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A6: Characterization

High Temperature Neutron Diffraction Study of Nanostructured Pb-Te-Sn-S Thermoelectric Materials

Fei Ren 1, Robert D. Schimidt 2, Eldon D. Case 2, Ke An 3
1 Mechanical Engineering, Temple University 2 Chem. Eng. and Materials Science, Michigan State University, 3 Chemical and Engineering Materials Division, Spallation Neutron Source, Oak Ridg National Laboratory

Energy harvesting applications of thermoelectrics (TE) require these materials to be stable within the service temperature range as well as during thermal cycling. Recent development of nanostructured TE materials has led to improvements in TE properties such as the figure of merit, ZT. However, thermal stabilities of these nanostructures have received less attention and need further investigation. In this study, we used in situ neutron diffraction technique to examine the structural evolution of PbSnTe-PbS between room temperature and 900 K. Three types of samples were included: powder, hot pressed, and pulsed electrical current sintered. It was discovered that the nanostructure in these materials was cubic PbSnS2 rather than previously reported PbS which and was stable up to ~ 700 K. In addition, for the powder sample, significant reduction in peak broadening was observed during the first heating cycle, which could be attributed to decrease in dislocation density during annealing.