Preparation and Thermoelectric Properties of Co-Doped ZnO Synthesized by Sol-Gel

Zinc oxide (ZnO) has attracted increasing attention as one of the most promising n-type thermoelectric materials, but its practice use was limited by high thermal conductivity and low electrical conductivity. Therefore, we herein prepared Co-doped ZnO nanoparticles by sol gel method and then compressed nanoparticles into bulk materials through spark plasma sintering. The thermoelectric properties, including electrical conductivity, Seebeck coefficient, thermal conductivity, and ZT value, have been investigated. We found that the substitution of Co2+ causes the decrease of bandgap and the increase of carrier concentration, thus the improvement of electrical conductivity. At the same time, the Co-induced lattice distortion and nanoparticles reduce the thermal conductivity by shortening the mean free path (MFP) of the phonons. The resultant ZT is 0.037 for Zn0.9Co0.1O, which is more than 23-fold higher than that of the pure ZnO samples.