An: In situ eutectic remelting and oxide replacement reaction for superior thermoelectric performance of InSb

In this work, we demonstrate a synergistic approach to improve the thermoelectric performance of the InSb compound by introducing a replacement reaction of InSb and TiO₂ during a hot pressing process. As a consequence of the replacement reaction, Ti_In ⁺ point defects, In₂O₃, stacking faults and InSb-Sb eutectic structures have been introduced into the InSb matrix. Accordingly, the electrical conductivity and the power factor (PF) have been significantly improved due to the electron donating nature of Ti_In ⁺ point defects, and the thermal conductivity has also been greatly reduced owing to the extra phonon scattering by dispersed In₂O₃ nanoparticles and stacking faults. More importantly, the melt of the introduced InSb-Sb eutectic structures plays an important role in filtering the transverse acoustic phonons, causing an abrupt reduction of lattice thermal conductivity at high temperature (753-773 K). Therefore, a relatively high ZT value ∼1.1 at 773 K has been obtained for the 0.1 wt% TiO₂ added InSb sample. Moreover, the Vickers hardness of InSb also increases largely (∼210 Hv) deriving from the strengthening effects by introduced point defects and nanoinclusions, which is tougher than many well established mid-temperature TE materials.