High-temperature deformation of forsterite single crystals doped with vanadium

Creep experiments have been performed on samples from a single crystal of vanadium-doped forsterite under controlled {Mathematical expression} conditions to investigate the effects of the addition of substitutional defects in the tetrahedral lattice sites. The addition of vanadium causes marked changes in the flow behavior of the forsterite, with a net increase in the creep rate at high {Mathematical expression} and a new {Mathematical expression} -dependent flow regime at low {Mathematical expression} conditions. These observations can be interpreted as resulting from changes in the majority defect species that maintain the charge neutrality within the crystal. A climb-controlled dislocation creep model for the high-temperature deformation of vanadium-doped forsterite is proposed in which either (i) movement of uncharged jogs is rate-limited by the diffusion of silicon via a vacancy mechanism or (ii) movement of positively charged jogs is rate-limited by diffusion of oxygen via a vacancy mechanism.