Thermoelectric materials in layered transition-metal oxides

The layered cobalt oxides having the CdI2-type hexagonal CoO/sub 2/ layer exhibit good thermoelectric properties especially at high temperatures. The layered structure works quite well in this system. However, such fortunate situations rarely occur in the layered 3d transition-metal oxides, where the carrier is strongly coupled with phonons to form a polaron. In contrast, in the layered 4d transition-metal oxides we did not find any trance of polaron conduction. In this article, we will make a brief review of the thermoelectric properties of various layered transition-metal oxides.