Enhancing the Figure of Merit in Thermoelectric Materials by Adding Silicate Aerogel
The practical applications of thermoelectric materials in large scale require materials with high thermal conversion efficiency, low cost, and operating at a proper temperature range. Due 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 small amount of silicate aerogel to existing promising materials, significantly improves the heat-electricity conversion efficiency with Figure of Merit (zT) enhancement. The materials we present in this work are bulk polycrystalline samples, which are relatively easy to produce without complicated synthesis processes. We have demonstrated using aerogel addition to enhance the zT of the two most commonly n- and p-type thermoelectric materials to record high levels. A record high zT ∼1.45 at 350K for p-type Bi0.5Sb1.5Te3 and zT ∼1.12 at 425 K for n-type Cu0.01Bi2Te2.7Se0.3 were achieved. The primary gain in zT comes from a significant reduced thermal conductivity while preserving high power factor for the aerogel mixed composites. We have also demonstrated the enhancement of the zT in aerogel-added p-type MgAg0.97Sb0.99 material with zT value of 1.69 for 0.3 wt% aerogel content at ∼550 K. The mechanism in the case of MAS is not due to the reduction of thermal conductivity but rather the large enhancement in power factor, which is more important for practical applications. Furthermore, the materials we present in this work are bulk polycrystalline samples, which make them more valuable due to the less complicated synthesis processes. This work was published in the open access journal of Materials Today Physics.
