First-principles studies on the phase stability of thermoelectric materials.
Computational determination of transport properties affecting thermoelectric figure of merit.
Studying elemental solubilities for promising doping atoms in thermoelectric materials.
Determining the solubility of n- and p- type doping elements is an important aspect of materials development in order to optimize the carrier concentration of heavily doped thermoelectric materials, thus leading to large gains in their thermoelectric figure of merit. Another common path for efficiency improvements is decreasing lattice thermal conductivity. This is typically done by the inclusion of nanoscale precipitates which contribute to phonon scattering. It is further hypothesized that coherent interfaces give larger improvements than incoherent interfaces. Therefore, optimization of carrier concentration and determination of the ordering tendencies of thermoelectric materials could lead to efficiency improvements.
In many thermoelectric material systems, the incoherent vs. coherent ordering tendencies and interfacial properties remain largely unknown and are important to enable tailored nanostructure morphology. For (II,IV)-VI thermoelectric alloys, these ordering tendencies reveal markedly different results from those expected based on intermetallic alloy ordering and (IV,IV)-VI alloys. While large coherency strain alters the thermodynamics of phase stability, these low lattice mismatch systems exhibit different short range ordering tendencies, one of phase mixing along one crystal direction and phase separation along another. This could lead to unique nanoprecipitate shapes with varying interfacial character along different directions leading to a future area of exploration examining the connection between ordering tendency and precipitate shape with the cluster variation method.
Parallel to this effort is a study of elemental solubilities for promising doping atoms in thermoelectric materials.
Jonathan graduated summa cum laude from Purdue University in May 2013 with a B.S degree with honors in Chemical Engineering. He also completed chemistry, mathematics, and french minors. While there, he completed an honors thesis under the guidance of Yue Wu working on size-directed, hot injection synthesis of PbTe nanocrystals.
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