Phonon focusing and phonon conduction in hexagonal crystals in the boundary-scattering regime

1974 ◽  
Vol 9 (2) ◽  
pp. 466-480 ◽  
Author(s):  
A. K. McCurdy
Keyword(s):  
Boundary Scattering ◽  
Phonon Conduction ◽  
Phonon Focusing ◽  
Hexagonal Crystals

scholarly journals Analysis of the Effect of Resonant Phonon Scattering on the Thermal Conductivity of CaF2

1976 ◽  
Vol 29 (2) ◽  
pp. 19 ◽  
Author(s):  
PRW Hudson ◽  
EE Gibbs
Keyword(s):  
Thermal Conductivity ◽  
Low Temperatures ◽  
Phonon Scattering ◽  
Low Frequency ◽  
Resonant Scattering ◽  
Boundary Scattering ◽  
Scattering Mechanism ◽  
Scattering Mechanisms ◽  
Phonon Conduction

An analysis is presented of the various phonon contributions to the thermal conductivity of CaF2 doped with 1�0% and 0�1 % of yttrium or thulium. The broad phonon resonant scattering term is found to reduce the low frequency phonon conduction significantly. This is responsible for the relatively stronger suppression of the conductivity at low temperatures in the phonon boundary scattering region. Thus broad quasilocalized phonon resonant scattering mechanisms have a similar effect to phonon precipitate scattering. It also follows that, in the case of a broad resonant scattering mechanism, a dip will not necessarily be seen in the conductivity.

Origin of the alternate bright/dark contrast in HREM images of hexagonal crystals, particularly 6H-SiC

1993 ◽  
Vol 51 ◽  
pp. 914-915
Author(s):  
J.S. Bow ◽  
R.W. Carpenter ◽  
M.J. Kim
Keyword(s):  
High Resolution ◽  
Incident Beam ◽  
Hexagonal Crystal ◽  
Detailed Explanation ◽  
Similar Character ◽  
High Resolution Images ◽  
The Difference ◽  
Zigzag Shape ◽  
Hexagonal Crystals ◽  
Dark Contrast

A prominent characteristic of high-resolution images of 6H-SiC viewed from [110] is a zigzag shape with a period of 6 layers as shown in Fig.1. Sometimes the contrast is same through the 6 layers of (0006) planes (Fig.1a), but in most cases it appears as in Fig.1b -- alternate bright/dark contrast among every three (0006) planes. Alternate bright/dark contrast is most common for the thicker specimens. The SAD patterns of these two types of image are almost same, and there is no indication that the difference results from compositional ordering. O’Keefe et al. concluded this type of alternate contrast was due to crystal tilt in thick parts of the specimen. However, no detailed explanation was given. Images of similar character from Ti3Al, which is also a hexagonal crystal, were reported by Howe et al. Howe attributed the bright/dark contrast among alternate (0002) Ti3Al planes to phase shifts produced by incident beam tilt.

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