Resistivity as a Tool for Characterizing Point Defects in Nonstoichiometric Metallic Ceramics

Abstract

ABSTRACTCompounds of IVb and Vb transition metals and carbon are electronically conductive, hard materials that crystallize in the NaC1 structure but are very nonstoichiometric (carbon-poor), as in TiCx, where x is the carbon/metal ratio and is less than unity. Carbon atom vacancies are randomly located in the fcc carbon sublattice and act as scattering centers for conduction electrons. Data on the electrical resistivity as a function of the concentration of these point defects could be used in the opposite sense–i.e., to determine the defect concentration, (l-x), through a measurement of resistivity. The chemical composition (carbon/metal ratio) is then given directly by x. The random vacancies can be ordered by slow cooling from high temperatures, thereby eliminating the residual resistivity. The carbon/metal ratios of these ordered phases are either 3:4, 5:6 or 7:8 and thus can specify the chemical composition precisely.