Enhanced Thermoelectric Performance of Cu-Doped SnTe by Reducing the Lattice Thermal Conductivity

SnTe is an environmentally friendly and promising alternative thermoelectric material in contrast to harmful PbTe. However, the long-lasting high lattice thermal conductivity significantly inhibits the further enhancement of the thermoelectric figure of merit ZT. Herein, this study proposed a strategy of solvothermal copper doping to considerably reduce the lattice thermal conductivity by introducing multiscale hierarchical structures. The structural and morphological characterizations indicate that Cu was doped as interstitial atoms and secondary-phase Cu1.80Te. Simultaneously, this study reveals that Cu1.80Te and the SnTe matrix stem from nanoparticles and octahedral structures, respectively. In the sintered bulks, phonon scattering was significantly increased owing to the abundant micro/nanopores, Cu1.80Te nanoprecipitates, grain boundaries of SnTe, and phase boundaries between Cu1.80Te and SnTe. The increased phonon scattering leads to a lattice thermal conductivity of ∼0.36 W m–1 K–1 at 773 K, which is lower than that of pristine SnTe. Benefiting from this substantially decreased thermal conductivity, a ZT value of ∼0.91 was achieved in Sn0.98Cu0.02Te. The enhancement is ∼300% over pristine SnTe. This work provides an effective method to fabricate high-performance energy-effective SnTe-based thermoelectric materials.