No abstract

SrAlF5 has been reported as one of the rare fluoride ferroelectric crystals, belonging to the polar I4 group. However, recent x-ray diffraction data suggest that the correct structure is centrosymmetric (I4 1 /a). Since ferroelectricity is forbidden in this structure, the existence of an inversion centre and the high temperature phase transition were investigated by vibrational and impedance spectroscopies. Thus, the optical phonons of SrAlF 5 single crystals were obtained by polarized Raman scattering and infrared reflectance spectroscopy. On the other hand, the high temperature phase transition was determined by frequency and temperature dependent measurements of the complex dielectric constant.