Thermal, dielectric properties and vibrational spectra of [n-C4H9NH3]2[BiBr5] crystal

Abstract: [n-C4H9NH3]2[BiBr5] exhibits five solid–solid structural phase transitions; at 309 (1st order), 291 (1st), 240 (1st), 219 (close to 2nd) and at 166K (1st). The phase transitions at 291 and 240K are accompanied by distinct dielectric anomalies. The dielectric relaxation process was found to appear over the phases (III) and (I). The infrared spectra for [n-C4H9NH3]2[BiBr5] were measured in the region of the internal vibration of the n-butylammonium cation (4000–400cm−1) between 12 and 320K. The temperature changes of wavenumbers and of a width for many of the internal modes of the n-butylammonium clearly indicate the contribution of the organic sublattice to the phase transition mechanism. [Copyright &y& Elsevier]