Dielectric behaviour and phase transition of SrAlF5single crystals

Dielectric constant and ionic conductivity measurements have been performed in SrAlF 5 single crystals, along the [100] and [001] directions, as functions of frequency (10 Hz–10 MHz) and temperature (300–800 K). The real part of the ac conductivity showed the 'universal dynamic response of dielectrics', evidenced by a power-law dependency on the frequency. A first-order phase transition was observed around 715 K, with a considerable thermal hysteresis in the real part of the dielectric constant and in the electrical conductivity. The ionic conductivity varies by about four orders of magnitude in the temperature interval studied and shows various regions with Arrhenius behaviour with activation energies ranging from 0.2 to 1.40 eV.