Thermoelectric and Structural Properties of the Chemically Doped Ca$_{3}$Co$_{4}$O$_{9}$ System

The Cu and Y doped thermoelectric oxide system [Ca$_{2}$CoO$_{3}$][CoO$_{2}$]$_{1.61}$, also referred to as Ca$_{3}$Co$_{4}$O$_{9}$, was 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 on Cu doped [Ca$_{2}$Co$_{1-x}$Cu$_{x}$O$_{3}$][CoO$_{2}$]$_{1.61}$ and Y doped [Ca$_{2-x}$Y$_{x}$CoO$_{3}$][CoO$_{2}$]$_{1.61}$. 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. Identification of the locations of the doping 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).