Role of Chemical Doping in Enhancement of Thermoelectric Properties of Ca$_{3}$Co$_{4}$O$_{9}$

Single-phase [Ca$_{2}$CoO$_{3}$][CoO$_{2}$]$_{1.61}$ (Ca$_{3}$Co$_{4}$O$_{9})$ materials doped by transition metals were prepared by solid state reaction followed by annealing under oxygen. The temperature dependent thermoelectric properties, including resistivity ($\rho$), Seebeck coefficient (S) and thermal conductivity ($\kappa )$, were measured. In order to understand the origin of the changes in ZT with doping, local (XAS) and long range (XRD) structural measurements as a function of doping were conducted. The electronic properties were probed by x-ray spectroscopic methods. Identification of the locations of the dopant sites and the impact on ZT will be discussed. This work is supported by DOE Grant DE-FG02-07ER46402. The Physical Properties Measurements System was acquired under NSF MRI Grant DMR-0923032 (ARRA award).