Effects of interstitial additions on the structure of Ti⁵Si³

Abstract

Changes in the structure of Ti₅Si₃ were measured by x-ray and neutron diffraction as carbon, nitrogen, or oxygen atoms were systematically incorporated into the lattice. Additionally, the lattice parameters and variable atomic positions of pure Ti₅Si₃ were determined to be a = 7.460 Å, c = 5.152 Å, x_Ti = 0.2509, and x_Si = 0.6072. The measured trends in lattice parameters as carbon, nitrogen, or oxygen atoms were added to Ti₅Si₃ showed that most of the previous studies on supposedly pure Ti₅Si₃ were actually contaminated by these pervasive light elements. Also, oxygen and carbon additions were shown to strongly draw in the surrounding titanium atoms—evidence for bonding between these atoms. The bonding changes that occurred on addition of carbon, nitrogen, or oxygen acted to decrease the measured anisotropic properties of Ti₅Si₃, such as thermal expansion.