A (3+3)-Dimensional

authors	Ling, CD; Schmid, S; Blanchard, PER; Petricek, V; McIntyre, GJ; Sharma, N; Maljuk, A; Yaremchenko, AA; Kharton, VV; Gutmann, M; Withers, RL
nationality	International
journal	JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
keywords	3-DIMENSIONAL INCOMMENSURATE MODULATION; NEUTRON POWDER DIFFRACTION; SOLID-SOLUTION; FUEL-CELLS; STRUCTURAL-PROPERTIES; BISMUTH SESQUIOXIDE; SUPERSPACE GROUPS; NODAL SURFACES; SYSTEM; PHASE
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.
publisher	AMER CHEMICAL SOC
issn	0002-7863
year published	2013
volume	135
issue	17
beginning page	6477
ending page	6484
digital object identifier (doi)	10.1021/ja3109328
web of science category	Chemistry, Multidisciplinary
subject category	Chemistry
unique article identifier	WOS:000318469100022