We report magnetic properties of [Ca2CoO3-δ]0.62CoO2 (Ca349) powders with various average size and the Bi- and Sr-doping effects on thermoelectric properties for the magnetically grain-aligned and densified Ca349 thick films. Magnetic anisotropy at 300 K depended on the initial average size of Ca349 powders and decreased with the decrease in the size. This presumably suggests that distortion of crystal structure was induced by a ball-milling process and led to the change of magnetic anisotropy. On the Bi- and Sr-doping effects, an obvious enhancement of thermoelectric properties did not emerge in the case of the Sr-doping, whereas the enhancement was observed for the Bi-doped Ca349 thick films. However, a drastic decrease of magnetic anisotropy was caused by the Bi-doping. For usage of the p-type layer in multilayered thermoelectric module, tuning of the Bi-doping levels in which both enhancement of thermoelectric properties and a certain level of magnetic anisotropy are achieved is required.

We report thermoelectric (TE) properties of mono-layer thick films of p-type [Ca2CoO3-δ]0.62CoO2 (Ca349) and n-type compounds of Ca0.9La0.1MnO3 (Mn113) and LaNi0.98Mo0.02O3 (Ni113) for the improvement of TE performance in multi-layered TE modules. In the case of magnetically aligned Ca349 film, the improvement of TE properties due to the reduction of resistivity (ρ) was achieved by optimization of hot-pressing temperature and ρ was sensitive to relative density of the Ca349 layer. For the decrease in ρ of the n-type layers, two different approaches, the choice of Ni113 as a n-type compound and usage of fine powders of Mn113, were attempted. Both approaches were effective for reducing ρ even in the sintering at ∼900°C.