Effect of Fe substitution on optical, electrical, electrochemical and dielectric properties of (Zn, Fe)S chalcogenide pellets

In the present work ternary chalcogenide p-type semiconductor Zn1-xFexS has been prepared by co-precipitation method for x = 0.18 and 0.4 concentrations of Fe. The precipitate was repeatedly sintered at 800degreesC in sealed quartz ampoules for a total of 165 h The material was then characterized by X-ray diffraction, X-ray fluorescence (XRF), EDAX, EPMA, diffuse reflectance spectroscopy, thermoelectric, electrochemical and capacitance measurement techniques. Compositional analysis techniques, viz. XRF, EDAX and EPMA reflected the composition of the solutions from which precipitation was carried out while X-ray reveals a sphalerite crystal structure. Capacitance measurements indicate that the relaxation effects are enhanced with increasing Fe substitution. Thermoelectric measurements indicate p-type conductivity in agreement with the results obtained by electrochemical analysis. The flat band potential V-fb has values 2.94 V (x = 0.18) and 2.66 V (x = 0.4) as obtained by Mott-Schottky plot. Similarly the optical band gap was found to decrease with increase in Fe concentration. (C) 200

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

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 degreesC. 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. (C) 2003 .