Hot deformation process enhances the thermoelectric properties of heavy-fermion compound YbAl3

The power factor of the heavy-fermion YbAl₃, a promising thermoelectric material, is approximately three to four times greater than that of the commercial thermoelectric material Bi₂Te₃ at room temperature, which has garnered significant attention. However, its simple cubic structure and the strong correlation between thermal and electrical conductivity complicate the regulation its performance, thereby limiting the optimization and enhancement of its thermoelectric properties. This article present a multi-scale microstructure of YbAl₃ developed through a hot deformation process, which simultaneously optimizes its electronic and phononic transport properties. The study reveals that after hot deformation, the number of grain boundaries, dislocations, and lattice distortions in YbAl₃ increases, effectively scattering electrons and phonons. This results in a significant reduction in electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, while the enhanced energy filtering effect improves the Seebeck coefficient. Following three rounds of hot deformation, the highest thermoelectric figure of merit (ZT) for YbAl₃ reaches 0.43 at 300 K, representing a 43 % increase, which is the best value reported to date. This work demonstrates that the electronic and phononic transport properties of heavy-fermion systems can be simultaneously enhanced through the hot deformation process.