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 , CoO, and to ZnO. It was found that the interstitial in the ZnO restrains the grain growth and CoO acts onto the bond between grains. The influence of the inclusion of and CoO onto the sintering behavior also was investigated.

The influence of the internal current for the ZnO ceramics on the sintering behavior by pulse current sintering (PCS) method was investigated. To clear the dependence of inner current on the sintering behavior of ZnO ceramics, direct measurement of electric resistance of ZnO specimen under sintering by SPS device was carried out. It was observed that electric resistance of specimen decreases with increase in the temperature. The electric resistance begins to decrease from the low temperature of . The internal structure of sintered ZnO ceramics changed by the control of the internal current in the specimen using plate.