Heavy-Fermion YbAl3 Materials: One-step Synthesis and Enhanced Thermoelectric Performance

Microstructure plays a key role in tuning physical properties of materials. Here YbAl3 materials with high figure of merit ZT of 0.35 at 300 K was directly synthesized with Yb and Al pure powders through one-step spark plasma sintering process in 10 min. The excellent thermoelectric performance is attributed to the simultaneous reduction in the lattice thermal conductivity by 47% and electronic thermal conductivity by 27% at 300 K. The remarkable decrease in the electronic thermal conductivity is ascribed to the enhanced scattering of electrons by nanocrystals with 5-20 nm in diameter, strip-like non-crystal with several nanometers in width and various atomic- scale distortions. The substantial decline in the lattice thermal conductivity originates from the enhanced scattering of phonons due to multi-scale microstructures spanning from nanoscale to mesoscale. This work demonstrates that one-step spark plasma sintering process is an efficient strategy to rapidly synthesize YbAl3 materials with multi-scale microstructures and enhanced thermoelectric performance.