Indexed on: 25 Sep '14Published on: 25 Sep '14Published in: JOM (Warrendale, Pa. : 1989)
Since the nanostructure was introduced to modify thermoelectric properties in 1993, many efforts have been devoted to fabricate nanostructures and investigate the electrical and thermal transports in nanostructured materials. Compared with low-dimensional materials, nanocomposites not only exhibit nanofeatures but also can be fabricated in large quantities and compatible with practical thermoelectric devices in scale and shape. This article reviews the background of nanocomposites, then the Mg2(Si0.4Sn0.6)Bix solid solutions. High-manganese silicides with MnSi (HMS–MnSi), and In4−xGdxSe3 compounds are selected as examples to illustrate the combination effect of nanostructure and dopants on thermoelectric properties. In situ nanostructures successfully formed during the rapid cooling and spark-plasma sintering processing and elementaldoping were achieved via melting processing. Electrical conductivities were enhanced as a result of the increased carrier concentration or carrier mobility by elemental doping. Meanwhile, thermal conductivities decreased as a result of the strong phonon scattering intensified by nanostructures. The ZTs for the specimens with optimal doping ratio were enhanced in these three types of thermoelectric materials.