Properties of (NH4)2SbF5 crystal: Infrared and thermal studies

Phase transitions of ammonium pentafluoroantimonate (NH4)2SbF5 crystal have been investigated by thermal and infrared measurements. Differential scanning calorimetry showed two phase transitions: at 291 K and about 171 K. This result is similar to the issues obtained during specific heat investigations. The infrared spectra of powdered (NH4)2SbF5 crystal in Nujol and Perfluorolube oil were studied in the wide region of internal vibration of the NH4+ and SbF52− ions (6000-400 cm−1) in the temperature range between 98 and 320 K. The temperature changes of wavenumber, half-width, center of gravity and intensity of the bands were analysed to clarify the cationic and anionic dynamics contribution to the phase transitions mechanisms. The separate bands were assigned to vibrations of two inequivalent ammonium ions below 168 K.