Direction-Dependent Thermoelectric Properties of a Layered Compound In<inf>2</inf>Te<inf>5</inf> Single Crystal

We examine the anisotropic electrical and thermal transport properties in single crystals of In2Te5 belonging to the monoclinic space group C12/c1 with the temperature gradient applied parallel (||) and perpendicular (⊥) to the crystallographic c-axis of the crystals. A systematic investigation of structural, electrical, and thermal properties suggests the role of layered structure in this material in guiding its thermoelectric behavior. The thermal conductivity along the c-axis (κ||c) was found to be smaller by a factor of 2 compared to the thermal conductivity along the direction perpendicular to the c-axis (κ⊥c) over the entire temperature range. In contrast, the Seebeck coefficient along the c-axis (S||c) was found to be higher than its value along the direction perpendicular to the c-axis (S⊥c). At room temperature, the figure of merit zT||c is found to be four times larger as compared to the figure of merit zT⊥c. Our results provide insights into how the resistivity, thermal conductivity, and thermopower depends on the crystalline anisotropy and its impact on the overall zT.