When forming the first electrode layer 12 by sputtering, a target of platinum or the like and a target of an ion-conductive metal oxide are used, thereby forming the first electrode layer 12 containing platinum or the like and the ion-conductive metal oxide. In addition, the porosity of the formed first electrode layer 12 can be controlled by adjusting the gas pressure during sputtering. Increasing the gas pressure can improve the porosity of the first electrode layer 12. The respective proportions of platinum or the like and the ion-conductive metal oxide in the first electrode layer 12 can be adjusted by appropriately setting the power supplied to the targets during sputtering.

[0057] After the first electrode layer 12 is formed, a step of forming the solid electrolyte layer 13 is carried out. The solid electrolyte layer 13 is formed on one of the two surfaces of the first electrode layer 12 that does not face the substrate 11. As with the formation of the first electrode layer 12, various thin film formation means are used to form the solid electrolyte layer 13. Of the thin film formation means, it is preferable to use a sputtering method, as this allows for the easy formation of the solid electrolyte layer 13 having the desired composition.

[0058] After the formation of the first electrode layer 12, and before the formation of the solid electrolyte layer 13, a step of firing the first electrode layer 12 and a subsequent step of forming the holes 14 in the substrate 11 may be performed. The firing step of the first electrode layer 12 is carried out to ensure that a co-continuous structure in which ion-conductive metal oxides are bonded by platinum or the like, i.e., a cermet, is formed in the first electrode layer 12. From the viewpoint of ensuring the formation of the co-continuous structure, the firing temperature is preferably 300°C or higher and 1300°C or lower, more preferably 500°C or higher and 1000°C or lower, and even more preferably 600°C or higher and 900°C or lower. From the same viewpoint, the firing time at the above firing temperature is preferably 1 minute to 10 hours, more preferably 10 minutes to 5 hours, and even more preferably 30 minutes to 3 hours. The firing atmosphere is not critical and may be an oxygen-containing atmosphere or a reducing atmosphere. By carrying out the firing step of the electrode layer, if the electrode layer is a layer containing, for example, SDC and platinum, a layer consisting only of SDC is formed on the surface of the substrate 11 facing the electrode layer, or if the substrate 11 is made of silicon, an SiO2 layer is formed on the surface of the substrate 11 facing the electrode layer.

[0059] After firing the first electrode layer 12, the substrate 11 can be subjected to a hole forming step. The hole forming step is conveniently performed from the main surface 11b side, which is the exposed surface of the substrate 11. For the hole forming step, it is preferable to use deep etching (DRIE) which is a dry etching method or anisotropic etching which is a wet etching method. By using these etching methods, deep holes 14 can be easily formed.

[0060] The dry etching method can be performed using a known photolithography technique. There are no particular limitations on the method of forming a photomask when performing the dry etching method or the type of dry etching gas, and these may be selected appropriately depending on the material of the substrate 11.

[0061] The wet etching method can also be performed using a known photolithography technique. There are no particular limitations on the method of forming a photomask or the type of chemical solution used when performing the wet etching method, and these may be selected appropriately depending on the material of the substrate 11.

[0062] The shape of the hole 14 formed will be a straight shape as shown in FIG. 1 when DRIE is used, and a tapered shape as shown in FIG. 3 when anisotropic etching is used.

[0063] After the hole formation step is completed, the step of forming the solid electrolyte layer 13 is carried out. To form the solid electrolyte layer 13, various thin film formation methods can be used, as with the first electrode layer 12. Specifically, the solid electrolyte layer 13 can be formed by physical vapor deposition (PVD) methods such as evaporation, sputtering, and ion plating, or chemical vapor deposition (CVD) methods. Sputtering is preferably used because of its superior mass productivity.

[0064] A firing step is preferably performed on the formed solid electrolyte layer 13. The firing step for the solid electrolyte layer 13 can be performed in the same manner as the firing step for the first electrode layer 12 described above.

[0065] In this manufacturing method, the firing step and hole forming step described above can also be performed after the formation of the solid electrolyte layer 13. In this case, it is not necessary to perform the hole forming step in the substrate 11 after the completion of the first electrode layer 12 forming step and before the solid electrolyte layer 13 forming step. Furthermore, in this case, the firing step is mainly performed on the solid electrolyte layer 13, not on the first electrode layer 12, so the firing step for the first electrode layer 12 can be performed after the completion of the first electrode layer 12 forming step and before the solid electrolyte layer 13 forming step. However, if the first electrode layer 12 is also sufficiently fired by the firing step mainly performed on the solid electrolyte layer 13, it is not necessary to perform a separate firing step for the first electrode layer 12 after the completion of the first electrode layer 12 forming step and before the solid electrolyte layer 13 forming step.

[0066] When the solid electrolyte assembly 10 has a second electrode layer, the second electrode layer can be formed after the step of forming the solid electrolyte layer 13. In this case, a firing step may be performed after the step of forming the solid electrolyte layer 13 is completed, and then a firing step may be performed again after the step of forming the second electrode layer is completed. However, from the viewpoint of simplifying the process, it is preferable not to perform the firing step after the step of forming the solid electrolyte layer 13 is completed, but to perform the firing step after the step of forming the solid electrolyte layer 13 and after the step of forming the second electrode layer is completed.

[0067] In addition, when forming the second electrode layer, the firing step may be performed after the completion of the step of forming the second electrode layer, and then the hole forming step may be performed after that. In this case, it is not necessary to perform the hole forming step after the completion of the step of forming the first electrode layer 12 and before the step of forming the solid electrolyte layer 13.

[0068] The solid electrolyte junction 10 manufactured by the above method is suitable for use as a component of an electrochemical device, such as a solid electrolyte fuel cell, a gas sensor such as an oxygen sensor, or a gas permeable element such as an oxygen permeable element.

[0069] 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, the shape and arrangement pattern of the holes 14 formed in the substrate 11 are not limited to those shown in Fig. 1 or 3.

[0070] Furthermore, although the solid electrolyte assembly 10 in the illustrated embodiment has a structure in which the first electrode layer 12 and the solid electrolyte layer 13 are in direct contact with each other, one or more additional layers may be disposed between the first electrode layer 12 and the solid electrolyte layer 13. The same applies to the structure between the second electrode layer and the solid electrolyte layer 13. [Example]

[0071] 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.

[0072] Example 1 Silicon crystal orientation <100> A 300 μm-thick substrate was prepared. A first electrode layer with a thickness of 800 nm was formed on one side of this substrate by sputtering. A 2-inch platinum target and a 4-inch SDC target were used as sputtering targets. Co-sputtering, in which power is supplied to both targets simultaneously, was used for deposition. DC sputtering was used for platinum, and RF sputtering was used for SDC. The argon gas flow rate was 50 sccm, and the argon pressure was 4 Pa. Sputtering was performed at room temperature with a power of 200 W for each. The resulting first electrode layer was porous and had a bicontinuous structure in which the SDC was bonded by the platinum. The first electrode layer contained 6% by volume of SDC and 94% by volume of platinum. The first electrode layer thus formed was sintered in air at 900°C for 1 hour.

[0073] A 200 nm thick solid electrolyte layer was formed on the first electrode layer by RF sputtering. The target for the sputtering was a 4-inch La 9.6 Si 5.3 B 0.7 O 26.1 A (LSBO) target was used. The argon gas flow rate was 50 sccm, and the argon pressure was 0.5 Pa. The power was 200 W, and sputtering was performed at room temperature. The solid electrolyte layer thus formed was sintered in an air atmosphere at 900°C for 1 hour.

[0074] Next, 100 holes were formed in the substrate by deep etching. The holes had a circular cross-sectional shape with a diameter of 50 μm. The ratio of the total opening area of ​​the holes on the surface of the substrate facing the electrode layer to the area of ​​the region where the holes were formed was 38%. In this way, the desired solid electrolyte assembly 10 was obtained.

[0075] Comparative Example 1 In this comparative example, a first electrode layer was not formed. That is, a solid electrolyte layer having a thickness of 200 nm was formed directly on the substrate by RF sputtering. A solid electrolyte joint was obtained in the same manner as in Example 1 except for this.

[0076] Example 2 Silicon crystal orientation <100> A 300 μm-thick substrate was prepared. A 300-nm-thick first electrode layer was formed on one side of this substrate by sputtering. A 2-inch platinum target and a 4-inch SDC target were used as sputtering targets. Co-sputtering, in which power is supplied to both targets simultaneously, was used for deposition. DC sputtering was used for platinum, and RF sputtering was used for SDC. The argon gas flow rate was 50 sccm, and the argon pressure was 4 Pa. Sputtering was performed at room temperature with a power supply of 200 W for each. The resulting first electrode layer was porous and had a bicontinuous structure in which the SDC was bonded by platinum. The first electrode layer contained 6% by volume of SDC and 94% by volume of platinum. The first electrode layer thus formed was sintered in air at 900°C for 1 hour.

[0077] Next, 100 holes were formed in the substrate using deep etching. The holes had a circular cross-sectional shape with a diameter of 50 μm. The ratio of the total opening area of ​​the holes on the surface of the substrate facing the electrode layer to the area of ​​the region in which the holes were formed was 38%. The shortest distance between the outer peripheries of adjacent holes was 20 μm.

[0078] After the holes were formed, a 300 nm thick solid electrolyte layer was formed on the first electrode layer by RF sputtering. The target for the sputtering was a 4-inch La 9.6 Si 5.3 B 0.7 O 26.1 The target was used. The flow rate of argon gas was 50 sccm, and the argon pressure was 0.5 Pa. The power was 200 W, and sputtering was performed at room temperature.

[0079] Next, a 300 nm-thick second electrode layer was formed on the solid electrolyte layer by sputtering. A 2-inch platinum target and a 4-inch SDC target were used as sputtering targets. Co-sputtering, in which power is supplied to both targets simultaneously, was used for film formation. DC sputtering was used for platinum, and RF sputtering was used for SDC. The argon gas flow rate was 50 sccm, and the argon pressure was 4 Pa. Sputtering was performed at room temperature with a power supply of 200 W. The resulting second electrode layer contained 8% by volume of SDC and 92% by volume of platinum. The second electrode layer and the solid electrolyte layer formed in this manner were fired at 900°C for 1 hour in an air atmosphere. In this manner, the desired solid electrolyte assembly 10 was obtained.

[0080] Example 3 The thickness of the first electrode layer in Example 2 was set to 260 nm. The other conditions were the same as those in Example 2 to obtain a solid electrolyte assembly 10.

[0081] Comparative Example 2 The first electrode layer and the second electrode layer in Example 2 were formed by DC sputtering using only a 2-inch platinum target. The argon gas flow rate was 50 sccm, and the argon pressure was 4 Pa. The supplied power was 200 W, and sputtering was performed at room temperature. The formed first electrode layer and second electrode layer were both composed of platinum only, and each had a thickness of 300 nm. Furthermore, no holes were formed in the substrate. A solid electrolyte junction was obtained in the same manner as in Example 2, except for these points.

[0082] [Rating 1] The strength of the first electrode layer and the solid electrolyte layer was evaluated for the solid electrolyte assemblies obtained in Examples 1 and 3 and Comparative Example 1. Specifically, the first electrode layer and the solid electrolyte layer on the through-holes of the obtained solid electrolyte assemblies were observed from the solid electrolyte layer side using an optical microscope, and the presence or absence of damage such as cracks or breaks in the unsupported regions 12a of the first electrode layer 12 corresponding to each hole 14 was confirmed, and the survival rate was calculated. The survival rate (%) was calculated by (the number of unsupported regions 12a where damage such as cracks or breaks was observed / the total number of unsupported regions 12a observed) × 100. The results are shown in Table 1 and Figures 4 to 6.

[0083] [Rating 2] The solid electrolyte junctions obtained in Example 2 and Comparative Example 2 were subjected to electrochemical measurement evaluation. Specifically, measurements were performed by AC impedance method using an SI1260 manufactured by Solartron. Measurement conditions included a measurement amplitude of 30 mV and frequencies ranging from 1 MHz to 1 kHz. A Nyquist plot was performed using the measurement results, and arc fitting was performed using analysis software in the above frequency range. The value at the intersection with the real axis was evaluated as the resistance value. The results are shown in Table 1.

[0084] [Table 1]

[0085] As is clear from FIGS. 4 to 6, in Comparative Example 1, cracks and breaks occurred in the solid electrolyte above the through-holes, whereas in Examples 1 and 3, no damage was observed. Furthermore, as is clear from Table 1, cracks occurred in the solid electrolyte layer above all of the through holes in Comparative Example 1, whereas no damage occurred in the solid electrolyte layer above all of the through holes in Example 1. This result clearly shows that the presence of the first electrode layer supporting the solid electrolyte layer is effective in improving strength. Furthermore, as is clear from Table 1, Example 2 exhibited a resistance value that was approximately one-eighth or less of that of Comparative Example 2. [Industrial Applicability]

[0086] According to the present invention, even when a large number of through holes are formed in the substrate of a solid electrolyte joint, the first electrode layer effectively prevents damage to the solid electrolyte layer located above the through holes, and the solid electrolyte layer can stably maintain its shape. Furthermore, since the first electrode layer contains at least one of a platinum group element, gold, and an alloy containing these, and an ion-conductive metal oxide, a solid electrolyte joint with low electrical resistance can be provided.

Claims

1. A solid electrolyte junction comprising a first electrode layer and a solid electrolyte layer laminated in this order on one surface of a substrate, the first electrode layer contains at least one of a platinum group element, gold, and an alloy containing any of them, and an ion-conductive metal oxide; In the first electrode layer, at least one of the platinum group element, gold, and an alloy containing any of them and the ion-conductive metal oxide have a bicontinuous structure, a ratio of the metal oxide to the first electrode layer is 1% by volume or more and 50% by volume or less; The substrate has a plurality of through holes extending in a direction intersecting a surface facing the first electrode layer.

2. The solid electrolyte joint according to claim 1 , wherein the metal oxide has oxide ion conductivity.

3. 3. The solid electrolyte joint according to claim 1, wherein the metal oxide contains one or more rare earth elements.

4. 4. The solid electrolyte joint according to claim 1, wherein the metal oxide is at least one selected from the group consisting of a composite oxide containing lanthanum and silicon, yttrium-stabilized zirconia, samarium-doped ceria, gadolinium-doped ceria, and yttrium-doped bismuth oxide.

5. 5. The solid electrolyte joint according to claim 1, wherein the metal oxide is a mixed conductor having both ionic conductivity and electronic conductivity.

6. 6. The solid electrolyte joint according to claim 1, wherein the first electrode layer is a porous body having an average porosity of 2% or more and 15% or less.

7. 7. The solid electrolyte joint according to claim 1, wherein the first electrode layer has a thickness of 50 nm or more and 1000 nm or less.

8. 8. The solid electrolyte joint according to claim 1, wherein the substrate is made of a material that can be dry-etched.

9. The through-holes have an opening area of ​​300 μm per hole on the surface of the substrate facing the first electrode layer. ２ 71000 μm or more ２ 9. The solid electrolyte joint according to claim 1, wherein:

10. 10. The solid electrolyte joint according to claim 1, wherein the through-holes have an opening area on an exposed surface of the substrate that is larger than an opening area on a surface of the substrate that faces the first electrode layer.

11. the through hole has a circular or regular polygonal shape in a plan view, 11. The solid electrolyte joint according to claim 1, wherein the shortest distance between the outer peripheries of the adjacent through holes in a plan view is 3 [mu]m or more and 50 [mu]m or less on average.

12. 12. The solid electrolyte joint according to claim 1, wherein the solid electrolyte layer has oxide ion conductivity.

13. 13. The solid electrolyte joint according to claim 12, wherein the solid electrolyte layer is at least one selected from the group consisting of a composite oxide containing lanthanum and silicon, yttrium-stabilized zirconia, samarium-doped ceria, gadolinium-doped ceria, and yttrium-doped bismuth oxide.

14. 14. The solid electrolyte joint according to claim 1, wherein a second electrode layer is disposed on a surface of the solid electrolyte layer opposite to a surface facing the first electrode layer.

15. 15. The solid electrolyte joint according to claim 14, wherein the second electrode layer contains at least one of a platinum group element, gold, an alloy containing any of these, a metal oxide, and a composite thereof.

16. 16. The solid electrolyte joint according to claim 1, wherein a layer of a compound containing an element constituting the substrate or an element constituting the electrode layer is present on a surface of the substrate facing the first electrode layer.

17. An electrochemical device comprising the solid electrolyte junction according to claim 1 .

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