Progress in increasing values of the figure of merit (ZT) for bulk thermoelectric materials was largely achieved through the suppression of thermal conductivity by employing lattice point defects, developing complex structures with loosely bound “rattle” atoms or groups, creating resonant dopant levels near the Fermi energy, or nanostructuring. Nevertheless, thin-film superlattices and quantum-dot thin-films still hold records for the highest ZT reported. Quantum-well structures in thin-film superlattices were shown theoretically and experimentally to lead to power factor enhancement through the quantum confinement effect.<br/>In our study we focused on creating bulk thermoelectric materials with the quantum confinement effect. Compounds with similar structures and crystal cell parameters but large difference in energy band gaps were utilized with primary focus on PbTe/CdTe and PbS/CdS systems. Large exciton Bohr radii in PbTe and PbS are crucial for achieving the quantum confinement effect.<br/>Several approaches were utilized to create nanostructures with controlled quantum-well thickness. In a simpler approach, nanocomposites were formed by mixing the pre-made nanoparticles of 2 materials followed by densification by the spark plasma sintering (SPS) method.<br/>Fine control of quantum-well material thickness was achieved by utilizing nano core-shell building blocks. A successive ionic layer adsorption and reaction (SILAR) method was employed as a facile way for large scale core-shell particle synthesis with well defined shell thickness. Nanostructures of the prepared materials as well as transport properties will be discussed. This work was supported by the National Science Foundation through Grant DMR-1206718.

Bulk nanostructured thermoelectric materials with quantum confinement

249th National Meeting (2015)

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