Phase, microstructural investigation and thermoelectric properties of Ga-doped zinc oxide-based ceramics sintered under an argon atmosphere

Compositions in the (Zn0.98-yAl0.02Gay)O (y = 0.00, 0.01, 0.02, 0.03) series were fabricated via the conventional solid-state sintering route under an argon atmosphere, and their phase, microstructure and thermoelectric properties were investigated. Single-phase ceramics were formed for the compositions with y ≤ 0.01. However, an unknown secondary phase was developed along with the parent phases when y ≥ 0.02 due to an over solubility limit of Ga in Zn. For a particular value of Ga substitution for Zn, the (Zn0.98Al0.02)O ceramics had decreased electrical resistivity (ρ) and an increased power factor (PF). In the present study, the highest power factor of 5.518 × 10−4 W K−2 m−1 and lowest electrical resistivity of ~0.82 mΩcm were obtained for the composition with y = 0.01, i.e., (Zn0.97Al0.02Ga0.01)O.