Novel K rattling: A new route to thermoelectric materials?
Abstract
We have performed ab initio molecular dynamics simulations to study the alkali-metal dynamics in the Al-doped (KAl{sub 0.33}W{sub 1.67}O{sub 6} and RbAl{sub 0.33}W{sub 1.67}O{sub 6}) and undoped (KW{sub 2}O{sub 6} and RbW{sub 2}O{sub 6}) defect pyrochlore tungstates. The K atoms exhibit novel rattling dynamics in both the doped and undoped tungstates while the Rb atoms do not. The KAl{sub 0.33}W{sub 1.67}O{sub 6} experimental thermal conductivity curve shows an unusual depression between ∼50 K and ∼250 K, coinciding with two crossovers in the K dynamics: the first at ∼50 K, from oscillatory to diffusive, and the second at ∼250 K, from diffusive back to oscillatory. We found that the low-temperature crossover is a result of the system transitioning below the activation energy of the diffusive dynamics, whereas the high-temperature crossover is driven by a complex reconstruction of the local potential around the K atoms due to the cage dynamics. This leads to a hardening of the K potential with increasing temperature. This unusual reconstruction of the potential may have important implications for the interpretation of finite-temperature dynamics based on zero-temperature potentials in similar materials. The key result is that the novel K rattling, involving local diffusion, leads to a significant reductionmore »
- Authors:
-
- Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, New South Wales 2232 (Australia)
- Institute for Solid State Physics, University of Tokyo, Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)
- Publication Date:
- OSTI Identifier:
- 22275825
- Resource Type:
- Journal Article
- Journal Name:
- Journal of Applied Physics
- Additional Journal Information:
- Journal Volume: 115; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; ACTIVATION ENERGY; ALUMINIUM COMPOUNDS; COMPUTERIZED SIMULATION; DIFFUSION; DOPED MATERIALS; MOLECULAR DYNAMICS METHOD; PHONONS; POTASSIUM COMPOUNDS; POTENTIALS; RUBIDIUM COMPOUNDS; TEMPERATURE DEPENDENCE; THERMAL CONDUCTIVITY; THERMOELECTRIC MATERIALS; TUNGSTATES
Citation Formats
Shoko, Elvis, Kearley, Gordon J., Peterson, Vanessa K., Thorogood, Gordon J., and Okamoto, Y. Novel K rattling: A new route to thermoelectric materials?. United States: N. p., 2014.
Web. doi:10.1063/1.4861641.
Shoko, Elvis, Kearley, Gordon J., Peterson, Vanessa K., Thorogood, Gordon J., & Okamoto, Y. Novel K rattling: A new route to thermoelectric materials?. United States. https://doi.org/10.1063/1.4861641
Shoko, Elvis, Kearley, Gordon J., Peterson, Vanessa K., Thorogood, Gordon J., and Okamoto, Y. 2014.
"Novel K rattling: A new route to thermoelectric materials?". United States. https://doi.org/10.1063/1.4861641.
@article{osti_22275825,
title = {Novel K rattling: A new route to thermoelectric materials?},
author = {Shoko, Elvis and Kearley, Gordon J. and Peterson, Vanessa K. and Thorogood, Gordon J. and Okamoto, Y.},
abstractNote = {We have performed ab initio molecular dynamics simulations to study the alkali-metal dynamics in the Al-doped (KAl{sub 0.33}W{sub 1.67}O{sub 6} and RbAl{sub 0.33}W{sub 1.67}O{sub 6}) and undoped (KW{sub 2}O{sub 6} and RbW{sub 2}O{sub 6}) defect pyrochlore tungstates. The K atoms exhibit novel rattling dynamics in both the doped and undoped tungstates while the Rb atoms do not. The KAl{sub 0.33}W{sub 1.67}O{sub 6} experimental thermal conductivity curve shows an unusual depression between ∼50 K and ∼250 K, coinciding with two crossovers in the K dynamics: the first at ∼50 K, from oscillatory to diffusive, and the second at ∼250 K, from diffusive back to oscillatory. We found that the low-temperature crossover is a result of the system transitioning below the activation energy of the diffusive dynamics, whereas the high-temperature crossover is driven by a complex reconstruction of the local potential around the K atoms due to the cage dynamics. This leads to a hardening of the K potential with increasing temperature. This unusual reconstruction of the potential may have important implications for the interpretation of finite-temperature dynamics based on zero-temperature potentials in similar materials. The key result is that the novel K rattling, involving local diffusion, leads to a significant reduction in the thermal conductivity. We suggest that this may open a new route in the phonon engineering of cage compounds for thermoelectric materials, where the rattlers are specifically selected to reduce the lattice thermal conductivity by the mechanism of local diffusion.},
doi = {10.1063/1.4861641},
url = {https://www.osti.gov/biblio/22275825},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 3,
volume = 115,
place = {United States},
year = {Tue Jan 21 00:00:00 EST 2014},
month = {Tue Jan 21 00:00:00 EST 2014}
}