Enhancing the figure of merit in thermoelectric materials by adding silicate aerogel

Abstract

To achieve practical applications of thermoelectric materials in large scale, materials with high thermal conversion efficiency, low cost, and operating at a proper temperature range are required. Owing to the inversely relationship between electrical conductivity (σ) and Seebeck coefficient (S), it is a great challenge to improve high power factor (PF = σS2) of a thermoelectric material. Here, we show that by adding a small amount of silicate aerogel to existing promising materials, including Bi0.5Sb1.5Te3 (p-type), Cu0.01Bi2Te2.7Se0.3 (n-type), and p-type MgAgSb, significantly improves the figure of merit (zT) of the materials. For the BiTe-based materials, the primary gain in zT comes from a significant reduced thermal conductivity, while preserving high PF for the aerogel mixed composites. On the other hand, the enhancement of zT in aerogel-added p-type MgAg0.97Sb0.99 material is not due to the reduction in thermal conductivity but rather an enhancement in PF, which is important for practical applications. Furthermore, the materials we present in this work are bulk polycrystalline samples, which are relatively easy to produce without complicated synthesis processes.