Mechanical properties of low-cost, earth-abundant chalcogenide thermoelectric materials, PbSe and PbS, with additions of 0–4 % CdS or ZnS

Abstract

PbTe-based thermoelectric (TE) materials have been extensively investigated as TE generator materials, however, the tellurium content limits the application potential due to both availability and cost. Replacing the tellurium with selenium or sulfur produces an isomorphic TE material with very good reported figure of merit, ZT, values of 1.3-1.6, but the effect of the material changes designed to increase ZT (doping, nano-and micro-precipitate additions) on mechanical properties has not been reported. In order to effectively incorporate these new materials into TE devices, it is important to understand materials' response to thermally and mechanically imposed loads, which in turn requires knowledge of the mechanical properties. In this study, the hardness was determined by Vickers indentation and elastic modulus and Poisson's ratio were measured using resonant ultrasound spectroscopy on PbSe-and PbS-based TE specimens as a function the addition of 0-4 at.% of CdS or ZnS. With 2.0 or 2.5 at.% Na doping, the hardness of PbSe-or PbS-based TE materials increased by about 30 % and the elastic moduli decreased by 5-10 %. In addition, PbS may be effectively sintered at 723 K when doped with 2.5 at.% Na, but requires a higher sintering temperature when undoped. This study shows that the hardness and moduli of PbSe-or PbSbased TE materials are not strong functions of the addition of CdS or ZnS precipitates.

Mechanical Properties of Thermoelectric Materials for Practical Applications

“…Enhancing the material strength can be achieved by engineering the material microstructure in the micron and submicron scales. Furthermore, experiments were also made trying to incorporate nano-particles or wires for producing composite materials [13,29]. The latter fabrication approach usually results in lower ZT of the materials with enhanced mechanical properties, which are associated with the strengthening components, without any significant contribution to the TE performance.…”

Tailoring the mechanical properties of thermoelectric lead telluride by alloying with non-doping calcium

“…Being highly doped semiconductors, thermoelectric materials are often very brittle and may show low fracture strengths. As a consequence, there have been some attempts in recent years to improve these mechanical properties in different classes of thermoelectric materials [7][8][9][10].…”

Microhardness and the Young Modulus of Thin, MBE-Grown, (Sn,Mn)Te Layers Containing up to 8% of Mn

“…For example using the same experimental setup the determined Young modulus was also a constant value in (Pb,Cd)Te solid solution but the microhardness increased by almost 50% in a similar composition range [17]. The microhardness of (Pb,Zn)Se and (Pb,Cd)Se solid solutions containing up to a few percent of Zn and Cd, respectively, also significantly increases with an increasing dopant metal content [20]. In the case of (Pb,Ge)Te bulk crystals both the microhardness and the Young modulus values were significantly higher for the solid solution containing 10% of Ge than those for PbTe [18].…”