• J Gopalakrishnan

      Articles written in Bulletin of Materials Science

    • Preparation of some transition metal sulphides

      J Gopalakrishnan

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      Ternary sulphides, LnMS3 (Ln=rare earth metal; M=first row transition metal) and MV2S4 (M=Mg, Fe, Co, Ni and Zn) have been prepared by the reaction of appropriate ternary metal oxides with H2S or CS2/N2 vapours at elevated temperatures. Chemical analysis and x-ray powder diffraction of the products indicate formation of single-phases with unique crystal structures in many cases.

    • Transition metal chalcogenides exhibiting quasi-one-dimensional behaviour

      J Gopalakrishnan K S Nanjundaswamy

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      This paper presents a survey of transition metal chalcogenides (mainly sulphides and selenides) that exhibit unidimensional structural features and electronic properties arising therefrom. The survey indicates that linear, single-atom, chains of transition metals are formed in chalcogenides by sharing faces of MX6 (X=chalcogen) trigonal prisms or octahedra as well as corners or edges of MX4 tetrahedra. Besides these single-atom chain compounds, chalcogenides possessing multiple-atom chains are known among the early members of the transition series when the transition metal is in a low formal oxidation state. Typical examples of this class are Ti5Te4 and TlMo3Se3.

    • Insertion/extraction of lithium and sodium in transition metal oxides and chalcogenides

      J Gopalakrishnan

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      Lithium and sodium can be reversibly inserted into a variety of transition metal oxide and chalcogenide hosts at low temperatures. The reaction is essentially topochemical involving electron-transfer and accompanying diffusionless transformation of the anion array in many cases. Alkali metal insertion/extraction reactions provide new routes for the synthesis of novel solids exhibiting unusual structure and properties. It appears that while the structure of the insertion compound is determined by the host structure and the size of the alkali metal ion, the extent of insertion/extraction is decided by the redox characteristics and electronic conductivity of the host.

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      Posted on October 12, 2020

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      Chemical Sciences 2020

      Prof. Surajit Dhara — School of Physics, University of Hyderabad, Hyderabad
      Physical Sciences 2020

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