Nanostructuring and Thermoelectric Characterization of (GaSb)3(1−x)(Ga2Te3) x

Abstract

GaSb is a promising thermoelectric material that exhibits good electrical properties. However, it has a high lattice thermal conductivity (κlat). Nanostructured bulk materials have been attracting interest because they effectively scatter phonons, significantly reducing κlat. AgPbmSbTem+2 (LAST-m) compounds have recently been reported to have low κlat. These compounds have a NaCl structure, similar to that of binary PbTe, where Ag and Sb occupy the Pb site. In these compounds, two divalent Pb atoms are replaced with a monovalent Ag atom and a trivalent Sb atom to maintain charge compensation. In the present study, we reduced κlat of GaSb by applying the same principle as in LAST-m. Specifically, we substituted Te for Sb and generated vacancies at the Ga site to maintain charge compensation. This produced compounds with chemical compositions of (GaSb)3(1−x)(Ga2Te3)x (x = 0, 0.05, 0.10, and 0.25), where GaSb and Ga2Te3 both have the zincblende crystal structure. We employed two different annealing conditions: annealing at 833 K followed by quenching, and annealing at 833 K followed by cooling to room temperature over 3 days. The former annealed samples with compositions of x = 0.05 and 0.10 had nanoscale Ga-rich precipitates and exhibited a large reduction in κlat.