Atomic substitution and ferroelectric phase transition inBixSb1−xSI

In order to characterize the effect caused by the atomic substitution on the ferroelectric phase change in $A_{\mathrm{V}}{B}_{\mathrm{VI}}{C}_{\mathrm{VII}}$ compounds, we have studied a series of ${\mathrm{Bi}}_x{\mathrm{Sb}}_{1-x}\mathrm{SI}$ mixed crystals. The Raman scattering, together with dielectric constant data, indicate that the Curie temperature $T_C$ falls from 293 K to a nearly zero value when the Bi concentration $x$ is raised from 0 to 0.75. Within this Bi concentration range, the ferroelectric phase transition in the mixed crystal is associated with a SbSI-like soft-mode behavior. The effect of the Sb by Bi substitution is, in many aspects, very comparable to that caused by hydrostatic pressure.