Enhancement of Thermoelectric Performance of Donor-Doped ZnO Ceramics by Involving an In Situ Aluminothermic Reaction during Processing

This work explores the possibility of involving aluminothermy in processing donor-doped zinc oxide-based thermoelectrics by relying on local, strong exothermic effects developed during sintering, with a potential positive impact on the electrical and thermal transport properties. The strategy was exemplified by using aluminium as a dopant, due to its recognized ability to generate additional, available charge carriers in ZnO, and by using two different metallic Al powders and conventional Al2O3 as precursors. Nanosized aluminium powder was involved in order to evaluate the possible desirable effects of the particles size, as compared to aluminium micropowder. A significant enhancement of the electrical and thermoelectric performance of the samples prepared via metallic Al precursors was observed and discussed in terms of the potential impacts provided by the aluminothermic reaction on the microstructure, charge carrier concentration and mobility during sintering. Although the presented results are the first to show evidence of how aluminothermic reactions can be used for boosting the thermoelectric performance of zinc oxide materials, the detailed mechanisms behind the observed enhancements are yet to be understood.