Toward High Conversion Efficiency of Thermoelectric Modules Through Synergistical Optimization of Layered Materials: Article No. 2210407

Waste-heat electricity generation using high-efficiency solid-state conversion technology can significantly decrease dependence on fossil fuels. In this paper, we report a synergistical optimization of layered half-Heusler (hH) materials and module to improve thermoelectric conversion efficiency. This was realized by manufacturing multiple thermoelectric materials with major compositional variations and temperature-gradient-coupled carrier distribution by one-step spark plasma sintering. This strategy provides a solution to overcome the intrinsic concomitants of the conventional segmented architecture that only considers the matching of the figure of merit (zT) with the temperature gradient. The current design is dedicated to temperature-gradient coupled resistivity and compatibility matching, optimum zT matching, and reducing contact resistance sources. By enhancing the quality factor of the materials by Sb-vapor pressure-induced annealing, a superior zT of 1.47 at 973 K was achieved for (Nb, Hf)FeSb hH alloys. Along with the low-temperature high-zT hH alloys of (Nb, Ta, Ti, V)FeSb, the single stage layered hH modules were developed with efficiencies of ~15.2% and ~13.5% for the single-leg and unicouple thermoelectric modules, respectively, under ..delta..T of 670 K. Therefore, this work has a transformative impact on the design and development of next-generation thermoelectric generators for any thermoelectric materials families.