Discovery of an intermediate phase in bis-thiourea pyridinium chloride inclusion compound.
This paper reports the occurrence of a new phase for bis-thiourea pyridinium chloride inclusion compound, which is intermediate to the high- and low-temperature ones already reported. The structure of the intermediate phase was determined by the x-ray diffraction and the following sequence of space groups was obtained: Cmcm-->(237 K)Cmc2(1)-->(206 K)Pbca. The triplication of the lattice a parameter in the intermediate phase was observed. Detailed investigations of its phase transitions were performed by differential scanning calorimetry, x-ray diffraction, and dielectric spectroscopy methods. The phase transition at T(1)=237 K is continuous while at T(2)=206 K is discontinuous. Both phase transitions have been classified as of order-disorder type. The high- and low-temperature phases are nonpolar in contrast to the intermediate phase, for which we could not found ferroelectric ordering.
Pajzderska
A
A
Faculty of Physics, A. Mickiewicz University, ul. Umultowska 85, 61-614 Poznań, Poland. apajzder@amu.edu.pl
Wasicki
J
J
Czarnecki
P
P
Toupet
L
L
Collet
E
E