• Rajiv Vaidya

      Articles written in Bulletin of Materials Science

    • Anisotropic behaviour of semiconducting tin monosulphoselenide single crystals

      T H Patel Rajiv Vaidya S G Patel

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      Single crystals of ternary mixed compounds of group IV–VI in the form of a series, SnS𝑥Se1-𝑥 (where 𝑥 = 0, 0.25, 0.50, 0.75 and 1), have been grown using direct vapour transport technique. The grown crystals were characterized by the X-ray diffraction analysis for their structural parameter determination. All the grown crystals were found to be orthorhombic. The microstructure analysis of the grown crystals reveals their layered type growth mechanism. From the Hall effect measurements Hall mobility, Hall coefficient and carrier concentration were calculated with all crystals showing 𝑝-type nature. The d.c. electrical resistivity measurements perpendicular to 𝑐-axis (i.e. along the basal plane) in the temperature range 303–453 K were carried out for grown crystals using four-probe method. The d.c. electrical resistivity measurements parallel to 𝑐-axis (i.e. perpendicular to basal plane) in the temperature range 303–453 K were carried out for the same crystals. The electrical resistivity measurements showed an anisotropic behaviour of electrical resistivity for the grown crystals. The anisotropic behaviour and the effect of change in stoichiometric proportion of S and Se content on the electrical properties of single crystals of the series, SnS𝑥Se1-𝑥 (where 𝑥 = 0, 0.25, 0.50, 0.75 and 1), is presented systematically.

    • X-ray diffraction studies of NbTe2 single crystal

      Neha Bhatt Rajiv Vaidya S G Patel A R Jani

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      NbTe2 is a member of transition metal dichalcogenide (TMDC) group. Single crystals of niobium ditelluride (NbTe2) have been grown by a chemical vapour transport technique using iodine as transporting agent. The composition of the grown crystals was confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and remaining structural characterization was also accomplished by X-ray diffraction (XRD) studies. Lattice parameters, volume and X-ray density have been carried out for the grown crystals. The particle size for a number of reflections has been calculated using Scherrer’s formula.

    • High pressure effect on MoS2 and MoSe2 single crystals grown by CVT method

      Madhavi Dave Rajiv Vaidya S G Patel A R Jani

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      Single crystals of MoS2 and MoSe2 were grown by chemical vapour transport method using iodine as a transporting agent and characterized by optical microscopy, energy dispersive analysis (EDAX), X-ray powder diffraction (XRD) and Hall mobility at room temperature. The variation of electrical resistance under pressure was monitored in a Bridgman anvil set-up up to 6.5 GPa to identify occurrence of any structural transition. MoS2 and MoSe2 do not undergo any structural transitions under pressure.

    • Optical and electrical properties of ZrSe3 single crystals grown by chemical vapour transport technique

      Kaushik Patel Jagdish Prajapati Rajiv Vaidya S G Patel

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      Single crystals of the lamellar compound, ZrSe3, were grown by chemical vapour transport technique using iodine as a transporting agent. The grown crystals were characterized with the help of energy dispersive analysis by X-ray (EDAX), which gave confirmation about the stoichiometry. The optical band gap measurement of as grown crystals was carried out with the help of optical absorption spectra in the range 700–1450 nm. The indirect as well as direct band gap of ZrSe3 were found to be 1.1 eV and 1.47 eV, respectively. The resistivity of the as grown crystals was measured using van der Pauw method. The Hall parameters of the grown crystals were determined at room temperature from Hall effect measurements. Electrical resistivity measurements were performed on this crystal in the temperature range 303–423 K. The crystals were found to exhibit semiconducting nature in this range. The activation energy and anisotropy measurements were carried out for this crystal. Pressure dependence of electrical resistance was studied using Bridgman opposed anvils set up up to 8 GPa. The semiconducting nature of ZrSe3 single crystal was inferred from the graph of resistance vs pressure. The results obtained are discussed in detail.

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