Plastic Deformation of Natural Sphalerite Single Crystals between 300 and 620 K

The plastic behaviour of ZnS (sphalerite) natural single crystals is studied between 300 and 620 K. The parameters of the thermal activation analysis of the plastic deformation are deduced from stress relaxation and rate jump tests, the later data being the most reliable. The values of the activation volume and TEM observations show that the Peierls mechanism is operative in this temperature range, nevertheless above 400 K, another one is probably superimposed. Comparison of the values of the Peierls stress obtained from the activation enthalpy and by extrapolation of the resolved shear stress to T = 0 K points out that a mechanism of non-annihilating kinks is likely and that the kink migration energy is weak.