Microstructure and Sintering Behavior of ZnO Thermoelectric Materials Prepared by the Pulse-Current-Sintering Method

Thermoelectric conversion efficiency of thermoelectric elements can be increased by using a structure combining n-type and p-type semiconductors. From the above point of view, attention was directed at ZnO as a candidate n-type semiconductor material and investigations were made. As the result, a dimensionless figure of merit ZT close to 0.28 (1073K) was obtained for specimens produced by the PCS (Pulse Current Sintering) method with addition of specified quantities of $TiO_2$, CoO, and $Al_2O_3$ to ZnO. It was found that the interstitial $TiO_2$ in the ZnO restrains the grain growth and CoO acts onto the bond between grains. The influence of the inclusion of $TiO_2$ and CoO onto the sintering behavior also was investigated.