Thermoelectric properties of Zn1-xAlxO ceramics prepared by the polymerized complex method

Zn1-xAlO powders were synthesized by the polymerized complex method and then consolidated by a SPS (Spark Plasma Sintering) apparatus. The microscopic structure and thermoelectric properties were examined comparing with the results of the samples prepared by the conventional solid-state reaction method. A small amount of ZnAl2O4 spinel phase as the second phase was observed in the sintered samples with x>0.02 by x-ray diffraction and SEM (Scanning Electron Microscope). The grain size of the samples prepared by the polymerized complex method is much smaller than that of the samples prepared by the solid-state reaction method. The absolute value of the Seebeck coefficient, electrical resistivity and thermal conductivity for the samples prepared by the polymerized complex method decrease with increasing x up to about x=0.01, and at fixed Al content of x, they are smaller than those for the samples prepared by the solid-state reaction method. The solubility limit of Al in Zn1-xAlxO system is about x=0.01. The doping of the carrier into the material can be more easily realized in the samples prepared by the polymerized complex method. Zn0.9975Al0.0025O has a maximum value of figure of merit of 6.9 X 10(-5) K-1 at 1073K.