Effect of Synthesis Factors on Microstructure and Thermoelectric Properties of FeTe2 Prepared by Solid-State Reaction

The alloying compound FeTe2 is a semi-metallic material with low thermal conductivity and has the potential to become a thermoelectric material. Single-phase FeTe2 compounds are synthesized using a two-step sintering method, and the effects of the optimal sintering temperature, holding temperature, and holding time on the thermoelectric properties of the alloy compound FeTe2 are investigated. The phase composition, microstructure, and electrical transport properties of the FeTe2 compound are systematically analyzed. The results show that single-phase FeTe2 compounds can be synthesized within the range of a sintering temperature of 823 K and holding time of 10~60 min, and the thermoelectric properties gradually deteriorate with the prolongation of the holding time. Microstructural analysis reveals that the sample of the alloy compound FeTe2 exhibits a three-dimensional network structure with numerous fine pores, which can impede thermal conduction and thus reduce the overall thermal conductivity of the material. When the sintering temperature is 823 K and the holding time is 30 min, the sample achieves the minimum electrical resistivity of 6.9 mΩ·cm. The maximum Seebeck coefficient of 65.48 μV/K is obtained when the sample is held at 823 K for 10 min; and under this condition, the maximum power factor of 59.54 μW/(m·K2) is achieved. In the whole test temperature range of 323~573 K, when the test temperature of the sample is 375 K, the minimum thermal conductivity is 1.46 W/(m·K), and the maximum ZT is 1.57 × 10−2.