CHINESE JOURNAL OF PHYSICS VOL. 39, NO. 4 AUGUST 2001

Raman Study of the Phase Transition in [N(C₂H₅)₄]₂ZnCl₄ Single Crystals

Tsai-Shia Jung, Hsiang-Lin Liu and Jiang-Tsu Yu

Institute of Physics, National Taiwan Normal University,

Taipei, Taiwan 116, R.O.C.
(Received April 10, 2001)

Polarized Raman spectra of oriented single crystals [N(C₂H₅)₄]₂ZnCl₄ (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.

PACS. 78.30.-j - Infrared and Raman spectra and scattering.
PACS. 61.50.Ks - Crystallographic aspects of polymorphic and order-disorder transformations.

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