Electrical and dielectric properties of In₂S₃ synthesized by solid state reaction

Indium sulfide (In₂S₃) material was synthesized by solid state reaction technique. The obtained powder was characterized by means of X-ray diffraction (XRD) and impedance spectroscopy. X-ray analysis shows that the obtained phase is β-In₂S₃ with cubic structure. The average grain size is about 42.6 nm, indicating the nanocrystalline nature of In₂S₃ material. The ac conductivity and dielectric properties of In₂S₃ have been investigated in a wide frequency (10 Hz–1 MHz) and temperature (0°C–100 °C) ranges. We found that the electrical conductance of In₂S₃ material is frequency and temperature dependent. The frequency dependence of ac conductivity follows the Jonscher's universal dynamic law. The variation of ac conductivity and the frequency exponent 's' are interpreted by the correlated barrier hopping (CBH) model. Activation energy value inferred from conductance spectrum matches very well with the value estimated from relaxation time, indicating that the relaxation process and conductivity have the same origin. In addition, the electronic conduction appears to be dominated by thermally activated hopping of small polaron (SPH) at high temperatures and by variable range hopping (VRH) at low temperatures. Values of dielectric constants ε′ and ε″ were found to decrease with frequency and increase with temperature. Such an observation is interpreted by Maxwell-Wagner-Sillars model (MWS). - Highlights: • In₂S₃ synthesized via solid state reaction technique. • At high-T the conduction process has been found to be suitable to SPH model. • VRH mechanism has been observed at low temperature. • The high relaxation is ascribed to be the MWS model.