Scattering of Electrons by Vacancies through an Order-Disorder Transition in Vanadium Carbide

Abstract

In nonstoichiometric vanadium carbide the carbon‐atom vacancies can be either ordered or disordered at certain compositions. It is likely that these vacancies in the disordered carbide are important electron scattering centers and produce the observed large residual resistivity. On the other hand, band‐structure effects in the transition‐metal carbides are sensitive to composition so it is difficult to evaluate the contribution of vacancies to the electrical resistivity. Since vacancy scattering should vanish in the ordered phase, the change in resistivity through the ordering temperature for VC_0.83 → V₆C₅ should be a useful measure. We have performed such an experiment. Though electron scattering by domain boundaries and by super‐lattice defects is important, the results show that vacancy scattering is indeed significant at low temperatures, but of lessening importance as temperature increases.