Effect of 3d-transition metal substitution on the thermoelectric properties of the misfit-layered cobalt oxide [Ca/sub 2/CoO/sub 3/]/sub p/CoO/sub 2/

The 3d-transition metal (M) substitution has been performed on the cobalt site in the rock-salt (RS)-type [Ca/sub 2/CoO/sub 3/] subsystem of misfit-layered cobalt oxide [Ca/sub 2/(Co/sub 1-x/M/sub x/)O/sub 3/]pCoO/sub 2/. Except for M = V, Ni and Zn, the solid solution has been prepared up to x /spl sim/ 0.10, when the mixed powders of starting materials were sintered at 1193 K. The Cu-substituted samples exhibit larger thermoelectric power (S) and lower resistivity (/spl rho/) relative to the non-doped one. For example, the sample with x = 0.10 shows S = 160 /spl mu/VK/sup -1/ and /spl rho/ = 9.1 m/spl Omega/cm at 290 K and the resulting thermoelectric power factor reaches S/sup 2///spl rho/ = 2.8 x 10/sup -4/ Wm/sup -1/K/sup -2/, being almost twice larger than that of [Ca/sub 2/CoO/sub 3/]/sub p/CoO/sub 2/.