JP2022136049A - Solid electrolyte, electrolyte layer, battery, and manufacturing method of solid electrolyte - Google Patents

Abstract

To provide a solid electrolyte which has high ion conductivity and which is stable in ion conductivity regardless of an ambient temperature or gas condition, an electrolyte layer and a battery, which are arranged by use thereof, and a manufacturing method of such a solid electrolyte.SOLUTION: A solid electrolyte, an electrolyte layer, a battery and a manufacturing method of a solid electrolyte are disclosed. The solid electrolyte comprises a particular compound. The compound is a compound represented by the following general formula (1): A5-xB1-yM4-zX16-w (1). [In the formula (1), A is a cation and the quantity x of defects of A is in a range of -4 to 4; B is a cation and the quantity y of defects of B is in a range of -0.5 to 0.5; M is a cation and the quantity z of defects of M is in a range of -2 to 2; X is an anion and the quantity w of defects of X is in a range of -3 to 3.]SELECTED DRAWING: Figure 1

Description

Patent Law Article 30, Paragraph 2 application has been filed [1] Date of publication (publication date) September 21, 2021 Publications The 37th The Ceramic Society of Japan Kanto Branch Research Presentation Abstract Collection Public Interest Incorporated Association The Ceramic Society of Japan Issued <Documents> Abstracts of Lectures Published research papers Excerpts [2] Date (release date) September 22, 2021 (Date: September 21-22, 2021) Meeting name, venue The 37th Research Presentation Meeting of the Ceramic Society of Japan Kanto Branch Public Interest Incorporated Association The Ceramic Society of Japan Kanto Branch Hosted online using video conferencing system (Zoom) Fee > Online poster presentation (discussion) materials

The present invention relates to a solid electrolyte used in solid electrolyte layers of fuel cells, sensors, and the like, electrolyte layers and batteries using the solid electrolyte, and methods of manufacturing solid electrolytes.

Various fuel cells are attracting attention as a key to realizing a next-generation clean energy society and solving environmental problems. Various ion conductors, such as metal oxide proton conductors and oxide ion conductors, are known as substances that can be used in fuel cells and sensors.

Yttria-stabilized zirconia (ZrO ₂ —Y ₂ O ₃ ) (hereinafter referred to as “YSZ”) is known as a conventionally known ion conductor as oxide ion (O ²⁻ ) conductive ceramics. YSZ can be used in solid oxide fuel cells (hereinafter referred to as "SOFCs"), and SOFCs are known to have the advantages of particularly high power generation efficiency, no need for a fuel reformer, and excellent long-term stability. ing.

On the other hand, as proton conductors, perovskite-type oxides in which oxygen vacancies are introduced by chemical substitution, such as BaZr0.8Y0.2O2.9, are known.

Patent Document 1 discloses a crystalline inorganic compound in which at least one carrier selected from the group consisting of anions, cations, protons, electrons and holes can conduct. A compound with high electrical conductivity, for example, a compound exhibiting high ionic conductivity that conducts ions such as oxide ions (O ²⁻ ) and protons (H ⁺ ) can be used in solid electrolytes such as fuel cells.

In Patent Document 2, the present inventors disclosed a solid electrolyte containing a hexagonal perovskite-related compound, the compound having the general formula Ba _7-α Nb _(4-xy) Mo _(1+x) M _y O _(20+z) and a solid electrolyte, an electrolyte layer and a battery using the same. This solid electrolyte, electrolyte layer and battery using it have high electrical conductivity even in a low temperature range compared to YSZ, and can be suitably used for SOFC.

Japanese Patent No. 6448020 WO2020-153485

In addition to conventionally known ionic conductors, ionic conductors with higher ionic conductivity and higher oxygen transport number are desired.
There is also a demand for ionic conductors that have stable properties regardless of the surrounding environment. The ambient environment includes, for example, temperature conditions and dependence on oxygen partial pressure.

Regarding temperature conditions, conventional YSZ requires a high temperature of about 700° C. or higher to ensure the oxide ion conductivity required for batteries. Operating a battery at a high temperature of 700° C. or higher requires an operating environment and space, and other devices for keeping the battery at a high temperature and for shutting off or cooling the other environment to prevent the temperature from becoming high. Therefore, there is a demand for an ionic conductor whose ionic conductivity does not decrease over a wide range of temperature conditions.

Here, the proton conductor has lower conductivity activation energy than the oxygen ion conductor, and can achieve high conductivity at medium and low temperatures.
However, the ionic conductivity of the perovskite-type oxide base material itself in which oxygen vacancies are introduced by chemical substitution such as BaZr0.8Y0.2O2.9 is not high. Although the conductivity of this compound can be increased by introducing impurities or oxygen vacancies, an ionic conductor with higher ionic conductivity is desired. In addition, proton conductors such as BaZr0.8Y0.2O2.9 have the problem of exhibiting hole conduction under high oxygen partial pressure and having a low proton transference number, and are deteriorated in the presence of carbon dioxide. Other proton conductors are still required to increase the proton transference number and avoid degradation.

The inventors of the present invention have found that the above-mentioned proton conductors are chemically substituted to introduce oxygen vacancies, or to introduce impurities or oxygen vacancies to increase the conductivity, whereas the intrinsic ion We predicted that if we use a parent material that has a crystal structure with a deficient layer, we would be able to find a compound with high ionic conductivity due to the deficient layer.

The present invention has been made in view of the above circumstances, a solid electrolyte having high ionic conductivity and stable ionic conductivity even in the ambient temperature or atmosphere, an electrolyte layer using the same, a battery and a An object of the present invention is to provide a method for producing a solid electrolyte.

In order to solve the above problems, the present invention has the following aspects.
[1] A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a compound represented by the following general formula (1).
A _5-x B _1-y M _4-z X _16-w (1)
[In the formula (1), A is a cation, and the missing amount x of A is a numerical value of -4 to 4. B is a cation, and the defect amount y of B is a numerical value of -0.5 to 0.5. M is a cation, and the missing amount z of M is a numerical value of -2 to 2. X is an anion, and the missing amount w of X is a numerical value of -3 to 3. ]
[2] In the above formula (1), the average ionic radius of A is 1.10 to 1.83 Å, the average ionic radius of B is 0.73 to 1.24 Å, and the average ionic radius of M is 0.20 to 0.20 Å. 50 Å, the solid electrolyte having an average ionic radius of X of 1.10 Å to 1.68 Å.
[3] The solid electrolyte, wherein in the formula (1), the anion X is O, and w is the amount of oxygen deficiency.
[4] The solid electrolyte as described above, wherein the compound is a palmierite-type compound and is an electric conductor that conducts ions or electrons other than Ba ²⁺ and K ⁺ .
[5] The above solid electrolyte, wherein the compound is a rubidium ion conductor, an oxide ion conductor, a proton conductor, an electron conductor, or a mixed conductor thereof.
[6] A of the compound is a cation containing at least Rb, B is a cation containing at least one element selected from among Gd, La, Nd, Sm, Eu, Tb, and Bi, and M is at least The above-mentioned solid electrolyte, which is a cation containing Mo and X is an anion containing at least O.
[7] The compounds are _Rb5Gd (MoO4) ₄ , _Rb5La (MoO4) ₄ , _{Rb5Nd(MoO4)4 , Rb5Sm ( MoO4 ) 4} , _{Rb5Eu ( MoO4} ) ₄ , _Rb5Tb ( _MoO4 ) ₄ , _Rb5Bi ( _MoO4 ) ₄ , _{Rb5Pr ( MoO4} ) _{4 , Rb4.9Bi1.1Mo4O16.1 , or Rb4.5Ba0 .5} The solid electrolyte above which is GdMo ₄ O _16.25 .
[8] The above solid electrolyte, wherein the compound is Rb ₅ Gd(MoO ₄ ) ₄ .
[9] A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a compound represented by the following general formula (2).
A _2-x B _1-y M _1-z X _5-w (2)
[In the formula (2), A is a cation, and the defect amount x of A is a numerical value of -1 to 1. B is a cation, and the defect amount y of B is a numerical value of -0.5 to 0.5. M is a cation, and the missing amount z of M is a numerical value from -0.5 to 0.5. X is an anion, w is the amount of deficiency of the anion X, and is a numerical value from -1 to 1. ]
[10] In the above formula (2), the average ionic radius of A is 1.28 Å to 1.94 Å, the average ionic radius of B is 0.59 Å to 1.04 Å, and the average ionic radius of M is 0.31 Å to 0.31 Å. 47 Å, and the average ionic radius of X is between 1.10 Å and 1.68 Å.
[11] The solid electrolyte as described above, wherein the compound is an α-Ba ₂ ScAlO ₅ type or β-Ba ₂ ScAlO ₅ type compound, and is an electric conductor or an ion-electron mixed conductor that conducts ions or electrons.
[12] The solid electrolyte described above, wherein in the formula (2), the anion X is O, and w is the amount of oxygen deficiency.
[13] In the formula (2), A is a cation containing at least Ba, B is a cation containing at least Sc, Lu or In, M is a cation containing at least Al, and X contains at least O. The above solid electrolyte, which is an anion.
[14 _{] The compound} is _{Ba2InAlO5 , Ba2ScAlO5 , Ba2Sc0.87Al1.13O5 , Ba2LuAlO5 , or Ba2Lu0.9Al1.1O5 .} The solid electrolyte described above.
_{[ 15 ] The compounds are Ba2ScAlO5 , Ba2Sc0.87Al1.13O5 , Ba2LuAlO5 , Ba2ScAl0.9Ga0.1O5 , Ba2ScAl0.95Ga0 .05O5 , Ba2Sc0.95Ga0.05AlO5 , Ba2Sc0.95Ca0.05AlO4.976 , Ba2Sc0.95Mg0.05AlO4.975 , Ba2 _ _ _ _ _ _ Sc0.95Zr0.05AlO5.025 , Ba2Lu0.98Al1.02O5 , Ba2Lu0.96Al1.04O5 , Ba2Lu0.95Al1.05O _ _ _ _ _ _ _ 5 , Ba2Lu0.94Al1.06O5 , Ba2Lu0.93Al1.07O5 , Ba2Lu0.9Al1.1O5 , or Ba2Lu0.8Al1 _ _ _ _ _ _} The above solid _electrolyte which is _.2O5 .
[16] A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a Ba ₇ Sc ₆ Al ₂ O ₁₉ type compound represented by the following general formula (3).
A _7-x B _6-y M _2-z X _19-w (3)
[In the formula (3), A is a cation, and the missing amount x of A is a numerical value of -3.5 to 3.5. B is a cation, and the defect amount y of B is a numerical value of -3 to 3. M is a cation, and the missing amount z of M is a numerical value from -1 to 1. X is an anion, and w is the missing amount of the anion X, which is a value of -3 to 3. ]
[17] In the above formula (3), the average ionic radius of A is 1.28 to 1.94 Å, the average ionic radius of B is 0.59 to 0.90 Å, and the average ionic radius of M is 0.31 to 0.31 Å. 47 Å, and the average ionic radius of X is between 1.10 Å and 1.68 Å.
[18] The solid electrolyte, wherein the anion X is O in the formula (3).
[19] In the formula (3), A is a cation containing at least Ba, B is a cation containing at least Sc, M is a cation containing at least Al, and X is an anion containing at least O. , the solid electrolyte described above.
_{[ 20 ] The compound is Ba7Sc6Al2O19 , Ba6.3K0.7Sc6Al2O18.65 , Ba6.3Sr0.7Sc6Al2O19 , Ba7Sc _ _ 5.4 Mg0.6Al2O19.3 , Ba7Sc5.4Tb0.6Al2O19.3 , or Ba7Sc5.4Zr0.6Al2O19.3 _ _ _ _ _ _ _} , the solid electrolyte described above.
[21] A solid electrolyte used as a proton conductor, for use under temperature conditions of 200 to 1200°C.
[22] The above-mentioned solid electrolyte, which has an electrical conductivity of -7 or more when measured at 200°C, represented by log[σ(Scm ^-1 )].
[23] Fuel cells, sensors, electrodes, electrolytes, element concentrators, element separation membranes, element permeable membranes, element pumps, catalysts, photocatalysts, electrical/electronic/communication equipment, energy/environment-related equipment or optical equipment, The solid electrolyte described above.
[24] The solid electrolyte described above, which is for an electrolyte layer used in fuel cells or sensors.
[25] An electrolyte layer containing the solid electrolyte.
[26] A battery comprising the electrolyte layer described above.
[27] The above cell, which is a hydrogen fuel cell.
[28] A method for producing the solid electrolyte,
Producing the compound by a solid state reaction method,
Firing in the solid phase reaction method is
When the compound is a compound represented by the general formula (1), it is calcined in the atmosphere at 200 to 1000° C. for 5 to 20 hours and then at 300 to 1100° C. for 5 to 24 hours,
When the compound is a compound represented by the general formula (2) or (3), it is calcined at 200 to 1000° C. for 5 to 20 hours in the atmosphere and then at 1500 to 1700° C. for 3 to 24 hours in the atmosphere. do,
A method for producing a solid electrolyte.

According to the present invention, a solid electrolyte having high ionic conductivity and stable ionic conductivity even under ambient temperature or gas conditions, an electrolyte layer using the same, a battery, and a method for producing a solid electrolyte can be obtained.

It is a figure which shows the crystal structure of _Rb5Gd ( _{MoO4)4 of} this embodiment. _It is a figure which shows the _crystal structure _{of Ba2Sc0.83Al1.17O5 of} this embodiment. It is a figure which shows the _crystal structure of _Ba2ScAlO5 of this embodiment. It is a figure which shows the _crystal structure of _Ba2LuAlO5 of this embodiment. It is a figure which _shows the _{crystal structure} of _Ba7Sc6Al2O19 of this embodiment. FIG. 4 shows a histogram of the energy barriers (E _b ) estimated by the energy diagram (BVEL) of test oxide ions based on bond valences. 4 is a graph showing the results of XRD measurement of Rb ₅ Gd(MoO ₄ ) ₄ of Example 1. FIG. 2 is an Arrhenius plot of the total conductivity of Rb ₅ Gd(MoO ₄ ) ₄ of Example 1. FIG. 4 is a graph showing the measurement results of the oxygen partial pressure dependence of the total electrical conductivity of Rb ₅ Gd(MoO ₄ ) ₄ of Example 1. FIG. 4 is a graph showing the measurement results (Tauc plot) of the UV-vis spectrum of Rb ₅ Gd(MoO ₄ ) ₄ of Example 1. FIG. FIG. 3 is a graph showing the results of XRD measurement of Ba ₂ Sc _0.83 Al _1.17 O ₅ of Example 2; FIG. 4 is a graph showing the results of XRD measurement of Ba ₂ ScAlO ₅ of Example 3; FIG. 2 is a graphical representation of Arrhenius plots of the total conductivity of Ba ₂ Sc _0.83 Al _1.17 O ₅ of Example 2 and Ba ₂ ScAlO ₅ of Example 3 in dry air and wet air. Oxygen partial pressure dependence of the total electrical conductivity of (a) Ba ₂ Sc _0.83 Al _1.17 O ₅ of Example 2 and (b) Ba ₂ ScAlO ₅ of Example 3 in dry and wet atmospheres. It is a graph chart showing a measurement result. FIG. 2 is a graph showing measurement results of (a) the ionic conductivity of Ba ₂ ScAlO ₅ of Example 3 and (b) the proton transference number in a dry atmosphere and a wet atmosphere at an oxygen partial pressure of 10 ⁻²⁰ atmospheres. FIG. 2 is a graph (Arrhenius plot) comparing the proton conductivity of Ba ₂ Sc _0.83 Al _1.17 O _{5 of} Example 2 and Ba ₂ ScAlO ₅ of Example 3 with those of conventional conductors. FIG. 10 is a graph showing the results of XRD measurement of Ba ₂ LuAlO ₅ of Example 4; FIG. 4 is a graphical representation showing Arrhenius plots of the total conductivity of Ba ₂ LuAlO ₅ of Example 4 in dry air and wet air. FIG. 4 is a graph showing the measurement results of the oxygen partial pressure dependence of the total electrical conductivity of Ba ₂ LuAlO ₅ of Example 4 in a humid atmosphere. FIG. 10 is a graph showing the measurement results of the proton transference number of Ba ₂ LuAlO ₅ of Example 4; FIG. 3 is a graph (Arrhenius plot) comparing the proton conductivity of Ba ₂ LuAlO ₅ of Example 4 and Ba ₂ Lu _0.9 Al _1.1 O ₅ of Example 5 with that of a conventional proton conductor. FIG. 10 is a graph showing the results of XRD measurement of Ba ₇ Sc ₆ Al ₂ O ₁₉ of Example 6. FIG. FIG. 10 is a graph showing Arrhenius plots of the total electrical conductivity of Ba ₇ Sc ₆ Al ₂ O ₁₉ of Example 6 in dry air and wet air. FIG. 4 is a graph showing the measurement results of the oxygen partial pressure dependence of the total electrical conductivity of Ba ₇ Sc ₆ Al ₂ O ₁₉ of Example 6 in a dry atmosphere and a wet atmosphere. FIG. 10 is a graph (Arrhenius plot) comparing the proton conductivity of Ba ₇ Sc ₆ Al ₂ O ₁₉ of Example 6 with that of a conventional proton conductor. FIG. 2 is a schematic diagram of the crystal structure of Rb ₅ Bi(MoO ₄ ) ₄ ; FIG. 10 is a graph showing the results of XRD measurement of the Rb ₅ Bi(MoO ₄ ) ₄ compound of Example 7; FIG. 10 is a graph showing the results of XRD measurement of the Rb ₅ Pr(MoO ₄ ) ₄ compound of Example 8. FIG. FIG. 4 is a graph showing the results of XRD measurement of the Rb ₅ La(MoO ₄ ) ₄ compound of Reference Example. FIG. 4 is a graph showing the results of XRD measurement of the Rb ₅ Nd(MoO ₄ ) ₄ compound of Reference Example. FIG. 4 is a graph showing the results of XRD measurement of the Rb ₅ Sm(MoO ₄ ) ₄ compound of Reference Example. FIG. 4 is a graph showing the results of XRD measurement of the Rb ₅ Eu(MoO ₄ ) ₄ compound of Reference Example. FIG. 4 is a graph showing the results of XRD measurement of the Rb ₅ Tb(MoO ₄ ) ₄ compound of Reference Example. FIG. 11 is an Arrhenius plot of the total conductivity of Rb ₅ Bi(MoO ₄ ) ₄ of Example 7; FIG. FIG. 10 is a graph showing the results of measuring the total electrical conductivity of Example 7 for each temperature and oxygen partial pressure. FIG. 4 is a graph showing transference numbers of Rb ⁺ and O ²⁻ in Rb ₅ Bi(MoO ₄ ) ₄ estimated by the Tubandt method. FIG. 2 is a graph showing the relationship between bulk conductivity and grain boundary conductivity in Rb ₅ Bi(MoO ₄ ) ₄ estimated by the AC impedance method. FIG. 4 is a graph showing a bulk conductivity comparison for Rb ₅ Bi(MoO ₄ ) ₄ and various oxide ion conductors. FIG. 10 is a graph showing the total electrical conductivity of Rb ₅ Pr(MoO ₄ ) ₄ of Example 8; FIG. 10 is a graph showing the laboratory XRD peak pattern of the Rb _4.9 Bi _1.1 Mo ₄ O _16.01 compound of Example 9; FIG. 10 is a graph showing the total electrical conductivity of Rb _4.9 Bi _1.1 Mo ₄ O _16.01 of Example 9; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ ScAl _0.9 Ga _0.1 O ₅ compound of Example 10. FIG. FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ ScAl _0.95 Ga _0.05 O ₅ compound of Example 11; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ Sc _0.95 Ga _0.05 AlO ₅ compound of Example 12; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ Sc _0.95 Ca _0.05 AlO _4.975 compound of Example 13; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ Sc _0.95 Mg _0.05 AlO _4.975 compound of Example 14; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₂ Sc _0.95 Zr _0.05 AlO _5.025 compound of Example 15; FIG. 4 is a graph showing the results of XRD measurement of the compounds of Examples 4 and 16-22. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 16. FIG. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 17. FIG. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 18. FIG. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 19. FIG. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 20. FIG. 2 is an Arrhenius plot of total conductivity in dry nitrogen and wet nitrogen for the compound of Example 22. FIG. FIG. 4 is a graph showing the results of proton transference measurement of the compound of Example 4. FIG. FIG. 4 is a graph showing the results of conductivity measurements in wet nitrogen+hydrogen of the compound of Example 4; FIG. 4 is a graph showing the results of measurement of the conductivity in dry nitrogen of the compound of Example 4; FIG. 4 is a graphical representation comparing the proton conductivity of the compound of Example 4 with that of a conventionally known proton conductor. FIG. 4 is a graph showing the measurement results of the UV/visible diffuse reflectance spectrum of the compound of Example 4. FIG. FIG. 10 is a graph showing the results of XRD measurement of the Ba _6.3 K _0.7 Sc ₆ Al ₂ O _18.65 compound of Example 23. FIG. FIG. 10 is a graph showing the results of XRD measurement of the Ba _6.3 Sr _0.7 Sc ₆ Al ₂ O ₁₉ compound of Example 24. FIG. FIG. 10 is a graph showing the results of XRD measurement of the Ba ₇ Sc _5.4 Mg _0.6 Al ₂ O _18.7 compound of Example 25; FIG. 10 is a graph showing the results of XRD measurement of the Ba ₇ Sc _5.4 Tb _0.6 Al ₂ O _19.3 compound of Example 26. FIG. FIG. 10 is a graph showing the results of XRD measurement of the Ba ₇ Sc _5.4 Zr _0.6 Al ₂ O _19.3 compound of Example 27; ₁₀ is an _Arrhenius plot of the _total conductivity of _{Ba7Sc5.4Zr0.6Al2O19.3} of Example 27 _;

BEST MODE FOR CARRYING OUT THE INVENTION A solid electrolyte, an electrolyte layer, a battery, and a method for producing a solid electrolyte according to the present invention will be described below with reference to embodiments. However, the present invention is not limited to the following embodiments.

(solid electrolyte)
The solid electrolyte of the present embodiment contains a hexagonal perovskite-related compound, and this compound includes those represented by the specific general formula described below. Here, the solid electrolyte is a material that conducts ions, and includes materials that conduct both ions and (electrons or holes thereof). Each of the following compounds contains a small amount of an impurity phase, but generally a single-phase compound can be used.

All of these compounds have essential oxygen-deficient layers (c' and/or h' layers) in their crystal structures, as will be described later. Here, "'" is called a prime. With this oxygen-deficient layer, carriers can exist and high ionic conductivity can be achieved. The ions that conduct here can mainly include oxide ions (O ²⁻ ), protons (hydrogen ions, H ⁺ ), and the like. Since the compound has an oxygen-deficient layer, it can have a structure having defects without adding cations having a valence lower than that of the constituent cations of the base material. Since no additives are required, the base material itself, which has excellent phase stability, can be used as a solid electrolyte. It is easy to manufacture, stable at high temperatures and in various atmospheres, and has high ionic conductivity (ionic conductivity) without deterioration. expected to keep

(Hexagonal perovskite-related compounds: A _5-x B _1-y M _4-z X _16-w )
One aspect of the compound of the present embodiment is a solid electrolyte containing a hexagonal perovskite-related compound, the compound being represented by the following general formula (1).
A _5-x B _1-y M _4-z X _16-w (1)
[In the formula (1), A is a cation, and the missing amount x of A is a numerical value of 0 to 4. B is a cation, and the missing amount y of B is a numerical value of 0 to 0.5. M is a cation, and the missing amount z of M is a numerical value of 0-2. X is an anion, and w is the missing amount of the anion X, which is a value of -3 to 3. ]

The hexagonal perovskite-related compound in the present embodiment is a compound having a layered structure containing hexagonal perovskite units or a compound having a structure similar thereto.

In the compound contained in the solid electrolyte in the present embodiment, in the formula (1), the average ionic radius of A is 1.10 to 1.83 Å, the average ionic radius of B is 0.73 to 1.24 Å, and the average of M Preferably, the ionic radius is 0.20 to 0.50 Å, and the average ionic radius of X is 1.10 Å to 1.68 Å.
When the ionic radius of each element is within this range, a crystal structure suitable for functioning as an ionic conductor can be obtained.

Further, in the compound contained in the solid electrolyte in the present embodiment, it is also preferable that the anion X in the formula (1) is O and the w is the amount of oxygen deficiency.

Moreover, it is also preferable that the solid electrolyte in the present embodiment contains a palmierite-type compound. Here, a palmierite-type compound refers to a compound having a structure similar to or similar to that of the mineral palmierite. More specifically, AX ₃ layers and/or AX _3-δ layers packed with A cations and X anions are hexagonally close-packed h-layers and anion-deficient cubic close-packed c-layers are . . c'hhc'hhc'hh . Here, _δ is a real number of 0 or more and 2 or less.
Also, the compound contained in the solid electrolyte in the present embodiment is preferably an electric conductor that conducts ions and/or electrons other than Ba ²⁺ and K ⁺ . Here, ions and/or electrons broadly include charged particles such as oxygen ions, protons (hydrogen ions), electrons, electron holes, and other charged atoms and molecules.

Also, the compound contained in the solid electrolyte in this embodiment is preferably a rubidium ion conductor, an oxide ion conductor, a proton conductor, an electron conductor, or a mixed conductor thereof.
Oxide ion conductors have been known and can be suitably used as solid electrolytes for fuel cells. Oxide ion-electron mixed conductors are expected as electrode materials for fuel cells. Since the proton conductivity of the proton conductor is relatively high at low temperatures, a solid electrolyte for low temperature operation type fuel cells can be obtained.

Further, in the compound contained in the solid electrolyte in the present embodiment, A of the compound is a cation containing at least Rb, and B is at least one of Gd, La, Nd, Sm, Eu, Tb, and Bi. It is also preferred that M is a cation containing at least Mo. In addition, each of A, B, M, and X may consist of a plurality of elements.

The compounds contained in the solid electrolyte in the present embodiment are Rb5Gd(MoO4) ₄ , _Rb5La ( _MoO4 ) ₄ , _{Rb5Nd ( MoO4} ) ₄ , _{Rb5Sm ( MoO4} ) ₄ , _Rb5Eu ( _MoO4 ) ₄ , _Rb5Tb ( _MoO4 ) ₄ , _{Rb5Bi ( MoO4} ) ₄ , _{Rb5Pr ( MoO4} ) _{4 , Rb4.9Bi1.1Mo4O16.1 ,} or Rb _4.5 Ba _0.5 GdMo ₄ O _16.25 .
In particular, Rb ₅ Tb(MoO ₄ ) ₄ , Rb ₅ Bi(MoO ₄ ) ₄ , or Rb _4.5 Ba _0.5 GdMo ₄ O _16.25 are hitherto unreported compounds, and , functions as various ionic or electronic conductors have not been known so far.

Moreover, it is particularly preferable that the compound contained in the solid electrolyte in the present embodiment is Rb ₅ Gd(MoO ₄ ) ₄ .

FIG. 1 shows the crystal structure of Rb ₅ Gd(MoO ₄ ) ₄ among the compounds of formula (1). Rb ₅ Gd(MoO ₄ ) ₄ has a palmierite structure, which is a kind of hexagonal perovskite structure. Random occupancy of Rb and Gd is seen, both occupancy ratios being 0.5. Crystals of the compounds of the present embodiment, including the compounds shown in the figure, have an oxygen-deficient layer (c' layer). It is believed that ions can be conducted through this oxygen-deficient layer. In particular, the c' layer of the compound shown in the figure is believed to be capable of conducting oxygen ions O ²⁻ .

The compounds of this embodiment have high ionic conductivity comparable to the conventional material YSZ. Specifically, the total electrical conductivity (σ tot ) of Rb ₅ Gd(MoO ₄ ) ₄ under dry air at 300° C. shows a value of 5.8×10 ⁻⁶ ( _Scm ⁻¹ ). It shows a value similar to the conductivity.

In addition, in a wide oxygen partial pressure range of 10 ⁻²¹ to 0.2 atm, the total electrical conductivity is almost constant without depending on the oxygen partial pressure, and the stability is high. It is suggested that in the compound of the present embodiment, ionic conduction is dominant over electron conduction and hole conduction.

(Hexagonal perovskite-related compound: A _2-x B _1-y M _1-z X _5-w )
One aspect of the compound of the present embodiment is a solid electrolyte containing a hexagonal perovskite-related compound, the compound being represented by the following general formula (2).
A _2-x B _1-y M _1-z X _5-w (2)
[In the formula (2), A is a cation, and the defect amount x of A is a numerical value of -1 to 1. B is a cation, and the defect amount y of B is a numerical value of -0.5 to 0.5. M is a cation, and the missing amount z of M is a numerical value from -0.5 to 0.5. X is an anion, and w is the amount of deficiency of the anion X, which is a numerical value from -1 to 1. ]

The compound contained in the solid electrolyte in the present embodiment is preferably an α-Ba ₂ ScAlO ₅ type compound or a β-Ba ₂ ScAlO ₅ type compound in the formula (2).
Here, the α-Ba ₂ ScAlO ₅ -type compound or the β-Ba ₂ ScAlO ₅ -type compound takes the α-type or β-type even if Ba ₂ ScAlO ₅ is Ba ₂ ScAlO ₅ as the chemical formula of the crystal. Refers to a crystal structure similar to a crystal. Which crystal structure to adopt can be adjusted by the composition ratio at the time of synthesizing the crystal. For example, when Ba ₂ ScAlO ₅ is synthesized so that the composition ratio is Ba ₂ ScAlO ₅ , it becomes β-Ba ₂ ScAlO ₅ type, and is synthesized so that the composition ratio is Ba ₂ Sc _0.83 Al _1.17 O ₅ . In this case, α-Ba ₂ ScAlO ₅ type crystals are obtained. Hereafter, β-Ba ₂ ScAlO ₅ is simply Ba ₂ ScAlO ₅ , α-Ba ₂ ScAlO ₅ is simply Ba ₂ Sc _0.83 Al _1.17 O _{5 ,} or α-Ba ₂ Sc _0.83 Al _1.17 O ₅ It is sometimes written as

The compound contained in the solid electrolyte in this embodiment is also preferably an electric conductor that conducts ions and/or electrons.

When M is Sc, the best characteristics are exhibited when B is Al and x = 0 and y = 0. When M is Lu, B is Al and x = 0.1 and y = -0.1. The best characteristics are exhibited when

In the compound contained in the solid electrolyte in this embodiment, in the formula (2), the average ionic radius of A is 1.28 Å to 1.94 Å, the average ionic radius of B is 0.59 Å to 1.04 Å, and the average of M Preferably, the ionic radius is 0.31 Å to 0.47 Å, and the average ionic radius of X is 1.10 Å to 1.68 Å.
When the ionic radius of each element is within this range, a crystal structure suitable for functioning as an ionic conductor can be obtained.

Further, in the compound contained in the solid electrolyte in the present embodiment, it is preferable that the anion X in the formula (2) is O and the w is the amount of oxygen deficiency.

Further, in the compound contained in the solid electrolyte in the present embodiment, in the formula (2), A is a cation containing at least Ba, B is a cation containing at least Sc, Lu or In, and M is at least Al. It is preferably a cation containing In addition, each of A, B, M, and X may consist of a plurality of elements.

Further, the compound contained in the solid _electrolyte in the present _embodiment is _Ba2InAlO5 , _{Ba2ScAlO5 , Ba2Sc0.87Al1.13O5 , Ba2LuAlO5 , or Ba2Lu0.9Al .} It is preferably _{1.1 O5} .

Further, the compounds contained in the solid electrolyte in the present embodiment are Ba ₂ ScAlO ₅ , Ba ₂ Sc _0.87 Al _1.13 O ₅ , Ba ₂ LuAlO ₅ , Ba ₂ ScAl _0.9 Ga 0.9 Ga 0.87 Al 1.13 O 5 , Ba 2 LuAlO 5 _{. 1O5 , Ba2ScAl0.95Ga0.05O5 , Ba2Sc0.95Ga0.05AlO5 , Ba2Sc0.95Ca0.05AlO4.976 , Ba2Sc0 . _ _ _ _ _ _ 95Mg0.05AlO4.975 , Ba2Sc0.95Zr0.05AlO5.025 , Ba2Lu0.98Al1.02O5 , Ba2Lu0.96Al1.04O5 _ _ _ _ _ _ _ _ , Ba2Lu0.95Al1.05O5 , Ba2Lu0.94Al1.06O5 , Ba2Lu0.93Al1.07O5 , Ba2Lu0.9Al1.1 _ _ _ _ _ _ _} O ₅ , or Ba ₂ Lu _0.8 Al _1.2 O ₅ , Ba ₂ Lu _0.9 Al _1.1 O ₅ or Ba ₂ Lu _0.8 Al _1.2 O ₅ is more preferable. These compounds are compounds that have never been reported before, and their functions as various ionic and/or electronic conductors have not been known so far.

FIG. 2 shows the crystal structure of Ba ₂ Sc _0.83 Al _1.17 O ₅ , FIG. 3 shows Ba ₂ ScAlO ₅ , and FIG. 4 shows the crystal structure of Ba ₂ LuAlO ₅ among the compounds of the formula (2). Ba ₂ Sc _0.83 Al _1.17 O ₅ is obtained as an α-type crystal of Ba ₂ ScAlO ₅ when each element is synthesized in this composition ratio, so α-Ba ₂ ScAlO ₅ or α-Ba _{It is} also _written as _{2Sc0.83Al1.17O5} . On the other hand, Ba ₂ ScAlO ₅ is also expressed as β-Ba ₂ ScAlO ₅ because it is obtained as a β-type crystal when each element is synthesized in this composition ratio.
As shown in the figure, there is an essential oxygen-deficient layer (h' layer) in these crystal structures. It is believed that ions can be conducted through this oxygen-deficient layer. In particular, the h' layer of this compound is believed to be capable of conducting protons.

Also, by changing the values of y and z as described above, and by changing the Lu/Al ratio, different properties can be obtained. A compound in which the compound is Ba ₂ Lu _0.9 Al _1.1 O ₅ has even higher conductivity, and can exhibit conductivity comparable to conventionally known typical proton conductors. This compound can exhibit electrical conductivity exceeding BaCe _0.9 Y _0.1 O _2.95 , especially at low temperatures of 300-700°C.

Among the compounds of formula (2), β-Ba ₂ ScAlO ₅ has a transference number of 99% at 200 to 600 ° C for the temperature dependence of the total electrical conductivity in the electrolyte region (P(O ₂ ) ~ 10 ^-20 atm). That's it. Therefore, it is considered that proton conductivity is dominant in electrical conductivity.

Comparing the proton conductivity, the compound of formula (2) is comparable to representative proton conductors in the prior art, such as La _0.8 Ba _1.2 GaO _3.9 (LBGO), La _0.99 Ca _{0.01 NbO3.995} ( _LaNbO4 ), _La26O27 ( _BO3 ) ₈ ( _LBO ), _{La5.4MoO11.1 ( LMO} ), or _{La0.9Sr0.1PO3.95 ( LaPO4} ), it can show a very high value.

(Ba ₇ Sc ₆ Al ₂ O ₁₉ type compound: A _7-x B _6-y M _2-z X _19-w )
One aspect of the compound of the present embodiment is a solid electrolyte containing a Ba ₇ Sc ₆ Al ₂ O ₁₉ type compound, and the compound is a compound represented by the following general formula (3).
A _7-x B _6-y M _2-z X _19-w (3)
[In the formula (3), A is a cation, and the missing amount x of A is a numerical value of 0 to 3.5. B is a cation, and the missing amount y of B is a numerical value of 0-3. M is a cation, and the missing amount z of M is a numerical value of 0-1. X is an anion, w is the amount of deficiency of the anion X, and has a value of -3 to 3. ]
The Ba ₇ Sc ₆ Al ₂ O ₁₉ type compound is one of the hexagonal perovskite-related compounds and is a compound having the same or similar crystal structure as Ba ₇ Sc ₆ Al ₂ O ₁₉ . Specifically, the structure is shown in FIG. 5, which will be described later, and is a structure in which ₉ layers of Ba ₃ Sc ₄ O and ₅ layers of β-Ba ₂ ScAlO are alternately laminated. More specifically, the compound of formula (3) has a similar or similar crystal structure to Ba ₇ Sc ₆ Al ₂ O ₁₉ .

In the compound contained in the solid electrolyte in the present embodiment, in the above formula (3), the average ionic radius of A is 1.28 to 1.94 Å, the average ionic radius of B is 0.59 to 0.90 Å, and the average of M Preferably, the ionic radius is 0.31 to 0.47 Å, and the average ionic radius of X is 1.10 Å to 1.68 Å.
When the ionic radius of each element is within this range, a crystal structure suitable for functioning as an ionic conductor can be obtained.

In the compound contained in the solid electrolyte in the present embodiment, it is also preferable that the anion X is O in the formula (3), and the w is the amount of oxygen deficiency. Also, the oxygen deficiency amount w may be a value of -2 to 2.

In the compound contained in the solid electrolyte in the present embodiment, in the formula (3), A is a cation containing at least Ba, B is a cation containing at least Sc, and M is a cation containing at least Al. is preferred. In addition, each of A, B, and M may be composed of a plurality of types of elements.

_{Compounds contained} in the _{solid electrolyte in this embodiment are Ba7Sc6Al2O19 , Ba6.3K0.7Sc6Al2O18.65 , Ba6.3Sr0.7Sc6Al2 O19 , Ba7Sc5.4Mg0.6Al2O19.3 , Ba7Sc5.4Tb0.6Al2O19.3 , or Ba7Sc5.4Zr0.6Al2 _ _ _ _ _ _ _} O is preferably _19.3 .

FIG. 5 shows the crystal structure of Ba ₇ Sc ₆ Al ₂ O ₁₉ among the compounds of formula (3).
As shown in the figure, there is an essential oxygen-deficient layer (h' layer) in this crystal structure. It is believed that ions can be conducted through this oxygen-deficient layer. In particular, the h' layer of this compound is believed to be capable of conducting protons.

The compound of formula (3) has the property that the conductivity is improved in a wet atmosphere as compared to a dry atmosphere. Therefore, it is considered that proton conductivity is dominant in electrical conductivity.

Comparing the proton conductivity, the compound of formula (3) is comparable to representative proton conductors in the prior art, such as La _0.8 Ba _1.2 GaO _3.9 (LBGO), La _5.4 MoO _11.1 (LMO) or La _0.9 Sr _0.1 PO _3.95 (LaPO ₄ ), extremely high values can be shown.

(Properties of ionic conduction of the compound of the present embodiment)
In this embodiment, it is conceivable that the compound having the above-mentioned conditions has properties as various ion conductors. In particular, it is assumed that the above-mentioned compounds will provide effective electrical conductivity (oxide ion conductivity) when used as proton conductors or solid electrolytes. A proton conductor is a compound that conducts electricity by conduction (movement) of protons (hydrogen ions, H ⁺ ). Further, the solid electrolyte using the compound of the present embodiment is preferably used under temperature conditions of 200 to 1200°C, more preferably under temperature conditions of 200 to 1000°C, and is used at 200°C or more and less than 700°C. is more preferable, and it is particularly preferable to use at 200 to 600°C. By using this temperature condition, it is possible to stably operate in a wider temperature range than the conventional fuel cell, so that there are few restrictions on the devices and layout required for operation, and a wide range of applications can be obtained.
A solid electrolyte using the compound of the present embodiment can also be operated at temperatures exceeding 600° C., such as SOFC.

When the electrical conductivity of the solid electrolyte of the present embodiment is measured at about 200° C., the electrical conductivity represented by log[σ(Scm ⁻¹ )] is preferably −7.0 or more, and −5. It is more preferably 0 or more. Since the electrical conductivity at 200° C. is sufficiently high, it has high electrical conductivity at low temperatures and can be used particularly well in batteries and other devices that operate at low temperatures.

(Solid electrolyte layer)
In addition, the solid electrolyte of the present embodiment can be formed into a layered structure, or formed to be included in a layered structure, and used as a solid electrolyte layer. The solid electrolyte layer may contain an ion conductor or the like other than the solid electrolyte of the present embodiment. In order for the battery or the like using the solid electrolyte of the present embodiment to exhibit high electrical conductivity, and particularly to operate effectively as a low-temperature operating battery described later, for example, 50% by mass or more, preferably 70% by mass, of the solid electrolyte layer % or more of the solid electrolyte containing the hexagonal perovskite-related compound of the present embodiment.

(Battery containing solid electrolyte or solid electrolyte layer)
The solid electrolyte of the present embodiment or an electrolyte layer containing this solid electrolyte can be used in a battery containing this. Among them, the solid electrolyte of the present embodiment can be particularly suitably used for fuel cells as described above.

A battery using the solid electrolyte of the present embodiment or an electrolyte layer containing this solid electrolyte can be particularly suitably used as a low-temperature operating battery. In the present embodiment, the low-temperature operating battery is a battery that operates at 200 to 1200°C, preferably 200 to 1000°C, more preferably 200 to 700°C, and most preferably 200 to 600°C, as described above.

The battery in this embodiment includes, for example, an anode, a cathode, and the solid electrolyte layer interposed therebetween. The cathode and solid electrolyte may form an integrated cathode-solid electrolyte layer assembly.

(Other uses of solid electrolyte)
Conventionally, perovskite-related compounds and solid electrolytes containing them show high ionic conductivity, so they are widely applied to batteries, sensors, ion concentrators, membranes used for ion separation and permeation, and catalysts. However, the solid electrolyte of the present embodiment can be applied similarly to these. For example, the solid electrolyte of the present embodiment can be used for fuel cells, other batteries, sensors, electrodes, electrolytes, element concentrators, element separation membranes, element permeable membranes, element pumps, catalysts, photocatalysts, electrical/electronic/communication equipment. , energy/environment-related devices, optical devices, and the like.

The solid electrolyte layer of the present embodiment described above can be particularly suitably used for fuel cells, sensors, and the like.

The solid electrolyte of the present embodiment can be used, for example, as an electrolyte for a gas sensor as a sensor. A gas sensor, a gas detector, or the like can be constructed by attaching a sensitive electrode corresponding to a gas to be detected on the electrolyte. For example, a carbon dioxide gas sensor is obtained by using a sensitive electrode containing carbonate, a NOx sensor is obtained by using a sensitive electrode containing nitrate, and a SOx sensor is obtained by using a sensitive electrode containing sulfate. Also, by assembling an electrolytic cell, it is possible to construct a device for collecting or decomposing NOx and/or SOx contained in the exhaust gas.

It can be used as the solid electrolyte of the present embodiment, an adsorbent such as ions, an adsorption/separation agent, or various catalysts.
In the solid electrolyte of this embodiment, various rare earth elements in the ion conductor may also act as an activator to form a luminescent center (color center). In this case, it can be used as a wavelength changing material or the like.
The solid electrolytes of the present embodiments may also be made superconductors by doping with electron or hole carriers.

The solid electrolyte of the present embodiment also uses the solid electrolyte as an ionic conductor, adheres to the surface thereof an inorganic compound or the like that is colored or discolored by the insertion/extraction of conductive ions, and furthermore, has a translucent electrode such as ITO on it. It is also possible to fabricate an all-solid-state electrochromic device by forming By using this all-solid-state electrochromic device, an electrochromic display having memory characteristics with reduced power consumption can be provided.

(Method for producing solid electrolyte)
In the method for producing a solid electrolyte of the present embodiment, the compound is produced by a solid phase reaction method.

The solid phase reaction method can be performed by conventionally known steps. For example, the starting raw materials are mixed so that the molar ratio of the elements of the starting materials becomes the desired chemical composition, pressed to form pellets, and fired to obtain a hexagonal perovskite-related compound.
First, a starting material containing elements having a desired chemical composition is prepared. The starting material may be pre-dried. Drying can be performed at 200 to 1000° C. for 5 to 20 hours using an electric furnace or the like.
The starting materials are then mixed to achieve the desired chemical composition with the molar ratio of the elements. The composition of the molar ratio can be based on the molar ratio of cations. Mixing-grinding can be carried out as appropriate. For example, using an agate mortar, dry mixing-grinding and wet mixing-grinding using ethanol can be repeated for 0.5 to 2 hours.
The resulting mixture is pressed into pellets. Molding can be performed by applying pressure after calcining the mixture. Calcination can be carried out at 300 to 1100° C. for 5 to 24 hours using an electric furnace or the like. After calcination, pulverization and the above mixing and grinding may be performed again. The mixture is formed into pellets at 62-150 MPa. The molded pellets are fired under the conditions described later.

When the compound is a compound represented by the general formula (1), the compound is preferably fired in the air at 300 to 500°C for 2 to 8 hours and then at 500 to 700°C for 6 to 24 hours. .
More preferably, the firing is carried out at 350-450° C. for 3-5 hours, followed by firing at 550-650° C. for 11-13 hours.
When the compound is a compound represented by the general formula (1), the mixing and grinding is preferably carried out in a wet manner, and the calcination step may be omitted.

When the compound is represented by the general formula (2) or (3), it is calcined at 1500 to 1700° C. for 3 to 24 hours in the atmosphere.
More preferably, the firing is performed at 1550 to 1650° C. for 8 to 13 hours.

The compound of the present embodiment can be effectively produced by these production method, synthesis method and firing conditions. In particular, the compounds Ba ₂ LuAlO ₅ and Ba ₂ Lu _0.9 Al _1.1 O ₅ of (2) are new substances, and no compounds with similar compositions exist in the past, and no synthesis method has been established. However, the inventors of the present invention investigated and found out the manufacturing conditions. This production condition is particularly useful as the production condition for the above compound.

EXAMPLES The present embodiment will be described below with reference to examples, but the present invention is not limited to the following examples.

(Test example 1)
(Investigation of properties of _Rb5Gd ( _{MoO4)4 )}
In finding useful hexagonal perovskite-related compounds, the present inventors focused on Rb ₅ Gd(MoO ₄ ) ₄ which showed the 22nd lowest value among 529 hexagonal perovskite-related oxides in the inorganic crystal structure database. did.
FIG. 6 shows a histogram of the energy barrier (E _b ) estimated by BVEL. As shown in the figure, Rb ₅ Gd(MoO ₄ ) ₄ had the lowest E _b excluding known materials and materials with possible electronic conductivity. Therefore, Rb ₅ Gd(MoO ₄ ) ₄ was focused on as a candidate for a useful compound.

(Example 1: Synthesis of _Rb5Gd ( _{MoO4)4 )}
A Rb ₅ Gd(MoO ₄ ) ₄ compound was prepared by a solid phase reaction method using the following means. Rb ₂ CO ₃ , Gd ₂ O ₃ and MoO ₃ were used as starting materials. The starting materials were dried in advance at 300° C. for 6 hours in an electric furnace, and then weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Using an agate mortar, wet mixed grinding with ethanol was repeated for 1 hour. The mixture was molded into cylindrical pellets with a diameter of 10 mm by pressing at 62-150 MPa using a uniaxial press. The obtained pellets were sintered at 400° C. for 4 hours in air and then at 600° C. for 12 hours. As a result, sintered pellets were obtained.

The production phase of the obtained compound was evaluated by X-ray diffraction (XRD). A portion of the sintered body was ground with a tungsten carbide (WC) grinder for 20 minutes and then ground with an agate mortar for 30 minutes to 1 hour. Powder XRD measurement was performed using the obtained powder. Powder X-ray diffraction measurement was performed using BRUKER D8 and Rietveld analysis using Z-Code. FIG. 7 shows the results of XRD measurement. Rietveld analysis was performed with a three-sided phase with a palmierite-type structure. The space group supported by the analysis was R-3m, with lattice constants a = b = 6.118 Å and c = 21.44 Å.

(Measurement of electrical conductivity of _Rb5Gd ( _{MoO4)4 )}
The total electrical conductivity of the obtained compound of Example 1 was measured by a DC four-probe method. A pellet having a diameter of 5 mm was formed by uniaxial pressing and sintered at 600° C. for 12 hours to prepare a sample for conductivity measurement. In the direct current four-terminal method, four platinum wires were wound around the sintered body, and platinum paste was applied to the platinum wires in order to adhere the sample to the platinum wires. The platinum paste was heated at 600° C. for 1 hour to remove organic substances contained in the platinum paste. Measurement temperature range was 200 to 650° C., and measurement was performed under dry air (100 mL/min, water vapor partial pressure: <10 ⁻⁶ atm).

The results are shown in FIG. At 300° C., σ _tot of Rb ₅ Gd(MoO ₄ ) ₄ was comparable to σ _b of YSZ. Rb ₅ Gd(MoO ₄ ) ₄ has σ _tot =5.8×10 ⁻⁶ (Scm ⁻¹ ) at 306° C. and YSZ has σ _b =5.0×10 ⁻⁶ (Scm ⁻¹ ) at 300° C. . This result indicates that Rb ₅ Gd(MoO ₄ ) ₄ is a material exhibiting electrical conductivity comparable to that of YSZ, which is a conventionally known practical material.

(Oxygen partial pressure dependence of total electrical conductivity of Rb ₅ Gd(MoO ₄ ) ₄ )
Next, the oxygen partial pressure dependence of the total electrical conductivity of Example 1 was measured. Samples were prepared as described above (total conductivity measurement). Oxygen O ₂ gas, nitrogen N ₂ gas, and N ₂ /H ₂ mixed gas were used to control the oxygen partial pressure. Oxygen partial pressure was monitored using an oxygen sensor installed downstream of the apparatus. _The oxygen partial pressure was controlled by mixing a small amount of the _N2 /H2 gas mixture into the nitrogen gas.
The measured electrical conductivity log ₁₀ [σ t t ( _Scm ^-1 )] is plotted on the vertical axis against the oxygen partial pressure log ₁₀ [P(O ₂ )/atm] on the horizontal axis.
FIG. 9 shows the results of measuring the total electrical conductivity for each temperature and oxygen partial pressure. From the measurement of the oxygen partial pressure dependence of the total electrical conductivity for Rb ₅ Gd(MoO ₄ ) ₄ , 650° C.: 5.0×10 ⁻²¹ to 0.10 atm, 500° C.: 6.9×10 ⁻²¹ to 0 .01 atm, 400° C.: Electrolyte regions were observed in the regions of 1.8×10 ⁻²¹ to 0.99 atm. It was suggested that ionic conduction is more dominant than electron conduction and hole conduction in this compound. This compound has a wide electrolyte region in the range of 10 ^-21 to 0.1 atm, and has a stability superior to that of conventionally known bismuth oxide and ceria-based materials, suggesting that it is highly practical.

(Measurement of UV-vis spectrum of Rb ₅ Gd(MoO ₄ ) ₄ )
FIG. 10 shows the results (Tauc plot) of UV-vis spectrum measurement of the compound of Example 1 obtained. The bandgap of Rb ₅ Gd(MoO ₄ ) ₄ was estimated by assuming a direct transition from the measurement results of the UV-Vis spectrum. The bandgap of Rb ₅ Gd(MoO ₄ ) ₄ assuming direct transition was estimated to be 4.32 eV. This result suggested that Rb ₅ Gd(MoO ₄ ) ₄ is not an intrinsic semiconductor.

(Test example 2)
₍ Example ₂ : _{Synthesis of Ba2Sc0.83Al1.17O5 )}
A Ba ₂ Sc _0.83 Al _1.17 O ₅ (α-Ba ₂ ScAlO ₅ ) compound was produced by a solid phase reaction method using the following means. BaCO ₃ , Sc ₂ O ₃ and Al ₂ O ₃ were used as starting materials. The starting materials were dried in advance at 300° C. for 10 hours in an electric furnace, and then weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Using an agate mortar, dry mixed-grinding and wet mixed-grinding with ethanol were repeated for 1 to 2 hours. The resulting mixture was calcined in an electric furnace at 900° C. to 1000° C. for 10 to 12 hours. The calcined mixture was repeatedly subjected to wet mixed grinding and dry mixed grinding using ethanol in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets with a diameter of 20 mm by pressing at 62-150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered at 1600° C. for 10 hours in the atmosphere. As a result, pellets, which are sintered bodies, were obtained.

The production phase of the obtained compound of Example 2 was evaluated by X-ray diffraction (XRD). A portion of the sintered body was ground with a tungsten carbide (WC) grinder for 20 minutes and then ground with an agate mortar for 30 minutes to 1 hour. Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above. The results of this XRD measurement are shown in FIG. a = 5.778 Å and c = 14.54 Å in space group P6 ₃ /mmc. In addition to Ba ₂ Sc _0.83 Al _1.17 O ₅ as a measurement result, α-Ba ₂ ScAlO ₅ simulation as a calculation prediction is also shown. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

(Example ₃ : Synthesis of _Ba2ScAlO5 )
A Ba ₂ ScAlO ₅ (β-Ba ₂ ScAlO ₅ ) compound was prepared by a solid phase reaction method using the following means. BaCO ₃ , Sc ₂ O ₃ and Al ₂ O ₃ were used as starting materials. The starting materials were dried in advance at 300° C. for 10 hours in an electric furnace, and then weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Using an agate mortar, dry mixed-grinding and wet mixed-grinding with ethanol were repeated for 1 to 2 hours. The resulting mixture was calcined in an electric furnace at 900° C. to 1000° C. for 10 to 12 hours. The calcined mixture was repeatedly subjected to wet mixed grinding and dry mixed grinding using ethanol in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets with a diameter of 20 mm by pressing at 62-150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered at 1600° C. for 10 hours in the atmosphere. As a result, pellets, which are sintered bodies, were obtained.

The production phase of the obtained compound was evaluated by X-ray diffraction (XRD). A portion of the sintered body was ground with a tungsten carbide (WC) grinder for 20 minutes and then ground with an agate mortar for 30 minutes to 1 hour. Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above. The results of this XRD measurement are shown in FIG. It was a = 5.806 Å and c = 19.46 Å in the space group P6 ₃ /mmc. In addition to Ba ₂ ScAlO ₅ as a measurement result, β-Ba ₂ ScAlO ₅ simulation as a calculation prediction is also shown. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

_{( Electrical conductivity} of _{Ba2Sc0.83Al1.17O5 , Ba2ScAlO5} )
The temperature dependence of the total electrical conductivity of the obtained compounds of Examples 2 and 3 was examined. The total electrical conductivity was measured by the DC 4-probe method, the measurement temperature range was 200 to 1200 ° C., σ _wet : in moist air (P (H ₂ O) = 0.02 atm), σ _dry : in dry air (P ( H ₂ O)<10 ⁻⁵ atm), respectively.
The results are shown in FIG. The figure is an Arrhenius plot, in which "α-Ba ₂ ScAlO ₅ " is Ba ₂ Sc _0.83 Al _1.17 O _{5 and} "β-Ba ₂ ScAlO ₅ " is Ba ₂ ScAlO ₅ . From the results in the figure, the conductivity in wet air was higher than in dry air, suggesting proton conduction.

(Dependence of electrical conductivity of Ba ₂ Sc _0.83 Al _1.17 O _{5 and} Ba ₂ ScAlO ₅ on oxygen partial pressure)
Next, FIG. 15 shows the results of measuring the electrical conductivity for each temperature and oxygen partial pressure. The oxygen partial pressure was measured in the same manner as in Test Example 1. “α-Ba ₂ ScAlO ₅ ” in FIG. 14(a) is Ba ₂ Sc _0.83 Al _1.17 O ₅ of Example 2, and “β-Ba ₂ ScAlO ₅ ” in FIG. Ba ₂ ScAlO ₅ of Example 3. In a moist atmosphere, the conductivity was almost constant at an oxygen partial pressure of 10 ⁻⁵ atmospheres or less, and the contribution of electron and hole conduction was small, suggesting proton conduction.

₍ Transfer number evaluation of _Ba2ScAlO5 )
The proton conductivity of Ba ₂ ^ScAlO ₅ of Example 2 is shown in FIG. )Pointing out toungue. Temperature dependence of total electrical conductivity in the electrolyte region (P(O ₂ ) ~ 10 ^-20 atm) of β-Ba ₂ ScAlO ₅ The transference number calculated by the following formula at 200 ~ 600 ° C. , the proton conductivity is considered to be dominant. The proton conductivity σ _H+ and the proton transport number t _H+ were estimated by the following equations using the total electrical conductivity σ _wet in the wet atmosphere and the total electrical conductivity σ _dry in the dry atmosphere.
t _H+ = σ _H+ / σ _wet = (σ _wet - σ _dry) / σ _wet

Further, FIG. 16 shows an Arrhenius plot comparing the proton conductivity of Ba ₂ Sc _0.83 Al _1.17 O _{5 and} Ba ₂ ScAlO ₅ of Examples 2 and 3 with that of a conventional conductor. For the vertical axis, σ _H+ = σ _wet - σ _dry . Typical proton conductors in the prior art _such as _{La0.8Ba1.2GaO3.9} ( _LBGO ), _{La0.99Ca0.01NbO3.995 ( LaNbO4} ), _{La26O27 ( BO 3} ) ₈ (LBO), La _5.4 MoO _11.1 (LMO), or La _0.9 Sr _0.1 PO _3.95 (LaPO ₄ ). rice field.

(Test example 3)
(Example ₄ : Synthesis of _Ba2LuAlO5 )
A Ba ₂ LuAlO ₅ compound was prepared by a solid state reaction method using the following means. BaCO ₃ , Lu ₂ O ₃ and Al ₂ O ₃ were used as starting materials. The starting materials were dried in advance at 300° C. in an electric furnace for 2 to 14 hours, and then weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Using an agate mortar, dry mixed-grinding and wet mixed-grinding with ethanol were repeated for 1 to 2 hours. The resulting mixture was calcined in an electric furnace at 900° C. to 1000° C. for 10 to 12 hours. The calcined mixture was repeatedly subjected to wet mixed grinding and dry mixed grinding using ethanol in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets with a diameter of 10-20 mm by pressing at 62-150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered at 1600° C. for 10 hours in the atmosphere. As a result, pellets, which are sintered bodies, were obtained.

The production phase of the obtained compound was evaluated by X-ray diffraction (XRD). A portion of the sintered body was ground with a tungsten carbide (WC) grinder for 20 minutes, and then ground with an agate mortar for 30 minutes to 1 hour. Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above. The results of this XRD measurement are shown in FIG. It was a = 5.927 Å and c = 19.82 Å in the space group P6 ₃ /mmc.

₍ Electrical conductivity of _Ba2LuAlO5 )
The temperature dependence of the total electrical conductivity of the obtained compound of Example 4 was examined. The total electrical conductivity was measured by the direct current 4-probe method, the measurement range was 300 to 1200°C, the temperature dependence of the total electrical conductivity and the P(O ₂ ) dependence (relative density ~ 73%) σ _wet : wet air Medium (P(H ₂ O) = 0.021 atm) σ _dry : In dry air (P(H ₂ O) < 10 ^-5 atm).
The results are shown in FIG. The figure is an Arrhenius plot. From the results in the figure, the conductivity in wet air was higher than in dry air, suggesting proton conduction.

₍ Oxygen partial pressure dependence of electrical conductivity of _Ba2LuAlO5 )
Next, FIG. 19 shows the results of measuring the total electrical conductivity of Example 4 in a humid atmosphere at each temperature and oxygen partial pressure in the figure. The oxygen partial pressure was measured in the same manner as in Test Example 1. In a moist atmosphere, the conductivity was almost constant regardless of the partial pressure of oxygen, and the contribution of electron and hole conduction was small, suggesting proton conduction.

₍ Transfer number evaluation of _Ba2LuAlO5 )
The proton conductivity was estimated from the difference in the total electrical conductivity of Ba ₂ LuAlO ₅ of Example 4 in wet air and dry air, and the results of the transference number calculated using this value are shown in FIG. Ba ₂ LuAlO ₅ has a high proton transference number in the range of about 200 to 800° C., and protons are the main carrier. Especially at 200 to 600°C, almost no decrease in proton transference number was observed even when the temperature was increased.

Also, for Ba ₂ LuAlO ₅ (Example 4) and Ba ₂ Lu _0.9 Al _1.1 O ₅ (Example 5), the proton capacity estimated from the difference in total electrical conductivity in wet air and dry air A comparison of conductivity with a conventional conductor is shown in FIG. Ba ₂ Lu _0.9 Al _1.1 O ₅ of Example 5 was synthesized in the same manner as Ba ₂ LuAlO ₅ except for the mixing ratio during synthesis. For the vertical axis, σ _H+ =σ _wet -σ _dry . All of them showed values almost comparable to BaCe _0.9 Y _0.1 O _2.95 , a typical proton conductor in the prior art, and showed values exceeding particularly at low temperatures. Also _compared to _, for example, _{La0.8Ba1.2GaO3.9} ( _LBGO ), _La5.4MoO11.1 ( _LMO ), or _{La0.9Sr0.1PO3.95 ( LaPO4} ) However, it was shown to show extremely high values. In particular, Ba ₂ Lu _0.9 Al _1.1 O ₅ with a different Lu/Al ratio exceeds BaCe _0.9 Y _0.1 O _2.95 at a low temperature of 400° C. or lower, showing usefulness. rice field.

(Test example 4)
₍ Example ₆ : _Synthesis of _Ba7Sc6Al2O19 )
A Ba ₇ Sc ₆ Al ₂ O ₁₉ compound was prepared by a solid phase reaction method using the following means. BaCO ₃ , Sc ₂ O ₃ and Al ₂ O ₃ were used as starting materials. The starting materials were dried in advance at 300° C. in an electric furnace for 3 to 14 hours, and then weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Using an agate mortar, dry mixed-grinding and wet mixed-grinding with ethanol were repeated for 1 to 2 hours. The resulting mixture was calcined in an electric furnace at 900° C. to 1000° C. for 10 to 12 hours. The calcined mixture was repeatedly subjected to wet mixed grinding and dry mixed grinding using ethanol in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets with a diameter of 10-20 mm by pressing at 62-150 MPa using a uniaxial press. The pellets thus obtained were placed in an electric furnace, sintered at 1600° C. for 10 hours in the atmosphere, and then rapidly cooled. As a result, sintered pellets were obtained.

In order to evaluate the production phase of the obtained compound by X-ray diffraction (XRD), part of the sintered body was pulverized with a tungsten carbide (WC) pulverizer for 20 minutes and then ground with an agate mortar for 30 minutes to 1 hour. crushed. The results of this XRD measurement are shown in FIG. a = 5.806 Å and c = 35.25 Å in the space group P6 ₃ /mmc. In addition to Ba ₇ Sc ₆ Al ₂ O ₁₉ as a measurement result, a simulation as a calculation prediction is also shown. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

_{( Electrical conductivity} of _Ba7Sc6Al2O19 )
The temperature dependence of the total electrical conductivity of the obtained compound of Example 6 was examined. The total electrical conductivity was measured by the DC 4-probe method, the measurement range was 300 to 1200°C, the temperature dependence of the total electrical conductivity and the P(O ₂ ) dependence (relative density ~ 76%) σ _wet : wet air Medium (P(H ₂ O) = 0.021 atm) σ _dry : In dry air (P(H ₂ O) < 10 ^-5 atm).
The results are shown in FIG. The figure is an Arrhenius plot. From the results in the figure, the conductivity in the wet atmosphere was higher than that in the dry atmosphere, suggesting proton conduction.

(Dependence of Ba ₇ Sc ₆ Al ₂ O ₁₉ on oxygen partial pressure)
Next, FIG. 24 shows the results of measuring the total electrical conductivity of Example 6 for each temperature and oxygen partial pressure. The oxygen partial pressure was measured in the same manner as in Test Example 1. There is an oxygen partial pressure range (electrolyte region) where the conductivity is almost constant regardless of the oxygen partial pressure, and the contribution of electron and hole conduction is small, suggesting proton conduction.

Further, FIG. 25 shows a comparison of the proton conductivity of Ba ₇ Sc ₆ Al ₂ O ₁₉ of Example 6 with that of a conventional conductor. For the vertical axis, σ _H+ =σ _wet -σ _dry . It showed a value almost comparable to BaCe _0.9 Y _0.1 O _2.95 , a typical proton conductor in the prior art, and showed a higher value especially at a low temperature of 450° C. or lower. Also, representative proton conductors in the prior art, such as _{La0.8Ba1.2GaO3.9} ( _LBGO ), _{La5.4MoO11.1 ( LMO} ), _{or La0.9Sr0.1} It was shown to show extremely high values even when compared with PO _3.95 (LaPO ₄ ).

(Test Example 5)
(Example 7: Synthesis of _Rb5Bi ( _{MoO4)4 )}
A Rb ₅ Bi(MoO ₄ ) ₄ compound was prepared by a solid phase reaction method using the following means.
Rb ₂ CO ₃ , MoO ₃ , Bi ₂ O ₃ (stoichiometric ratio) were used as starting materials. All starting materials were of high purity chemistry. It was weighed with an electronic balance so that the molar ratio of cations would be the target chemical composition. Synthesis was carried out under the same conditions as in Example 1, except that the sintering was carried out at 400° C. for 4 hours and then at 590° C. for 12 hours.

(Example 8: Synthesis of _Rb5Pr ( _{MoO4)4 )}
A Rb ₅ Pr(MoO ₄ ) ₄ compound was prepared by a solid phase reaction method using the following means.
Rb ₂ CO ₃ , MoO ₃ , Pr ₆ O ₁₁ (stoichiometric ratio) were used as starting materials. All starting materials were of high purity chemistry. It was weighed with an electronic balance so that the molar ratio of cations would be the target chemical composition. Synthesis was carried out in the same manner as in Example 1, except that sintering was carried out at 400° C. for 24 hours and then at 650° C. for 24 hours.

Further, as a reference example, a compound in which A is La, Nd, Sm, Eu, Gd, or Tb in Rb ₅ A(MoO ₄ ) ₄ was similarly synthesized by the solid-phase synthesis method.
FIG. 26 shows a schematic diagram of the crystal structure of Rb ₅ Bi(MoO ₄ ) ₄ obtained based on the peak pattern obtained in the neutron diffraction experiment at 540°C.

A laboratory powder XRD measurement was performed on the resulting compound.
FIG. 27 shows the Rb ₅ Bi(MoO ₄ ) ₄ compound of Example 7, and FIG. 28 shows the laboratory system XRD peak patterns of the Rb ₅ Pr(MoO ₄ ) ₄ compound.
29 shows Rb ₅ La(MoO ₄ ) ₄ compound, FIG. 30 shows Rb ₅ Nd ₍ MoO ₄ ) ₄ compound, FIG. 31 shows Rb ₅ Sm ₍ MoO ₄ ) ₄ compound, and FIG. ) ₄ compounds, and FIG. 33 shows laboratory XRD peak patterns of reference examples of Rb ₅ Tb(MoO ₄ ) ₄ compounds. It was confirmed that each compound was obtained as the main phase.

(Electrical conductivity of _Rb5Bi ( _{MoO4)4 )}
The temperature dependence of the total electrical conductivity of the obtained compound of Example 7 was examined. The total electrical conductivity was measured by the direct current four-probe method, and the measurement range was 50 to 570°C.
The results are shown in FIG. The figure is an Arrhenius plot. Compounds in which A is La, Pr, Nd, Sm, Eu, Gd, and Tb in Rb ₅ A(MoO ₄ ) ₄ of Reference Examples are also shown. That is, "Bi" in the figure is the plot of Example 7. The results in the figure show that when A in the formula is Bi, the electrical conductivity is higher than when it is other cations.
In addition, each compound where A = La, Pr, Nd, Sm, Eu, Gd, and Tb shows a slightly lower conductivity than when A is Bi, but all of them have some applicability. It is believed that there is.

(Dependence of Rb ₅ Bi(MoO ₄ ) ₄ on oxygen partial pressure)
FIG. 35 shows the results of measuring the total electrical conductivity for Example 7 at each temperature and each oxygen partial pressure. The oxygen partial pressure was measured in the same manner as in Test Example 1. The oxygen partial pressure range (electrolyte region) was such that the conductivity was almost constant regardless of the oxygen partial pressure.

FIG. 36 shows the transference numbers of Rb ⁺ and O ²⁻ in Rb ₅ Bi(MoO ₄ ) ₄ estimated by the Tubandt method. O ^2- has a high transference number, suggesting that O ^2- is mainly the conducting species in the Rb ₅ Bi(MoO ₄ ) ₄ compound.

FIG. 37 shows the relationship between bulk conductivity (σ _bulk ) and grain boundary conductivity (σ _gb ) in Rb ₅ Bi(MoO ₄ ) ₄ estimated by the AC impedance method. The conductivity (σ _DC ) by the DC four-terminal method is also shown. As shown in the figure, a result was obtained that the bulk conductivity was higher than the grain boundary conductivity and the conductivity by the direct current four-terminal method (σ _bulk >σ _gb ).

FIG. 38 shows a bulk conductivity comparison for Rb ₅ Bi(MoO ₄ ) ₄ and various oxide ion conductors. It was shown that the bulk conductivity of Rb ₅ Bi(MoO ₄ ) ₄ is higher in any temperature range than known oxide ion conductors in the figure.

(Electrical conductivity of _Rb5Pr ( _{MoO4)4 )}
For the compound of Example 8, the temperature dependence of the total electrical conductivity was investigated. The total electrical conductivity was measured by the direct current four-probe method, and the measurement range was 200 to 650°C.

The results are shown in FIG. A comparison between YSZ, which has been conventionally used as an electrical conductive material, and Ba ₇ MoNb ₄ O ₂₀ , an oxide ion conductor of the same hexagonal perovskite-related oxide, is shown.
The total electrical conductivity of Rb ₅ Pr(MoO ₄ ) ₄ measured in dry air is comparable or superior to that of YSZ at 480-650 °C, and that of Ba ₇ MoNb ₄ O ₂₀ after 480 °C. higher than the conductivity.

₍ Example ₉ : _{Synthesis of Rb4.9Bi1.1Mo4O16.01 )}
A Rb _4.9 Bi _1.1 Mo ₄ O _16.01 compound was prepared by a solid phase reaction method using the following means.
Rb ₂ CO ₃ , MoO ₃ , Bi ₂ O ₃ (stoichiometric ratio) were used as starting materials. All starting materials were of high purity chemistry. It was weighed with an electronic balance so that the molar ratio of cations would be the desired chemical composition. Synthesis was carried out in the same manner as in Example 1, except that sintering was carried out at 400° C. for 24 hours and then at 570° C. for 24 hours.

A laboratory powder XRD measurement was performed on the resulting compound.
Figure _{40 shows the laboratory XRD peak pattern of the Rb4.9Bi1.1Mo4O16.01 compound .} It was confirmed that an Rb _4.9 Bi _1.1 Mo ₄ O _16.01 compound was obtained as the main phase.

(Electrical conductivity of Rb _4.9 Bi _1.1 Mo ₄ O _16.01 )
The temperature dependence of the total electrical conductivity of the obtained compound of Example 7 was examined. The total electrical conductivity was measured by the direct current four-probe method, and the measurement range was 100 to 650°C.
The results are shown in FIG. A comparison between YSZ, which is conventionally used as an electrically conductive material, and the aforementioned Rb ₅ Bi(MoO ₄ ) ₄ is shown.
The total electrical conductivity measured in dry air of Rb _4.9 Bi _1.1 Mo ₄ O _16.01 is higher than the bulk conductivity of the current practical material YSZ at 100-650° C. At 100-500° C., it was found that the overall electrical conductivity of Rb ₅ Bi(MoO ₄ ) ₄ , the world's best oxide ion conductor, is even higher than that of current materials.

(Test example 6)
(Examples 10-15: Synthesis of Ba ₂ B _1-y M _1-z O _5-w )
using the following means:
_{Example 10 : Ba2ScAl0.9Ga0.1O5
Example 11 : Ba2ScAl0.95Ga0.05O5
Example 12 : Ba2Sc0.95Ga0.05AlO5
Example 13 : Ba2Sc0.95Ca0.05AlO4.975
Example 14 : Ba2Sc0.95Mg0.05AlO4.975
Example 15 : Ba2Sc0.95Zr0.05AlO5.025}
Each compound of was prepared by the solid phase reaction method. BaCO ₃ , Sc ₂ O ₃ , Al ₂ O ₃ , Ga ₂ O ₃ , CaCO ₃ , MgCO ₃ and ZrO ₂ were used as starting materials. Weighed with an electronic balance so that the molar ratio of cations was the target chemical composition of the compound of each example described above, and the other was Example 2 (synthesis of Ba ₂ Sc _0.83 Al _1.17 O ₅ ) and A similar synthesis was performed. Examples 10-11 have one type of M (Ga), and Examples 12-15 have multiple types of M (Ga, Ca, Mg, Zr, and Al).

The production phases of the obtained compounds of Examples 10 to 15 were evaluated by X-ray diffraction (XRD). Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above.
42 to 47 show the results of this XRD measurement. Each was in space group P6 ₃ /mmc. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

(Test Example 7)
(Examples 16-22: Synthesis of _{Ba2Lu1 - xAl1 +xO5} )
A compound of Ba ₂ Lu _1-x Al _1+x O ₅ was prepared by a solid state reaction method using the following means. In addition to x = 0 (same composition as in Example 4), 0.02 (Example 16), 0.04 (Example 17), 0.05 (Example 18), 0.06 (Example 19), 0.07 (Example 20), 0.1 (Example 21) and 0.2 (Example 22) were synthesized. BaCO ₃ , Lu ₂ O ₃ and Al ₂ O ₃ were used as starting materials. The molar ratio of cations was weighed with an electronic balance so that the target chemical composition of the compound of each example described above was obtained, and otherwise the same synthesis as in Example 4 (Ba ₂ LuAlO ₅ ) was performed.

The production phase of each compound of Examples 4 and 16 to 22 obtained was evaluated by X-ray diffraction (XRD). Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above. The results of this XRD measurement are shown in FIG. Each was in space group P6 ₃ /mmc. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

(Electrical conductivity of Ba ₂ Lu _1−x Al _1+x O ₅ )
The temperature dependence of the total electrical conductivity of the obtained compounds of Examples 16 to 20 and 22 was examined. The total electrical conductivity was measured by the DC 4-probe method, the measurement range was 300 to 800 ° C. (Examples 16 to 20), 300 to 1000 ° C. (Example 22), the temperature dependence of the total electrical conductivity and P (O ₂ ) dependence (relative density ~ 78%) σ _wet : in wet nitrogen (P(H ₂ O) = 0.021 atm) σ _dry : in dry nitrogen (P(H ₂ O) < 10 ^-5 atm) and did.
The results are shown in Figures 49-54. The figure is an Arrhenius plot. From the results in the figure, the conductivity in the wet atmosphere was higher than that in the dry atmosphere, suggesting proton conduction.

(Test Example 8)
₍ Transfer number evaluation of _Ba2LuAlO5 )
The proton transference number of the compound _Ba2LuAlO5 of Example ₄ synthesized above was evaluated. The proton conductivity was estimated by the difference in total electrical conductivity of Ba ₂ LuAlO ₅ in wet nitrogen and dry nitrogen, and that value was used for calculations.
The results are shown in FIG. Ba ₂ LuAlO ₅ has a high proton transference number in the range of about 300 to 800° C., and protons are the main carrier. Especially at 200 to 500°C, almost no decrease in proton transference number was observed even when the temperature was increased.

₍ Conductivity of _Ba2LuAlO5 )
Regarding the compound Ba ₂ LuAlO ₅ of Example 4 synthesized above, the temperature dependence of bulk conductivity and grain boundary conductivity was investigated. Bulk conductivity (σ _bulk ) and grain boundary conductivity (σ _gb ) were measured by an AC impedance method, and the measurement range was 100 to 800° C. σ _wet : in wet nitrogen + hydrogen (P(H ₂ O)=0. 021 atm), σ _dry : in dry nitrogen (P(H ₂ O)<10 ⁻⁵ atm).
FIG. 56 shows the results in wet nitrogen+hydrogen, and FIG. 57 shows the results in dry nitrogen. The figure is an Arrhenius plot. From the results in the figure, it was found that the bulk conductivity is higher than the grain boundary conductivity.
FIG. 58 shows a graph (Arrhenius plot) comparing the bulk proton conductivity of Ba ₂ LuAlO ₅ of Example 4 with that of a conventionally known proton conductor. The compound of Example 4 exhibits conductivity superior to that of conventionally known proton conductor compounds in most temperature ranges, and even exceeds BaZr _0.8 Y _0.2 O _2.9 at temperatures below 500°C. rice field.

₍ UV-visible diffuse reflectance spectrum of _Ba2LuAlO5 )
For the compound Ba ₂ LuAlO ₅ of Example 4 synthesized above, an ultraviolet/visible diffuse reflectance spectrum (UV-Vis DRS) was measured in air at room temperature by a double beam method. The bandgap was determined using Tauc Plot assuming direct allowed transitions.
The results are shown in FIG. The results in the figure suggest that the bandgap is sufficiently large and the contribution of electron and hole conduction is small.

(Test Example 9)
(Examples 23-27: Synthesis of Ba _7-x B _6-y M _2-z O _19-w )
using the following means:
_{Example 23 : Ba6.3K0.7Sc6Al2O 18.65
Example 24 : Ba6.3Sr0.7Sc6Al2O19 _
Example 25 : Ba7Sc5.4Mg0.6Al2O 18.7
Example 26 : Ba7Sc5.4Tb0.6Al2O 19.3
Example 27 : Ba7Sc5.4Zr0.6Al2O19.3 _}
Each compound of was prepared by the solid phase reaction method. BaCO ₃ , Sc ₂ O ₃ , Al ₂ O ₃ , K ₂ CO ₃ , SrCO ₃ , Ga ₂ O ₃ , CaCO ₃ , MgCO ₃ , Tb ₂ O ₃ and ZrO ₂ were used as starting materials. Weighed with an electronic balance so that the molar ratio of cations would be the target chemical composition of the compound of each example described above, and mixed and ground using a ball mill. Others were synthesized in the same manner as in Example 2 (Synthesis of Ba ₂ Sc _0.83 Al _1.17 O ₅ ). Examples 23 to 27 have multiple types of M (Sc, Mg, Tb, Zr, and Al).

The production phases of the obtained compounds of Examples 23 to 27 were evaluated by X-ray diffraction (XRD). Powder X-ray diffraction measurements were performed using the same equipment and conditions as described above.
The results of this XRD measurement are shown in Figures 60-64. Each was in space group P6 ₃ /mmc. The calculation prediction and the measurement result showed almost the same result, indicating that the expected compound was obtained.

_{( Electrical conductivity of Ba7Sc5.4Zr0.6Al2O19.3 )}
For the compound Ba ₇ Sc _5.4 Zr _0.6 Al ₂ O _19.3 of Example 27, the temperature dependence of the total electrical conductivity was investigated. The total electrical conductivity was measured by the direct current 4-probe method, the measurement range was 300 to 800 ° C., the temperature dependence of the total electrical conductivity (relative density ~ 71%), σ _wet : in moist air (P (H ₂ O) = 0.021 atm).
The results are shown in FIG. The figure is an Arrhenius plot.

(Structure optimization calculation)
Structural optimization calculations based on density functional theory were performed for each of the compounds represented by the following chemical formulas, and lattice constants obtained by structural optimization were determined.
Density functional theory calculations using generalized gradient approximation and PBE functionals were performed using the program VASP. The lattice constant results are shown in each table for each structure group and division below.
The optimized structures of all compositions retain the crystal structure of the original hexagonal perovskite-related compounds, indicating the possibility of synthesizing these compositions. These compounds are also considered to exhibit oxide ion conduction.

(Calculation examples 1 to 308: groups of Rb ₅ BiMo ₄ O ₁₆ and Rb ₅ GdMo ₄ O ₁₆ )
Category a: Structure optimization calculations based on density functional theory were performed on Rb ₅ MMo ₄ O ₁₆ . Here, M is Bi, Gd, Ce, Dy, Er, Eu, Ho, S, In, La, Lu, Nd, Pm, Pr, Sc, Sm, Tb, Tm, Y, Yb, Ag, Au, Ir , Mo, Nb, Np, Pd, Pu, Ru, Sb, Ta, Ti and U are cations of at least one element. (Table 1)
Section b: Performed on M ₅ BiMo ₄ O ₁₆ . Here, M is a cation of at least one element selected from the group consisting of Na, K, Cs, Hg, Tl, Au and Ba. (Table 2)
Section c: Performed on Rb ₅ BiM ₄ O ₁₆ . Here, M is a cation of at least one element selected from the group consisting of Cr, S, Te and W. (Table 2)
Section d: Rb ₁₅ Gd ₃ Mo ₁₂ O ₃₈ X ₁₀ was tested. Here, X is an anion of at least one element selected from the group consisting of F, N and S. (Table 2)
Section e: Rb ₁₅ Bi ₃ Mo ₁₂ O ₃₈ X ₁₀ was tested. Here, X is an anion of at least one element selected from the group consisting of F, N and S. (Table 2)
Section f: Performed on Rb ₄ MGdMo ₄ O ₁₆ . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 3 and 4)
Section g: Rb ₁₅ Gd ₂ MMo ₁₂ O ₄₈ was performed. Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 5 and 6)
Section h: _{Performed on Rb5GdMo3MO16} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 7 and 8)
Section i: _{Performed on Rb4MBiMo4O16} . Here, M is a cation of at least one element selected from the group consisting of Ru, Cd, Br, Sc, Be, Bi, Sm, Si, Se, Sc, B, Sb and S. (Table 9)
Section j: Performed on Rb ₁₅ Bi ₂ MMo ₁₂ O ₄₈ . Here, M is selected from the group consisting of Ag, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Al, Ge, Hf, Hg, Ho, I, In, Ir, Li and Lu. are cations of at least one element with (Table 9)
Section k: _{Performed on Rb5BiMo3MO16} . Here, M is selected from the group consisting of Ag, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Al, Ge, Hf, Hg, Ho, I, In, Ir, Li and Lu. are cations of at least one element with (Table 10)
_{Category l : Structural optimization calculations for Rb5GdMo4O13 , Rb15Gd3Mo12O56 , Rb5Mo4BiO13 , Rb15Mo12Bi3O56 , Rb5GdMo3O16 , Rb15Gd 2Mo12O48 , Rb4GdMo4O16 , Rb5Mo3BiO16 , Rb15Mo12Bi2O48 , Rb4Mo4BiO16 . _ _ _ _ _ _} In addition, the division l assumes the deficiency of each cation/anion. (Table 10)

(Calculation examples 309 to 561: group of α-Ba ₂ ScAlO ₅ )
Section a: Performed on Ba ₂ MAIO ₅ . Here, M is Sc, Ag, Bi, Ga, Sb, Au, Ce, Co, Cr, Dy, Er, Eu, Fe, Gd, Ho, In, Ir, La, Lu, Mn, Mo, Nb, Nd, at least one element selected from the group consisting of Ni, Np, Pa, Pd, Pm, Pr, Pu, Rh, Ru, Sm, Ta, Tb, Ti, Tl, Tm, U, V, Y, and Yb It is a cation. (Table 11)
Section b was performed on M ₂ ScAlO ₅ . Here, M is a cation of at least one element selected from the group consisting of C, Ra, Pb, Cd and Sr. (Table 12)
Section c Ba ₂ ScGaO ₅ was performed. (Table 12)
Section d was performed on Ba ₂ ScAlX ₅ . Here, X is an anion of at least one element selected from the group consisting of N, F and S. (Table 12)
Section _e was _{performed on Ba6Sc2Al2MO15} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 13 and 14)
Section f Ba ₄ M ₂ Sc ₃ Al ₃ O ₁₅ was performed. Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Table 14, Table 15)
Section _g : _{Performed on Ba6Sc2MAl3O15} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 16 and 17)

(Calculation examples 562-813: group of β-Ba ₂ ScAlO ₅ )
Section a: Performed on Ba ₂ MAIO ₅ . Here, M is Sc, Ag, Au, Bi, Ce, Co, Cr, Dy, Er, Eu, Fe, Ga, Gd, Ho, In, Ir, La, Lu, Mn, Mo, Nb, Nd, Ni, A cation of at least one element selected from the group consisting of Np, Pa, Pd, Pm, Pr, Pu, Rh, Sb, Sm, Ta, Tb, Ti, Tl, Tm, U, V, Y, and Yb is. (Table 18)
Section b: Performed on M ₂ ScAlO ₅ . Here, M is a cation of at least one element selected from the group consisting of Eu, Pb and Sr. (Table 19)
Section c: Performed on Ba ₂ ScGaO ₅ . (Table 19)
Section d: Performed on Ba ₂ ScAlX ₅ . Here, X is an anion of at least one element selected from the group consisting of N, F and S. (Table 19)
Section _e : _{Performed on Ba8Sc4Al3MO20} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 20 and 21)
Section f: Performed on Ba ₃ MSc ₂ Al ₂ O ₁₀ . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 22 and 23)
Section _g : _{Performed on Ba8Sc3MAl4O20} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 23, 24, 25)

(Calculation examples 814 to 1047: group of Ba ₇ Sc ₆ Al ₂ O ₁₉ )
_Section a: _{Performed on Ba7M6Al2O19} . Here, M is Ni, As, Co, Cr, Ga, V, Mn, Fe, Rh, Ti, Ru, Ir, Mo, Nb, Ta, Ag, Sc, Pd, Sb, In, Au, Lu, Yb, It is a cation of at least one element selected from the group consisting of Tm, Tl, Er and Y. (Table 26)
Section b: Performed on M ₇ Sc ₆ Al ₂ O ₁₉ . Here, M is a cation of at least one element selected from the group consisting of Cd, Ca, Sr, Pb and Ra. (Table 27)
Section c Ba ₇ Sc ₆ Ga ₂ O ₁₉ was performed. (Table 27)
Section _d : _{Performed on Ba7Sc6Al2X19} . where X is N or F; (Table 27)
Section e: Performed on Ba ₇ Sc ₆ AlMO ₁₉ . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 28 and 29)
Section f: Ba ₁₁ M ₃ Sc ₁₂ Al ₄ O ₃₈ was tested. Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Table 31)
_{Section g} : _{Performed on Ba14Sc9M3Al4O38} . Here, M is Ag, Al, At, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, Li, Lu, Mg, Mn, Mo, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Pm, Po, Pr, Pt, Pu, Re, Rh, Ru, S, selected from the group consisting of Sb, Sc, Se, Si, Sm, Sn, Ta, Ta, Tb, Tc, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Yb, Zn, Zr It is a cation of at least one element. (Tables 32 and 33)

According to the solid electrolyte, the electrolyte layer using the same, the battery, and the method for producing the solid electrolyte of the present invention, a solid electrolyte having high ionic conductivity and stable ionic conductivity even under ambient temperature or gas conditions; An electrolyte layer, a battery, and a method for producing a solid electrolyte are obtained. The solid electrolyte of the present invention can also be used for fuel cells, sensors, electrodes, electrolytes, element concentrators, element separation membranes, element permeable membranes, element pumps, catalysts, photocatalysts, electrical/electronic/communication equipment, energy/environment-related equipment or It can be used for optical equipment and the like.

Claims (28)

A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a compound represented by the following general formula (1).
A _5-x B _1-y M _4-z X _16-w (1)
[In the formula (1), A is a cation, and the missing amount x of A is a numerical value of -4 to 4. B is a cation, and the defect amount y of B is a numerical value of -0.5 to 0.5. M is a cation, and the missing amount z of M is a numerical value of -2 to 2. X is an anion and w is the amount of deficiency of the anion X, which is a numerical value of -3 to 3. ] In the above formula (1), the average ionic radius of A is 1.10 to 1.83 Å, the average ionic radius of B is 0.73 to 1.24 Å, the average ionic radius of M is 0.20 to 0.50 Å, X The solid electrolyte according to claim 1, wherein the average ionic radius of is 1.10 Å to 1.68 Å. 3. The solid electrolyte according to claim 1, wherein in the formula (1), the anion X is O, and the w is the amount of oxygen deficiency. The solid electrolyte according to any one of claims 1 to 3, wherein the compound is a palmierite-type compound and is an electric conductor that conducts ions or electrons other than Ba ²⁺ and K ^{2 +} . 5. The solid electrolyte according to any one of claims 1 to 4, wherein said compound is a rubidium ion conductor, an oxide ion conductor, a proton conductor, an electron conductor, or a mixed conductor thereof. A of the compound is a cation containing at least Rb, B is a cation containing at least one element selected from among Gd, La, Nd, Sm, Eu, Tb, and Bi, and M contains at least Mo. 6. The solid electrolyte according to any one of claims 1 to 5, wherein the solid electrolyte is a cation and X is an anion containing at least O. The compounds are _Rb5Gd (MoO4) ₄ , _Rb5La (MoO4) ₄ , _Rb5Nd ( _MoO4 ) ₄ , _{Rb5Sm ( MoO4} ) ₄ , _{Rb5Eu ( MoO4} ) ₄ , _Rb5 Tb( _MoO4 ) ₄ , _{Rb5Bi ( MoO4} ) _{4 , Rb5Pr ( MoO4} ) ₄ , _{Rb4.9Bi1.1Mo4O16.1 ,} or _{Rb4.5Ba0.5GdMo} 7. The solid electrolyte according to any one of claims 1 to ₆ , which is _{4O 16.25} . 8. The solid electrolyte according to any one of claims 1 to ₇ , wherein said compound is _Rb5Gd (MoO4) ₄ . A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a compound represented by the following general formula (2).
A _2-x B _1-y M _1-z X _5-w (2)
[In the formula (2), A is a cation, and the defect amount x of A is a numerical value of -1 to 1. B is a cation, and the defect amount y of B is a numerical value of -0.5 to 0.5. M is a cation, and the missing amount z of M is a numerical value from -0.5 to 0.5. X is an anion, and w is the amount of deficiency of the anion X, which is a numerical value from -1 to 1. ] In the above formula (2), the average ionic radius of A is 1.28 Å to 1.94 Å, the average ionic radius of B is 0.59 Å to 1.04 Å, and the average ionic radius of M is 0.31 Å to 0.47 Å. , X has an average ionic radius of 1.10 Å to 1.68 Å. The solid according to claim 9 or 10, wherein said compound is an α-Ba ₂ ScAlO ₅ type or β-Ba ₂ ScAlO ₅ type compound and is an electrical conductor or a mixed ion-electron conductor conducting ions or electrons. Electrolytes. 12. The solid electrolyte according to any one of claims 9 to 11, wherein in the formula (2), the anion X is O, and the w is the amount of oxygen deficiency. In the formula (2), A is a cation containing at least Ba, B is a cation containing at least Sc, Lu or In, M is a cation containing at least Al, and X is an anion containing at least O. A solid electrolyte according to any one of claims 9 to 12. _{10. The compound} is _{Ba2InAlO5 , Ba2ScAlO5 , Ba2Sc0.87Al1.13O5 , Ba2LuAlO5 , or Ba2Lu0.9Al1.1O5 .} 14. The solid electrolyte according to any one of 13. _{The compounds are Ba2ScAlO5 , Ba2Sc0.87Al1.13O5 , Ba2LuAlO5 , Ba2ScAl0.9Ga0.1O5 , Ba2ScAl0.95Ga0.05O _ _ _ 5 , Ba2Sc0.95Ga0.05AlO5 , Ba2Sc0.95Ca0.05AlO4.976 , Ba2Sc0.95Mg0.05AlO4.975 , Ba2Sc0 . _ _ _ _ _ 95Zr0.05AlO5.025 , Ba2Lu0.98Al1.02O5 , Ba2Lu0.96Al1.04O5 , Ba2Lu0.95Al1.05O5 , Ba _ _ _ _ _ _ 2Lu0.94Al1.06O5 , Ba2Lu0.93Al1.07O5 , Ba2Lu0.9Al1.1O5 , or Ba2Lu0.8Al1.2O _ _ _ _ _ _ _} 15. The solid electrolyte according to any one of claims 9 to 14, which is ₅ . A solid electrolyte containing a hexagonal perovskite-related compound, wherein the compound is a Ba ₇ Sc ₆ Al ₂ O ₁₉ type compound represented by the following general formula (3).
A _7-x B _6-y M _2-z X _19-w (3)
[In the formula (3), A is a cation, and the missing amount x of A is a numerical value of -3.5 to 3.5. B is a cation, and the defect amount y of B is a numerical value of -3 to 3. M is a cation, and the missing amount z of M is a numerical value from -1 to 1. X is an anion, and w is the missing amount of the anion X, which is a value of -3 to 3. ] In the above formula (3), the average ionic radius of A is 1.28 to 1.94 Å, the average ionic radius of B is 0.59 to 0.90 Å, and the average ionic radius of M is 0.31 to 0.47 Å. , X has an average ionic radius of 1.10 Å to 1.68 Å. 18. The solid electrolyte according to claim 16 or 17, wherein said anion X is O in said formula (3). In the formula (3), A is a cation containing at least Ba, B is a cation containing at least Sc, M is a cation containing at least Al, and X is an anion containing at least O. Item 19. The solid electrolyte according to any one of Items 16 to 18. _{Said compounds are Ba7Sc6Al2O19 , Ba6.3K0.7Sc6Al2O18.65 , Ba6.3Sr0.7Sc6Al2O19 , Ba7Sc5.4 _ _ _ _ _ _ Mg0.6Al2O19.3 , Ba7Sc5.4Tb0.6Al2O19.3 , or Ba7Sc5.4Zr0.6Al2O19.3 _ _ _ _ _ _ _} 20. The solid electrolyte according to any one of 16 to 19. The solid electrolyte according to any one of claims 1 to 20, which is used as a proton conductor and is for use under temperature conditions of 200 to 1200°C. 22. The solid electrolyte according to any one of claims 1 to 21, wherein the electrical conductivity represented by log [σ(Scm ^-1 )] is -7 or more when measured at 200°C. Fuel cells, sensors, electrodes, electrolytes, element concentrators, element separation membranes, element permeation membranes, element pumps, catalysts, photocatalysts, electric/electronic/communication equipment, energy/environment-related equipment, or optical equipment. 23. The solid electrolyte according to any one of 22. 24. The solid electrolyte according to claim 23, for electrolyte layers used in fuel cells or sensors. An electrolyte layer comprising the solid electrolyte according to any one of claims 1 to 24. A battery comprising the electrolyte layer of claim 25. 27. The cell of claim 26, which is a hydrogen fuel cell. A method for producing a solid electrolyte according to any one of claims 1 to 24,
Producing the compound by a solid state reaction method,
Firing in the solid phase reaction method is
When the compound is a compound represented by the general formula (1), it is calcined in the atmosphere at 200 to 1000° C. for 5 to 20 hours and then at 300 to 1100° C. for 5 to 24 hours,
When the compound is a compound represented by general formula (2) or (3), it is calcined at 200 to 1000° C. for 5 to 20 hours in the air and then at 1500 to 1700° C. for 3 to 24 hours in the air. A method for producing a solid electrolyte.

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