The formation of interstitial solid solutions based on solvents showing the fcc structure: elastic versus chemical interaction

Abstract

Unit cell parameters and densities were measured for the terminal solid solutions of the late transition metals showing the fcc structure (α-Co, Rh, Ir, Ni, Pd, Pt) with boron and partly with carbon. Especially the solid solutions Pd(B) and Pd(C) were investigated because of the large homogeneity range up to the atomic fractions x f B=0.186 and x f C≃0.05, respectively. The unit cell parameter increases and the density decreases with increasing boron and carbon content. Comparison of the calculated and measured number of atoms in the Pd(B) and Pd(C) unit cells confirms the interstitial nature of both solid solutions. The difference between the measured dependence of the Pd–B shortest interatomic distances on the solute content and those calculated according to the hard sphere model indicates a distinct negative deviation from additivity of the pure form volumes. The chemical (electronic) interaction plays a more important role than the elastic interaction (characterized by a size factor) in the formation of solid solutions of metals with the interstitially dissolved metalloids H, B, C, N and O.