Syntheses, Structures, and Physical Properties of the New Quaternary Rare-Earth Chalcogenides RbNd2CuS4, RbSm2CuS4, CsLa2CuSe4, CsSm2CuSe4, RbEr2Cu3S5, CsGd2Ag3Se5, CsTb2Ag3Se5, and Rb2Gd4Cu4S9

✍ Scribed by Fu Qiang Huang; James A. Ibers

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 445 KB
• Volume: 158
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2001.9110

✦ Synopsis

The R 1 indices are 0.0257, 0.0255, and 0.0241. The cell dimensions of Rb 2 Gd 4 Cu 4 S 9 (a, b, c (A s ),

(3)) is 13.897(1), 3.9883(3), 16.054(1), 109.273(1), and the R 1 index is 0.0199. All eight compounds have closely related three-dimensional tunnel structures. All alkali metal atoms in the tunnels are coordinated to eight Q atoms. Their anionic frameworks are built from LnQ 6 octahedra and MQ 4 tetrahedra. ALn 2 CuQ 4 contains 1 [CuQ 3 ] chains of vertex-sharing tetrahedra; Rb 2 Gd 4 Cu 4 S 9 contains 1 [Cu 4 S 8 ] chains of tetrahedra; and ALn 2 M 3 Q 5 contains 2 [M 3 Q 5 ] layers of tetrahedra. Rb 2 Gd 4 Cu 4 S 9 and RbEr 2 Cu 3 S 5 , which are paramagnetic, obey the Curie+Weiss law, and have e4ective magnetic moments of 7.9(2) B for Gd 3؉ and 9.43(5) B for Er 3؉ . A band gap of 1.94 eV for Rb 2 Gd 4 Cu 4 S 9 was deduced from its di4use re6ectance spectrum, and the typical 4f+4f optical transitions for Er 3؉ were found in RbEr 2 Cu 3 S 5 at about 1.6, 1.9, and 2.5 eV.