Role of Al Substitution in the Enhancement of High-Temperature Thermoelectric Properties of ZnO Compound

ZnO thermoelectric material has shown a high Seebeck coefficient and low thermal conductivity. Nevertheless, the dimensionless figure of merit (ZT) value is quite low because of its high resistivity. We proposed a way to reduce electrical resistivity by substituting Al into ZnO. The Al-substituted ZnO samples were synthesized by solid-state reaction method and pressed into pellets by hot-pressing (HP) method. The Seebeck coefficient, electrical resistivity, and thermal conductivity (κ) are investigated. We have found that the electrical resistivity and the thermal conductivity significantly decreased with increasing Al content into the increases ZT = 0.28 (Al = 0.02) at 1073 K. The ZT values were higher than four times when compared with the unsubstituted sample.