Raman scattering in ferroelectric [NH(CH3)3]3Sb2Cl9 single crystals

The Raman spectra of ferroelectric [NH(CH3)3]3Sb2Cl9 single crystals were studied at temperatures ranging from 90 to 390 K. An assignment of most of the observed bands is proposed. A second‐order phase transition around 364 K leading to a high‐temperature paraelectric phase manifested itself by spliting of the antisymmetric CH3 stretching band (3035 cm−1) below the transition temperature. A temperature dependence study revealed the existence of disorder in the crystal. A systematic measurement of the CH3 torsional vibration Raman band (305 cm−1) was performed and the activation energy (Ea = 2.39 kcal mol−1) of an unidentified organic group HN(CH3)3+ motion was extracted from the half‐width versus temperature curve.