Abstract
We report a simple, economical and low temperature route for phase-pure synthesis of two distinct phases of Cu–Sb–S, chalcostibite (CuSbS
2
) and tetrahedrite (Cu
12
Sb
4
S
13
) nanostructures. Both compounds were prepared by the decomposition of a mixture of
bis
(
O
-ethylxanthato)copper(II) and
tris
(
O
-ethylxanthato)antimony(III), without the use of solvent or capping ligands. By tuning the molar ratio of copper and antimony xanthates, single-phases of either chalcostibite or tetrahedrite were obtained. The tetrahedrite phase exists in a cubic structure, where the Cu and Sb atoms are present in different coordination environments, and tuning of band gap energy was investigated by the incorporation of multivalent cationic dopants, i.e. by the formation of Zn-doped tetrahedrites Cu
12−x
Zn
x
Sb
4
S
13
(x = 0.25, 0.5, 0.75, 1, 1.2 and 1.5) and the Bi-doped tetrahedrites Cu
12
Sb
4−x
Bi
x
S
13
(x = 0.08, 0.15, 0.25, 0.32, 0.4 and 0.5). Powder X-ray diffraction (p-XRD) confirms single-phase of cubic tetrahedrite structures for both of the doped series. The only exception was for Cu
12
Sb
4−x
Bi
x
S
13
with x = 0.5, which showed a secondary phase, implying that this value is above the solubility limit of Bi in Cu
12
Sb
4
S
13
(12%). A linear increase in the lattice parameter
a
in both Zn- and Bi-doped tetrahedrite samples was observed with increasing dopant concentration. The estimated elemental compositions from EDX data are in line with the stoichiometric ratio expected for the compounds formed. The morphologies of samples were investigated using SEM and TEM, revealing the formation of smaller particle sizes upon incorporation of Zn. Incorporation of Zn or Bi into Cu
12
Sb
4
S
13
led to an increase in band gap energy. The estimated band gap energies of Cu
12−x
Zn
x
Sb
4
S
13
films ranges from 1.49 to 1.6 eV, while the band gaps of Cu
12
Sb
4−x
Bi
x
S
13
films increases from 1.49 to 1.72 eV with increasing x.