Transport properties and thermoelectric performance of (Zn_1-yMg_y)_1-xAl_xO

Addition of MgO to Al-doped ZnO was successful in reduction of the phonon thermal conductivity, κ_ph, in order to suppress the unfavorably high thermal conductivity, κ, of the material in terms of applications to thermoelectric conversion. The electrical conductivity, σ, of Zn_0.98Al_0.02O decreased with increasing amount of the added MgO, whereas the Seebeck coefficient was virtually unchanged up to (Zn_0.9Mg_0.1)_0.98Al_0.02O. Further Al₂O₃ doping was ineffective in improving σ. The carrier mobility decreased with increasing amount of the added MgO but was independent of the extent of the Al doping. In spite of the significant suppression of κ, the figure of merit was smaller for the MgO-added samples because of the marked decrease of σ.