High-temperature charge transport and thermoelectric properties of a degenerately Al-doped ZnO nanocomposite

2 mol% Al-doped ZnO nanoparticles were consolidated into a ZnO nanocomposite with ZnAl2O4 nanoprecipitates by spark plasma sintering and its high-temperature charge transport and thermoelectric properties were investigated up to 1073 K. The carrier concentration in the nanocomposite was not dependent on the temperature, while the Hall mobility showed positive temperature-dependence due to grain boundary scattering. The negative Seebeck coefficient of the nanocomposite was linearly proportional to the temperature, and the density of the state effective mass (m(d)*) was evaluated to be 0.33m(e) by using the Pisarenko relation. Drastic reduction of thermal conductivity (k < 2 W m(-1) K-1) was achieved in the nanocomposite, and the maximum ZT of 0.34 was obtained at 1073 K.