Analysis of tracer and nuclear magnetic resonance measurements of self‐diffusion in aluminium

Abstract

The various nuclear magnetic resonance techniques used for determining self-diffusion coefficients and activation energies in aluminium are evaluated critically. The data considercd most reliable arc analyzed togctlier with the Al*B-tracer measurerncnts of self-diffusion. From the temperature and the pressure dependence of the self-diffusion coefficient,s i t is deduced that a t high temperatures divacancics contribute appreciably to self-diffusion in aluminium and that the self-diffusion activation energy for a monovacancy mechanism is Q1 G Efv -1 E& -= 1.28 eV. With t.he help of measurcmcnts on the equilibrium concentration of vacant sites is subdivided into the formation energy EFv = 0.66 eV and the migration encrgy Et$ = 0.63 cV. The difference between migration and binding energies of divacancies is found to be E?lv -Efv = 0.28 eV. It is shown that the ratio of the selfdiffusion activation volume for monovscancies to the atomic volume is smallcr t,han unity and about equal to 0.9. Die verschiedenen Kernspinresonanzmethoden zur

Electromigration transport mechanisms in Al thin-film conductors

“…On the other hand, Seeger and co-workers interpret the discrepancy as arising from a significant divacancy contribution to Al diffusion at high temperature. 13 The latter authors ascribe a value of E a ϭ1.28 eV to diffusion by monovacancies. Measurements of impurity diffusion in bulk Al, however, do not support a divacancy contribution at high temperature, 14 casting doubt on the latter interpretation.…”

Quenching Studies of Lattice Vacancies in High-Purity Aluminium

“…a temperature dependence of the enthalpies and entropies of formation and migration, or contributions from defects other than monovacancies. The matter was discussed in detail elsewhere 45,46) with the conclusion 45) that in most fcc metals (including Al 47) ) showing strongly curved Arrhenius (or Boltzmann) plots, the curvatures are mainly due to divacancies present in hightemperature thermal equilibrium. (An analogous statement would presumably not be true for bcc metals.…”

“…(19) 47) or Dais, Messer, and Seeger. 11) ) In a detailed analysis, taking into account also the radiotracer data, 51,52) Dais et al 11) deduced for the pre-exponential factor in the Arrhenius relationship of the tracer self-diffusivity by the monovacancy mechanism,…”

Slow Atomic Motion in Zr-Ti-Cu-Ni-Be Metallic Glasses Studied by NMR

“…For instance, possible spatial inhomogeneity of atomic motions cannot be probed directly by these techniques [1]. In contrast, nuclear magnetic resonance (NMR) is a direct probe of local atomic motions and has made significant contributions to the understanding of motions in polymeric and oxide glassy systems [8][9][10][11][12] and in crystalline metals and alloys [13][14][15][16]. So far, the potential of NMR has not been realized in studying atomic motions in metallic glasses [12].…”