Materials Chemistry and Physics 89 (2005) 211–215 Effect of Fe substitution on optical, electrical, electrochemical and dielectric properties of (Zn, Fe)S chalcogenide pellets S.H. Deulkar a , C.H. Bhosale a,∗ , M. Sharon b a Department of Physics, Electrochemical Materials Laboratory, Shivaji University, Kolhapur 416 004, India b Department of Chemistry, IIT Bombay, Powai, Mumbai 400 076, India Received 13 September 2003; received in revised form 17 October 2003; accepted 3 December 2003 Abstract In the present work ternary chalcogenide p-type semiconductor Zn 1-x Fe x S has been prepared by co-precipitation method for x = 0.18 and 0.4 concentrations of Fe. The precipitate was repeatedly sintered at 800 ◦ C 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. © 2004 Published by Elsevier B.V. Keywords: (Zn, Fe)S chalcogenide pellets; EPMA; Mott–Schottky plots; Electrical polarization 1. Introduction Semiconducting ZnS occurs in nature as cubic spha- lerite [1] and hexagonal wurtzite [2] with tetrahedrically bonded Zn 2+ . Due to its wide band gap of 3.7 eV at room temperature [3] it can be used as light emitting diode in the blue to UV spectral region. ZnS has a high re- fractive index due to which it can be used as a reflector [4] while its high transmittance in visible range, makes it suitable material for application as a dielectric filter [5]. Structurally similar to ZnS is the low band gap (E g = 0.85 eV) semiconductor FeS which too can crystallize in the cubic phase lattice [6]. An attractive alternative is represented by alloying iron monosulphide with ZnS and formation of a solid solution Zn 1-x Fe x S can be expected as the lattice mismatch is only 0.1% between the two chalcogenide compounds. In addition, it seemed to be interesting to study the variation of optical ∗ Corresponding author. Tel.: +91-2312690571; fax: +91-2312691533. E-mail address: bhosale ch@yahoo.com (C.H. Bhosale). band gap with increasing substitution of Zn 2+ with Fe 2+ ions in the tetrahedral sites. The aim of the present study is to synthesize (Zn, Fe)S compound in the form of polycrystalline pellets by using the method of co-precipitation and tune the optical energy gap by changing the relative Zn/Fe concentration ratio and decipher its repercussions on the flat band potential through electrochemical analysis. In addition the effect of Fe sub- stitution on dielectric properties is also studied. The present method of preparation is based on non-toxic, largely occur- ring elements which can be prepared in pellet form by us- ing low cost co-precipitation technique [7], carried out in a aqueous medium followed by drying of precipitate in inert argon atmosphere and annealing in vacuum sealed quartz ampoules. The structural, optical, thermoelectrical, electro- chemical and dielectrical properties of (Zn, Fe)S pellets have been investigated. 2. Experimental The pellet semiconductor electrodes used in this study were co-precipitated as per the following chemical 0254-0584/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.matchemphys.2003.12.002