Low-temperature internal friction and thermal conductivity of plastically deformed, high-purity monocrystalline niobium

• Published in: Journal of low temperature physics Vol. 127; no. 3-4; pp. 121 - 151
• Main Authors: WASSERBÄCH, W, SAHLING, S, POHL, R. O, THOMPSON, E
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 2002
• Subjects: Amorphous silicon; Anelasticity, internal friction, stress relaxation, and mechanical resonances; Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electrical and thermal conduction in crystalline metals and alloys; Electronic conduction in metals and alloys; Electronic transport in condensed matter; Exact sciences and technology; Internal friction; Mechanical and acoustical properties of condensed matter; Metals. Metallurgy; Nanostructured materials; Niobium; Phonons; Physics; Plastic deformation; Silica; Thermal conductivity; Temperature dependence; Internal friction; Mean free path; Tunnel effect; Plastic deformation; Experimental study; Niobium; Dislocations; Energy relaxation; Monocrystals; Transition elements; Dislocation mobility; Phonon-defect interactions; Thermal conductivity; Phonon scattering; Strain hardening; Lattice thermal conductivity
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1023/A:1014848312572

The low-temperature internal friction Q super(-1) and thermal conductivity K of plastically deformed, high-purity niobium monocrystals have been investigated and compared with measurements on an amorphous SiO sub(2) (a-SiO sub(2)) specimen. After plastic deformation at intermediate temperatures, an approximately temperature independent internal friction Q super(-1) was observed with a magnitude comparable to that of the a-SiO sub(2) specimen. Plastic deformation at low temperatures leads to an internal friction Q super(-1) with a considerably smaller magnitude. In the temperature range between about 0.3 and 1.5 K, the lattice thermal conductivity k of the deformed specimens decreases with increasing deformation. It is, however, nearly independent of the amount of deformation at the lowest temperatures investigated. In this temperature regime, the lattice thermal conductivity of the specimens varies proportional to T super(3) and has a magnitude as would be expected for an undeformed sample. Additional heat release experiments on an undeformed sample clearly show no long-time energy relaxation effects. We conclude that the defects introduced by plastic deformation cannot be described with the tunneling model which had been proposed to describe the low temperature elastic and thermal properties of amorphous solids. The phonon scattering mechanisms observed in deformed niobium are tentatively related to the dynamic interaction of phonons with geometrical kinks in dislocations.