Thermoelectric Properties of Bi2.3-xPbxSr2.6Co2Oy Single Crystals

Abstract

A set of single crystals of the layered cobaltite Bi_2.3-x Pb_xSr_2.6Co₂O_y (0 ≤x≤0.44) were prepared by a flux technique. The resistivity ρ and the thermopower S along the in-plane direction were measured, and the thermoelectric properties were compared with those of other oxides. The Pb substitution causes a decrease in ρ and an increase in S below 100 K, which improves the power factor S ²/ρ by 3–4 times. The transport parameters exhibit an anomaly near 25–50 K, such as a plateau in S and an upturn in ρ, which we ascribe to the reduction of the density of states owing to a pseudogap.