Room temperature microplasticity of a spodumene LiAlSi₂O₆

Abstract

As uniaxial compression tests of α spodumene LiAlSi₂O₆ at various temperatures and strain rates systematically led to brittle fracture, room-temperature microindentations have been performed with a view to characterizing the glide systems. Transmission electron microscopy (TEM) investigations show that only the [010] (100) glide system is activated. The resulting dislocations are widely dissociated (up to 3,000 Å) following the reaction [010]→[0 1/2 1/6]+[0 1/2 $\bar 1$/6]. In contrast, in naturally deformed spodumene the activated glide systems found in TEM studies are [001] {110} and 1/2〈110〉{1$\bar 1$0} and the corresponding dislocations are not dissociated. Such a difference in mechanical behaviour is interpreted in considering the necessary impingement of the oxygen atoms during dislocation glide. It is shown that only the dissociated b dislocations can glide with a moderate lattice friction at room temperature. The proposed model is supported by the first exploratory deformation runs performed under confining pressure.