Low Temperature Physics: 27, 404 (2001); https://doi.org/10.1063/1.1374728 (8 pages)
Fizika Nizkikh Temperatur: Volume 27, Number 5 (May 2001), p. 547-557    ( to contents , go back )

Low-temperature internal friction a -peak in niobium and its relation to relaxation of kinks in dislocations

V. D. Natsik, P. P. Pal-Val, L. N. Pal-Val, and Yu. A. Semerenko

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61164, Ukraine
E-mail: palval@ilt.kharkov.ua

Received November 3, 2000

Abstract

The influence of impurities on the parameters of the internal friction a-peak registered in Nb single and polycrystals in the temperature range 200-250 K at oscillation frequency »80 kHz is studied. It is found that an increase of the sample purity results in an increase of the peak location temperature, as well as in an increase of its width and amplitude. The structural sensitivity of the peak has been observed in studies of the influence of preliminary plastic deformation, thermocycling and low-temperature recovery on the peak parameters. A statistical description of the experimental data is proposed which takes into account the dependence of activation energy and attempt period both on impurity concentration and on characteristic value and statistical scatter of internal stresses. A new algorithm of the analysis of the experimental data is developed which allows one to obtain empirical estimations of the activation energy and its dispersion as well as of the attempt period and relaxation strength corresponding to various structural states of the samples. It is shown that the a-peak is due to the resonant interaction of elastic vibrations with the process of thermally activated nucleation of kink pairs in dislocation segments lying in the valleys of the Peierls potential relief. The main parameters describing this process are estimated. The a-peak properties in Nb are found to agree qualitatively with the kinetic theory of nucleation and relaxation of dislocation kinks proposed by Engelke.

PACS:
61.70.Le -
62.40.+i - Anelasticity, internal friction, stress relaxation, and mechanical resonances (see also 81.40.Jj Elasticity and anelasticity in materials science)
62.80.+f - Ultrasonic relaxation (see also 43.35.Fj Ultrasonic relaxation processes in liquids and solids�in acoustics appendix; for ultrasonic attenuation in superconductors, see 74.25.Ld)

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