Structure of the quaternary alloy Zn0.6Mn0.4In2S4 from synchrotron powder diffraction and electron transmission microscopy

The aim of the present work was to determine the structure of the quaternary alloy Zn0.6Mn0.4In2S4 and to locate the Mn2+. This was accomplished by means of powder synchrotron X-ray diffraction, high-resolution microscopy and convergent-beam electron diffraction (CBED). The powder X-ray diffraction pattern was indexed in a rhombohedral cell, with cell constants a = 3.875 (2), c = 37.208 (4) angstrom, and possible space groups R(3) over bar m or R3m. Rietveld refinements using different cationic arrangements in these space groups were performed. A model in space group R3m, in which the tetrahedral and octahedral sites were occupied by different proportions of Zn, Mn and In atoms, gave the best result. The Rietveld refinement of this model led to figures of merit R-wp = 9.8%, R-p = 9.1% and chi(2) = 11.1. Selected-area electron diffraction patterns and high-resolution transmission electron micrographs along [001] reveal the rhombohedral configuration. CBED patterns perpendicular to [001], showing the distinctive 3m symmetry, confirmed space group R3m and the breaking of the centrosymmetry of the parent compound, ZnIn2S4.