AC Conduction Mechanism in Perovskite-like Dimers (C2H8NO)2M2X6, M=Co/Cu, X=CI/Br

Abstract

AC conductivities at 5 Hz-10 kHz and 78 K up to room temperature of bis- (ethanolammonium) Co2X6, and bis- (ethanolammonium) Cu2X6, X=C1 and Br are reported. At high temperatures, band type conduction prevails for all dimers. In the low temperature range T< 200 K the (CcbBr6)-2 dimer conducts via small polarons and the other three dimers conduct via quantum mechanical tunneling. The obtained relaxation times for the different dimers werefound to be 1.1 IO-14 s. The frequency dependence follows the universal power law σac(ω)= Aωδ. The exponent s and the pre-factor A were found to be very sensitive to the phase transitions, with 5 showing a minimum or maximum at the transition temperature. Changes in the conduction mechanism are reflected by abrupt changes in the variation of the pre-factor A vs 1 IT relation. The conduction is found to depend on the type of the halide ion rather than on the transition metal ion. © 2014, Verlag der Zeitschrift für Naturforschung. All rights reserved.