A Comparison Between the Mechanical and Thermoelectric Properties of Three Highly Efficient p-Type GeTe-Rich Compositions: TAGS-80, TAGS-85, and 3% Bi₂Te₃-Doped Ge_0.87Pb_0.13Te

Abstract

Since the 1960s, the TAGS system, namely (GeTe) _x (AgSbTe₂)_1−x , with two specific compositions x = 0.8 and 0.85, known as TAGS-80 and TAGS-85, respectively, was identified as containing highly efficient p-type thermoelectric materials. Recently, another highly efficient p-type GeTe-rich composition, namely 3% Bi₂Te₃-doped Ge_0.87Pb_0.13Te, achieving thermoelectric properties comparable to TAGS-based solid solutions, was also reported. Since all of these compositions were obtained by different manufacturing approaches, a comparison between the transport and mechanical properties of these alloys, prepared by the same manufacturing techniques, is required to identify the advantages and disadvantages of these compositions for practical thermoelectric applications. In the current research, the thermoelectric and mechanical properties of three highly efficient GeTe-rich alloys, TAGS-80, TAGS-85, and 3% Bi₂Te₃-doped Ge_0.87Pb_0.13Te, following hot pressing, were investigated and compared. Maximal ZT values of ∼1.75, ∼1.4, and ∼1.6 at 500°C were found for these compositions, respectively. Improvement of the mechanical properties was observed by increasing the GeTe content. The influence of the GeTe relative amount on the transport and mechanical properties was interpreted by means of the phase-transition temperatures from the low-temperature rhombohedral to the high-temperature cubic phases.