Synthesis and Electrical Conductivity of Nickel Sulphide
Over the last few years, a great deal of interest has been developed in the materials belonging to the nickel-sulphur system (Fig. 1) (LIN et al.), since their electrical and magnetic properties are technologically useful. Nickel sulphide Ni& belongs to this group (KULLERUD, W D ) . Literature survey revealed that Ni3S2 synthesized by different methods exhibits numerous inconsistent results with regard to the thermal stability, structure and physical properties of Ni3Sz (RAU; CONARD et al.; KULLERUD, VUND). However the electrical conductivity studies on Ni3S2 in the high temperature region is not reported. The purpose of the present paper is to report the low temperature crystallization process, XRD, EDX, TG, and electrical conductivity characteristics of Ni3S2.
Stoichiometric amounts of nickel and sulphur were mixed using a ball mill for several hours. The fine powder was loaded into a silica tube and evacuated to atmosphere pressure. The tube was sealed and heated at a temperature of 51OoC for 110 hours in a furnace (Lindburg). The hot sample tube was then quenched to room temperature. Repeated grinding, heating, and quenching of the sample intermittently in vacuum, resulted in pure single phase crystallization material 'with Ni3S2 stoichiometry. The resulted polycrystalline material was analysed by X-ray diffraction, using Siemens DIFF-500 diffractometer. EDX analysis of the material was carried out to identify the homogeneity and composition. Thermal stability of the material was determined using a TG apparatus. The electrical conductivity measurements were made by a d. c. four-probe method on a 4*2*2 m3 bar-shaped polycrystalline Ni&. Keithly model 224 was used as constant current source (25 mA) and voltage drop across the material was measured using a Keithly model 181 voltmeter. The electrical conductivity of Ni& was measured as a function of temperature between 300K and 1023K in vacuum.