Effect of TiO2 on high-temperature thermoelectric properties of ZnO

The as-sintered Zn1−xTixO (0.01 ≤ x ≤ 0.05) samples contained a solid solution of Zn1−xTixO with a wurtzite structure and a small amount of the cubic spinel Zn2TiO4. The amount of Zn2TiO4 increased with an increase in TiO2 content. The density and grain size increased with the small TiO2 content (≤0.01), and then they decreased gradually by further increasing the TiO2 content. The addition of TiO2 to ZnO led to a significant increase in the electrical conductivity and a decrease in the absolute value of the Seebeck coefficient, resulting in an increase in the power factor. The highest value of power factor (7.6 × 10−4 W m−1 K−2) was attained for Zn0.98Ti0.02O at 1073 K. It is demonstrated that the TiO2 addition is fairly effective for enhancing thermoelectric properties.