Syntheses, crystal and electronic structures of ternary rare-earth zirconium sulfides, RE2ZrS5 (RE = Y, Ce and Pr)

摘要

Three ternary rare-earth zirconium sulfides, Y2ZrS5 (1), Ce2ZrS5 (2) and Pr2ZrS5 (3), have been synthesized by high-temperature solid-state reactions. They crystallize in the space group Pnma of the orthorhombic system, belonging to the Y2HfS5 structure type. There are two types of building units in their structures, RES8 bicapped trigonal prisms and ZrS7 monocapped trigonal prisms. Their structures feature polyanionic {[ZrS5](6-)}(n) chains and cubane-like {[RE4Zr2S6](8+)}(n) double chains along the b direction, and RE atoms occupying the polyhedral interspaces between the former chains. The lanthanide contraction phenomenon in the series of RE2ZrS5 (RE = La-Nd, Sm and Gd) is discussed. The electronic band structure and density of states calculations using Material Studio indicate that the direct optical energy gap of 1 is 1.39 eV and the optical absorption is mainly ascribed to the charge transition from S-3p to Y-4d and Zr-4d states. (C) 2016 Elsevier B.V. All rights reserved.