Flow stress of Eu doped KCl

Abstract

The flow stress of Eu doped single crystal KCl has been measured as a function of the dopant concentration and thermal history. Samples that have been fast cooled from temperatures near 1000 K show a flow stress that is linear in the concentration. This result is consistent with a model in which isolated Eu ++-K + vacancy dipoles undergo a Snoek ordering. Crystals aged at room temperature first show an increased strength due to aggregation of the dipoles into small clusters. After nine months at room temperature precipitation has taken place and the flow stress is lower than the original value. Heating the crystal at 1010 K restores the original flow stress and, presumably, the original degree of isolation for the Eu ++-K + vacancy dipoles.