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Showing 1 to 15 of 15 for “"phonon mean free path"”.
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Experimental and numerical investigation of phonon mean free path distribution
Knowledge of phonon mean free path (MFP) distribution is critically important to engineering size effects. Phenomenological models of phonon relaxation times can give us some sense about the mean free path distribution, but they are not accurate. Further improvement of thermoelectric performance …
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Experimental studies of the thermoelectric properties of microstructured and nanostructured lead salts
… Thermal conductivity can be reduced by boundary phonon scattering for materials in which the grain size is comparable to or less than the phonon mean free path. Samples of PbTe and PbSe were prepared by hot pressing nano-size and micro-sized particles and the thermal diffusivity, the Seebeck …
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Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon
… been some lingering questions surrounding the phonon mean free path and importance of different polarizations. This research investigates phonon transport in bulk crystalline silicon using molecular dynamics and lattice dynamics. The interactions are modeled with the environment dependent …
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Thermal transport in graphene-based nanostructures and other two-dimensional materials
… or devices with dimensions comparable to the phonon mean free path (MFP). Here, we investigated thermal transport in graphene-based nanostructures and several other 2D materials. First, we measured heat conduction in nanoscale graphene by a substrate-supported thermometry platform. Short, …
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Variational approach to solving the phonon Boltzmann transport equation for analyzing nanoscale thermal transport experiments
… at the nanoscale. We model the heat flow due to phonons (crystal lattice vibrations), the dominant heat carriers in semiconductors and dielectrics, by solving the Boltzmann transport equation (BTE) to develop an understanding of nondiffusive thermal transport and its dependence on the system …
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Low Temperature Behavior of Potassium and Sodium-Silicate Glasses
… glass transition temperature, mass density, phonon velocity, and concentration and density fluctuations. The results of this study have provided further support for an empirical relationship between the low-temperature phonon mean free path and T(,g). This seems to indicate P (PROPORTIONAL) …
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Electron thermal conductivity of thin films of strong-coupling superconductors and of superconductors containing rare earth impurities
… at liquid helium temperatures, and therefore the phonon mean free path in these films was very short. Consequently, the phonons contributed very little to the thermal conductivity. The experimentally determined thermal conductivity was therefore due almost entirely to the conduction of heat by the …
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Low temperature anomalies in niobium, vanadium and tantalum
… the thermal conductivity. In Nb doped with D the phonon mean free path exhibits a minimum which occurs at the same temperature at which a deuterium related anomaly has been observed in the specific heat. Phonon scattering caused by the addition of H to Nb or Ta is complicated by the presence of …
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Anderson localization of thermal phonons : anomalous heat conduction in disordered superlattices
… devices, thermal energy is carried by phonons, the quantized excitation of atomic vibrations. These phonons scatter with impurities, electrons, grain boundaries, and other phonons. At a sufficiently large scale, phonon dynamics can be approximated as a Brownian random walk, leading to …
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Optical characterization of complex mechanical and thermal transport properties
… grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked to structural relaxation in supercooled liquids. In ISS measurements, short optical pulses are crossed to produce a periodic excitation profile in or at the …
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Optical transient grating measurements of micro/nanoscale thermal transport and mechanical properties
… transient grating technique was used to study phonon mediated thermal transport in bulk and nanostructured semiconductors and surface wave propagation in a monolayer of micron sized spheres. In the transient grating technique two picosecond pulses are crossed to generate a spatially periodic …
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The Pressure Dependence of the Low Temperature Thermal Properties of an Amorphous Polymer
… Tunneling Model and the existence of phonons can account for the observed behavior, which is indicative of localized two-level excitations. For temperatures in the range 1 K-10 K there is no widely accepted model to explain the existence of an additional set of vibrational modes or the …
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The pressure dependence of the low-temperature thermal properties of an amorphous polymer
… Tunneling Model and the existence of phonons can account for the observed behavior, which is indicative of localized two-level excitations. For temperatures in the range 1 K- 10 K there is no widely accepted model to explain the existence of an additional set of vibrational modes or …
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Quantum Critical Ferroelectricity and Emergent Phenomena in KTaO3 and SrTiO3
… at temperatures below the minimum in L(T). The phonon mean free path l_ph in KTaO3 is derived from data on thermal conductivity and specific heat and literature values of the sound velocity vs, showing a peculiar plateau of l_ph ≈ 0.6 μm in a window of 10-22.5K before increasing rapidly to …
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Transport and thermodynamic studies of the superconductors A3T4Sn13 and YFe2Ge2
… Although the superconductivity is believed to be phonon-mediated with s-wave pairing symmetry, an unusual second-order structural transition makes this material family fascinating to study. Whether this structural transition is a result of three distortions with perpendicular wavevectors resulting …