The behavior of Ni in monocrystalline material was investigated at temperatures ranging from 613 to 949K (table 47). Ion-beam sputtering and secondary-ion mass spectrometry were used to measure the concentration versus depth profiles. It was found that the diffusion of Ni could be described by:

D (m2/s) = 6.2 x 10-5exp[-2.32(eV)/kT]

It was noted that these results were consistent with previously reported high-temperature tracer data. By combining the latter data with the present low-temperature results, a curvature of the Arrhenius plot was revealed. This curvature was attributed to the contribution that was made by di-vacancies at high temperatures. The variation of the diffusivities of Fe and Ni as a function of temperature could be explained by using a modified electrostatic model for impurity diffusion and by assuming effective values for the charge difference between host atoms and impurities.

A.Almazouzi, M.P.Macht, V.Naundorf, G.Neumann: Physical Review B, 1996, 54[2], 857-63

Table 48

Diffusivity of Ni in Cu