Electrical properties of SbSI crystals in the vicinity of the ferroelectric curie point

The electrical properties of SbSI crystals have been studied with particular reference to the ferroelectric phase transition. The dielectric constant along the c-axis obeys the Curie-Weiss law with C = 2.54 × 105 K and T0 = 15.2°C. The coefficients in the Gibbs free energy expanded by the electric polarization have been determined to be ξ = -3.02 × 108 Vm5C-3 and ζ = 6.99 × 109 Vm9C-5 by using the temperature dependence of the dielectric constant and the spontaneous polarization. An anomaly in the electric conductivity has been found at the Curie point. Effects of substitution of Bi for Sb in SbSI on the behavior of the phase transition have been also studied. The Curie point decreases with increasing Bi concentration x according to the relation Tc(x) = Tc(0) - 520x (°C). The phase transition, which is a first-order for pure SbSI, becomes a second-order between x = 0.10 and 0.17.