Ferroelectric phase transitions in alkylammonium halogenoantimonates (III)

A number of crystals composed of nonahalo-genodiantimonate anion and alkylammonium cations of general formula [NH4-n(CH3)n]3Sb2X9 (X=Cl, Br) have been grown which exhibit dielectric anomalies. Ferroelectric phase transitions were found in [(cH3)2NH2]3Sb2Cl9, [(CH3)3NH]3Sb2Cl9 and [(CH3)2NH2]3Sb2Br9. X-ray diffraction, dielectric, NMR and IR studies show that the order-disorder phase transitions are related to a motion of alkylammonium cations.