PHASE-TRANSITION AND RAMAN STUDIES ON CS-0.9(NH4)(0.1)HSO4

The phase transition in the mixed Cs-0.9(NH4)(0.1)HSO4 were characteri zed by differential scanning calorimetry and Raman spectroscopy studie s at temperatures ranging from 300 to 500 K. The I-II transition is ch aracterized bg the conversion of infinite (HSO4-)(n) chains into cycli c (HSO4-)(2) dimers. The II-III phase transition corresponds to a supe rprotonic phase transition (STP) where protons and SO42- ions contribu te to the unusually high conductivity. The activation energy mas deter mined from the plot of Delta nu(1/2) as a function of temperature for the nu(S-OH) bands and from the conductivities. The two values have th e same order of magnitude.