Ferroelectric ordering in imidazolium perchlorate

• Published in: The Journal of chemical physics 2006-04, Vol.124 (14), p.144502-144502-6
• Main Authors: Pająk, Z., Czarnecki, P., Szafrańska, B., Małuszyńska, H., Fojud, Z.
• Format: Article
• Language: English
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.2185098

Imidazolium perchlorate has been synthesized and studied over a wide range of temperatures by differential scanning calorimetry, x-ray diffraction, proton magnetic resonance, optical observation, and dielectric spectroscopy. Polymorphic solid-solid phase transitions have been disclosed at 487, 373, and 247 K . The crystal structure at 298 K has been determined as trigonal, space group R 3 m , Z = 1 with a = 5.484 ( 1 ) Å and α = 95.18 ( 2 ) ° . The imidazolium cations are strongly disordered, while the perchlorate ions are well ordered. At 385 K the crystal structure remains trigonal, space group R 3 ¯ m , a = 5.554 ( 1 ) Å and α = 95.30 ( 2 ) ° . Both ionic sublattices are orientationally disordered. Temperature evolution of the molecular dynamics of the imidazolium cation has been characterized. In spite of a high cationic disorder, dielectric measurements have revealed the polar properties of the crystal. It appears to be a new ferroelectric compound with the Curie point at 373 K . The spontaneous polarization originates predominantly from the behavior of slightly distorted perchlorate anion.