Structural Phase Transitions in (n-C3H7NH3)2SbBr5

Abstract

Abstract Dielectric, DSC, thermal expansion and preliminary X-ray diffraction studies on (n-C3H7NH3)- SbBr5 are reported. It was found that this crystal undergoes a complex sequence of phase transitions. On cooling: phase I → phase II at 188.7 K (continuous), II → III at 165 K (1st order, ΔS = 26.8 J/mol K), III → IV at 137 K (1st order, 1.6 J/mol K). On heating: IV → III at 154 K, III → II’ at 168 K, II’ → II at 177 K (1st order, 2.8 J/mol K), II → I at 189 K. All 1st order phase transitions are likely due to the motion of the n-C3H7NH3 +cations. The dielectric dispersion studies between 100 Hz-1 MHz within the phases I and II indicate a fast reorientational motion of dipoles with τ < 10−7 S.