Improved thermoelectric transport properties of Cu1.8S with NH4Cl-derived mesoscale-pores and point-defects

Abstract In the present work, we have investigated the effect of NH 4 Cl content ( x ) on the microstructure, phase structure and thermoelectric transport properties of Cu 1.8 S- x NH 4 Cl ( x =0, 1, 5, 10, 15 wt%) bulks fabricated by combining mechanical alloying and spark plasma sintering. The addition of NH 4 Cl introduces lots of mesoscale (0.1–2.0 µm) pores and point-defects such as V S • • , C l S • , C l i ' and H i • , leading to a decreased carrier mobility and an increased carrier concentration, respectively. As a result, the thermal conductivity was effectively reduced from 2.1 to 1.2 W m −1 K −1 as increasing x from 0 to 10 wt% at 673 K. A peak ZT value of 0.3 was achieved at 673 K for x =1 wt% resulted from a low thermal conductivity of 1.6 W m −1 K −1 combining an appropriate power factor of 717 μWm −1 K −2 , which is 15% higher than that (0.26) of pristine Cu 1.8 S. Our result indicates that the introduction of NH 4 Cl in thermoelectric materials is an effective and convenient strategy to improve ZT by decreasing thermal conductivity.