X-Ray and23Na NMR Investigations on Na+– and Na+/La3+–β″-Al2O3Crystals

Köhler, Joachim; Balzer-Jöllenbeck, G.; Urland, Werner

doi:10.1006/jssc.1996.0119

Cited by 14 publications

(5 citation statements)

References 2 publications

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“…Therefore, only a few papers have reported the possibility of trivalent ion conduction; e.g. Ln 3+ −β‘‘-alumina, − β-LaNb 3 O 9 , LaAl 11 O 18 , and LaAl 12 O 18 N. , These papers, however, have only indicated a probability of trivalent cation conduction, and any trivalent ionic conduction in the solids were not directly and quantitatively demonstrated at all.…”

Section: Introductionmentioning

confidence: 99%

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

et al. 1998

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To realize a trivalent ion conduction in solids, the Sc 2 (WO 4 ) 3 -type structure was chosen on the basis of the mobile trivalent ions and the structure which reduces the electrostatic interaction between the framework and the mobile trivalent ionic species as much as possible. The typical conductivity of the rare earth tungstates R 2 (WO 4 ) 3 (R ) Sc, Y, and Er-Lu) with the Sc 2 (WO 4 ) 3 -type structure was found to be on the order of 10 -5 S cm -1 at 600 °C. Among the rare earth tungstates, Sc 2 (WO 4 ) 3 (σ 600°C ) 6.5 × 10 -5 S cm -1 , E a ) 44.1 kJ mol -1 ) was found to be the most suitable size for the ionic conduction with regard to the relation between the mobile ion radius and the lattice size. The rare earth ion conducting characteristics were investigated by means of the rare earth concentration cell measurements and dc electrolyses. The electromotive force measurements with the Sc-Y binary alloy and the yttrium tungsten bronze as the electrodes strongly suggest the possibility of the trivalent ion conduction of rare earths such as Sc 3+ and Y 3+ . Furthermore, by the dc electrolysis, the mobile species was clarified to be the rare earth ions Sc 3+ and Y 3+ in the rare earth tungstates with the Sc 2 (WO 4 ) 3 -type structure.

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Section: Introductionmentioning

confidence: 99%

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

et al. 1998

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“…In contrast, trivalent cations have been considered as an extremely poor choice for ionic migration because of high electrostatic interaction of these highly charged species with the surrounding atomic framework structure. Only a few papers have reported some possibilities of trivalent ion conduction, e.g., Ln 3+ -β‘‘-alumina − and β-LaNb 3 O 9 …”

Section: Introductionmentioning

confidence: 99%

“…Farrington et al − and Urland et al − have reported that Ln 3+ -β‘‘-alumina (Ln: rare earth), which was obtained by ionically exchanging the 3Na + site of Na + -β‘‘-alumina single crystal for Ln 3+ using molten salts such as nitrate or chloride, is a trivalent ion conductor, and the mechanism of the ionic conduction has been examined . The ionic exchange ratio from Na + to Ln 3+ in Na + -β‘‘-alumina has been described to be higher than 95%, while the total conductivity of the Ln 3+ -β‘‘-alumina decreased more than 3 orders of magnitude compared to that of pure Na + -β‘‘-alumina.…”

Section: Introductionmentioning

confidence: 99%

Trivalent Al³⁺ Ion Conduction in Aluminum Tungstate Solid

et al. 1997

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Ionic conduction of trivalent aluminum in solid aluminum tungstate, Al 2 (WO 4 ) 3 , has been directly and quantitatively demonstrated. Trivalent ions, especially for aluminum where the polarizability is considerably low, are strongly bonded in a crystal lattice and have been believed to be unlikely to exhibit migration in solids because of high electrostatic interaction with the surrounding skeleton structure. The material, Al 2 (WO 4 ) 3 , which has the Sc 2 (WO 4 ) 3 structure, was selected in order to reduce the interaction between the framework and the mobile species, Al 3+ , as much as possible. The ionic conduction characteristics of Al 2 (WO 4 ) 3 were investigated by means of electrolysis and electromotive force measurement by constructing an aluminum concentration cell. The typical electrical conductivity of Al 2 (WO 4 ) 3 was, approximately 2 × 10 -5 S cm -1 at 800 °C. The dc electrolysis data strongly support the conclusion that ionic Al 3+ is the mobile species in Al 2 (WO 4 ) 3 . By further electrochemical measurements, it was confirmed that the mobile species was aluminum ion in a trivalent state with no contribution due to electronic conduction. The ionic transference number was determined to be unity from the oxygen-air gas concentration cell and the aluminum concentration cell method.

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“…Typically, the migrating ions in solid electrolytes have been limited mono- or divalent ions. In a few cases, trivalent cation conduction has been claimed for such materials as Ln 3+ -β‘‘-alumina, − β-LaNb 3 O 9 , LaAl 11 O 18 , and LaAl 12 O 18 N . However, no clear and direct demonstration of specific trivalent ion conduction in these solids has been accomplished.…”

Section: Introductionmentioning

confidence: 99%

Trivalent Aluminum Ion Conducting Characteristics in Al₂(WO₄)₃ Single Crystals

Imanaka¹,

Tamura²,

Hiraiwa³

et al. 1998

Chem. Mater.

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Single crystals of the trivalent Al3+ ion conductor Al2(WO4)3 were grown by the Czochralski (CZ) method. The ionic conductivity in the a-, b-, and c-axis directions was determined and Al3+ ion conduction in the direction of the b-axis was concluded to be the most suitable pathway for ion migration in the tungstate grains. The ionic conductivities in the a- and c-axis directions were 0.3 and 10-2 times lower than the conductivity in the b-axis. Consistent with this observation, the lowest activation energy (E a) for Al3+ ion migration was obtained for the b-axis direction. The E a of the conductivity in the direction of the c-axis was almost comparable to that of the polycrystalline samples and the E a of the Al3+ ionic conduction in the grains of this material was explicitly verified to be controlled by the Al3+ ionic migration in the c-axis direction. The Al3+ ion conductivity of the polycrystalline sample was higher in the higher temperature region, indicating that the conductivity in the grain boundaries enhances the total Al3+ ion conductivity to a considerable extent. From the oxygen pressure dependencies of the electrical conductivity and the polarization behavior, the single crystals were demonstrated to be pure Al3+ ionic conductors showing an anisotropic ion conducting behavior.

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X-Ray and23Na NMR Investigations on Na+– and Na+/La3+–β″-Al2O3Crystals

Cited by 14 publications

References 2 publications

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

Trivalent Al³⁺ Ion Conduction in Aluminum Tungstate Solid

Trivalent Aluminum Ion Conducting Characteristics in Al₂(WO₄)₃ Single Crystals

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X-Ray and23Na NMR Investigations on Na+– and Na+/La3+–β″-Al2O3Crystals

Cited by 14 publications

References 2 publications

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc2(WO4)3-Type Structure

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc2(WO4)3-Type Structure

Trivalent Al3+ Ion Conduction in Aluminum Tungstate Solid

Trivalent Aluminum Ion Conducting Characteristics in Al2(WO4)3 Single Crystals

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Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

Trivalent Rare Earth Ion Conduction in the Rare Earth Tungstates with the Sc₂(WO₄)₃-Type Structure

Trivalent Al³⁺ Ion Conduction in Aluminum Tungstate Solid

Trivalent Aluminum Ion Conducting Characteristics in Al₂(WO₄)₃ Single Crystals