Cation ordering and physicochemical characterization of the quaternary diamond-like semiconductor Ag2CdGeS4

The quaternary diamond-like semiconductor, Ag2CdGeS4, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag2CdGeS4 in the orthorhombic, noncentrosymmetric space group Pna21 with a=13.7415(8) Å, b=8.0367(5) Å and c=6.5907(4) Å, in contrast to a previously published model in Pmn21 from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna21 space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag2CdGeS4 exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material.