The structure of the high-temperature phase was studied by using neutron diffraction techniques. Alloys with Ni contents of between 71 and 75at% were examined at temperatures ranging from 600 to 1000C. The results confirmed that the structure was of DO3 type, and that the vacancy concentration amounted to up to 20% of the Ni sites. It was suggested that the high number of vacancies played an essential role in stabilizing the DO3 phase. The vacancies were also held to be responsible for the extremely high Ni tracer diffusivities which were measured.

O.G.Randl, G.Vogl, M.Kaisermayr, W.Bührer, J.Pannetier, W.Petry: Journal of Physics - Condensed Matter, 1996, 8[41], 7689-98