Environmental and economic concerns have significantly spurred the search for novel, high-performance thermoelectric materials for energy conversion in small-scale power generation and refrigeration devices. This quest has been mainly fueled by the introduction of new designs and the synthesis of new materials. In fact, good thermoelectric materials must simultaneously exhibit extreme properties: they must have very low thermal conductivity values and both electrical conductivity and Seebeck coefficient high values as well. Since these transport coefficients are interrelated, the required...