Enhanced thermoelectric performance via randomly arranged nanopores: Excellent transport properties of YbZn2Sb2 nanoporous materials

Fabricating nanoporous bulk thermoelectric (TE) materials with periodically arranged nanopores is highly challenging and expensive, although TE materials exhibit high power factors (α2σ) and low thermal conductivities (κ). Enhanced TE performance via randomly arranged nanopores is demonstrated with a YbZn2Sb2 nanoporous material (nPM) fabricated by a combination of melt quenching and two stage spark plasma sintering in less than 10 h. Measurement of the electrical conductivity, Hall mobility, Seebeck coefficient, and thermal conductivity show that simultaneously enhancing α2σ and reducing κ can realize in the YbZn2Sb2 nPM with randomly arranged nanopores about 50–200 nm in diameter. Compared with YbZn2Sb2 dense bulk materials (dBM) fabricated by a conventional method taking more than 180 h, α2σ at 300 K increases by 122%, κ at 300 K decreases by 29%, and the maximum ZT value at 775 K reaches 0.67, increasing by 46% for the nPM725 sample. This work shows that a periodic arrangement of nanopores is not essential for the fabrication of attractive TE materials, which offers a wider approach to nanostructure engineering to improve TE performance.