Zusammenfassung
The crystal structures of the lanthanide orthothiophosphates LnPS(4) (Ln = lanthanide) have been extensively investigated in the past. Up to now, however, single crystals of two members of this series - TmPS4 and YbPS4 - have not been available. Here, we report a modified synthesis protocol for TmPS4 and YbPS4 yielding single crystals suitable for X-ray diffraction. Both compounds crystallize in ...
Zusammenfassung
The crystal structures of the lanthanide orthothiophosphates LnPS(4) (Ln = lanthanide) have been extensively investigated in the past. Up to now, however, single crystals of two members of this series - TmPS4 and YbPS4 - have not been available. Here, we report a modified synthesis protocol for TmPS4 and YbPS4 yielding single crystals suitable for X-ray diffraction. Both compounds crystallize in the tetragonal space group I4(1)/acd (no. 142) with 16 formula units per unit cell and adopt the SmPS4 parent structure, like most reported lanthanide orthothiophosphates. The structures contain isolated [PS4](3-) tetrahedra and two crystallographically independent Le cations, which form trigonal-dodecahedral [LnS(8)](13-) polyhedra. The lattice parameters for TmPS4 are a =10.598(2), c=18.877(4) angstrom with V=2120.2(6) angstrom(3), and for YbPS4 a=10.577(2), c =18.827(4)angstrom with V= 2106.2(7) angstrom(3). The DFT-calculated electronic band structures indicate semiconducting behavior and reveal indirect band gaps of 2.1-2.2 eV, consistent with the reddish brown color of YbPS4, but underestimating the band gap of pale-yellow TmPS4. The Raman spectra are dominated by [PS4](3-) vibrations as confirmed by DFT-calculated phonon spectra. DTA measurements reveal remarkably high thermal stability compared to other known orthothiophosphate compounds.
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