Combined investigations of NiAl alloys by means of X‐ray photoelectron spectroscopy, compton gamma scattering and positron annihilation

Abstract

The results of measurements of Compton profiles, photoelectron spectra, positron annihilation curves, and lifetime spectra of several NiAl alloys are discussed in terms of bonding and stability in transition metal aluminides.The interpretation of experimental Compton profiles suggests a transfer of nearly-free electrons from A1 sites to more localized d-like states on Ni-sites. The transfer increases with A1 contents up to 50 atomic percent. From X-ray photoelectron spectra in the oase of Al-rich alloys a different behaviour follows. The results support a model established by WENGER. Following this in the composition range above 50 percent A1 no further charge is transferred to Ni cells. The Ni d states seem t o be occupied in the Al-rich alloys. A preferential annihilation of positrons in Ni cells is though to have its origin in the enhanced negative charge of these cells caused by charge transfer.