PHASE-TRANSITIONS IN SUPERIONIC-PROTONIC CONDUCTORS CS1-XMXHSO4

MHXO4 type compounds (X = S, Se) generally exhibit a highly disordered phase before melting leading to a plastic and (superionic state. In this paper a review of main results about phase transition and conductivity mechanism is given at the light of new investigations: calorimetry, vibrational spectroscopy and impedance spectroscopy. In mixed alkali acid sulphates Cs1-xMxHSO4 (M = Li, K and Rb). A partial substitution of Cs+ by Li+, K+ or Rb+ spreads out the ionic superionic conductor transition bringing together the properties of the high and low temperature phases. After several cycles melting annealing, the DSC becomes similar to that of glassy material.