EXPERIMENTAL AND THEORETICAL INVESTIGATIONS OF EELS NEAR-EDGE FINE-STRUCTURE IN TIAL WITH AND WITHOUT TERNARY ADDITION OF V, CR, OR MN

The intermetallic compounds TiAl without additives and with similar to 5 at % V, Cr, or Mn, have been studied by electron-energy-loss spectr oscopy. Spectral shapes in the vicinity of the Ti L-2,L-3, Al L-2,L-3 and Al K edges are investigated and compared with calculated spectra. Dipole selection rules (Delta l = +/-1) apply, and L edges thus provid e information on s+d final states, while K edges provide information o n p final states. The theoretical densities of states have been calcul ated using the ab initio full potential linear augmented-plane-wave me thod, and, combined with the relevant matrix elements, theoretical spe ctra have been obtained. In calculating the electronic structure of te rnary doped phases, a rigid-band model producing only variations in th e Fermi level within the energy bands is used. This model shows good a greement with experiments. From the interpretation of the spectral fea tures at the Al site (in doped as well as undoped phases) common, hybr idized electronic states between the Al sp and Ti d bands are observed . This is evidence of covalent bonding.