|About this Abstract
||2021 TMS Annual Meeting & Exhibition
||Alloys and Compounds for Thermoelectric and Solar Cell Applications IX
||Phase Boundary Mapping to Improve Na solubility, Band Convergence, and Thermoelectric Properties in p-type PbTe
||James Patrick Male, Priyanka Jood, Shashwat Anand, G. Jeffrey Snyder
|On-Site Speaker (Planned)
||James Patrick Male
Many monumental breakthroughs in p-type PbTe thermoelectrics are driven by optimizing a Pb0.98Na0.02Te matrix. We find high temperature zT near 2 for Pb0.96Na0.04Te, despite doping beyond the expected solubility limit of Na. High temperature X-ray diffraction and carrier concentration measurements show enhanced Na solubility at high temperatures when x > 0.02, but no improvement in carrier concentration, indicating that Na enters the lattice but is electrically compensated by intrinsic defects. Experiments and calculations show that higher Na concentration converges the light L and heavy Σ valence bands in PbTe, suppressing bipolar conduction and increasing the Seebeck coefficient. Further, we apply a phase diagram approach to explain the origins of increased solubility from excess Na doping and offer strategies for repeatable synthesis of high zT Na-doped materials. A starting matrix of simple, high performing Pb0.96Na0.04Te synthesized following our guidelines may be superior to Pb0.98Na0.02Te for continued PbTe optimization.