Anisotropy of Young's Modulus and Microhardness of PbTe

Abstract

Nanoindentation measurements were performed for a single PbTe crystal grown by self-selecting vapour growth method and characterized by X-ray diffraction. The microhardness and Young's modulus were determined for a few loads applied along the [001], [011] and [111] high symmetry directions for carefully oriented, 2 mm thick crystal plates. An anisotropy of two parameters has been suggested and compared with available literature data. The present results qualitatively confirm the theoretical predictions for a rock salt type crystal (PbS). The microhardness anisotropy value is in an agreement with recently determined, relevant value for (Pb,Cd)Te solid solution.

Anisotropy of Selected Mechanical Properties of PbTe

“…Taking into account that the maximum nanoindentation depth for the lowest applied maximum load is of the order of 100 nm or even slightly smaller the quantitative value of nanohardness anisotropy determined for relatively small maximum loads should be considered with some caution. A significant dependence of H on applied load maximum was not observed, present data corresponding, for example, to 10 mN does not differ a lot from values determined previously for much lower maximum load . The obtained nanohardness anisotropy determined for bulk PbTe crystals can be compared with those, previously determined for bulk (Pb,Cd)Te solid solution crystals, containing 5% of CdTe .…”

“…A slightly higher value 58.86 GPa corresponded to hot extruded samples . Some noticeably higher values (from about 65 GPa to 70 GPa) were recently reported for single crystal PbTe grown by SSVG method …”

“…The anisotropy of both microhardness and Young's modulus determined for (Pb,Cd)Te solid solution using a single crystal containing about 5% of CdTe does not exceed 10% . Very recently, the nanohardness and Young's modulus anisotropy for PbTe, suggested by results of nanoindentation measurements qualitatively confirmed values corresponding to (Pb,Cd)Te . However, because of a very low maximum load applied for these measurements and resulting from it low maximum nanoindentation depth these results should be considered cautiously (see the further discussion in Part 4) and require confirmation using higher values of maximum load.…”

“…These values are relatively low in comparison to reported microhardness for Si, GaAs, other semiconducting compounds of III–V type, or even for selected II–VI type materials. Recently, the nanohardness values from about 550 MPa to about 590 MPa were reported for single crystal PbTe grown by the self‐selecting vapor growth (SSVG) method …”

XVII Interstate Conference Thermoelectrics and Their Applications --- 2021" (ISCTA 2021 St. Petersburg, September 13-16, 2021 Obtaining and investigation of ohmic contacts with high adhesion to thermoelements

“…The purpose of this operation is to remove the layer of TE materials damaged during cutting of the samples and to obtain the necessary surface roughness, which plays an important role in the adhesion strength of the deposited film. Mechanical treatment of TE materials is not an easy task, since the majority of thermoelectric materials are soft, with a microhardness of 25 to 70 kg/mm 2 [21,[33][34][35][36][37][38][39][40]. This greatly complicates the grinding and polishing of TE materials.…”