Preparation of non-stoichiometric (Zn,Fe)S chalcogenides and evaluation of their thermal, optical and electrical properties Original Research Article

Non-stoichiometric ternary chalcogenides, Zn1−xFexS, were prepared by co-precipitation of ZnS and FeS by Na2S from aqueous solutions containing FeSO4 and ZnSO4 and sintering of pellets of the co-precipitate repeatedly between 800 and 1000 °C. The chemical composition of the resulting solids as analyzed by XRF, EDAX, and EPMA, reflected the composition of the solutions from which precipitation was carried out, with Fe contents up to x=0.4. X-ray diffraction indicated the presence of solid solutions, Zn1−xFexS (sphalerite). Electrical resistivity studies indicated that the compounds were semiconducting. From the temperature dependence of the resistivity, thermal bandgaps were found to be decreasing with increasing Fe content, in agreement with values on optical bandgaps as estimated from diffuse optical reflectance measurements as a function of wavelength. TEP (Thermo Electric Power) measurements indicated p-type conductivity for most samples.