Proton NMR Study of Molecular Crystal Ferroelectrics, Trichloroacetamide (TCAA)

抄録

Proton spin lattice relaxation time was measured and proton NMR spectrum was observed in a purely molecular ferroelectrics, trichloroacetamide (TCAA). From the temperature and the frequency dependences of the spin lattice relaxation time, it was found that the proton spin lattice relaxation is governed by the fluctuation of proton-proton dipolar interaction in the temperature range including the phase transition temperature. From the computer simulation analysis of NMR spectra, a slight change in proton-proton distance was deduced between the ferroelectric and the paraelectric phases. The relaxation time and then the correlation time of the protonic motion change abruptly at the transition temperature. It was determined that the activation energies of the protonic motion are 1.12×10⁴ J/mol and 0.80×10⁴ J/mol in the ferroelectric and the paraelectric phases, respectively.