Raman study of the phase transition in [N(C2H5)4]2ZnCl4 single crystals

Polarized Raman spectra of oriented single crystals [N(C2H5)(4)](2)ZnCl4 (TEAZ) have been recorded from 320 K to 40 K during both cooling and heating cycles, covering the known phase transitions. The temperature dependence of the internal vibration of the ZnCl4-2 ion and C-C bond is explained in terms of the motional narrowing due to the disordering CH3 group in TEAZ, which results in the splitting of the ZnCl4-2 and C-C lines in the internal mode region. Our Raman data shows that the phase transition is associated with the onset of the CH3 group disordering. We have also observed that the phase transition exhibits thermal hysteresis.