Mobility of interstitial oxygen in scandium by anelastic spectroscopy

The high-temperature anelastic spectrum of the solid solution Sc-O has been investigated on a polycrystalline sample at oxygen concentrations between 0.024 and ∼0.9 at.% O, as estimated by residual resistivity and intentional O doping. Two thermally activated relaxation processes appear near 430 and 520 K for a vibration frequency of 3.5 kHz; both peaks are stable with thermal cycling and their intensities increase with the oxygen content, indicating that they are due to O jumps. The process at lower temperature has an intensity that strongly increases with increasing temperature, when measured at higher frequency (42 kHz), indicating that the relaxation occurs between states differing in energy by ∼0.3 eV. The peak is describable by a single relaxation time, and is interpreted as due to the stress-induced hopping of single oxygen atoms between the non-equivalent tetrahedral and octahedral interstitial sites. The process at high temperature is tentatively attributed to O pairs. An estimate of the specific resistivity of O atoms has been provided.