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

In the present work, the thermoelectric properties of potential thermoelectric materials (Bi 1− x In x) 2 Se 2.7 Te 0.3 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 (Bi 0.96 In 0.04) 2 Se 2.7 Te 0.3 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 Bi 2 Se 3 sample at 350 K. The highest ZT value of about 0.285 is achieved for (Bi 0.96 In 0.04) 2 Se 2.7 Te 0.3 at 350 K. [Display omitted] • Indium doped Bi 2 Se 2.7 Te 0.3 belongs to the hexagonal crystal system with the space group R 3 ̅ m. • 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 co-doped crystals. • Electrical resistivity has shown degenerate semiconducting behavior with low activation energy. • The Seebeck coefficient and Hall measurements confirm the unique transition from p-type to n-type nature in the doped samples with carrier concentration of the order 1025 m−3. • A significant reduction in the electrical resistivity was found for the co-doped (Bi 0.96 In 0.04) 2 Se 2.7 Te 0.3 sample, leading to an enhancement of the power factor (PF) and thermoelectric figure of merit (ZT). [ABSTRACT FROM AUTHOR]