Delaire, O. and May, A. F. and McGuire, M. A. and Porter, W. D. and Lucas, M. S. and Stone, M. B. and Abernathy, D. L. and Ravi, V. A. and Firdosy, S. A. and Snyder, G. J. (2009) Phonon density of states and heat capacity of La_(3−x)Te_4. Physical Review B, 80 (18). Art. No. 184302 . ISSN 1098-0121 http://resolver.caltech.edu/CaltechAUTHORS:20100104-091911957
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The phonon density of states (DOS) of La_(3−x)Te_4 compounds (x=0.0,0.18,0.32) was measured at 300, 520, and 780 K, using inelastic neutron scattering. A significant stiffening of the phonon DOS and a large broadening of features were observed upon introduction of vacancies on La sites (increasing x). Heat-capacity measurements were performed at temperatures 1.85 ≤ T ≤ 1200 K and were analyzed to quantify the contributions of phonons and electrons. The Debye temperature and the electronic coefficient of heat capacity determined from these measurements are consistent with the neutron-scattering results, and with previously reported first-principles calculations. Our results indicate that La vacancies in La_(3−x)Te_4 strongly scatter phonons and this source of scattering appears to be independent of temperature. The stiffening of the phonon DOS induced by the introduction of vacancies is explained in terms of the electronic structure and the change in bonding character. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation.
|Additional Information:||© 2009 American Physical Society. Received 25 August 2009; published 19 November 2009. We thank David Singh for providing us with the numerical data for the electronic DOS of La3Te4 published in Ref. 27, and for helpful discussions. We thank Rebecca A. Mills for help with the neutron-scattering furnace. This work was partially supported by the Division of Materials Science and Engineering, Basic Energy Sciences, U.S. DOE. Work performed at the California Institute of Technology was done with the assistance of the Jet Propulsion Laboratory, under a contract with the National Aeronautics and Space Administration. The Research at Oak Ridge National Laboratory’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. DOE. High-temperature calorimetry measurements were conducted at Oak Ridge National Laboratory’s High Temperature Materials Laboratory, sponsored by the U. S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. This work benefitted from DANSE software developed under NSF under Award No. DMR-0520547.|
|Subject Keywords:||band structure; bonds (chemical); Debye temperature; lanthanum alloys; neutron diffraction; phonons; specific heat; tellurium alloys; vacancies (crystal)|
|Classification Code:||PACS numbers: 63.20.e, 61.05.fg, 65.40.Ba, 72.20.Pa|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||04 Jan 2010 19:35|
|Last Modified:||26 Dec 2012 11:39|
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