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|Title:||A (3+3)-Dimensional \"Hypercubic\" Oxide-Ionic Conductor: Type II Bi2O3-Nb2O5|
|Author:||Ling, Chris D.|
Blanchard, Peter E. R.
McIntyre, Garry J.
Yaremchenko, Aleksey A.
Kharton, Vladislav V.
Withers, Ray L.
|Keywords:||3-DIMENSIONAL INCOMMENSURATE MODULATION|
NEUTRON POWDER DIFFRACTION
|Publisher:||AMER CHEMICAL SOC|
|Abstract:||The high-temperature cubic form of bismuth oxide, delta-Bi2O3, is the best intermediate-temperature oxide-ionic conductor known. The most elegant way of stabilizing delta-Bi2O3 to room temperature, while preserving a large part of its conductivity, is by doping with higher valent transition metals to create wide solid-solutions fields with exceedingly rare and complex (3 + 3)-dimensional incommensurately modulated \"hypercubic\" structures. These materials remain poorly understood because no such structure has ever been quantitatively solved and refined, due to both the complexity of the problem and a lack of adequate experimental data. We have addressed this by growing a large (centimeter scale) crystal using a novel refluxing floating-zone method, collecting high-quality single-crystal neutron diffraction data, and treating its structure together with X-ray diffraction data within the superspace symmetry formalism. The structure can be understood as an \"inflated\" pyrochlore, in which corner-connected NbO6 octahedral chains move smoothly apart to accommodate the solid solution. While some oxide vacancies are ordered into these chains, the rest are distributed throughout a continuous three-dimensional network of wide delta-Bi2O3-like channels, explaining the high oxide-ionic conductivity compared to commensurately modulated phases in the same pseudobinary system.|
|Appears in Collections:||CICECO - Artigos|
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