0000000000617562
AUTHOR
Roland Machet
Raman measurements in the intermediate phase of [N(CH3)4]2ZnI4
Abstract Raman spectra and deviation angle of the indicatrix have been measured in the intermediate phase, between the two transition temperatures T c1 = 255 K and T c2 = 217 K. The results are consistent with the existence, in this phase, of large domains, piled up along the c-axis (Pnma notation).
Experimental study of the crystals [N(CH3)4]2Znl4by Raman spectroscopy and optical measurements; comparison with isomorph compounds
Abstract Raman spectra and rotation angle of the indicatrix have been measured in the intermediate phase of the crystal [N(CH3)4]2Znl4 The results are consistent with the existence of large ferroelastric domains piled up along the a axis in a monoclinic phase P1121/a (Pnma notation in the paraelectric phase). The phase sequence (Pnma-P1121/a-P21ca) in this compound is different from other members of [N(CH3)4]2BX4 family.
Effect of Hydrostatic Pressure on the Phase Transitions of {N(CH3)4}2ZnCl4-xBrxMixed Crystals
Single crystals of the solid solution system {N(CH 3 ) 4 } 2 ZnCl 4- x Br x have been prepared in a low x region, and the effect of hydrostatic pressure on the phase transitions were measured for x =0.2 and 0.3. The normal-to-incommensurate phase transition temperatures increase linearly with increasing pressure with the rates of 0.126 K/MPa and 0.129 K/MPa for x =0.2 and 0.3 crystals, respectively. The ferroelectric III phase disappears at about 60 MPa for x =0.2 crystal. On the other hand, phase III is not observed for the x =0.3 crystal both at 0 pressure and at high pressures. The II-IV or III-IV transition temperatures also increases with increasing pressure with the rates of 0.162 K/M…