Browsing by Author "Dong, ST"

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    Lattice dynamics of KxRhO2 single crystals
    (AIP Publishing, 2015-08-05) Zhang, BB; Zhang, NN; Dong, ST; Lv, YY; Chen, YB; Yao, SH; Zhang, ST; Gu, ZB; Zhou, J; Guedes, I; Yu, DH; Chen, YF
    A series of crystals KxRhO2 (x = 0.72, 0.63, 0.55, 0.39, and 0.24) have been synthesized and their vibrational properties have been studied by first principles calculations, Raman spectroscopy, and inelastic neutron scattering. The measured vibrational spectra of KxRhO2 for x = 0.72 and 0.63 are consistent with the theoretical prediction for the stoichiometric KRhO2. For samples with x = 0.55, 0.39 and 0.24, extra vibrational modes have been observed and they are believed to be due to the symmetry reduction and the loss of translational symmetry induced by K disorder. The good agreement was found for the phonon density of states among the Raman spectroscopic observations, inelastic neutron scattering and the first principles calculations, as an evidence for the generation of structure disorder by K deficiency. © 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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    The physical mechanism of extremely low thermal conductivity of BiCuTeO and BiCuSeO revealed by inelastic neutron and Raman spectroscopy
    (Elsevier, 2020-06-15) Lin, D; Dong, ST; Zhang, YY; Lv, YY; Zhou, J; Chen, YB; Mole, RA; Yao, SH; Yu, DH
    Layered structure BiCuSeO-based compounds have extremely low thermal conductivity about ∼0.5–0.8 W/m·K, and the corresponding physical origin has been extensively studied by the first-principles calculations. Here we experimentally revealed the physical mechanism of extremely low thermal conductivity in BiCuSeO and BiCuTeO through inelastic neutron and Raman scattering spectroscopy. Generalized phonon density of states (PDOS) characterized by inelastic neutron scattering reveals that the average acoustic-phonon velocities of BiCuSeO and BiCuTeO are as low as 2104 and 1547 m/s, respectively, which are lower than most of normal materials (∼3000 m/s), and strong anharmonic effect in BiCuSeO and BiCuTeO. Strongly anharmonic effect is also verified by the large Grüneisen constant of specific optical-phonon mode of BiCuSeO and BiCuTeO (∼6.7 in BiCuTeO). The calculated thermal conductivities of BiCuSeO and BiCuTeO by phenomenological thermal conductivity formula, under approximation of the relaxation-time as minimum quasi-particle lifetime of optical-phonon mode, are close to experimental values. Our work sheds more light on the physical mechanism of extremely low thermal conductivity in these compounds. © 2020 Elsevier B.V.