Microstructure and thermoelectric performance evaluation of p-type (Bi, Sb)2Te3 materials synthesized using mechanical alloying and spark plasma sintering process

In this paper, three p-type thermoelectric compounds, namely Bi0.5Sb1.5Te3, Bi0.3Sb1.7Te3, and Bi0.2Sb1.8Te3 were manufactured by mechanical milling and spark plasma sintering method. The effects of chemical composition on microstructural and thermoelectric properties were investigated. In this order, Bi, Te, and Sb powders with different contents were mechanically milled for 6 hours. Then, they were consolidated using a spark plasma sintering process (SPS) at 400 degrees C under 60 MPa pressure. The phase composition was analyzed using XRD with Cu-K alpha radiation. The microstructural characterization of the specimens was performed using scanning electron microscopy. Moreover, thermoelectric properties of the samples, including the Seebeck coefficient, electrical and thermal conductivity, power factor, and ZT were determined. Analysis of XRD patterns of fabricated compositions indicated that a single phase with a rhombohedral lattice structure was synthesized in all conditions. In addition, SEM results showed an integrated structure with a few scattered micropores. The thermoelectric results confirmed that Bi0.5Sb1.5Te3 demonstrates the lowest thermal conductivity (0.85 W/m K), the highest electrical conductivity (4.48 S/cm), and the maximum figure of merit (1.03 x 10(-2)) at room temperature. Therefore, it is the best option among the fabricated compounds to be utilized as thermoelectric materials.