Li3La[PS4]2: The First Lithium Lanthanum Ortho‐Thiophosphate

Abstract

AbstractThe first lithium‐containing lanthanum ortho‐thiophosphate(V) with the formula Li3La[PS4]2 crystallizes orthorhombically in the space group Pbca with a=1053.51(6) pm, b=1920.62(11) pm, c=1165.83(7) pm and Z=8. Colorless single crystals were obtained from the reaction of lanthanum trichloride, dilithium sulfide and diphosphorus pentasulfide at 750 °C with lithium chloride as by‐product. The new structure of Li3La[PS4]2 features characteristic [PS4]3− anions and a crystallographically unique La3+‐cation position, surrounded by eight sulfur atoms from four [PS4]3− tetrahedra constructing a trigonal dodecahedron. These [LaS8]13− polyhedra are connected via [PS4]3− tetrahedra to form strongly corrugated layers ( ) spreading out parallel to the ac‐plane with Li+ cations in between residing in four‐, five‐ and sixfold sulfur coordination. Raman‐spectroscopic measurements were performed to visualize further vibrational modes, whereas diffuse reflectance spectroscopy verified the absorption of UV light, owing to the colorless appearance of the crystals. The optical band gap was found to be at 3.25 eV. Energy‐dispersive X‐ray spectroscopy (EDXS) measurements assured the absence of chlorine in the investigated single crystals. Calculations of Effective Coordination Numbers (ECoN) for each crystallographic position confirm the refined coordination environments for all atoms. Further investigations of the Madelung Parts of the Lattice Energies (MAPLE) point out the strong relationship of Li3La[PS4]2 with the ternary compounds of Li3[PS4] and La[PS4].