Effect of Synthesis Factors on Microstructure and Thermoelectric Properties of FeTe[sub.2] Prepared by Solid-State Reaction

The alloying compound FeTe[sub.2] is a semi-metallic material with low thermal conductivity and has the potential to become a thermoelectric material. Single-phase FeTe[sub.2] 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 FeTe[sub.2] are investigated. The phase composition, microstructure, and electrical transport properties of the FeTe[sub.2] compound are systematically analyzed. The results show that single-phase FeTe[sub.2] 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 FeTe[sub.2] 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·K[sup.2]) 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[sup.−2].