In this work pure \(NiS_{2}\) , 0.15g and 0.25g Ag-doped \(NiS_{2}\) were synthesized using solid-state reaction method. X-ray diffraction (XRD) confirmed the formation of the cubic crystal structure with the space group \(Pa_{3}\) . The cell parameters were a = b = c = 5.668090Å, and all angles were \(90^\circ \) . From XRD data (421) was found to be preferential oriented plan for pure and doped \(NiS_{2}\) . The average crystallite size was 27.72 nm, 32.64 nm and 32.43 nm for \(NiS_{2}\) , 0.15g and 0.25g Ag-doped \(NiS_{2}\) , respectively. Scanning electron microscope (SEM) images showed irregularly shaped nanoparticles with average size \(\sim 500 nm\) for all samples. Impedance spectroscopy measurements were conducted from 20 Hz– 2 MHz at temperatures from (150 K-290 K). The impedance plots consisting of two semi-circles indicate grain and grain boundary regions in Ag-doped \(NiS_{2}\) nanoparticles. The conduction in doped \(NiS_{2}\) was governed by the Correlated Barrier Hopping (CBH) mechanism. Using this model, the density of states and the minimum hopping distance were calculated to be \(\sim 10^{40} \, \textrm{eV}^{-1} \, \textrm{cm}^{-3}\) and \(\sim 10^{-28} \, \textrm{m}\) , respectively for doped \(NiS_{2}\) . At lower frequencies, high values of dielectric permittivity and dielectric tangent loss were observed, both increased with temperature and decreased with frequency. The peak shifting in the imaginary part of the electric modulus indicates various relaxation mechanisms. The broad and asymmetric peaks suggest non-Debye type relaxation.
