Quenching Rate and Quenched-In Lattice Vacancies in Gold

Abstract

The quenched‐in resistivity in gold was measured for cooling rates from 10⁴ to 10⁵ °C/sec. The quenched‐in resistivity increases considerably with increasing cooling rate and depends strongly on the quenching temperature over much of the range investigated; for example, for a cooling rate of 20 000°C/sec about 12% of the residual resistivity recovers during the quenching process for a quench from 700°C and about 20% recovers for a quench from 800°C. For the lower quenching temperatures the quenched‐in resistivity appears to approach saturation at the fastest quenching rates obtained. A linear relation between the logarithm of quenched‐in resistivity and the reciprocal of quenching rate was observed. This allowed linear extrapolation to infinite quenching rate. The quenched‐in resistivity ρ_∞ obtained by extrapolating to infinite rate, is expressed by ρ_∞=ρ₀ exp(−H_f/kT), where ρ₀=5.0×10⁻⁴ Ω‐cm and the formation enthalpy, H_f=0.97 eV. Assuming ρ_∞ corresponds to single vacancies rather than clusters, measurements of the length change of the quenched specimens and using Tewordt's result that a vacancy has 0.47 atomic volume, the following constants were obtained: The resistivity of 1 at. % of vacancies, 1.7×10⁻⁶ Ω‐cm; the entropy of formation of a vacancy, 0.95×10⁻⁴ eV/°K; and the fractional concentration at the melting point, 6.4×10⁻⁴.