Novel K rattling: a new route to thermoelectric materials?

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dc.contributor.authorShoko, Een_AU
dc.contributor.authorOkamoto, Yen_AU
dc.contributor.authorKearley, GJen_AU
dc.contributor.authorPeterson, VKen_AU
dc.contributor.authorThorogood, GJen_AU
dc.date.accessioned2022-04-21T07:22:36Zen_AU
dc.date.available2022-04-21T07:22:36Zen_AU
dc.date.issued2014-01-15en_AU
dc.date.statistics2022-04-06en_AU
dc.description.abstractWe have performed ab initio molecular dynamics simulations to study the alkali-metal dynamics in the Al-doped (KAl0.33W1.67O6 and RbAl0.33W1.67O6) and undoped (KW2O6 and RbW2O6) defect pyrochlore tungstates. The K atoms exhibit novel rattling dynamics in both the doped and undoped tungstates while the Rb atoms do not. The KAl0.33W1.67O6 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. © 2014 AIP Publishing LLC.en_AU
dc.identifier.articlenumber033703en_AU
dc.identifier.citationShoko, E., Okamoto, Y., Kearley, G. J., Peterson, V. K., & Thorogood, G. J. (2014). Novel K rattling: a new route to thermoelectric materials?. Journal of Applied Physics, 115(3), 033703. doi:10.1063/1.4861641en_AU
dc.identifier.issn1089-7550en_AU
dc.identifier.issue3en_AU
dc.identifier.journaltitleJournal of Applied Physicsen_AU
dc.identifier.urihttps://doi.org/10.1063/1.4861641en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/13059en_AU
dc.identifier.volume115en_AU
dc.language.isoenen_AU
dc.publisherAIP Publishingen_AU
dc.subjectThermoelectric materialsen_AU
dc.subjectThermal conductivityen_AU
dc.subjectPotassiumen_AU
dc.subjectRubidiumen_AU
dc.subjectPyrochloreen_AU
dc.subjectMoleculesen_AU
dc.titleNovel K rattling: a new route to thermoelectric materials?en_AU
dc.typeJournal Articleen_AU
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