Dielectric Relaxation, Electrical Conductivity, Dielectric Permittivity, and Correlated Barrier Hopping Conduction Mechanism Analysis in Ag Doped Bi₂S₃ at Low Temperatures

Abstract

Pure and 6% Ag doped bismuth sulfide (Bi2S3) were synthesized via solid‐state reaction method at 500 °C. The X‐ray diffraction method confirmed the orthorhombic phase with average crystallite size ∼25 nm and average lattice strain ∼0.5% and ∼0.6% for pure and 6% Ag doped Bi2S3. The scanning electron microscope (SEM) images confirmed nanobelt morphology. A direct bandgap of ∼3.3 and ∼3.4 eV for pure and doped Bi2S3 was estimated using UV–vis spectroscopy, respectively. AC measurements were performed from 200 Hz to 2 MHz at temperature 223–298 K. Investigation of Nyquist plots of 6% Ag doped Bi2S3 nanobelts suggested space‐charge‐dependent behavior and indicated an negative temperature coefficient of resistance (NTCR). AC conductivity adhered to Jonscher's power law in which the decreasing trend of s‐parameter with increasing temperature indicates correlated barrier hopping conduction mechanism. From this model, hopping distance (∼10−9–10−11 m) and density of states (∼1022–1023 eV−1 cm−3) were estimated. The dielectric permittivity exhibited dispersion at low frequencies due to the combined effect of electronic, ionic, and interfacial polarizations. Presence of two semicircular arcs in the complex modulus analysis suggested the presence of both grain and grain‐boundary effects.