Alkali oxide-tantalum oxide and alkali oxide-niobium oxide ionic conductors

Roth, Robert; Parker, H.S.; Brower, W. S.; Minor, D. B.

doi:10.6028/nbs.ir.74-440

Cited by 16 publications

(11 citation statements)

References 18 publications

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“…A triclinic phase with a composition very close to that of K3NbTOl9 has been published by Roth et al (1974). The formula is given as KsNb18049 but can also be written as K3.10Nb6.98Oi9.…”

Section: Resultsmentioning

confidence: 99%

“…In addition to these compounds, there exist two kinds of layer structures, namely K4Nb6Ol7 (Gasperin & Le Bihan, 1982) and L-KNb308 (Gasperin, 1982), both determined by single-crystal X-ray diffraction. A survey of the KNbO3-Nb2Os system published by Roth, Parker, Brower & Minor (1974) included several of the compounds mentioned above as well as a triclinic phase which was assigned the composition KsNb18049.…”

Section: Introductionmentioning

confidence: 99%

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Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction

Sundberg¹,

Lundberg²

1987

Acta Crystallogr Sect B

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An idealized structure model of the K3Nb7Ol9 compound has been deduced from high-resolution electron micrographs. For simplicity the structure was derived in a pseudo-monoclinic system with triclinic symmetry (space group P1) and unit-cell dimensions a = 13.777 (2), b =6-431 (1), c= 18.897 (6) A, a-~ 90, /3 = 98.06 (2) and y -~ 90 °, V = 1657.7 A 3, Z = 4. It has been verified both by simulated image calculations in two projections and by X-ray powder diffraction studies. The structure consists of a threedimensional framework which is built up of pairs of NbO6 octahedra having one edge in common in such a way that the structure can be described by means of{011} crystallographic shear in the ReO3 type structure. The pairs are linked by edge and corner sharing as in the {120} crystallographic-shear (CS) structure M702o. Two kinds of tunnels are formed, in which the K atoms are located. The structure thus independently derived agrees with that recently published by triclinic. We have refined the cell parameters given in that article: a = 14.1282 (9), b--9.9369 (9), c = 6.4553 (6) A, a= 106.44(1), /3=95.856(6) and y= 97.30 (1) °, V= 853.05 ~3, Z =2, M~ = 1071.64, and Dx = 4.17 g cm -3. However, in this paper the structure is described in a different manner and discussed in relation to neighbouring compounds of this system.

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“…A triclinic phase with a composition very close to that of K3NbTOl9 has been published by Roth et al (1974). The formula is given as KsNb18049 but can also be written as K3.10Nb6.98Oi9.…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction

Sundberg¹,

Lundberg²

1987

Acta Crystallogr Sect B

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“…It has already been mentioned in the previous summary report (1) that the hexagonal tungsten bronze-type phase (HTB) found in binary alkali niobate and tantalate systems has alkali ions in non-stoichiometric positions and excess Nb+5 or Is +5 ions. These excess pentavalent ions may well block the alkali ion conductivity as these hexagonal bronzes cannot be ion exchanged.…”

Section: Hexagonal Tungsten Bronze-type Phases (Htb)mentioning

confidence: 85%

“…As in the K20-Ta205 [1,2] and Rb 20 -Nb 20 5 systems a layer sequence 9-L, 16-L, 11-L ( in order of increasing alkali content) was found to be present. The IITB and GTB-like phases [ 1] were also found to be present. The results of the experiments are given in Table 2 and the phase equilibrium diagram interpreted from this data is shown in Figure 2.…”

Section: The System Ta 20 5 4rb20:llta205mentioning

confidence: 87%

“…which represents a line in the system shown by the join 3:1 --348 in Figure 6 and involves the evolution of one molecule of gas (0 2 ) In the previous contract summary report [1] it was reported that the compound occurring at about 2K20 : 3Nb 20 5 had the unit cell dimensions a-7.822, b-33.019, c=6.481A when not hydrated. Only the b axis expanded upon exposure to moisture as previously mentioned by Nassau [ 15].…”

Section: Hexagonal Tungsten Bronze -Pyrochlore Seriesmentioning

confidence: 99%

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Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

Roth

Brower²,

Parker³

et al. 1975

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Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

Złotnik

Sahu

Navrotsky

et al. 2015

Chemistry A European J

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Alkali niobates and tantalates are currently important lead-free functional oxides. The formation and decomposition energetics of potassium tantalum oxide compounds (K2 O-Ta2 O5 ) were measured by high-temperature oxide melt solution calorimetry. The enthalpies of formation from oxides of KTaO3 perovskite and defect pyrochlores with K/Ta ratio of less than 1 stoichiometry-K0.873 Ta2.226 O6 , K1.128 Ta2.175 O6 , and K1.291 Ta2.142 O6 -were experimentally determined, and the values are (-203.63 ± 2.92) kJ mol(-1) for KTaO3 perovskite, and (-339.54 ± 5.03) kJ mol(-1) , (-369.71 ± 4.84) kJ mol(-1) , and (-364.78 ± 4.24) kJ mol(-1) , respectively, for non-stoichiometric pyrochlores. That of stoichiometric defect K2 Ta2 O6 pyrochlore, by extrapolation, is (-409.87 ± 6.89) kJ mol(-1) . Thus, the enthalpy of the stoichiometric pyrochlore and perovskite at K/Ta=1 stoichiometry are equal in energy within experimental error. By providing data on the thermodynamic stability of each phase, this work supplies knowledge on the phase-formation process and phase stability within the K2 O-Ta2 O5 system, thus assisting in the synthesis of materials with reproducible properties based on controlled processing. Additionally, the relation of stoichiometric and non-stoichiometric pyrochlore with perovskite structure in potassium tantalum oxide system is discussed.

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Alkali oxide-tantalum oxide and alkali oxide-niobium oxide ionic conductors

Cited by 16 publications

References 18 publications

Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction

Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction

Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

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Alkali oxide-tantalum oxide and alkali oxide-niobium oxide ionic conductors

Cited by 16 publications

References 18 publications

Studies of K3Nb7O19 by high-resolution electron microscopy and X-ray powder diffraction

Studies of K3Nb7O19 by high-resolution electron microscopy and X-ray powder diffraction

Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

Pyrochlore and Perovskite Potassium Tantalate: Enthalpies of Formation and Phase Transformation

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Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction

Studies of K₃Nb₇O₁₉ by high-resolution electron microscopy and X-ray powder diffraction