Planar defects in off-stoichiometric, Nb-rich NbFe2 Laves phase
Deviations from the ideal, stoichiometric composition of tcp (tetrahedrally close-packed) intermetallic phases as, e.g., Laves phases can be partially compensated by point defects like antisite atoms or vacancies, but also planar defects may offer an opportunity to accommodate excess atoms.
In cooperation with the group Advanced Transmission Electron Microscopy (Christian Liebscher), various types of such planar faults in a Nb-rich off-stoichiometric NbFe2 Laves phase are investigated by HRSTEM (high resolution scanning transmission electron microscopy) and accompanied by ab initio calculations (performed by the CM department). Interestingly, all types of observed planar faults contain structural motifs, which are characteristic for the crystal structure of the µ phase Nb6Fe7 that occurs at higher Nb contents in the binary system; see Fig. 1 for an example.