Debye model

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

Linewidths and Thermal Shifts of Spectral Lines in Neodymium-Doped Yttrium Aluminum Garnet and Calcium Fluorophosphate

Abstract: Measurements in the 4.2-500\ifmmode^\circ\else\textdegree\fi{}K temperature range are reported of the widths, shapes, and thermal shifts of the 1.06- and 0.9-\ensuremath{\mu} lines of the ${\mathrm{Nd}}^{3+}$ ions in yttrium aluminum garnet (YAlG) and calcium fluorophosphate. The results are interpreted in terms of phonon-impurity interactions and static crystal strains. The obtained effective Debye temperature of YAlG is compared with the phonon density spectrum deduced from vibronic sidebands of the $R$ lines in YAlG: ${\mathrm{Cr}}^{3+}$. The $R\ensuremath{\rightarrow}{Z}_{5}$ and $R\ensuremath{\rightarrow}{Y}_{6}$ transitions of YAlG: Nd are observed to shift exceptionally to the higher energies with an increase of temperature. This is tentatively ascribed to the pushing effect of nearby higher-lying manifolds. Comparison of widths of several lines in YAlG: Nd at low temperatures reveals that the fluctuation of the second-degree crystal-field parameters contributes to the inhomogeneous linebroadenings. Discussions are also presented on the suitability of hard crystals with high phonon cutoff frequencies for the laser host materials.

Phonon thermal transport in noncrystalline materials

Abstract: The thermal conductivities of a borosilicate glass and a polycarbonate have been measured in the temperature range 0.04-60 K. Some samples contained well-defined holes to provide an additional source of phonon scattering. The results at low temperatures are consistent with the predictions of the Debye model using experimentally measured sound velocities. There is a sharp decrease in phonon mean free path with increasing frequency so that, at higher temperatures (the "plateau" region), thermal transport is provided predominantly by phonons having frequencies much less that $\ensuremath{\omega}\ensuremath{\simeq}\frac{4kT}{\ensuremath{\hbar}}$. For very small hole diameters, diffraction of thermal phonons occurs. The data are compared with theoretical models of thermal transport in noncrystalline materials.

Thermal Conductivity of II-VI Compounds and Phonon Scattering by Fe 2 + Impurities

Abstract: The thermal conductivities $\ensuremath{\kappa}$ of over twenty different single crystals of synthetic ZnO, ZnS, ZnSe, ZnTe, CdTe, and of natural, cubic ZnS have been measured from temperatures of 3 to 300 K The results for the undoped crystals above 30 K can be scaled using the parameter $\overline{M}\ensuremath{\delta}{\ensuremath{\Theta}}^{3}$, where $\overline{M}$, $\ensuremath{\delta}$, and $\ensuremath{\Theta}$ are the average mass, interatomic spacing, and Debye temperature, respectively A comparison of these results with those in the literature for BeO, CdS, CdSe, HgSe, HgTe, Si, Ge, GaAs, and InSb show that the same scaling parameter applies for most of them The compounds HgSe and HgTe exhibit anomalously low $\ensuremath{\kappa}$ values Crystals doped with ${\mathrm{Fe}}^{2+}$ show a resonant-type one-phonon scattering from the five low-lying energy levels of this $3{d}^{6}$ ion Group theory shows that the strongest scattering occurs for phonons of energy $2\ensuremath{\Delta}$, where $\ensuremath{\Delta}$ is the interlevel spacing of the ${\mathrm{Fe}}^{2+}$ ion