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Germanium substitution in the well-known photovoltaic material Cu2ZnSnS4 has been previously shown to improve power conversion efficiencies, but detailed information about the local structure within solid solutions Cu2ZnSn1−xGexS4 has so far been lacking. Given the many ways the metal cations can be distributed, several structural models for the site distribution are possible. In conjunction with powder X-ray diffraction, multinuclear magnetic resonance spectroscopy (63/65Cu, 67Zn, 73Ge, and 119Sn) was applied to evaluate these models because these nuclei are sensitive to variations in the coordination environments around specific atoms. The 67Zn NMR spectra indicate that Zn atoms are in lower symmetry environments in Cu2ZnGeS4 than in Cu2ZnSnS4, as their different quadrupole coupling constants suggested. The 73Ge and 119Sn NMR spectra show gradual changes in chemical shift, indicating that Ge and Sn atoms are randomly mixed in tetrahedral sites within the entire range of solid solubility. The 63/65Cu NMR spectra collected at high field (21.1 T) reveal two distinct Cu sites for all members of Cu2ZnSn1−xGexS4, consistent with the structure model in space group I4¯, as also supported by DFT calculations of NMR parameters. Ge substitution increases the experimental band gap from 1.5 eV in Cu2ZnSnS4 to 2.0 eV in Cu2ZnGeS4 because the conduction band minimum is raised to higher energy, as shown by electronic structure calculations. [ABSTRACT FROM AUTHOR]

Sodium‐containing chalcogenide materials are emerging as a class of solid electrolytes for application in inexpensive all‐solid‐state sodium‐ion batteries due to their high ionic conductivity, abundance, and degree of synthetic and structural variability. Members of the solid solution Na3PS4−xSex, which are promising solid electrolytes for sodium‐ion batteries, are prepared by reaction at high temperature. With increasing substitution of S by Se, the structure transforms from tetragonal (space group P4¯$\bar{4}$21c for x = 0, 1) to cubic (space group I4¯$\bar{4}$3m for x = 2, 3, 4). Within the solid solution, the S and Se atoms are completely disordered in the environments around the P atoms, in accordance with a binomial distribution, as inferred by the 31P nuclear magnetic resonance (NMR) spectra. In 23Na NMR experiments conducted at different magnetic fields and temperatures, quadrupolar lineshapes are observed that are influenced by sodium ion dynamics; the activation energies decrease from 0.21 to 0.15 eV on progressing from the S‐ to the Se‐rich members. A dynamic model is proposed to account for the changes in the 23Na quadrupolar lineshapes by switching the orientations of the electric field gradient and chemical shift anisotropy tensors when Na+ ions hop to the four nearest Na sites. [ABSTRACT FROM AUTHOR]

The ternary antimonide CeNiSb3 has been prepared from an Sb flux or from reaction of Ce, NiSb, and Sb above 1123K. It crystallizes in the orthorhombic space group Pbcm with Z=12 and lattice parameters a=12.6340(7)Å, b=6.2037(3)Å, and c=18.3698(9)Å at 193K. Its structure consists of buckled square nets of Sb atoms and layers of highly distorted edge- and face-sharing NiSb6 octahedra. Located between the ∞2[Sb] and ∞2[NiSb2] layers are the Ce atoms, in monocapped square antiprismatic coordination. There is an extensive network of Sb-Sb bonding with distances varying between 3.0 and 3.4Å. The structure is related to that of RECrSb3 but with a different stacking of the metal-centered octahedra. Resistivity measurements reveal a shallow minimum near 25K that is suggestive of Kondo lattice behavior, followed by a sharp decrease below 6K. © 2003 Elsevier Inc. All rights reserved.