INFLUENCE OF IMPURITIES AND TESTING ATMOSPHERE ON HIGH-TEMPERATURE DEFORMATION OF CSI CRYSTALS

The influence of anion (bromine) and cation (cadmium and barium) impur ities, as well as testing atmosphere (air, argon, vacuum) on high temp erature deformation of CsI crystals is studied. This deformation in Cs I has some peculiarities, which are the superplasticity signs and evid encing about instability of a lattice state. All the impurities studie d caused the hardening, their effect in superplasticity depends on its solubility in the CsI lattice: the less the solubility, the stronger the effect. With testing in vacuum and argon, when the formation of po int defect clusters occurs, enhanced the superplasticity evidence comp ared to that by testing in air, where clustering is prevented. These f acts, as well as a quality resemblance of stress-strain curves of sing le- and polycrystalline specimens give the basis for the conclusion, t hat superplasticity is the manifestation of a plastic instability of t he crystal, the instability centers may be precipitates and point defe ct clusters.