Durham E-Theses Synthesis, Structure and Properties of Metal Oxychalcogenides TUXWORTH, ANDREW,JAMES How to cite: TUXWORTH, ANDREW,JAMES (2014) Synthesis, Structure and Properties of Metal Oxychalcogenides, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/9497/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk Abstract “Synthesis, Structure and Properties of Metal Oxychalcogenides” PhD Thesis Andrew J. Tuxworth December 2013 Chapter 1 gives a brief review of oxychalcogenide materials and their properties, with particular focus on structures similar to the systems discussed in the later chapters. These oxychalcogenides, are of interest due to their potentially interesting magnetic and electronic properties. Chapter 2 discusses the synthetic methods and characterisation techniques used throughout this thesis. The theory behind both single crystal and powder diffraction techniques used in this work is described. Chapter 3 describes the synthesis of a new ZrCuSiAs-related transition metal containing oxychalcogenide La2O2ZnSe2. The structure of La2O2ZnSe2 is reported, deduced from symmetry adapted distortion mode analysis of laboratory X-ray powder diffraction data, and confirmed by Rietveld analysis of combined X-ray and neutron powder diffraction data. The variable temperature structural properties of La2O2ZnSe2 are also reported alongside diffuse reflectance measurements. Chapter 4 discusses the variable temperature structural, electronic and magnetic properties of A4O4TiSe4 (A = Sm, Gd, Tb, Dy, Ho, Er, & Y). The variable temperature structural properties of the compounds are also reported. Electronic measurements show these materials are semiconductors while SQUID magnetometry measurements suggest these materials order antiferromagnetically at low temperatures. Chapter 5 reports the synthesis of an extended family of ternary oxychalcogenides with A4O4Se3 composition. Three new structures for this composition have been solved using a combination of single crystal and powder X-ray diffraction. The new γ and δ-structures have been shown to contain a highly disordered layer of selenium anions. The variable temperature structural properties of the series are also reported. Chapter 6 discusses the synthesis of single crystals of La2O2Se2Fe2O, La2O2Se2Mn2O and Pr2O2Se2Mn2O. A comparison of the structural properties of the A2O2Se2Mn2O materials is given, alongside determination of the incommensurately modulated cell of La2O2Se2Mn2O. Chapter 7 reports synthesis a new 3D oxychalcogenide LaInS2O. Its structure is solved from X- ray powder diffraction measurements. Chapter 8 describes the method of temperature calibration used for variable temperature X- ray powder diffraction measurements used in this work. Synthesis, Structure and Properties of Metal Oxychalcogenides Andrew J. Tuxworth M.Chem (Dunelm) Durham University Supervisor: Prof. John S. O. Evans A thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy Department of Chemistry Durham University 2013 Table of Contents Abstract ......................................................................................................................................... 1 Abbreviations ................................................................................................................................ 7 Declaration & Statement of Copyright ......................................................................................... 8 Acknowledgments ......................................................................................................................... 9 Chapter 1: Introduction and Literature Review .......................................................................... 10 1.1 Introduction ...................................................................................................................... 10 1.2 Layered oxychalcogenides ................................................................................................ 10 1.2.1 Ternary materials, AxOyQz and BxOyQz ........................................................................ 10 1.2.2 Quaternary AOMQ materials with the ZrCuSiAs structure ........................................ 15 1.2.3 A2O2Q2M2O type materials ......................................................................................... 23 1.3 3-Dimensional oxychalcogenides A/O/M/Q ..................................................................... 29 1.3.1 A/O/Ti/Q compounds................................................................................................. 29 1.3.2 A/O/V/Q compounds ................................................................................................. 30 1.3.3 ACrOQ2 compounds ................................................................................................... 31 1.3.4 A/O/M/Q (M = Mn, Fe) compounds ......................................................................... 32 1.3.5 La/O/In/S compounds ................................................................................................ 33 1.4 Conclusions and project aims ........................................................................................... 35 References .............................................................................................................................. 36 Chapter 2: Synthetic Methods and Analytical Techniques ......................................................... 40 2.1 Introduction ...................................................................................................................... 40 2.2 Experimental details ......................................................................................................... 40 2.2.1 Preparation of AxOy starting reagents ........................................................................ 41 2.2.2 Synthesis of TiSe2 starting reagent ............................................................................ 41 2.2.3 Synthesis of La2O2ZnSe2 ............................................................................................. 41 2.2.4 Synthesis of A4O4TiSe4 (A = Sm, Gd, Tb, Dy, Ho, Er and Y) ......................................... 43 2.2.5 Synthesis of A4O4Se3 (A = Nd, Sm-Er, Yb, Y) ............................................................... 44 2.2.6 Synthesis of A2O2Se2M2O (A = La, Pr, M = Fe, Mn) ..................................................... 45 2.2.7 Synthesis of LaInS2O ................................................................................................... 46 2.3 X-ray diffraction ................................................................................................................ 47 2.3.1 Diffraction from commensurate materials ................................................................ 47 2.3.2 Incommensurate materials ........................................................................................ 48 2.4 Single crystal X-ray diffraction .......................................................................................... 51 2.4.1 Instruments ................................................................................................................ 51 3 2.4.2 Crystal mounting procedure and selection ................................................................ 52 2.4.3 Indexing, symmetry determination and integration ................................................. 52 2.4.4 Structure solution and least squares refinement ...................................................... 53 2.5 Powder diffraction ............................................................................................................ 54 2.5.1 X-ray powder diffraction instruments ....................................................................... 54 2.5.2 Sample preparation ................................................................................................... 55 2.5.3 Analysis of X-ray powder diffraction data .................................................................. 56 2.5.4 Rietveld refinement ................................................................................................... 56 2.5.5 Methodologies for analysis of multiple datasets ....................................................... 57 2.5.6 Peak fitting and indexing in TOPAS ............................................................................ 57 2.5.7 Pawley refinement ..................................................................................................... 58 2.5.8 Structure solution from powder diffraction data ...................................................... 58 2.6 Neutron powder diffraction .............................................................................................. 59 2.6.1 Neutron diffraction 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