A CBED Study of CuAgSS
The room temperature phase of the compound CuAgS occurs in nature as the mineral stromeyerite. Its structure is stable up to approximately 90°C, above this temperature it transforms to a cation disordered structure with copper and silver ions mobile through a hexagonal close packed sulphur lattice. The structure of stromeyerite has been investigated by single crystal X-ray diffraction and was found to have an orthorhombic unit cell with possible space groups Cmcm (63) or Cmc21 (36). The structure was refined in Cmcm but only to an R factor of 0.30. Refinement in Cmc21 was not attempted. The structure is important as a starting model for those of other phases in the system Cu-Ag-S and consequently more precise information was required.Synthetic CuAgS was prepared from the binary sulphides by solid state reaction in vacuo at 300°C for one week. It was then ground to a powder and annealed at 70°C in N2 for a month.