Abstract
The linear thermal expansion of a 99.999% gold bar has been measured throughout the range 15° to 1057°C by direct observation of the length expansion , with filar micrometer microscopes and by measurement of the lattice parameter expansion , by x-ray diffraction with a rotating-single-crystal method. The expansions agree within the experimental precision of about 1: at the lower temperatures. However, the values of thermal expansion obtained are about 1.5% larger than those in the literature. At the higher temperatures () becomes positive, proving that thermally-generated defects are formed which are predominantly vacant lattice sites. The net added concentration of substitutional atomic sites, , just below the melting temperature, is (7.2±0.6)× as obtained by an extrapolation of the data of only 6°C. can be described by . These results are independent of any aggregation of the defects and of any lattice dilatation about the individual defects. Just below the melting temperature, more than 80% of the vacant sites are single vacancies if the divacancy and trivacancy binding energies are less than 0.4 ev and 1.0 ev, respectively.
The present concentrations are about 40% larger than those reported by DeSorbo from a calorimetric study of quenched foil. A critical assessment of the relationship between the present equilibrium measurements and results obtained by quenching methods is attempted. Combination of present values with and values of Bauerle and Koehler and with values of Takamura on quenched and annealed wires gives an electrical resistivity μohm cm/at.% of vacancies and a volume expansion atomic volume/vacancy.
- Received 11 September 1961
DOI:https://doi.org/10.1103/PhysRev.125.862
©1962 American Physical Society