Structure studies of some ternary copper chalcogenides

Abstract: Copper has in its heavier chalcogenides often a high mobility in the solid state. This behaviour has also be found for some ternary compounds where copper appears to govern the observed phase transitions and structural transformations. The focus of this thesis has been to investigate and characterise these transformations with the aim of relating the changes in structure to changes in physical properties.The thesis is divided into three parts. The first is a summary of the synthesis and characterisation of the compounds while the second relates to the structure refinement. The topic of non-ideal crystal behaviour is outlined by introducing disorder and incommensurate ordering. The third part describes the investigated structures and the various transformations observed for these compounds with a particular emphasis on copper deficient ACu7S4, (A = NH4+, TI+, K+, Rb+). The thermal and resistivity characteristics are linked to the behaviour of copper. A possible explanation for the observed differences between the sulphide and selenide analogues are also introduced.