Nanocomposite Materials for Thermoelectric Energy Conversion: A Brief Survey of Recent Patents

The past few decades have witnessed an increasing demand for renewable energy technology, including that of direct thermal to electrical energy conversion via thermoelectricity. Central to high efficient thermoelectric (TE) energy conversion is a high figure of merit, ZT, of the TE material, which requires high electrical conductivity, high thermopower and low thermal conductivity. For simple bulk materials it is hard to simultaneously satisfy these criteria because these physical quantities are inter-dependent: optimizing one quantity often adversely affects the others. Over the past decade, the pursuit of higher ZT materials has culminated into a new paradigm, namely, nanocomposite thermoelectric materials (NcTMs). A NcTM is typically multi-phased, and the characteristic length scale of at least one constituent is on the order of nanometers. The resulting classical and quantum size effects arising from the nanophase(s) and at the interfaces help decouple the inter-dependence of those TE properties, leading to outstanding TE performance. In this paper, we present a brief survey of relevant patent disclosures for NcTMs, focusing on the preparation methods and the peculiar micromorphologies.