Wydział Chemii

Ryszard Jakubas

Andrzej Miniewicz

M. Bertault

Juliusz Sworakowski

A. Collet

1989

Journal de Physique

50

1483-1491

10.1051/jphys:0198900500120148300

Naukowa

Angielski

Artykuł

Phase transitions occurring in a ferroelectric crystal tris(trimethylam-monium)nonachlorodiantimonate (III) (TMACA) were studied by calorimetric, dielectric andpyroelectric methods. Anomalies of dielectric and thermal properties were found around 200 Kand at ca. 364 K. The anomalies in the low-temperature region exhibit a pronounced relaxationalcharacter. A detailed study of the behaviour of TMACA around 364 K clearly indicates that infact TMACA undergoes two closely lying phase transitions, one of them being probably of thefirst order and the other of the second order. The temperature of the second order transition wasdetermined to amount to (364.0 ± 0.3) K irrespective of the method employed, whereas the firstorder transition temperatures are detected by the dielectric measurements ca. 1 K below thosefound from the calorimetric measurements. An unusual sequence of the phase transitions wasobserved in DSC measurements : both on cooling and on heating the samples through thetransition region, the second order phase transition precedes the first order one. The onset toferroelectricity was found to be associated with the first order phase transition.

http://dx.doi.org/10.1051/jphys:0198900500120148300