AC Conductivity and Dielectric Properties of Cu2HgI4

A. M. Salem ； Y. A. El-Gendy ； G. B. Sakr

《Chinese Journal of Physics》 47卷6期 (2009/12) Pp. 874-884

並列摘要

Cu2HgI4 powder was prepared at room temperature using the reactive chemical solutions process. The structure of the prepared powder was identified by X-ray diffraction. The dc electrical conductivity, σ(subscript dc), studied in the temperature range 303-370 K shows a drastic change around 340 K, which is attributed to a phase transition from a first-order phase to a fast ion-conducting one. The frequency dispersion curves of the conductivity, σ(subscript ac)(ω), capacitance, C(subscript x), real and imaginary parts of the dielectric constants, ε', ε”, and loss-factor, tanδ have been investigated in the frequency range 10^2-10^5 Hz and temperature range 303-354 K. A characteristic hopping frequency, ω(subscript p), was found to be involved in the conduction mechanism, above which the conductivity obeys the universal power-law behaviour. The variation of capacitance with frequency was explained according to the Goswami and Goswami model. The frequency dependence of the loss tangent, tanδ, shows a relaxation peak which shifts towards higher frequency with increasing temperature, indicating a characteristic feature of the Debye-type relaxation. The imaginary part of the dielectric constant, ε”, varies inversely with frequency. The maximum barrier height, Wm, has been calculated at different temperatures and was used to calculate the theoretical value of the material optical band gap, E(subscript g).