X-ray study of the superionic phase transition in Cu6PS5Br

The structure of the cubic (F-43m), superionic phase of the Cu6PS5Br crystal was redetermined at 295 and 420 K. A model of an ordered anion framework and two sublattices of Cu atoms creating a three-dimensional, highly defective network is proposed. Low temperature transitions were studied by DSC analysis, and measurements of the temperature dependence of the lattice parameters were performed using the X-ray diffraction Bond method. The superionic transition at T-s = 169 K was clearly seen in the DSC curve, but does not show any diffraction anomalies and seems to be an isostructural transformation. Rietveld refinement based on powder data collected at 50 K led to the structure of an ordered Cu ion framework with Cc space group. (C) 1999 Elsevier Science B.V. All rights reserved.