Effect of hot isostatic pressing treatment on the thermoelectric power factors of zinc oxides

The effect of hot isostatic pressing (HIP) on the thermoelectric power factor of zinc oxide (ZnO) has been examined. ZnO is expected to be a potential n-type oxide thermoelectric material that could enhance the thermoelectric conversion efficiency. The HIP treatment is useful for densifying the material and controlling crystal defects in the material by applying high temperatures and pressures simultaneously. Furthermore, the atmosphere during HIP treatment can be controlled to enable the application of this technique to both metallic and oxide materials. The thermoelectric power factor of ZnO increased due to a notable increase in electrical conductivity, although the Seebeck coefficient decreased by approximately 50% following HIP treatment under argon gas. The increase in the thermoelectric power factor is attributed to the oxygen vacancies introduced into ZnO subsequent to the HIP treatment. Consequently, HIP treatment represents a promising approach for enhancing the thermoelectric power factor of ZnO.