High thermoelectric figure of merit of aluminum doped zinc oxide through unintentional graphite inclusion

Abstract

Serendipity plays a major role in scientific progress. Often unintentionally, things lead to consequences which pave road for further developments. Here, we report high thermoelectric figure of merit of a gram-scale synthesized, compositionally graded nanocomposite made by unintentional graphite inclusion in nanocrystalline 2%Al doped ZnO (AZO) hot pressed sample. This facile inclusion has led to significantly high thermoelectric figure of merit of this Al doped zinc oxide system. The hybrid compositionally graded samples obtained using hot uniaxial pressing contained nanosized AZO particles with graphitic carbon inclusions together having density of 4.3 gm/cc i.e. 80% of theoretical density of ZnO. Al has been found to substitute at Zn site in the ZnO lattice as seen from XRD. This led to a giant electrical conductivity of about 600 S/cm. Moreover, the thermopower values are about 50 µV/k which is rather low for pure oxides. Nonetheless, it also showed significantly low thermal conductivity (< 7 W /m.K). Together, all these parameters could give the figure of merit as 0.09 at 1000 K, which is at least two orders of magnitude higher than the values expected of polycrystalline zinc oxides reported in the literature.In the original version of the article supplied to AIP Publishing, the name of Keshav Dabral was misspelled. Additionally, figure 4 did not appear clearly. An updated article, with these issues corrected, was published on 21 January 2021.