Power generation of a p-type Ca3Co4O9/n-type CaMnO3 module

Thermoelectric modules composed of eight pairs of p-type Ca2.7Bi0.3Co4O9 (Co-349) and n-type CaMn0.98Mo0.02O3 (Mn-113) bulks were constructed using Ag electrodes and paste including powder of the n-type oxide. The former bulks were prepared by hot pressing. On the other hand, the latter were densified using a cold isostatic pressing technique and sintered in atmospheric pressure. Dimensions of both oxide legs were 5 mm wide and thick and 4.5 mm high. An alumina plate was used as a substrate, and there was no alumina plate on the other side of the modules. When the substrate side was heated, the module could generate up to 1.0 V and 0.17 W of open circuit voltage (V-O) and maximum power (P-max), respectively, at a hot-side temperature of 1273 K (furnace temperature as a heat source) and a cold-side temperature of 298 K (circulated water temperature) in air. But internal resistance R-I reached a value of 1.5 Omega, which is about six times higher than the calculated one from resistivity of both p- and n-type bulks. When the substrate side was cooled, V-O and P-max reached 0.7 V and 0.34 W of V-O and P-max, respectively, at a furnace temperature of 1273 K.