Superprotonic conduction and ferroelectricity in addition cesium sulfate tellurate Cs2SO4.Te(OH)(6)

Dielectric investigations in the temperature and frequency ranges 300-600 K and 10(2) - 1.3 x 10(7) Hz, respectively, show that cesium sulfate tellura te Cs2SO4. Te(OH)(6) (CsSTe) exhibits two phase transitions at 490 and 500 K. The a.c. complex impedance measurements performed on CsSTe material show an important level of conductivity at high temperature, attributed to the motion of H+ proton. This behavior is in agreement with the presence of a s uperionic protonic phase transition in CsSTe material at 500 K. This assign ment was confirmed by the analysis of the M " /M " (max) spectra. The tempe rature dependence of is an element of (')(r) and tan delta indicates that t he anomaly at 490 K is attributed to a ferroelectric-paraelectric phase tra nsition. Crystallographic studies show that this material presents a non-ce ntrosymmetric space group at room temperature which is in agreement with ou r last deduction. (C) 2001 Elsevier Science Ltd. All rights reserved.