Abstract
Relative changes in macroscopic length, , and x-ray lattice parameter, , of a 99.999% silver bar have been measured from 14 to 956°C, using a rigid parallel pair of filar micrometer microscopes and a rotating single-crystal x-ray method. The expansions agree within experimental precision (about 1:) at the lower temperatures. At the higher temperatures () progressively increases, showing that atomic sites are added, corresponding to the thermal generation of vacancy-type defects. The concentration of added sites, , at the melting point (obtained by a 4° extrapolation) is (1.7±0.5) ×. This value is only of the corresponding value previously found for aluminum by the same technique. For reasonable values of the binding energies of vacancy aggregates, it is concluded that more than 90% of these extra sites are present as single vacancies. For an entropy of formation of an energy of formation for monovacancies of 1.09±0.10 ev is obtained. This formation energy is slightly larger than half the activation energy for self-diffusion, as similar measurements have shown for aluminum, and as quenching experiments have indicated for gold.
- Received 11 March 1960
DOI:https://doi.org/10.1103/PhysRev.119.600
©1960 American Physical Society