  Whether porosity can effectively improve thermoelectric performance is still
an open question. Herein we report that thermoelectric performance can be
significantly enhanced by creating porosity in n-type
Mg3.225Mn0.025Sb1.5Bi0.49Te0.01, with a ZT of ~0.9 at 323 K and ~1.6 at 723 K,
making the average ZT much higher for better performance. The large improvement
at room temperature is significant considering that such a ZT value is
comparable to the best ZT at this temperature in n-type Bi2Te3. The enhancement
was mainly from the improved electrical mobility and multi-scale phonon
scattering, particularly from the well-dispersed bismuth nano-precipitates in
the porous structure. We further extend this approach to other thermoelectric
materials such as half-Heuslers Nb0.56V0.24Ti0.2FeSb and
Hf0.25Zr0.75NiSn0.99Sb0.01 and Bi0.5Sb1.5Te3 showing similar improvements,
further advancing thermoelectric materials for applications.
