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 Bi_2-xPb_xSr₂Co₂O_y. 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.