The Effects of the Misfit Structure on Thermoelectric Properties of Bi2-xPbxSr2Co2Oy Single Crystals

In-plane anisotropy of the resistivity and thermopower was measured for single crystal Bi2-xPbxSr2Co2Oy. There is large in-plane anisotropy, which is attributed to the anisotropic pseudogap formation due to the different crystal symmetry between the square Bi2Sr2O4 layer and the triangular CuO2 layer. The magnitude of the thermopower both along a- and b-axis direction increases with Pb doping from x=0 to 0.4, where we observe discontinuous shrink of b-axis length. We attribute this to the enhancement of the misfitness. Thus, we can improve the thermoelectric properties by tuning the misfitness.