Positron lifetime spectroscopy data on thermal vacancy formation in intermetallic compounds yielded high effective formation enthalpies for close-packed structures, and low values for body-centered cubic structures. The vacancy migration enthalpy could be determined at high temperatures, for B2-FeAl, by studying the equilibrium process after temperature changes. The thermal formation and migration of defects were sensitively investigated here by means of time-differential length-change studies after temperature changes in the neighborhood of the equilibration temperature. The results for vacancies could explain the wide variations in the transition-metal self-diffusivities in intermetallic compounds.

High-Temperature Atomic Defect Properties and Diffusion Processes in Intermetallic Compounds. H.E.Schaefer, K.Frenner, R.Wurschum: Intermetallics, 1999, 7[3-4], 277-87