Solvothermal routes to new chalcogenide materials

Abstract

Chapter 1 reviews the literature on the use of solvothermal methods for synthesising metal chalcogenide materials and the structures of copper containing metal chalcogenide materials based on tetrahedral bonding motifs. Chapter 2 contains details of the structural characterisation, physical property measurements and synthetic methods used throughout this work. Chapter 3 summarises work on ways of modelling preferred orientation and anisotropic peak broadening in powder X-ray diffraction (PXRD) data using spherical harmonic functions; these are applied to data from compounds discussed elsewhere in this thesis. Chapter 4 discusses the synthesis of Cu(_2)MX(_4) materials (M = W or Mo; X = S, Se or S/Se) and PPh(_4)CuWSe(_4) using a solvothermal method. The effects of synthesis temperature and pressure on the structures of the materials formed have been investigated. The materials have been characterised by PXRD, the structures of ICu(_2)WS(_4) and PPh(_4)CuWSe(_4) have been solved from powder diffraction data; the structures of other materials have been determined by Rietveld refinement. Variable temperature diffraction experiments and physical property measurements have been performed on selected materials. Chapter 5 describes structural studies on (PPh(_4))(_2)M(WS(_4)(_2))(M = Co, Ni, Zn) materials. Single crystal diffraction has been used to further investigate the complex superstructure of the known polymorph of the zinc material. A new zinc polymorph has been discovered and its structure studied by PXRD. The structure of the Ni containing material has been determined directly from powder diffraction data. Chapter 6 outlines preliminary work on materials which are tentatively described as M(_x)WS(^2) intercalates. X-ray diffraction, magnetic measurements and Energy Dispersive-ray Analysis have all been used to probe their properties. Chapter 7 is a discussion of the structure solution of (NH(_4))2WS(_3)O from powder diffraction data and a variable temperature diffraction experiment on the same material.