Low-temperature heat capacity and localized vibrational modes in natural and synthetic tetrahedrites

Lara‐Curzio, Edgar; May, Andrew F.; Delaire, Olivier; McGuire, Michael A.; Lu, Xu; Liu, Cheng Yun; Case, Eldon D.; Morelli, Donald T.

doi:10.1063/1.4878676

Cited by 72 publications

(63 citation statements)

References 7 publications

(16 reference statements)

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“…The Einstein-like character of the trigonal Cu vibrations also leads to a definite enhancement in the low-temperature heat capacity, as previously reported. 52 This view is also supported by the first-order character of the structural phase transition observed in our specific heat and diffraction measurements. The strongly anharmonic character of the trigonal Cu vibrations is manifest in the pronounced softening on cooling reported here, and was also inferred from an anharmonic refinement of the atomic displacement parameters from single-crystal x-ray diffraction.…”

Section: Lattice Dynamicssupporting

confidence: 72%

Structural phase transition and phonon instability inCu12Sb4S13

et al. 2016

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A structural phase transition has been discovered in the synthetic tetrahedrite Cu12Sb4S13 at approximately 88 K. Upon cooling, the material transforms from its known cubic symmetry to a tetragonal unit cell that is characterized by an in-plane ordering that leads to a doubling of the unit cell volume. Specific heat capacity measurements demonstrate a hysteresis of more than two degrees in the associated anomaly. Similar hysteresis was observed in powder x-ray diffraction measurements that also indicate a coexistence of the two phases, and together these results suggest a first order transition. This structural transition coincides with a recently-reported metal-insulator transition, and the structural instability is related to the very low thermal conductivity κ in these materials. Inelastic neutron scattering was used to measure the phonon density of states in Cu12Sb4S13 and Cu10Zn2Sb4S13, both of which possess a localized, low-energy phonon mode associated with strongly anharmonic copper displacements that suppress κ. In Cu12Sb4S13, signatures of the phase transition are observed in the temperature dependence of the localized mode, which disappears at the structural transition. In contrast, in the cubic Zn-doped material the mode is at slightly higher-energy but observable for all temperatures, though it softens upon cooling.

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Section: Lattice Dynamicssupporting

confidence: 72%

Structural phase transition and phonon instability inCu12Sb4S13

et al. 2016

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“…for Cu 11 NiSb 4 S 13 from diffraction studies. 5 Although our Debye temperature is much smaller than 500 K for Cu 10 Zn 2 Sb 4 S 13 from heat capacity studies, 22 our Debye heat capacity is close to what was obtained in that work (∼2.75 k B ). In addition, our mean speed of sound is close to the hydrodynamic sound velocity (2668 m/s) expected from the bulk modulus.…”

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confidence: 60%

First-principles studies of atomic dynamics in tetrahedrite thermoelectrics

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et al. 2016

APL Materials

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“…In addition, we can suggest that the highly anisotropic thermal motion of Cu(2) atoms ( Fig. 1) in pseudo-trigonal coordination [20] may lead to low-energy vibrations in the stiff network, as it was recently reported in Cu 12 Sb 4 S 13 tetrahedrites [4,36]. Such low-energy vibrations are expected to interact with the heat-carrying phonon and/or conduction carrier as it does in caged compounds, skutterudites [37] and clathrates [38].…”

Section: Thermoelectric Propertiesmentioning

confidence: 76%