On phase transitions in layered ferroelastics with light impurities

The effect of Li and Na light impurities on the temperature of structural phase trnansition in isostructural KSc(MoO4)2 RbSc(MoO4)2, CsSc(MoO4)2 ferroelastics is studied. A structural phase transition is revealed in pure CsSc(MoO4)2. The presence of Li impurities in each of the considered compounds results in new phase transitions. Temperatures of these virtual transitions are analyzed on the basis of phonon spectrum changes and are conditioned by the loss of impurity crystal stability. Dynamic nature of virtual transitions is revealed and on its basis a possble character of dipole moment ordering of lithium ions is discussed