POLARIZED-LIGHT STUDY OF THE CSHSO4 AND CSDSO4 SUPERPROTONIC CRYSTALS

The results of an optical polarization study of superprotonic CsHSO4 a nd CsDSO4 crystals in the vicinity of phase transitions are presented. Our observations allow us to state that the temperature of III-II pha se transition in 'fresh', high quality crystals is 373 K. The temperat ure of the phase transition of the specimens that have experienced the III-II phase transition earlier is reduced to 330 K. It is establishe d that changes of the domain structure in CsDSO4 crystals are observed on both increasing and decreasing temperature at 3 K away from the te mperature of the superprotonic phase transition. The appearance of the new structure is accompanied by a gradual increase in the conductivit y by 1.5-2 order of magnitude and then the conductivity increases abru ptly by another two orders of magnitude at the temperature of the supe rprotonic phase transition.