Lattice vibrations of glasses

Pohl, Robert Wichard

doi:10.1016/j.jnoncrysol.2006.01.102

Cited by 20 publications

(5 citation statements)

References 17 publications

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“…The discrepancy between the measured and predicted thermal conductivity at low temperatures was also observed by Cahill and Pohl for amorphous silica. It was attributed to the fact that the Cahill–Pohl model does not include energy transport by phonons with long mean free path whose contributions become important at low temperatures in both amorphous and strongly disordered polycrystalline solids. , …”

Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Highly-Ordered Mesoporous Titania Thin Films from 30 to 320 K

et al. 2011

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ABSTRACT:11 This paper reports the cross-plane thermal conductivity of highly ordered amorphous and crystalline templated mesoporous titania 12 thin films measured by the 3ω method from 30 to 320 K. Both solÀgel and nanocrystal-based films were synthesized by evaporation-13 induced self-assembly, with average porosity of 30% and 35%, respectively. The pore diameter ranged from 14 to 25 nm. The size of 14 crystalline domains in polycrystalline mesoporous films were 12À13 nm, while the nanocrystals in the nanocrystal-based film were 15 9 nm in diameter. At high temperatures, the thermal conductivity of amorphous dense and mesoporous films showed similar trends 16 with respect to temperature. This was attributed to the fact that the presence of pores had a purely geometrical effect by reducing the 17 cross-sectional area through which heat can diffuse. By contrast, the thermal conductivity of polycrystalline dense and mesoporous 18 films behaves differently with temperature due to phonon scattering by pores and crystalline nanosize domains. In addition, at low 19 temperatures, the presence of pores caused the thermal conductivity of mesoporous films to be less temperature dependent than 20 their dense counterparts. Despite its crystallinity, the thermal conductivity of the nanocrystal-based film was about 40% less than that 21 of the polycrystalline mesoporous films. This was mainly attributed to its larger porosity, smaller crystal size, and strong phonon 22 scattering at the poorly interconnected nanocrystal boundaries. These results suggest various ways to control the thermal 23 conductivity of mesoporous materials for various applications.

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Section: Resultsmentioning

confidence: 99%

Thermal Conductivity of Highly-Ordered Mesoporous Titania Thin Films from 30 to 320 K

et al. 2011

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“…Presumably, the heat carrying acoustic phonons of the KBr host lattice are resonantly scattered by these tunnel states, which behave similarly to the tunneling states in a glass and produces the T 2 dependence at low T . At higher temperatures, the random local stresses associated with the substitution of the elongated CN – for Br – presumably produce lattice vibrations that are in some ways glass‐like . Note that, as illustrated in Figure , doubling the KCN content from x ∼ 0.2 to x ∼ 0.4 does not appreciably affect the thermal conductivity, which is glass‐like in both cases.…”

Section: Extrinsic Structural Disorder In Crystalsmentioning

confidence: 89%

“…The introduction of vacancies and interstitial atoms in these and related materials presumably also produces random stresses throughout the crystal. The chemical disorder and random stresses in turn may induce lattice vibrations that are similar to those in a glass . This contrasts with simple atomic site substitution, which can be viewed as a perturbation to the lattice dynamics of the parent crystal.…”

Section: Extrinsic Structural Disorder In Crystalsmentioning

confidence: 99%

Inorganic Crystals with Glass‐Like and Ultralow Thermal Conductivities†

Beekman

Cahill

2017

Crystal Research and Technology

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The ability to control the transport of thermal energy is critical in a wide variety of technologies. At the same time, understanding the underlying microscopic mechanisms of thermal transport in solids continues to be a central goal of condensed matter and materials physics, with many persistent challenges and unanswered questions. One of the remarkable findings has been the observation that some crystalline materials have very low, glass-like thermal conductivities despite long-range order in the arrangement of the atoms in their structure. Although examples with such unusual behavior were initially rare, the number of crystalline materials known to have glass-like thermal conductivities has grown significantly in the past two decades. Moreover, some fully dense inorganic solids have recently been discovered that possess ultralow thermal conductivities below the so-called glass limit. In this review, we use several specific examples to highlight the salient structural and lattice dynamical features of these intriguing "glass-like crystals," focusing on current understanding of the microscopic mechanisms that cause these crystals to conduct heat like a glass. The study of such materials continues to push our understanding of heat transport in solids and the roles that chemical bonding and structural order and disorder play in thermal transport processes.

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“…It has been reported that all amorphous materials present very similar temperature dependence for the thermal conductivity, suggesting a universal behavior, whose origin is not completely understood [20,21]. In fact, the temperature dependence of the thermal conductivity and the specific heat of non-crystalline solids differ markedly from that of crystalline ones, and despite the intensive investigation [22] on the subject a satisfactory microscopic description of the origin of the mentioned difference has not yet been given.…”

Section: Discussionmentioning

confidence: 99%