Enhanced thermoelectric performance of yttrium-doped ZnO ceramics <i>via</i> secondary phase formation and conventional sintering

Zinc oxide (ZnO)-based ceramics have been widely studied for thermoelectric applications due to their abundance, non-toxicity, cost-effectiveness, thermal stability, and high Seebeck coefficient. In this work, a series of yttrium (Y)-doped ZnO samples was synthesized using the sol-gel method followed by conventional sintering. The thermoelectric property measurements coupled with detailed structural characterization were systematically performed to establish a structure-property relationship. The X-ray diffraction (XRD) analysis confirms limited substitution of Y at the Zn-site in the lattice of ZnO. The surplus Y-doping results in the formation of the secondary phase Y₂O₃. The sample with composition Zn_0.98Y_0.02O exhibited the highest power factor and figure of merit (<i>ZT</i>) values of 0.47 μW cm^-1 K^-2 and 5.6 × 10^-5, respectively, at 575 K. The outlined study elucidates the effects of Y-doping in ZnO to understand the underlying transport phenomenon in ZnO ceramics.