New insight into InSb-based thermoelectric materials: from a divorced eutectic design to a remarkably high thermoelectric performance†
As a promising mid-temperature thermoelectric (TE) material, the main obstacle to a high TE performance of the InSb compound is its high thermal conductivity. In this article, a new strategy of eutectic melting has been employed to improve the TE properties of the compound for the first time. By addition of excess Sb into the InSb matrix, an InSb–Sb eutectic structure has been introduced. When the temperature is above the melting point of the eutectic mixture, the InSb–Sb eutectic melts into a liquid phase which inhibits the propagation of transverse acoustic phonons, and the thermal conductivity is reduced drastically. Therefore, the thermoelectric performance is remarkably enhanced after the melting of the eutectic, and an unprecedented high ZT of 1.28@773 K has been achieved for the InSb1.04 sample, which is almost 3 times higher than that of the eutectic-free InSb matrix. Moreover, the Vickers hardness of the eutectic included InSb compound is higher than those of many well-established mid-temperature TE materials, and no evident hardness degradation can be detected after several melting–solidification cycles of the eutectic.