Tunable thermoelectric properties of Ca0.9Yb0.1MnO3 through controlling the particle size via ball mill processing

This paper reports the thermoelectric properties of ytterbium doped calcium manganite with different porosities through controlling the particle size via ball mill processing. It was found that powders without ball milling only yields ~67% of theoretical density after sintering, whereas 10 h milling improves the density to 98%. The enhanced bulk density is due to the reduction of particle size via ball milling. The change in morphology and porosity leads to notable influence on the thermal and electrical transport properties of this material system. The absolute value of Seebeck coefficient decreases with increasing the ball milling time which may be associated with modification of Mn3+/Mn4+ ratio in the system, as evidenced by the results of X-ray photoelectron spectrometry and Raman spectroscopy. A maximum figure of merit (ZT=0.11 at 700 °C) was achieved from the sample that was processed with ball milling of 6 h.