SPECIAL TOPIC — Recent advances in thermoelectric materials and devices
We report the synthesis of Nd-filled and Fe substituted p-type NdxFe3.2Co0.8Sb12 (x=0.5, 0.6, 0.7, 0.8, and 0.9) skutterudites by the solid-state reaction method. The influences of Nd filler on the electrical and thermal transport properties are investigated in a temperature range from room temperature to 850 K. A lowest lattice thermal conductivity of 0.88 W·m-1·K-1 is obtained in Nd0.8Fe3.2Co0.8Sb12 at 673 K, which results from the localized vibration modes of fillers and the increase of grains boundaries. Meanwhile, the maximum power factor is 2.77 mW·m-1·K-2 for the Nd0.9Fe3.2Co0.8Sb12 sample at 668 K. Overall, the highest dimensionless figure of merit zT=0.87 is achieved at 714 K for Nd0.9Fe3.2Co0.8Sb12.
In this work, we report that the thermoelectric properties of Bi0.52Sb1.48Te3 alloy can be enhanced by being composited with MnTe nano particles (NPs) through a combined ball milling and spark plasma sintering (SPS) process. The addition of MnTe into the host can synergistically reduce the lattice thermal conductivity by increasing the interface phonon scattering between Bi0.52Sb1.48Te3 and MnTe NPs, and enhance the electrical transport properties by optimizing the hole concentration through partial Mn2+ acceptor doping on the Bi3+ sites of the host lattice. It is observed that the lattice thermal conductivity decreases with increasing the percentage of MnTe and milling time in a temperature range from 300 K to 500 K, which is consistent with the increasing of interfaces. Meanwhile, the bipolar effect is constrained to high temperatures, which results in the figure of merit zT peak shifting toward higher temperature and broadening the zT curves. The engineering zT is obtained to be 20% higher than that of the pristine sample for the 2-mol% MnTe-added composite at a temperature gradient of 200 K when the cold end temperature is set to be 300 K. This result indicates that the thermoelectric performance of Bi0.52Sb1.48Te3 can be considerably enhanced by being composited with MnTe NPs.