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In this work we have observed a remarkable improvement in the thermoelectric (TE) performance of In6- xSn xSe7 ( ZT = ∼0.28 at x = 0.1, 833 K) compared to that of pristine In6Se7 ( ZT = 0.015 at 640 K). This improvement is mainly attributed to the creation of active donor defects SnIn3+ as Sn(4+) is energetically favorable to In+ sites. Although Sn (2+), which generates a defect SnIn− as an acceptor when it is incorporated into the In3+ sites, has a negative effect on the transport properties, the counter effect from Sn(4+) and Sn(2+) suggests that In6Se7-based alloys are prospectively good thermoelectric candidates if their chemical compositions are well optimized. [ABSTRACT FROM AUTHOR]

We present two series of Cu2Ga4Te7-based compounds with Zn substituting for Cu (Cu-poor) and Ga (Ga-poor), and have observed enhanced thermoelectric performance. Generally, the Seebeck coefficient ( α) and lattice thermal conductivity ( κL) increase and electrical conductivity ( σ) decreases with the Zn content increasing. The variation in electrical properties might be mainly due to the formation of antisite defects ( [ABSTRACT FROM AUTHOR]