Crystal structure, Spectroscopic characterization, impedance spectroscopic investigation and AC electrical conduction behavior of [(NH4)0,79K0,21]2Cu0,71Ni0,29Cl4.2H2O

Abstract The present research under study makes in attention the synthesis of a new mixed material of formula [(NH4)0,79K0,21]2Cu0,71Ni0,29Cl4.2H2O by slow evaporation at room temperature. It is characterized by the following techniques: X-ray diffraction (XRD), IR absorption, Raman scattering, thermal analysis, AC conductivity and dielectric measurements. The crystals of [(NH4)0,79K0,21]2Cu0,71Ni0,29Cl4.2H2O belong to the Tetragonal system with the P4(2)/mnm space group. The crystallographic network consists of an [Cu0,71Ni0,29Cl4.(H2O)2]2− anion located on an inversion center and coordinated by two water molecules and four chlorine, and two [(NH4)0,79/K0,21]+ protonated cations. The crystalline stability is ensured by hydrogen bonds to form a zero-dimensional network. Furthermore, the spectroscopic results, at room temperature, confirmed the existence of both cationic and anionic parts, which is in perfect harmony with the results obtained from structural measurements. The impedance spectroscopy technique was used in order to understand the evolution of the electrical behavior and the relaxation process in this material. Accordingly, the experimental data of the Nyquist were fitted to the equivalent circuit created by a parallel combination of grain resistance Rg and a term of complex elements: constant phase elements CPE. The impedance spectroscopic confirms the existence of non-Debye behavior. As a matter of fact, the DC conductivity exhibits a semiconductor behavior. The transport of the charge carrier happens through an ion hopping mechanism, influenced by the motion of the K⁺ and NH4+ cations within the structure of [(NH4)0,79K0,21]2Cu0,71Ni0,29Cl4.2H2O. The AC conductivity data are well described by Jonsher’s law. The thermal behavior of the exponent parameter "n" reveals that the conduction mechanism is non-overlapping small polaron tunneling.