Thermoelectric performance of In0.8+yGa0.2Sb (0 ≤ y ≤ 0.06) ternary solid solutions with In excess

Abstract

N-type In0.8+yGa0.2Sb(y = 0, 0.02, 0.04, 0.06) ternary solid solutions were prepared by B2O3 flux method followed by spark plasma sintering (SPS) technique. X-ray diffraction analysis and scanning electron microscopy observations show that all samples are composites containing both major InSb-rich solution phase and minor GaSb-rich solution phase. We found that increasing In excess content markedly increased the Seebeck coefficient while had a weak influence on the electrical conductivity of In0.8Ga0.2Sb. As a result, a maximum power factor of 5.2 mWm−1 K−2 was obtained for y = 0.06 at 680 K, two times that of the y = 0 sample. Ga alloying obviously reduces the lattice thermal conductivity. The lowest lattice thermal conductivity of 1.98 Wm−1 K−1 was obtained in the sample with y = 0 at 776 K. The phonon scattering mechanism was discussed. Due to the highest Seebeck coefficient, the maximum ZT value of 0.9 was obtained at 770 K for y = 0.06, which is one of the best results for (In, Ga)Sb based TE materials, suggesting application perspectives at intermediate temperatures. These results also demonstrate the crucial importance of controlling the In stoichiometry in the (In, Ga)Sb solid solutions to obtain high TE performance.