Synthesis and Characterization of Cu3NbSe4 and KCu2TaSe4

✍ Scribed by Ying-Jie Lu; James A. Ibers

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 183 KB
• Volume: 107
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1993.1323

✦ Synopsis

(\mathrm{Cu}{3} \mathrm{NbSe}{4}) has been synthesized from a stoichiometric reaction of the elements at (950^{\circ} \mathrm{C}). The material, which has the sulvanite (\left(\mathrm{Cu}{3} \mathrm{VS}{4}\right)) structure, crystallizes in space group (T_{d}^{1}-P \overline{4} 3 m) of the cubic system with one formula unit in a cell with (a=5.638(1) \AA) at (-165^{\circ} \mathrm{C} . \mathrm{Cu}{3} \mathrm{NbSe}{4}) has a three-dimensional structure with edge-sharing of (\mathrm{CuSe}{4}) and (\mathrm{NbSe}{4}) tetrahedra and corner-sharing among (\mathrm{CuSe}{4}) tetrahedra extending equally in all directions. (\mathrm{KCu}{2} \mathrm{TaSe}{4}) was prepared from a reaction of (\mathrm{K}{2} \mathrm{Se}{5}, \mathrm{Cu}, \mathrm{Ta}), and Se in the ratio (1: 4: 2: 3) at (850^{\circ} \mathrm{C}). (\mathrm{KCu}{2} \mathrm{TaSe}{4}) crystallizes in space group (C{8}^{4}-C c) of the monoclinic system with four formula units in a cell of dimensions (a=5.660(1), b=18.829(4), c=7.662(2) \AA), (\beta=90.04(3)^{\circ}) at (-165^{\circ} \mathrm{C}). In this structure the (\mathrm{Ta}) and two independent (\mathrm{Cu}) atoms are in tetrahedral sites. The (\mathrm{CuSe}{4}) and (\mathrm{TaSe}{4}) tetrahedra share edges and corners to make up two-dimensional layers. These layers are separated from one another by (\mathrm{K}^{+})ions. (\mathrm{KCu}{2} \mathrm{TaSe}{4}) is not isostructural with (\mathrm{KCu}{2} \mathrm{NbSe}{4}), although the structures are similar. (1993 Academic Press, Inc.