Person:

Liang, Xin

Compositionally dependent superlattices, (In_2O_3) ((ZnO) _k), form in the (ZnO)-rich portion of the (ZnO-In_2O_3) phase diagram, decreasing thermal conductivity and altering both the electron conductivity and Seebeck coefficient over a wide range of composition and temperature. With increasing indium concentration, isolated point defects first form in (ZnO) and then superlattice structures with decreasing interface spacing evolve. By fitting the temperature and indium concentration dependence of the thermal conductivity to the Klemens-Callaway model, incorporating interface scattering and accounting for conductivity anisotropy, the Kapitza resistance due to the superlattice interfaces is found to be (5.0 ± 0.6 × 10^{−10} m^2K/W). This finding suggests that selecting oxides with a compositionally dependent superlattice structure can be a viable approach, unaffected by grain growth, to maintaining low thermal conductivity at high temperatures.

The present dissertation investigates the relationship between the structure and thermoelectric properties of ZnO based materials, with a focus on trivalent element doping on engineering the microstructure and altering the electrical and thermal transport properties. Within the solubility range, the addition of trivalent elements, such as In3+, Fe3+ and Ga3+, is observed to increase the electrical conductivity of ZnO and decrease the thermal conductivity.