New Oxychalcogenides for Electronic, Magnetic and Optical Applications

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Solid state chemistry has impact on many areas of modern life. Examples are numerous: essentially all the petrol we use has been processed using solid state porous catalysts; the fuel cells and rechargeable batteries in modern portable devices rely on materials produced by solid state chemists; metal alloys and metal oxides form key components of all electronic goods. Many of the materials in use today are based on metal oxides. In these materials electronic, optical and magnetic properties are usually controlled by substituting different metal ions in the structure. This influences the electron count in metal-oxygen antibonding bands which in turn changes properties; seemingly minor changes in chemical composition can dramatically change a material's properties. In this proposal we seek funding to investigate the chemistry of oxychalcogenides, phases which simultaneously contain O2- and S2- or Se2- anions. We believe that these materials are exciting for several reasons. Firstly, they are a relatively under-explored family and there are significant opportunities to prepare new materials with properties influenced by the simultaneous presence of two different anions. Secondly, the bonding in such materials is significantly different to that in oxides and the higher degree of covalency leads to a combination of metal and anion character in the highest energy occupied electronic states. This offers the possibility of preparing phases such as p-type transparent conductors and to produce materials with potentially exploitable magnetic properties. Thirdly, it's possible to use the chalcogenide layers in materials to stabilise oxide layers with structural arrangements that aren't found in pure oxide materials. The novel structures of such layers suggest novel electronic and magnetic properties may be discovered and exploited.In one work strand we aim to develop the chemistry of materials related to [Bi2LnO4][Cu2Se2] (Ln is a 3+ lanthanoid element). There are a wide range of chemical substitutions and related materials we hope to prepare with a range of potentially interesting properties. A second strand targets [Ln2O2Q2][M2O] (M is a transition metal) materials which contain an unusual [M2O] layer of atoms which is structurally related to layers found in many important materials but has M and O positions reversed. We wish to explore the range of such materials that can be prepared and investigate their structural, magnetic and electronic properties. A final strand of the work will use our knowledge of the kinds of features found in known oxychalcogenides to target new structure types.In summary, this project will allow us to prepare exciting new materials and investigate their structural, electronic, optical and magnetic properties.