Electronic transport and thermoelectricity in the selenospinel Cu6-xFe4+xSn12Se32

We report a study of selenospinel Cu6-xFe4+xSn12Se32 (x = 0, 1, 2) single crystals, which crystallize in a cubic structure with the Fd3m space group, and show typical semiconducting behavior. The large discrepancy between the activation energy for electrical conductivity Ep (32.3-69.8 meV), and for thermopower ES (3.2-11.5 meV), indicates a polaronic transport mechanism between 350 and 50 K. With decreasing temperature, it evolves into variable-range hopping conduction. Furthermore, the heat capacity shows a hump around 25(5) K and diverges from the Debye T3 law at low temperatures, indicating the observation of structural glassy features in these crystalline solids.

Automated summary

We report a study on the single crystals of selenospinel Cu6-xFe4+xSn12Se32 (x = 0, 1, 2), which have a cubic structure with the Fd3m space group and exhibit typical semiconductor behavior. The large difference between the activation energy for electrical conductivity Ep (32.3-69.8 meV) and for thermopower ES (3.2-11.5 meV) indicates the presence of a polaronic transport mechanism between 350 and 50 K. As the temperature decreases, it evolves into variable-range hopping conduction. Furthermore, the heat capacity shows a hump around 25(5) K and deviates from the Debye T3 law at low temperatures, suggesting the observation of structural glassy features in these crystalline solids.