Synthesis and thermoelectric properties of In0.2+xCo4Sb12+x composite

In this work we have synthesized In0.2+xCo4Sb12+x samples using a melting–annealing–hot pressing procedure, with the In and Sb contents concomitantly varied. The microstructures and thermoelectric properties have been subsequently studied and correlated. Increasing x value leads to an increase of the electrical conductivity, a decrease of the Seebeck coefficient in magnitude, and non-monotonic changes in the power factor and the lattice thermal conductivity. In particular, we have for the first time observed the InSb/Sb eutectic formation through thermal analysis when x is well above 0.2. The high density of interfaces via the formation of InSb/Sb mixture on the grain boundaries seems to decrease the lattice thermal conductivity and accounts for a dimensionless figure of merit, ZT, of 1.0 in In0.8Co4Sb12.6 at 650 K.