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

Cu doped and Y doped [Ca$_{2}$CoO$_{3}$][CoO$_{2}$]$_{1.61}$ (referred to as Ca$_{3}$Co$_{4}$O$_{9})$ were prepared by solid state reaction. Temperature dependent thermoelectric properties, resistivity ($\rho )$, Seeback coefficient (S) and thermal conductivity ($\kappa )$, were measured. As seen before, it is found that doping by Cu and Y significantly enhances the thermoelectric properties. In order to understand the origin of these changes in properties in terms of the atomic structure, synchrotron x-ray diffraction and x-ray absorption spectroscopy were applied to probe the change in the average structure and the location of the dopants. The details of the location and coordination of Co and Y in the host lattice and the effect on the figure of merit are discussed. This work is supported by DOE Grant DE-FG02-07ER46402.