title: Syntheses, structures, physical and electronic properties of quaternary semiconductors: Cs[RE9Cd4Se18] (RE = Tb-Tm).
abstract: Five new quaternary rare-earth selenides, Cs[RE9Cd4Se18] (RE = Tb-Tm), which are the first examples with closed cavities in the quaternary A/RE/Cd/Q (A = alkali metal; RE = rare earth metal; Q = chalcogenide) system, have been synthesized by high-temperature solid state reactions with a modified reactive CsCl flux. Single crystal X-ray diffraction analyses show that these isostructural materials adopted a known BaV13O18-structure type in the trigonal space group R3[combining macron] (no. 148) with cell parameters of a = 17.773(2)-17.489(6) Å, c = 9.918(2)-9.765(5) Å and Z = 3. The structure is composed of MSe6 (centered by disordered RE and Cd) and RESe6 octahedra that share edges to form a 3D framework, inside which the cuboctahedral Se12 closed cavities accommodate Cs cations. It is interesting to note that these compounds exhibit atomic distributions different from the recently reported Mn-compounds Cs[RE9Mn4Se18]. In Cd-compounds, Cd and RE atoms are statistically mixed only at one of the 18f sites; the rest of the RE atoms are fully occupied at the two framework sites: 18f and 3a. Moreover, the theoretical studies have greatly aided the understanding of the site-preference about a Cd atom in the 3D framework. The synthesis, structural characterization, electronic band structure as well as physical properties of the title compounds are also discussed.
authors.affiliation: Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People's Republic of China. liming_wu@fjirsm.ac.cn.
authors.forename: Hua
authors.initials: H
authors.lastname: Lin
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Peng-Fei
authors.initials: PF
authors.lastname: Liu
authors.forename: Ju-Song
authors.initials: JS
authors.lastname: Yu
authors.forename: Yu-Jun
authors.initials: YJ
authors.lastname: Zheng
authors.forename: Khan Muhammad
authors.initials: KM
authors.lastname: Ali
authors.forename: Ling
authors.initials: L
authors.lastname: Chen
authors.forename: Li-Ming
authors.initials: LM
authors.lastname: Wu