The grain size and the density of the Zn-1 (-) xSnxO (0 <= x <= 0.05) samples decreased with increasing SnO2 content. The addition of a small amount of SnO2 (x <= 0.01) to ZnO led to an increase in both the electrical conductivity and the absolute value of the Seebeck coefficient, resulting in a significant increase in the power factor. The thermoelectric power factor was maximized to a value of 1.25 x 10(-3) Wm(-1) K-2 at 1073 K for the Zn0.99Sn0.01O sample. (c) 2007 Elsevier Ltd. All rights reserved.