Structural Investigation of Six Quinary Sulfides Synthesized via the Flux-Assisted Boron-Chalcogen Mixture (BCM) Method Eu2+ Containing Members of the RE3MTQ7 (M and T = Transition or Main Group Metals, Q = Chalcogens) FamilyStructural Investigation of Six Quinary Sulfides Synthesized via the Flux-Assisted Boron-Chalcogen Mixture (BCM) Method Eu2+ Containing Members of the RE3MTQ7 (M and T = Transition or Main Group Metals, Q = Chalcogens) Family
来源：ACS Publications
A series of six quinary rare-earth sulfides Ce1.854+Eu1.152+Na0.30SiS7, Ce1.914+Eu1.092+K0.18SiS7, Ce1.964+Eu1.042+Rb0.08SiS7, Ce1.984+Eu1.022+Cs0.05SiS7, Ce1.974+Eu1.032+Ag0.06SiS7, and Ce1.504+Eu1.502+CuSiS7 were obtained in an alkali iodide flux using the boron-chalcogen mixture (BCM) method. Single crystal X-ray diffraction was used to determine the structures of the high quality single crystals that were grown; their elemental compositions were confirmed by energy-dispersive spectroscopy (EDS). The compounds crystallize in the hexagonal crystal system in the noncentrosymmetric space group P63. The crystal structure consists of a three-dimensional network composed of mixed cerium and europium bicapped trigonal prisms, isolated SiS4 tetrahedra, and monovalent metals (Na, K, Rb, Cs, Ag, and Cu) located in cavities created by linked Ce/EuS8 polyhedra. The structures are charge-balanced when Ce and Eu are in their +4 and +2 oxidation states, respectively. The effective magnetic moment of Ce1.504+Eu1.502+CuSiS7 determined from the temperature dependence of the magnetic susceptibility data is consistent with the presence of Ce4+ and Eu2+. Clear correlations between the alkali ion site occupancy, the ionic radius of the alkali cations, and the average bond length of Ce4+/Eu2+–S, were established. UV–vis diffuse reflectance data were collected for Ce1.504+Eu1.502+CuSiS7 and a band gap of 1.9(1) eV was established.