The yield strength and dynamic behaviour of dislocations in MgO crystals at high temperatures

Abstract

The mechanical behaviour and mobility of dislocations in MgO crystals in the temperature range 20 to 800° C are shown to be dependent on the concentration and the valence state of impurities. Impurities of trivalent state are found to interrupt the motion of screw dislocations and lead to an increase of the yield strength throughout the temperature range investigated. Impurities of divalent state, of which Ca²⁺ ions are the most prevalent, are shown to retard the motion of edge dislocations by forming an atmosphere at elevated temperatures and are responsible for a peak of the yield stress appearing around 700° C.