  Electrical and thermal transport properties of Cu-deficient kuramite
Cu3-xSnS4 (CTS) was examined as a possible earth-abundant thermoelectric
material. Crystallographic structure of CTS was characterized by partial
disorder between Cu and Sn. In contrast to semiconducting electrical transport
of related compounds, such as Cu2ZnSnS4 and Cu3SbS4, metallic conduction with
an electrical resistivity of 0.4 mohmcm and a carrier concentration of 3 \times
10^21 cm-3 was observed at 300 K. Lattice thermal conductivity was calculated
at 2.6 Wm^-1K^-1, which was probably reduced by Cu-deficiency and or partial
cation disorder. Density functional theory calculation indicates valence band
was composed of hybridization between Cu 3d orbitals and S 3p orbitals.
