Dynamic dislocation behavior in iron-doped magnesium oxide crystals

Abstract

Edge- and screw-dislocation velocities in iron-doped magnesium-oxide single crystals containing 150 ppm Fe+3 have been measured as a function of stress and temperature in order to elucidate the rate-controlling drag mechanism for dislocation mobility. Edge dislocations have been found to move faster than the screw dislocations over the stress and temperature regimes investigated. From the analysis of the edge- and screw-dislocation velocity data in terms of the activation parameters (activation volume, activation enthalpy, total activation enthalpy, and the stress exponent of dislocation velocity), it is suggested that the edge- and screw-dislocation mobilities in MgO single crystals containing 150-ppm Fe+3 dopants are controlled by the interaction of dislocations with the nonsymmetric distortions due to (FeMg.−VMg″) defects. The strain Δε owing to such defects has been calculated and is related to the observed hardening of ion-doped (Fe+3) MgO single crystals.