Dielectric dispersion of new ferroelectric cobalt halide dimers: Bis-ethanolammonium-hexahalocobaltate, (C2H8NO)(2)Co2X6, X = Cl/Br

The AC conductivity in the frequency range 5.0 Hz 10.0 kHz, the magnetic su sceptibility in a field of 14.7 and 17.8.10(4)A/m, and differential thermal analysis at 78 K up to room temperature for bis-(ethanolammonium)Co-2 Xh(6 )X = Cl and Pr are reported. The bromide dimer undergoes an order-disorder transition at 302 K and a displacive type ferroelectric transition at T sim ilar to 220 K. The chloride dimer shows two transitions, the first being in a displacive ferroelectric one at T similar to 210 K showing critical slow ing down. The second phase transition, occuring at 282 K, is found to be in active in the electric measurements.