Dielectric Relaxation in High Temperature Phases of (NH3C2H5)2CuCl4 Crystals

On the basis of dielectric investigations of (NH 3 C 2 H 5 ) 2 CuCl 4 crystals the existence of phase transitions at T 1 = 364 K and T 2 = 356 K (in a heating run) was confirmed. In the temperature region of 300-370 K Debye relaxation was observed. The change of the dielectric dispersion character around T 3 = 330 K is related to the phase transition. The determined values of the activation energy and the times of the dielectric relaxation for all phases are characteristic of the combined reorientation motions of the alkylammonium cation. The conclusions concerning the dynamics of the hydrogen bonds were confirmed by IR spectroscopy.

[1]  V. Kapustianik,et al.  Temperature Evolution of the Optical Absorption Edge in (NH3C2H5)2CuCl4 Crystals , 2000 .

[2]  S. Sveleba,et al.  Investigations of High Temperature Phase Transitions in (NH3c2H5)2CuCl4Crystals , 1999 .

[3]  V. Kapustianik.  Dilatometric and dielectric study of phase transitions in NH2(CH3)2MnCl3.2 H2O crystals , 1998 .

[4]  I. Polovinko,et al.  Electron–Phonon Interaction and Phase Transitions in [C2H5NH3]2CuCl4 Crystals , 1998 .

[5]  I. Polovinko,et al.  Phase transitions in [N(C2H5)4]2MeCl2Br2 (Me=Zn, Co, Cu) solid solutions , 1997 .

[6]  A. Fuith,et al.  Dielectric Relaxation and Anomalous Electric Conductivity of (NH2(CH3)2)2CoCl4 Crystals , 1996 .

[7]  I. Polovinko,et al.  Dielectric properties and electric conductivity of dimethylammonium tetrachlorcobaltate ferroelectric crystals , 1995 .

[8]  K. Knorr,et al.  Competing structural phase sequences in (C3H7NH3)2CuCl4: reconstructive phase transitions and the low-temperature incommensurate phase , 1994 .

[9]  G. Chapuis,et al.  Structure analysis of the high-temperature phases of [NH3(C3H7)]2CuCl4. I: The commensurate phases , 1990 .

[10]  M. Fujisawa,et al.  Reflectivity and Electronic Structures of Layered Ionic Crystals, (CnH2n+1NH3)2CdCl4: n=1, 2, 3 , 1989 .

[11]  S. Kashida,et al.  Dielectric dispersion of (CH3)3NHCdCl3-molecular reorientation of (CH3)3NH ions , 1987 .

[12]  J. Bats,et al.  Structure of monomethylammonium tetrachlorocuprate at 297 and 100 K , 1987 .

[13]  R. Kind.  Structural phase transitions in perovskite layer structures , 1980 .