Using Raman spectroscopy to understand the origin of the phase transitions observed in [(C₃H₇)₄N]₂Zn₂Cl₆ compound.

Phase transitions of the centrosymmetric compound, [(C3H7)4N]2Zn2Cl6, were studied by differential scanning calorimetry (DSC), X-ray diffraction, Raman spectroscopy and dielectric measurements. Two reversible order-disorder and displacive phase transitions are observed at T1=327K and T2=347K with 3K and 4K hysteresis respectively, indicating a first order character. The evolution of Raman line shifts, "ν", and the half-width, "Δν", versus temperature show some singularities associated with the transitions, suggesting that they are governed by the reorientational and the displacement of the organic part. Besides the results of the dielectric permittivity study confirms the conclusion drawn from the calorimetric and Raman measurements that the phase transition located in the vicinity of the temperature of the dielectric proprieties is characterized by change of dynamical state of cation.