Journal ArticleDOI
Thermal diffusivity of electrical insulators at high temperatures: Evidence for diffusion of bulk phonon-polaritons at infrared frequencies augmenting phonon heat conduction
TLDR
In this paper, the authors explore the possibility that the thermal diffusivity of an electrical insulator could include both a contribution of lattice phonons (the FT−G term) and a contribution from diffusive bulk phonon-polaritons (BPP) at infrared (IR) frequencies (the HT term).Abstract:
We show that laser-flash analysis measurements of the temperature (T) dependence of thermal diffusivity (D) for diverse non-metallic (e.g., silicates) single-crystals is consistently represented by D(T) = FT−G + HT above 298 K, with G ranging from 0.3 to 2, depending on structure, and H being ∼10−4 K−1 for 51 single-crystals, 3 polycrystals, and two glasses unaffected by disorder or reconstructive phase transitions. Materials exhibiting this behavior include complex silicates with variable amounts of cation disorder, perovskite structured materials, and graphite. The high-temperature term HT becomes important by ∼1300 K, above which temperature its contribution to D(T) exceeds that of the FT−G term. The combination of the FT−G and HT terms produces the nearly temperature independent high-temperature region of D previously interpreted as the minimal phonon mean free path being limited by the finite interatomic spacing. Based on the simplicity of the fit and large number of materials it represents, this finding has repercussions for high-temperature models of heat transport. One explanation is that the two terms describing D(T) are associated with two distinct microscopic mechanisms; here, we explore the possibility that the thermal diffusivity of an electrical insulator could include both a contribution of lattice phonons (the FT−G term) and a contribution of diffusive bulk phonon-polaritons (BPP) at infrared (IR) frequencies (the HT term). The proposed BPP diffusion exists over length scales smaller than the laboratory sample sizes, and transfers mixed light and vibrational energy at a speed significantly smaller than the speed of light. Our diffusive IR-BPP hypothesis is consistent with other experimental observations such as polarization behavior, dependence of D on the number of IR peaks, and H = 0 for Ge and Si, which lack IR fundamentals. A simple quasi-particle thermal diffusion model is presented to begin understanding the contribution from bulk phonon-polaritons to overall heat conduction.read more
Citations
More filters
a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.
TL;DR: In this article, it was shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions).
Journal ArticleDOI
Transport properties of glassy and molten lavas as a function of temperature and composition
Anne M. Hofmeister,Alexander Sehlke,Alexander Sehlke,Geoffroy Avard,Anthony J. Bollasina,Geneviève Robert,Geneviève Robert,Alan G. Whittington +7 more
TL;DR: In this article, the authors measured thermal diffusivity (D), heat capacity (CP), and viscosity (η) for 12 remelted natural lavas and 4 synthetic glasses and melts, ranging in composition from leucogranite to low-silica basalt, and calculate their thermal conductivity.
Journal ArticleDOI
Temperature-dependent thermal transport properties of carbonate minerals and rocks
TL;DR: In this article, the authors measured thermal diffusivity of a suite of carbonate minerals and rocks using laser flash analysis at temperatures from ~300 K up to ~1000 K, with the strongest drop occurring in the interval ~300-500 K.
Book ChapterDOI
Thermal Conductivity of the Earth
TL;DR: In this article, measurements and theory of heat transport properties (thermal conductivity, k, and thermal diffusivity, D ) of electric insulators that are partially transparent to light (i.e., most minerals in Earth's mantle).
Journal ArticleDOI
Temperature dependence of thermal diffusivity and conductivity for sandstone and carbonate rocks
Sheqiang Miao,Yongsheng Zhou +1 more
TL;DR: In this paper, the temperature dependence of the thermal diffusivity (D) of dolomite, limestone, Carrara marble, and four types of sandstone was studied using the laser flash technique, which is accurate (± 2%) and isolates the lattice component from the direct radiative transfer, at temperatures up to 973 K.
References
More filters
Journal ArticleDOI
Thermal Barrier Coatings for Gas-Turbine Engine Applications
TL;DR: In this article, the structure, properties, and failure mechanisms of thermal barrier coatings (TBCs) are reviewed, together with a discussion of current limitations and future opportunities.
Journal ArticleDOI
Flash Method of Determining Thermal Diffusivity, Heat Capacity, and Thermal Conductivity
TL;DR: In this paper, a high-intensity short-duration light pulse is absorbed in the front surface of a thermally insulated specimen, and the resulting temperature history of the rear surface is measured by a thermocouple and recorded with an oscilloscope and camera.
Journal ArticleDOI
Lower limit to the thermal conductivity of disordered crystals
TL;DR: These measurements support the claim that the lattice vibrations of these disordered crystals are essentially the same as those of an amorphous solid, based on a model originally due to Einstein.
Journal ArticleDOI
Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals
TL;DR: In this paper, it was shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions).
a Quantum-Mechanical Theory of the Contribution of Excitons to the Complex Dielectric Constant of Crystals.
TL;DR: In this article, it was shown that the ordinary semiclassical theory of the absorption of light by exciton states is not completely satisfactory (in contrast to the case of absorption due to interband transitions).