Debye model

About: Debye model is a research topic. Over the lifetime, 7462 publications have been published within this topic receiving 133987 citations.

Elastocaloric effect in a textured polycrystalline Ni-Mn-In-Co metamagnetic shape memory alloy

Abstract: By direct measurements, the elastocaloric effect at various temperatures in a [001]-oriented Ni45.7Mn36.6In13.3Co5.1 metamagnetic shape memory polycrystal has been investigated. A reversible temperature change of ±3.5 K, due to the relatively low stress (100 MPa) induced martensitic transformation, was observed at room temperature. A theoretical analysis based on the Debye description has revealed that the adiabatic temperature change arising from the lattice vibration plays a dominant role in the large elastocaloric effect for Ni-Mn-In-Co alloys.

Thermoelectric Properties of Lead Chalcogenide Core–Shell Nanostructures

Abstract: We present the full thermoelectric characterization of nanostructured bulk PbTe and PbTe–PbSe samples fabricated from colloidal core–shell nanoparticles followed by spark plasma sintering. An unusually large thermopower is found in both materials, and the possibility of energy filtering as opposed to grain boundary scattering as an explanation is discussed. A decreased Debye temperature and an increased molar specific heat are in accordance with recent predictions for nanostructured materials. On the basis of these results we propose suitable core–shell material combinations for future thermoelectric materials of large electric conductivities in combination with an increased thermopower by energy filtering.

Multiple Converged Conduction Bands in K2Bi8Se13: A Promising Thermoelectric Material with Extremely Low Thermal Conductivity

Abstract: We report that K2Bi8Se13 exhibits multiple conduction bands that lie close in energy and can be activated through doping, leading to a highly enhanced Seebeck coefficient and a high power factor with elevated temperature. Meanwhile, the large unit cell, complex low symmetry crystal structure, and nondirectional bonding lead to the very low lattice thermal conductivity of K2Bi8Se13, ranging between 0.42 and 0.20 W m–1 K–1 in the temperature interval 300–873 K. Experimentally, we further support the low thermal conductivity of K2Bi8Se13 using phonon velocity measurements; the results show a low average phonon velocity (1605 ms–1), small Young’s modulus (37.1 GPa), large Gruneisen parameter (1.71), and low Debye temperature (154 K). A detailed investigation of the microstructure and defects was carried out using electron diffraction and transmission microscopy which reveal the presence of a K2.5Bi8.5Se14 minor phase intergrown along the side of the K2Bi8Se13 phase. The combination of enhanced power factor an...

Size effect of the resistivity of thin epitaxial gold films

Abstract: The temperature dependence of the electrical resistivity of thin, epitaxial, and flat (111)-oriented gold films with thickness between 2 and $50\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$ is investigated. The quality of these Au films is superior to epitaxial Au films grown on mica, therefore the investigation of well-defined thin films was possible. The experiments are analyzed within the frame of classical size-effect theories of the resistivity. It turns out that for thin films, the characteristic Debye temperature is strongly decreased as compared to the bulk value. In contrast to the more physically motivated approach of Soffer, the original model of Fuchs-Sondheimer describes the experimental data in a physically consistent way.

Surface Debye Temperatures of the (100), (111), and (110) Faces of Platinum

Abstract: The intensity of back‐diffracted low‐energy electrons (15–350 eV) from the clean (100), (111), and (110) surfaces of platinum single crystals was measured. From the temperature dependence of the (00) reflection in the range of 25°—700°C, the Debye—Waller factor and the root‐mean‐square displacements of surface atoms perpendicular to the surface planes were determined. The measured root‐mean‐square displacement 〈uz2〉½ was found to be a sensitive function of electron energy. The properties of the surface planes were determined from the intensity data taken at the lowest electron energy. Using the Debye model in the high‐temperature approximation, the Debye temperatures and the frequencies of lattice vibration were calculated. The root‐mean‐square displacement of surface platinum atoms perpendicular to the surface plane is about twice as great as that in the bulk. This effect gives rise to surface Debye temperatures which are much smaller (107°—118°K) than the bulk value (234°K).