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Title: Charge Transport in the A 6 B 2 O 17 (A = Zr, Hf; B = Nb, Ta) Superstructure Series
The electrical properties of the entropy stabilized oxides: Zr6Nb2O17, Zr6Ta2O17, Hf6Nb2O17and Hf6Ta2O17were characterized. The results and the electrical properties of the products (i.e. ZrO2, HfO2, Nb2O5and Ta2O5) led us to hypothesize the A6B2O17family is a series of mixed ionic-electronic conductors. Conductivity measurements in varying oxygen partial pressure were performed on A6Nb2O17and A6Ta2O17.The results indicate that electrons are involved in conduction in A6Nb2O17while holes play a role in conduction of A6Ta2O17. Between 900 °C–950 °C, the charge transport in the A6B2O17system increases in Ar atmosphere. A combination of DTA/DSC and in situ high temperature X-ray diffraction was performed to identify a potential mechanism for this increase. In-situ high temperature X-ray diffraction in Ar does not show any phase transformation. Based on this, it is hypothesized that a change in the oxygen sub-lattice is the cause for the shift in high temperature conduction above 900 °C–950 °C. This could be:(i)Nb(Ta)4+- oxygen vacancy associate formation/dissociation,(ii)formation of oxygen/oxygen vacancy complexes(iii)ordering/disordering of oxygen vacancies and/or(iv)oxygen-based superstructure commensurate or incommensurate transitions. In-situ high temperature neutron diffraction up to 1050 °C is required to help elucidate the origins of this large increase in conductivity.  more » « less
Award ID(s):
2047084
PAR ID:
10509887
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Journal of the Electrochemical Society
Date Published:
Journal Name:
Journal of The Electrochemical Society
Volume:
171
Issue:
3
ISSN:
0013-4651
Page Range / eLocation ID:
034503
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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