Study of phonon-dislocation interaction in LiF and KCl crystals

A knowledge of dislocations is essential for an understanding of many of the physical and mechanical properties of crystalline solids. The low-temperature thermal conductivity of electrically insulating crystals is strongly influenced by dislocations. Measurement of the lattice thermal conductivity, therefore, provides a useful tool for the study of phonon-dislocation interaction. In this thesis, thermal conductivity measurements on plastically deformed LiF and KCl crystals are discussed. LiF crystals were deformed in such a way that four slip systems were activated, in a hope to better understand the frequencydependence of the phonon-dislocation interaction. The results of measurements on LiF samples support the conclusion that phonons are scattered by dislocations through dynamic processes, in agreement with previous measurements. Yet, some fraction of phonons still have long mean-free-paths. Numerical calculations for the mean-free-paths assuming dynamic scattering processes and including phonon focusing effects are in fair agreement with experiments made at low temperatures. Our thermal conductivity measurements on KCl crystals indicate that , at temperatures below 2.0 K, all phonon modes are strongly scattered by dislocations. Heat-pulse measurements on KCl samples support this interpretation. 1-irradiation restores the thermal conductivity of the deformed KCl samples, suggesting that the phonon-dislocation interaction in KCl also is dynamic in nature. The experimental results are compared with numerical calculations assuming dynamic scattering processes. For small dislocation densities, there is reasonable agreement. However, the agreement is poor for heavily deformed samples.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2011

Author dc:creator

• Yang, In-Sang

Contributors dc:contributor

• Anderson, A.C.

• phonon-dislocation interaction
• LiF crystals
• KCl crystals
• low-temperature thermal conductivity
• electrically insulating crystals
• lattice thermal conductivity

Statement dc:rights

• Copyright 1988 In-Sang Yang

Language dc:language

en

Identifier

3473897

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/23927