Power generation from n-type NbCo1−xNixSn and p-type NbFe1−xMnxSb ternary half-Heusler compounds: from materials development to module fabrication

Abstract

This study presents the fabrication of a highly reliable and thermally stable thermoelectric module using ternary half-Heusler (HH) compounds. The n-type and p-type legs were synthesized from NbCoSn and NbFeSb based materials, respectively. The thermoelectric properties of the HH compounds were enhanced through alloying with Ni doping in n-type NbCo_1−xNi_xSn and Mn doping in p-type NbFe_1−xMn_xSb. Trace amounts of secondary phases were observed in both compounds using X-ray diffraction analysis. Nevertheless, doping improved the power factor as well as the figure-of-merit (zT) in both cases. The n-type NbCo_0.90Ni_0.10Sn and p-type NbFe_0.96Mn_0.04Sb compounds were chosen as thermoelectric legs based on optimized design for a 2π-module using a 3D finite element analysis and their matching thermal expansion coefficients. The constructed module exhibited a power density of 1.74 W cm⁻² with a conversion efficiency of approximately 1% when connected to the hot and cold sides at temperatures of 873 K and 293 K, respectively. These modules, fabricated from all HH compounds, demonstrated consistent and dependable thermoelectric performance, along with reproducibility, thus indicating their potential for practical applications.