Reflection and vibrational spectra of SbSCl0.1I0.9 crystals in the ferroelectric phase-transition region

SbSCl0.1I0.9 crystals were grown from the vapor phase and reflection spectra were recorded using a Fourier-transform IR spectrometer. The optical parameters and optical functions along the c axis were calculated using an improved Kramers–Kronig technique with two confining spectral limits. The reflection spectra were analyzed using the oscillator parameter fitting technique for comparison of results. The vibrational frequencies ωL and ωT were evaluated. The ferroelectric phase-transition temperature was estimated as 330 K for SbSCl0.1I0.9 from experimental reflection measurements and theoretical investigation of the potential energy of Sb atoms for B1u soft normal modes of SbSI and SbSCl0.1I0.9 crystals.