MSc Candidate Ms. Aleksandra Uzhansky
Room 302, Meidan, and via ZOOM
Thermoelectric (TE) materials serve for conversion of waste heat into electricity. Reasonable TE conversion efficiency requires high electrical conductivity and Seebeck coefficient together with low thermal conductivity. These requirements can be fulfilled by introduction of second-phase precipitates. Lead telluride is a prominent TE material capable of formation of Ag-rich precipitates upon alloying with Ag. Precipitate formation and evolution at elevated temperatures are determined by their interfacial free energy, which mainly depends on their orientation relationship (OR) with respect to the matrix. In this study we simulate experimentally observed ORs between Ag2Te precipitates and PbTe matrix from first-principles at 0 K. Our calculations reveal higher interfacial energies for Ag terminations than for mixed ones. We obtained values ranging between 150 and 800 mJ/m2 for the monoclinic Ag2Te phase, whereas for the cubic phase they range between 80 and 500 mJ/m2. Higher interface free energies increase the energy barrier for nucleation, thereby suppressing the nucleation rate. To evaluate the effects of Bi-doping on the precipitate growth kinetics, we calculated the substitution formation energies (SFE) of Bi at the vicinity of the interfaces, and found that Bi substitution for Pb reduces the interface energy. Interestingly, Bi was also found to reduce the activation energy for diffusion of Ag in PbTe from 52.9 down to 44.1 kJ/mol. This study elucidates the effects of interface energy on precipitation kinetics in PbTe-based compounds with implications for TE performance.
Supervisor: Prof. Yaron Amouyal
The lecture will take place in room 302, Meidan, for green pass holders, or via ZOOM.
Meeting ID: 995 9239 6977