Block-Layer Concept for the Layered Cobalt Oxide: A Design for Thermoelectric Oxides

A thermoelectric material is a material which generates electricity from heat through the Seebeck effect, and pumps heat through the Peltier effect. The thermo-electric conversion efficiency is characterized by the figure of merit Z= S 2/ρκ. (S, ρ, and κ are thermopower, resistivity, and thermal conductivity.) In order to attain the high thermoelectric efficiency, thermoelectric materials need large thermopower, low resistivity and low thermal conductivity. In conventional thermoelectric materials, however, S, ρ, and κcannot be controlled independently, because they depend on the carrier density. The thermoelectric performance is optimized near a carrier density of 1019cm-3, which is a typical value for a degenerate semiconduc-tor. Actually, the thermoelectric materials were mainly searched in the degenerate semiconductors of high mobility.