Good thermoelectric materials require a large thermopower (S) for generating largethermal voltage, a low electrical resistivity (ρ) for minimizing Joule heating, and a lowthermal conductivity (κ) for retaining the heat at the junctions to obtain a high figure ofmerit Z = S2/ρκ. The calcium cobaltites Ca3Co4O9+δ show large thermopower and lowthermal conductivity and are considered to be a good candidate material forthermoelectric application in waste heat recovery. The composition of Ca3Co4O9+δ couldbe expressed as [Ca2CoO3][CoO2] b1/b2 with the misfit-layered structure. The misfitlayeredstructure comes from different periodicities along the b axis with b1 referring tothe b-axis length of NaCl type [Ca2CoO3] sublattice and b2 referring to the b-axis lengthof [CoO2] sublattice. Therefore, it can be viewed as being composed of two subsystems,i.e., the distorted NaCl-type [Ca2CoO3] sublattice and the CdI2-type [CoO2] sublatticealternatively stacking along the c axis. This chapter presents the data and discussion forthe thermopower of a series of misfit-layered oxides Ca3Co4O9+δ where either the Co siteis partially substituted by transition metals or the Ca site is partially substituted by rareearth metals.
|Title of host publication||Thermoelectric Power|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||36|
|Publication status||Published - 2011 Dec 1|
All Science Journal Classification (ASJC) codes