ELECTRICAL PROPERTIES OF BETA-PHASE NIAL

The variation of the electrical resistivity of the intermetallic compound β-NiAl at 77° and 298°K is characterized by a sharp minimum at the stoichiometric composition and can be explained by electron scattering from constitutional point defects. The Hall coefficient shows proportionality to the electrical conductivity and changes the sign twice within the homogeneity range. Positive and negative contributions to the Hall coefficient are interpreted by the shape of the Fermi surface relative to the Brillouin zones. Room temperature values of the absolute thermoelectric power and of the high frequency conductivity measured by optical methods indicate that the Fermi surface overlaps into higher Brillouin zones in 〈110〉 direction, when the Al-concentration approaches 50 at.%. From the low energy part of the conductivity spectra effective electron masses were computed. Absorption maxima found at 1·5, 2·5, 4 and 5 eV are attributed to interband transitions of electrons. The compositional dependence of the hydrogen solubility suggests that hydrogen dissociates into proton and electron, the solubility being primarily controlled by the electron potential. Thus the rapid rise in Fermi energy between 46 and 50 at.% Al simultaneously causes the solubility to decrease. © 1969.