A series of new rare-earth sulfide borates RE3S3BO3 (RE = Nd, Tb, Dy): Syntheses, structures and optical properties

Exploration of new compounds belonging to unusual families is always attractive for the everlasting development of material science. Here, three isomorphic rare-earth sulfide borates RE3S3BO3 (RE = Nd, Tb, Dy) have been obtained via a facile metal oxide-boron-sulfur solid-state routine. Their centrosymmetric triclinic structures feature 3D framework built by three types of REOxSy units, viz. REOS6, REO4S3, and REO3S6. Their structural relationship with similar phases and lanthanide contraction rule are discussed. Their optical band gaps are measured to be 2.59–2.70 eV, and the corresponding theoretical calculations are also performed. This work enriches the rarely studied chalcogenide borate system and is conducive to discovering more inorganic materials.