title: KCaEr2CuS5: a new pentanary rare-earth layered chalcogenide without substitutional disorder.
abstract: A new pentanary rare-earth chalcogenide without substitutional disorder, KCaEr2CuS5, was obtained from reaction of the Er-Ca-Cu-S precursor with KBr flux by either a two-step flux method or a direct reaction of the mixture of the binary components (1Cu2S:2Er2S3:3CaS) with excess KBr as flux. KCaEr2CuS5 crystallizes in the orthorhombic space group Cmcm (No. 63) with a = 3.9327(5) A, b = 13.410(2) A, c = 17.042(2) A, V = 898.8(3) A(3), Z = 4, R = 0.0632, and Rw = 0.0627. The KCaEr2CuS5 structure consists of four different building units: ErS6 octahedra, CaS6 octahedra, CuS4 tetrahedra, and KS6 trigonal prisms; it is characterized by [Er2CuS5]3- layers that are formed by the interconnection of double ErS6 octahedral chains with CuS4 tetrahedral chains in the a-c plane. K+ and Ca2+ cations are located in the cavities defined by S2- anions between the [Er2CuS5]3- layers. KCaEr2CuS5 is a semiconductor with an estimated band gap of 2.4 eV and shows a Curie-Weiss paramagnetic behavior in the 5-300 K range.
authors.affiliation: State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China.
authors.forename: Hui-Yi
authors.initials: HY
authors.lastname: Zeng
authors.forename: Hansjürgen
authors.initials: H
authors.lastname: Mattausch
authors.forename: Arndt
authors.initials: A
authors.lastname: Simon
authors.forename: Fa-Kun
authors.initials: FK
authors.lastname: Zheng
authors.forename: Zhen-Chao
authors.initials: ZC
authors.lastname: Dong
authors.forename: Guo-Cong
authors.initials: GC
authors.lastname: Guo
authors.forename: Jin-Shun
authors.initials: JS
authors.lastname: Huang