Thermoelectric Properties of Zinc Oxide Doped with Aluminum and Nickel Ions

In this work, a thermoelectric material with the nominal composition Zn 0.97 Al 0.02 Ni 0.01 O is synthesized using the chemical coprecipitation method. The synthesized powder consists of the main phase of wurtzite with a small content of Ni 1– z Zn z O; the change in the crystal-lattice parameters of the main phase indicates the replacement of Zn 2+ with Al 3+ . The Ni 1– z Zn z O phase is predominantly located at the grain boundaries, blocking their growth during spark-plasma sintering. The resulting morphology enhances phonon scattering processes, which leads to a decrease in thermal conductivity. The electrical conductivity exhibits activation behavior and increases significantly in comparison with undoped ZnO, because the concentration of charge carriers increases with the substitution of Zn 2+ /Al 3+ . Thus, the chemical coprecipitation method allows one to obtain doped ZnO with an increase in thermoelectric performance of more than 2 times relative to undoped ZnO.