Potential thermoelectric materials of indium and tellurium co-doped bismuth selenide single crystals grown by melt growth technique

Abstract

In the present work, the thermoelectric properties of potential thermoelectric materials (Bi1−xInx)2Se2.7Te0.3 grown as high-quality single crystals by the melt growth technique were investigated between 10 and 350 K. Powder X-ray diffraction confirms the hexagonal crystal structure of all studied crystals. The high-resolution X-ray diffraction study reveals the direction of growth, single-crystal quality, dislocation density, and the influence of dopants on the inner plane structure of the crystals. A clean surface with very low angle grain boundaries is observed by the field emission scanning electron microscopy. Energy-dispersive X-ray analysis confirms the elemental composition of the crystals. Electrical resistivity has shown degenerate semiconducting behavior with low activation energy. The Seebeck coefficient confirms p-type for the pristine and n-type conducting behavior for the doped samples, with the correlation to the carrier concentration and carrier mobility in the order of 1025/m3 and 10−4 m2/V s, respectively. Thermal conductivity has shown the dominant behavior of phonon scattering. A significant reduction in the electrical resistivity was found for the co-doped (Bi0.96In0.04)2Se2.7Te0.3 sample, leading to an enhancement of the power factor (PF) and thermoelectric figure of merit (ZT) by a factor of about 8.0 and 4.1, respectively, as compared to the pristine Bi2Se3 sample at 350 K. The highest ZT value of about 0.285 is achieved for (Bi0.96In0.04)2Se2.7Te0.3 at 350 K.