Department of Materials Science and Engineering, University of Wisconsin, Madison, WI 53706, USA
Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695, USA; Department of Physics, North Carolina State University, Raleigh, NC 27695, USA
The ordered structure A2B2O6O’ in pyrochlores engenders twin rows of inequivalent anion sublattices each centred on alternating cations. While it is known that cation antisite disorder augments the ionic conductivity by several orders of magnitude, the local cation environment around the anions and the dynamic anion reordering during the cation disordering are not well-elucidated. Using atomistic simulations on Gd2Zr2O7, we first show that the anions engage in concerted hops to the neighbouring tetrahedral sites mostly along with the $$\langle$$1 0 0$$\rangle$$ direction while completely avoiding the octahedral sites. While the initially vacant 8asites start accommodating oxygen ions with increasing cation disorder, they show noticeable reluctance even at significant levels of disorder. We have also tracked both the distribution of available oxygen sites following random cation disorder, which is dependent only on cation disordering, and the probability of occupation of these sites. Interestingly, the available oxygen sites show a non-monotonic dependence on the number of B ions in the nearest neighbouring shell while the occupation probability of all the available oxygen sites increases monotonically. A tetrahedral oxygen site thus has a better probability of being occupied when it has a greater number of second neighbour B ions.
This article is part of the Theo Murphy meeting issue 'Understanding fast-ion conduction in solid electrolytes'.
Annamareddy, Ajay and Eapen, Jacob. "Decoding ionic conductivity and reordering in cation-disordered pyrochlores." Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences, vol. 379, no. 2211, Oct. 2021. https://doi.org/10.1098/rsta.2019.0452
Annamareddy, Ajay, & Eapen, Jacob (2021). Decoding ionic conductivity and reordering in cation-disordered pyrochlores. Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences, 379(2211). https://doi.org/10.1098/rsta.2019.0452
Annamareddy, Ajay, and Eapen, Jacob, "Decoding ionic conductivity and reordering in cation-disordered pyrochlores," Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences 379, no. 2211 (2021), https://doi.org/10.1098/rsta.2019.0452
@article{osti_1979595,
author = {Annamareddy, Ajay and Eapen, Jacob},
title = {Decoding ionic conductivity and reordering in cation-disordered pyrochlores},
annote = {The ordered structure A2B2O6O’ in pyrochlores engenders twin rows of inequivalent anion sublattices each centred on alternating cations. While it is known that cation antisite disorder augments the ionic conductivity by several orders of magnitude, the local cation environment around the anions and the dynamic anion reordering during the cation disordering are not well-elucidated. Using atomistic simulations on Gd2Zr2O7, we first show that the anions engage in concerted hops to the neighbouring tetrahedral sites mostly along with the $\langle$1 0 0$\rangle$ direction while completely avoiding the octahedral sites. While the initially vacant 8asites start accommodating oxygen ions with increasing cation disorder, they show noticeable reluctance even at significant levels of disorder. We have also tracked both the distribution of available oxygen sites following random cation disorder, which is dependent only on cation disordering, and the probability of occupation of these sites. Interestingly, the available oxygen sites show a non-monotonic dependence on the number of B ions in the nearest neighbouring shell while the occupation probability of all the available oxygen sites increases monotonically. A tetrahedral oxygen site thus has a better probability of being occupied when it has a greater number of second neighbour B ions. This article is part of the Theo Murphy meeting issue 'Understanding fast-ion conduction in solid electrolytes'.},
doi = {10.1098/rsta.2019.0452},
url = {https://www.osti.gov/biblio/1979595},
journal = {Philosophical Transactions of the Royal Society. A, Mathematical, Physical and Engineering Sciences},
issn = {ISSN 1364-503X},
number = {2211},
volume = {379},
place = {United States},
publisher = {The Royal Society Publishing},
year = {2021},
month = {10}}