Kinetics of NiAl3 and Ni2Al3 phase growth on lateral diffusion couples

The phase formation of NiAl3 and Ni2Al3 is studied on lateral diffusion couples of an Al-rich source on a Ni thin film at temperatures from 375 to 500 °C. Analytical electron microscopy is used to determine the crystal structures, chemical compositions, and the widths of growing phases. Simultaneous growth of NiAl3 and Ni2Al3 is observed at 375 and 450 °C. Al atoms dominate the diffusion process in NiAl3 and Ni2Al3. The growth of Ni2Al3 has a parabolic dependence on annealing time, and the growth constant, X2/t, has an activation energy of 2.0±0.2 eV. The growth kinetics is further studied by comparing the growth rates of NiAl3 in one- and two-phase growth, and by applying the criteria proposed by Gösele and Tu to the simultaneous growth of NiAl3 and Ni2Al3.