Further observations on Rebinder effects in MgO

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Abstract
A study has been made of the influence of impurities on the environment-sensitive mobility of near-surface edge dislocations introduced by a diamond indenter into freshly cleaved MgO surfaces. The environments used were solutions of DMF or DMSO in H2O, and DMF in DMSO. It was found that the extent of edge dislocation motion resulting from the application of a fixed indenter load for a given time varied in a rather complicated manner with composition of the environment. The characteristic features of this variation for DMSO–DMF environments were reproduced by all three types of MgO used, but the relative positions of the maxima and minima were dependent on the concentration and state of ionization of the impurities. Though the observations cannot be interpreted in detail, they appear consistent with a mechanism for Rebinder effects in ionic crystals proposed earlier by the authors.