Phonon Density of States and Heat Capacity of La$$_{3-x}$$Te$$_4$$
- ORNL
- California Institute of Technology, Pasadena
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 $$~1.85 \leqslant T \leqslant 1200 \,$$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. The temperature dependence of the phonon DOS is captured satisfactorily by the quasiharmonic approximation.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Temperature Materials Lab. (HTML); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- DE-AC05-00OR22725
- OSTI ID:
- 1010982
- Journal Information:
- Physical Review B, Vol. 80, Issue 18; ISSN 1098--0121
- Country of Publication:
- United States
- Language:
- English
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