Thermal generation of vacancies from voids in aluminium

The thermal generation kinetics of vacancies from octahedral voids in aluminium has been studied by the measurement of residual resistance due to vacancies generated during pulse heating of the specimen for short time, and also by electron microscopic observation of the voids. The vacancy generation curves saturated at the levels of 3.2Δρ0 and 2.3Δρ0 for the voids with edge length l = 6 nm at 543K and 573K, respectively, where Δρ0 is the resistivity due to the thermal equilibrium concentration of vacancies. For the voids with edge length l = 17nm the generation curves saturated at the levels of (1.02–1.05)Δρ0 for both temperatures. These results are consistent with a newly proposed model that takes account of diffusion limited vacancy generation from the edge and the surface parts of the voids, with the respective promotive energies of vacancy formation ΔE and ∊. The new model yielded the best fit value sets ΔE = (0.16±0.01)eV and ∊ = 0 for the voids with l = 6nm, and ΔE = (0.04 ± 0.01) eV and ∊ = 0 for l = 17nm voids. These results indicate that the contribution from the surface part to the vacancy generation curves is dominant in the large voids, while the contribution from the edge part becomes significant in the small voids.