Here we report the solid-state synthesis, crystal structure, and physiochemical characterization of 18 new members of the Ln3LiTQ7 family. The structure consists of LnQ8 bicapped trigonal prisms, TQ4 tetrahedra, and Li+ ions. The LnQ8 bicapped trigonal prisms are connected through corner, edge, and face sharing. All TQ4 tetrahedra are isolated from each other and share edges and corners with neighboring LnQ8 polyhedra. Both the LnQ8 and TQ4 polyhedra are inherently noncentrosymmetric (NCS) and align along the crystallographic c-axis, resulting in an overall structure lacking an inversion center. The 3-D structure formed by these polyhedra possesses channels where the Li+ are located and surrounded by six Q atoms in an octahedral pocket. Compounds of the La3CuSiS7 structure type are a special class of materials that crystallize in the NCS, hexagonal space group P63 (No. 173). Differential thermal analysis indicates that the tin-containing compounds melt at temperatures around 750 °C, while the compounds containing lighter tetrals do not show any thermal events up to 1000 °C. All compounds are stable at room temperature and ambient atmosphere. Optical diffuse reflectance spectroscopy was utilized to estimate the bandgaps, which are in the range of ~2.1 - 2.5 eV. Attenuated total reflectance FT-IR spectroscopy shows potentially high transparency in the near and mid-infrared regions. The linear relationships were found between bond distance and unit cell volume as a function of lanthanide radius. Bond valence sums, polyhedral distortions, and dipole moments were also calculated and will be discussed.

Synthesis, structure, and physicochemical characterization of novel quaternary lanthanide-chalcogenides with noncentrosymmtric structure and potential in IR-NLO applications

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.