Thermoelectric transport properties of naturally nanostructured Ga-ZnO ceramics: Effect of point defect and interfaces

Point defects and nanoscale interfaces have been found of significant influence on the phonon and electrical transport properties. In the preset work, we present the high temperature thermoelectric properties of naturally nanostructured Ga-ZnO ceramics synthesized by sparking plasma sintering process. By varying the GaO1.5 doping concentration, compositionally dependent structures were formed, from point defected solid solution to nanostructures with superlattices and nanotwins. The introduction of low GaO1.5 concentration increases both electron and point defect concentrations, leading to significantly increased electrical conductivity while reduced thermal conductivity. The nanostructure interfaces are found to increase scattering of both charge carriers and phonons, leading to drastically reduced electronic mobility and lattice thermal conductivity. A combined analysis of electrical conductivity and Seebeck coefficient with temperature was also developed, which revealed that the dominant electron scattering mechanism changes with defect concentration. We believe that this approach is also likely applicable to other thermoelectric material systems.