The temperature and composition dependence of the formation of thermal vacancies in the intermetallic compound Ni3Al with the L12 structure was studied by means of positron lifetime spectroscopy. High values of the effective vacancy formation enthalpy HVF increasing monotonically from 1.65 to 2.01eV with increasing Ni content from 74.1 to 76.5at% were found. A fit to a model based upon the interaction of nearest-neighbor atoms to the experimental data demonstrated the predominant formation of thermal vacancies on the Ni sub-lattice and high concentrations of antisite atoms. The results were considered with respect to recent tracer-diffusion measurements in Ni3Al.

Thermal Formation of Atomic Vacancies in Ni3Al. Badura-Gergen, K., Schaefer, H.E.: Physical Review B, 1997, 56[6], 3032-7