Dielectric and Raman investigations in the temperature and frequency ranges 300–550K and 102 – 104Hz respectively show that M2(SO4). Te(OH)6 with (M = K, Rb and Cs) materials present three phase transition. The first transition observed at 480, 440 and 460K respectively for M = K, Rb and Cs and should be probably of order-disorder type. The second one was observed only for Rb2(SO4). Te(OH)6 and Cs2(SO4). Te(OH)6 respectively at 510 and 495K. The third peak observed at 490, 520 and 510K for M = K, Rb and Cs respectively can be attributed to a ferroelectric-paraelectric phase transition.

Dielectric and Raman investigations on M2(SO4).Te(OH)6 (M =K, Rb and Cs)

Ferroelectric and electric properties of Rb0.6(NH4)0.4HSO4 single crystal

Ferroelectricity and superionic conduction in telluric sulfates MM′(SO4)Te(OH)6 (M, M′=K, Rb and Cs)

Dielectric, electric and Raman studies on the RbK(SO4)·Te(OH)6 material

High pressure Raman spectroscopic investigations have been carried out on Cs2SO4 up to a pressure of 164kbar. The behaviour of the internal modes of sulphate ions as a function of pressure are examined. In contrast to other disulphates, cesium sulphate does not exhibit any phase transition up to the highest pressures reached in the present investigations. Present results are discussed in the light of earlier studies on other disulphates.

A Raman spectroscopic study of cesium sulphate at high pressure

Dielectric investigations show three anomalies for some Cs1−x(NH4)xHSO4 (x = 005, 01 and 025) compositions The paraelectric-ferroelectric phase transition is well defined in the 280–320 K temperature range A dipolar-type relaxation is observed only for x = 025 The high-temperature phase transition is a plastic phase with highly orientational disorder

Ferroelectric transition in Cs1−X(NH4)xHSO4 solid solutions

A crystal of Cs1—x (NH4)xHSO4 (x=0.1) has been prepared by slow evaporation at room temperature. This crystal is of about.(1x1x0.5) mm3 and is monoclinic at room temperature. DSC, dielectric, optical and infrared measurements allow us to detect a second-order or slightly first-order phase transition at 346 K and a first-order phase transition: superionic protonic phase transition (SPT) at 410 K.

Z. Fakhfakh

Papers

Ferroelectric transition in Cs1−X(NH4)xHSO4 solid solutions

Dielectric, optical and infrared studies of the mixed caesium-ammonium acid sulphate Cs0.9(NH4)0.1HSO4

Synthesis Characterization and Protonic Conduction in Mixed Caesium-Ammonium Hydrogenosulphate Cs0.95(NH4)0.05HSO4