3.5 Author:
   Ishida, Hiroyuki; Furukawa, Yoshihiro; Kashino, Setsuo; Sato, Setsuko; Ikeda, Ryuichi
Reference:
   Journal, BBPCAX, Ber.Bunsen-Ges.Phys.Chem., EN, 100, 4, 1996, 433-439
Title:
   Phase Transitions and Ionic Motions in Solid Trimethylethylammonium Iodide Studied by 1H and 127I NMR, Electrical Conductivity, X-ray Diffraction, and Thermal Analysis
Abstract:
1H and 127I NMR, differential thermal analysis (DTA), differential scanning calorimetry (DSC), electrical conductivity, and powder and single crystal X-ray diffractions were studied for trimethylethylammonium iodide.Three solid phases, named I, II, and III, were obtained above 410 K, between 336 and 410 K, and below 336 K, respectively.Powder X-ray patterns showed that Phase I and II have a NaCl-type cubic structure (a = 10.00(1) Angstroem, Z = 4) and a tetragonal structure (a = 8.430(5), c = 6.216(4) Angstroem, Z = 2), respectively.The structure of Phase III was determined to be orthorhombic (Pnam (62), a = 11.294(4), b = 10.729(2), c = 7.158(6) Angstroem, Z = 4) by single crystal X-ray diffraction.In Phase III, the C3 reorientation of CH3 groups and the C`3 reorientation of the whole (CH3)3N group in the cation were observed by 1H NMR.In Phase II, the cation is expected to perform the quasi-isotropic reorientation.In Phase I, the cation was found to carry out the isotropic reorientation, while the spherical anion the translational self-diffusion, as evidenced by 1H and 127I NMR, and electrical conductivity.Phase II and I are, therefore, dynamically disordered phases; especially, Phase I is highly disordered.From the dynamical behaviour of the cation and anion, and thermal properties, Phase I can be classified into an ionic plastic phase with a NaCl-type structure.