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OXYGEN ION TRANSPORT MATERIALS AND RELATED DEVICES

20240270597 ยท 2024-08-15

    Inventors

    Cpc classification

    International classification

    Abstract

    Devices are provided, which in embodiments, comprise a source configured to generate oxygen ions via a redox reaction; and an oxygen ion transport material through which oxygen ions generated from the source are transported. The oxygen ion transport material may have either: Formula I A.sup.x+B.sub.2.sup.y+C.sub.4.sup.z+O.sub.12 .sup.2? wherein x+2y+4z=24 and (x, y, z) is (4, 2, 4), (x, y, z) is (2, 1, 5), or (x, y, z) is (3, 2.5, 4); Formula II A.sub.4.sup.x+B.sub.5.sup.y+C.sub.4.sup.z+O.sub.22.sup.2? wherein 4x+5y+4z=44 and (x, y, z) is (2, 4, 4) or (x, y, z) is (3, 3.2, 4) or (x, y, z) is (2.5, 3.6, 4); or Formula III Bi.sub.2MO.sub.4X; wherein A, B, and C are independently selected from alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, lanthanoids, P, Th, and combinations thereof, and wherein M is selected from rare earth elements and combinations thereof and X is selected from halogens and combinations thereof. Methods of using the devices are also provided, which in embodiments, which comprise transporting oxygen ions generated from the source through the oxygen ion transport material.

    Claims

    1. A device comprising: a source configured to generate oxygen ions via a redox reaction; and an oxygen ion transport material through which oxygen ions generated from the source are transported, the oxygen ion transport material having either: Formula I A.sup.x+B.sub.2.sup.y+C.sub.4.sup.z+O.sub.12.sup.2?wherein x+2y+4z=24 and (x, y, z) is (4, 2, 4), (x, y, z) is (2, 1, 5), or (x, y, z) is (3, 2.5, 4); Formula II A.sub.4.sup.x+B.sub.5.sup.y+C.sub.4.sup.z+O.sub.22.sup.2? wherein 4x+5y+4z=44 and (x, y, z) is (2, 4, 4) or (x, y, z) is (3, 3.2, 4) or (x, y, z) is (2.5,3.6, 4); or Formula III Bi.sub.2MO.sub.4X; wherein A, B, and C are independently selected from alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, lanthanoids, P, Th, and combinations thereof, and wherein M is selected from rare earth elements and combinations thereof and X is selected from halogens and combinations thereof.

    2. The device of claim 1, wherein the oxygen ion transport material has Formula II wherein (x, y, z) is (3, 3.2, 4).

    3. The device of claim 2, wherein A is selected from Al, Ga, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof; B is selected from Mn, Ti, Zr, Hf, V, Fe, Co, Cr, Ru, Ir and a combination of at least one of Fe, Co, Ni, Mg, Ca, Zn, Cu, Mn and at least one of Fe, Co, Ni, Mn, Al, Ga, Ti, Zr, Hf, Cr, Ru, Ir, Ge, V, Nb, W; and C is selected from Si, Ge, Sn, and combinations thereof.

    4. The device of claim 2, wherein A is selected from La, Pr, Nd, Sm, Ce, and combinations thereof; B is selected from Mn, V, Ti, Zn, Fe, Co, Ni, Al, Nb, Mg, Cr, and combinations thereof; and C is Si.

    5. The device of claim 2, wherein A is selected from La, Nd, and combinations thereof; B is selected from Mn, V, Ti, and combinations thereof; and C is Si.

    6. The device of claim 2, wherein the oxygen ion transport material is La.sub.4Mn.sub.5Si.sub.4O.sub.22; La.sub.4Ti.sub.5Si.sub.4O.sub.22; A.sub.4(V, Zn).sub.5Si.sub.4O.sub.22 wherein A is La, Pr, Nd, or Ce; A.sub.4(Mg.sub.2Ti.sub.3)Si.sub.4O.sub.22 wherein A is La, Pr, Nd, or Sm; A.sub.4(Fe.sub.2Ti.sub.3)Si.sub.4O.sub.22 wherein A is La, Nd, or (Ce, La); A(Ni.sub.2Ti.sub.3)Si.sub.4O.sub.22 wherein A is La.sub.4, La.sub.2Pr.sub.2, LaPr.sub.3, La.sub.0.6Pr.sub.3.4, La.sub.2Nd.sub.2, Pr.sub.4, Nd.sub.4, Sm.sub.4, Sm.sub.2Nd.sub.2, or Ce.sub.4; A(Co.sub.2Ti.sub.3)Si.sub.4O.sub.22 wherein A is La.sub.4, La.sub.3.4Pr.sub.0.6, La.sub.3Pr, La.sub.2.6Pr.sub.1.4, La.sub.2Pr.sub.2, Pr.sub.4, Nd.sub.4, Sm.sub.4, Sm.sub.2Nd.sub.2, Ce.sub.4, Ce.sub.2La.sub.2, or CeLa.sub.5; La.sub.4Mn.sub.3Ge.sub.5.2Si.sub.0.8O.sub.22; La.sub.4(FeCoTi.sub.3)Si.sub.4O.sub.22; A(NiCoTi.sub.3) Si.sub.4O.sub.22 wherein A is La.sub.3Pr, La.sub.1.3Pr.sub.2.7, La.sub.2Pr.sub.2, or Sm.sub.2Nd.sub.2; A.sub.4(FeAl.sub.2Ti.sub.2)Si.sub.4O.sub.22 wherein A is Pr, Nd, or Ce; Ce.sub.4BSi.sub.4O.sub.22 wherein B is MgFe.sub.2Ti.sub.2, MgCr.sub.2Ti.sub.2, FeTi.sub.4, Fe(Ti, Fe).sub.4, or Fe.sub.1.5AlTi.sub.2.5; Ce, La).sub.4(Fe (Ti, Fe, Mn).sub.2Ti.sub.2)Si.sub.4O.sub.22; (Ce, La).sub.4(Fe (Ti, Fe, Mn).sub.2Ti.sub.2)Si.sub.4O.sub.22; or a combination thereof.

    7. The device of claim 2, wherein the oxygen ion transport material is La.sub.4Mn.sub.5Si.sub.4O.sub.22; La.sub.4Ti.sub.5Si.sub.4O.sub.22; La.sub.4V.sub.5Si.sub.4O.sub.22; Nd.sub.4V.sub.5Si.sub.4O.sub.22; or a combination thereof.

    8. The device of claim 1, wherein the oxygen ion transport material has Formula I wherein (x, y, z) is (4, 2, 4).

    9. The device of claim 8, wherein A is selected from Ti, Zr, Hf, Ce, Re, Ir, and combinations thereof; B is selected from Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, and combinations thereof; and C is selected from Si, Ge, Sn, and combinations thereof.

    10. The device of claim 8, wherein A is selected from Zr, Ce, and combinations thereof; B is selected from Mn, Co, Ni, Cu, and combinations thereof; and C is Ge.

    11. The device of claim 8, wherein A is selected from Zr, Ce, and combinations thereof; B is selected from Mn, Co, and combinations thereof; and C is Ge.

    12. The device of claim 8, wherein the oxygen ion transport material is Ce(Mn.sub.xCo.sub.2-x)Ge.sub.4O.sub.12 (x=0, 0.5, 1, 1.5, 2); Zr(Mn.sub.xCo.sub.2-x)Ge.sub.4O.sub.12 (x=0, 0.5, 1, 1.5, 2); Ce(Mn.sub.1.5Ni.sub.0.5)Ge.sub.4O.sub.12; Ce(Mn.sub.1.5Cu.sub.0.5)Ge.sub.4O.sub.12; Ce(Co.sub.1.5Ni.sub.0.5)Ge.sub.4O.sub.12; Ce(Co.sub.1.5Cu.sub.0.5)Ge.sub.4O.sub.12; or a combination thereof.

    13. The device of claim 8, wherein the oxygen ion transport material is ZrMn.sub.2Ge.sub.4O.sub.12; CeMn.sub.2Ge.sub.4O.sub.12; ZrCo.sub.2Ge.sub.4O.sub.12; CeCo.sub.2Ge.sub.4O.sub.12; or a combination thereof.

    14. The device of claim 1, wherein the oxygen ion transport material has Formula I wherein (x, y, z) is (3, 2.5, 4).

    15. The device of claim 14, wherein A is selected from Al, Ga, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof; B is selected from a combination of at least one A-site element and at least one of Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn; and a combination of at least two of Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn; and C is selected from Si, Ge, Sn, and combinations thereof.

    16. The device of claim 14, wherein A is selected from Y, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Tb, Ce, Pr, and combinations thereof; B is selected from a combination of at least one A-site element and at least one of Ca, Mn, Co; and a combination of at least two of Ca, Mn, Fe, Co, Cu, Sc, Zn; and C is Ge.

    17. The device of claim 14, wherein the oxygen ion transport material is Y(YMn)Ge.sub.4O.sub.12; Y(YCo)Ge.sub.4O.sub.12; or a combination thereof.

    18. The device of claim 1, wherein the oxygen ion transport material is La.sub.4Mn.sub.5Si.sub.4O.sub.22; LaTi.sub.5Si.sub.4O.sub.22; La.sub.4V.sub.5Si.sub.4O.sub.22; Nd.sub.4V.sub.5Si.sub.4O.sub.22; ZrMn.sub.2Ge.sub.4O.sub.12; CeMn.sub.2Ge.sub.4O.sub.12; ZrCo.sub.2Ge.sub.4O.sub.12; CeCo.sub.2Ge.sub.4O.sub.12; Y(YMn)Ge.sub.4O.sub.12; Y(YCo)Ge.sub.4O.sub.12; or a combination thereof.

    19. The device of claim 1, wherein the oxygen ion transport material is La.sub.4Mn.sub.5Si.sub.4O.sub.22; ZrMn.sub.2Ge.sub.4O.sub.12; or a combination thereof.

    20. The device of claim 1, wherein the device comprises an electrode, a counter electrode in electrical communication with electrode, and an electrolyte or a membrane between the electrode and the counter electrode, wherein the source is the electrode.

    21. The device of claim 20, wherein the electrolyte, the electrode, or the membrane comprises the oxygen ion transport material.

    22. The device of claim 20, wherein the device is a fuel cell, a gas sensor, or a separation system.

    23. A method of using the device of claim 1, the method comprising transporting oxygen ions generated from the source through the oxygen ion transport material.

    24. The method of claim 23. further comprising generating the oxygen ions via the redox reaction.

    Description

    BRIEF DESCRIPTION OF THE DRAWINGS

    [0008] Illustrative embodiments of the disclosure will hereafter be described with reference to the accompanying drawings.

    [0009] FIGS. 1A-1B depict the bulk structure of ZrMn.sub.2Ge.sub.4O.sub.12 viewed from (FIG. 1A) and (FIG. 1B) [001].

    [0010] FIG. 2 depicts the bulk structure of La.sub.4Mn.sub.5Si.sub.4O.sub.22. The black box denotes a single unit cell, and four unit cells are shown to aid visibility of the structure.

    [0011] FIGS. 3A-3D demonstrate oxygen ion migration through ZrMn.sub.2Ge+O.sub.12 (FIG. 3A) and La.sub.430 Mn.sub.5Si.sub.4O.sub.22 (FIG. 3C). The migration pathway is marked by arrows. The initial and final sites of the oxygen interstitial are labeled in FIGS. 3A and 3C. The lattice oxygen participating in the migration pathway are labeled in FIG. 3A. FIGS. 3B and 3D show the nudged elastic band (NEB) calculated energy profile along the migration pathway of oxygen ion in ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22, respectively.

    [0012] FIGS. 4A-4B show Arrhenius plot of oxygen ion diffusivity versus the reciprocal of the temperature in (FIG. 4A) ZrMn.sub.2Ge.sub.4O.sub.12 and (FIG. 4B) La.sub.4Mn.sub.5Si.sub.4O.sub.22 from ab initio molecular dynamics (AIMD) simulations.

    [0013] FIG. 5 depicts a schematic of a fuel cell comprising an oxygen ion transport material according to an illustrative embodiment.

    [0014] FIG. 6 depicts a schematic of a metal-air battery comprising an oxygen ion transport material according to an illustrative embodiment.

    [0015] FIG. 7 depicts a schematic of a gas sensor comprising an oxygen ion transport material according to an illustrative embodiment.

    [0016] FIG. 8 depicts a schematic of a separation system comprising an oxygen ion transport material according to an illustrative embodiment.

    [0017] FIG. 9 depicts a schematic of a supercapacitor comprising an oxygen ion transport material according to an illustrative embodiment.

    [0018] FIG. 10 depicts a schematic of a steam reactor for carrying out solid oxide electrolysis comprising an oxygen ion transport material according to an illustrative embodiment.

    [0019] FIGS. 11A-11B depict the bulk structure of Bi.sub.2LaO.sub.4Cl from side (FIG. 11A) and top (FIG. 11B) view.

    [0020] FIG. 12A demonstrates oxygen ion migration through Bi.sub.2LaO.sub.4Cl. The migration pathway is marked by arrows. The initial and final sites of the oxygen are labeled in FIG. 12A. FIG. 12B shows the nudged elastic band (NEB) calculated energy profile along the migration pathway of oxygen ion in Bi.sub.2LaO.sub.4Cl.

    [0021] FIG. 13 shows Arrhenius plot of oxygen ion diffusivity versus the reciprocal of the temperature in Bi.sub.2LaO.sub.4Cl from ab initio molecular dynamics (AIMD) simulations with 2.78% of oxygen sites vacant in the cell.

    [0022] FIGS. 14A-14C show the X-ray powder diffraction patterns of ZrMn.sub.2Ge.sub.4O.sub.12 (FIG. 14A), La.sub.4Mn.sub.5Si.sub.4O.sub.22 (FIG. 14B), and Bi.sub.2LaO.sub.4Cl (FIG. 14C).

    [0023] FIGS. 15A-15B show the electrical conductivity transient of the ZrMn.sub.2Ge.sub.4O.sub.12 pellet as the oxygen partial pressure goes from 5% to 20% atm (FIG. 15A) and from 20% to 5% atm (FIG. 15B) at a temperature of 775? C.

    [0024] FIGS. 16A-16B shows the electrical conductivity transient of the La.sub.4Mn.sub.5Si.sub.4O.sub.22 pellet as the oxygen partial pressure goes from 5% to 20% atm (FIG. 16A) and from 20% to 5% atm (FIG. 16B) at a temperature of 800? C.

    [0025] FIGS. 17A-17B shows the electrical conductivity transient of the Bi.sub.2LaO.sub.4Cl pellet as the oxygen partial pressure goes from 10% to 20% atm (FIG. 17A) and from 20% to 10% atm (FIG. 17B) at a temperature of 600? C.

    [0026] FIGS. 18A-18B show the fitting of the normalized electrical conductivity relaxation curve of ZrMn.sub.2Ge.sub.4O.sub.12 with oxygen partial pressure changing from 5% to 20% at 750? C. (FIG. 18A) and the fitting of the normalized electrical conductivity relaxation curve of La.sub.4Mn.sub.5Si.sub.4O.sub.22 with oxygen partial pressure changing from 5% to 20% at 800? C. (FIG. 18B).

    DETAILED DESCRIPTION

    [0027] Provided are oxygen ion transport materials, devices comprising the materials, and methods of using the materials and devices.

    AB.sub.2C.sub.4O.sub.12 Materials

    [0028] Embodiments of the oxygen ion transport materials have Formula I A.sup.x+B.sub.2.sup.y+C.sub.4.sup.z+O.sub.12.sup.2? wherein x+2y+4z=24. The labels A, B, and C, represent distinct lattice sites in the material which are occupied by various elements. The A-site elements, B-site elements, and C-site elements are selected to satisfy the valence equation x+2y+4z=24. In embodiments, the valence configuration (x, y, z) is (4, 2, 4), i.e. A.sup.4+B.sub.2.sup.2+C.sub.4.sup.4+O.sub.12.sup.2? (Formula IA). In embodiments, the valence configuration (x, y, z) is (2, 1, 5), i.e., A.sup.2+B.sub.2.sup.1+C.sub.4.sup.5+O.sub.12.sup.2? (Formula IB). In embodiments, the valence configuration (x, y, z) is (3, 2.5, 4), i.e., A.sup.3+B.sub.2.sup.2.5+C.sub.4.sup.4+O.sub.12.sup.2? (Formula IC). In general, the A-site, B-site, and C-site elements may be selected from alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, and lanthanoids. In embodiments, a reactive non-metal such as P may be used, e.g., for a C-site element. Unless otherwise stated, more than one type of element may be present on a particular site. This includes, e.g., having 2, 3, 4, 5, 6, 7, etc. different types of elements on the A-site, the B-site, the C-site, or combinations thereof.

    [0029] In embodiments, a single type of element is present on the A-site, one or two types of elements are present on the B-site, and a single type of element is present on the C-site. In embodiments, a single type of element is present on the A-site, a single type of element is present on the B-site, and a single type of element is present on the C-site.

    [0030] Table 1, below, includes embodiments of oxygen ion transport materials having Formulas IA, IB, or IC which may be used. In embodiments, the oxygen ion transport material has Formula IA, wherein A is selected from Ti, Zr, Hf, Ce, Re, Ir, and combinations thereof; B is selected from Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, and combinations thereof; and C is selected from Si, Ge, Sn, and combinations thereof. In embodiments, the oxygen ion transport material has Formula IB, wherein A is selected from Mg, Ca, Sr, Ba, Cu, Zn, and combinations thereof; B is selected from Li, Na, K, Rb, Cs, Ag, and combinations thereof; and C is selected from V, Nb, Ta, P, As, Sb, and combinations thereof. In embodiments, the oxygen ion transport material has Formula IC, wherein A is selected from Al, Ga, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof; B is selected from a combination of at least one A-site element and at least one of Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, and Zn; and a combination of at least two of Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn; and C is selected from Si, Ge, Sn, and combinations thereof.

    TABLE-US-00001 TABLE 1 Embodiments of oxygen ion transport materials having Formula IA, IB, or IC. Material A-site elements B-site elements C-site elements A.sup.4+B.sub.2.sup.2+C.sub.4.sup.4+O.sub.12.sup.2? Ti, Zr, Hf, Ce, Re, Mg, Ca, Sr, Ba, Mn, Si, Ge, Sn (Formula IA) Ir Fe, Co, Ni, Cu A.sup.2+B.sub.2.sup.1+C.sub.4.sup.5+O.sub.12.sup.2? Mg, Ca, Sr, Ba, Li, Na, K, Rb, Cs, Ag V, Nb, Ta, P, As, (Formula IB) Cu, Zn Sb A.sup.3+B.sub.2.sup.2.5+C.sub.4.sup.4+O.sub.12.sup.2? Al, Ga, Sc, Y, La, An element in A-site Si, Ge, Sn (Formula IC) Ce, Pr, Nd, Sm, column + one of Mg, Eu, Gd, Tb, Dy, Ca, Sr, Ba, Mn, Fe, Co, Ho, Er, Tm, Yb, Ni, Cu, Zn; or two of Lu Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn

    [0031] In embodiments, the oxygen ion transport material has Formula IA, wherein A is selected from Zr, Ce, and combinations thereof; B is selected from Mn, Co, Ni, Cu, and combinations thereof; and C is Ge. In embodiments, the oxygen ion transport material has Formula IA, wherein A is selected from Zr, Ce, and combinations thereof; B is selected from Mn, Co, and combinations thereof; and C is Ge. In embodiments, the oxygen ion transport material has Formula IB, wherein A is selected from Ca, Sr, and combinations thereof; B is selected from Na, K, Rb, Cs, Ag, and combinations thereof; and C is selected from V, P, As, and combinations thereof. In embodiments, the oxygen ion transport material has Formula IC, wherein A is selected from Y, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Tb, Ce, Pr, and combinations thereof; B is selected from a combination of at least one A-site element and at least one of Ca, Mn, and Co; and a combination of at least two of Ca, Mn, Fe, Co, Cu, Sc and Zn; and C is Ge. An illustrative list of such species is shown in Table 2, below. The materials of Table 2 have been experimentally synthesized and confirmed to share similar crystal structure (although not necessarily same space group) as ZrMn.sub.2Ge.sub.4O.sub.12 (see FIGS. 1A and 1B).

    TABLE-US-00002 TABLE 2 Additional embodiments of oxygen ion transport materials having Formula IA, IB, or IC. Formula IA (A.sup.4+B.sub.2.sup.2+C.sub.4.sup.4+O.sub.12.sup.2?) Ce(Mn.sub.xCo.sub.2?x)Ge.sub.4O.sub.12(x = 0, 0.5, 1, 1.5, 2) Zr(Mn.sub.xCo.sub.2?x)Ge.sub.4O.sub.12 (x = 0, 0.5, 1, 1.5, 2) Ce(Mn.sub.1.5Ni.sub.0.5)Ge.sub.4O.sub.12 Ce(Mn.sub.1.5Cu.sub.0.5)Ge.sub.4O.sub.12 Ce(Co.sub.1.5Ni.sub.0.5)Ge.sub.4O.sub.12 Ce(Co.sub.1.5Cu.sub.0.5)Ge.sub.4O.sub.12 Formula IB (A.sup.2+B.sub.2.sup.1+C.sub.4.sup.5+O.sub.12.sup.2?) CaNa.sub.2As.sub.4O.sub.12 CaAg.sub.2V.sub.4O.sub.12 CaNa.sub.2V.sub.4O.sub.12 SrAg.sub.2V.sub.4O.sub.12 SrNa.sub.2V.sub.4O.sub.12 SrK.sub.2V.sub.4O.sub.12 SrRb.sub.2V.sub.4O.sub.12 SrNa.sub.2P.sub.4O.sub.12 CaNa.sub.2P.sub.4O.sub.12 SrCs.sub.2V.sub.4O.sub.12 Formula IC (A.sup.3+B.sub.2.sup.2.5+C.sub.4.sup.4+O.sub.12.sup.2?) Er(FeCu)Ge.sub.4O.sub.12 Eu(EuMn)Ge.sub.4O.sub.12 Gd(GdMn)Ge.sub.4O.sub.12 Dy(DyMn)Ge.sub.4O.sub.12 Ho(HoMn)Ge.sub.4O.sub.12 Er(ErMn)Ge.sub.4O.sub.12 Tm(TmMn)Ge.sub.4O.sub.12 Yb(YbMn)Ge.sub.4O.sub.12 Lu(LuMn)Ge.sub.4O.sub.12 Y(YMn)Ge.sub.4O.sub.12 Gd(GdCo)Ge.sub.4O.sub.12 Tb(TbCo)Ge.sub.4O.sub.12 Dy(DyCo)Ge.sub.4O.sub.12 Ho(HoCo)Ge.sub.4O.sub.12 Er(ErCo)Ge.sub.4O.sub.12 Gd(LuCo)Ge.sub.4O.sub.12 Gd(ScCo)Ge.sub.4O.sub.12 Tb(ScCo)Ge.sub.4O.sub.12 Dy(ScCo)Ge.sub.4O.sub.12 Y(YCo)Ge.sub.4O.sub.12 Eu(EuCa)Ge.sub.4O.sub.12 Gd(GdCa)Ge.sub.4O.sub.12 Dy(DyCa)Ge.sub.4O.sub.12 Ho(HoCa)Ge.sub.4O.sub.12 Er(ErCa)Ge.sub.4O.sub.12 Tm(TmCa)Ge.sub.4O.sub.12 Yb(YbCa)Ge.sub.4O.sub.12 Lu(LuCa)Ge.sub.4O.sub.12 Y(YCa)Ge.sub.4O.sub.12 Gd(FeZn)Ge.sub.4O.sub.12 Y(MnFe)Ge.sub.4O.sub.12 Eu(MnFe)Ge.sub.4O.sub.12 Lu(MnFe)Ge.sub.4O.sub.12 Y.sub.2?xEr.sub.xCaGe.sub.4O.sub.12 (x = 0-2) Y.sub.2?2xCe.sub.xCa.sub.1+xGe.sub.4O.sub.12 (x = 0-1) Y.sub.2?xPr.sub.xMnGe.sub.4O.sub.12 (x = 0-0.5) Y(YCa.sub.1?xMn.sub.x)Ge.sub.4O.sub.12 (x = 0-1) Y(YCa.sub.1?xZn.sub.x)Ge.sub.4O.sub.12 (x = 0-1) Y(YCo.sub.1?xCa.sub.x)Ge.sub.4O.sub.12 (x = 0.25, 0.5)
    A.sub.4B.sub.5C.sub.4O.sub.22 Perrierite-Group and Chevkinite-Group Materials

    [0032] Embodiments of the oxygen ion transport materials have Formula II A.sub.4.sup.x+B.sub.5.sup.y+C.sub.4.sup.z+O.sub.22.sup.2? wherein 4x +5y+4z=44. As noted above, the labels A, B, and C represent distinct lattice sites in the material occupied by various elements. Here, however, the A-site elements, B-site elements, and C-site elements are selected to satisfy the valence equation 4x+5y+4z=44. In embodiments, the valence configuration (x, y, z) is (2, 4, 4), i.e. A.sub.4.sup.2+B.sub.5.sup.4+C.sub.4.sup.4+O.sub.22.sup.2? (Formula IIA). In embodiments, the valence configuration (x, y, z) is (3, 3.2, 4), i.e., A.sub.4.sup.3+B.sub.5.sup.3.2+C.sub.4.sup.4+O.sub.22.sup.2 (Formula IIB). In embodiments, the valence configuration can be fractional due to the compositional variation on each site, for example (x, y, z) is (2.5, 3.6, 4), i.e., A.sub.4.sup.2.5+B.sub.5.sup.3.6+C.sub.4.sup.4+O.sub.22.sup.2? (Formula IIC). In general, the A-site, B-site, and C-site elements may be selected from alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, and lanthanoids. In embodiments, an actinide such as Th may be used, e.g., for an A-site element. Unless otherwise stated, more than one type of element may be present on a particular site. This includes, e.g., having 2, 3, 4, 5, 6, 7, etc. different types of elements on the A-site, the B-site, the C-site, or combinations thereof.

    [0033] In embodiments, a single type of element is present on the A-site, two or three types of elements are present on the B-site, and a single type of element is present on the C-site. In embodiments, two types of elements are present on the A-site, two to five types of elements are present on the B-site, and a single type of element is present on the C-site. In embodiments, a single type of element is present on the A-site, a single type of element is present on the B-site, and a single type of element is present on the C-site.

    [0034] Table 3, below, includes embodiments of oxygen ion transport materials having Formulas IIA, IIB, or IIC which may be used. In embodiments, the oxygen ion transport material has Formula IIA, wherein A is selected from Mg, Ca, Sr, Ba, Cu, Zn, and combinations thereof; B is selected from Ti, Zr, Hf, Ce, Re, Ir, and combinations thereof; and C is selected from Si, Ge, Sn, and combinations thereof. In embodiments, the oxygen ion transport material has Formula IIB, wherein A is selected from Al, Ga, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof; B is selected from Mn, Ti, Zr, Hf, V, Fe, Co, Cr, Ru, Ir; and a combination of at least one 2+ element (selected from Fe, Co, Ni, Mg, Ca, Zn, Cu, Mn) and at least one 3+, 4+, or 5+ element (selected from Fe, Co, Ni, Mn, Al, Ga, Ti, Zr, Hf, Cr, Ru, Ir, Ge, V, Nb, W); and C is selected from Si, Ge, Sn, and combinations thereof. In embodiments, the oxygen ion transport material has Formula IIC, wherein A is a combination of at least one 2+ or 1+ element (selected from Mg, Ca, Sr, Ba, Cu, Zn, Na) and at least one 3+ or 4+ element (selected from Al, Ga, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Fe); B is a combination of at least one 2+ element (selected from Fe, Co, Ni, Mg, Ca, Zn, Cu, Mn), and at least one 3+, 4+, or 5+ element (selected from Fe, Co, Ni, Mn, Al, Ga, Ti, Zr, Hf, Cr, Ru, Ir, Ge, V, Nb, W); and C is selected from Si, Ge, Sn, Al, and combinations thereof.

    TABLE-US-00003 TABLE 3 Embodiments of oxygen ion transport materials having Formula IIA, IIB, or IIC. Material A-site elements B-site elements C-site elements A.sub.4.sup.2+B.sub.5.sup.4+C.sub.4.sup.4+O.sub.22.sup.2? Mg, Ca, Sr, Ba, Ti, Zr, Hf, Ce, Re, Ir Si, Ge, Sn (Formula IIA) Cu, Zn A.sub.4.sup.3+B.sub.5.sup.3.2+C.sub.4.sup.4+O.sub.22.sup.2? Al, Ga, Sc, Y, La, Mn, Ti, Zr, Hf, V, Fe, Si, Ge, Sn (Formula IIB) Ce, Pr, Nd, Sm, Co, Cr, Ru, Ir, or a Eu, Gd, Tb, Dy, combination of a 2+ Ho, Er, Tm, Yb, element (Fe, Co, Ni, Lu Mg, Ca, Zn, Cu, Mn) and a 3+ or 4+ or 5+ element (Fe, Co, Ni, Mn, Al, Ga, Ti, Zr, Hf, Cr, Ru, Ir, Ge, V, Nb, W) A.sub.4.sup.2.5+B.sub.5.sup.3.6+C.sub.4.sup.4+O.sub.22.sup.2? A combination of V or a combination of Si, Ge, Sn, Al (Formula IIC) a 2+ or 1+ element a 2+ element (Fe, Co, (Mg, Ca, Sr, Ba, Ni, Mg, Ca, Zn, Cu, Cu, Zn, Na) and a Mn) and a 3+ or 4+ or 3+ or 4+ element 5+ element (Fe, Co, (Al, Ga, Sc, Y, La, Ni, Mn, Al, Ga, Ti, Zr, Ce, Pr, Nd, Sm, Hf, Cr, Ru, Ir, Ge, V, Eu, Gd, Tb, Dy, Nb, W) Ho, Er, Tm, Yb, Lu, Th, Fe)

    [0035] In embodiments, the oxygen ion transport material has Formula IIA, wherein A is Sr; B is selected from Zr, Ti, and combinations thereof; and C is Si. In embodiments, the oxygen ion transport material has Formula IIB, wherein A is selected from La, Pr, Nd, Sm, Ce, and combinations thereof; B is selected from Mn, V, Ti, Zn, Fe, Co, Ni, Al, Nb, Mg, Cr, and combinations thereof; and C is Si. In embodiments, the oxygen ion transport material has Formula IIB, wherein A is selected from La, Nd, and combinations thereof; B is selected from Mn, V, Ti, and combinations thereof; and C is Si. In embodiments, the oxygen ion transport material has Formula IIC, wherein A is Ce or a combination of at least two of Sr, Rare Earth Element (REE: Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), Fe, Ca, Na, and Th; B is selected from Zr, Ti, Fe, Mg, Mn, Cr, Al, Ga, V, W, Nb and combinations thereof; and C is Si or a combination of Si and Al. An illustrative list of such species is shown in Table 4, below. The materials of Table 4 have been experimentally synthesized and confirmed to share the same crystal structure as La.sub.4Mn.sub.5Si.sub.4O.sub.22 (see FIG. 2).

    TABLE-US-00004 TABLE 4 Additional embodiments of oxygen ion transport materials having Formula IIA, IIB, or IIC. Note that the empty square symbol ? denotes a vacancy. Formula IIA (A.sub.4.sup.2+B.sub.5.sup.4+C.sub.4.sup.4+O.sub.22.sup.2?) Sr.sub.4Ti.sub.5Si.sub.4O.sub.22 Matsubaraite Sr.sub.4(ZrTi.sub.4)Si.sub.4O.sub.22 Rengeite Formula IIB (A.sub.4.sup.3+B.sub.5.sup.3.2+C.sub.4.sup.4+O.sub.22.sup.2?) La.sub.4Mn.sub.5Si.sub.4O.sub.22 La.sub.4Ti.sub.5Si.sub.4O.sub.22 A.sub.4V.sub.5Si.sub.4O.sub.22 (A = La, Pr, Nd) A.sub.4(V, Zn).sub.5Si.sub.4O.sub.22 (A = La, Pr, Nd, Ce) A.sub.4(Mg.sub.2Ti.sub.3)Si.sub.4O.sub.22 (A = La, Pr, Nd, Sm) A.sub.4(Fe.sub.2Ti.sub.3)Si.sub.4O.sub.22 (A = La, Nd, (Ce, La)) A(Ni.sub.2Ti.sub.3)Si.sub.4O.sub.22 (A = La.sub.4, La.sub.2Pr.sub.2, LaPr.sub.3, La.sub.0.6Pr.sub.3.4, La.sub.2Nd.sub.2, Pr.sub.4, Nd.sub.4, Sm.sub.4, Sm.sub.2Nd.sub.2, Ce.sub.4) A(Co.sub.2Ti.sub.3)Si.sub.4O.sub.22 (A = La.sub.4, La.sub.3.4Pr.sub.0.6, La.sub.3Pr, La.sub.2.6Pr.sub.1.4, La.sub.2Pr.sub.2, Pr.sub.4, Nd.sub.4, Sm.sub.4, Sm.sub.2Nd.sub.2, Ce.sub.4, Ce.sub.2La.sub.2, CeLa.sub.3) La.sub.4Mn.sub.3Ge.sub.5.2Si.sub.0.8O.sub.22 La.sub.4(FeCoTi.sub.3)Si.sub.4O.sub.22 A(NiCoTi.sub.3)Si.sub.4O.sub.22 (A = La.sub.3Pr, La.sub.1.3Pr.sub.2.7, La.sub.2Pr.sub.2, Sm.sub.2Nd.sub.2) A.sub.4(FeAl.sub.2Ti.sub.2)Si.sub.4O.sub.22 (A = Pr, Nd, Ce) Ce.sub.4BSi.sub.4O.sub.22 (B = MgFe.sub.2Ti.sub.2, MgCr.sub.2Ti.sub.2, FeTi.sub.4, Fe(Ti, Fe).sub.4, Fe.sub.1.5AlTi.sub.2.5) (Ce, La).sub.4(Fe (Ti, Fe, Mn).sub.2Ti.sub.2)Si.sub.4O.sub.22 Dingdaohengite-(Ce) (Ce, La).sub.4(Fe, Ti, Nb).sub.5Si.sub.4O.sub.22 Maoniupingite-(Ce) Formula IIC (A.sub.4.sup.x+B.sub.5.sup.y+C.sub.4.sup.z+O.sub.22.sup.2? (4x + 5y + 4z = ?44)) Ce.sub.4(FeAlTi.sub.3)(Si.sub.3Al)O.sub.22 (Ce.sub.3Ca)(Fe(AlTi)Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3Ca)(Fe(Ga, Ti).sub.2Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3Sr)(Fe(AlTi)Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3Sr)(Fe(Ga, Ti).sub.2Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3.4Ca.sub.0.6)(Fe(Fe.sub.0.6Al.sub.0.8Ti.sub.0.7)Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3.7Ca.sub.0.3)(Fe(Fe.sub.0.76Al.sub.0.4Ti.sub.0.85)Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.3.8Ca.sub.0.2)(Fe(Fe.sub.0.8Al.sub.0.3Ti.sub.0.9)Ti.sub.2)Si.sub.4O.sub.22 (Ce.sub.1.2La.sub.1Nd.sub.0.15Sr.sub.1Ca.sub.0.5Na.sub.0.15).sub.4((Zr.sub.0.5Fe.sub.0.3Mn.sub.0.2)(Ti.sub.1.3Fe.sub.0.7).sub.2Ti.sub.2)Si.sub.4O.sub.22 (La.sub.3Sr)(Fe(GaTi)Ti.sub.2)Si.sub.4O.sub.22 (La.sub.3Ca)(Fe(AlTi)Ti.sub.2)Si.sub.4O.sub.22 Pr.sub.4(FeAl.sub.2Ti.sub.2)(Si.sub.3Al)O.sub.22 (Pr.sub.3Ca)(Fe(AlTi)Ti.sub.2)Si.sub.4O.sub.22 (Sr.sub.3.846Ce.sub.0.154)(ZrTi.sub.3.68Al.sub.0.1Fe.sub.0.22)Si.sub.4O.sub.22 (Ce, Fe).sub.4(Fe, Ti, Nb).sub.5Si.sub.4O.sub.22 (La, Ca).sub.4V.sub.5Si.sub.4O.sub.22 (Sr, REE).sub.4(Zr(Ti, Fe.sup.3+, Fe.sup.2+).sub.2Ti.sub.2)Si.sub.4O.sub.22 Hezuolinite (REE, Ca).sub.4(Fe.sup.2+(Ti, Fe.sup.2+, Mg, Fe.sup.3+).sub.2Ti.sub.2)Si.sub.4O.sub.22 (Ce, La, Ca, Th).sub.4(Fe.sup.2+(Ti, Fe.sup.2+, Mg, Fe.sup.3+, Al).sub.2(Ti, Nb).sub.2)Si.sub.4O.sub.22 Dingdaohengite-(Ce) (La, Ce, Ca).sub.4((Fe, Mn.sup.2+, Mg)Fe.sup.3+.sub.2(Ti, Fe.sup.3+).sub.2)Si.sub.4O.sub.22 (La, Ce, Ca).sub.4((Fe.sup.2+, Mn)(Ti, Fe.sup.3+, Al).sub.4)Si.sub.4O.sub.22 (La, Ce, Ca).sub.4(Fe.sup.2+(Ti, Fe.sup.3+).sub.4)Si.sub.4O.sub.22 Perrierite-(La) (Ce, La, Ca).sub.4(Fe.sup.2+ (Ti, Fe.sup.3+).sub.4)Si.sub.4O.sub.22 (REE, Ca).sub.4(Fe.sup.2+(Ti, Fe.sup.2+, Fe.sup.3+, Al).sub.2Ti.sub.2)Si.sub.4O.sub.22 Perrierite-(Ce) (Ce, Ca, Th).sub.4(Fe, Mg, Ti).sub.5Si.sub.4O.sub.22 (REE, Ca).sub.4(Fe.sup.2(Ti, Fe.sup.3+, Nb).sub.4)Si.sub.4O.sub.22 (REE, Ca).sub.4(Fe.sup.2(Ti, Fe.sup.3+, Fe.sup.2+, Al).sub.2Ti.sub.2)Si.sub.4O.sub.22 (REE, Ca, Th).sub.4((Fe.sup.2+, Mg)(Fe.sup.2+, Ti, Fe.sup.3+).sub.2(Ti, Fe.sup.3+).sub.2)Si.sub.4O.sub.22 (REE, Ca, Na).sub.4((Fe.sup.2+, Mg.sup.2+, Ti.sup.2+)(Fe.sup.2+, Nb.sup.5+, Al.sup.3+).sub.2(Ti.sup.4+, Ti.sup.3+, Nb.sup.5+).sub.2)Si.sub.4O.sub.22 (REE, Ca, Na).sub.4((Fe.sup.2+)(Fe.sup.2+, Nb.sup.5+, Al.sup.3+).sub.2(Ti.sup.4+, Ti.sup.3+, Nb.sup.5+, Mg.sup.2+).sub.2)Si.sub.4O.sub.22 (Ce, La, Nd, Ca, Sr, Th, Na).sub.4((Fe.sup.2+, Mg, Mn.sup.2+)(Fe.sup.3+, Ti, Al, Zr, Nb).sub.2Ti.sub.2)Si.sub.4O.sub.22 Chevkinite-(Ce) (REE, Ca).sub.4((Fe.sup.2+, Mg)(Cr.sup.3, Fe.sup.3+).sub.2(Ti, Nb).sub.2)Si.sub.4O.sub.22 Polyakovite-(Ce) (REE, Ca).sub.4((Fe.sup.3+, Ti, Fe.sup.2+, ?)(Ti, Fe3.sup.+, Fe.sup.2+, Nb).sub.2Ti.sub.2)Si.sub.4O.sub.22 Maoniupingite-(Ce) (REE, Ca).sub.4((Mg, Fe.sup.2+)(Cr.sup.3+, Fe.sup.3+).sub.2(Ti, Nb).sub.2)Si.sub.4O.sub.22 Polyakovite-(Ce) (Sr, La, Ce, Ca).sub.4(Fe(Ti, Zr).sub.2Ti.sub.2)Si.sub.4O.sub.22 (Sr, REE).sub.4(Fe.sup.2+(Ti.sup.4+, Fe).sub.4)Si.sub.4O.sub.22 Strontiochevkinite (Ce, La, Ca).sub.4(Mn.sup.2+(Ti, Fe.sup.3+).sub.3(Fe3.sup.+, Fe.sup.2+, Ti))Si.sub.4O.sub.22 (REE, Ca).sub.4(Mn.sup.2+(Ti, Fe.sup.3+).sub.3(Fe3.sup.+, Fe.sup.2+, Ti))Si.sub.4O.sub.22 (Ce, REE, Ca).sub.4((Mn, Fe.sup.2+)(Ti, Fe, Al).sub.4)Si.sub.4O.sub.22 Christofsch?ferite-(Ce) (Sr, La, Ce, Ca).sub.4(Zr(Ti, Fe).sub.2Ti.sub.2)Si.sub.4O.sub.22 Rengeite (REE, Ca).sub.4(Mg(Fe.sup.3+, W, Al).sub.3?)Si.sub.4O.sub.20(OH).sub.2 Delhuyarite-(Ce)
    Bi.sub.2MO.sub.4X Materials

    [0036] Embodiments of the oxygen ion transport materials have Formula III, Bi.sub.2MO.sub.4X wherein M is selected from Rare Earth Elements and X is selected from halogens. In embodiments, M is selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and combinations thereof and X is selected from F, Cl, Br, I, and combinations thereof. Each of these materials have been experimentally synthesized and confirmed to share the same crystal structure as Bi.sub.2LaO.sub.4Cl. Unless otherwise stated, more than one type of element M, X may be present on each relevant site as described above. However, in embodiments, a single type of element M is present and a single type of element X is present.

    [0037] Selection of AB.sub.2C.sub.4O.sub.12 and A.sub.4B.sub.5C.sub.4O.sub.22 materials which exhibit desirable oxygen ion transport properties may be guided by the following parameters including free volume, migration hop length, bulk thermodynamic stability, and valence state. These parameters, their calculations, and illustrative numeric values for each are described in the Example, below.

    [0038] Other parameters to be used to identify AB.sub.2C.sub.4O.sub.12 and A.sub.4B.sub.5C.sub.4O.sub.22 materials which exhibit desirable oxygen ion transport properties include the formation energy E.sub.f of the dilute oxygen interstitial ion in the AB.sub.2C.sub.4O.sub.12 or A.sub.4B.sub.5C.sub.4O.sub.22 material. Density functional theory (DFT) calculations may be used to determine E.sub.f at a T=300K and Po.sub.2=0.2 atm for a particular AB.sub.2C.sub.4O.sub.12 or A.sub.4B.sub.5C.sub.4O.sub.22 material as described in the Example, below. In embodiments, the oxygen ion transport material is characterized by an E.sub.f of not more than 1 eV under these conditions. This includes an E.sub.f in a range of from 0 eV to 1 eV and from 0.5 eV to 1 eV.

    [0039] Other parameters to be used to identify AB.sub.2C.sub.4O.sub.12 and A.sub.4B.sub.5C.sub.4O.sub.22 materials which exhibit desirable oxygen ion transport properties include the migration energy E.sub.m at a T=300K and Po.sub.2=0.2 atm of the oxygen ion in the AB.sub.2C.sub.4O.sub.12 or A.sub.4B.sub.5C.sub.4O.sub.22 material. Ab initio molecular dynamics (AIMD) simulations may be used to determine E.sub.m under these conditions for a particular AB.sub.2C.sub.4O.sub.12 or A.sub.4B.sub.5C.sub.4O.sub.22 material as described in the Example, below. In embodiments, the oxygen ion transport material is characterized by an E.sub.m under these conditions of not more than 0.6 eV. This includes an E.sub.m of not more than 0.5 eV, not more than 0.4 eV, not more than 0.3 eV, not more than 0.2 eV, not more than 0.1 eV, or 0 eV.

    [0040] The present oxygen ion transport materials may be characterized by the mechanism by which the oxygen ion diffuses through the material. In embodiments, the diffusion is interstitial-mediated oxygen diffusion, which encompasses both interstitial and interstitialcy oxygen diffusion. (See FIGS. 3A, 3C.) In other embodiments, the diffusion is vacancy-mediated oxygen diffusion. Theoretical calculations similar to those described above, and in the Example, below, may be used to evaluate materials for desirable vacancy-mediated oxygen diffusion properties. AIMD simulations may be used to confirm the type of mechanism as described in the Example, below. The Bi.sub.2MO.sub.4X materials may be characterized by exhibiting vacancy-mediated oxygen diffusion.

    [0041] The present oxygen ion transport materials may be synthesized by known techniques, such as the solid-state reaction heating techniques and the flux method referenced in the Example, below.

    Devices

    [0042] Although the present oxygen ion transport materials themselves are encompassed by the present disclosure, they may be incorporated into a variety of devices, which are also encompassed by the present disclosure. In general, any device comprising a source of oxygen ions may comprise that source, and also, any of the present oxygen ion transport materials in order to facilitate the transport of those oxygen ions within, to, or from the device. Thus, in embodiments, such a device comprises a source configured to generate oxygen ions via a redox reaction and an oxygen ion transport material through which the generated oxygen ions are transported. The source is a component, or a material thereof, in which, or on which (i.e., on a surface thereof), the redox reaction occurs. An illustrative redox reaction is O.sub.2+4e.sup.?.fwdarw.2O.sup.2?, in which molecular oxygen is reduced to two oxygen ions. An illustrative source configured to generate oxygen ions via this reaction is an electrode in electrical communication with a source of electrons, e.g., from a counter electrode. In embodiments, the source and the oxygen ion transport material are different, distinct entities. However, in other embodiments, the oxygen ion transport material itself may also be the source of the oxygen ions. This may be achieved if the oxygen ion transport material is also electrically conductive. Illustrative devices are described below, with reference to FIGS. 5-10.

    [0043] FIG. 5 depicts a schematic of a fuel cell comprising an oxygen ion transport material according to an illustrative embodiment. The fuel cell comprises an electrode (cathode), a counter electrode (anode) in electrical communication with the electrode, and an electrolyte between the electrode and the counter electrode. The electrode is the source of O.sup.2?, generated via the reduction of O.sub.2, which is transported through the electrolyte to the counter electrode. An embodiment of the present oxygen ion transport materials may be used as the electrolyte, or a component thereof. In embodiments, the electrode of the fuel cell may comprise, or be composed of, an embodiment of the present oxygen ion transport materials. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such fuel cells may be used. Fuel cells including additional components or adopting other configurations as compared to that of FIG. 5 may also be used.

    [0044] FIG. 6 depicts a schematic of a metal-air battery comprising an oxygen ion transport material according to an illustrative embodiment. The metal-air battery comprises an air electrode (air cathode), a counter electrode (metal anode) in electrical communication with the air electrode, and an electrolyte between the air electrode and the counter electrode. The air electrode is the source of O.sup.2?, generated via the reduction of O.sub.2 in air, which is transported through the electrolyte to the counter electrode. An embodiment of the present oxygen ion transport materials may be used as the electrolyte, or a component thereof. In embodiments, the air electrode of the metal-air battery may comprise, or be composed of, an embodiment of the present oxygen ion transport materials. This includes the present oxygen ion transport materials being used in, or as, a membrane in contact with the air electrode. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such metal-air batteries may be used. Metal-air batteries including additional components or adopting other configurations as compared to that of FIG. 6 may also be used.

    [0045] FIG. 7 depicts a schematic of a gas sensor comprising an oxygen ion transport material according to an illustrative embodiment. The gas sensor comprises a first electrode, a second electrode in electrical communication with the first electrode, and a membrane between the first and second electrodes. The first electrode is the source of O.sub.2?, generated via the reduction of O.sub.2 from air, which is transported through the membrane to the second electrode. An embodiment of the present oxygen ion transport materials may be used as the membrane, or a component thereof. In embodiments, the first electrode of the gas sensor may comprise, or be composed of, an embodiment of the present oxygen ion transport materials. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such gas sensors may be used. Gas sensors including additional components or adopting other configurations as compared to that of FIG. 7 may also be used.

    [0046] FIG. 8 depicts a schematic of a separation system comprising an oxygen ion transport material according to an illustrative embodiment. The separation system comprises an electrode, a counter electrode in electrical communication with the electrode, and membrane between the electrode and the counter electrode. The electrode is the source of O.sub.2?, generated via the reduction of O.sup.2, which is transported through the membrane to the counter electrode. Other gases which may be present on the electrode side (e.g., N.sup.2 in air), cannot pass through the membrane. Embodiments of the present oxygen ion transport materials may be used as the membrane, or a component thereof. In embodiments, the electrode and the counter electrode may not be necessary if the oxygen ion transport material is conductive. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such separation systems may be used. Separation systems including additional components or adopting other configurations as compared to that of FIG. 8 may also be used. In embodiments, the separation system may be a component of a membrane reactor. By way of illustration, membrane reactors configured to carry out reactions such as the oxidative coupling of methane, the partial oxidation of methane, and the oxidative dehydrogenation of ethane may also comprise a separation system as described herein to facilitate the uniform distribution of pure oxygen along the axial length of such reactors.

    [0047] FIG. 9 depicts a schematic of a supercapacitor comprising an oxygen ion transport material according to an illustrative embodiment. The supercapacitor comprises a first electrode, a counter electrode in electrical communication with the electrode, an electrolyte between the electrode and the counter electrode, and a separator positioned in the electrolyte. The electrode is the source of O.sup.2?, generated via the reduction of O.sub.2, which is transported through the electrolyte to the counter electrode. However, O.sup.2? can also form an electrical double layer with cations near the electrode side. As shown in the figure, embodiments of the present oxygen ion transport materials may be used as the electrode, or a component thereof. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such supercapacitors may be used. Supercapacitors including additional components or adopting other configurations as compared to that of FIG. 9 may also be used.

    [0048] FIG. 10 depicts a schematic of a steam reactor for carrying out solid oxide electrolysis comprising an oxygen ion transport material according to an illustrative embodiment. The steam reactor comprises an electrode (cathode), a counter electrode (anode) in electrical communication with the electrode, and a membrane between the electrode and the counter electrode. The electrode is the source of O.sup.2?, generated via the reduction of water (steam), which is transported through the membrane to the counter electrode. An embodiment of the present oxygen ion transport materials may be used as the membrane, or a component thereof. In embodiments, the electrode of the reactor may comprise, or be composed of, an embodiment of the present oxygen ion transport materials. Aside from the use of the oxygen ion transport material in the device, other materials generally used in such steam reactors may be used. Steam reactors including additional components or adopting other configurations as compared to that of FIG. 10 may also be used.

    Methods

    [0049] Methods of using any of the present oxygen ion transport materials and devices incorporating the materials are also encompassed by the present disclosure. In general, a method of transporting oxygen ions comprises exposing an embodiment of the present oxygen ion transport materials to a source of oxygen ions, wherein the oxygen ions are transported therethrough. The method may further comprise generating the oxygen ions from the source via a redox reaction. The method may further comprise steps involving the operation of the relevant device, e.g., the fuel cell, the metal-air battery, the gas sensor, the separation system, the supercapacitor, the steam reactor, etc.

    EXAMPLE

    [0050] Oxide materials were examined using a variety of theoretical calculations as follows. Crystallographic information files (CIF files) from the Material Project databases were used to calculate the free volume, migration hop length, bulk thermodynamic stability, and the valence state of the oxides. By way of illustration, a search approach for interstitial-mediated oxygen diffusion materials is described below.

    [0051] Voronoi analysis of the geometric structures was used to find the free volume. The shared corners and centers of shared edges of the Voronoi polyhedra were also used as initial guesses for the location of the oxygen interstitial (O.sup.i) site. The distance between the interstitial oxygen site and its nearest neighbors was used as the screening criterion. Specifically, for the distance between O.sub.i and its adjacent atom, subtracted by the ionic radius of the adjacent atom, the screening criterion was such that this distance is not smaller than 0.99 ? (i.e., distance?0.99 ?) when the adjacent atom is a cation and not smaller than 0.88 A (i.e., distance?0.88 ?) when the adjacent atom is oxygen, respectively. This criterion was used as a guide to determine if there is sufficient room for an O.sub.i atom in the material. The minimum distance between the oxygen interstitial sites was that this distance is less than or equal to 3 ? (i.e., minimum distance?3 ?). Energy above convex hull of the oxide materials in the closed system and under air condition, i.e., open system, (300K, 0.2 atm O.sub.2) was applied to evaluate the thermodynamic stability. In the closed system, the screening kept cases where the energy above hull was less than or equal to 100 meV/atom (i.e., energy above hull?100 meV/atom). In the open system, the screening kept cases where the energy above hull was less than or equal to 200 meV/atom (i.e., energy above hull?200 meV/atom). The valence state of the cations in the oxides was also analyzed and the screening criterion was that the valence state is smaller than its maximum oxidation state for at least one cation. Density functional theory (DFT) calculations were used to calculate the formation energy (E.sub.f) of the interstitial oxygen ion in the oxides. Finally, analysis of the oxygen ion diffusion properties of the oxides was carried out using ab initio molecular dynamics (AIMD) simulation and the nudged elastic band (NEB) method. These methods were used to evaluate the migration energy (E.sub.m) of the oxygen ion. The DFT calculation, AIMD simulation and the NEB calculation were performed by the Vienna Ab initio Simulation Package (VASP).

    [0052] As another illustration, a search approach for vacancy-mediated oxygen diffusion materials is described below. The screening kept cases where the distances between the lattice oxygen sites were used as the screening criterion. Specifically, the nearest lattice oxygen distance was less than or equal to 3 ? (i.e., distance?3 ?). Screening kept cases where the energy above convex hull of the oxide materials in the closed system was less than or equal to 100 meV/atom (i.e., energy above hull?100 meV/atom). Then the CIF files were analyzed by the bond-valence method, which provided an estimate of the energy barrier (E.sub.b) for the oxide-ion migration based on the geometry structure and composition of the materials. Screening kept cases where the estimated energy barrier was less than or equal to 1 eV. Finally, the defect formation energy and migration energy of oxygen vacancy with charge state 2+ (V{umlaut over (.sub.o)}) were studied at the DFT level.

    [0053] The results of the theoretical calculations described above were used to arrive at two representative oxygen ion transport materials, ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22. Table 5 also includes a few other representative oxygen ion transport materials. ZrMn.sub.2Ge.sub.4O.sub.12 is an oxide material with the tetragonal space group P4/nbm (a=b=9.77 ?, c=9.83 ?; ?=?=?=90?. The bulk structure is shown in FIGS. 1A and 1B. Specifically, the structure of ZrMn.sub.2Ge.sub.4P.sub.12 is composed of (001) layers of ZrO.sub.8 square antiprisms and MnO.sub.6 octahedra sharing edges, separated by layers of GeO.sub.4 tetrahedra. The GeO.sub.4 tetrahedra are linked into [Ge.sub.4O.sub.12].sup.8? rings, which are composed of four vertex-sharing GeO.sub.4 tetrahedra. ZrMn.sub.2Ge.sub.4O.sub.12 has been synthesized by solid-state reaction heating at 1125? C. (See Xu, D., Sale, M., Avdeev, M., Ling, C. D. & Battle, P. D. Dalt. Trans. 46, 6921-6933 (2017)).

    [0054] La.sub.4Mn.sub.5Si.sub.4O.sub.22 is isostructural with the chevkinite and perrierite structures, crystallizes in the monoclinic space group (C2/m (a=11.26 ?, b=7.59 <, c=11.34 ?; ?=74?. ?=75.6?. ?=68.3?). The La.sub.4Mn.sub.5Si.sub.4O.sub.22 material displays sorosilicate Si.sub.2O.sub.7 groups which separate rutile-like sheets of edge-shared MnO.sub.8 octahedra from single, isolated MnO.sub.8 octahedra, as shown in FIG. 2. La.sub.4Mn.sub.5Si.sub.4O.sub.22 has been synthesized by solid-state reaction heating at 850? C. (See Gueho, C., Giaquinta, D., Mansot, J. L., Ebel, T. & Palvadeau, P. Chem. Mater. 7, 486-492 (1995)).

    [0055] The formation energy of the oxygen interstitial (at ?2% interstitial concentration) in ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22 bulk structures were calculated under atmospheric condition (T=300K, P.sub.o2=0.2 atm) and are summarized in Table 5. Some calculations were performed for other materials as also shown in Table 5. Formation energies were studied with different DFT exchange and correlation functionals. These functionals consist of the generalized gradient approximation (GGA), GGA with Hubbard U correction (GGA+U), hybrid functional of Heyd, Scuseria and Ernzerhof (HSE06), and the strongly constrained and appropriately normed (SCAN) functional. Negative formation energies indicate that incorporating interstitial oxygen ions into the bulk structures is an energetically favorable process and oxygen interstitial defects are stable in the bulk structure. As noted above, the diffusion behavior of the oxygen ion in the bulk structures was studied by AIMD simulation. The migration pathway of oxygen ions in ZrMn.sub.2Ge.sub.4O.sub.12 showed an interstitialcy (or kick-out) mechanism, in which an oxygen interstitial hops to an oxygen lattice site and the lattice oxygen hops to another interstitial site. The complete migration pathway is displayed in FIG. 3A, where initial and final interstitial sites are labeled. Two lattice oxygen sites are also labeled to illustrate the kick-out process. The energy profile of the diffusion pathway calculated by the NEB method shows that the migration barrier is surprisingly low, 0.33 eV (FIG. 3B). The migration barrier was also calculated by AIMD simulation (see Table 6, below). FIG. 4A shows the Arrhenius plot for ZrMn.sub.2Ge.sub.4O.sub.8 of the AIMD-calculated oxygen-ion diffusivity versus the reciprocal of the temperature, with a calculated migration barrier of 0.34+0.03 eV, in excellent agreement with the NEB calculation. The error bars represent the numerical errors associated with the AIMD sampling and fitting E.sub.m, but do not represent errors associated with the use of DFT. Notably, the very low migration barriers are comparable to those for Li ions in LiFePO.sub.4, which is a commercial Li-ion battery cathode used in high-power applications. A similar plot is shown for La.sub.4Mn.sub.5Si.sub.4O.sub.22 in FIG. 4B. Therefore, the calculations show that the ZrMn.sub.2Ge.sub.4O.sub.12, La.sub.4Mn.sub.5Si.sub.4O.sub.22, and other materials in Table 5 support the kind of fast oxygen ion transport previously only obtained for cations in the solid state.

    TABLE-US-00005 TABLE 5 The formation energy of the oxygen interstitial E.sub.f under atmospheric condition (T = 300K, P.sub.O2 = 0.2 atm.) E.sub.f(eV) E.sub.f(eV) E.sub.f(eV) E.sub.f (eV) (GGA) (GGA + U) (HSE06) (SCAN) ZrMn.sub.2Ge.sub.4O.sub.12 ?0.88 1.64 1.24 ?0.49 La.sub.4Mn.sub.5Si.sub.4O.sub.22 ?0.55 0.74 0.73 ?0.11 La.sub.4Ti.sub.5Si.sub.4O.sub.22 ?1.62 ?1.72 CeMn.sub.2Ge.sub.4O.sub.12 ?0.89 ZrCo.sub.2Ge.sub.4O.sub.12 0.06 CeCo.sub.2Ge.sub.4O.sub.12 0.33 Y(YMn)Ge.sub.4O.sub.12 ?0.56 Y(YCo)Ge.sub.4O.sub.12 0.40 La.sub.4V.sub.5Si.sub.4O.sub.22 ?1.01 Nd.sub.4V.sub.5Si.sub.4O.sub.22 ?1.41

    TABLE-US-00006 TABLE 6 The migration barrier E.sub.m of the oxygen interstitial calculated by the NEB method and the AIMD simulation using the GGA functional. E.sub.m (eV) (NEB) E.sub.m (eV) (AIMD) ZrMn.sub.2Ge.sub.4O.sub.12 0.33 0.34 ? 0.03 La.sub.4Mn.sub.5Si.sub.4O.sub.22 0.53 0.44 ? 0.02 La.sub.4Ti.sub.5Si.sub.4O.sub.22 0.35 ? 0.08 CeMn.sub.2Ge.sub.4O.sub.12 0.54 0.57 ? 0.05

    [0056] As shown in FIG. 3C, for La.sub.4Mn.sub.5Si.sub.4O.sub.22, the interstitial oxygen ion shows an interstitial diffusion pathway in which the oxygen interstitial directly hops in between two SiO.sub.4 tetrahedra, without exchanging with the lattice oxygen. The initial and the final site of the interstitial are labeled in FIG. 3C. FIG. 3D shows the energy profile of the diffusion pathway calculated by the NEB method and FIG. 4B shows the Arrhenius plot of the AIMD-calculated oxygen-ion diffusivity versus the reciprocal of the temperature. Again, as summarized in Table 6, the calculated migration barrier for La.sub.4Mn.sub.5Si.sub.4O.sub.22 and other materials are surprisingly low.

    [0057] Similar theoretical calculations were performed to examine a vacancy-mediated oxygen transport material. The results of the theoretical calculations described above are presented below for the representative oxygen ion transport material Bi.sub.2LaO.sub.4Cl. Bi.sub.2LaO.sub.4Cl is a tetragonal structure with space group P4/mmm (a=b=3.99 ?, c=9.28 ?; ?=?=?=90?). The bulk structure is shown in FIG. 11. In the structure, [Bi.sub.2LaO.sub.4].sup.+ layers are interweaved with a single layer of halogen atoms, forming a layered structure. Bi is 4-fold coordinated and La is 8-fold coordinated. Bi.sub.2LaO.sub.4Cl may be synthesized by the flux method at 1073K. (See A. Nakada, et al. J. Am. Chem. Soc. 6, 2491-2499 (2021)). The formation energy of the oxygen vacancy with charge state 2+ (V{umlaut over (.sub.o)}) at ?1.6% vacancy concentration in Bi.sub.2LaO.sub.4Cl bulk structures was calculated at P.sub.o2=0.2 atm. The defect formation of V{umlaut over (.sub.o)} is 0.57 eV at 300K, ?0.04 eV at 873K, and ?0.43 eV at 1073K. The negative formation energy at 1073K indicates the formation of the V{umlaut over (.sub.o)} is energetically favorable during the synthesis process at P.sub.o2=0.2 atm. The diffusion behavior of the oxygen ion in the bulk structure was studied by AIMD simulation. The migration pathway of oxygen ions in Bi.sub.2LaO.sub.4Cl shows a vacancy-mediated mechanism, in which an oxygen hops from an oxygen lattice site to the vacant lattice oxygen. The complete migration pathway is displayed in FIG. 12A, where initial and final sites are labeled. The energy profile of the diffusion pathway calculated by the NEB method shows that the migration barrier is very low, 0.09 eV (FIG. 12B). The migration barrier was also calculated by fitting to temperature trends in AIMD simulation. FIG. 13 is the Arrhenius plot of the AIMD-calculated oxygen-ion diffusivity versus the reciprocal of the temperature. The data appears to show different barriers in different temperature regions and two linear fits were performed to identify one barrier in a high-temperature region and one in a low-temperature region. The calculated migration barrier from these linear fits is 0.32?0.04 eV in the high temperature region (T?1200K), and 0.10 ?0.02 eV in the low temperature region (T?1000K).

    [0058] Oxygen ion transport materials were examined using a variety of experimental techniques as follows. Materials were synthesized using a solid-state reaction or flux method, as appropriate. The resulting synthesized powders were analyzed using X-ray diffraction (XRD) to verify the crystal structure matched to known records and to check for the presence of multiple phases. Powder samples were pressed and sintered at high temperature to achieve dense samples. To assess the presence of interstitial oxygen, dense, sintered samples of the oxygen ion transport materials ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22, were examined using the electron probe micro-analyzer (EPMA) and iodometric titration methods. The chemical oxygen diffusivity and surface exchange coefficient of ZrMn.sub.2Ge.sub.4O.sub.12, La.sub.4Mn.sub.5Si.sub.4O.sub.22, and Bi.sub.2LaO.sub.4Cl were studied using the electrical conductivity relaxation (ECR) method. Electrical conductivity transient was measured with abrupt oxygen partial pressure change. Electrical conductivity transient was measured at multiple temperature and oxygen partial pressure conditions. Oxygen diffusivity D.sub.chem and surface exchange coefficient K.sub.chem were obtained by fitting the normalized electrical conductivity relaxation curve to the 2-D diffusion equations.

    [0059] ZrMn.sub.2Ge.sub.4O.sub.12 was synthesized through the solid-state reaction. Stoichiometric quantities of ZrO.sub.2, MnCO.sub.3, and GeO.sub.2 were mixed and grinded using an alumina mortar and pestle for 1 hour. Then the reaction mixture was heated in an alumina crucible with a volume of 30 ml at 1050? C. for 6 hours with lid on. The grinding and heating process was repeated for 9 times and the ZrMn.sub.2Ge.sub.4O.sub.12 powder was obtained. The crystalline structure of ZrMn.sub.2Ge.sub.4O.sub.12 was examined by XRD as shown in FIG. 14A, indicating a crystalline sample with diffraction peaks in the expected positions.

    [0060] La.sub.4Mn.sub.5Si.sub.4O.sub.22 was synthesized through the flux method. Stoichiometric quantities of La.sub.2O.sub.3, MnO.sub.2, and SiO.sub.2 were mixed with KCL flux. The flux-to-reactants mass ratio was 1.6:1. The reaction mixture was heated in an alumina crucible with a volume of 30 ml at 900? C. for 6 days with lid on. The sample was slow cooled down to 500? C. at a rate of 20? C./h and then cooled down to room temperature for 5 h at a rate of 95? C./h. The resultant powder was washed with deionized water for 7-10 times to dissolve the KCL flux and dried on a hot plate at 120? C. in air. La.sub.4Mn.sub.5Si.sub.4O.sub.22 powder was obtained and examined by XRD as shown in FIG. 14B, indicating a crystalline sample with diffraction peaks in the expected positions.

    [0061] Bi.sub.2LaO.sub.4Cl was synthesized through the flux method. Stoichiometric quantities of Bi.sub.2O.sub.3, BiOCl, and La.sub.2O.sub.3 were mixed with CsCl flux with 95% molar concentration of the solvent. The reaction mixture was heated in an alumina crucible at 800? C. for 20 h with lid on. The sample was cooled down to room temperature at a cooling rate of 240 ? C./h. After cooling down, the synthesized sample was washed with deionized water for several times to remove the CsCl flux and dried on a hot plate at 120? C. in air. Bi.sub.2LaO.sub.4Cl powder was obtained and examined by XRD as shown in FIG. 14C, indicating a crystalline sample with diffraction peaks in the expected positions. Synthesized Bi.sub.2LaO.sub.4Cl powder was pressed and sintered at 1000? C.for 8 h in Ar atmosphere. The Bi.sub.2LaO.sub.4Cl pellet is stable below 700? C. while decomposed at higher temperature in air.

    [0062] Synthesized ZrMn.sub.2Ge.sub.4O.sub.12 powder was pressed and sintered at 1100? C. for 10 h in air and La.sub.4Mn.sub.5Si.sub.4O.sub.22 powder was pressed and sintered at 1050? C. for 24 h in air to achieve densification. Electron probe micro-analyser (EPMA) analysis was performed on the polished pellet, and the results are summarized in Table 7. From the EPMA analysis, the derived stoichiometries are ZrMn.sub.2.04Ge.sub.3.79O.sub.12+1.14 and La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.42 respectively, revealing the presence of Ge-vacancy and interstitial oxygen in ZrMn.sub.2Ge.sub.4O.sub.12 and the presence of Mn-vacancy and interstitial oxygen in La.sub.4Mn.sub.5Si.sub.4O.sub.22. The presence of the interstitial oxygen validates the use of these compounds as oxygen ion transport materials for use in any of the devices described herein, including supercapacitors (for which capacitive charge storage is related to the oxygen interstitial concentration). Iodometric titration analysis was performed on the polished pellet of nominally La.sub.4Mn.sub.5Si.sub.4O.sub.22 and ZrMn.sub.2Ge.sub.4O.sub.12, the derived stoichiometry was La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.47 and ZrMn2.04Ge.sub.3.79O.sub.12+3.37 by assuming that the stoichiometry of cations is the same with the EPMA results. The existence of interstitial oxygen was confirmed by the EPMA and iodometric titration analysis.

    TABLE-US-00007 TABLE 7 Atomic percentage measured by EPMA and the derived formula from EPMA and Iodometric titration analysis compared with the ideal results. Zr Mn Ge O Formula Ideal 5.26% 10.53% 21.05% 63.16% ZrMn.sub.2Ge.sub.4O.sub.12 EPMA 5.01% 10.21% 19.00% 65.79% ZrMn.sub.2.04Ge.sub.3.79O.sub.12+1.14 Iodometric titration ZrMn.sub.2.04Ge.sub.3.79O.sub.12+3.37 La Mn Si O Formula Ideal 11.43% 14.29% 11.43% 62.86% La.sub.4Mn.sub.5Si.sub.4O.sub.22 EPMA 11.39% 13.34% 11.46% 63.81% La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.42 Iodometric titration La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.47

    [0063] FIGS. 15A-15B show the electrical conductivity of the ZrMn.sub.2Ge.sub.4O.sub.12 dense pellet, which was measured by switching oxygen partial pressure between 5% and 20% atm at 750? C. The resistivity changed from 1240 to 1195 ?*cm within ?5min. The fast response to the oxygen partial pressure indicates surprisingly fast oxygen exchange and diffusion. FIGS. 16A-16B show the electrical conductivity of the La.sub.4Mn.sub.5Si.sub.4O.sub.22 pellet, which was measured by switching oxygen partial pressure between 5% and 20% atm at 800? C. Again, surprisingly fast oxygen exchange and diffusion were observed. FIGS. 17A-17B show the electrical conductivity of the Bi.sub.2LaO.sub.4Cl pellet, which was measured by switching oxygen partial pressure between 10% and 20% atm at 600? C. Again, surprisingly fast oxygen exchange and diffusion were observed.

    [0064] Oxygen diffusivity D.sub.chem and surface exchange coefficient K.sub.chem were obtained by fitting the normalized electrical conductivity relaxation curve to the 2-D diffusion equations. Fitting of the normalized electrical conductivity relaxation curve of ZrMn.sub.2Ge.sub.4O.sub.12 with oxygen partial pressure changing from 5% to 20% at 750? C. is shown in FIG. 18A. Fitting of the normalized electrical conductivity relaxation curve of La.sub.4Mn.sub.5Si.sub.4O.sub.22 with oxygen partial pressure changing from 5% to 20% at 800? C. is shown in FIG. 18B. The derived D.sub.chem and K.sub.chem values are summarized in Table 8 and compared to the reference material LSCF, which is a representative mixed ionic and electronic conductor. The D.sub.chem and K.sub.chem of LSCF were obtained using the same method presented here. Both ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22 exhibit higher D.sub.chem and K.sub.chem as compared to LSCF, demonstrating faster oxygen diffusion and surface exchange in the new oxide materials (ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si+O.sub.22).

    TABLE-US-00008 TABLE 8 Fitted oxygen diffusivity D.sub.chem and surface exchange coefficient K.sub.chem of ZrMn.sub.2Ge.sub.4O.sub.12 and La.sub.4Mn.sub.5Si.sub.4O.sub.22 compared with the reference material LSCF. D.sub.chem K.sub.chem ZrMn.sub.2Ge.sub.4O.sub.12, 800? C. 3.93 ? 10.sup.?5 cm.sup.2/s 8.85 ? 10.sup.?4 cm.sup.2/s La.sub.4Mn.sub.5Si.sub.4O.sub.22, 750? C. 1.45 ? 10.sup.?5 cm.sup.2/s 6.72 ? 10.sup.?4 cm.sup.2/s LSCF, 775? C. 3.10 ? 10.sup.?6 cm.sup.2/s 3.19 ? 10.sup.?4 cm.sup.2/s

    [0065] The word illustrative is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as illustrative is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, a or an means one or more.

    [0066] Each of the formulas disclosed herein encompass compounds in which the amounts of the elements may deviate from ideal, e.g., non-stoichiometric compounds. This deviation is inherent in the nature of chemical compounds, including the fact that the compounds are capable of allowing for oxygen transport so that some oxygen may be missing as vacancies or additional oxygen may be present during transport. For example, the deviation may be up to about 0.5 in cations. This includes up to about 0.4, up to about 0.3, up to about 0.2, and up to about 0.1. The deviation for oxygen may be, e.g., up to 25% of oxygen missing as oxygen vacancies or up to about 20% additional oxygen as interstitials. As a specific example, the formula ZrMn.sub.2Ge.sub.4O.sub.12 encompasses the measured stoichiometries in Table 7, i.e., ZrMn.sub.2.04Ge.sub.3.79O.sub.12+3.37 and ZrMn.sub.2.04Ge.sub.3.79O.sub.12+1.14. Similarly, the formula La.sub.4Mn.sub.5Si.sub.4O.sub.22 encompasses La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.42 and La.sub.4Mn.sub.4.69Si.sub.4.03O.sub.22+0.47.

    [0067] All numeric values of parameters in the present disclosure are proceeded by the term about which means approximately. This encompasses those variations inherent to the measurement of the relevant parameter as understood by those of ordinary skill in the art. This also encompasses the exact value of the disclosed numeric value and values that round to the disclosed numeric value.

    [0068] The foregoing description of illustrative embodiments of the disclosure has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principles of the disclosure and as practical applications of the disclosure to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the claims appended hereto and their equivalents.