authors |
Wind, J; Sharma, N; Yaremchenko, AA; Kharton, VV; Blom, DA; Vogt, T; Ling, CD |
nationality |
International |
journal |
CHEMISTRY OF MATERIALS |
keywords |
BI2O3-NB2O5 SOLID-SOLUTION; BI2O3-TA2O5 SYSTEM; FLUORITE; BI3NBO7; PHASE; TEMPERATURE; MODULATION; CHEMISTRY; BI2O3-WO3 |
abstract |
Starting from a previously published stoichiometric model for the commensurate Type III phase in the (1 - x)Bi2O3 center dot xNb(2)O(5) system, Bi94Nb32O221 (x = 0.254), we have developed a crystal-chemical model of this phase across its solidsolution range 0.20 <= x <= 0.26. After using annular dark-field scanning transmission electron microscopy to identify the metal sites that support nonstoichiometry, we show that the maximum possible range of that nonstoichiometry is 0.198 <= x <= 0.262, perfectly consistent with the experimental result. Intersite cation defects on these sites provide some local coordinative flexibility with respect to the surrounding oxygen sublattice, but not enough to create continuous fluorite-like channels like those found in the high-temperature incommensurate Type II phase. This explains the reduced oxide-ionic conductivity of Type III compared to Type II at all temperatures and compositions, regardless of which phase is thermodynamically stable under those conditions. The solid-solution model shows that oxygen disorder and vacancies are both reduced as x increases, which also explains why Type III becomes relatively more stable, and why oxide ionic conductivity decreases, as x increases. |
publisher |
AMER CHEMICAL SOC |
issn |
0897-4756 |
year published |
2018 |
volume |
30 |
issue |
10 |
beginning page |
3387 |
ending page |
3394 |
digital object identifier (doi) |
10.1021/acs.chemmater.8b00846 |
web of science category |
Chemistry, Physical; Materials Science, Multidisciplinary |
subject category |
Chemistry; Materials Science |
unique article identifier |
WOS:000433403800026
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ciceco authors
impact metrics
journal analysis (jcr 2019):
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journal impact factor |
9.567 |
5 year journal impact factor |
10.102 |
category normalized journal impact factor percentile |
88.386 |
dimensions (citation analysis):
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altmetrics (social interaction):
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