The Experts below are selected from a list of 243 Experts worldwide ranked by ideXlab platform
Thommy Ekström - One of the best experts on this subject based on the ideXlab platform.
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Study on the solid solubility of Al in the Melilite systems R2Si3 − xAlxO3 + xN4 − x with R = Nd, Sm, Gd, Dy and Y
Journal of the European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.
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study on the solid solubility of al in the Melilite systems r2si3 xalxo3 xn4 x with r nd sm gd dy and y
Journal of The European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.
Mathieu Allix - One of the best experts on this subject based on the ideXlab platform.
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La2Ga3O7.5: A Metastable Ternary Melilite with a Super-Excess of Interstitial Oxide Ions Synthesized by Direct Crystallization of the Melt
Chemistry of Materials, 2020Co-Authors: Jintai Fan, Xiaojun Kuang, Vincent Sarou-kanian, Xiaoyan Yang, Maria Diaz-lopez, Franck Fayon, Michael J. Pitcher, Mathieu AllixAbstract:The La1+xAE1-xGa3O7+x/2 Melilite family (AE = Ca, Sr, Ba, and 0 0.65 with very high Oint concentrations (referred to here as "super-excess" compositions) have the potential to support correspondingly high ionic conductivities, but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here we report that fully-substituted La2Ga3O7.5 (x = 1) Melilite ceramics can be synthesized by direct crys-tallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S.cm-1 at 800 °C, three orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7, and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S.cm-1). It crystallizes in an orthorhombic √2a x √2a x 2c expansion of the parent Melilite cell, in space group Ima2, with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D Melilite framework, which appears to be an incipient feature of previously reported partially-ordered Melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended com-positional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.
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La2Ga3O7.5: a metastable ternary Melilite with a super-excess of inter- stitial oxide ions synthesized by direct crystallization of the melt
Chemistry of Materials, 2020Co-Authors: Jintai Fan, Xiaojun Kuang, Vincent Sarou-kanian, Xiaoyan Yang, Maria Diaz-lopez, Franck Fayon, Michael Pitcher, Mathieu AllixAbstract:The La1+xAE1-xGa3O7+x/2 Melilite family (AE = Ca, Sr, Ba, and 0 < x < 0.64) demonstrates remarkable oxide ion conductivity due to the ability of its layered tetrahedral [Ga3O7+x/2] network to accommodate and transport interstitial oxide ions (Oint). Compositions x > 0.65 with very high Oint concentrations (referred to here as "super-excess" compositions) have the potential to support correspondingly high ionic conductivities, but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here we report that fully-substituted La2Ga3O7.5 (x = 1) Melilite ceramics can be synthesized by direct crys-tallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S.cm-1 at 800 °C, three orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7, and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S.cm-1). It crystallizes in an orthorhombic √2a x √2a x 2c expansion of the parent Melilite cell, in space group Ima2, with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D Melilite framework, which appears to be an incipient feature of previously reported partially-ordered Melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended com-positional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.
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Development of Melilite-Type Oxide Ion Conductors.
Chemical record (New York N.Y.), 2020Co-Authors: Lijia Zhou, Mathieu Allix, Xiaojun KuangAbstract:Lowering the operating temperature of solid oxide fuel cells (SOFCs) requires high performance oxide ion conductor electrolytes. Recently tetrahedra-based structures have been attracting considerable attention for oxide ion conductor development, among which the layered tetrahedral network Melilite structure appears particularly interesting owing to its remarkable capability to accommodate and transport interstitial oxide ions, compared with isolated tetrahedral anion structures. Stabilization and migration mechanisms of interstitial oxide ions in Melilites have been systematically investigated using local structural relaxation from both electrostatic Coulomb interaction and chemical bonding aspects based on atomic and electronic structures respectively using experimental and theoretical approaches. These reveal cationic size and chemical bonding effects on stabilization and migration mechanisms of interstitial oxide ions. Lately, full crystallization from glass, an innovative synthesis method, was employed to produce new metastable Melilite oxide ion conductors which are inaccessible using classic solid state reaction owing to cationic size effect. Finally, the thermal and chemical stability at low temperature and the high oxide ion conductivity of the best Melilite oxide ion conductors based on LaSrGa 3 O 7 are likely to provide real possibilities of applications of Melilite-type electrolytes in SOFCs and other related devices.
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Interstitial Oxide Ion Migration Mechanism in Aluminate Melilite La 1+ x Ca 1– x Al 3 O 7+0.5 x Ceramics Synthesized by Glass Crystallization
ACS Applied Energy Materials, 2019Co-Authors: Jiehua Wang, Aydar Rakhmatullin, Sandra Ory, Alberto Fernández-carrión, Xiaojun Kuang, Mathieu AllixAbstract:Gallate Melilite materials have attracted considerable interest as new interstitial oxide ion conducting electrolytes for solid oxide fuel cells for more than a decade. However, the preparation of aluminate Melilite materials as interstitial oxide ion conductors remains a challenge. Here, we show that interstitial oxide ion conducting aluminate Melilite materials La1+xCa1-xAl3O7+0.5x (x = 0-0.5) can be prepared via a full crystallization from bulk glass process. Rietveld refinements performed from combined neutron and synchrotron X-ray powder diffraction (NPD and SPD) data reveal multiple interstitial defect positions within the pentagonal ring, demonstrating the diversity of local structures around the oxygen interstitial defects in La La1+xCa1-xAl3O7+0.5x. Variable temperature solid-state Al-27 nuclear magnetic resonance (NMR) spectroscopy measurements demonstrate the existence of 5-coordinated AlO5 polyhedra and dynamic exchange processes between these 5-coordinated Al sites, representing the first example of evidence for the migration mechanism of interstitial oxide ions in Melilites by NMR. This latter involves framework and interstitial oxide ions, and is assisted by rotation and deformation of tetrahedra. These calculations reveal reduced mobility of interstitial oxide ions in aluminate tetrahedral network owing to its rigidity.
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Interstitial Oxide Ion Migration Mechanism in Aluminate Melilite La1+xCa1–xAl3O7+0.5x Ceramics Synthesized by Glass Crystallization
2019Co-Authors: Jiehua Wang, Aydar Rakhmatullin, Sandra Ory, Xiaojun Kuang, Alberto J. Fernández-carrión, Mathieu AllixAbstract:Gallate Melilite materials have attracted considerable interest as new interstitial oxide ion conducting electrolytes for solid oxide fuel cells for more than a decade. However, the preparation of aluminate Melilite materials as interstitial oxide ion conductors remains a challenge. Here, we show that interstitial oxide ion conducting aluminate Melilite materials La1+xCa1–xAl3O7+0.5x (x = 0–0.5) can be prepared via a full crystallization from bulk glass process. Rietveld refinements performed from combined neutron and synchrotron X-ray powder diffraction (NPD and SPD) data reveal multiple interstitial defect positions within the pentagonal ring, demonstrating the diversity of local structures around the oxygen interstitial defects in La1+xCa1–xAl3O7+0.5x. Variable temperature solid-state 27Al nuclear magnetic resonance (NMR) spectroscopy measurements demonstrate the existence of 5-coordinated AlO5 polyhedra and dynamic exchange processes between these 5-coordinated Al sites, representing the first example of evidence for the migration mechanism of interstitial oxide ions in Melilites by NMR. This latter involves framework and interstitial oxide ions, and is assisted by rotation and deformation of tetrahedra. These calculations reveal reduced mobility of interstitial oxide ions in aluminate tetrahedral network owing to its rigidity
P.l. Wang - One of the best experts on this subject based on the ideXlab platform.
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Study on the solid solubility of Al in the Melilite systems R2Si3 − xAlxO3 + xN4 − x with R = Nd, Sm, Gd, Dy and Y
Journal of the European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.
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study on the solid solubility of al in the Melilite systems r2si3 xalxo3 xn4 x with r nd sm gd dy and y
Journal of The European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.
Xiaojun Kuang - One of the best experts on this subject based on the ideXlab platform.
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La2Ga3O7.5: A Metastable Ternary Melilite with a Super-Excess of Interstitial Oxide Ions Synthesized by Direct Crystallization of the Melt
Chemistry of Materials, 2020Co-Authors: Jintai Fan, Xiaojun Kuang, Vincent Sarou-kanian, Xiaoyan Yang, Maria Diaz-lopez, Franck Fayon, Michael J. Pitcher, Mathieu AllixAbstract:The La1+xAE1-xGa3O7+x/2 Melilite family (AE = Ca, Sr, Ba, and 0 0.65 with very high Oint concentrations (referred to here as "super-excess" compositions) have the potential to support correspondingly high ionic conductivities, but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here we report that fully-substituted La2Ga3O7.5 (x = 1) Melilite ceramics can be synthesized by direct crys-tallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S.cm-1 at 800 °C, three orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7, and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S.cm-1). It crystallizes in an orthorhombic √2a x √2a x 2c expansion of the parent Melilite cell, in space group Ima2, with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D Melilite framework, which appears to be an incipient feature of previously reported partially-ordered Melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended com-positional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.
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La2Ga3O7.5: a metastable ternary Melilite with a super-excess of inter- stitial oxide ions synthesized by direct crystallization of the melt
Chemistry of Materials, 2020Co-Authors: Jintai Fan, Xiaojun Kuang, Vincent Sarou-kanian, Xiaoyan Yang, Maria Diaz-lopez, Franck Fayon, Michael Pitcher, Mathieu AllixAbstract:The La1+xAE1-xGa3O7+x/2 Melilite family (AE = Ca, Sr, Ba, and 0 < x < 0.64) demonstrates remarkable oxide ion conductivity due to the ability of its layered tetrahedral [Ga3O7+x/2] network to accommodate and transport interstitial oxide ions (Oint). Compositions x > 0.65 with very high Oint concentrations (referred to here as "super-excess" compositions) have the potential to support correspondingly high ionic conductivities, but have never before been accessed due to the limitations of conventional solid-state ceramic synthesis. Here we report that fully-substituted La2Ga3O7.5 (x = 1) Melilite ceramics can be synthesized by direct crys-tallization of an under-cooled melt, demonstrating that super-excess compositions are accessible under suitable nonequilibrium reaction conditions. La2Ga3O7.5 is stable up to 830 °C and exhibits an ionic conductivity of 0.01 S.cm-1 at 800 °C, three orders of magnitude higher than the corresponding x = 0 end-member LaSrGa3O7, and close to the range exhibited by the current best-in-class La1.54Sr0.46Ga3O7.23 (0.1 S.cm-1). It crystallizes in an orthorhombic √2a x √2a x 2c expansion of the parent Melilite cell, in space group Ima2, with full long-range ordering of Oint into chains within the [Ga3O7.5] layers. The emergence of this chain-like (1D) ordering within the 2D Melilite framework, which appears to be an incipient feature of previously reported partially-ordered Melilites, is explained in terms of the underlying hexagonal topology of the structure. These results will enable the exploration of extended com-positional ranges for the development of new solid oxide ion electrolytes with high concentrations of interstitial oxide charge carriers.
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Development of Melilite-Type Oxide Ion Conductors.
Chemical record (New York N.Y.), 2020Co-Authors: Lijia Zhou, Mathieu Allix, Xiaojun KuangAbstract:Lowering the operating temperature of solid oxide fuel cells (SOFCs) requires high performance oxide ion conductor electrolytes. Recently tetrahedra-based structures have been attracting considerable attention for oxide ion conductor development, among which the layered tetrahedral network Melilite structure appears particularly interesting owing to its remarkable capability to accommodate and transport interstitial oxide ions, compared with isolated tetrahedral anion structures. Stabilization and migration mechanisms of interstitial oxide ions in Melilites have been systematically investigated using local structural relaxation from both electrostatic Coulomb interaction and chemical bonding aspects based on atomic and electronic structures respectively using experimental and theoretical approaches. These reveal cationic size and chemical bonding effects on stabilization and migration mechanisms of interstitial oxide ions. Lately, full crystallization from glass, an innovative synthesis method, was employed to produce new metastable Melilite oxide ion conductors which are inaccessible using classic solid state reaction owing to cationic size effect. Finally, the thermal and chemical stability at low temperature and the high oxide ion conductivity of the best Melilite oxide ion conductors based on LaSrGa 3 O 7 are likely to provide real possibilities of applications of Melilite-type electrolytes in SOFCs and other related devices.
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Development of Melilite‐Type Oxide Ion Conductors
Chemical Record, 2020Co-Authors: Lijia Zhou, Allix Mathieu, Xiaojun KuangAbstract:Lowering the operating temperature of solid oxide fuel cells (SOFCs) requires high performance oxide ion conductor electrolytes. Recently tetrahedra-based structures have been attracting considerable attention for oxide ion conductor development, among which the layered tetrahedral network Melilite structure appears particularly interesting owing to its remarkable capability to accommodate and transport interstitial oxide ions, compared with isolated tetrahedral anion structures. Stabilization and migration mechanisms of interstitial oxide ions in Melilites have been systematically investigated using local structural relaxation from both electrostatic Coulomb interaction and chemical bonding aspects based on atomic and electronic structures respectively using experimental and theoretical approaches. These reveal cationic size and chemical bonding effects on stabilization and migration mechanisms of interstitial oxide ions. Lately, full crystallization from glass, an innovative synthesis method, was employed to produce new metastable Melilite oxide ion conductors which are inaccessible using classic solid state reaction owing to cationic size effect. Finally, the thermal and chemical stability at low temperature and the high oxide ion conductivity of the best Melilite oxide ion conductors based on LaSrGa 3 O 7 are likely to provide real possibilities of applications of Melilite-type electrolytes in SOFCs and other related devices.
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Interstitial Oxide Ion Migration Mechanism in Aluminate Melilite La 1+ x Ca 1– x Al 3 O 7+0.5 x Ceramics Synthesized by Glass Crystallization
ACS Applied Energy Materials, 2019Co-Authors: Jiehua Wang, Aydar Rakhmatullin, Sandra Ory, Alberto Fernández-carrión, Xiaojun Kuang, Mathieu AllixAbstract:Gallate Melilite materials have attracted considerable interest as new interstitial oxide ion conducting electrolytes for solid oxide fuel cells for more than a decade. However, the preparation of aluminate Melilite materials as interstitial oxide ion conductors remains a challenge. Here, we show that interstitial oxide ion conducting aluminate Melilite materials La1+xCa1-xAl3O7+0.5x (x = 0-0.5) can be prepared via a full crystallization from bulk glass process. Rietveld refinements performed from combined neutron and synchrotron X-ray powder diffraction (NPD and SPD) data reveal multiple interstitial defect positions within the pentagonal ring, demonstrating the diversity of local structures around the oxygen interstitial defects in La La1+xCa1-xAl3O7+0.5x. Variable temperature solid-state Al-27 nuclear magnetic resonance (NMR) spectroscopy measurements demonstrate the existence of 5-coordinated AlO5 polyhedra and dynamic exchange processes between these 5-coordinated Al sites, representing the first example of evidence for the migration mechanism of interstitial oxide ions in Melilites by NMR. This latter involves framework and interstitial oxide ions, and is assisted by rotation and deformation of tetrahedra. These calculations reveal reduced mobility of interstitial oxide ions in aluminate tetrahedral network owing to its rigidity.
Mats Nygren - One of the best experts on this subject based on the ideXlab platform.
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Study on the solid solubility of Al in the Melilite systems R2Si3 − xAlxO3 + xN4 − x with R = Nd, Sm, Gd, Dy and Y
Journal of the European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.
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study on the solid solubility of al in the Melilite systems r2si3 xalxo3 xn4 x with r nd sm gd dy and y
Journal of The European Ceramic Society, 1995Co-Authors: P.l. Wang, Wei-ying Sun, Dongsheng Yan, Mats Nygren, Thommy EkströmAbstract:Abstract The solubility of aluminium in the nitrogen-containing Melilite structure has been studied by preparation of specimens of the general formula R 2 Si 3 − x Al x O 3 + x N 4 − x with R = Nd, Sm, Gd, Dy and Y by hot pressing and pressureless sintering techniques in the temperature interval 1600–1750 °C. For elements with large ionic radii, i.e. R = Nd and Sm, up to one Si can be replaced by Al, but the solubility limits in Melilite solid solutions decrease with decreasing the ionic radii. Consequently, yttrium-Melilite had the lowest observed aluminium solubility (x ≈ 0.6) in rare earth elements-Melilite solid solutions.