Growth of ternary teallite (PbSnS2) for hydrogen sensing and its dielectric relaxation, ac conductivity and modulus spectroscopic studies

We have synthesized ${\mathrm{PbSnS}}_2$ by conventional solid-state technique. The X-ray diffraction (XRD) confirmed formation of pure orthorhombic ${\mathrm{PbSnS}}_2$. Mixed shape morphology was observed by scanning electron microscopy (SEM). A direct band gap of $\sim$2.89 eV was estimated from uv-vis spectroscopy. Energy dispersive x-ray spectroscopy (EDS) confirmed the presence of lead, tin and sulfur only. The ac electrical measurements were performed from 218 K–298 K with an applied frequency varied from 20 Hz to 2 MHz. The ac conductivity obeyed Jonscher’s power law. The $s$ parameter variation with temperature suggested non-overlapping small polaron hopping (NSPH) as a dominant conduction mechanism for ${\mathrm{PbSnS}}_2$. From NSPH model, density of states (DOS) , hopping energy and hopping distance were calculated to be ($\sim$ $10^{21}$–$10^{23}$ ${\mathrm{eV}}^{-1}{\mathrm{cm}}^{-3}$), $\sim$ $10^{-10}$ m and ($\sim 0.35\text{–}0.48\mathrm{eV}$), respectively. The ${\mathrm{PbSnS}}_2$ responded to $H_2$ gas with response of 14% at 160 mbars. Moreover, ${\mathrm{PbSnS}}_2$ sensors showed reproducibility, stability and selectivity towards $H_2$.