Dresden 2017 – wissenschaftliches Programm
CPP 39.9: Vortrag
Mittwoch, 22. März 2017, 17:15–17:30, POT 81
Ag-segregation at dislocations and grain boundaries in annealed PbTe thermoelectric materials studied by atom probe tomography — •Yuan Yu1, Oana Cojocaru-Mirédin1, Yaron Amouyal2, Ariel Sheskin2, and Matthias Wuttig1 — 1I. Physikalisches Institut (IA), RWTH Aachen, 52074, Aachen, Germany — 2Technion-Israel Institute of Technology, 32000 Haifa, Israel
PbTe-based alloys play a significant role in thermoelectric (TE) applications. The figure-of-merit, ZT, of standard PbTe is near 1, whereas for PbTe alloys doped with Sr, Na, K, and Ag, the ZT factors are larger than 2. The large enhancement of ZT values mainly benefits from the elemental doping-induced band modification and nano-precipitation. However, the effects of these dopants on the TE properties is still not well understood mainly due to the difficulty to track the impurity redistribution in 3D with traditional characterization techniques. Here, we investigated the distribution of Ag in PbTe TE material using 3D atom probe tomography. We clearly find that the Ag is prone to form platelet-like nanostructures with diameters of ~15 nm and thickness of ~3 nm in the as-quenched state. After annealing at 380 °C for 48 h, these platelet-like nanostructures dissolve in the matrix, leading to a Ag-supersaturated matrix. Thus, the Ag tends to segregate at the dislocations and grain boundaries. These Ag-decorated dislocations and grain boundaries as well as the remaining stable Ag-rich nano-precipitates are believed to influence the electron and phonon transport processes. Our results can help to better tailor the structures and provide more information for the theoretical calculation.