Phase transitions in CuBiP₂Se₆crystals

Abstract

Investigation results of dielectric (20 Hz–1 MHz) properties of layered CuBiP2Se6 crystals are presented. The temperature dependence of the static dielectric permittivity reveals the first-order “displacive” antiferroelectric phase transition at T c = 136 K. In the paraelectric phase, at low frequencies, dielectric spectra are highly influenced by the high ionic conductivity with the activation energy of 2473 K (0.21 eV). In the antiferroelectric phase the electrical conductivity and its activation energy (531.1 K (0.045 eV)) are considerably smaller. At low temperatures, the temperature behaviour of the distribution of relaxation times reveals complex freezing phenomena. A part of long relaxation time distribution is strongly affected by external direct current (DC) electric field and it is obviously caused by antiferroelectric domain dynamics.