7-11 July 2014
Africa/Johannesburg timezone
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Novel Rattling Dynamics Explain Low Thermal Conductivity in Aluminium-Doped Potassium Tungstate Defect Pyrochlore

Presented by Dr. Elvis SHOKO on 10 Jul 2014 from 14:00 to 14:20
Type: Oral Presentation
Session: DPCMM1
Track: Track A - Division for Physics of Condensed Matter and Materials

Abstract

In a recent study, we reported an unusual quasielastic inelastic neutron scattering (INS) signal in the K analogue of the Al-doped series of cage compounds with the β-pyrochlore structure, AAl0.33W1.67O6 (A = K, Rb, Cs) [1]. We are studying this family of compounds because the rattling modes of the alkali metal atoms [2, 3] are similar to those found to enhance thermoelectric performance in both clathrates [4] and skutterudites [5]. This talk will discuss our recent thermal conductivity [6] and specific heat data in terms of the vibrational density of states calculated from ab initio molecular dynamics (MD) simulations validated against experimental INS spectra and show the significance of the novel K dynamics for these properties. I will conclude with a tentative sketch of the prospects of these compounds for thermoelectric development. References [1] E. Shoko, G. J. Kearley, V. K. Peterson, H. Mutka, M. M. Koza, J.-I. Yamaura, Z. Hiroi, G. J. Thorogood, submitted to Phys. Rev. B, ( arXiv:1310.8137). [2] K. Oshiba and T. Hotta, J. Phys. Soc. Jpn. 80, 094712 (2011). [3] J. Yamaura and Z. Hiroi, J. Phys. Soc. Jpn. 80, 054601 (2011), Z. Hiroi, J.-I. Yamaura and K. Hattori, J. Phys. Soc. Jpn. 81, 11012 (2012). [4] B. C. Sales, B. C. Chakoumakos, R. Jin, J. R. Thompson and D. Mandrus, Phys. Rev. B 63, 245113 (2001). [5] M. M. Koza, M. R. Johnson, R. Viennois, H. Mutka, L. Girard and D. Ravot, Nature Mater. 7, 805 (2008). [6] E. Shoko, V. K. Peterson, and G. J. Kearley, J. Appl. Phys. 115, 033703, (arXiv:1310.8382v2)

Award

No

Level

No

Supervisor

Prof. Daniel Joubert (daniel.joubert@wits.ac.za)

Paper

No

Place

Room: D Les 201


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