SOLID ELECTROLYTE, ELECTROLYTE LAYER AND BATTERY

Description

[Technical Field]

[0001] The present invention relates to a solid electrolyte used for a solid electrolyte layer such as a fuel cell, an electrolyte layer using the same, and a battery.[Background Art]

[0002] Among fuel cells that have been studied in recent years, a solid oxide fuel cell (hereinafter, referred to as "SOFC") has particularly high power generation efficiency, does not require a fuel-reforming device, and has excellent long-term stability, and therefore, the SOFC has a possibility of being widely applied to home use and business use, and is attracting attention.

[0003] The SOFC is configured to include a solid electrolyte-electrode laminate provided with fuel and air electrodes on both sides of the solid electrolyte layer. Yttria-stabilized zirconia (ZrO 2 -Y 2 O 3) (hereinafter, referred to as "YSZ") is known as an oxide ion (O 2-< ) conductive ceramic for the solid electrolyte layer used in SOFC.

[0004] Other examples of solid electrolytes used in SOFC include compounds with high electrical conductivity, for example, compounds with high ion conductivity that conduct ions such as oxide ions (O 2-< ) and protons (H +< ). Patent Document 1 discloses a crystalline inorganic compound capable of conducting at least one carrier selected from the group consisting of anions, cations, protons, electrons, and holes. Non-Patent Document 1 discloses Ba 7 Nb 4 MoO 20 , which is a hexagonal perovskite-related compound having high ion conductivity (σ). Non-Patent Documents 2-6 and the patent documents referenced therein describe hexagonal perovskite-related compounds.[Citation List][Patent Document][Patent Document 1]

[0005] Japanese Patent No. 6448020[Non-Patent Documents]

[0006] [Non-Patent Document 1] Sacha Fop, Novel oxide ion conductors in the hexagonal perovskite family, uk. Bl. Ethos. 701786, [viewed December 25, 2018], Internet < URL: https: / / ethos.bl.uk / OrderDetails.do?uin=uk.bl.ethos.701786 > [Non-Patent Document 2] DATABASE WPIWeek 201054 Thomson Scientific, London, GB;AN 2010-J83646-& JP 2010 170998 A (MITSUBISHI JUKOGYO KK) 5 August 2010 (2010-08-05) [Non-Patent Document 3] MOSSNER B ET AL: "9R-Stapelvarianten vom Typ Ba3(B,B')2O9-y mit B,B' = Mo, W, V, Ti", JOURNAL OF THE LESS-COMMON METALS, ELSEVIER-SEQUOIA S.A. LAUSANNE, CH, vol. 114, no. 2, 16 December 1985 (1985-12-16), pages 333-341, XP024073350,ISSN: 0022-5088, DOI: 10.1016 / 0022-5088(85)90453-9 [retrieved on 1985-12-16] [Non-Patent Document 4] DATABASE WPIWeek 201379 Thomson Scientific, London, GB;AN 2013-W00868-& CN 103 316 668 A (UNIV GUILIN TECHNOLOGY) 25 September 2013 (2013-09-25) [Non-Patent Document 5] FLOROS N. ET AL: "The n=2 Member of the New Layered Structural Family Ba5+nCa2Mn3+nO3n+14 Derived from the Hexagonal Perovskite: Ba7Ca2Mn5O20",JOURNAL OF SOLID STATE CHEMISTRY, vol. 168, no. 1, 1 October 2002 (2002-10-01), pages 11-17, XP93044275,US ISSN: 0022-4596, DOI: 10.1006 / jssc.2002.9667 [Non-Patent Document 6] GAUDIN E ET AL: "Synthesis, crystal structure, and magnetic properties of the manganate La2Ca2MnO6(O2) related to the hexagonal perovskite-type structure", JOURNAL OF SOLID STATE CHEMISTRY, vol. 175, no. 1, 1 October 2003 (2003-10-01), pages 124-131, XP93044352,US ISSN: 0022-4596, DOI: 10.1016 / S0022-4596(03)00043-4 [Summary of Invention][Technical Problem]

[0007] A conventional SOFC using YSZ as a solid electrolyte needs to be operated at a high temperature in order to obtain sufficient performance. The reason for this is that YSZ requires a high temperature of approximately 700°C or more in order to ensure the oxide ion conductivity necessary for the battery. Operating a battery at a high temperature of 700°C or more requires an environment and space in which the battery can be operated, other devices for keeping the battery at a high temperature and shutting off or cooling the battery so that other environments do not have a high temperature, and the like.

[0008] It is expected that if SOFC can be operated at low temperatures, the restriction for operating at a high temperature described above will be reduced, and the usefulness of SOFC will be significantly increased. It is also expected that the range of application of solid electrolytes other than SOFC will be greatly expanded because they can be operated at a low temperature. Therefore, a solid electrolyte having high electrical conductivity at a low temperature is strongly desired.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid electrolyte having high electrical conductivity even in a low-temperature region, and an electrolyte layer and a battery using the solid electrolyte.[Solution to Problem]

[0010] In order to solve the above problems, the present invention has the following aspects. [1] A solid electrolyte comprising a hexagonal perovskite-related compound, wherein the compound is a compound represented by any of the following general formulas (3) to (7), (11) and (13):         Ba7Nb(4-x)Mo(1+x)O(20+z)     (3) , [in the formula (3), x represents a value of -1.1 or more and -0.01 or less or 0.01 or more and 1.1 or less, and z is an oxygen non-stoichiometry and represents a value of - 2.0 or more and 2.0 or less];         Ba7Nb(4-y)MoMyO(20+z)     (4) , [in the formula (4), M is a cation of at least one element selected from the group consisting of V, Mn, Ge, Si, and Zr; and y represents a value of 0.01 or more and 1.1 or less, and z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less];         Ba7Nb4Mo(1-y)MyO(20+z)     (5) , [in the formula (5), M is a cation of at least one element selected from the group consisting of V and Mn; and z is an oxygen non-stoichiometry and represents a value of - 2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba7Nb(4-y)MoCryO(20+z)     (6) , [in the formula (6), z is an oxygen non-stoichiometry and represents a value of - 2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba7Nb(4-y)MoWyO(20+z)     (7) , [in the formula (7), z is an oxygen non-stoichiometry and represents a value of - 2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba2.6Ca2.4La4Mn4O(19+z)     (11) , [in the formula (11), z is an oxygen non-stoichiometry and represents a value of -1.0 or more and 1.0 or less]; and         Ba5M2Al2ZrO(13+z)     (13) , [in the formula (13), M represents any of Gd, Dy, Ho, Er, Tm, Yb, or Lu; and z is an oxygen non-stoichiometry and represents a value of -1.0 or more and 1.0 or less] , and wherein the hexagonal perovskite-related compound in the present embodiment is a compound having a layered structure containing a hexagonal perovskite unit. [2] The solid electrolyte according to [1], wherein the compound is a compound represented by the general formula (3), and x is 0.06 or more and 0.30 or less. [3] The solid electrolyte according to [2], wherein x is 0.19 or more and 0.21 or less. [4] The solid electrolyte according to [3], wherein in the compound, an a-axis length, a b-axis length, a c-axis length (Å), an α-angle, a β-angle, and a γ-angle (o) of a lattice constant are in the numerical range of 5.35 < a < 6.56, 5.35 < b < 6.56, 15.14 < c < 18.52, 89 < α < 91, 89 < β < 91, and 119 < γ < 121, for the formulas (3) to (7), 5.23 < a < 6.4, 5.23 < b < 6.4, 18.96 < c < 23.19, 89< α < 91, 89 < β < 91, and 119 < γ < 121, for for the formula (11), 5.05 < a < 6.19, 5.05 < b < 6.19, 15.57 < c < 19.03, 89 < α < 91, 89 < β < 91, and 119 < γ < 121, for the formula (13), respectively. [5] A use of the solid electrolyte according to any one of [1] to [4], used as an oxide ion (O2-) conductor and used under a temperature condition of 300 to 1200°C. [6] The solid electrolyte according to any one of [1] to [4], wherein the solid electrolyte has an electrical conductivity represented by log [σ(Scm-1)] of -7 or more when measured at 300°C. [7] A use of the solid electrolyte according to any one of [1] to [4] or 6, or the use according to [5], used for a solid oxide fuel cell (SOFC), a sensor, a battery, an electrode, an electrolyte, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, an oxygen pump, a catalyst, a photocatalyst, an electric / electronic / communication device, an energy / environment-related device, or an optical device. [8] A use of the solid electrolyte according to any one of [1] to [4] or [6], or the use according to [5] or [7],used for an electrolyte layer used in a solid oxide fuel cell (SOFC), a sensor, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, or an oxygen pump. [9] An electrolyte layer comprising the solid electrolyte according to any one of [1] to [8].

[10] A battery comprising the electrolyte layer containing the solid electrolyte according to [9].

[11] The battery according to

[10] , wherein the battery is a solid oxide fuel cell (SOFC). [Advantageous Effects of Invention]

[0011] According to the present invention, a solid electrolyte having high electrical conductivity even in a low-temperature region, and an electrolyte layer and a battery using the solid electrolyte can be obtained.[Brief Description of Drawings]

[0012] Fig. 1 is a graph showing an X-ray diffraction (XRD) pattern of Test Example 1 of the present example. Fig. 2 is a graph showing the XRD pattern of Test Example 2 of the present example. Fig. 3 is a graph showing the XRD pattern of Test Example 3 of the present example. Fig. 4 is a graph showing the XRD pattern of Test Example 4 of the present example. Fig. 5 is a graph showing the XRD pattern of Test Example 5 of the present example. Fig. 6 is a graph showing the XRD pattern of Test Example 6 of the present example. Fig. 7 is a graph showing the XRD pattern of Test Example 7 of the present example. Fig. 8 is a graph showing the XRD pattern of Test Example 8 of the present example. Fig. 9 is a graph showing the XRD pattern of Test Example 9 of the present example. Fig. 10 is a graph showing the XRD pattern of Test Example 10 of the present example. Fig. 11 is a graph showing the XRD pattern of Test Example 11 of the present example. Fig. 12 is a graph showing the XRD pattern of Test Example 12 of the present example. Fig. 13 is a graph showing the XRD pattern of Test Example 13 of the present example. Fig. 14 is a graph showing the XRD pattern of Test Example 14 of the present example. Fig. 15 is a graph showing the XRD pattern of Test Example 15 of the present example. Fig. 16 is a graph showing the XRD pattern of Test Example 16 of the present example. Fig. 17 is a graph showing the XRD pattern of Test Example 17 of the present example. Fig. 18 is a graph showing the XRD pattern of Test Example 18 of the present example. Fig. 19 is a graph showing the XRD pattern of Test Example 19 of the present example. Fig. 20 is a graph showing the XRD pattern of Test Example 20 of the present example. Fig. 21 is a graph showing the XRD pattern of Test Example 21 of the present example. Fig. 22 is a graph showing a comparison of the electrical conductivity of Test Example 1 and Test Example 6 of the present example and YSZ. Fig. 23 is a graph showing the electrical conductivity of Ba 7 Nb (4-x) Mo (1+x) O (20+z) in which the excess amount x of Mo in Test Examples of the present example is 0.02 to 0.10. For comparison, this graph also shows the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the excess amount x of Mo of Test Examples of the present example is 0.0. Fig. 24 is a graph showing the electrical conductivity of Ba 7 Nb (4-x) Mo (1+x) O (20+z) in which the excess amount x of Mo in Test Examples of the present example is 0.10 to 0.18. For comparison, this graph also shows the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the excess amount x of Mo of Test Examples of the present example is 0.0. Fig. 25 is a graph showing electrical conductivity of Ba 7 Nb (4-y) MoM y O (20+z) in which the doping amount y of cations of each element of Cr, W, V, Si, Ge, and Zr is 0.1 and Ba 7 Nb 4 Mo (1-y) V y O (20+z) in which the doping amount y of cations of V is 0.1 in Test Examples of the present example. Fig. 26 is a graph showing the electrical conductivity of Ba 7 Nb (4-y) MoCr y O (20+z) in which the doping amount y of Cr of Test examples of the present example is 0.10 to 0.30. Fig. 27 is a graph showing the oxygen partial pressure dependence of electrical conductivity at 900°C in Test Example 1 of the present example. Fig. 28 is a graph showing the relationship between the electromotive force and the oxygen partial pressure of the oxygen concentration cell at 800°C in Test Example 6 of the present example. Fig. 29 is a graph showing the relationship between the electromotive force and the oxygen partial pressure of the oxygen concentration cell at 900°C in Test Example 6 of the present example. Fig. 30 shows the crystal structure of Ba 7 Nb 4 MoO 20 which is Test Example 22. Fig. 31 is a graph showing the XRD patterns of Ba 7 Nb (4-x) Mo (1+x) O (20+z) of Test Examples 22 to 27. Fig. 32 shows XRD measurement charts of Ba 7 Nb (4-x) Mo (1+x) O (20+z) for Test Examples 28 to 37 with different compositions. Fig. 33(a) shows the conductivity of Ba 7 M (4-x) Mo (1+x) O (20+z) of Test Examples 22 to 27 in a temperature-dependent manner. Fig. 33(b) shows the conductivity of Ba 7 Nb (4-x) Mo (1+x) O (20+z) for Test Examples 28 to 35 having different compositions in a temperature-dependent manner. Fig. 34 shows the conductivity of Ba 7 Nb (4-x) Mo (1+x) O (20+z) of Test Examples 22 to 35 at a certain temperature in a composition-dependent manner. Fig. 35 is a graph showing the XRD patterns of Ba 7 Nb (4-y) MoCr y O (20+z) of Test Examples 40 to 44 and 46. Fig. 36 shows the conductivity of Ba 7 Nb (4-y) MoCr y O (20+z) of Test Examples 40 to 44 and 46 in a temperature-dependent manner. Fig. 37 shows the conductivity of Ba 7 Nb (4-y) MoCr y O (20+z) of Test Examples 22, 40 to 44, and 46 in a composition-dependent manner. Fig. 38 is a graph showing the XRD patterns of Ba 7 Nb (4-y) MoW y O (20+z) of Test Examples 52 to 58 and 81 and 83. Fig. 39 shows the total electrical conductivity of Test Examples 52 to 58, 81, 82 of Ba 7 Nb (4-y) MoW y O (20+z) in a temperature-dependent manner. Fig. 40 shows the total electrical conductivity of Ba 7 Nb (4-y) MoW y O (20+z) of Test Examples 22, 52 to58, 81, and 82 in a composition-dependent manner. Fig. 41 is a graph showing the XRD patterns of Test Examples 38, 39, 45, 47 to 51. Fig. 42 shows the electrical conductivity of Test Examples 38, 39, and 47 to 50 in a temperature-dependent manner. Fig. 43 shows the crystal structure of a Ba 3 WVO 8.5 -based material of Test Examples 59 to 67. Fig. 44 is a graph showing the XRD patterns of Ba 3 W (1-x) V (1+x) O (8.5+z) of Test Examples 59 to 67. Fig. 45 shows the electrical conductivity of Ba 3 W (1-x) V (1+x) O (8.5+z) of Test Examples 59 to 67 in a temperature-dependent manner. Fig. 46 shows the electrical conductivity of Ba 3 W (1-x) V (1+x) O (8.5+z) of Test Examples 59 to 67 in a composition-dependent manner. Fig. 47 shows the oxygen partial pressure P (O 2 ) dependence of total electrical conductivity for Ba 3 W 1.6 V 0.4 O 8.8 of Test Example 66. Fig. 48 shows the conductivity of Ba 3 W 1.6 V 0.4 O 8.8 of Test Example 66 in dry air and in moist air in a temperature-dependent manner. Fig. 49 shows the crystal structure of Ba 3 MoTIO 8 of Test Example 68. Ba 3 Mo (1-x) Ti (1+x) O (8+z) of Test Examples 69 and 70 also have a similar crystal structure. Fig. 50 is a graph showing the XRD patterns of Ba 3 Mo (1-x) Ti (1+x) O (8+z) of Test Examples 68 to 70. Fig. 51 shows the electrical conductivity of Ba 3 Mo (1-x) Ti (1+x) O (8+z) of Test Examples 68 to 70 in a temperature-dependent manner. Fig. 52 shows the P (O 2 ) dependence of total electrical conductivity for Ba 3 M0 1.1 Ti 0.9 O 8.1 of Test Example 69. Fig. 53 shows the crystal structure of Ba 7 Ca 2 Mn 5 O 20 of Test Example 71. Fig. 54 is a graph showing the XRD pattern of Ba 7 Ca 2 Mn 5 O 20 of Test Example 71. Fig. 55 shows the total electrical conductivity of Ba 7 Ca 2 Mn 5 O 20 of Test Example 71 in a temperature-dependent manner. Fig. 56 shows the crystal structure of Ba 2.6 Ca 2.4 La 4 Mn 4 O 19 of Test Example 72. Fig. 57 is a graph showing the XRD pattern of Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 of Test Example 72. Fig. 58 shows the total electrical conductivity of Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 of Test Example 72 in a temperature-dependent manner. Fig. 59 shows the crystal structure of La 2 Ca 2 MnO 7 of Test Example 73. Fig. 60 is a graph showing the XRD pattern of La 2 Ca 2 MnO 7 of Test Example 73. Fig. 61 shows the crystal structure of a Ba 5 M 2 Al 2 ZrO 13 -based material of Test Examples 74 to 80. Fig. 62 is a graph showing the XRD patterns of Ba 5 M 2 Al 2 ZrO 13 of Test Examples 74 to 80. Fig. 63 shows the total electrical conductivity of Ba 5 M 2 Al 2 ZrO 13 of Test Examples 74 to 80 in a temperature-dependent manner. [Description of Embodiments]

[0013] Hereinafter, a solid electrolyte, an electrolyte layer, and a battery will be described.(Solid electrolyte)

[0014] A solid electrolyte of the present embodiment contains a hexagonal perovskite-related compound that includes a compound represented by a specific general formula described later. Here, the solid electrolyte is a material through which ions are conducted, and also includes a material through which both ions and (protons, electrons or holes thereof) are conducted. The hexagonal perovskite-related compound in the present embodiment is a compound having a layered structure containing a hexagonal perovskite unit or a compound having a similar structure.

[0015] The embodiments are defined by aspects [1] to

[11] described above.

[0016] In the present embodiment, it is assumed that a compound having each of the above-described conditions provides effective electrical conductivity (oxide ion conductivity) when used as an oxide ion (O 2-< ) conductor or a solid electrolyte. Oxide ion (O 2-< ) conductors are compounds in which electricity is conducted by conduction (movement) of oxide ions. Further, the solid electrolyte using the compound of the present embodiment is preferably used under a temperature condition of 300 to 1200°C, more preferably used under a temperature condition of 300 to 1000°C, still more preferably used at 300°C or more and less than 700°C, and particularly preferably used at 300 to 600°C. By using the solid electrolyte under these temperature conditions, it is possible to operate at a lower temperature than the conventional SOFC, so that there are few restrictions on the equipment and arrangement required for the operation, and a wide range of applications can be obtained.

[0017] The solid electrolyte using the compound of the present embodiment can be operated at a temperature exceeding 600°C as in a conventional SOFC.

[0018] When the electrical conductivity of the solid electrolyte of the present embodiment is measured at about 300°C, the electrical conductivity represented by log [σ(Scm -1< )] is preferably -7 or more, more preferably higher than -5.0, and particularly preferably -3.5 or more. Since the electrical conductivity at 300°C is sufficiently high, the electrical conductivity is high at a low temperature, and it can be particularly preferably used for a battery or other device operating at a low temperature.(Solid electrolyte layer)

[0019] Further, the solid electrolyte of the present embodiment can be used as a solid electrolyte layer by being formed in a layer shape or being formed so as to be included in a layered structure. The solid electrolyte layer may conductor another ion conductor or the like in addition to the solid electrolyte of the present embodiment. In order for a battery or the like using the solid electrolyte of the present embodiment to exhibit effective electrical conductivity and to effectively operate as a low-temperature operating battery described later in particular, it is preferable for the solid electrolyte layer to contain, for example, 50% by mass or more, preferably 70% by mass or more, of the solid electrolyte containing the hexagonal perovskite-related compound of the present embodiment.(Battery containing solid electrolyte or solid electrolyte layer)

[0020] The solid electrolyte of the present embodiment, or the electrolyte layer containing the solid electrolyte, can be used for a battery containing the solid electrolyte. Of these, the solid electrolyte of the present embodiment can be particularly preferably used for a solid oxide fuel cell (SOFC) as described above.

[0021] The SOFC in the present embodiment means a battery in which all the electrodes and electrolytes constituting the battery are made of solid. In particular, the ionic conduction between the electrodes may be oxide ions.

[0022] The battery using the solid electrolyte in the present embodiment or the electrolyte layer containing the solid electrolyte can be particularly preferably used for a low-temperature operating battery. In the present embodiment, the low-temperature operating battery is a battery that operates at 300 to 1200°C, preferably 300 to 1000°C, more preferably 300 or more and less than 700°C, and particularly preferably 300 to 600°C, as described above.

[0023] The battery in the present embodiment includes, for example, an anode, a cathode, and the above-described solid electrolyte layer interposed therebetween. The cathode and the solid electrolyte may form an integrated cathode-solid electrolyte layer assembly.(Other applications of solid electrolyte)

[0024] Conventionally, perovskite-related compounds and solid electrolytes containing the perovskite-related compounds exhibit high ion conductivity, and thus are widely applied to batteries, sensors, ion concentrators, membranes used for ion separation, permeation, and the like, catalysts, and the like, and the solid electrolyte of the present embodiment can be applied in the same manner as these. For example, the solid electrolyte of the present embodiment can be used for other batteries, sensors, electrodes, electrolytes, oxygen concentrators, oxygen separation membranes, oxygen permeation membranes, oxygen pumps, catalysts, photocatalysts, electric / electronic / communication devices, energy / environment-related devices, and optical devices, in addition to the above-described solid oxide fuel cell (SOFC).

[0025] The solid electrolyte layer of the present embodiment described above can be used for a solid oxide fuel cell (SOFC), a sensor, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, an oxygen pump, or the like.

[0026] The solid electrolyte of the present embodiment can be used as an electrolyte of a gas sensor, for example, as a sensor. A gas sensor, gas detector, or the like can be constituted by attaching a sensitive electrode corresponding to the gas to be detected on the electrolyte. For example, a carbon dioxide sensor can be obtained when a sensitive electrode containing carbonate is used, a NOx sensor can be obtained when a sensitive electrode containing a nitrate is used, and an SOx sensor can be obtained when a sensitive electrode containing sulfate is used. Further, by assembling the electrolytic cell, a collecting device or a decomposing device for NOx and / or SOx contained in exhaust gas can be constituted.

[0027] The solid electrolyte of the present embodiment can be used as an adsorbent or an adsorption-separation agent for ions or the like, various catalysts, or the like.

[0028] In the solid electrolyte of the present embodiment, various rare earths in the ion conductor may act as an activator forming a light emission center (color center). In this case, it can be used as a wavelength-changing material or the like.

[0029] The solid electrolyte of the present embodiment may also become a superconductor by doping with electron carriers or hole carriers.

[0030] Regarding the solid electrolyte of the present embodiment, it is also possible to fabricate an all-solid-state electrochromic element by, using the solid electrolyte as an ion conductor, attaching an inorganic compound or the like which is colored or discolored by insertion / desorption of conduction ions to the surface thereof, and forming a translucent electrode such as ITO thereon. By using this all-solid-state electrochromic element, it is possible to provide an electrochromic display having memory characteristics with reduced power consumption.[Examples](Sample synthesis)(Test Examples 1 to 21)

[0031] The compounds shown in "Composition" of Test Examples 1 to 21 in Table 1 were prepared by the solid-phase reaction method. In the composition shown in Table 1, the oxygen amount calculated from the electrically neutral condition is shown assuming that the oxidation number of Ba is +2, the oxidation number of Nb is +5, the oxidation number of Mo is +6, the oxidation number of oxygen O is -2, the oxidation number of W is +6, the oxidation number of V is +5, the oxidation number of Cr is +6, the oxidation number of Ge is +4, the oxidation number of Si is +4, and the oxidation number of Zr is +4, but the oxygen amount (20+z) is not limited to the values shown because the oxygen non-stoichiometry z depends on the cation molar ratio, temperature, oxygen partial pressure, synthesis method, and thermal history. BaCO 3 , Nb 2 O 5 , MoO 3 , WO 3 , V 2 O 5 , Cr 2 O 3 , GeO 2 , SiO 2 , and ZrO 2 were used as starting materials. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for 30 minutes to 2 hours. The obtained mixture was calcined in the air at 900°C for 10 to 12 hours using an electric furnace. The calcined mixture was repeatedly subjected to wet mixing and grinding using ethanol and dry mixing and grinding in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets having a diameter of 10 to 20 mm by pressurizing at 62 to 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1100°C for 24 hours. As a result, pellets as a sintered body were obtained. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for 30 minutes to 1 hour by an agate mortar.

[0032] For the compounds having the compositions of Test Examples 1 and 6, high-density samples were prepared by means of applying hydrostatic pressure once before sintering. On the other hand, a sample sintered without being subjected to hydrostatic pressure treatment before sintering is called a low-density sample. Assuming a theoretical density for each sample of 5.85 g / cm 3< , the following relative densities were calculated: 100 × (density) / (theoretical density)%.

[0033] The high-density sample of Test Example 1 had a density of 5.2725 g / cm 3< and a relative density of 90.1%.

[0034] The low-density sample of Test Example 1 had a density of 3.9659 g / cm 3< and a relative density of 67.8%.

[0035] The high-density sample of Test Example 6 had a density of 5.5951 g / cm 3< and a relative density of 95.6%.

[0036] The low-density sample of Test Example 6 had a density of 3.9165 g / cm 3< and a relative density of 66.9%.

[0037] For each test example, XRD measurement was performed by a diffractometer Bruker D8. The obtained XRD pattern was indexed using DICVOL06 to obtain the lattice constant. The XRD pattern of Test Example 1 is shown in Fig. 1.

[0038] The results of XRD measurement of Test Examples 2 to 21 are also shown in Figs. 2 to 21, respectively. The lattice constants were determined from the obtained XRD patterns. The lattice constants (a, b, c, α, β, γ) and the lattice volume V of Test Examples 1 to 21 are shown in Table 1. [Table 1]CompositionCrystal latticea[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]Test Example 1Ba 7 Nb 4 MoO 20 5.86025.860216.53119090120491.72Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 5.86065.860616.53619090120491.87Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 5.86055.860516.54069090120491.99Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 5.85995.859916.52989090120491.57Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 5.85985.859816.52889090120491.50Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 5.85925.859216.51819090120491.11Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 5.86015.860116.53159090120491.65Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 5.86085.860816.53399090120491.83Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 5.86055.860516.53379090120491.78Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 5.86045.860416.53479090120491.79Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 5.85855.858516.50389090120490.56Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 5.85845.858416.52599090120491.19Test Example 13Ba 7 Nb 3.9 MoV 0.1 O 20 5.85575.855716.51149090120490.32Test Example 14Ba 7 Nb 3.9 MoCr 0.1 O 20.05 5.85395.853916.51229090120490.04Test Example 15Ba 7 Nb 3.8 MoCr 0.2 O 20.1 5.84745.847416.49859090120488.54Test Example 16Ba 7 Nb 3.7 MoCr 0.3 O 20.15 5.84745.847416.50849090120488.84Test Example 17Ba 7 Nb 3.9 MoGe 0.1 O 19.95 5.85555.855516.51569090120490.41Test Example 18Ba 7 Nb 3.9 MoSi 0.1 O 19.95 5.85795.857916.52579090120491.10Test Example 19Ba 7 Nb 3.9 MoZr 0.1 O 19.95 5.85975.859716.52049090120491.26Test Example 20Ba 7 Nb 4.05 Mo 0.9 O 19.975 5.85575.855716.52069090120490.59Test Example 21Ba 7 Nb 4.1 Mo 0.9 O 19.95 5.86245.862416.54639090120492.47 (Measurement of total electrical conductivity)

[0039] The electrical conductivity of each test example in Table 1 excluding Test Example 21 was measured by the DC four-terminal method. After reducing the particle size of the sample prepared in the above (Sample Synthesis) using a ball-mill, the sample was molded into pellets having a 5 mm φ by uniaxial pressing and sintered to prepare a sample for conductivity measurement. Four platinum wires were wound around a sintered body for measuring total electrical conductivity by the DC four-terminal method, and platinum paste was applied on the platinum wires in order to bring the sample and the platinum wires into close contact with each other. In order to remove organic components contained in the platinum or gold paste, the paste was heated at 900°C for 1 hour. The electrical conductivity measured for each test example is shown in Tables 2 to 9. In the composition shown in Tables 2 to 9, the oxygen amount calculated from the electrically neutral condition is shown assuming that the oxidation number of Ba is +2, the oxidation number of Nb is +5, the oxidation number of Mo is +6, the oxidation number of oxygen O is -2, the oxidation number of W is +6, the oxidation number of V is +5, the oxidation number of Cr is +6, the oxidation number of Ge is +4, the oxidation number of Si is +4, and the oxidation number of Zr is +4, but the oxygen amount (20+z) is not limited to the values shown because the oxygen non-stoichiometry z depends on the cation molar ratio, temperature, oxygen partial pressure, synthesis method, and thermal history. [Table 2]CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 1Ba 7 Nb 4 MoO 20 (high density)408°C-3.8Test Example 1Ba 7 Nb 4 MoO 20 (high density)505°C-3.3Test Example 1Ba 7 Nb 4 MoO 20 (high density)605°C-2.9Test Example 1Ba 7 Nb 4 MoO 20 (high density)705°C-2.6Test Example 1Ba 7 Nb 4 MoO 20 (high density)804°C-2.4Test Example 1Ba 7 Nb 4 MoO 20 (high density)904°C-2.3Test Example 1Ba 7 Nb 4 MoO 20 (low density)307°C-5.7Test Example 1Ba 7 Nb 4 MoO 20 (low density)408°C-4.7Test Example 1Ba 7 Nb 4 MoO 20 (low density)509°C-4Test Example 1Ba 7 Nb 4 MoO 20 (low density)610°C-3.4Test Example 1Ba 7 Nb 4 MoO 20 (low density)709°C-3Test Example 1Ba 7 Nb 4 MoO 20 (low density)809°C-2.7Test Example 1Ba 7 Nb 4 MoO 20 (low density)908°C-2.6Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 305°C-4.9Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 406°C-3.8Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 506°C-3.1Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 608°C-2.8Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 708°C-2.7Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 808°C-2.6Test Example 2Ba 7 Nb 3.98 Mo 1.02 O 20.01 908°C-2.5 [Table 3] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 307°C-4.7Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 410°C-3.6Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 510°C-2.9Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 610°C-2.6Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 710°C-2.5Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 809°C-2.4Test Example 3Ba 7 Nb 3.96 Mo 1.04 O 20.02 909°C-2.3Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 302°C-5.2Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 406°C-3.9Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 506°C-3.2Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 607°C-2.7Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 708°C-2.5Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 808°C-2.4Test Example 4Ba 7 Nb 3.94 Mo 1.06 O 20.03 905°C-2.4Test Example 4Ba 7 Nb 3.92 Mo 1.08 O 20.04 306°C-4.4Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 408°C-3.4Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 510°C-2.8Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 609°C-2.5Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 709°C-2.4Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 809°C-2.3Test Example 5Ba 7 Nb 3.92 Mo 1.08 O 20.04 908°C-2.2 [Table 4] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)280°C-3.7Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)358°C-3.2Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)457°C-2.7Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)561°C-2.3Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)658°C-2.1Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)721°C-2Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)840°C-1.9Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)878°C-1.9Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (high density)307°C-5.5Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)409°C-4.4Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)509°C-3.8Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)610°C-3.2Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)710°C-2.9Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)809°C-2.7Test Example 6Ba 7 Nb 3.9 Mo 1.1 O 20.05 (low density)909°C-2.5Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 305°C-5Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 406°C-3.7Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 507°C-3Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 607°C-2.6Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 707°C-2.4Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 808°C-2.3Test Example 7Ba 7 Nb 3.88 Mo 1.12 O 20.06 908°C-2.2 [Table 5] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 308°C-4.6Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 408°C-3.4Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 508°C-2.8Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 608°C-2.5Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 708°C-2.3Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 808°C-2.1Test Example 8Ba 7 Nb 3.86 Mo 1.14 O 20.07 907°C-2.1Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 304°C-4.5Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 406°C-3.4Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 506°C-2.7Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 607°C-2.4Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 707°C-2.2Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 807°C-2.2Test Example 9Ba 7 Nb 3.84 Mo 1.16 O 20.08 906°C-2.1Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 307°C-4.3Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 408°C-3.3Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 509°C-2.7Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 610°C-2.4Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 709°C-2.3Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 809°C-2.2Test Example 10Ba 7 Nb 3.82 Mo 1.18 O 20.09 908°C-2.1 [Table 6] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 306°C-4.1Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 409°C-3.3Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 508°C-2.8Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 608°C-2.5Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 707°C-2.2Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 808°C-2Test Example 11Ba 7 Nb 3.9 MoW 0.1 O 20.05 907°C-1.9Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 306°C-5.4Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 409°C-4.2Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 508°C-3.5Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 608°C-3.2Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 707°C-3.2Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 806°C-3.1Test Example 12Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 908°C-2.9Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 304°C-5.8Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 405°C-4.8Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 506°C-4.2Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 607°C-3.6Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 707°C-3.1Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 807°C-2.9Test Example 13Ba 7 Nb 3.9 V 0.1 MoO 20 908°C-2.8 [Table 7] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 304°C-5.5Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 402°C-4.5Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 505°C-3.6Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 605°C-3Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 706°C-2.6Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 807°C-2.4Test Example 14Ba 7 Nb 3.9 Cr 0.1 MoO 20.05 907°C-2.3Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 309°C-5Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 410°C-3.7Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 509°C-3Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 610°C-2.6Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 710°C-2.3Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 809°C-2.2Test Example 15Ba 7 Nb 3.8 Cr 0.2 MoO 20.1 908°C-2.2Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 302°C-4.6Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 401°C-3.9Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 505°C-3.1Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 607°C-2.7Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 700°C-2.4Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 803°C-2.4Test Example 16Ba 7 Nb 3.7 Cr 0.3 MoO 20.15 905°C-2.5 [Table 8] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 303°C-5.6Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 406°C-4.7Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 506°C-4Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 607°C-3.5Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 707°C-3.3Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 808°C-3.1Test Example 17Ba 7 Nb 3.9 Ge 0.1 MoO 19.95 908°C-2.9Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 309°C-5.2Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 409°C-4.1Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 510°C-4.1Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 610°C-4Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 709°C-3.6Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 809°C-3.5Test Example 18Ba 7 Nb 3.9 Si 0.1 MoO 19.95 908°C-3.3 [Table 9] CompositionTotal electrical conductivity (=oxide ion conductivity)Temperaturelog (σ total (S cm -1< ))Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 305°C-6.2Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 404°C-5.5Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 504°C-4.6Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 606°C-4Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 707°C-3.6Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 807°C-3.4Test Example 19Ba 7 Nb 3.9 Zr 0.1 MoO 19.95 907°C-3.3Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 305°C-4.8Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 406°C-3.7Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 506°C-3Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 607°C-2.7Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 707°C-2.6Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 807°C-2.5Test Example 20Ba 7 Nb 4.05 Mo 0.95 O 19.975 907°C-2.4

[0040] From Tables 2 to 9, for all of Test Examples 2 to 20, the electrical conductivity represented by log [σ(Scm -1< )] in the temperature range of 280 to 909°C was within the range of -7.0 to -1.0. In Test Examples 2 to 20, the electrical conductivity represented by log [σ(Scm -1< )] obtained by extrapolation from the electrical conductivity at 300°C or the above data and Figs. 22 to is -6.2 or more. Therefore, for all of Test Examples 2 to 20, high electrical conductivity can be obtained at a low temperature. Further, the electrical conductivity at 300°C is higher than -5.0 in Test Examples 2, 3, 5, 6 (high density), 8 to 11, 16, and 20. Of all the test examples, the test example having the highest electrical conductivity at around 300°C described above is Test Example 6, and the value of the electrical conductivity log [σ(Scm -1< )] at 280°C is -3.7. Although the electrical conductivity for Test Example 21 was not measured, it is considered that it exhibits electrical (ionic) conduction in the same manner as in Ba 7 Nb 4.05 Mo 0.95 O 19.975 of Test Example 20.

[0041] Fig. 22 shows a graph (Arrhenius plot) in which log [σ(Scm -1< )] is plotted on the vertical axis and 1000T -1< / K -1< is plotted on the horizontal axis for the absolute temperature T obtained from the temperature of the table for each electrical conductivity σ of conventionally used YSZ (Comparative Example 1), Test Example 1 (Ba 7 Nb 4 MoO 20 ) (high density), and Test Example 6 (Ba 7 Nb 3.9 Mo 1.1 O 20.05 ) (high density).

[0042] From Fig. 22, the electrical conductivity increases as the temperature rises. At 600°C, the electrical conductivity σ of Test Example 6, in which the excess amount x of Mo was 0.10, was 5.5 times higher than the electrical conductivity of Ba 7 Nb 4 MoO 20 of Test Example 1, indicating that the electrical conductivity was improved by increasing the Mo amount.

[0043] In the conventional Test Example 1, the log [σ(Scm -1< )] = -2.7 at 600°C. In Test Example 6, in which the excess amount x of Mo was set to 0.10, the log [σ(Scm -1< )] was higher than those of YSZ and Test Example 1 at a temperature of 590°C or less, indicating that the electrical conductivity was higher than that of a conventionally used electrolyte.

[0044] Further, Fig. 23 shows an Arrhenius plot of the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the excess amount x of Mo is 0.02 to 0.10 in the general formula (7), and Fig. 24 shows an Arrhenius plot of the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the excess amount x of Mo is 0.10 to 0.18. For comparison, Figs. 23 and 24 also show the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the excess amount x of Mo of Test Examples of the present example is 0.0. Test Examples 1 (high density, low density), 2, 3, 4, 5, 6 (high density, low density), 7, 8, 9, and 10 correspond to samples in which the excess amount x of Mo (x in Ba 7 Nb (4-x) Mo (1+x) O (20+z) of the general formula (7)) is 0 (high density, low density), 0.02, 0.04, 0.06, 0.08, 0.10 (high density, low density), 0.12, 0.14, 0.16, and 0.18, respectively.

[0045] The electrical conductivity of Test Example 1 (x = 0) and Test Example 6 (x = 0.10) of the high-density sample is higher than that of the low-density sample at any temperature.

[0046] All of the samples in which the excess amount x of Mo is in the range of 0.02 to 0.18 (Test Examples 2 to 10) show higher electrical conductivity than the low-density sample of Ba 7 Nb 4 MoO 20 (Test Example 1) in which the excess amount x of Mo is 0. The high-density sample in which the excess amount x of Mo is 0.10 has the highest electrical conductivity, and high electrical conductivity is maintained even at a low temperature of about 300°C.

[0047] Fig. 25 shows an Arrhenius plot of the electrical conductivity of Ba 7 Nb 4 MoO 20 (y = 0.10 in the general formulas (4) to (7)) in which the doping amount y of W, V (substituting part of Mo), V (substituting part of Nb), Cr, Si, Ge, and Zr is 0.1. Test Examples 11, 12, 13, 14, 17, 18, and 19 described above correspond to results of compounds doped with W (substituting part of Nb), V (substituting part of Mo), V, Cr, Ge, Si, and Zr (substituting part of Nb), respectively. Among these compounds, the compound doped with W has the highest electrical conductivity in all of the plotted temperature regions. In other Test Examples, the electrical conductivity of the compound doped with Cr and V (substituting part of Mo) is high at a high temperature, but the electrical conductivity of the compound doped with Si increases when 1000T -1< / K -1< becomes 1.4 or more, that is, at a low temperature of approximately 441°C or less.

[0048] Further, Fig. 26 shows an Arrhenius plot of the electrical conductivity of Ba 7 Nb 4 MoO 20 in which the doping amount y of Cr is 0.10 to 0.30 (Ba 7 Nb (4-y) MoCr y O (20+z) in which y = 0.10 to 0.30 in the general formula (10)). Test Examples 14, 15, and 16 described above correspond to samples having a doping amount y of 0.10, 0.20, and 0.30, respectively. The electrical conductivity of Ba 7 Nb 4 MoO 20 (y = 0.10 to 0.30) in which the doping amount y of Cr is 0.10 to 0.30 is higher than that of Ba 7 Nb 4 MoO 20 at 800°C or lower.(Oxygen partial pressure dependence of total electrical conductivity)

[0049] For Test Example 1, the oxygen partial pressure dependence of total electrical conductivity was measured. Samples were prepared in the same manner as described above (measurement of total electrical conductivity). The oxygen partial pressure was controlled by using an oxygen O 2 gas, a nitrogen N 2 gas, and an N 2 / H 2 mixed gas.

[0050] The oxygen partial pressure dependence of total electrical conductivity was measured at an oxygen partial pressure range of 3.5 × 10 -25< to 0.2 atm and 900°C. The oxygen partial pressure was monitored using an oxygen sensor installed downstream of the device. The oxygen partial pressure was controlled by mixing a small amount of the N 2 / H 2 mixed gas with the nitrogen gas.

[0051] Fig. 27 shows a graph in which the measured electrical conductivity log [σ(Scm -1< )] is plotted on the vertical axis with respect to the oxygen partial pressure log [P(O 2 ) / atm] on the horizontal axis. It was strongly suggested that oxide ions were the dominant carriers in the electrical conduction of the compound of Test Example 1 because the total electrical conductivity was almost constant regardless of the oxygen partial pressure. Test Examples 2 to 21 having similar crystal structures are also considered to be compounds having oxide ions as dominant carriers.(Evaluation of oxide ion transference number)

[0052] For Test Example 6, in order to determine the oxide ion transference number, the electromotive force was measured by an oxygen concentration cell using air gas and an N 2 / O 2 mixed gas. After reducing the particle diameter of the sample prepared in the above-mentioned (Sample Synthesis) using a ball-mill, the sample was molded into pellets having a 25 mm φ by uniaxial pressing, and hydrostatic pressure was applied. The sample was sintered at 1200°C for 12 hours to prepare a high-density sample of Test Example 6 for measuring electromotive force. The surface of the sample was scraped with a diamond slurry to make it smooth. The relative density of the pellets of Test Example 6 was 96.0%. A Pt paste having a diameter of about 10 mm was applied to the center of the pellet and heated at 1000°C for 1 hour in order to remove the organic component contained in the platinum paste. The platinum paste and the platinum electrode were bonded with instant adhesives, and the alumina tube, glass seal, and sample were also bonded with instant adhesives and the platinum electrode was attached. A clamp made of alumina was used as a presser for the measurement. After heating at 1000°C for 1 hour for adhesion of the glass seal, the oxide ion transference number of Test Example 6 was determined at 800°C and 900°C by measuring the electromotive force with an oxygen concentration cell.

[0053] Fig. 28 and Fig. 29 respectively show the electromotive force / mV plotted on the vertical axis and the oxygen partial pressure log [P(O 2 ) / atm] plotted on the horizontal axis for the result of electromotive force measurement of the oxygen concentration cell of Test Example 6 at temperatures of 800°C and 900°C. The measured values showed that the electromotive force obtained was close to the theoretical value, in particular, the transference number of oxide ions at 900°C was 94%, indicating that the oxide ions were the dominant carriers in the electrical conduction of the compound of Test Example 6, and that the compound of Test Example 6 was an oxide ion conductor. It is considered that the same transference numbers are shown for Test Examples 1 to 5 and 7 to 21 having similar crystal structures.(Structural optimization by density functional theory calculation)

[0054] Structural optimization calculations based on density functional theory were performed on Ba 7 Nb 3 MoMO 20 . Here, M is a cation of at least one element selected from the group consisting of Ag, Al, At, Au, Be, Bi, Br, Ca, Cd, Ce, Co, Cr, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, Ir, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Np, Os, P, Pb, Pd, Po, Pr, Pt, Pu, Re, Rh, Ru, S, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Tc, Te, Ti, Tl, Tm, U, V, W, Xe, Y, Yb, Zn, and Zr. Structural optimization calculation was further performed on Ba 7 Nb 3 Mo 2 O 20 . Density functional theory calculation using generalized gradient approximation and PBE functional was performed using the program VASP. Tables 10 to 12 and 33 to 36 show the results of the lattice constants obtained by the structural optimization. The optimized structures of all compositions retain the crystal structure of the original hexagonal perovskite-related compounds, indicating the possibility that these compositions can be synthesized. These compositions are also considered to exhibit oxide ion conduction. [Table 10]CompositionLattice constanta(Å)b(Å)c(Å)α(°)β(°)γ(°)Ba 7 Nb 3 MoAgO 20 5.9399035.93990316.79299090120Ba 7 Nb 3 MoAlO 20 5.9004045.90040416.7431769090120Ba 7 Nb 3 MoAtO 20 6.0105146.01051416.8605869090120Ba 7 Nb 3 MoAuO 20 5.940455.9404516.7766559090120Ba 7 Nb 3 MoBeO 20 5.9042665.90426617.1673259090120Ba 7 Nb 3 MoBiO 20 5.9920085.99200816.8361639090120Ba 7 Nb 3 MoBrO 20 5.9449145.94491416.8106879090120Ba 7 Nb 3 MoCdO 20 6.004396.0043916.9154179090120Ba 7 Nb 3 MoCoO 20 5.8815625.88156216.7377019090120Ba 7 Nb 3 MoCrO 20 5.8835035.88350316.7383259090120Ba 7 Nb 3 MoCuO 20 5.9061615.90616116.7618789090120Ba 7 Nb 3 MoFeO 20 5.8833435.88334316.734959090120Ba 7 Nb 3 MoGaO 20 5.9337365.93373616.7640849090120Ba 7 Nb 3 MoGeO 20 5.9022955.90229516.7686939090120Ba 7 Nb 3 MoHfO 20 5.9689765.96897616.7909979090120Ba 7 Nb 3 MoHgO 20 5.9873965.98739616.864099090120Ba 7 Nb 3 MoIO 20 5.9892675.98926716.8244099090120Ba 7 Nb 3 MoInO 20 5.9934785.99347816.8233559090120 [Table 11] CompositionLattice constanta(Å)b(Å)c(Å)α(°)β(°)γ(°)Ba 7 Nb 3 MoIrO 20 5.9210315.92103116.7763589090120Ba 7 Nb 3 MoLiO 20 5.9734545.97345416.8486259090120Ba 7 Nb 3 MoMgO 20 5.9622215.96222116.7701249090120Ba 7 Nb 3 MoMnO 20 5.8855795.88557916.7468779090120Ba 7 Nb 3 Mo 2 O 20 5.9259055.92590516.7660749090120Ba 7 Nb 4 MoO 20 5.9391875.93918716.7850919090120Ba 7 Nb 3 MoNiO 20 5.8855215.88552116.7436379090120Ba 7 Nb 3 MoNpO 20 6.0064286.00642816.821759090120Ba 7 Nb 3 MoOsO 20 5.9244425.92444216.7650139090120Ba 7 Nb 3 MoPO 20 5.841065.8410616.7130449090120Ba 7 Nb 3 MoPbO 20 6.0062456.00624516.855839090120Ba 7 Nb 3 MoPdO 20 5.9239565.92395616.7783079090120Ba 7 Nb 3 MoPoO 20 6.0069666.00696616.8670889090120Ba 7 Nb 3 MoPtO 20 5.925245.9252416.7798349090120Ba 7 Nb 3 MoPuO 20 6.0042236.00422316.8270159090120Ba 7 Nb 3 MoReO 20 5.9247475.92474716.7656519090120Ba 7 Nb 3 MoRhO 20 5.915235.9152316.7801449090120Ba 7 Nb 3 MoRuO 20 5.917875.9178716.7682069090120 [Table 12] CompositionLattice constanta(Å)b(Å)c(Å)α(°)β(°)γ(°)Ba 7 Nb 3 MoSO 20 5.9931615.99316117.0627329090120Ba 7 Nb 3 MoSbO 20 5.9456255.94562516.7883849090120Ba 7 Nb 3 MoScO 20 5.9716765.97167616.7852529090120Ba 7 Nb 3 MoSeO 20 5.9265115.92651116.797299090120Ba 7 Nb 3 MoSiO 20 5.8603835.86038316.7113539090120Ba 7 Nb 3 MoSnO 20 5.9668845.96688416.7859869090120Ba 7 Nb 3 MoTaO 20 5.9403755.94037516.7921279090120Ba 7 Nb 3 MoTbO 20 6.0335146.03351416.8976249090120Ba 7 Nb 3 MoTcO 20 5.9168675.91686716.7632189090120Ba 7 Nb 3 MoTeO 20 5.9764775.97647716.8041579090120Ba 7 Nb 3 MoTiO 20 5.921035.9210316.7664049090120Ba 7 Nb 3 MoTlO 20 6.0148356.01483516.9153649090120Ba 7 Nb 3 MoUO 20 6.0076476.00764716.8260999090120Ba 7 Nb 3 MoVO 20 5.8923065.89230616.7502649090120Ba 7 Nb 3 MoWO 20 5.926595.9265916.7511679090120Ba 7 Nb 3 MoXeO 20 6.0743096.07430916.7527229090120Ba 7 Nb 3 MoZnO 20 5.9552335.95523316.7848699090120Ba 7 Nb 3 MoZiO 20 5.9782175.97821716.7933829090120 (Test Examples 22 to 83)

[0055] The compounds shown in the "Composition" of Test Examples 22 to 41 shown in Table 13, Test Examples 42 to 61 shown in Table 14, and Test Examples 62 to 83 shown in Table 15 were prepared according to the following procedure. In the composition shown in Tables 13 to 15, the oxygen amount calculated from the electrically neutral conditions is shown assuming that the oxidation number of Ba is +2, the oxidation number of Nb is +5, the oxidation number of Mo is +6, the oxidation number of oxygen O is -2, the oxidation number of W is +6, the oxidation number of V is +5, the oxidation number of Cr is +6, the oxidation number of Ge is +4, the oxidation number of Si is +4, the oxidation number of Zr is +4, the oxidation number of Ti is +4, the oxidation number of Al is +3, the oxidation number of Gd is +3, the oxidation number of Dy is +3, the oxidation number of Er is +3, the oxidation number of Ho is +3, the oxidation number of Tm is +3, the oxidation number of Yb is +3, and the oxidation number of Lu is +3, but the oxygen amount (20+z) is not limited to the values shown because the oxygen non-stoichiometry z depends on the cation molar ratio, temperature, oxygen partial pressure, synthesis method, and thermal history.(Test Examples 22 to 58 and 81 to 83)

[0056] The compounds shown in "Composition" of Test Examples 22 to 41 in Table 13, Test Examples 42 to 58 in Table 14, and Test Examples 81 to 83 in Table 15 were prepared by the solid-phase reaction method. As starting materials, BaCO 3 , Nb 2 O 5 , MoO 3 , WO 3 , V 2 O 5 , Cr 2 O 3 , MnO 2 , GeO 2 , SiO 2 , and ZrO 2 were used. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for 30 minutes to 2 hours. The obtained mixture was calcined in the air at 900°C for 10 to 12 hours using an electric furnace. The calcined mixture was repeatedly subjected to dry mixing and grinding and wet mixing and grinding using ethanol in an agate mortar for 30 minutes to 2 hours. The mixture was molded into cylindrical pellets having a diameter of 10 to 20 mm by pressurizing at 62 to 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1100°C for 24 hours. As a result, pellets as a sintered body were obtained. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for about 20 minutes by a grinder made of tungsten carbide (WC) and then ground for 30 minutes to 1 hour by an agate mortar.(Test Examples 59 to 67)

[0057] The compounds shown in "Composition" of Test Examples 59 to 61 in Table 14 and Test Examples 62 to 67 in Table 15 were prepared by the solid-phase reaction method. BaCO 3 , WO 3 , and V 2 O 5 were used as starting materials. The starting materials were dried in advance in an electric furnace at 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for 1 hour. The obtained mixture was calcined in the air at 950°C for 15 hours using an electric furnace. The calcined mixture was repeatedly subjected to mixing and grinding in an agate mortar for 1 hour in a dry manner and in a wet manner using ethanol. The mixture was molded into cylindrical pellets having a diameter of 10 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1020°C for 24 hours. As a result, pellets as a sintered body were obtained. The electrical conductivity was measured using the obtained sintered body. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for about 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 1 hour by an agate mortar.(Test Examples 68 to 70)

[0058] The compounds shown in "Composition" of Test Examples 68 to 70 in Table 15 were prepared by the solid-phase reaction method. BaCO 3 , TiO 2 , and MoO 3 were used as starting materials. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for 30 minutes. The obtained mixture was calcined in the air at 900°C for 12 hours using an electric furnace. The calcined mixture was repeatedly subjected to mixing and grinding in an agate mortar for about 1 hour in a dry manner and in a wet manner using ethanol. The mixture was molded into cylindrical pellets having a diameter of 20 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1100°C for 24 hours. The obtained sintered body was ground for 20 minutes by a grinder made of a tungsten carbide (WC), and then ground in an agate mortar for about 1 hour. The mixture was molded into cylindrical pellets having a diameter of 5 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1100°C for 12 hours. As a result, pellets as a sintered body were obtained. The electrical conductivity was measured using the obtained sintered body. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 1 hour by an agate mortar.(Test Example 71)

[0059] The compound shown in "Composition" of Test Example 71 in Table 15 was prepared by the solid-phase reaction method. BaCO 3 , MnO 2 , and CaCO 3 were used as starting materials. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for about 1 hour. The obtained mixture was calcined in the air at 900°C for 12 hours using an electric furnace. The calcined mixture was repeatedly subjected to dry mixing and grinding and wet mixing and grinding using ethanol in an agate mortar for 30 minutes. The mixture was molded into cylindrical pellets having a diameter of 20 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1200°C for 12 hours. The obtained sintered body was ground for 20 minutes by a grinder made of a tungsten carbide (WC), and then ground in an agate mortar for about 1 hour. The mixture was molded into cylindrical pellets having a diameter of 5 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1400°C for 24 hours. As a result, pellets as a sintered body were obtained. The electrical conductivity was measured using the obtained sintered body. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 1 hour by an agate mortar.(Test Example 72)

[0060] The compound shown in "Composition" of Test Example 72 in Table 15 was prepared by the solid-phase reaction method. BaCO 3 , MnO 2 , La 2 O 3 , and CaCO 3 were used as starting materials. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for about 1 hour. The obtained mixture was calcined in the air at 900°C for 10 hours using an electric furnace. The calcined mixture was repeatedly subjected to mixing and grinding in an agate mortar for about 1 hour in a dry manner and in a wet manner using ethanol. The mixture was molded into cylindrical pellets having a diameter of 5 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1200°C for 12 hours. The obtained sintered body was ground for 20 minutes by a grinder made of a tungsten carbide (WC), and then ground in an agate mortar for about 1 hour. The mixture was molded into cylindrical pellets having a diameter of 5 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1200°C for 12 hours. As a result, pellets as a sintered body were obtained. The electrical conductivity was measured using the obtained sintered body. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 1 hour by an agate mortar.(Test Example 73)

[0061] The compound shown in "Composition" of Test Example 73 in Table 15 was prepared by the solid-phase reaction method. La 2 CO 3 , MnO 2 , and CaCO 3 were used as starting materials. The starting materials were dried in advance in an electric furnace at 250 to 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for about 1 hour. The obtained mixture was calcined in the air at 900°C for 12 hours using an electric furnace. The calcined mixture was repeatedly subjected to mixing and grinding in an agate mortar for about 1 hour in a dry manner and in a wet manner using ethanol. The mixture was molded into cylindrical pellets having a diameter of 5 mm by pressurizing at 150 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1200°C for 12 hours. As a result, pellets as a sintered body were obtained. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 1 hour by an agate mortar. This compound also has a crystal structure similar to that of the compounds of Test Examples 1 to 21, and thus is considered to have oxide ion conductance.(Test Examples 74 to 80)

[0062] The compounds shown in the "composition" of Test Examples 74 to 80 in Table 15 were prepared by the solid-phase reaction method. BaCO 3 , Al 2 O 3 , ZrO 2 , Gd 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , and Lu 2 O 3 were used as starting materials. The starting materials were dried in advance in an electric furnace at 300°C for 12 hours, and then weighed with an electronic balance so that the molar ratio of cations was at the desired chemical composition. Using an agate mortar, dry mixing and grinding and wet mixing and grinding using ethanol were repeatedly performed for 30 minutes. The obtained mixture was calcined in the air at 900°C for 10 hours using an electric furnace. The calcined mixture was subjected to mixing and grinding in an agate mortar for 30 minutes in a dry manner. The mixture was molded into cylindrical pellets having a diameter of 20 mm by pressurizing at about 50 MPa using a uniaxial press. The obtained pellets were placed in an electric furnace and sintered in the air at 1600°C for 12 hours to obtain a sintered body. The electrical conductivity was measured using the obtained sintered body. In order to evaluate the product phase of the obtained compound by X-ray diffraction (XRD), a part of the sintered body was ground for 20 minutes by a grinder made of tungsten carbide (WC) and then ground for about 30 minutes by an agate mortar.

[0063] Each table also shows the lattice constant and the lattice volume V of Test Examples 22 to 83. Further, for some Test Examples, the activation energy Ea (eV) of conductivity estimated from the temperature dependence of the total electrical conductivity is also shown. The transference number of Test Example 27 at 900°C was 100%.

[0064] Fig. 30 shows a crystal structure of Ba 7 Nb 4 MoO 20 used in Test Example 22. In this figure, the space group is P-3m1 (No. 164), and the lattice constants are a = b = 5.8602 Å and c = 16.5311 Å. Test Examples 23 to 58 and 81 to 83, which are Ba 7 Nb 4 MoO 20 -based materials, also have similar crystal structures. Figs. 31 and 32 are a graph showing the XRD patterns of Ba 7 Nb (4-x) Mo (1+x) O (20+z) . Fig. 31 shows the measurement charts for x = 0, 0.02, 0.04, 0.06, 0.08, 0.1, and Fig. 32 shows the measurement charts for x = 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.25, 0.3, 0.4, 0.5. The conductivity of Ba 7 Nb (4-x) Mo (1+x) O (20+z) is plotted in a temperature-dependent manner for each value of x in Fig. 33 and in a composition-dependent manner for each temperature value in Fig. 34.

[0065] Fig. 35 is a graph showing the XRD pattern of Ba 7 Nb (4-y) MoCr y O (20+z) used in Test Examples 40 to 44 and 46. The measurement charts for x = 0.1, 0.2, 0.25, 0.3, 0.4, 0.5 are shown. The conductivity of Ba7Nb(4-x)Mo(1+x)O(20+z) is plotted in a temperature-dependent manner in Fig. 36.

[0066] The conductivity of Ba 7 Nb (4-y) MoCr y O (20+z) used in Test Examples 22, 40 to 44, and 46 is plotted in a composition-dependent manner in Fig. 37.

[0067] Fig. 38 is a graph showing the XRD patterns of Ba 7 Nb (4-y) MoW y O (20+z) used in Test Examples 52 to 58 and 81 and 83. Fig. 39 shows the total electrical conductivity of Ba 7 Nb (4-y) MoW y O (20+z) in a temperature-dependent manner. Fig. 40 shows the total electrical conductivity of Ba 7 Nb (4-y) MoW y O (20+z) in a composition-dependent manner.

[0068] Fig. 41 is a graph showing XRD patterns of Ba 7 Nb 3.9 MoM 0.1 O (20+z) (M is V, Mn, Ge, Si, or Zr), Ba 7 Nb 4 Mo 0.9 M 0.10 O (20+z) (M is V or Mn), and Ba 7 Nb 4.05 Mo 0.95 O (20+z) as other solid solutions used in Test Examples 38, 39, 45, and 47 to 51. Fig. 42 shows the electrical conductivity of the solid solutions used in Test Examples 38, 39, and 47 to 50 in a temperature-dependent manner.

[0069] Fig. 43 shows the crystal structure of a Ba 3 WVO 8.5 -based material used in Test Examples 59 to 67. At present, the Ba 3 WVO 8.5 system is said to have the crystal structure of Fig. 43(a), but the crystal structures of Figs. 43(b) and (c) are proposed from the analysis results. In these figures, the space group is R-3m (No. 166), and the lattice constants are a = b = 5.808130 (19) Å and c = 21.094919 (21) Å. Fig. 44 is a graph showing the XRD patterns of Ba 3 W (1-x) V (1-x) O (8.5+z) . Fig. 45 shows the electrical conductivity in a temperature-dependent manner. Fig. 46 shows the electrical conductivity in a composition-dependent manner. The electrical conductivity increases as the temperature rises. At 600°C, the electrical conductivity σ of Ba 3 W 1.6 V 0.4 O 8.8 of Test Example 66 was 85 times higher than the electrical conductivity of Ba 3 WVO 8.5 of Test Example 59, indicating that the electrical conductivity was improved by increasing the W amount. The same applies to Test Examples 59 to 65 and 67, which are also Ba 3 WVO 8.5 -based materials.

[0070] Fig. 47 shows the P (O 2 ) dependence of conductivity for Ba 3 W 1.6 V 0.4 O 8.8 of Test Example 66. It is suggested that oxide ions are the dominant carriers in the region in the electrical conduction of the compound of Test Example 66 because there is a region where the total electrical conductivity is almost constant regardless of the oxygen partial pressure. Fig. 48 shows the conductivity of Ba 3 W 1.6 V 0.4 O 8.8 in dry air and in moist air. No change in total electrical conductivity was observed in measurements in moist air and dry air with respect to Test Example 66, strongly suggesting that no proton conduction occurred in Test Example 66. The same applies to Test Examples 59 to 65 and 67, which are also Ba 3 WVO 8.5 -based materials.

[0071] Fig. 49 shows the crystal structure of a Ba 3 MoTiO 8 -based material used in Test Examples 68 to 70. In this figure, the space group is R-3m (No. 166), and the lattice constants are a = b = 5.9548Å and c = 21.2924Å. Fig. 50 is a graph showing the XRD pattern of Ba 3 Mo (1-x) Ti (1+x) O (8+z) .

[0072] Fig. 51 shows the temperature dependence of the electrical conductivity of Ba 3 Mo 1.1 Ti 09 O 8.1 and Ba 3 Mo 1.2 Ti 0.8 O 8.2 in which the excess amount x of Ti is -0.1 and - 0.2. The temperature dependence of the electrical conductivity of Ba 3 MoTiO 8 in which the excess amount x of Mo of Test Example of the present example is 0.0 is also shown. All of the samples in which the excess amount x of Mo is in the range of -0.1 and -0.2 show higher electrical conductivity than the sample of Ba 3 MoTIO 8 (Test Example 68) in which the excess amount x of Mo is 0.0. At 620°C or less, the sample in which the excess amount x of Mo is -0.1 has the highest electrical conductivity, and high electrical conductivity is maintained even at a low temperature of about 300°C.(Oxygen partial pressure dependence of total electrical conductivity)

[0073] For Test Example 69, the oxygen partial pressure dependence of total electrical conductivity was measured. Fig. 52 shows a graph in which the measured electrical conductivity log [σ(Scm -1< )] is plotted on the vertical axis with respect to the oxygen partial pressure log [P(O 2 ) / atm] on the horizontal axis. It was strongly suggested that oxide ions were the dominant carriers in the electrical conduction of the compound of Test Example 69 because the total electrical conductivity was almost constant regardless of the oxygen partial pressure. The same applies to Test Examples 68 and 70, which are also Ba 3 MoTiO 8 -based materials.

[0074] Fig. 53 shows the crystal structure of a Ba 7 Ca 2 Mn 5 O 20 -based material used in Test Example 71. In this figure, the space group R-3m (No. 166), the lattice constants a = b = 5.8195Å, and c = 51.3701Å. Fig. 54 is a graph showing the XRD pattern of Ba 7 Ca 2 Mn 5 O 20 . Fig. 55 shows the total electrical conductivity of Ba 7 Ca 2 Mn 5 O 20 in a temperature-dependent manner.

[0075] Fig. 56 shows the crystal structure of a Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 -based material used in Test Example 72. The space group of Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 is C2 / m (No. 12), and the lattice constants are a = 9.8394 Å, b = 5.6823 Å, c = 15.6435 Å, and β = 102.09 °. Fig. 57 is a graph showing the XRD pattern of Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 . Fig. 58 shows the total electrical conductivity of Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 in a temperature-dependent manner.

[0076] Fig. 59 shows the crystal structure of a La 2 Ca 2 MnO 7 -based material used in Test Example 73. In this figure, the space group is R-3m (No. 166), and the lattice constants are a = b = 5.6200 Å and c = 17.2954 Å. Fig. 60 is a graph showing the XRD pattern of La 2 Ca 2 MnO 7 .

[0077] Fig. 61 shows the crystal structure of the Ba 5 M 2 Al 2 ZrO 13 -based material used in Test Examples 74 to 80. In this figure, the space group is P63 / mmc (No. 194), and the lattice constants are a = b = 5.9629 Å and c = 24.7340 Å. Fig. 62 is a graph showing the XRD patterns of Ba 5 M 2 Al 2 ZrO 13 (M is Gd, Dy, Er, Ho, Tm, Yb, Lu). Fig. 63 shows the total electrical conductivity of Ba 5 M 2 Al 2 ZrO 13 measured in the air in a temperature-dependent manner. For Test Example 76, the total electrical conductivity in dry air was also shown in a temperature-dependent manner. The reduced conductivity in dry air suggests that Test Example 76 exhibits proton conduction. The same applies to Test Examples 74, 75, and 77 to 80, which are also Ba 5 M 2 Al 2 ZrO 13 -based materials. [Table 13]CompositionLattice constantActivation energya[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]E a (eV)Example 22Ba 7 Nb 4 MoO 20 5.86025.860216.53119090120491.720.52Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 5.86065.860616.53619090120491.870.49Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 5.86055.860516.54069090120491.990.49Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 5.86225.862216.53379090120492.060.47Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 5.85985.859816.52889090120491.500.51Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 5.85855.858516.54089090120491.650.44Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 5.86015.860116.53159090120491.650.48Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 5.86085.860816.53399090120491.830.54Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 5.86055.860516.53379090120491.780.52Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 5.86045.860416.53479090120491.790.47Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 5.86115.861116.53629090120491.950.41Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 5.85945.859416.53649090120491.670.42Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 5.86315.863116.54179090120492.450.43Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 5.87215.872116.5199090120493.290.44Example 36Ba 7 Nb 3.6 Mo 1.4 O 20.2 5.8655.865016.5449090120492.84Example 37Ba 7 Nb 3.5 Mo 1.5 O 20.25 5.87595.875916.52159090120494.00Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 5.85845.858416.52599090120491.190.53Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 5.85575.855716.51149090120490.320.69Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 5.85395.853916.51229090120490.040.59Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 5.84745.847416.49859090120488.540.43 [Table 14] CompositionLattice constantActivation energya[Å]b[Å]c[Å]a[Å]b[Å]γ[°]a[Å]b[Å]Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20 / 125 5.85465.854616.53199090120490.740.58Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 5.84745.847416.50849090120488.840.47Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 5.84915.849116.53539090120489.920.48Example 45Ba 7 Nb 4 Mo 0.9 Mn 0.1 O 20.05 5.85505.855016.52189090120490.50Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 5.84835.848316.53689090120489.830.44Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 5.85555.855516.51569090120490.410.59Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 5.85795.857916.52579090120491.100.38Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 5.85975.859716.52049090120491.260.69Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 5.85575.855716.52069090120490.590.52Example 51Ba 7 Nb 3.9 MoMn 0.1 0 19.95 5.86095.860916.55339090120492.4292484Example 52Ba 7 Nb 3.9 MoW 0. 1 O 20.05 5.8775575.87755716.57039090120495.7410.48Example 53Ba 7 Nb 3.8 MoW 0 2 O 20.1 5.860355.8603516.51869090120491.310.51Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 5.8569665.85696616.5222979090120490.870.59Example 55Ba 7 Nb 3.6 MoW 0.4 O 20.2 5.861345.8613416.530549090120491.830.59Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 5.8573085.85730816.517669090120490.770.54Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 5.8572225.85722216.51999090120490.820.60Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 5.8539215.85392116.522479090120490.340.66Example 59Ba 3 WVO 8.5 5.808130(19)5.808130(19)21.094919(21)9090120615.4(9)1.72Example 60Ba 3 W 0.9 V 1.1 O 8.45 5.8225.82221.1599090120621.191.67Example 61Ba 3 W 0.95 V 1.05 O 8.475 5.8225.82221.1499090120620.801.81 [Table 15] CompositionLattice constantActivation energya[Å]b[Å]c[Å]a[Å]b[Å]γ[°]a[Å]b[Å]Test Example 62Ba 3 W 1.05 V 0.95 O 8.525 5.8235.82321.1329090120620.611.73Test Example 63Ba 3 W 1.1 V 0.9 O 8.55 5.8245.82421.1199090120620.311.67Test Example 64Ba 3 W 1.25 V 0.75 O 8.625 5.8165.81621.0219090120615.811.40Test Example 65Ba 3 W 1.5 V 0.5 O 8.75 5.8215.82121.0549090120617.881.11Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 5.821531(7)5.821531(7)21.03203(9)9090120617.290(4)1.02Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 5.81855665.818556620.99762529090120615.651.17Test Example 68Ba 3 MoTiO 8 5.95485.954821.29249090120653.891.00Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 5.94845.948421.26269090120651.560.78Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 5.93435.934321.22169090120647.211.03Test Example 71Ba 7 Ca 2 Mn 5 O 20 5.81955.819551.370190901201506.660.85Test Example 72Ba 2.6 Ca 2.4 La 4 Mn 4 O 19 9.83945.682315.643590102.09390855.23Test Example 73La 2 Ca 2 MnO 7 5.62005.620017.29549090120473.09Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 5.98075.980724.6619090120776.681.28Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 5.9475.94724.8179090120774.070.19Test Example 76Ba 5 Er 2 Al 2 ZrO 13 5.95475.946224.7099090120761.620.25Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 5.94625.934824.6729090120763.680.26Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 5.93485.926924.6359090120759.310.52Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 5.92695.926224.6039090120754.390.27Test Example 80Ba 3 Lu 2 Al 2 ZrO 13 5.92625.926924.6119090120753.880.24Test Example 81Ba 7 Nb 3 MoWO 20.5 5.8533555.85335516.51679090120490.08Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.075 5.8602415.86024116.53229090120491.69Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.125 5.8579225.85792216.519189090120490.92

[0078] Tables 16 to 32 show the results of Test Examples in which electrical conductivity was measured among Test Examples 22 to 83. In the composition shown in Tables 16 to 32, the oxygen amount calculated from the electrically neutral conditions is shown assuming that the oxidation number of Ba is +2, the oxidation number of Nb is +5, the oxidation number of Mo is +6, the oxidation number of oxygen O is -2, the oxidation number of W is +6, the oxidation number of V is +5, the oxidation number of Cr is +6, the oxidation number of Ge is +4, the oxidation number of Si is +4, the oxidation number of Zr is +4, the oxidation number of Ti is +4, the oxidation number of Al is +3, the oxidation number of Gd is +3, the oxidation number of Dy is +3, the oxidation number of Er is +3, the oxidation number of Ho is +3, the oxidation number of Tm is +3, the oxidation number of Yb is +3, and the oxidation number of Lu is +3, but the oxygen amount (20+z) is not limited to the values shown because the oxygen non-stoichiometry z depends on the cation molar ratio, temperature, oxygen partial pressure, synthesis method, and thermal history. [Table 16]CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 22Ba 7 Nb 4 MoO 20 306°C-4.6Example 22Ba 7 Nb 4 MoO 20 406°C-3.9Example 22Ba 7 Nb 4 MoO 20 506°C-3.4Example 22Ba 7 Nb 4 MoO 20 606°C-3.0Example 22Ba 7 Nb 4 MoO 20 706°C-2.7Example 22Ba 7 Nb 4 MoO 20 807°C-2.5Example 22Ba 7 Nb 4 MoO 20 907°C-2.3Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 306°C-4.5Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 406°C-3.8Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 506°C-3.3Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 606°C-2.9Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 706°C-2.7Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 806°C-2.5Example 23Ba 7 Nb 3.98 Mo 1.02 O 20.01 906°C-2.3Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 307°C-4.7Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 410°C-3.6Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 510°C-2.9Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 610°C-2.6Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 710°C-2.5Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 809°C-2.4Example 24Ba 7 Nb 3.96 Mo 1.04 O 20.02 909°C-2.3 [Table 17] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 304°C-4.3Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 406°C-3.6Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 506°C-3.1Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 606°C-2.8Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 706°C-2.6Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 806°C-2.4Example 25Ba 7 Nb 3.94 Mo 1.06 O 20.03 906°C-2.2Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 306°C-4.4Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 408°C-3.7Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 510°C-3.1Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 609°C-2.8Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 709°C-2.5Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 809°C-2.3Example 26Ba 7 Nb 3.92 Mo 1.08 O 20.04 908°C-2.1Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 305°C-4.1Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 407°C-3.4Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 505°C-2.9Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 606°C-2.6Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 706°C-2.4Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 807°C-2.2Example 27Ba 7 Nb 3.9 Mo 1.1 O 20.05 906°C-2.1 [Table 18] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 307°C-4.3Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 406°C-3.6Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 507°C-3.1Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 607°C-2.7Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 707°C-2.5Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 807°C-2.3Example 28Ba 7 Nb 3.88 Mo 1.12 O 20.06 906°C-2.2Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 306°C-4.2Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 407°C-3.3Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 506°C-2.8Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 606°C-2.3Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 706°C-2.1Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 806°C-1.9Example 29Ba 7 Nb 3.86 Mo 1.14 O 20.07 907°C-1.8Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 305°C-4.0Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 406°C-3.3Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 506°C-2.7Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 606°C-2.3Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 706°C-2.1Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 806°C-1.9Example 30Ba 7 Nb 3.84 Mo 1.16 O 20.08 906°C-1.8 [Table 19] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 307°C-3.7Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 408°C-3.0Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 509°C-2.5Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 610°C-2.1Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 709°C-2.0Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 809°C-1.8Example 31Ba 7 Nb 3.82 Mo 1.18 O 20.09 908°C-1.7Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 306°C-3.4Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 406°C-2.8Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 506°C-2.3Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 606°C-2.0Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 706°C-1.8Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 807°C-1.7Example 32Ba 7 Nb 3.8 Mo 1.2 O 20.1 906°C-1.6Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 304°C-3.8Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 406°C-3.1Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 505°C-2.7Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 606°C-2.4Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 706°C-2.2Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 807°C-2.0Example 33Ba 7 Nb 3.78 Mo 1.22 O 20.11 907°C-1.9 [Table 20] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 305°C-3.8Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 407°C-3.1Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 507°C-2.7Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 607°C-2.4Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 706°C-2.2Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 807°C-2.0Example 34Ba 7 Nb 3.75 Mo 1.25 O 20.125 907°C-1.9Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 305°C-3.8Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 406°C-3.1Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 506°C-2.7Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 607°C-2.4Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 706°C-2.2Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 807°C-2.0Example 35Ba 7 Nb 3.7 Mo 1.3 O 20.15 907°C-1.9Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 306°C-5.4Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 409°C-4.2Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 508°C-3.5Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 608°C-3.2Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 707°C-3.2Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 806°C-3.1Example 38Ba 7 Nb 4 Mo 0.9 V 0.1 O 19.95 908°C-2.9 [Table 21] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 304°C-5.8Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 405°C-4.8Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 506°C-4.2Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 607°C-3.6Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 707°C-3.1Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 807°C-2.9Example 39Ba 7 Nb 3.9 MoV 0.1 O 20 908°C-2.8Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 306°C-4.5Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 406°C-3.6Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 507°C-3.0Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 607°C-2.6Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 707°C-2.2Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 807°C-2.1Example 40Ba 7 Nb 3.9 MoCr 0.1 O 20.05 907°C-2.0Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 303°C-3.9Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 403°C-3.2Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 504°C-2.7Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 605°C-2.4Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 705°C-2.2Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 806°C-2.1Example 41Ba 7 Nb 3.8 MoCr 0.2 O 20.1 906°C-2.0 [Table 22] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 307°C-4.6Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 407°C-3.8Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 507°C-3.2Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 607°C-2.7Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 707°C-2.4Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 807°C-2.2Example 42Ba 7 Nb 3.75 MoCr 0.25 O 20.125 907°C-2.1Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 307°C-4.0Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 407°C-3.2Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 507°C-2.7Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 607°C-2.4Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 707°C-2.1Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 807°C-2.0Example 43Ba 7 Nb 3.7 MoCr 0.3 O 20.15 906°C-2.0Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 307°C-4.2Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 407°C-3.4Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 507°C-2.9Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 607°C-2.5Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 707°C-2.2Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 807°C-2.1Example 44Ba 7 Nb 3.6 MoCr 0.4 O 20.2 907°C-2.2 [Table 23] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 305°C-4.2Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 406°C-3.5Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 506°C-3.0Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 606°C-2.6Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 706°C-2.3Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 806°C-2.3Example 46Ba 7 Nb 3.5 MoCr 0.5 O 20.25 907°C-2.3Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 303°C-5.6Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 406°C-4.7Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 506°C-4.0Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 607°C-3.5Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 707°C-3.3Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 808°C-3.1Example 47Ba 7 Nb 3.9 MoGe 0.1 O 19.93 908°C-2.9Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 309°C-5.2Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 409°C-4.1Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 510°C-4.1Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 610°C-4.0Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 709°C-3.6Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 809°C-3.5Example 48Ba 7 Nb 3.9 MoSi 0.1 O 19.95 908°C-3.3 [Table 24] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 305°C-6.2Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 404°C-5.5Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 504°C-4.6Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 606°C-4.0Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 707°C-3.6Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 807°C-3.4Example 49Ba 7 Nb 3.9 MoZr 0.1 O 19.95 907°C-3.3Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 305°C-4.8Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 406°C-3.7Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 506°C-3.0Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 607°C-2.7Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 707°C-2.6Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 807°C-2.5Example 50Ba 7 Nb 4.05 Mo 0.95 O 19.975 907°C-2.4Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 306°C-4.1Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 409°C-3.3Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 508°C-2.8Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 608°C-2.5Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 707°C-2.2Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 808°C-2.0Example 52Ba 7 Nb 3.9 MoW 0.1 O 20.05 907°C-1.9 [Table 25] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 53Ba 7 Nb 3.8 MoW 0.2 O 20.1 506°C-2.8Example 53Ba 7 Nb 3.8 MoW 0.2 O 20.1 606°C-2.3Example 53Ba 7 Nb 3.8 MoW 0.2 O 20.1 706°C-2.0Example 53Ba 7 Nb 3.8 MoW 0.2 O 20.1 806°C-1.8Example 53Ba 7 Nb 3.8 MoW 0.2 O 20.1 906°C-1.6Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 306°C-4.4Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 407°C-3.5Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 506°C-2.9Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 606°C-2.5Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 706°C-2.1Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 806°C-1.9Example 54Ba 7 Nb 3.7 MOW 0.3 O 20.15 906°C-1.7Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 506°C-2.9Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 606°C-2.4Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 706°C-2.1Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 806°C-1.8Example 56Ba 7 Nb 3.5 MoW 0.5 O 20.25 906°C-1.6 [Table 26] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 306°C-4.8Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 407°C-3.6Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 506°C-3.0Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 606°C-2.5Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 706°C-2.1Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 806°C-1.9Example 57Ba 7 Nb 3.4 MoW 0.6 O 20.3 906°C-1.7Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 506°C-2.9Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 606°C-2.4Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 706°C-2.0Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 806°C-1.7Example 58Ba 7 Nb 3.2 MoW 0.8 O 20.4 906°C-1.5Example 59Ba 3 WVO 8.5 602.8°C-5.5Example 59Ba 3 WVO 8.5 653°C-5.1Example 59Ba 3 WVO 8.5 703.2°C-4.6Example 59Ba 3 WVO 8.5 753.6°C-4.2Example 59Ba 3 WVO 8.5 803.9°C-3.9Example 59Ba 3 WVO 8.5 854.2°C-3.5Example 59Ba 3 WVO 8.5 904.2°C-3.2Example 59Ba 3 WVO 8.5 954.5°C-2.9Example 59Ba 3 WVO 8.5 1004.6°C-2.6 [Table 27] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 602.3°C-6.1Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 652.4°C-5.3Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 702.8°C-5.1Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 753.1°C-4.7Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 803.4°C-4.3Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 853.5°C-4.7Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 903.9°C-5.1Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 953.8°C-5.3Example 60Ba 3 Nb 0.9 MoW 1.1 O 8.45 1004°C-6.1Example 61Ba 3 W 0.95 V 1.05 O 8.475 602.8°C-5.6Example 61Ba 3 W 0.95 V 1.05 O 8.475 653°C-5.2Example 61Ba 3 W 0.95 V 1.05 O 8.475 703.2°C-4.8Example 61Ba 3 W 0.95 V 1.05 O 8.475 753.6°C-4.5Example 61Ba 3 W 0.95 V 1.05 O 8.475 803.9°C-4.1Example 61Ba 3 W 0.95 V 1.05 O 8.475 854.2°C-3.8Example 61Ba 3 W 0.95 V 1.05 O 8.475 904.2°C-3.5Example 61Ba 3 W 0.95 V 1.05 O 8.475 954.5°C-3.2Example 61Ba 3 W 0.95 V 1.05 O 8.475 1004.6°C-2.9Example 62Ba 3 W 1.05 V 0.95 O 8.525 603°C-5.3Example 62Ba 3 W 1.05 V 0.95 O 8.525 653.1°C-5.0Example 62Ba 3 W 1.05 V 0.95 O 8.525 703.4°C-4.7Example 62Ba 3 W 1.05 V 0.95 O 8.525 754°C-4.4Example 62Ba 3 W 1.05 V 0.95 O 8.525 804.3°C-4.0Example 62Ba 3 W 1.05 V 0.95 O 8.525 854.6°C-3.7Example 62Ba 3 W 1.05 V 0.95 O 8.525 904.7°C-3.3Example 62Ba 3 W 1.05 V 0.95 O 8.525 954.9°C-3.0Example 62Ba 3 W 1.05 V 0.95 O 8.525 1004.9°C-2.7 [Table 28] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Example 63Ba 3 W 1.1 V 0.9 O 8.55 602.7°C-5.2Example 63Ba 3 W 1.1 V 0.9 O 8.55 653.1°C-4.9Example 63Ba 3 W 1.1 V 0.9 O 8.55 703.6°C-4.6Example 63Ba 3 W 1.1 V 0.9 O 8.55 754°C-4.2Example 63Ba 3 W 1.1 V 0.9 O 8.55 804.1°C-3.9Example 63Ba 3 W 1.1 V 0.9 O 8.55 854.5°C-3.5Example 63Ba 3 W 1.1 V 0.9 O 8.55 904.7°C-3.2Example 63Ba 3 W 1.1 V 0.9 O 8.55 955.1°C-2.9Example 63Ba 3 W 1.1 V 0.9 O 8.55 1005.2°C-2.6Example 64Ba 3 W 1.25 V 0.75 O 8.625 602.8°C-4.9Example 64Ba 3 W 1.25 V 0.75 O 8.625 653°C-4.5Example 64Ba 3 W 1.25 V 0.75 O 8.625 703.3°C-4.1Example 64Ba 3 W 1.25 V 0.75 O 8.625 753.9°C-3.8Example 64Ba 3 W 1.25 V 0.75 O 8.625 804.4°C-3.5Example 64Ba 3 W 1.25 V 0.75 O 8.625 854.6°C-3.2Example 64Ba 3 W 1.25 V 0.75 O 8.625 902.8°C-2.9Example 64Ba 3 W 1.25 V 0.75 O 8.625 952.5°C-2.7Example 64Ba 3 W 1.25 V 0.75 O 8.625 1004.3°C-2.4Example 65Ba 3 W 1.5 V 0.5 O 8.75 602.9°C-4.1Example 65Ba 3 W 1.5 V 0.5 O 8.75 653.1°C-3.8Example 65Ba 3 W 1.5 V 0.5 O 8.75 703.4°C-3.5Example 65Ba 3 W 1.5 V 0.5 O 8.75 753.9°C-3.2Example 65Ba 3 W 1.5 V 0.5 O 8.75 804.2°C-2.9Example 65Ba 3 W 1.5 V 0.5 O 8.75 854.4°C-2.7Example 65Ba 3 W 1.5 V 0.5 O 8.75 904.8°C-2.5Example 65Ba 3 W 1.5 V 0.5 O 8.75 955°C-2.3Example 65Ba 3 W 1.5 V 0.5 O 8.75 1005°C-2.1 [Table 29] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 602.6°C-3.5Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 653°C-3.2Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 703.3°C-2.9Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 753.7°C-2.7Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 804°C-2.4Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 854.1°C-2.2Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 904.5°C-2.0Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 954.9°C-1.9Test Example 66Ba 3 W 1.6 V 0.4 O 8.8 1004°C-1.7Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 602.55°C-4.7Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 652.35°C-4.4Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 702.85°C-4.1Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 753.15°C-3.9Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 803.65°C-3.6Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 854.05°C-3.4Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 904.25°C-3.2Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 954.35°C-2.9Test Example 67Ba 3 W 1.75 V 0.25 O 8.875 1004.65°C-2.8Test Example 68Ba 3 MoTiO 8 902.7°C-2.9Test Example 68Ba 3 MoTiO 8 854.4°C-3.0Test Example 68Ba 3 MoTiO 8 803.6°C-3.1Test Example 68Ba 3 MoTiO 8 753.2°C-3.4Test Example 68Ba 3 MoTiO 8 702.1°C-3.7Test Example 68Ba 3 MoTiO 8 651.4°C-4.0Test Example 68Ba 3 MoTiO 8 600.9°C-4.3Test Example 68Ba 3 MoTiO 8 549.9°C-4.7Test Example 68Ba 3 MoTiO 8 495.2°C-5.0Test Example 68Ba 3 MoTiO 8 450.2°C-5.5 [Table 30] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 904.2°C-2.2Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 853.6°C-2.2Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 802.9°C-2.3Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 752.6°C-2.5Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 701.7°C-2.6Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 651.5°C-2.8Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 601°C-3.0Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 550.4°C-3.3Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 449.5°C-3.8Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 395.5°C-4.3Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 347.5°C-4.7Test Example 69Ba 3 Mo 1.1 Ti 0.9 O 8.1 295.8°C-5.2Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 804.7°C-2.2Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 753.3°C-2.4Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 703.1°C-2.5Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 653°C-2.8Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 602.3°C-3.1Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 552.5°C-3.4Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 501.8°C-3.7Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 456.8°C-4.2Test Example 70Ba 3 Mo 1.2 Ti 0.8 O 8.2 419°C-4.5Test Example 71Ba 7 Ca 2 Mn 5 O 20 300.7°C-4.5Test Example 71Ba 7 Ca 2 Mn 5 O 20 401.2°C-3.7Test Example 71Ba 7 Ca 2 Mn 5 O 20 506.3°C-3.0Test Example 71Ba 7 Ca 2 Mn 5 O 20 603.6°C-2.4Test Example 71Ba 7 Ca 2 Mn 5 O 20 704.2°C-1.9Test Example 71Ba 7 Ca 2 Mn 5 O 20 804.9°C-1.4Test Example 71Ba 7 Ca 2 Mn 5 O 20 905.5°C-1.1Test Example 71Ba 7 Ca 2 Mn 5 O 20 1005.6°C-0.8Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 676°C-2Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 775°C-1.8Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 826°C-1.7Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 876°C-1.6Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 926°C-1.5Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 976°C-1.4Test Example 72Ba 2.6 Ca 1.4 La 4 Mn 4 O 19 1027°C-1.4 [Table 31] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 292.4°C-6.3Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 345.1°C-5.9Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 396.8°C-5.6Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 447.9°C-5.4Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 498.4°C-5.2Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 599.7°C-5.0Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 700.5°C-4.8Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 801.6°C-4.5Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 904.8°C-4.1Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 1001.1°C-3.7Test Example 74Ba 5 Gd 2 Al 2 ZrO 13 1170.3°C-3.0Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 299.9°C-3.4Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 350.5°C-3.2Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 401.3°C-3.1Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 452.1°C-3.1Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 504.3°C-3.1Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 604.9°C-3.2Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 704.9°C-3.2Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 804.9°C-3.2Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 905.2°C-3.2Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 1005.6°C-3.1Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 1105.5°C-3.0Test Example 75Ba 5 Dy 2 Al 2 ZrO 13 1204.9°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 299.2°C-3.5Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 352.4°C-3.1Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 403.9°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 453.9°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 503.8°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 505.8°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 554.2°C-2.9Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 604.5°C-3.0Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 705°C-3.0Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 805.3°C-3.0Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 905.6°C-2.9Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 1005.5°C-2.8Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 1105.3°C-2.7Test Example 76 (in air)Ba 5 Er 2 Al 2 ZrO 13 1204.8°C-2.6Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 317.8°C-4.6Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 404.7°C-4.2Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 508.2°C-4.1Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 600°C-4.0Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 702.9°C-3.9Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 805.7°C-3.8Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 1007.4°C-3.5Test Example 76 (in dry air)Ba 5 Er 2 Al 2 ZrO 13 1150.1°C-3.2Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 299.9°C-2.9Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 351.6°C-2.8Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 399.2°C-2.7Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 449.3°C-2.7Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 499.6°C-2.7Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 601.2°C-2.8Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 701.8°C-2.9Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 802.5°C-2.8Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 903.2°C-2.7Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 1003.7°C-2.6Test Example 77Ba 5 Ho 2 Al 2 ZrO 13 1203.9°C-2.4 [Table 32] CompositionTotal electrical conductivity (~ oxide ion conductivity) and measured temperatureTemperaturelog (σ total (S cm -1< ))Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 299°C-3.5Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 348.4°C-3.3Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 398.4°C-3.2Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 448.7°C-3.3Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 499.2°C-3.4Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 602.4°C-3.4Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 701.3°C-3.3Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 801.9°C-3.1Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 903.1°C-2.9Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 1039.8°C-2.6Test Example 78Ba 5 Tm 2 Al 2 ZrO 13 1206.5°C-2.4Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 304.1°C-3.3Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 404.3°C-2.9Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 503.7°C-2.8Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 604.2°C-2.8Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 704.9°C-2.9Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 804.5°C-2.8Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 904.9°C-2.7Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 1005.6°C-2.6Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 1105.1°C-2.5Test Example 79Ba 5 Yb 2 Al 2 ZrO 13 1204.6°C-2.4Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 305.7°C-5.0Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 354.3°C-4.5Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 403.4°C-4.1Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 452.9°C-3.9Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 502.1°C-3.9Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 603.6°C-3.9Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 705.4°C-3.8Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 804.6°C-3.7Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 904.8°C-3.6Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 1005.3°C-3.5Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 1105.3°C-3.3Test Example 80Ba 5 Lu 2 Al 2 ZrO 13 1204.3°C-3.0Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.075 355.85°C-3.7Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.076 405.85°C-3.3Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.077 454.85°C-3.0Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.078 504.85°C-2.7Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.079 554.85°C-2.5Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.080 604.85°C-2.3Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.081 654.85°C-2.1Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.082 704.85°C-2.0Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.083 755.85°C-1.9Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.084 805.85°C-1.8Test Example 82Ba 7 Nb 3.85 W 0.15 MoO 20.085 855.85°C-1.7Test Example 82Ba 7 Nb 3.85 W 0.13 MoO 20.086 905.85°C-1.6Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.125 355.85°C-4.0Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.126 405.85°C-3.7Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.127 454.85°C-3.3Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.128 504.85°C-3.1Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.129 554.85°C-2.8Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.130 604.85°C-2.6Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.131 654.85°C-2.4Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.132 704.85°C-2.3Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.133 755.85°C-2.2Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.134 805.85°C-2.1Test Example 83Ba 7 Nb 3.75 W 0.25 MoO 20.135 855.85°C-2.0

[0079] For all of Test Examples shown in Tables 16 to 32, the electrical conductivity represented by log [σ(Scm -1< )] in the temperature range of 280 to 909°C was within the range of -7.0 to -1.0. Among these, for example, Test Example 32 exhibited high electrical conductivity at a low temperature of -3.4 to -2.0 at 306 to 606°C.(Calculation example)

[0080] For Ba 7 Nb 4 MoO 20 , a structure in which a part of Nb was substituted with another element was designed, and the a-axis length, b-axis length, c-axis length (Å), α-angle, β-angle, and γ-angle (o) of the lattice constants were obtained by calculation. (Test Examples 84 to 152, Tables 33 to 36) [Table 33]CompositionLattice constanta[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]Test Example 84Ba 7 Nb 3 AgMoO 20 5.93995.939916.79299090120513.1154Test Example 85Ba 7 Nb 3 AlMoO 20 5.90045.900416.74329090120504.8147Test Example 86Ba 7 Nb 3 AtMoO 20 6.01056.010516.86069090120527.5049Test Example 87Ba 7 Nb 3 AuMoO 20 5.94055.940516.77679090120512.7134Test Example 88Ba 7 Nb 3 BeMoO 20 5.90435.904317.16739090120518.2808Test Example 89Ba 7 Nb 3 BiMoO 20 5.99205.992016.83629090120523.5022Test Example 90Ba 7 Nb 3 BrMoO 20 5.94495.944916.81079090120514.5259Test Example 91Ba 7 Nb 3 CaMoO 20 6.01376.013716.84629090120527.6174Test Example 92Ba 7 Nb 3 CdMoO 20 6.00446.004416.91549090120528.1425Test Example 93Ba 7 Nb 3 CeMoO 20 6.04946.049417.00419090120538.9045Test Example 94Ba 7 Nb 3 CoMoO 20 5.88165.881616.73779090120501.4317Test Example 95Ba 7 Nb 3 CrMoO 20 5.88355.883516.73839090120501.7814Test Example 96Ba 7 Nb 3 CuMoO 20 5.90625.906216.76199090120506.3652Test Example 97Ba 7 Nb 3 DyMoO 20 6.01396.013916.80209090120526.2740Test Example 98Ba 7 Nb 3 ErMoO 20 6.00516.005116.78189090120524.0937Test Example 99Ba 7 Nb 3 EuMoO 20 6.02746.027416.92159090120532.3955Test Example 100Ba 7 Nb 3 FeMoO 20 5.88335.883316.73509090120501.6530Test Example 101Ba 7 Nb 3 GaMoO 20 5.93375.933716.76419090120511.1718Test Example 102Ba 7 Nb 3 GdMoO 20 6.02336.023316.82529090120528.6394Test Example 103Ba 7 Nb 3 GeMoO 20 5.90235.902316.76879090120505.9081 [Table 34] CompositionLattice constanta[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]Test Example 104Ba 7 Nb 3 HgMoO 20 5.98745.987416.86419090120523.5637Test Example 105Ba 7 Nb 3 HoMoO 20 6.00936.009316.79069090120525.1054Test Example 106Ba 7 Nb 3 IMoO 20 5.98935.989316.82449090120522.6582Test Example 107Ba 7 Nb 3 InMoO 20 5.99355.993516.82349090120523.3607Test Example 108Ba 7 Nb 3 IrMoO 20 5.92105.921016.77649090120509.3578Test Example 109Ba 7 Nb 3 LaMoO 20 6.04756.047516.97859090120537.7646Test Example 110Ba 7 Nb 3 LiMoO 20 5.97355.973516.84869090120520.6503Test Example 111Ba 7 Nb 3 LuMoO 20 5.99265.992616.76089090120521.2621Test Example 112Ba 7 Nb 3 MgMoO 20 5.96225.962216.77019090120516.2773Test Example 113Ba 7 Nb 3 MnMoO 20 5.88565.885616.74699090120502.3922Test Example 114Ba 7 Nb 3 NaMoO 20 5.96905.969016.79109090120518.0919Test Example 115Ba 7 Nb 3 NbMoO 20 5.98805.988016.89809090120524.7378Test Example 116Ba 7 Nb 3 NdMoO 20 6.04216.042116.91819090120534.8888Test Example 117Ba 7 Nb 3 NiMoO 20 5.88555.885516.74369090120502.2851Test Example 118Ba 7 Nb 3 NpMoO 20 6.00646.006416.82189090120525.5746Test Example 119Ba 7 Nb 3 OsMoO 20 5.92445.924416.76509090120509.6000Test Example 120Ba 7 Nb 3 PMoO 20 5.84115.841116.71309090120493.8210Test Example 121Ba 7 Nb 3 PbMoO 20 6.00626.006216.85589090120526.6073Test Example 122Ba 7 Nb 3 PdMoO 20 5.92405.924016.77839090120509.9204Test Example 123Ba 7 Nb 3 PoMoO 20 6.00706.007016.86719090120527.0855 [Table 35] CompositionLattice constanta[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]Test Example 124Ba 7 Nb 3 PrMoO 20 6.04586.045816.95209090120536.6149Test Example 125Ba 7 Nb 3 PtMoO 20 5.92525.925216.77989090120510.1879Test Example 126Ba 7 Nb 3 PuMoO 20 6.00426.004216.82709090120525.3532Test Example 127Ba 7 Nb 3 ReMoO 20 5.92475.924716.76579090120509.6719Test Example 128Ba 7 Nb 3 RhMoO 20 5.91525.915216.78019090120508.4750Test Example 129Ba 7 Nb 3 RuMoO 20 5.91795.917916.76829090120508.5669Test Example 130Ba 7 Nb 3 SMoO 20 5.99325.993217.06279090120530.7513Test Example 131Ba 7 Nb 3 SbMoO 20 5.94565.945616.78849090120513.9662Test Example 132Ba 7 Nb 3 ScMoO 20 5.97175.971716.78539090120518.3833Test Example 133Ba 7 Nb 3 SeMoO 20 5.92655.926516.79739090120510.9378Test Example 134Ba 7 Nb 3 SiMoO 20 5.86045.860416.71149090120497.0433Test Example 135Ba 7 Nb 3 SmMoO 20 6.03386.033816.86519090120531.7507Test Example 136Ba 7 Nb 3 SnMoO 20 5.96695.966916.78609090120517.5743Test Example 137Ba 7 Nb 3 SrMoO 20 6.04206.042017.04979090120539.0294Test Example 138Ba 7 Nb 3 TaMoO 20 5.94045.940416.79219090120513.1733Test Example 139Ba 7 Nb 3 TbMoO 20 6.03356.033516.89769090120532.7175Test Example 140Ba 7 Nb 3 TcMoO 20 5.91695.916916.76329090120508.2433Test Example 141Ba 7 Nb 3 TeMoO 20 5.97655.976516.80429090120519.8019Test Example 142Ba 7 Nb 3 TiMoO 20 5.92105.921016.76649090120509.0554 [Table 36] CompositionLattice constanta[Å]b[Å]c[Å]α[°]β[°]γ[°]V[Å 3< ]Test Example 143Ba 7 Nb 3 TiMoO 20 6.01486.014816.91549090120529.9799Test Example 144Ba 7 Nb 3 TmMoO 20 6.00106.001016.77549090120523.1813Test Example 145Ba 7 Nb 3 UMoO 20 6.00766.007616.82619090120525.9239Test Example 146Ba 7 Nb 3 VMoO 20 5.89235.892316.75039090120503.6431Test Example 147Ba 7 Nb 3 WMoO 20 5.86445.864416.75129090120503.6431Test Example 148Ba 7 Nb 3 XeMoO 20 6.06886.068816.74279090120534.0269Test Example 149Ba 7 Nb 3 YbMoO 20 6.00376.003716.82619090120525.2420Test Example 150Ba 7 Nb 3 ZnMoO 20 5.95525.955216.78499090120515.5207Test Example 151Ba 7 Nb 3 ZrMoO 20 5.97825.978516.79349090120519.7711Test Example 152Ba 7 Nb 3 YMoO 20 5.99855.998516.79349090120523.3099

[0081] According to the calculation examples, the optimized structures of the compounds having the compositions of Test Examples 84 to 152 retain the crystal structure of the original hexagonal perovskite-related compounds, indicating the possibility that these compositions can be synthesized. Similar to Test Examples 1 to 83, it is considered that these compositions also exhibit excellent characteristics in, for example, electrical conductivity at a low temperature when used in a solid electrolyte.[Industrial Applicability]

[0082] According to the solid electrolyte, and the electrolyte layer and battery using the solid electrolyte of the present invention, a solid electrolyte having high electrical conductivity even in a low-temperature region, an electrolyte layer, and a battery using the solid electrolyte can be obtained. The solid electrolyte according to the present invention can also be used in a solid oxide fuel cell, a sensor, a battery, an electrode, an electrolyte, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, an oxygen pump, a catalyst, a photocatalyst, an electric / electronic / communication device, an energy / environment-related device, an optical device or the like.

Claims

1. A solid electrolyte comprising a hexagonal perovskite-related compound, wherein the compound is a compound represented by any of the following general formulas (3) to (7), (11) and (13):         Ba7Nb(4-x)Mo(1+x)O(20+z)     (3) , [in the formula (3), x represents a value of -1.1 or more and -0.01 or less or 0.01 or more and 1.1 or less, and z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less];         Ba7Nb(4-y)MoMyO(20+z)     (4) , [in the formula (4), M is a cation of at least one element selected from the group consisting of V, Mn, Ge, Si, and Zr; and y represents a value of 0.01 or more and 1.1 or less, and z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less];         Ba7Nb4Mo(1-y)MyO(20+z)     (5) , [in the formula (5), M is a cation of at least one element selected from the group consisting of V and Mn; and z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba7Nb(4-y)MoCryO(20+z)     (6) , [in the formula (6), z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba7Nb(4-y)MoWyO(20+z)     (7) , [in the formula (7), z is an oxygen non-stoichiometry and represents a value of -2.0 or more and 2.0 or less, and y represents a value of 0.01 or more and 1.1 or less];         Ba2.6Ca2.4La4Mn4O(19+z)     (11) .., [in the formula (11), z is an oxygen non-stoichiometry and represents a value of -1.0 or more and 1.0 or less]; and         Ba5M2Al2ZrO(13+z)     (13) , [in the formula (13), M represents any of Gd, Dy, Ho, Er, Tm, Yb, or Lu; and z is an oxygen non-stoichiometry and represents a value of -1.0 or more and 1.0 or less] , and wherein the hexagonal perovskite-related compound in the present embodiment is a compound having a layered structure containing a hexagonal perovskite unit.

2. The solid electrolyte according to Claim 1, wherein the compound is a compound represented by the general formula (3), and x is 0.06 or more and 0.30 or less.

3. The solid electrolyte according to Claim 2, wherein x is 0.19 or more and 0.21 or less.

4. The solid electrolyte according to Claim 3, wherein in the compound, an a-axis length, a b-axis length, a c-axis length (Å), an α-angle, a β-angle, and a γ-angle (o) of a lattice constant are in the numerical range of 5.35 < a < 6.56, 5.35 < b < 6.56, 15.14 < c < 18.52, 89 < α < 91, 89 < β < 91, and 119 < γ < 121, for the formulas (3) to (7), 5.23 < a < 6.4, 5.23 < b < 6.4, 18.96 < c < 23.19, 89 < α < 91, 89 < β < 91, and 119 < γ < 121, for for the formula (11), 5.05 < a < 6.19, 5.05 < b < 6.19, 15.57 < c < 19.03, 89 < α < 91, 89 < β < 91, and 119 < γ < 121, for the formula (13), respectively.

5. A use of the solid electrolyte according to any one of Claims 1 to 4, used as an oxide ion (O2-) conductor and used under a temperature condition of 300 to 1200°C.

6. The solid electrolyte according to any one of Claims 1 to 4, wherein the solid electrolyte has an electrical conductivity represented by log [σ(Scm-1)] of -7 or more when measured at 300°C.

7. A use of the solid electrolyte according to any one of Claims 1 to 4 or 6, or the use according to Claim 5, used for a solid oxide fuel cell (SOFC), a sensor, a battery, an electrode, an electrolyte, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, an oxygen pump, a catalyst, a photocatalyst, an electric / electronic / communication device, an energy / environment-related device, or an optical device.

8. A use of the solid electrolyte according to any one of Claims 1 to 4 or 6, or the use according to Claims 5 or 7,used for an electrolyte layer used in a solid oxide fuel cell (SOFC), a sensor, an oxygen concentrator, an oxygen separation membrane, an oxygen permeation membrane, or an oxygen pump.

9. An electrolyte layer comprising the solid electrolyte according to any one of Claims 1 to 8.

10. A battery comprising the electrolyte layer containing the solid electrolyte according to Claim 9.

11. The battery according to Claim 10, wherein the battery is a solid oxide fuel cell (SOFC).