Structural Phase Transitions in [(C2H5)4N]3Sb2Br9 and [(C2H5)4N]3Bi2Br9

Dielectric, DSC and preliminary X-ray diffraction studies on [(C N] Sb Br (TEABA) and [(C N] Bi Br (TEABB) are reported. The compounds are isomorphous, space group P6 22. The static electric permittivity measurements on single crystals in the temperature range 220 - 290 K revealed that both compounds show two distinct dielectric anomalies; TEABA at T = 258 K and T = 252 K, while TEABB at T = 265 K and T = 248 K. The DSC studies show only one anomaly of first order at T =258 K for TEABA, and T =266 K for TEABB. These transitions are presumably related to a freezing of the reorientational motion of the tetraethylammonium cations