Mechanical loss studies of O—O interactions in ta

Abstract

Mechanical loss measurements are carried out on Ta with various O contents (0.01 to 0.6 at.%) by applying frequencies of about 1 Hz and about 1 kHz. The mean activation enthalpy of relaxation, as determined from the frequency shift of the peak temperatures, does not depend on the O content, i.e. H m = (1.10 ± 0.01) eV. The Snoek maxima are broadened and shifted to higher temperature with increasing O content. The results are analysed in terms of the “random cooperative strain interaction” model for elastic dipoles. In this model, interactions between interstitial atoms, being long range in nature, are treated by a mean field approximation. The critical temperature characterizing the O—O interactions in Ta is proportional to the square root of the O concentration, and increases from 70 K for 0.036 at.% O to 260 K for 0.6 at.% O.