Thermoelectric Transport Properties of Co<sub>0.5</sub>Fe<sub>0.5</sub>Se<sub>2</sub>, Co<sub>0.5</sub>Fe<sub>0.5</sub>Te<sub>2</sub>, and Their Solid-Solution Compositions

Abstract

Transition- metal chalcogenides with tunable electronic transport properties and unique crystal structures have attracted much attention as potential thermoelectric materials. In this study, the electrical, thermal, and thermoelectrical transport properties of Co0.5Fe0.5Se2, Co0.5Fe0.5Te2 and a series of solid-solution compositions ( Co0.5Fe0.5(Se1-yTey)(2), y = 0.25, (0.5), and 0.75) were investigated. Co0.5Fe0.5Se2 and Co0.5Fe0.5Te2 polycrystalline alloys exhibited high power factors of 1.37 and 1.53 mW/mK(2) at 600 K, respectively, and their solid-solution compositions exhibited lower power factors between 0.38 and 0.81 mW/mK(2). The lattice thermal conductivities of Co0.5Fe0.5Se2 and Co0.5Fe0.5Te2 were (2).87 and 1.71 W/mK at 300 K, respectively, and their solid-solution compositions exhibited lower lattice thermal conductivities between 0.96 and 1.98 W/ mK. Consequently, the thermoelectric figure of merit (zT) of the Co0.5Fe0.5Se2 and Co0.5Fe0.5Te2 polycrystalline alloys was 0.16 and 0.18 at 600 K, respectively, and the zT of their solid-solution composition exhibited lower values between 0.04 and 0.09. As the solid-solution composition exhibited a lower thermoelectric performance than the Co0.5Fe0.5Se2 and Co0.5Fe0.5Te2 polycrystalline alloys, the lower thermoelectric performance was analyzed and discussed. [GRAPHICS.]