Effects of Ge Doping on the Charge Transport and Thermoelectric Properties of Permingeatites Cu3Sb1−yGeySe4

Permingeatites Cu3Sb1−yGeySe4 (0 ≤ y 0.14) were synthesized by mechanical alloying and hot pressing. The charge-transport parameters (Hall coefficient, carrier concentration, mobility, Lorenz number) thermoelectric properties (electrical conductivity, Seebeck power factor, thermal figure of merit) examined with respect to the Ge doping level. A single permingeatite phase a tetragonal structure was obtained without subsequent heat treatment, but small amount secondary Cu2GeSe3 found for specimens ≥ 0.08. All hot-pressed compacts exhibited relative density 97.5%–98.3%. lattice constants a-axis c-axis decreased substitution at Sb sites. As content increased, concentration increased from 5.2 × 10<sup>18</sup> 1.1 10<sup>20</sup> cm<sup>−3</sup>, mobility 92 25 cm<sup>2</sup>·V<sup>−1</sup>·s<sup>−1</sup>. number undoped Cu3SbSe4 implied non-degenerate semiconductor behavior, ranging (1.57–1.56) 10<sup>−8</sup> V<sup>2</sup>·K<sup>−2</sup> 323–623 K. merit 0.39 623 K, resulting factor 0.49 mW·m<sup>−1</sup>·K<sup>−2</sup> conductivity 0.76 W·m<sup>−1</sup>·K<sup>−1</sup>. However, numbers Gedoped indicated degenerate characteristics, increasing (1.63–1.94) highest 0.65 K Cu3Sb0.86Ge0.14Se4, significantly improved 0.93 0.89W·m<sup>−1</sup>·K<sup>−1</sup>. result, remarkably enhanced into sites permingeatite.