No abstract

Four probe electrical conductivity measurements from 15 to 300 K demonstrate that the mixed-valence compound Na3Cu4S4 is metallic. Measurements on single crystals reveal that the conductivity is highly anisotropic, with enhanced conductivity parallel to the crystal needle axis, corresponding to pseudo-one-dimensional [Cu4S41 23~]" columns in the structure. For single crystals, a» increases from 15000 IT1 cm"1 at 300 K to 300000 "1 cm"1 at 15 K. A small, temperature-independent magnetic susceptibility is consistent with metallic behavior. Diffuse-reflectance spectra support the formulation of this compound as a class 3B mixed-valence S2"/S" solid.

Das durch Hochtemp.‐Reaktion zwischen Cu, K2CO3 und Sdarstellbare KCu4S3 kristallisiert in einer eigenen Schichtstruktur (P4/mmm, P422 oder P42m, Z=1).

Wie Messungen der elektrischen Leitfähigkeit zwischen 15 und 300 K zeigen, ist die gemischtwertige Titelverbindtmg metallisch.