Ionic conductivities and dielectric analysis of (C₆H₂₀N₃)BiI₆.H₂O compound

Thermogravimetric analysis, differential scanning calorimetry analysis and complex impedance spectroscopic data have been carried out on (C₆H₂₀N₃)BiI₆.H₂O compound. The results show that this compound exhibits a phase transition at 325 K which was characterized by differential scanning calorimetry spectroscopy and dielectric measurements. The dielectric analysis has been studied by using impedance spectroscopy measurements over a wide range of temperatures and frequencies, 290-350 K and 100 Hz-1 MHz, respectively. The Z′ and Z″ vs. frequency plots are well-fitted to an equivalent electrical circuit consisting of a parallel combination of a bulk resistance Rp (polarization resistance) and constant phase elements CPE (capacity of the fractal interface). The frequency-dependent AC conductivity is well analyzed by Jonscher's universal power law: σ(ω,T)=σdc(T)+A(T)ωs(T). This suggested hoping conduction due to three theoretical models. The latter can be attributed to the quantum mechanical tunneling model in region I and correlated barrier hopping in region II. The temperature dependence and dielectric relaxation of the DC conductivity satisfied the Arrhenius law. Furthermore, the modulus plots have been characterized by full width at half height or in terms of a non-experiential decay function φ(t)=exp(−t/τ)β. The values of the activation energies obtained from the electrical conductivity and electric modulus are near, which suggests that the transport is probably due to the ion hopping mechanisms. (author)