Effect of Preparation Conditions on the Polymorphism and Transport Properties of La6–xMoO12−δ (0 ≤ x ≤ 0.8)

López-Vergara, Adrián; Porras-Vázquez, José M.; Infantes‐Molina, Antonia; Canales‐Vázquez, Jesús; Cabeza, Aurelio; Losilla, Enrique R.; Marrero-López, D.

doi:10.1021/acs.chemmater.7b02481

Cited by 42 publications

(78 citation statements)

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“…Above 700 °C, the Sm 2−x Ca x Zr 2 O 7−x/2 (x = 0.05, 0.1) solid solutions have the conductivity, which is independent of humidity (Figure 6). According to López-Vergara et al [41], this means that oxygen-ion conductivity prevails at these temperatures. The activation energies for conduction in dry and wet atmospheres are indicated in Table 4.…”

Section: Resultsmentioning

confidence: 99%

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

et al. 2019

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Sm2−xCaxZr2O7−x/2 (x = 0, 0.05, 0.1) and Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1) mixed oxides in a pyrochlore–fluorite morphotropic phase region were prepared via the mechanical activation of oxide mixtures, followed by annealing at 1600 °C. The structure of the solid solutions was studied by X-ray diffraction and refined by the Rietveld method, water content was determined by thermogravimetry (TG), their bulk and grain-boundary conductivity was determined by impedance spectroscopy in dry and wet air (100–900 °C), and their total conductivity was measured as a function of oxygen partial pressure in the temperature range: 700–950 °C. The Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) pyrochlore solid solutions, lying near the morphotropic phase boundary, have proton conductivity contribution both in the grain bulk and on grain boundaries below 600 °C, and pure oxygen–ion conductivity above 700 °C. The 500 °C proton conductivity contribution of Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) is ~ 1 × 10−4 S/cm. The fluorite-like Gd2−xCaxZr2O7−x/2 (x = 0.1) solid solution has oxygen-ion bulk conductivity in entire temperature range studied, whereas proton transport contributes to its grain-boundary conductivity below 700 °C. As a result, of the morphotropic phase transition from pyrochlore Sm2−xCaxZr2O7−x/2 (x = 0.05, 0.1) to fluorite-like Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1), the bulk proton conductivity disappears and oxygen-ion conductivity decreases. The loss of bulk proton conductivity of Gd2−xCaxZr2O7−x/2 (x = 0.05, 0.1) can be associated with the fluorite structure formation. It is important to note that the degree of Ca substitution in such solid solutions (Ln2−xCax)Zr2O7−δ (Ln = Sm, Gd) is low, x < 0.1. In both series, grain-boundary conductivity usually exceeds bulk conductivity. The high grain-boundary proton conductivity of Ln2−xCaxZr2O7−x/2 (Ln = Sm, Gd; x = 0.1) is attributable to the formation of an intergranular CaZrO3-based cubic perovskite phase doped with Sm or Gd in Zr sublattice.

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Section: Resultsmentioning

confidence: 99%

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

et al. 2019

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“…[1][2][3][4][5][6][7] Ln 6-x Zr x MoO 12-δ (Ln = La, Nd, Sm, Dy, Ho) Zr-doped molybdates, pure La 5.5 MoO 11.25 , pure and doped La 5.4 MoO 11.1 , and Ln 10 Mo 2 O 21 (Ln = Nd, Gd -Ho) have mixed electron-ion (electron-proton) conductivity and are promising materials for SOFC electrolytes and proton-conducting membranes. [5][6][7][8][9][10][11][12][13][14] Zirconium doping improves the stability of these materials to…”

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confidence: 99%

“…12 The Ln 6-x MoO 12-δ (Ln = La, Nd, Sm; x = 0, 0.5, 1) light molybdates are known to differ from other molybdates of R 2 O 3 -MoO 3 systems in that Mo 6+ is the most stable in these compounds. 6,7,9,12,13 Because of this, light molybdates hold the greatest promise for the preparation of mixed conductors with the highest ionic and/or protonic conductivity among the known rare-earth molybdates.…”

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confidence: 99%

“…In particular, temperatures well above 1000°C are often needed for the synthesis of lanthanide-based multicomponent oxides, rather promising as luminescent and optical materials [1][2][3][4] and oxygen-ion (proton) conductors. [6][7][8][9][10][11][12] MA and MS allow usually lowering the synthesis temperature for initially activated materials and, in some cases, ensure targeted synthesis of unique powder products at room temperature. For example, having a cubic structure, oxygen-ion conducting pyrochlores rather often result from room-temperature mechanochemical synthesis.…”

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confidence: 99%

“…Analysis of the proton conductivity of the rare-earth molybdates and tungstates demonstrates that the ionic (proton) conductivity drops with decreasing R ionic radius. [7][8][9]21,22 Because of this, the room-temperature mechanochemical synthesis of La 10 Mo 2 O 21 with high electron-proton conductivity is of greatest interest.…”

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Room‐temperature mechanochemical synthesis of RE molybdates: Impact of structural similarity and basicity of oxides

et al. 2021

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RE molybdates and tungstates are very important inorganic materials that have a high potential application in various fields: photoluminescence, optical fibers, laser materials, and mixed conductors. [1][2][3][4][5][6][7] Ln 6-x Zr x MoO 12-δ (Ln = La, Nd, Sm, Dy, Ho) Zr-doped molybdates, pure La 5.5 MoO 11.25 , pure and doped La 5.4 MoO 11.1 , and Ln 10 Mo 2 O 21 (Ln = Nd, Gd -Ho) have mixed electron-ion (electron-proton) conductivity and are promising materials for SOFC electrolytes and proton-conducting membranes. [5][6][7][8][9][10][11][12][13][14] Zirconium doping improves the stability of these materials to

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High Proton Conductivity in β‐Ba₂ScAlO₅ Enabled by Octahedral and Intrinsically Oxygen‐Deficient Layers

Murakami

Avdeev

Morikawa

et al. 2022

Adv Funct Materials

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Proton conductors are promising materials for clean energy, but most available materials exhibit sufficient conductivity only when chemically substituted to create oxygen vacancies, which often leads to difficulty in sample preparation and chemical instability. Recently, proton conductors based on hexagonal perovskite‐related oxides have been attracting attention as they exhibit high proton conductivity even without the chemical substitutions. However, their conduction mechanism has been elusive so far. Herein, taking three types of oxides with different stacking patterns of oxygen‐deficient layers (β‐Ba2ScAlO5, α‐Ba2Sc0.83Al1.17O5, and BaAl2O4) as examples, the roles of close‐packed double‐octahedral layers and oxygen‐deficient layers in proton conduction are shown. It is found that “undoped” β‐Ba2ScAlO5, which adopts a structure having alternating double‐octahedral layer and double‐tetrahedral layer with intrinsically oxygen‐deficient hexagonal BaO (h') layer, shows high proton conductivity (≈10−3 S cm−1 above 300 °C), comparable to representative proton conductors. In contrast, the structurally related oxides α‐Ba2Sc0.83Al1.17O5 and BaAl2O4 exhibit lower conductivity. Ab initio molecular dynamics simulations revealed that protons in β‐Ba2ScAlO5 migrate through the double‐octahedral layer, while the h′ layer plays the role of a “proton reservoir” that supplies proton carriers to the proton‐conducting double‐octahedral layers. The distinct roles of the two layers in proton conduction provide a strategy for developing high‐performance proton conductors.

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Effect of Preparation Conditions on the Polymorphism and Transport Properties of La_6–xMoO_12−δ (0 ≤ x ≤ 0.8)

Cited by 42 publications

References 46 publications

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Room‐temperature mechanochemical synthesis of RE molybdates: Impact of structural similarity and basicity of oxides

High Proton Conductivity in β‐Ba₂ScAlO₅ Enabled by Octahedral and Intrinsically Oxygen‐Deficient Layers

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Effect of Preparation Conditions on the Polymorphism and Transport Properties of La6–xMoO12−δ (0 ≤ x ≤ 0.8)

Cited by 42 publications

References 46 publications

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Evolution of Oxygen–Ion and Proton Conductivity in Ca-Doped Ln2Zr2O7 (Ln = Sm, Gd), Located Near Pyrochlore–Fluorite Phase Boundary

Room‐temperature mechanochemical synthesis of RE molybdates: Impact of structural similarity and basicity of oxides

High Proton Conductivity in β‐Ba2ScAlO5 Enabled by Octahedral and Intrinsically Oxygen‐Deficient Layers

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Effect of Preparation Conditions on the Polymorphism and Transport Properties of La_6–xMoO_12−δ (0 ≤ x ≤ 0.8)

High Proton Conductivity in β‐Ba₂ScAlO₅ Enabled by Octahedral and Intrinsically Oxygen‐Deficient Layers