The conversion of heat to electricity by thermoelectric devices may play a key role in the future for energy production and utilization. However, in order to meet that role, more efficient thermoelectric materials are needed that are suitable for high-temperature applications. We show that the material system AgPb(m)SbTe(2+m) may be suitable for this purpose. With m = 10 and 18 and doped appropriately, n-type semiconductors can be produced that exhibit a high thermoelectric figure of merit material ZTmax of approximately 2.2 at 800 kelvin. In the temperature range 600 to 900 kelvin, the AgPb(m)SbTe(2+m) material is expected to outperform all reported bulk thermoelectrics, thereby earmarking it as a material system for potential use in efficient thermoelectric power generation from heat sources.

Energy conversion Energy conversion V 1650Cubic AgPb m SbTe 2+m : Bulk Thermoelectric Materials with High Figure of Merit.-The title materials with m = 10 and 18 are n-type semiconductors exhibiting a high thermoelectric figure of merit of about 2.2 at 800 K. They are expected to outperform all reported bulk thermoelectrics in the temperature range 600-900 K and to find applications in thermoelectric power generation from heat sources, such as vehicle exhaust, coal-burning installations, or electric power utilities. With a hot source of 900 K and a temperature difference of about 500 K, a conversion efficiency of more than 18% may be achieved. -(HSU, K. F.; LOO, S.; GUO, F.; CHEN, W.; DYCK, J. S.; UHER, C.; HOGAN, T.; POLYCHRONIADIS, E. K.; KANATZIDIS*, M. G.;

Barium-filled skutterudites BayCo4Sb12 with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that Ba0.44Co4Sb12 is paramagnetic, which implies that some of the Co atoms in BayCo4Sb12 have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BayCo4Sb12 is significantly depressed as compared to unfilled Co4Sb12. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature reaching a maximum value of 1.1 for Ba0.24Co4Sb12 at 850 K.