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Characterization of Mixed Crystals in the System Cu 2 Mn x Co 1− x GeS 4 and Investigations of the Tetrahedra Volumes
Author(s) -
Bernert Thomas,
Pfitzner Arno
Publication year - 2006
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200500430
Subject(s) - crystallography , orthorhombic crystal system , tetragonal crystal system , crystal structure , superstructure , materials science , tetrahedron , type (biology) , wurtzite crystal structure , chemistry , physics , geology , paleontology , thermodynamics , hexagonal crystal system
Abstract In a series of investigations on normal tetrahedral compounds we present mixed crystals in the system Cu 2 Mn x Co 1− x GeS 4 (0 < x < 1) and an inspection of their tetrahedra volumes. Cu 2 CoGeS 4 crystallizes tetragonal in a stannite type structure, Cu 2 MnGeS 4 crystallizes orthorhombic in the wurtzstannite structure type. The crystal structures of Cu 2 CoGeS 4 and Cu 2 Mn 0.68 Co 0.32 GeS 4 were refined from single crystal diffraction data. The refinement of Cu 2 CoGeS 4 converged to R = 0.0547 and wR 2 = 0.0847 for 299 unique reflections. The refinement of Cu 2 Mn 0.68 Co 0.32 GeS 4 converged to R = 0.0481 and wR 2 = 0.0877 for 1556 unique reflections. From these data the tetrahedra volumes of the end members and of Cu 2 Mn 0.68 Co 0.32 GeS 4 are calculated. In Cu 2 CoGeS 4 tetrahedra [ M S 4 ] are similar in size. In contrast, the differences of the volumes of the polyhedra [ M S 4 ] in the orthorhombic wurtzite superstructure type compounds Cu 2 MnGeS 4 and Cu 2 Mn 0.68 Co 0.32 GeS 4 are significant ( M = Cu, Mn, (Mn 0.68 Co 0.32 ), Co, Ge). From x = 0 to x = 0.5 the tetragonal structure type dominates while from x = 0.7 to the Cu 2 MnGeS 4 end member the products crystallize in the orthorhombic structure type. Melting points of the mixed crystals decrease linearly with increasing manganese content.