Creep experiments have been carried out on single crystals of Fe2SiO4 and Co2SiO4. The crystals were internally buffered by oxide precipitates against FeO and SiO2, respectively. The following flow laws were obtained: for internally buffered fayalite, ϵ = 1·7 × 1022σ6±1 pgOOexp(-923±220kJmoL−1RT), and for internally buffered cobalt olivine. (formula presented) where ϵ is in units of s−1 and σ and po2 are in units of MPa. In Fe2SiO4, he observed po2 dependence of the strain rate can be explained by a model in which creep is controlled by the motion of positively charged jogs along edge dislocation lines, with the diffusion of oxygen by a vacancy mechanism as the rate-limiting step. In Co2SiO4, on the contrary, the po2 dependence suggests that creep may be glide controlled, that is, rate limited by migration of ionized kinks along the dislocations. However, defect associations, which cannot be totally ruled out, were not considered in this work.
|Original language||English (US)|
|Number of pages||15|
|Journal||Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties|
|State||Published - Jan 1985|