Enhanced Debye level in nano , , and NiSb: Nuclear inelastic spectroscopy on¹²¹ Sb

Abstract

The 121 Sb partial density of phonon states (DPS) in nanopowder antimonides were obtained with nuclear inelastic scattering on Zn 1+x Sb, FeSb 2 , and NiSb prepared by a wet chemistry route. The DPS is compared with the bulk counterpart. An increase of the Debye level indicative of a decrease of the isothermal speed of sound is systematically observed. This observation reveals that the decrease in speed of sound observed in nanostructured thermoelectric materials is not restricted to sintered nanocomposites.

Origin of the highly anisotropic thermal expansion of the semiconducting ZnSb and relations with its thermoelectric applications

“…Our measurements also support the presence of a peak around 48 cm −1 (6 meV) as seen by Belash et al [50] using INS on a sample containing a mixture of ZnSb and antimony, and by Claudio et al [51] on nanometric Zn 1+x Sb using antimony nuclear inelastic scattering. The peak at 84 cm −1 , located at the X-high symmetry point, mainly involves the Zn-atoms moving along the a-direction.…”

“…The peak at 84 cm À1 , located at the X-high symmetry point, mainly involves the Zn-atoms moving along the a-direction. Our measurements also support the presence of a peak around 48 cm À1 (6 meV) as seen by Belash et al 50 using INS on a sample containing a mixture of ZnSb and antimony, and by Claudio et al 51 on nanometric Zn 1+x Sb using antimony nuclear inelastic scattering. In addition, comparing our results on bulk ZnSb with those on Zn 4 Sb 3 , 30,52,53 the low energy peak in G(E) is located around the same energy ($5.5 meV) in both compounds.…”

Effect of nanocrystallinity on lattice dynamics in Bi2Te3based thermoelectrics

“…At least partially, this demonstrates that microscopic investigations of vibrational properties are scarce for this important material class. Published research based on inelastic neutron scattering (INS) or nuclear inelastic scattering (NIS) focused on as‐cast compounds or reported a reduction of the average phonon group velocity for nanowire ensembles and other nanocrystalline thermoelectrics . Herein, we demonstrate that nanocrystalline (NC) Bi 2 Te 3 based thermoelectrics exhibit densities of phonon states distinct from those in as‐cast (AC), coarse grained counterparts.…”

Anharmonicity and Effect of the Nanostructuring on the Lattice Dynamics of CrSi2

“…15−17 Complementary to these measurements, powder INS is the technique of choice to study the overall spectral density of phonons and is thus best suited to elaborate the impact of nanostructuring on the vibrational properties of a given material. 18,19 However, combining both techniques on specific thermoelectric materials has been only scarcely carried out to date. Herein, we report for the first time the experimental phonon dispersion curves of single-crystalline CrSi 2 and the generalized vibrational density of states (GVDOS) of bulk and nanocrystalline CrSi 2 .…”

“…In this context, inelastic neutron scattering (INS) is a powerful technique as it is able to map out the phonon properties in an extended range of the energy-momentum phase space. With INS on a single crystal specimen, one can map out the dispersion of the phonons, thereby setting a particular emphasis on the acoustic excitations and their possible coupling with low-energy, dispersionless optical modes. − Complementary to these measurements, powder INS is the technique of choice to study the overall spectral density of phonons and is thus best suited to elaborate the impact of nanostructuring on the vibrational properties of a given material. , However, combining both techniques on specific thermoelectric materials has been only scarcely carried out to date. Herein, we report for the first time the experimental phonon dispersion curves of single-crystalline CrSi 2 and the generalized vibrational density of states (GVDOS) of bulk and nanocrystalline CrSi 2 .…”