CuInTe2 chalcopyrite semiconductor and the ordered defect compounds of the Cu2Te–In2Te3 pseudo‐binary system have recently emerged as suitable candidates for thermoelectric applications. In this article, the crystal structure, optical, and electrical properties of Cu3In7Te12, a member of this ternary system, have been studied. It was established that this material crystallizes in a tetragonal structure with space group Ptrue4¯2c. The analysis of the optical absorption spectrum near the fundamental absorption edge shows that the energy gap is direct and the band gap varies from 1.030 to 0.952 eV between 10 and 300 K. From the analysis of electrical data, it was found that above 160 K, the electrical conduction is due to the activation of a shallow acceptor level of about 10 meV, and the value of the hole‐effective mass is mh = (1.18 ± 0.35) me. In the temperature range from 160 to 130 K, variable range hopping (VRH) mechanism of Mott‐type in the impurity band is observed. At high temperatures, the mobility is explained by taking into account the scattering mechanism of the charge carriers by donor–acceptor defect pairs, ionized and neutral impurities, acoustic and non‐polar optical phonons. In the low temperature region, the mobility data can be explained by an expression related to Mott law for VRH conductivity.

The crystal structure of the ordered vacancy compound (OVC) Cu 3 In 7 Te 12 is analyzed using powder X-ray diffraction data. It is found that this OVC crystallizes with a chalcopyrite-related structure, in the tetragonal space group P 4 2c (Nº 112), with unit cell parameters and volume a = 6.1720(2) Å, c = 12.3597(8) Å, and V = 470.83(4) Å 3. The Rietveld refinement of 28 instrumental and structural parameters led to R p = 9.27 %, R wp = 10.30 %, R exp = 6.95% and S = 1.48, for 4501 step intensities and 130 independent reflections, respectively. This compound is isostructural with Cu 3 In 7 Se 12 , and has a defect adamantane structure.

Here we report a study of the absorption spectrum of Mn‐doped bulk crystal samples of Cu2SnSe3 which are also characterized by X‐ray diffraction (XRD), electrical properties, and Raman spectroscopy. From the electrical data it is found that above 145 K the electrical conduction is mainly due to activation in the valence band and below this temperature due to variable‐range‐hopping of Efros–Shklovskii type in the impurity band. Our XRD and Raman data show the presence of SnSe and SnSe2 binary secondary phases in this compound. From the absorption coefficient data at room temperature the fundamental absorption edge is determined to be direct with a band gap energy of EG = (0.41 ± 0.01) eV. An additional indirect band‐to‐band transition above 0.9 eV, probably related to the band gap of SnSe, is observed.

Raman spectra of CuGa3Te5 that has a chalcopyrite‐related structure with space group Ptrue4¯2c were obtained at room temperature from measurements performed under parallel (z|xx|z) and perpendicular (z|xy|z) polarization dependent configurations. A tentative assignment of the observed lines was made by comparison with the reported phonon modes for ZnTe, which is the binary analogue of CuGaTe2, and also by using theoretical models reported in the literature for multinary compounds. The main lines observed at 129, 144, and 187 cm−1 were assigned to the three A1‐symmetry modes for Ptrue4¯2c ternary compounds predicted by group theory, and other lines at 91 and 277–285 cm−1 to the B1 modes. Also, lines at 55, 64, 102, 172, 224, 265–269, and 333–334 cm−1 and lines at 78, 172, 224, 205–209, 242–249, and 342 cm−1 were assigned to E and B2 modes, respectively. The higher‐phonon frequencies observed at 291–297, 303–310, and 319–323 cm−1 are attributed to an overtone of the A1 mode at 144 cm−1, and a combination of A1 and E modes, respectively.