Temperature study of [N(C3H7)4]2Cd2Cl6 by thermal analysis, Raman scattering, and X-ray powder diffraction: Evidence of phase transitions

The phase transitions of [N(C3H7)4]2Cd2Cl6 have been evidenced by differential scanning calorimetry (DSC), and the different phases have been studied by Raman scattering on single crystals, in the frequency range 50–3900 cm−1 for temperatures ranging between 294 and 451 K. On heating, two reversible phase transitions are observed at T 1 = 321.5 K (weakly first order, with 1.2 K hysteresis) and T 2 = 323.6 K (second order), and a strongly first-order transition occurs in the vicinity of 448 K ( T 3 ), with breaking of the crystal and decrease of the temperature of transition for successive temperature cycles. mperature dependence of the Raman line shifts ν , the half-width Δ ν , and the relative intensities show weak singularities in the vicinity of T 1 and T 2 and marked effects on approaching T 3 . The X-ray powder diffraction patterns at room temperature prior to and after the T 3 phase transition show that it is irreversible, although the diffractograms look qualitatively very similar.