Ferroelectric properties of pyridinium fluorosulfonate

Pyridinium fluorosulfonate has been synthesized and studied over a wide ran ge of temperatures by differential thermal analysis, differential scanning calorimetry, H-1 and F-19 nuclear magnetic resonance (NMR) spectra and rela xation, and complex dielectric permittivity. The room temperature crystal s tructure has been determined by x-ray diffraction as trigonal, space group R (3) over bar m, Z=1 with a=5.762 Angstrom and alpha=97.96 degrees and con firmed by FTIR spectra. Three solid-solid phase transitions at 235, 272, an d 282 K have been disclosed and the dynamics of the pyridinium cation and t he fluorosulfonate anion characterized. The polar properties of phase II ha ve been demonstrated. The upper transition temperature 282 K appears to be the Curie point of a new ferroelectric compound. (C) 2000 American Institut e of Physics. [S0021-9606(00)70226-1].